Improvement of light emission of Mn-doped Zn2SiO4 phosphors with sodium

Mn-doped willemite (Zn2SiO4:Mn) green phosphor were synthesized by sol–gel technology. The effect of the addition of sodium, as in the composition Zn(1.92 – X) NaXMn0.08SiO4, on the emission behavior was studied. FT–IR and EPR results revealed that sodium ion is incorporated into the lattice and results in the formation of isolated Mn2+ and Mn–Mn pairs. The maximum emission intensity of the sample under ultraviolet (UV) excitation occurred at the sodium concentration of x?=?~0.03. The green emission at about 525?nm is assigned to Mn2+–Mn2+ pair centres on nearest neighbour Zn sites. The highest intensity of the green emission for x?=?~0.03 is well close to the highest concentration of the Mn2+–Mn2+ pair. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 2 February 2012 | 11:55 am

Flow-injection chemiluminescence determination of haemoglobin in the blood

In this study, a sensitive and simple flow-injection chemiluminescence (CL) method was developed for the quantitative analysis of haemoglobin. The method is based on the ability of haemoglobin to enhance the CL signal generated by a H2O2–K4Fe(CN)6–fluorescein alkaline system enhanced by CdTe quantum dots. Under the optimized conditions, haemoglobin can be detected in concentration range 7.35?×?10–9–2.5?×?10–6?mol/L, with a detection limit (3?) of 1.8?×?10–9?mol/L and a relative standard deviation (RSD; for 5?×?10–7?mol/L haemoglobin) of 2.06% (n?=?11). The present CL method was successfully applied for the determination of haemoglobin in three kinds of blood samples taken from an infant, an adult man, an adult woman and two reference samples. Compared with previous reports, the CL method described in this work is simple and rapid, with high sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 2 February 2012 | 11:27 am

Determination of arecoline in areca nut based on field amplification in capillary electrophoresis coupled with electrochemiluminescence detection

A sensitive capillary electrophoresis–electrochemiluminescence (CE–ECL) assay with an ionic liquid (IL) was developed for the determination of arecoline in areca nut. The IL, 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4), was an effective additive improved not only the separation selectivity but also the detection sensitivity of the analyte. BMImBF4 in the separation electrolyte made the resistance of the separation buffer much lower than that of the sample solution, which resulted in an enhanced field amplified electrokinetic injection CE. ECL intensity of arecoline is about two times higher than that of the analyte with phosphate–IL buffer system. Resolution between arecoline and other unknown compounds in real samples was improved. Under the optimized conditions (ECL detection at 1.2?V, 16?kV separation voltage, 20?mmol/L phosphate with 10?mmol/L BMImBF4 buffer at pH 7.50, 5?mmol/L Ru(bpy)32+ and 50?mmol/L phosphate buffer in the detection reservoir), a detection limit of 5?×?10–9?mol/L for arecoline was obtained. Relative standard deviations of the ECL intensity and the migration time were 4.51% and 0.72% for arecoline. This method was successfully applied to determination of the amount of arecoline in areca nut within 450?s. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 2 February 2012 | 7:06 am

A ratiometric fluorescent probe for bisulphite anion, employing intramolecular charge transfer

4-(1H-benzimidazol-2-yl)benzaldehyde (1) has been developed as a new ratiometric fluorescent probe for bisulphite, based on the modulation of intramolecular charge transfer (ICT). Upon mixing with bisulphite in aqueous ethanol, an aldehyde–bisulphite adduct was formed and the ICT of the probe was switched off, which resulted in a ratiometric fluorescence response with an enhancement of the ratios of emission intensities at 368 and 498?nm. The detection range of the probe for bisulphite is in the 2.0–200?µmol/L concentration range and the detection limit is 0.4?µmol/L. Probe 1 produces a ratiometric fluorescent response to bisulphite with a marked emission wavelength shift (130?nm) and displays high selectivity for bisulphite over other anions. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 2 February 2012 | 6:26 am

Application of optimized chemiluminescence assay for determination of the antioxidant capacity of herbal extracts

A chemiluminescence (CL) assay for the determination of antioxidant capacity (AOC) has been optimized and applied to analyses of herbal extracts in the present study. The optimal concentrations of reagents (luminol, H2O2, horseradish peroxidase) have been determined, as well as the optimal reaction conditions (wavelength, pH, temperature, sample volume). All of the measurements were performed at the emission maximum of the oxidized form of luminol (425?nm). The optimal concentrations of the reagents were determined as follows: 1.6?mmol/L luminol, 7.5?mmol/L H2O2 and 0.14 U/mL horseradish peroxidase activity in the reaction mixture. Analyses were carried out in phosphate buffer, pH 7.4, at room temperature. With the optimized CL assay, the AOCs of various water and methanol herbal extracts were determined (dog rose hips, plantain leaves and coltsfoot and thyme flowers) and the results were compared to those obtained by other classical methods for the evaluation of antioxidants. Strong correlations (r?>?0.9) with the Folin–Ciocalteau assay and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH)? assay are confirmed, although there is no correlation between AOC and the concentration of ascorbic acid in the samples analysed. This optimized CL assay is simple, rapid and reliable, and it represents a good alternative to classical methods (Folin–Ciocalteau, DPPH?) for the determination of AOC of herbal extracts and other food samples. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 30 January 2012 | 6:07 pm

Spectrofluorimetric determination of aliskiren in dosage forms and urine

A new, simple and sensitive spectrofluorimetric method has been developed for the determination of aliskiren (ALS) in dosage forms and human urine. The method is based on the reaction between ALS and fluorescamine in borate buffer solution, pH 9, to give a highly fluorescent derivative which is measured at 482?nm after excitation at 382?nm. The factors affecting the reaction were carefully studied. The fluorescence intensity concentration plots were rectilinear over the range 140–1400?ng/mL with a limit of detection 13.47?ng/mL and limit of quantitation 40.81?ng/mL. The developed method was successfully applied to the analysis of the drug in tablets and human urine; the average recoveries (n?=?6) were 99.88?±?0.38% and 99.57?±?0.44%, respectively. The “analytical performance of the method was fully validated and the results were satisfactory. The stability of the drug was studied by subjecting it to acidic, basic, oxidative and thermal degradation. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 30 January 2012 | 5:42 pm

Investigation on luminescence properties of Eu2+-doped Ba3Al2O5Cl2 phosphor for near-UV-excited white LEDs

Ba3Al2O5Cl2:Eu2+ phosphor was prepared by combustion synthesis (CS). The prepared phosphor was excited at 329?nm; the phosphors shows an efficient bluish-green wide-band emission centred at 490?nm, which originates from the 4f6d1???4f7 transition of Eu2+ ions. The excitation spectra of the phosphors have a band centred at 329?nm. It was also characterized by XRD, FT–IR for confirmation of phase purity, and FT–IR analysis indicated the vibrations of metal–oxygen (M–O) groups. SEM shows the morphology of the phosphor at the submicron scale. The results indicate that Ba3Al2O5Cl2:Eu2+ phosphor may be applicable for solid-state lighting purposes. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 27 January 2012 | 1:45 pm

Dy3+and Mn2+ emission in fluoride- and chloride-based Na3(SO4)X (X = F or Cl) phosphors

In the present study, Na3(SO4)X (X?=?F or Cl) halosulphate phosphors have been synthesized by the solid-state diffusion method. The phase formation of the compounds Na3(SO4)F and Na3(SO4)Cl were confirmed by X-ray powder diffraction (XRD) measurement. Photoluminescence (PL) excitation spectrum measurement of Na3(SO4)F:Ce3+ and Na3(SO4)Cl:Ce3+ shows this phosphor can be efficiently excited by near-ultraviolet (UV) light and presents a dominant luminescence band centred at 341?nm for Ce3+, which is responsible for energy transfer to Dy3+and Mn2+ ions. The efficient Ce3+???Dy3+ energy transfer in Na3(SO4)F and Na3(SO4)Cl under UV wavelength was observed due to 4?F9/2 to 6H15/2 and 6H13/2 level, while Ce3+???Mn2+ was observed due to 4?T1 state to 6A1. The purpose of the present study is to develop and understanding the photoluminescence properties of Ce3+-, Dy3+- and Mn2+-doped fluoride and chloride Na3(SO4)X (X?=?F or Cl) luminescent material, which can be the efficient phosphors in many applications, such as scintillation applications, TL dosimetry and the lamp industry, etc. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 25 January 2012 | 6:50 am

In Memoriam: Dr. Masako Maeda (1934–2011)

Posted on 25 January 2012 | 6:39 am

Effects of 6?months of endurance training on neutrophil functions to produce reactive oxygen species and mental states in male long-distance runners

To clarify changes of neutrophil functions, mental conditions and relationships among them, 19 male elite long-distance runners participated in this study for 6?months. Examinations, with informed consent, were carried out once a month. According to the results of physical characteristics, it was thought that training intensity was reduced after the main race, Hakone-Ekiden. Neutrophil functions were estimated by indices of reactive oxygen species production, determined by luminol- and lucigenin-dependent chemiluminescence (LmCL and LgCL, respectively) and cytochrome c reduction methods. The peak times (PT) in LmCL and LgCL (LgPT) were most prolonged in January and December, respectively. The peak heights (PH) in LmCL (LmPH) were enhanced in February. Decreased levels of negative categories in the profile of mood state (POMS) questionnaire and the total mood state (TMS) of POMS were observed in February without significance. Correlation analysis using measured values revealed significant negative correlation between LmPH and negative categories in POMS; however, these correlations were possibly a mere appearance, caused by personal differences. After eliminating personal differences, LgPT correlated positively to depression (p?<?0.05), anger (p?<?0.05), fatigue (p?<?0.01) and TMS (p?<?0.05). These results suggest that the mean time from the recognition of foreign matter to the maximum production of superoxide from neutrophils is prolonged in the mentally suppressed conditions found under continuous physical training. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 18 January 2012 | 4:57 pm

High-throughput method for the analysis of venlafaxine in pharmaceutical formulations and biological fluids, using a tris(2,2?-bipyridyl) ruthenium(II)–peroxydisulphate chemiluminescence system in a two-chip device

A simple, rapid and sensitive chemiluminescent (CL) method for the assay of venlafaxine (VEN) in pharmaceutical formulations and serum samples by a two-chip device is proposed. The method is based on the reaction of this drug with a tris(2,2?-bipyridyl) ruthenium(II)–peroxydisulphate CL system. The optimum chemical conditions for CL emission were investigated. The calibration graph was linear for the concentration range 0.02–8.0?µg/mL. The detection and quantification limits were found to be 0.006 and 0.018?µg/mL, respectively, while the relative standard deviation (RSD) was <2.0%. The present CL procedure was applied to the determination of VEN in pharmaceutical formulations and serum samples; the recovery levels were in the range 96.5–101.2%. The results suggest that the method is unaffected by the presence of common formulation excipients found in these samples. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 18 January 2012 | 2:03 pm

Terbium-sensitized fluorescence method for the determination of dopamine in biological fluids and tablet formulation

A novel, rapid, simple and sensitive method for dopamine analysis in solutions was developed. The method is based on excitation of terbium–dopamine complex at 318?nm and emission intensity at 545?nm. The optimum conditions found were: pH 8.5; reaction time 70–150?min; temperature 0°C; buffer (Tris 0.1?mol/L) volume 1?ml; terbium concentration 10–5?mol/L; antioxidant Na2SO3, 0.02?mol/L; and Brij 35 0.002?mol/L. To avoid a matrix effect of urine, serum and saliva, the samples should be diluted e.g., 1000-fold for urine and 100-fold for serum. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 12 January 2012 | 10:02 am

Scavenging of hydroxyl radical by catecholamines

The direct effects of the four catecholamines (CATs), adrenaline (A), noradrenaline (NA), dopamine (D) and isoproterenol (I), on free radicals were investigated using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and hydroxyl radial (HO•). The CATs examined were found to inhibit the ESR signal intensity of DPPH• in a dose-dependent manner over the range 0.1–2.5?mmol/L in the following order: NA?>?A?>?I?>?D, with IC50?=?0.30 ± 0.03 for noradrenaline and IC50?=?0.86 ± 0.02 for dopamine. Hydroxyl radicals were produced using a Fenton reaction in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and ESR technique was applied to detect the CATs reactivity toward the radicals. The reaction rates constant (kr) of CATs with HO• were found to be in the order of 109?L/mol/s, and the kr value for noradrenaline was the highest (kr?=?8.4 × 109?L/mol/s). The CATs examined exhibited also a strong decrease in the light emission (62–73% at 1?mmol/L concentration and 79–89% at 2?mmol/L concentration) from a Fenton-like reaction. These reactions may be relevant to the biological action of these important polyphenolic compounds. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 12 January 2012 | 9:06 am

Investigation on the chemiluminescence reaction of the phenylhydrazine-luminol–peroxide system

We studied the chemiluminescence (CL) oxidation of phenyl hydrazine–luminol with various organic and inorganic peroxides. Maximum CL intensity for this system was obtained for t-butylhydroperoxide. The enhancement in CL depended strongly on pH and was greatest at pH 12.5. The solvent drastically enhanced the CL intensity. DMSO was found to increase the CL intensity many-fold as compared to acetonitrile and water. The effect of temperature on CL intensity has also been studied. The CL spectra revealed a broad peak at 425?nm, which suggests excited 3-aminophthalate ion as the luminophor. A mechanism to explain the reactions is suggested. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 12 January 2012 | 9:05 am

Synthesis and characterizations of iso-luminol-functionalized, tadpole-shaped, gold nanomaterials

Iso-luminol functionalized gold nanomaterials were synthesized in high yield by a simple seeding approach, using the chemiluminescent reagent iso-luminol as reductant in the presence of HAuCl4, AgNO3 and cetyltrimethylammonium bromide (CTAB). The morphology of as-prepared gold nanoparticles was characterized by transmission electron microscopy and UV–vis spectroscopy, showing that gold nanotadpoles (AuNTps) were obtained. Subsequent experiments revealed that the amounts of seed colloids and AgNO3 and the concentrations of iso-luminol and CTAB in the growth solution play critical roles in the formation of well-shaped AuNTps. The surface state of AuNTps was characterized by UV–vis spectroscopy and fluorescence spectroscopy, indicating that iso-luminol and its oxidation product, 4-aminophthalate, coexisted on the surface of AuNTps. The CL behaviour was studied by static injection CL experiments, demonstrating that AuNTps were of CL activity. Finally, the growth mechanism of AuNTps was also discussed. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 4 January 2012 | 5:39 pm

Solvent effects of N-nitroso, N-(2-chloroethyl), N?,N?-dibenzylsulfamid and its copper(II) and cobalt(II) complexes: fluorescence studies

The structure of N-nitroso, N-(2-chloroethyl), N?,N?-dibenzylsulfamid (CENS) was established by X-ray crystallography. The atomic coordinates, factors of isotropic thermal agitation, bond lengths and valence angles were determined. The solvent effects on the electronic absorption and fluorescence spectra of CENS were investigated at room temperature. The effects of solvent polarity and of hydrogen bonding were interpreted by means of linear solvation energy relationships (LSERs). Multiple linear regression analysis indicated that the hydrogen donation properties of the solvent play an important role in determining the position of the absorption maximum, while the classical polarity of the medium is the only dominating parameter in determining the emission maximum and the Stokes' shift. Complexation of the investigated compound by two different transition metal ions was studied. Fluorescence measurements show that fluorescence quenching by cobalt(II) is more important than that by copper(II). This phenomenon can be attributed to good stereo-structural matching between the electronic configuration of the Co2+ ion and the active site distribution of CENS in aqueous solution. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 4 January 2012 | 5:34 pm

Synthesis and luminescence properties of lanthanide complexes with a new tripodal ligand featuring N-thenylsalicylamide arms

To explore the relationship between the structure of the ligands and the luminescent properties of the lanthanide complexes, luminescent lanthanide complexes of a new tripodal ligand, featuring N-thenylsalicylamide arms, were synthesized and characterized by elemental analysis, IR and TGA measurements. Photophysical properties of the complexes were studied by means of UV???visible absorption and steady-state luminescence spectroscopy. The results of UV???vis spectra indicate that metal binding does not disturb the electronic structure of the ligand. Excited-state luminescence lifetimes and quantum yields of the complexes were determined. The photoluminescence analysis suggested that there is an efficient ligand???Ln(III) energy transfer for the Tb(III) complex, and the ligand is an efficient 'antenna' for Tb(III). From a more general perspective, the results demonstrated the potential application of the lanthanide complex as luminescent materials in material chemistry. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 4 January 2012 | 5:34 pm

Chemiluminescence behaviour of CdTe–potassium permanganate enhanced by sodium hexametaphosphate and sensitized sensing of l-ascorbic acid

A highly sensitive flow-injection chemiluminescence (FIA-CL) method based on the CdTe nanocrystals and potassium permanganate chemiluminescence system was developed for the determination of l-ascorbic acid. It was found that sodium hexametaphosphate (SP), as an enhancer, could increase the chemiluminescence (CL) emission from the redox reaction of CdTe quantum dots with potassium permanganate in near-neutral pH conditions. l-Ascorbic acid is suggested as a sensitive enhancer for use in the above energy-transfer excitation process. Under optimal conditions, the calibration graph of emission intensity against logarithmic l-ascorbic acid concentration was linear in the range 1.0?×?10?9–5.0?×?10?6?mol/L, with a correlation coefficient of 0.9969 and relative standard deviation (RSD) of 2.3% (n?=?7) at 5.0?×?10?7?mol/L. The method was successfully used to determine l-ascorbic acid in vitamin C tablets. The possible mechanism of the chemiluminescence in the system is also discussed. Copyright © 2012 John Wiley & Sons, Ltd.

Posted on 4 January 2012 | 5:27 pm

Flow injection–chemiluminescence determination of acyclovir

The chemiluminescence (CL) reaction of acyclovir (ACV)–potassium permanganate, with formaldehyde as an enhancer, was investigated by the flow-injection system, and a new method is reported for the determination of ACV on the basis of the reaction. The method is rapid, effective and simple for the determination of acyclovir in the range 0.2–80?mg/L, with a limit of detection of 0.06?mg/L (3 S:N), a relative standard deviation (RSD) of 3.7% for the determination of 1.0?mg/L acyclovir solution in 11 repeated measurements. The method has been applied to the determination of acyclovir in pharmaceuticals, with satisfactory results. The possible reaction mechanism is also discussed briefly. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 30 December 2011 | 3:31 pm

The UK Glow Worm Survey and the Glow Worm Distribution Map

Posted on 28 December 2011 | 5:47 am

Optical studies of CdS:Mn nanoparticles

Cadmium sulphide nanoparticles were grown using a wet chemical method, by dissolving the reactants, cadmium chloride and sodium sulphide in water, in the presence of mercaptoethanol (ME), which was used as a capping agent. Manganese chloride was used to dope the nanoparticles. It was found that the particle size varied with different concentrations of ME. At higher concentrations of ME, smaller sized nanoparticles were synthesized. This method also reveals the high stability of nanoparticles in water. Nanoparticle properties were investigated using UV–vis absorption, photoluminescence spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The particle sizes were measured by the XRD technique, SEM and optical absorption spectra and were in the range 2–6?nm. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 28 December 2011 | 4:18 am

Development of a compact capillary electrophoresis–chemiluminescence system with ultra-fast peroxyoxalate reaction to monitor the hydrolysis of rhodamine 6G

A simple and effective capillary electrophoresis–chemiluminescence (CE–CL) detection system was developed based on an ultra-fast bis(2,4,6-trichlorophenyl)oxalate (TCPO) chemiluminescence (CL) reaction (0.6 s duration) that avoided overlapping peaks and peak tailing. Through a series of static injection experiments, this unusually rapid CL reaction was ascribed to the catalytic effect of imidazole in the tetrahydrofuran solvent, which has been rarely utilized in such investigations. A possible mechanism is given to explain the results. Under the optimized conditions, rhodamine 6?G (R6G) and its hydrolysis product (R6G-COOH) could be efficiently separated through electrophoresis in 7?min, with sensitive CL detection in the proposed CE–CL system. In this way, the alkaline hydrolysis of R6G was monitored, followed by estimation of relative rate constants and activation energy. This finding and application should be helpful in further study for the TCPO CL reaction, and revealed an attractive opportunity for simplifying the CE–CL system, such as in a microchip device. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 28 December 2011 | 4:18 am

Effects of imidazolium room temperature ionic liquids on the fluorescent properties of norfloxacin

The effects of 12 imidazolium room temperature ionic liquids (RTILs), including [Cnmim]BF4, [Cnmim]PF6, and [Cnmim]Br (n?=?4, 6, 8, 10), on the fluorescent properties of norfloxacin were examined. The fluorescence intensity of norfloxacin at 0.1?mg/L in methanol significantly increased with the addition of [Cnmim]BF4 and [Cnmim]PF6 into the solvent at 0.1–15.0%. The sensitizing effect may result from the higher viscosity of the RTILs–methanol mixture solvent than that of the methanol itself. However, the quenching effect on fluorescence of norfloxacin was observed in [Cnmim]Br–methanol solvent. The fluorescence intensities of norfloxacin decreased with an increase in the alkyl chain length of the alkyl substituents of the imidazolium ring of RTILs. The main interaction between the RTILs and norfloxacin is not by hydrogen bonding. The fact, that some RTILs can significantly sensitize fluorescence of norfloxacin, indicates that RTILs could be a group of promising solvents for development of sensitive spectrofluorimetric methods for determination of norfloxacin at ultra-trace levels in environmental samples. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 28 December 2011 | 4:17 am

Supramolecular aggregation/disaggregation-based molecular sensing: a review focused on investigations from China

Supramolecular aggregation and disaggregation induced by external stimuli can impact the optical or electrical signals of the aggregates/constituting units (receptors). Therefore, manipulating supramolecular aggregation/disaggregation has recently been employed to construct novel and promising photoluminescence (PL)-based sensing and recognition systems. The sensing systems were capable of substantially enhancing the sensitivity, relying on cooperative interactions occurring in the assembly/disassembly processes (mostly operating in emission turned-on or emission-enhanced mode). This review focuses mainly on recent advances in the new emerging PL-based sensing platforms, based on manipulating the behaviours of supramolecular aggregation/disaggregation, including aggregation-induced emission (AIE), metallophilic interactions-related sensing (metallophilic interactions-induced aggregation/disaggregation), metal coordination polymers-related sensing, and other sensing systems involving supramolecular aggregation/disaggregation. In particular, those sensing systems developed by scientists in China are summarized and highlighted. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 12 December 2011 | 10:42 am

Combustion synthesis of blue-emitting submicron CaAl4O7:Eu2+, Dy3+ persistence phosphor

Long persistence phosphor CaAl4O7: Eu2+, Dy3+ were prepared by a combustion method. The phosphors were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), decay time measurement techniques and photoluminescence spectra (PL). The CaAl4O7: Eu2+, Dy3+ phosphor showed a broad blue emission, peaking at 445?nm when excited at 341?nm. Such a blue emission can be attributed to the intrinsic 4f???5d transitions of Eu2+ in the host lattices. The lifetime decay curve of the Dy3+ co-doped CaAl4O7: Eu2+ phosphor contains a fast decay component and another slow decay one. Surface morphology also has been studied by SEM. The calculated CIE colour chromaticity coordinates was (0.227, 043). We have also discussed a possible long-persistent mechanism of CaAl4O7:Eu2+, Dy3+ phosphor. All the results indicate that this phosphor has promising potential for practical applications in the field of long-lasting phosphors for the purposes of sign boards and defence. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 12 December 2011 | 10:42 am

Fluorescence enhancement of rare earth Tb(III) by Tm(III) in benzyl benzoylmethyl sulphoxide complexes

A series of rare earth complexes [(TbxTmy)L5(ClO4)2](ClO4)·3H2O (x:y?=?1.000:0.000, 0.999:0.001, 0.995:0.005, 0.990:0.010, 0.950:0.050, 0.900:0.100, 0.800:0.200, 0.700:0.300; L?=?C6H5CH2SOCH2COC6H5) (Tb(III) luminescence ion; Tm(III) doped inert ion) were synthesized and characterized by elemental analysis, infrared spectra (IR) and 1H-NMR. The photophysical properties of these complexes were studied in detail using ultraviolet absorption spectra, fluorescent spectra and lifetimes. The fluorescence spectra of complexes indicated that the fluorescence emission intensity was significantly enhanced by Tm(III). The complexes showed the best luminescence properties when the mole ratio Tb(III):Tm(III) was 0.990:0.010. The fluorescence intensity could be increased to 390%. Additionally, phosphorescence spectra and the luminescence mechanisms are discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 23 November 2011 | 2:38 pm

Effects of homogeneous media, binary mixtures and microheterogeneous media on the fluorescence and fluorescence probe properties of some benzo[b][1,8]naphthyridiens with HSA and BSA

A rapid and efficient method for the synthesis of various poly-substituted benzo[b][1,8]naphthyridines in high yield has been developed via the Friedländer condensation of 2-aminoquinoline-3-carbaldehyde 1 with various alicyclic ketones in a base catalyst (aq. potassium hydroxide). A series of benzo[b][1,8]naphthyridines branched with various side-chains and substituents were prepared with the aim of being investigated as a fluorescent agents. Electronic absorption and fluorescence properties of some representative benzonaphthyridines (3d, 5b and 21f) in homogeneous organic solvents, dioxane–water binary mixtures and in the microheterogeneous media (sodium dodecyl sulphate (SDS), cetyl trimethyl ammonium bromide (CTAB) and Triton-X100 micelles) have been examined. A linear correlation between solvent polarity and fluorescence properties was observed. Further, the interaction of these benzonaphthyridines (3d, 5b and 21f) with human serum albumin (HSA) and bovine serum albumin (BSA) in phosphate buffer have been examined by UV-vis absorption and fluorescence spectroscopy. The fluorescence intensity of 3d, 5b and 21f increases with the increasing HSA and BSA concentration. These benzonaphthyridines also quench the 345?nm fluorescence of BSA in phosphate buffer (?ex 280?nm). These compounds have potential for use as neutral and hydrophobic fluorescence probes for examining the microenvironments in proteins, polymers, micelles, etc. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 18 November 2011 | 3:05 pm

Sol–gel synthesis, characterization and luminescence properties of SrMgAl2SiO7:Eu2+ as a novel nanocrystalline phosphor

In this research, a new SrMgAl2SiO7:Eu2+ phosphor was synthesized via the sol–gel method. The phase-forming processes were studied by thermogravimetric–differential thermal analysis and X-ray diffraction technique. Scanning electron microscopy showed that there is uniform morphology and microstructure owing to the sol–gel route. Spectrophotometry and colorimetry analyses illustrated that, under short ultraviolet excitation, the main emission peak occurred at 421?nm and also a relatively pure blue color was observed that was ascribed to the 4f65d1(2D) ? 4f7(8S7/2) transition of Eu2+ with color coordination of x = 0.187, y = 0.077. Finally, it was found that the color and phase purity of the synthesized powder increased as calcinations time increased. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Mechanoluminescence properties of gamma-ray-irradiated BaSO4:Eu phosphors

BaSO4 activated with various concentrations of Eu were prepared by solid-state reaction technique. Thermoluminescence (TL) and mecanoluminescence (ML) of ?-ray-irradiated BaSO4:Eu2O3 phosphors were recorded. In the TL glow curve of the phosphor a single peak at 170°C was observed. The TL of the phosphors were also recorded after deforming the phosphors by dropping a piston of mass 0.4?kg onto them with different impact velocities. TL intensity (after deformation) decreased with increasing the impact velocity. In the ML intensity vs time curve two peaks were observed. ML intensity increased with increasing impact velocity of the piston and the time corresponding to peak ML intensity shifted to a shorter time value. ML intensity decreased drastically when it was recorded after annealing the sample at 170°C. The BaSO4 phosphors activated with 0.1?mol% of Eu2O3 showed optimum TL and ML. The photoluminescence emission spectrum of the sample showed that Eu enters as Eu2+ ion in host lattice. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Flow injection chemiluminescence determination of vitamin B12 using on-line UV-persulfate photooxidation and charge coupled device detection

A sensitive chemiluminescence method for vitamin B12 using a charge-coupled device (CCD) photodetector combined with on-line UV-persulfate oxidation in a simple continuous flow system has been developed. The principle for the determination of vitamin B12 is based on the enhancive effect of cobalt (II) on the chemiluminescence reaction between luminol and percarbonate in alkaline medium. In addition, percarbonate has been investigated and proposed as a powerful source of hydrogen peroxide as oxidant agent in this chemiluminescence reaction. The digestion of vitamin B12 to release the cobalt (II) is reached by UV irradiation treatment in a persulfate medium. The CCD detector, directly connected to the flow cell, is used with the continuous flow manifold to obtain the full spectral characteristics of cobalt (II) catalyzed luminol–percarbonate reaction. The vitamin B12 oxidation process and chemical conditions for the chemiluminescence reaction were investigated and optimized. The increment of the emission intensity was proportional to the concentration of vitamin B12, giving a second-order calibration graph over the cobalt (II) concentration range from 10 to 5000??g L?1 (r2?=?0.9985) with a detection limit of 9.3??g L?1. The proposed method was applied to the determination of vitamin B12 in different kinds of pharmaceuticals. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Stability-indicating micelle-enhanced spectrofluorimetric method for determination of loratadine and desloratadine in dosage forms

A highly sensitive and simple spectrofluorimetric method was developed for the determination of loratadine (LRT) and desloratadine (DSL) in their pharmaceutical formulations. The proposed method is based on investigation of the fluorescence spectral behaviour of LRT and DSL in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution of acetate buffer of pH 4.5, the fluorescence intensities of both LRT and DSL were greatly enhanced (240%) in the presence of SDS. The fluorescence intensity was measured at 438?nm after excitation at 290?nm for both drugs. The fluorescence–concentration plots were rectilinear over the range 0.05–2.0?µg/mL for both LRT and DSL, with lower detection limits of 5.13?×?10?3 and 6.35?×?10?3 µg/mL for LRT and DSL, respectively. The method was successfully applied to the analysis of the two drugs in their commercial tablets, capsules and syrups, and the results were in good agreement with those obtained with the official or comparison methods. The proposed method is specific for the determination of LRT in the presence of other co-formulated drugs, such as pseudoephedrine. The application of the proposed method was extended to stability studies of LRT and DSL after exposure to different forced degradation conditions, such as acidic, alkaline and oxidative conditions, according to ICH guidelines. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Metabolic self-organization of bioluminescent Escherichia coli

A possible reason for the complexity of the signals produced by bioluminescent biosensors might be self-organization of the cells. In order to verify this possibility, bioluminescence images of cultures of lux gene reporter Escherichia coli were recorded for several hours after being placed into 8–10?mm diameter cylindrical containers. It was found that luminous cells distribute near the three-phase contact line, forming irregular azimuthal waves. As we show, space–time plots of quasi-one-dimensional bioluminescence measured along the contact line can be simulated by reaction–diffusion–chemotaxis equations, in which the reaction term for the cells is a logistic (autocatalytic) growth function. It was found that the growth rate of the luminous cells (~0.02?s?1) is >100 times higher than the growth rate of E. coli. We provide an explanation for this result by assuming that E. coli exhibits considerable respiratory flexibility (the ability of oxygen-induced switching from one metabolic pathway to another). According to the simple two-state model presented here, the number of oxic (luminous) cells grows at the expense of anoxic (dark) cells, whereas the total number of (oxic and anoxic) cells remains unchanged. It is conjectured that the corresponding reaction–diffusion–chemotaxis model for bioluminescence pattern formation can be considered as a model for the energy-taxis and metabolic self-organization in the population of the metabolically flexible bacteria under hypoxic conditions. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Flow-injection chemiluminescence method for the determination of chloramphenicol based on luminol–sodium periodate order-transform second-chemiluminescence reaction

A new chemiluminescence (CL) reaction was observed when chloramphenicol solution was injected into the mixture after the end of the reaction of alkaline luminol and sodium periodate or sodium periodate was injected into the reaction mixture of chloramphenicol and alkaline luminol. This reaction is described as an order-transform second-chemiluminescence (OTSCL) reaction. The OTSCL method combined with a flow-injection technique was applied to the determination of chloramphenicol. The optimum conditions for the order-transform second-chemiluminescence emission were investigated. A mechanism for OTSCL has been proposed on the basis of the chemiluminescence kinetic characteristics, the UV-visible spectra and the chemiluminescent spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of chloramphenicol over the range 5.0?×?10?7–5.0?×?10?5 mol/L with a correlation coefficient of 0.9969 and a detection limit of 6.0?×?10?8 mol/L (3?). The relative standard deviation (RSD) for 11 repeated determinations of 5.0?×?10?6 mol/L chloramphenicol is 1.7%. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A new and sensitive catalytic resonance scattering spectral assay for the detection of laccase using guaiacol as substrate

In pH 4.0 succinic acid–sodium hydroxide buffer solution, laccase catalyzed the oxidization of guaiacol substrate to form red particles, which exhibited a strong resonance scattering (RS) peak at 590?nm. Under the chosen conditions, as the laccase increased, the RS intensity (?I) increased linearly. The ?I was proportional to laccase activity in the range of 0.10–1.2?U/mL, with a regression equation of ?I = 734.0?Ulaccase ? 9.7, and a detection limit of 0.05?U/mL. This RS method was applied to the detection of laccase activity in real samples, and the results were agreement with those from spectrophotometry. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Novel blue-emitting SrMg2Al16O27:Eu2+ phosphor for solid-state lighting

Eu2+-activated SrMg2Al16O27 novel phosphor was synthesized by a combustion method (550°C furnace). The prepared phosphor was first characterized by X-ray diffraction (XRD) for confirmation of phase purity. SEM analysis showed the morphology of the phosphor. The photoluminescence characteristics showed broad-band excitation at 324?nm, which was monitored at 465?nm emission wavelength. The SrMg2Al16O27:Eu2+ phosphor shows broad blue emission centred at 465?nm, emitting a blue light corresponding to 4f65d1???4f7 transition. Here we report the photoluminescence characteristics of the prepared phosphor and compare it with commercial BAM:Eu2+ phosphor. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Sodium azide as a specific quencher of singlet oxygen during chemiluminescent detection by luminol and Cypridina luciferin analogues

Reactive oxygen species (ROS) are presently thought to play important role in an increasing number of the physiological and pathological processes in living organisms. Various chemiluminescent (CL) compounds have been studied in order to find suitable and specific probes for the detection of particular ROS species. The CL of luminol is known to be non-specific and can be induced by various oxidants. Two Cypridina luciferin analogues, CLA and MCLA, have been used for the detection of ROS in vivo. CLAs are thought to emit light only when reacting with superoxide and singlet oxygen. It is possible to distinguish the particular ROS by using a specific quencher or scavenger, e.g. superoxide dismutase (SOD) or sodium azide (NaN3). The CL reactions of luminol (3-aminophthalhydrazide), CLA [2-methyl-6-phenyl-3,7-dihydroimidazo(1,2?) pyrazin-3-one] and MCLA [2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo(1,2?) pyrazin-3-one] were studied in three hydrogen peroxide decomposition systems (H2O2–HRP; H2O2–CuSO4; and H2O2–NaOCl). The measurements were carried out in phosphate buffer, pH 7.4, at 25?°C, using a luminometer (Fluoroskan Ascent FL and Sirius C). NaN3 was used as the specific quencher of singlet oxygen. The results demonstrate that the proclaimed specifity of the CL of Cypridina luciferin analogues towards singlet oxygen has to be discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Study of the interaction between ofloxacin and human serum albumin by spectroscopic methods

The binding of ofloxacin (OFLX) to human serum albumin (HSA) was investigated by fluorescence and circular dichroism (CD) techniques. The binding parameters have been evaluated by a fluorescence quenching method. Competitive binding measurements were performed in the presence of warfarin and ibuprofen and suggest binding to the warfarin site I of HSA. The distance r between donor (HSA) and acceptor (OFLX) was estimated according to the Forster's theory of non-radiatiative energy transfer. CD spectra revealed that the binding of OFLX to HSA induced conformational changes in HSA. Molecular docking was performed and shows that for the lowest energy complex OFLX is located in site I of HSA, which correlate to the competitive binding experiments. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Luminol–silver nitrate chemiluminescence enhancement induced by cobalt ferrite nanoparticles

CoFe2O4 nanoparticles (NPs) could stimulate the weak chemiluminescence (CL) system of luminol and AgNO3, resulting in a strong CL emission. The UV–visible spectra, X-ray photoelectron spectra and TEM images of the investigated system revealed that AgNO3 was reduced by luminol to Ag in the presence of CoFe2O4 NPs and the formed Ag covered the surface of CoFe2O4 NPs, resulting in CoFe2O4–Ag core–shell nanoparticles. Investigation of the CL reaction kinetics demonstrated that the reaction among luminol, AgNO3 and CoFe2O4 NPs was fast at the beginning and slowed down later. The CL spectra of the luminol???AgNO3???CoFe2O4 NPs system indicated that the luminophor was still an electronically excited 3-aminophthalate anion. A CL mechanism has been postulated. When the CoFe2O4 NPs were injected into the mixture of luminol and AgNO3, they catalyzed the reduction of AgNO3 by luminol to produce luminol radicals and Ag, which immediately covered the CoFe2O4 NPs to form CoFe2O4–Ag core–shell nanoparticles, and the luminol radicals reacted with the dissolved oxygen, leading to a strong CL emission. With the continuous deposition of Ag on the surface of CoFe2O4 NPs, the catalytic activity of the core–shell nanoparticles was inhibited and a decrease in CL intensity was observed and also a slow growth of shell on the nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A novel spectrofluorimetric method for the assay of pseudoephedrine hydrochloride in pharmaceutical formulations via derivatization with 4-chloro-7-nitrobenzofurazan

A new highly sensitive and specific spectrofluorimetric method has been developed to determine a sympathomimetic drug pseudoephedrine hydrochloride. The present method was based on derivatization with 4-chloro-7-nitrobenzofurazan in phosphate buffer at pH 7.8 to produce a highly fluorescent product which was measured at 532?nm (excitation at 475?nm). Under the optimized conditions a linear relationship and good correlation was found between the fluorescence intensity and pseudoephedrine hydrochloride concentration in the range of 0.5–5?µg?mL?1. The proposed method was successfully applied to the assay of pseudoephedrine hydrochloride in commercial pharmaceutical formulations with good accuracy and precision and without interferences from common additives. Statistical comparison of the results with a well-established method showed excellent agreement and proved that there was no significant difference in the accuracy and precision. The stoichiometry of the reaction was determined and the reaction pathway was postulated. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A highly selective fluorescent sensor for mercury ion (II) based on azathia-crown ether possessing a dansyl moiety

An intramolecular charge transfer (ICT) fluorescent sensor 1 using a dansyl moiety as the fluorophore and an azathia-crown ether as the receptor was designed, synthesized and characterized. The ions-selective signaling behaviors of the sensor 1 were investigated in CH3CN-H2O (1:1, v/v) by fluorescence spectroscopy. It exhibited remarkable fluorescence quenching upon addition of Hg2+, which was attributed to the 1:1 complex formation between 1 and Hg2+, while other selected metal ions induced basically no spectral changes. The sensor 1 showed a rapid and linear response towards Hg2+ in the concentration range from 5.0 × 10?7 to 1.0 × 10?5?mol?L?1 with the detection limit of 1.0 × 10?7?mol?L?1. Furthermore, the whole process could be carried out in a wide pH range of 2.0–8.0 and was not disturbed by other metal ions. Thus, the sensor 1 was used for practical determination of Hg2+ in different water samples with satisfactory results. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Gold nanoparticles-based fluorescence enhancement of the terbium–levofloxacin system and its application in pharmaceutical preparations

A sensitive fluorescence (FL) technique is proposed for the determination of levofloxacin (LVX). The method is based on the fact that the weak FL signal of the Tb(III)–LVX system is strongly enhanced in the presence of gold nanoparticles. Gold nanoparticles were prepared by the citrate reduction of HAuCl4 and characterized by transmission electron microscopy (TEM). Levofloxacin and Tb(III) ion form a fluorescence complex in aqueous solution, and its maximum emission wavelength was found at 545?nm. Optimal conditions for the formation of the levofloxacin–Tb(III) complexes were studied. Levofloxacin was detected by measuring the FL intensity, which increases linearly with the concentration of LVX in the range 6.2?×?10?10–2.6?×?10?8 mol/L. Recovery of the target analytes was?>?96% with good quality parameters: linearity (r2?>?0.996), limit of detection (LOD) and limit of quantification (LOQ) values 2.1?×?10?10 mol/L and 7.2?×?10?10 mol/L, and run-to-run and day-to-day precisions with relative standard deviations (RSDs) around 3%. Thus, the proposed method can be successfully applied to the routine determination of levofloxacin in pharmaceutical preparations. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A sensitive method for determination of trace amounts of chromate (III) with terbium (III) sodium hexametaphosphate chelate as fluorescent probe

Based on the fluorescence quenching of Terbium (III)-sodium hexametaphosphate (Tb/SHMP) chelates in the presence chromate (III), a sensitive fluorimetric method was developed for the determination of trace amounts of chromium (III) in aqueous solutions. Under the optimum conditions, the linear calibration graph was obtained (R = 0.996). The linear range and detection limit of Cr (III) were 7.69 × 10?7 to 1.15 × 10?4?mol?L?1 and 4.50 × 10?7?mol?L?1, respectively. The proposed method had a wider linear range and was proved to be very sensitive, rapid and simple. The method was applied successfully to the determination of chromium (III) in the synthetic samples and real water samples. Moreover, the reaction mechanism was discussed through the fluorescence lifetime and proved to be dynamic quenching behavior. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Analysis of fexofenadine in pharmaceutical formulations using tris(1,10-phenanthroline)–ruthenium(II) peroxydisulphate chemiluminescence system in a multichip device

A simple, rapid and sensitive method has been developed for the analysis of fexofenadine (FEX) in pharmaceutical formulations, using a tris(1,10-phenanthroline)–ruthenium(II) [Ru(phen)32+] peroxydisulphate chemiluminescence (CL) system in a multichip device. Various parameters that influence the CL signal intensity were optimized. These included pH, flow rates and concentration of reagents used. Under optimum conditions, a linear calibration curve in the range 0.05–5.0?µg/mL was obtained. The detection limit was found to be 0.001?µg/mL. The procedure was applied to the analysis of FEX in pharmaceutical products and was found to be free from interference from concomitants usually present in these preparations. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Spectrofluorimetric determination of aluminium using 2-hydroxy-1-naphthylidene-(8-aminoquinoline)

A sensitive and selective spectrofluorimetric method has been developed for the rapid determination of aluminium. This method is based on the complex formation between aluminium and 2-hydroxy-1-naphthylidene-(8-aminoquinoline) (HNAQ). The optimum conditions for the complex formation were a metal-to-ligand (M?:?L) stoichiometric ratio of 1:1, a pH of 5.5 and a 0.20 m acetate buffer. The fluorescence of the complex was monitored at an emission wavelength of 502?nm with excitation at 438?nm. Under these conditions, linear calibration curves were obtained in the ranges 0.05–1 and 1–5?ppm. The detection limit was 3.4?ppb for the former and 13.5?ppb for the latter. The maximum relative standard deviation of the method for an aluminium standard of 200?ppb was 1.5% (n = 5). This method was successfully applied for the determination of aluminium in drinking water, pharmaceutical antacid tablets and suspension samples. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Fluorescence emission mechanism and fluorescence properties of ternary Tb(III) complex with diphenyl sulphoxide and bipyridine

A novel ternary complex, TbL5L?(ClO4)3·3H2O, two binary complexes, TbL7(ClO4)3·3H2O and TbL?3.5(ClO4)3·4H2O has been synthesized (using diphenyl sulphoxide as the first ligand L, bipyridine as the second ligand L?). Their composition was analysed by element analysis, coordination titration, IR spectra and 1H-NMR, and the fluorescence emission mechanism, fluorescence intensities and phosphorescence spectra were also investigated by comparison. It was shown that the ternary rare-earth complex showed stronger fluorescence intensities than the binary rare-earth complexes in such material. The strongest characteristic fluorescence emission intensity of the ternary system was 8.23 times, 3.58 times as strong as that of the binary systems TbL7(ClO4)3·3H2O and TbL?3.5 (ClO4)3·4H2O, respectively. By fluorescence analysis it was found that both diphenyl sulphoxide and bipyridine could sensitize the fluorescence intensities of rare-earth ions. In particular, in the ternary rare-earth complex, introduction of bipyridine was of benefit to the fluorescence properties of Tb(III). Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A sensitive and regenerable biosensor for organophosphate pesticide based on self-assembled multilayer film with CdTe as fluorescence probe

A fluorescence biosensor for organophosphorus pesticides was developed. A pH indicator, CdTe quantum dots, were used as an optical transducer of the inhibition of enzyme by analyte. Through the intervening agency of chitosan, the recognition elements (acetylcholinesterase and CdTe) were immobilized onto the surface of quartz by electrostatic attraction to form a self-assembled multilayer film. In the absence of pesticide, acetylcholine was biocatalytically hydrolysed to yield acetic acid and choline. The released acid resulted in pH decrease, which was sensed by the immobilized pH indicator (CdTe). In the presence of pesticide, the action of acetylcholine was reduced; the fluorescence intensity of the film changed and was related to the concentration of pesticide. This multilayer film could be used as the biosensor for monocrotophos, with a detection limit of 3.20?×?10?8 mol/L; the sensitivity was 100 times higher than that of CdTe in aqueous solution. The sensor was easily regenerated, and had good stability and selectivity for organophosphorus pesticides. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Types of interaction of meso-tetraphenylporphyrin with alkali and alkaline-earth metal ions

The cavity in a porphyrin can accommodate metal ions through electron donor–acceptor (EDA) interaction in acetonitrile media without any specially designed fabrication with the porphyrin subunit. Alkali metal ion forms a complex with meso-tetraphenylporphyrin (TP) in 2:1 stoichiometry, while the bivalent Mg2+ ion follows a 1:1 stoichiometry. A fluorescence interaction study indicated that TP can behave like a chemosensor for these ions present in the blood electrolytes. Specifically, for the alkali metal ions intensity-based sensing was observed, due to inhibition of photoinduced electron transfer (PET), entailing enhancement of fluorescence intensity, and for the alkaline-earth Mg2+ a mixed quenching was observed. Na+ and K+ ions can be differentiated depending upon the extent of fluorescence enhancement. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Characterization of the superoxide anion radical scavenging activity by tetracycline antibiotics in aprotic media

The tetracycline family antibiotics are widely used as human and veterinary treatments. The drugs are effective as antibiotics and also show antimicrobial and non-microbial action. However, the antioxidant properties of tetracyclines have not been characterized in aprotic media. To better understand their biological functions, the in vitro superoxide anion radical (O2•¯) scavenging activities of tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline were characterized, along with a very efficient O2•¯ scavenger, tiron, in dimethyl sulphoxide (DMSO), using ultra-weak chemiluminescence (CL). We found that tetracycline, chlortetracycline and doxycycline efficiently inhibited CL from the O2•¯-generating system at concentration levels of 0.02–1.0?mmol/L. Methacycline and oxytetracycline were the O2•¯scavengers at concentration levels of 0.01–0.1?mmol/L, whereas when their concentration was lowered the drugs were capable of generating O2•¯, leading to CL enhancement. For all the data obtained in this study, the scavenging activity for the compounds tested decreased in the following order: tetracycline?>?doxycycline?>?chlortetracycline?>?tiron methacycline?>?oxytetracycline. These results indicate that the tetracycline drugs directly alter O2•¯ redox chemistry in aprotic media. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Capillary electrophoresis analysis of isoniazid using luminol-periodate potassium chemiluminescence system

A rapid and simple capillary electrophoresis method coupled with chemiluminescent (CL) detection was proposed for analysis of isoniazid (ISO) based on the enhancement effect of ISO to CL emission of luminol-periodate potassium reaction. Under the optimal conditions, ISO can be assayed in the range of 7.0 × 10?7 to 3.0 × 10?5?g?mL?1 (R2 = 0.9990) with a limit of detection of 3.0 × 10?7?g?mL?1 (signal-to-noise ratio of 3). The whole analysis process can be completed within 2.5?min with a theoretical plate number of 6258. The relative standard deviations of the signal intensity and the migration time were 3.1 and 1.4% for a standard sample at 1.0 × 10?5?g?mL?1 (n = 5), respectively. The presented novel strategy was successfully applied to the determination of ISO in commercial pharmaceutical preparations and spiked human serum samples. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Bioluminescence characteristics of the fruiting body of Mycena chlorophos

Bioluminescent fungi are widely distributed on land and most belong to the class Basidomycetes. Light of about 530?nm wavelength maximum is emitted continuously. The molecular basis for the light-emitting process remains unclear. We investigated the characteristics of the bioluminescence using cultivated fruiting bodies of M. chlorophos. Only fresh fruiting bodies exhibited long-lasting light emission; rapid decay of light emission was observed with frozen and freeze-dried samples. Freeze-dried samples can be stored at room temperature under dry conditions and may be useful for the isolation of luciferin. The light emission of the fresh fruiting bodies was maintained in various buffers at varying pH; it could be stopped with pH 4 acetate buffer and could be recovered at pH 6. The isolation of luciferin from the fresh fruiting bodies might be possible by the control of buffer pH. The effect of temperature on the light emission of fruiting bodies indicated that bioluminescence in M. chlorophos may involve enzymatic reaction(s). The solubilization of bioluminescent components from the fruiting bodies could not be achieved with various surfactants. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Chemiluminescence determination of antioxidant property of Zizyphus mistol and Prosopis alba during oxidative stress generated in blood by Hemolytic Uremic Syndrome-producing Escherichia coli

This study was undertaken to elucidate the antioxidant effect of Zizyphus mistol and Prosopis alba, with the hypothesis that these fruits can counteract the induction of reactive oxygen species (ROS) caused by toxins produced by Escherichia coli. In the search of nutrients effective against the Hemolytic Uremic Syndrome (HUS), we detected by chemiluminescence a protective role of both plants, due to their natural antioxidants significantly decreasing the levels of ROS induced by toxins from E. coli in blood. The ferric reducing antioxidant power (FRAP) was found to be higher in Z. mistol than in P. alba. The chemical analyses of the phenols and flavonoids present in the fruit extracts indicated that the FRAP correlated with the amount of phenolic compounds, but not with the flavonoids analyzed. Both fruits studied reduce the induction of ROS, and in this way help to prevent the development of complications related to oxidative stress generated in the blood of patients with HUS. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Chemiluminescence investigations of antioxidative activities of some antibiotics against superoxide anion radical

A chemiluminescent technique was applied to determine antioxidative activities of adriamycin, farmorubicin, mitomycin C and bleomycin against superoxide anion radical (O2•) in aprotic medium. The antioxidant capacity was expressed as the decrease in light emission from the O2• solution by and antibiotic. A KO2 solution in dimethyl sulphoxide (DMSO) and 18-crown-6 ether were used for the generation of O2•. The results showed that the examined compounds decreased the chemiluminescence (CL) sum from the O2•-generating system in a dose-dependent manner. Among the antibiotics examined, adriamycin, farmorubicin and bleomycin exhibited antioxidant activity almost comparable to that of 1,2-dihydroxy benzene-3,5-disulphonic acid (tiron), an efficient of the O2• inhibitor. Mitomycin C was two-times less effective as tiron in decreasing the initial CL intensity. The proposed assay with usage of ultraweak CL technique and the KO2–DMSO–crown ether system was useful for the evaluation of antioxidant activity in aprotic solvents. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Flow injection methods for the determination of retinol and ?-tocopherol using lucigenin-enhanced chemiluminescence

Flow injection (FI) methods are reported to determine retinol and ?-tocopherol based on its enhancement affect of lucigenin chemiluminescence (CL) in alkaline medium. Surfactants including Brij-35, Triton X-100, cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate have been reported for the first time to enhance lucigenin CL intensity in the presence of retinol and ?-tocopherol. With Brij-35, the CL intensity was enhanced by 67% for retinol and 58% for ?-tocopherol. CTAB was found to enhance the CL intensity by 16% for retinol whereas for ?-tocopherol, the CL intensity was quenched up to 95%. Retinol could be determined specifically in the presence of ?-tocopherol using CTAB. The calibration graphs were found to be linear up to 1.43?mg/L (R2 = 0.9985, n = 8) with a detection limit (3s) of 1.43 × 10?3?mg/L for retinol and 2.15?mg/L (R2 = 0.9989; n = 8) with a detection limit (3s) of 4.31 × 10?4?mg/L for ?-tocopherol. An injection throughput of 120/h, and relative standard deviations of 0.9–2.8% (n = 4) were achieved in the concentration range studied. The influence of common ions, excipients in pharmaceutical formulations and related organic compounds on the determination of retinol and ?-tocopherol individually was studied. The proposed methods were applied to determine retinol and ?-tocopherol in pharmaceutical formulations and human blood serum. The results did not differ significantly from the CL method and HPLC reference method at 95% confidence level. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Determination of metformin hydrochloride using precolumn derivatization with acetaldehyde and capillary electrophoresis coupled with electrochemiluminescence

A novel method was developed using capillary electrophoresis (CE) coupled with tris(2,2?-bipyridyl)ruthenium(II) electrogenerated chemiluminescence (ECL) for highly sensitive detection of metformin hydrochloride (MH) derivatizatized with acetaldehyde. The precolumn derivatization of MH with acetaldehyde was performed in phosphate buffer solution (0.3?mol/L, pH 7.5) at room temperature for 120?min. The effects of acetaldehyde concentration, buffer pH, electrokinetic voltage and injection time were investigated. Under optimized detection conditions, the MH ECL detection sensitivity was more than 120 times that without derivatization. The linear concentration range for MH was 0.001–15.00??g/mL (with a correlation coefficient of 0.9992). The detection limit was 0.31?ng/mL with a signal:noise ratio of 3. The recoveries of MH in human urine were in the range 98.50–99.72%. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Synthesis and luminescence properties of Ca3Ga2Si3O12:RE3+ (RE?=?Eu/Tb) powder phosphors

Rare earth ions (Eu3+ or Tb3+)-activated Ca3 Ga2 Si3O12 (CaGaSi) phosphors were synthesized by using a sol–gel method. Photoluminescence spectra of Eu3+:CaGaSi phosphors exhibited five emission bands at 578, 592, 612, 652 and 701?nm, which were assigned to the transitions (5D0???7F0, 7F1,7F2, 7F3 and 7F4), respectively, with an excitation wavelength of ?exci?=?392?nm. Among these, the transition 5D0???7F2 (612?nm) displayed bright red emission. In the case of Tb3+:CaGaSi phosphors, four emission bands were observed at 488 (5D4???7F6), 543 (5D4???7F5), 584 (5D4???7F4) and 614?nm (5D4???7F3) from the measurement of PL spectra with ?exci?=?376?nm. Among these, the transition 5D4???7F5 at 543?nm displayed bright green emission. The structure and morphology of the phosphors were studied from the measurements of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX) results. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Interaction of ?-cyclodextrin-capped CdSe quantum dots with inorganic anions and cations

A facile method was developed for the preparation of water soluble ?-Cyclodextrin (?-CD)-modified CdSe quantum dots (QDs) (?-CD-QDs) by directly replacing the oleic acid ligands on the QDs surface with ?-CD in an alkaline aqueous solution. The as-prepared QDs show good stability in aqueous solution for several months. Oxoanions, including phosphoric acid ion, sulphite acid ion and carbonic acid ion, affect the fluorescence of ?-CD-QDs. Among them, H2PO4– exhibited the largest quenching effect. For the polyprotic acids (HO)3AO, the effect of acidic anions on the fluorescence of ?-CD-QDs was in the order: monoanion (HO)2AO2– > dianion (HO)AO32– >> trianion AO43–. After photoactivation for several days in the presence of anions at alkaline pH, the ?-CD-QDs exhibited strong fluorescence emission. The effect of various heavy and transition metal ions on the fluorescence properties of the ?-CD-QDs was investigated further. It was found that Ag+, Hg2+ and Co2+ have significant quenching effect on the fluorescence of the ?-CD-QDs. The Stern–Volmer quenching constants increased in the order: Hg2+ < Co2+ <Ag+. The adsorption model of metal ions on ?-CD-QDs was explored. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Determination of trace carvedilol by solid substrate–room temperature phosphorimetry, based on its activating effect on hypochlorite-oxidizing amaranth using sodium dodecyl benzene sulphonate as sensitizer

This work proposes a simple and sensitive solid substrate–room temperature phosphorimetry (SS–RTP) for the selective determination of carvedilol (CV). The method is based on the sensitizing effect of sodium dodecyl benzene sulphonate (SDBS) on CV to activate the oxidation between NaClO and amaranth, resulting in the intense quenching of room temperature phosphorescence (RTP) of the system. Compared with non-SDBS system, the reduction of phosphorescence intensity (?Ip) with SDBS is 16.5 times higher and is directly proportional to the content of CV, covering a wide range 0.080–16.00?fg/spot. The regression equation of the working curve can be expressed as ?Ip?=?0.7780?+?7.057 mCV (fg/spot) (correlation coefficient (r)?=?0.9976, n?=?8), with a detection limit (LD) of 0.020?fg/spot (corresponding concentration is 5.1?×?10?14?g/mL, sample volume is 0.40??L/spot). This sensitive method has also been applied to determine trace CV in human plasma and the results agreed with synchronous fluorimetry (SF). The activation energy (E) and rate constant (k) of this activating reaction were 69.04?kJ/mol and 3.580?×?10?4?s?1, respectively. The reaction mechanism is also discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Flow-injection chemiluminescent determination of estrogen benzoate using the tris(1,10-phenanthroline) ruthenium(II)–permanganate system

Chemiluminescence (CL) detection for the determination of estrogen benzoate, using the reaction of tris(1,10–phenanthroline)ruthenium(II)–Na2SO3–permanganate, is described. This method is based on the CL reaction of estrogen benzoate (EB) with acidic potassium permanganate and tris(1,10–phenanthroline)ruthenium(II). The CL intensity is greatly enhanced when Na2SO3 is added. After optimization of the different experimental parameters, a calibration graph for estrogen benzoate is linear in the range 0.05–10?µg/mL. The 3?s limit of detection is 0.024?µg/mL and the relative standard deviation was 1.3% for 1.0?µg/mL estrogen benzoate (n = 11). This proposed method was successfully applied to commercial injection samples and emulsion cosmetics. The mechanism of CL reaction was also studied. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Luminescence studies on Al4B2O9:Eu2+ phosphor crystals

A novel blue-emitting phosphor, Eu2+-doping Al4B2O9, was prepared via a modified solid-state reaction. Al4B2O9:Eu2+ nanoparticles with diameters varying in a range from 20 to 50?nm were obtained using urea as an auxiliary reagent at the optimum temperature of 850°C. The crystallization and particle sizes of Al4B2O9:Eu2+ were investigated using powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Photoluminescence (PL) results showed that Al4B2O9:Eu2+ phosphor could be efficiently excited by the ultraviolet region from 240 to 410?nm, exhibiting bright blue emission. Further investigation on concentration-dependent emission spectra indicated that the Al3.997B2O9:Eu2+0.003 phosphor exhibited the strongest luminescent, and the relative PL intensity decreased with increasing Eu2+ concentration due to concentration quenching. In addition, the concentration quenching for the one-Eu-site emission centers was caused by the electric multipole–multipole interaction. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Flow system for the automatic screening of the effect of phenolic compounds on the luminol–hydrogen peroxide–peroxidase chemiluminescence system

In this work, an automated flow-based procedure for the screening of the effect of the different phenolic compounds on the chemiluminescence (CL) luminol–hydrogen peroxide–horseradish peroxidase (HRP) system is presented. This procedure involves the combination of multisyringe flow injection analysis (MFSIA) and sequential injection analysis (SIA) techniques and exploits the ability of the different subgroups of phenols, such as cholorophenols, nitrophenols, methylphenols and polyphenols, to enhance or inhibit the described CL system. The implementation of this reaction in the SIA–MSFIA system enabled favourable and precise conditions to evaluate the effect of phenolic compounds, as it involves an in-line reaction between the phenolic derivative, hydrogen peroxide and peroxidase and subsequent oxidized HRP intermediates generation prior to the fast reaction with the chemiluminogenic reagent. Several studies were then performed with the aim of establishing the appropriate flow system configuration and reaction conditions. It was shown that phenol and chlorophenols produce an enhanced CL response and nitrophenols, methylphenols and polyphenols are inhibitors within the range of concentrations studied (1–100?mg/L). Based on these studies, the developed method was applied to the determination of total polyphenol and phenol content in wine/grape seeds and water samples, respectively, and the results obtained showed good agreement with those furnished by the corresponding Folin–Ciocalteu and 4-aminoantipyrine reference methods. The developed approach is further pursued by designing an automated generic tool for performing studies of peroxidase-catalysed CL reactions of luminol focused on the detection of compounds that will affect the rate of those reactions. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Cathodic electrochemiluminescent behavior of luminol at nafion–nano-TiO2 modified glassy carbon electrode

The electrochemiluminescence (ECL) behavior of luminol on a nafion–nano-TiO2 modified glassy carbon electrode (nafion–nano-TiO2GCE) was studied. Two ECL peaks (ECL-1 and ECL-2) were found during cathodic potential scanning. ECL-1 at ca ?0.4?V (vs AgAgCl reference electrode) came from the reaction between luminol and active oxygen anion produced at the GCE surface directly, while ECL-2 at ca ?0.9?V (vs AgAgCl reference electrode) came from the reaction between luminol and the active oxygen anion catalyzed by TiO2. The possible mechanism for the generation of both ECL peaks has been proposed. The reproducibility of the ECL intensities on nafion–nano-TiO2GCE at ECL-1 and ECL-2 was good, with relative standard deviations (n = 10) of 4.3 and 1.3%, respectively. The ECL-2 generated at the nafion–nano-TiO2GCE surface was further developed to detect the dissolved oxygen, and a detection limit of 0.02?mg/L was achieved. The proposed method was applied to detect dissolved oxygen in water with satisfactory result. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Investigation on the analytical application of cationic Gemini surfactant 12-4-12 and its interaction with DNA

The quantitative determination of nucleic acids is of great importance in fundamental research and clinical diagnosis. In this work, the interaction between DNA and cationic Gemini surfactant 12-4-12, which changes the conformation of DNA, was investigated by UV-vis absorption, FT-IR spectra and steady-state fluorescence techniques. A hydrophobic pyrene probe was used to investigate the microenvironment change and calculate the critical micelle concentration (CMC) of Gemini surfactant 12-4-12 (0.69?mmol/L), which is close to the value obtained from the conductivity method (0.79?mmol/L). A new detection assay for DNA is proposed with Gemini surfactant 12-4-12, using the resonance light-scattering (RLS) technique. The formation of DNA–12-4-12 complex resulted in enhanced RLS signals at 368?nm, which is proportional to DNA concentration in the range 0.304–5.32?mg/L, with a detection limit of 35?µg/L. Most coexisting substances do not interfere in the detection and four synthetic samples were analyzed satisfactorily. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Cathodic electrochemiluminescence of the peroxydisulphate–ciprofloxacin system and its analytical applications

The cathodic electrochemiluminescence (ECL) of peroxydisulphate (S2O82?)–ciprofloxacin (CPF) system at a wax-impregnated graphite electrode was studied. When CPF was absent, S2O82? was electrochemically reduced to sulphate free radical (SO4•?), and dissolved oxygen absorbed on the electrode surface was reduced to protonated superoxide anion radical (HO2•). The HO2• was oxidized by SO4•? to produce molecular oxygen in both singlet and triplet states. Some of the singlet molecular oxygen (1O2) further combined through collision to be an energy-rich precursor singlet molecular oxygen pair (1O2)2. A weak ECL was produced when 1O2 or (1O2)2 was converted to ground-state molecular oxygen (3O2). When CPF was present, a stronger ECL was produced, which originated from two emitting species. The main emitting species was excited state CPF (CPF*), which was produced by accepting energy from (1O2)2. The other emitting species was excited singlet molecular oxygen pair [(1O2)2*], which originated from the chemical oxidation of CPF by SO4•? and dissolved oxygen. Based on the stronger ECL phenomenon, an ECL method for the determination of either S2O82? or CPF was proposed. The proposed ECL method has been applied to the determination of CPF in pharmaceutical preparations. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Effect of alcohol drinking and cigarette smoking on neutrophil functions in adults

In recent years, the effects of smoking and excessive alcohol consumption on immune function have been studied, due to a high prevalence of infection or cancer in heavy drinkers, and the combination of smoking and drinking was considered to be a carcinogenic risk. However, the effect of smoking and drinking on systemic immune function has yet to be clearly understood. In this study, we investigated neutrophil functions (reactive oxygen species (ROS) productive activity, phagocytic ability and serum opsonic activity) and their relationship with alcohol consumption or amount of smoking. In total there were 731 male and female adult subjects who participated in the Iwaki Health Promotion Project in 2005. Multiple regression analysis showed a trend of increased ROS production in male subjects and a statistically significant decrease was observed in phagocytic activity caused by smoking in female subjects. In other words, oxidative stress caused by smoking in male subjects may be involved in ROS production from neutrophils. Decreased phagocytic activity of neutrophils caused by smoking suggests that host defense functions were impaired in female subjects. A relationship between neutrophil functions and the amount of alcohol consumption was not observed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Determination of dipyridamole using TCPO–H2O2 chemiluminescence in the presence of silver nanoparticles

The method is based on the fact that dipyridamole can enhance the chemiluminescence (CL) emission from the redox reaction of bis (2,4,6-tricholorophenyl) oxalate (TCPO) with H2O2 in the presence of silver nanoparticles (AgNPs). The CL reaction mechanism was discussed. The effect of concentrations of TCPO, H2O2, AgNPs and pH value on the CL reaction were investigated. Under the optimum conditions, the linear dynamic range was 1.0–1000?×?10?9 g/mL and the detection limit (3?) was 9?×?10?10 g/mL. The relative standard deviation (RSD) was 4.8% for 1.0?×?10?9 g/mL dipyridamole (n?=?7). The proposed method has been successfully applied to the determination of dipyridamole tablets and the recovery was 99–103%. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Luminescence studies of decomposition of ceric sulfate

Literature results on the decomposition products of ceric sulfate are inconsistent. A group of researchers claim that ceric sulfate decomposed to ceric oxide without going through a cerous phase at any stage, while the results of the other group show that cerous sulfate is formed as an intermediate phase. Most of these studies used DTA/TGA, XRD and IR techniques. Cerous compounds can also be detected by the characteristic luminescence of Ce3+. Using such techniques we show that the thermal decomposition of both monoclinic and ?Ce(SO4)2·4H2O in air at 500°C leads to the formation of cerous sulphate. Use of various atmospheres (air/N2/vacuum) and temperature profiles for the decomposition by the different researchers may be responsible for the discrepancies between literature results. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Resonance light scattering technique for determination of polychlorinated biphenyls with silver nanoparticles

In this paper, a simple and novel method for the determination of polychlorinated biphenyls (PCBs), using silver nanoparticles (AgNPs) as a resonance light scattering (RLS) probe, is proposed. Under optimized conditions, there existed linear relationships between the enhancing RLS intensity of the system and the concentrations of PCBs in the range 8.0?×?10?8?1.0?×?10?6?g mL?1 for 2,4,4?-trichlorbiphenyl (PCB28), 9.0?×?10?8?1.0?×?10?6?g mL?1 for 2,2?,5,5?-tetrachlorbiphenyl (PCB52) and 4.0?×?10?8?1.0?×?10?6?g mL?1 for 3,3?,4,4?-tetrachlorobiphenyl (PCB77). The corresponding detection limits (S/N?=?3) were 2.6?×?10?8?g mL?1 for PCB28, 3.3?×?10?8?g mL?1 for PCB52 and 6.3?×?10?9?g mL?1 for PCB77, respectively. Finally, the mechanism of RLS enhancement was also studied. The results indicated that PCBs were adsorbed on the surface of AgNPs to form larger AgNP–PCB aggregates, resulting in the RLS enhancement of the system. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A fluorescent probe for biothiols based on the conjugate addition of thiols to ?,?-unsaturated ester

A sensitive fluorogenic probe 1 for biothiols was developed based on the Michael addition reaction. The probe 1 was readily synthesized via the reaction of 2-(4?-hydroxyphenyl) benzimidazole (HPBI) with acryloyl chloride and shows weak fluorescence emission. Upon mixing with biothiols, the fluorescence of 1 is significantly enhanced due to the conjugate addition of thiols to the ?,?-unsaturated carbonyl moiety, thus eliminating the photoinduced electron transfer (PET) quenching of the fluorophore by the intramolecular carbon–carbon double bond. Cysteine (Cys) was selected as the representative thiol in the spectral experiment. A good linear relationship was obtained from 1.0 to 30.0?µmol?L?1 for Cys and the detection limit was 0.17?µmol?L?1. Furthermore, probe 1 was highly selective for biothiols without the interference of some biologically relevant analytes and has been applied to detecting biothiols in human urine samples. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Synthesis and characterization of a novel high luminescent gold-2-mercapto-1-methyl-imidazole complex

Synthesis and characterization of a new gold-2-mercapto-1-methyl imidazole are reported. This new organic material shows an extraordinary fluorescence activity (superfluorescence) up to 220°C with an unusual quantum yield of 0.2. Both fluorescence and NMR spectroscopy were applied to understand the behavior of the gold-2-mercapto-1-methylimidazole complex. Results suggest that the superfluorescence activity can be attributed to the shrinking of the HOMO-LUMO band gap energy following complexation of the organic imidazole system with gold. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Luminescent properties of europium complexes with bis(diphenylphosphino)alkane dioxides

Eu(NO3)3?5H2O and EuCl3?6H2O were allowed to react with bis(diphenylphosphino)alkane dioxides Ph2P(O)(CH2)nP(O)Ph2 (n?=?2, 4, 6) to obtain polymeric and binuclear complexes. The prepared compounds were structurally characterized by X-ray diffraction. Luminescence measurements (emission and excitation spectra, quantum yields, lifetimes) were compared with crystallographic data in order to find a relationship between luminescent properties of the Eu(III) complexes and their structures. The Eu(III) polymers, especially [Eu(dpphO2)2Cl2]+Cl–}n, have shown extremely long luminescence lifetimes, up to 3.73?ms, as a result of a highly protecting hydrophobic shield. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Determination of clomipramine by flow-injection analysis with acidic potassium permanganate–formic acid chemiluminescence detection

A sensitive and simple chemiluminescent (CL) method for the determination of clomipramine has been developed by combining the flow-injection analysis (FIA) technique, which is based on the CL intensity generated from the redox reaction of potassium permanganate (KMnO4)–formic acid in sulphuric acid (H2SO4) medium. Under the optimum conditions, the linear range for the determination of clomipramine was 0.04–4?µg/mL, with a correlation coefficient of 0.9988 (n?=?10) and a detection limit of 0.008?µg/mL (3?), and the relative standard deviation (RSD) for 2.0?µg/mL clomipramine (n?=?11) is 1.26%. The proposed method has been successfully applied to the determination of the studied clomipramine in pharmaceutical preparations. The possible reaction mechanism is discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Online naphazoline quality control by micellar-enhanced spectrofluorimetry

The aim of this study was to develop a method for online spectrofluorimetric quality control of naphazoline (NPZ) in pharmaceuticals and raw drugs. A combination of a flow-injection analysis (FIA) system with micellar-enhanced fluorescence detection is presented as a powerful alternative for the rapid and sensitive analysis of naphazoline. Since NPZ shows low native fluorescence, the use of an anionic surfactant, such as sodium dodecyl sulphate (SDS), provides a considerable enhancement of fluorescence intensity and the nature of the technique allows a possible and easy adaptation to a FIA system. Using ?exc?=?280?nm and ?em?=?326?nm, a good linear relationship (LOL) was obtained in the range 0.003–10?µg mL?1 with a detection limit (LOD) of 3?×?10?4?µg mL?1 (s/n?=?3). Parameters related to the nature of the analytical signal and to the FIA manifold were optimized. Satisfactory recoveries were obtained in the analysis of commercial pharmaceutical formulations. The proposed method is simple, accurate and allows for high-speed sampling and considerably shorter analysis times. In addition, it requires inexpensive equipment and reagents and has easy operational conditions and no side effects, thus avoiding environmental pollution through toxic waste. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

The ‘Gator’ Mouse Suit for early bioluminescent metastatic breast cancer detection and nanomaterial signal enhancement during live animal imaging

Optical imaging is a cornerstone of modern oncologic research. The aim of this study is to determine the value of a new tool to enhance bioluminescent and fluorescent sensitivity for facilitating very-low-level signal detection in vivo. Experimental:?For bioluminescent imaging experiments, a luciferase expressing breast cancer cell line with metastatic phenotype was implanted orthotopically into the mammary fat pad of mice. For fluorescent imaging experiments, near-infrared (NIR) nanoparticles were injected intratumorally and subcutaneously into mice. Images were compared in mice with and without application of the ‘Gator’ Mouse Suit (GMS). Results:?The GMS was associated with early detection and quantification of metastatic bioluminescent very-low-level signal not possible with conventional imaging strategies. Similarly, NIR nanoparticles that were undetectable in locations beyond the primary injection site could be visualized and their very-low-level signal quantifiable with the aid of the GMS. Conclusion:?The GMS is a device which has tremendous potential for facilitating the development of bioluminescent models and fluorescent nanomaterials for translational oncologic applications. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Quantum efficiencies, absolute intensities and signal-to-blackbody ratios of high-temperature laser-induced thermographic phosphors

There are a number of issues related to high-temperature phosphor thermometry, which include measurement of faster decays, decreasing emission intensity and rising levels of blackbody radiation, that will impose limits on the maximum delectable temperature. This paper provides absolute intensity measurements, quantum efficiencies and signal-to-blackbody radiation ratios at peak emission wavelengths, at various temperatures (20–1400°C), for Y2O3:Eu, YAG:Tb and YAG:Tm thermographic phosphors under 266 and 355?nm excitation from a Q-switched Nd:YAG laser. These terms are beneficial in a number of ways for engineers wanting to use a phosphor thermometry solution at high temperatures. They may also provide additional insight to the physical luminescence processes of phosphors at high temperatures. The phosphor signal:blackbody radiation ratio is useful because it combines the effects of blackbody radiation and phosphor emission intensities at various temperatures, providing a valuable quantitative evaluation that can be used as a design aid for phosphor selection. A figure of merit is the temperature when the blackbody radiation equals the phosphor emission (ratio?=?1); this is the cross-over temperature at which the blackbody radiation rapidly starts to overtake and mask out phosphor emissions. To the best of our knowledge no such work exists previously. The results presented show a variation in phosphor intensity with increasing temperature, and although the intensity and quantum efficiencies for Y2O3:Eu and YAG:Tb were much greater than YAG:Tm at low temperatures, YAG:Tm was found to be the most efficient phosphor investigated at higher temperatures (>900°C). With a peak emission wavelength of 458?nm, YAG:Tm experienced the lowest proportion of blackbody radiation therefore its advantage at higher temperatures was further amplified and was found to offer an advantage of approximately +350°C and +250°C increased upper temperature capability compared to Y2O3:Eu and YAG:Tb phosphors, respectively. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

High-sensitivity spectrofluorimetric determination of tiopronin based on inhibition of hemoglobin

A highly sensitive and simple spectrofluorimetric method for the determination of tiopronin based on its inhibitory effect on the hemoglobin-catalyzed reaction of H2O2 and l-tyrosine was developed. The concentration of tiopronin is linear with decreased fluorescence (?F) of the system under the optimal experimental conditions. The calibration graph is linear in the range 1.23 × 10?8 to 3.06 × 10?5?mol?L?1 with a detection limit of 6.13 × 10?9?mol?L?1. The relative standard deviation was 4.38% for 11 determinations of 6.13 × 10?6?mol?L?1. This method can be used for the determination of tiopronin in pharmaceuticals with satisfactory results. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Bioluminescent enzyme assay for the indication of plant stress in enclosed life support systems

The application of bioluminescent sensors for monitoring key metabolites and enzymes that are indicators of stress in plants is demonstrated. The sensitivity of bioluminescent assay for NAD(P)H and NAD(P)+ was about 0.5 and 1?nmol, respectively. The levels of NAD(P)H and NAD(P)+ in radish (Raphanus sativus) root extracts from controls and from stress-induced conditions were compared. To induce environmental stress, the plants were grown in enclosed environmental chambers with low pressure (9 or 32?kPa), high humidity (>80%) and low oxygen partial pressure (down to 3.3–6.5?kPa). The concentrations of NAD(P)+ and NAD(P)H in plants varied under stress conditions. Decreasing both total pressure from 101.5 to 32 or 9?kPa and partial pressure of oxygen increased the ratio of NAD(P)+/NAD(P)H from 0.2 to 4 or 6, respectively. The increase in this ratio suggests that plants are undergoing stress in these hypobaric environments. The developed bioluminescent assay for quantification of pyridine nucleotides in plant tissues is rapid, low-cost and easily performed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Characteristics of rare earth (RE = Eu, Tb, Tm)-doped Y2O3 phosphors for thermometry

The temperature-dependent photoluminescences of Y2O3:Eu (6% Eu), Y2O3:Tb (4% Tb) and Y2O3:Tm (1% Tm) were investigated for high-temperature phosphor thermometry. Two different phases, the monoclinic phase and cubic phase, were considered because the fluorescence spectra vary with the phase. To employ the intensity ratio method, we investigated their photoluminescence spectra under the excitation light of an Hg–Xe lamp as the temperature was elevated from room temperature to more than 1200?K. As a result, it was confirmed that the luminescence intensity of all of the phosphors varied with elevating temperature, i.e. thermal quenching, with the variations depending on the type of rare earth impurity and their phases. The results indicate that Y2O3:Eu phosphors are applicable to the intensity ratio method because they show appropriate variations in the intensity ratio of two emission lines, and they also have strong and sharp peak intensities without excessive optical noise or black body radiation over a wide range of temperatures. The intensity ratios for Y2O3:Tb provide such small variations with temperature that the temperature resolution is low, despite the strong emission intensities. As for Y2O3:Tm, the intensity ratios also have a low temperature resolution and their emission intensities are weak. Therefore, Y2O3:Tb and Y2O3:Tm are not appropriate for the intensity ratio method for phosphor thermometry. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A label-free immunoassay using eggshell membrane as matrix and poly(diallyldimethylammonium chloride) as light-scattering enhancer

A label-free immunoassay system using eggshell membrane as a matrix was developed. A common spectrofluorometer was used to collect light-scattering signals. The rabbit anti-human IgG (Ab) was first immobilized on the eggshell membrane with glutaraldehyde. Then, based on the immunoreactions and electrostatic interaction, the target human IgG antigen (Ag) and poly(diallyldimethylammonium chloride) (PDDA) were captured on the eggshell membrane. It was found that the light-scattering signal resulting from the PDDA immunotargeted on modified eggshell membrane was related to the concentration of target antigen. Under the optimal conditions, the light scattering intensity is directly proportional to the concentration of Ag in the range of 5.00–500?ng/mL (r?=?0.995) with the limit of detection of 2.31?ng/mL [signal:noise ratio (S:N)?=?3]. The proposed method was successfully applied to the determination of IgG in human serum, and the results were in agreement with those obtained by a general immunonephelometric method. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

The photodynamic effect: the comparison of chemiexcitation by luminol and phthalhydrazide

The presence of light, oxygen and photosensitizer (organic dye) is required for the photodynamic effect. Light and photosensitizer are harmless by themselves, but when combined with oxygen, reactive oxygen species (ROS) can be produced. This photodynamic effect is used in photodynamic therapy (PDT); the production of ROS as lethal cytotoxic agents can inactivate tumor cells. However, during PDT, there are many difficulties, so it is not possible to excite the photosensitizer using a laser, a source of light at the wavelengths specific to the photosensitizer (in visible region of the spectrum). Chemiluminescence is the light emission as a result of a chemical reaction. It is possible to use a chemiluminescent mixture to excite the photosensitizer even if the light emission does not conform to the absorption maximum of the photosensitizer. Luciferin and luminol have been used as chemiluminescent compounds (energizers) for the excitation of the photosensitizers. The aim of this work was to compare the chemiexcitation of some selected photosensitizers (e.g. fluorescein, eosin, methylene blue, hypericin and phthalocyanines) by chemiluminescent mixtures containing luminol (high chemiluminescent quantum yield) or phthalhydrazide (low chemiluminescent quantum yield) on some Gram-positive (Enterococcus faecalis, Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa, E. coli) bacteria and some cell lines (NIH3T3 and MCF7). The efficiency of the chemiexcitation was dependent on the kind of the photosensitizer and on the type of the bacterial strain or cell line and was independent of the energizers. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Effect of bis-triazoles on a ribose-based fluorescent sensor

We synthesized two ribosyl-based fluorescent sensors. Both sensors have an anthracene as the fluorophore, but they differ in the recognition site for metal ions. One (3) has two ribosyl esters, and the other (6) has two triazole groups linked to two ribosyl esters. Among the metal ions examined in MeOH, compound 3 displayed a large chelation-enhanced fluorescence (CHEF) effect with Hg2+ and Cu2+ ions, and compound 6 displayed a large chelation-quenched fluorescence (CHQF) effect with Cu2+ and Ni2+ ions. The results demonstrated that the absence (sensor 3) and presence (sensor 6) of an incorporated bis-triazole group in a ribosyl-based fluorescent sensor conferred different preferences and distinct binding modes for metal ions. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Determination of subnanomolar concentrations of vanadium in environmental water samples using flow injection with luminol chemiluminescence detection

A flow injection chemiluminescence method is described for the determination of subnanomolar concentrations of vanadium in environmental water samples. The procedure is based on the oxidation of luminol in the presence of dissolved oxygen catalyzed by vanadium(IV). Vanadium(V) reduction and preconcentration of vanadium(IV) was carried out using in-line silver reductor and 8-hydroxyquinoline chelating columns at pH 3.15, respectively. The calibration graph for vanadium(IV) was linear in the concentration range of 0.025–10?µg/L with relative standard deviation in the range of 0.4–5.58%. The detection limit (3s blank) was 3.8 × 10?3?µg/L without preconcentration; when the vanadium(IV) was preconcentrated with an 8-HQ column for 1?min (2.0?mL of sample loaded), the detection limit of 5.1 × 10?4?µg/L was achieved. One analytical cycle can be completed in 2.0?min. The analysis of certified reference materials (CASS-4, NASS-5 and SLRS-4) by the proposed method showed good agreement with the certified values. The method was successfully applied to the determination of total dissolved vanadium in environmental water samples. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

A novel chemiluminescent flow-injection analysis of transferrin by its reduction of the luminol—hydrogen peroxide reaction catalysed by meso-tetra-(3-methoxyl-4-hydroxyl) phenyl manganese porphyrin

Based on the inhibition effect of transferrin (Tf) on the reaction of the luminol–hydrogen peroxide (H2O2) chemiluminescence (CL) system, catalysed by meso-tetra-(3-methoxyl-4-hydroxyl) phenyl manganese porphyrin (MnP) as a mimetic enzyme of peroxides, a sensitive flow-injection CL method has been developed for the determination of Tf in an alkaline medium. The CL reaction was carefully investigated by examining the variations of reaction conditions. Under optimum conditions, the linear range for the determination of transferrin was 0.04–20.0??g/mL and the detection limit was 1.62?ng/mL. This proposed method was sensitive, convenient and simple, and has been successfully applied to the determination of transferrin in a serum sample. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Prooxidant action of carazolol in the Fenton-like reaction

Carazolol [4-(2-hydroxy-3-isopropyl-amino-propoxy)-carbazole], a ?3-adrenoceptor agonist, is clinically used in the treatment of hypertension, cardiac arrhythmias and angina pectoris. Despite the beneficial effect of the drug, its high dose may contribute to cardiotoxicity. This study was conducted to examine whether carazolol can influence hydroxyl radical formation by a Fenton-like reaction [Co(II) + H2O2 + HO-] in the presence of ethylenediaminetetraacetic acid. The oxygen free radicals and singlet oxygen (1O2) formation was traced by three different assay methods: chemiluminescence (CL), an electron spin resonance (ESR) spin trapping with 2,2,6,6-tetramethyl-4-piperidine and 5,5-dimethyl-1-pyrroline-1-oxide, and spectrophotometric determination of 1O2 based on bleaching of p-nitrosodimethylaniline. The effect of hydroxyl radical inhibitors and 1O2 quenchers on peroxidation of carazolol was also examined. The results indicated that carazolol enhanced the HO radical and 1O2 formation in a Fenton-like reaction. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Chemical and photophysical mechanism of fluorescence enhancement of 3-quinolineboronic acid upon change of pH and binding with carbohydrates

The free 3-quinolineboronic acid (3-QBA) with the lowest (n–?*) excited singlet is non- or weakly fluorescent while protonated 3-QBA has the lowest (?–?*) excited singlet state and is highly fluorescent. The hybridization of boronic atom or charge transfer from aromatic ring to boronic acid group plays a secondary role in affecting fluorescence intensity. Binding with carbohydrate at a proper acidity, the hybridization of boron atom changes from sp2 to sp3 and the nitrogen atom in the quinoline ring is partially protonated, resulting in large enhancement of fluorescence. Meanwhile, the fluorescent lifetime of 3-QBA produces obvious change by binding with carbohydrates. Quinoline boronic acid is an important water-soluble fluorescence sensor for carbohydrate recognition. Both the remarkable changes in intensity and lifetime of 3-QBA can act as working parameters in recognition of carbohydrates at physiological pH. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Aqueous synthesis of CdTe/CdS/ZnS quantum dots and their optical and chemical properties

In this paper, we described a strategy for synthesis of thiol-coated CdTe/CdS/ZnS (core–shell–shell) quantum dots (QDs) via aqueous synthesis approach. The synthesis conditions were systematically optimized, which included the size of CdTe core, the refluxing time and the number of monolayers and the ligands, and then the chemical and optical properties of the as-prepared products were investigated. We found that the mercaptopropionic acid (MPA)-coated CdTe/CdS/ZnS QDs presented highly photoluminescent quantum yields (PL QYs), good photostability and chemical stability, good salt tolerance and pH tolerance and favorable biocompatibility. The characterization of high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and fluorescence correlation spectroscopy (FCS) showed that the CdTe/CdS/ZnS QDs had good monodispersity and crystal structure. The fluorescence life time spectra demonstrated that CdTe/CdS/ZnS QDs had a longer lifetime in contrast to fluorescent dyes and CdTe QDs. Furthermore, the MPA-stabilized CdTe/CdS/ZnS QDs were applied for the imaging of cells. Compared with current synthesis methods, our synthesis approach was reproducible and simple, and the reaction conditions were mild. More importantly, our method was cost-effective, and was very suitable for large-scale synthesis of CdTe/CdS/ZnS QDs for future applications. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Direct chemiluminescence determination of penicillin G potassium and a chemometrical optimization approach

A highly selective and simple chemiluminescence (CL) method for determination of penicillin G potassium (PGK) was developed. In the proposed method, CL was elicited from PGK upon its oxidation with H2O2. The light emission was enhanced in the presence of N-cetyl-N,N,N-trimethylammonium bromide (CTMAB). An experimental design, central composite design (CCD), was used to realize the optimized variables, including pH, surfactant (CTMAB) and H2O2 concentrations. Under optimum condition, the calibration graph was linear in the range 3.3?×?10?3–3.3?×?10?1?mmol/L, with a detection limit of 8.8?×?10?4?mmol/L for PGK. The precision was calculated by analysing samples containing 1.6?×?10?1?mmol/L PGK (n?=?5) and the relative standard deviation (RSD) was 1.40%. The utility of this method was demonstrated by determining PGK in pharmaceutical formulations for injection. The proposed method was validated by a reference method. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Improvement of photoluminescence of Cu+ ion in Li2SO4

The synthesis of the Li2SO4: Cu phosphor using a wet chemical method is reported here. The XRD technique showed the crystalline nature of the prepared material. The presence of Na and K in the host affected the observed photoluminescence characteristics of Li2SO4: Cu. Photoluminsecent emission spectra of Li2SO4: Cu phosphor showed a very strong prominet peak at 387?nm in the indigo region due to 3d9 4?s1 ? 3d10 transition of the Cu+ ion. The increase in peak intensity of the PL spectrum suggests that Cu+ acts as the luminescence center in the present matrix. Copyright © 2010 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Dy3+-activated NaM4 (VO4)3 (M = Ca, Ba, Sr) phosphor for near-UV solid-state lighting

We report the photoluminescence characterization of Dy3+-activated NaM4(VO4)3 (M = Ca, Ba, Sr) phosphors prepared by a solid-state method. The synthesis was confirmed by X-ray diffraction (XRD) characterization and photoluminescence (PL) emission results showed sharp blue and yellow bands for NaM4(VO4)3 (M = Ca, Ba, Sr):Dy3+ phosphors at the excitation wavelength of 323?nm, which is near-UV excitation. Thus, these phosphors could be applicable for near-UV excited solid-state lighting devices. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 November 2011 | 6:00 am

Determination of nitrate and nitrite in freshwaters using flow-injection with luminol chemiluminescence detection

A simple and sensitive flow-injection (FI) method for the determination of nitrate and nitrite in natural waters, based on luminol chemiluminescence (CL) detection, is reported. Nitrate was reduced online to nitrite via a copperized cadmium (Cu–Cd) column and then reacted with acidic hydrogen peroxide to form peroxynitrous acid. CL emission was observed from the oxidation of luminol in an alkaline medium in the presence of the peroxynitrite anion. The limits of detection (S:N?=?3) were 0.02 and 0.01?µg?N/L, with sample throughputs of 40 and 90?/h for nitrate and nitrite, respectively. Calibration graphs were linear over the range 0.02–50 and 0.01–50?µg?N/L [R2?=?0.9984 (n?=?8) and R2?=?0.9965 (n?=?7)] for nitrate and nitrite, respectively, with relative standard deviations (RSDs; n?=?3) in the range 1.8–4.6%. The key chemical and physical variables (reagent concentrations, buffer pH, flow rates, sample volume, Cu–Cd reductor column length) were optimized and potential interferences investigated. The effect of cations [Ca(II), Mg(II), Co(II), Fe(II) and Cu(II)] was masked online with EDTA. Common anions (PO43?, SO42? and HCO3?) did not interfere at their maximum admissible concentrations in freshwaters. The effect of salinity on the luminol CL reaction with and without nitrate and nitrite (2 and 0.5?µg?N/L, respectively) was also investigated. The method was successfully applied to freshwaters and the results obtained were in good agreement with those obtained by an automated segmented flow analyser reference method. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 28 October 2011 | 11:03 am

Sensitive spectrofluorimetric determination of tizanidine in pharmaceutical preparations, human plasma and urine through derivatization with dansyl chloride

A sensitive spectrofluorimetric method was developed for the determination of tizanidine in human plasma, urine and pharmaceutical preparations. The method is based on reaction of tizanidine with 1-dimethylaminonaphthalene-5-sulphonyl chloride (dansyl chloride) in an alkaline medium to form a highly fluorescent derivative that was measured at 511?nm after excitation at 383?nm. The different experimental parameters affecting the fluorescence intensity of tizanidine was carefully studied and optimized. The fluorescence–concentration plots were rectilinear over the ranges 50–500 and 20–300?ng/mL for plasma and urine, respectively, detection limits of 1.81 and 0.54?ng/mL and quantification limits of 5.43 and 1.62?ng/mL for plasma and urine, respectively. The method presents good performance in terms of linearity, detection and quantification limits, precision, accuracy and specificity. The proposed method was successfully applied for the determination of tizanidine in pharmaceutical preparations. The results obtained were compared with a reference method, using t- and F-tests. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 28 October 2011 | 11:03 am

Effect of colloidal ?-cyclodextrins–Fe3O4 magnetic nanoparticles on the chemiluminescence enhancement of luminol–Ag(III) complex for rapid and sensitive determination of cysteine in human serum

Colloidals solution of Fe3O4 magnetic nanoparticles (MNPs), capped with ?-cyclodextrins (?-CD) as inclusion complexes, were found to enhance the chemiluminescence (CL) intensity of the luminol–diperiodatoargentate(III) (DPA) system. On injection of cysteine into the luminol–DPA–?-CD–Fe3O4 MNPs inclusion complexes system, the CL intensity is strongly enhanced. The enhanced CL signal is ascribed to the catalytic effect of Fe3O4 MNPs capped with ?-CD, which is assumed to stabilize the CL intermediate. Based on these findings, a rapid and sensitive assay was developed for the determination of cysteine in human serum. The effects of analytical variables on the CL signal were studied and optimized. Under the optimum conditions, the CL intensity was directly proportional to the concentration of cysteine in the range 8.0?×?10–9–1.0?×?10–6?mol/L. The detection limit was 2.8?×?10–9?mol/L (3 Sb/m) and the relative standard deviation (RSD) for 10 replicate determinations of 1.0?×?10–7?mol/L cysteine was 3.5%. The proposed method was applied to the sensitive determination of cysteine in human serum samples, and compared with the Ellman method with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 25 October 2011 | 1:11 pm

The use of outer filter effects for Cu2+ quantitation: a unique example for monitoring nonfluorescent molecule with fluorescence

This article concerns a new and precise strategy for the determination of Cu2+ based on a color reaction and outer filter effects (OFEs). Cu2+ can react with sodium diethyldithiocarbamate trihydrate (DDTC) to form a DDTC–Cu2+ complex with a significant absorption at 447?nm. Being positively correlated with Cu2+, the absorption could be treated as the basis for the determination of Cu2+. When cuvettes containing the complex were fixed in the light path of a fluorescence spectrophotometer, the excitation/emitted light were absorbed by the OFEs, similar to absorption mechanisms of inner filter effects. Under suitable conditions, OFEs from the complex could quantitatively reduce the fluorescence intensities of quinine sulfate and acridine yellow by absorbing the excitation or emission light. Compared with traditional absorption spectroscopy (with a detection limit at 0.9?µmol/L), indirect OEF techniques showed increased sensitivities by about 1 order of magnitude. The strategy could be extended to many different systems where components absorb the excitation wavelength and/or emission wavelength of fluorescers. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 25 October 2011 | 12:59 pm

Catalytic solid substrate–room-temperature phosphorimetry detection for trace cadmium with Cd2+–3.5-generation polyamidoamine dendrimer–Tween-80 complex

3.5-Generation polyamidoamine dendrimers (3.5-G-D) emitted strong and stable room-temperature phosphorescence (RTP) on filter paper when Pb2+ was used as a heavy atom perturber. The RTP signal of 3.5-G-D was sharply enhanced upon the formation of 3.5-G-D–Tween-80 micelle compound. The complex Cd2+–3.5-G-D–Tween-80, generated in the coordination reaction between Cd2+ and the tertiary amidocyanogen on the outer layer of 3.5-G-D in 3.5-G-D–Tween-80 micelle compound, could catalyze KBrO3 to oxidize 3.5-G-D in 3.5-G-D–Tween-80, which caused the sharp quenching of the RTP signal of the system. The phosphorescence intensity change (?Ip) of the system had a linear relationship with the content of Cd2+. Thus a new catalytic solid substrate–room-temperature phosphorimetry (SS-RTP) for the determination of trace cadmium has been established. This highly selective and sensitive method has been applied to determine trace cadmium in biological samples with a limit of detection (LD) of 1.2 ag per spot (when the sample volume was 0.4??L per spot, the corresponding concentration was 3.0?×?10?15?g mL?1), the results agreeing with those obtained by atomic absorption spectrometry. The mechanism of catalytic SS-RTP for the determination of trace cadmium was also discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 24 October 2011 | 7:59 am

Synthesis, X-ray crystal structure and optical properties of novel 2-aryl-3-ethoxycarbonyl-4-phenylpyrido[1,2-a]benzimidazoles

A series of novel 2-aryl-3-ethoxycarbonyl-4-phenylpyrido[1,2-a]benzimidazole derivatives were synthesized by the tandem reaction of 2-benzoyl benzimidazole and (Z)-ethyl 4-bromo-3-arylbut-2-enoate in the presence of potassium carbonate. The compounds were characterized using IR, 1H-NMR, 13C-NMR, HRMS and the structure of 6f was further determined by X-ray crystallography. Both absorption and fluorescence spectra characteristics of the compounds were investigated in acetonitrile and dichloromethane. The results showed that the absorption maxima of the compounds varied from 220 to 284?nm, depending on the structure of 2-aryl group. The fluorescence results revealed that these compounds exhibited blue-green fluorescence (463–475?nm) in dilute solutions and showed acceptable fluorescence quantum yields (?PL?=?0.13–0.73) in dichloromethane. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 17 October 2011 | 8:47 am

Determination of phenformin hydrochloride using molecular imprinting technology coupled with flow-injection chemiluminescence

A novel method was developed using molecular imprinting technology (MIT) coupled with flow-injection chemiluminescence (FI-CL) for highly sensitive detection of phenformin hydrochloride (PH). The phenformin imprinted polymer was synthesized with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. Newly synthesized molecularly imprinted polymer (MIP) particles were packed into a column as a selective recognition element for determination of PH. A CL method for the determination of PH was developed based on the CL reaction of PH with N-bromosuccinimide sensitized by eosin Y in basic media. The optimization of detection conditions was investigated. The CL intensity responded linearly to the concentration of PH in the range 0.09–2.0?µg/mL, with a correlation coefficient of 0.9920. The detection limit was 0.031?µg/mL. The relative standard deviation for the determination of 1.0?µg/mL PH solution was 1.0% (n?=?11). The method was applied to the determination of PH in urine samples, with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 12 October 2011 | 12:38 pm

Chemiluminescence of a cyclometallated iridium(III) complex and its application in the detection of cysteine

Chemiluminescence (CL) of a cyclometallated iridium (III) complex {tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium(III)} in the presence of potassium permanganate and oxalic acid is reported for the first time. Cysteine exhibits sufficient enhancing effect on the CL generated from the cyclometallated iridium(III) complex, which make it possible for the sensitive detection of cysteine using a flow-injection–chemiluminescence (FI–CL) method. The optimum conditions for the chemiluminescence emission were investigated. Under the optimal condition, the linear range for the determination of cysteine was 1.0?×?10–9–5.0?×?10–6?mol/L with a detection limit of 6.9?×?10–10?mol/L. A relative standard deviation of 1.6% was obtained for eight replicate determinations. The mechanisms of CL are proposed and the emitting species was identified as the metal-to-ligand charge-transfer (MLCT) excited states of the iridium complex. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 12 October 2011 | 12:35 pm

Synthesis and luminescence properties of a blue-emitting Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5:Eu2+ phosphor

A novel blue-emitting Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5:Eu2+ phosphor was synthesized via a solid-state reaction. Powder X-ray diffraction (XRD) analysis demonstrated that the Sr3.5Y6.5O2(PO4)1.5(SiO4)4.5 host had a hexagonal crystal structure in the space group P63/m and unit cell parameters a?=?9.418?Å, c?=?6.900?Å. The as-prepared phosphor showed a blue emission and all the main emission peaks were located at around 466?nm for different excitation wavelengths of 297, 333 and 391?nm. The temperature dependence of the photoluminescence property was investigated in the range 20–250?°C, and the emission intensity decreased to 71% of the initial value at room temperature on increasing the temperature to 150?°C. According to the classical theory of fluorescent thermal quenching, the activation energy (?E) for the thermal quenching luminescence of the as-prepared Sr3.45Y6.5O2(PO4)1.5(SiO4)4.5:0.05Eu2+ phosphor was determined to be 0.20?eV. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 10 October 2011 | 8:07 am

One-step method for plasma determination of ibuprofen by chemiluminescence-coupled ultrafiltration and application in a pharmacokinetic study

A simple one-step method is established for plasma determination of ibuprofen and its pharmacokinetic study. The method involves simple sample pre-treatment by dilution, rapid separation by ultrafiltration (UF) and online sensitive detection by chemiluminescence (CL) based on significant intensity enhancement of ibuprofen on the weak CL of potassium permanganate and sodium sulphite in an acidic system. The calibration curve for ibuprofen is linear in the range 0.1–50.0?µg/mL in rat plasma. Average recoveries of ibuprofen at 0.80, 12.0 and 40.0?µg/mL amounted to 98.0?±?4.2%, 101.2?±?3.6% and 99.3?±?5.4%, respectively. Standard deviations of intra- and inter-day measurement precision and accuracy are within ±10.0%. The detection limit for ibuprofen is 10.0?µg/L in plasma samples. Pharmacokinetic study of ibuprofen by the validated method shows that the mean plasma drug concentration–time course confirms to a classical two-compartment open model with first-order absorption. The proposed method will be an alternative for pre-clinical pharmacokinetic study of ibuprofen and other non-steroidal anti-inflammatory drugs. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 10 October 2011 | 8:05 am

Tunable fluorescent pH sensor based on water-soluble perylene tetracarboxylic acid/Fe3+

A novel fluorescent pH sensor with tunable response range was designed based on highly fluorescent 3,4:9,10-perylene tetracarboxylic ammonium, which could coordinate the paramagnetic Fe3+ ions to turn off its fluorescence and could also release Fe3+ to turn on the fluorescence again at higher pH. The fluorescent pH sensor was tunable in the presence of different ligands in aqueous solution. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 10 October 2011 | 8:03 am

A highly sensitive and temporal visualization system for gaseous ethanol with chemiluminescence enhancer

A two-dimensional gaseous ethanol visualization system has been developed and demonstrated using a horseradish peroxidase–luminol–hydrogen peroxide system with high-purity luminol solution and a chemiluminescence (CL) enhancer. This system measures ethanol concentrations as intensities of CL via the luminol reaction. CL was emitted when the gaseous ethanol was injected onto an enzyme-immobilized membrane, which was employed as a screen for two-dimensional gas visualization. The average intensity of CL on the substrate was linearly related to the concentration of standard ethanol gas. These results were compared with the CL intensity of the CCD camera recording image in the visualization system. This system is available for gas components not only for spatial but also for temporal analysis in real time. A high-purity sodium salt HG solution (L-HG) instead of standard luminol solution and an enhancer, eosin Y (EY) solution, were adapted for improvement of CL intensity of the system. The visualization of gaseous ethanol was achieved at a detection limit of 3?ppm at optimized concentrations of L-HG solution and EY. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 5 October 2011 | 6:08 pm

Lyoluminescence, thermoluminescence and mechanoluminescence studies in ?-ray irradiated Dy3+ activated potassium chloride phosphor for accidental radiation dosimetry

The lyoluminescence (LL), thermoluminescence (TL) and mechanoluminescence (ML) of ?-ray-irradiated coloured powder of KCl:Dy (0.05–0.5?mol%) phosphors are reported in this paper. To understand the mechanism of LL and ML, the LL and ML spectra are compared with TL studies. The variation of intensity of respective luminescence with different ?-ray doses and with different concentrations of Dy3+ ion doped in KCl is found to be similar in nature. The intensities differ from each other, but their nature is found to be similar with ?-ray exposures. The ML glow peak intensity is linear up to high 1?kGy exposure as compared to LL (up to 0.5?kGy) and TL (up to 0.75?kGy) techniques. Therefore, according to our results, the recommendation is that KCl:Dy (0.1?mol%) phosphor prepared by wet chemical technique is useful for high-dose measurements using the ML technique for accidental radiation dosimetry. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 5 October 2011 | 6:08 pm

Thermal luminescence spectra of polyamides and their Maillard reaction with reducing sugars

Thermal luminescence (TL) spectra of polyamides were measured with a Fourier-transform chemiluminescence spectrometer to elucidate the emission mechanism. A TL band of ?-polylysine with a peak at 542?nm observed at 403?K was assigned to the emission due to the interaction of the –CO–NH– group with oxygen molecules by comparison with nylon-6, polyglycine, and polyalanine. When the sample was kept at 453?K, the intensity of the TL band decreased and the wavelength of the peak shifted to 602?nm, which was assigned to the emission due to the interaction of the NH2 group on the side chain with oxygen molecules by comparison with monomeric lysine. A weak emission with a peak at 668?nm was assigned to the advanced glycosylation end products (AGEs) yielded by the Maillard reaction with a catalytic amount of water. To understand this reaction and to examine the TL emission of AGEs, we measured TL spectra of mixtures of polylysine and reducing sugars such as glucose, maltose, lactose, and dextrin. The minimum temperature for TL emission, wavelength of the peak and the relative intensities of the TL emission were found to depend on the size of the sugars. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 5 October 2011 | 6:07 pm

Determination of bismuth in pharmaceutical products using phosphoric acid as molecular probe by resonance light scattering

A novel method for the sensitive determination of bismuth(III) in pharmaceutical products using phosphoric acid as a molecular probe by resonance light scattering (RLS) is discussed. In 0.5?mol/L phosphoric acid (H3PO4) medium, bismuth(III) reacted with PO43? to form an ion association compound, which resulted in the significant enhancement of RLS intensity and the appearance of the corresponding RLS spectral characteristics. The maximum scattering peak of the system existed at 364?nm. Under optimal conditions, there was linear relationship between the relative intensity of RLS and concentration of bismuth(III) in the range of 0.06–10.0?µg/mL for the system. A low detection limit for bismuth(III) of 3.22?ng/mL was achieved. The relative standard deviations (RSD) for the determination of 0.40 and 0.80?µg/mL bismuth(III) were 2.1% and 1.1%, respectively, for five determinations. Based on this fact, a simple, rapid, and sensitive method was developed for the determination of bismuth(III) at nanogram level by RLS technique with a common spectrofluorimeter. This analytical system was successfully applied to determine the trace amounts of bismuth(III) in pharmaceutical products, which was in good agreement with the results obtained by atomic absorption spectrometry (AAS). Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 23 September 2011 | 2:43 pm

Spectroscopic investigations of Er3+:CdO–Bi2O3–B2O3 glasses

This article reports on the optical properties of Er3+ ions doped CdO–Bi2O3–B2O3 (CdBiB) glasses. The materials were characterized by optical absorption and emission spectra. By using Judd–Ofelt theory, the intensity parameters ?? (??=?2, 4, 6) and also oscillatory strengths were calculated from the absorption spectra. The results were used to compute the radiative properties of Er3+:CdBiB glasses. The concentration quenching and energy transfer from Yb3+–Er3+ were explained. The stimulated emission cross-section, full width at half maximum (FWHM) and FWHM?×??pE values are also calculated for all the Er3+:CdBiB glasses. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 19 September 2011 | 4:00 pm

Selective signaling of fluoride anion based on imidazole moieties

The imidazole ring unit in both 2-(2?-hydroxyphenyl)-benzimidazole (ligand a) and a europium(III) complex exhibited specific luminescent responses in the presence of fluoride anions. UV-visible and 1H-nuclear magnetic resonance spectra showed that the NH bond of the imidazole ring can form a hydrogen bond with added fluoride anions. The detection limits are 5?×?10?6?m for organic ligand and 1.0?×?10?6?m for the europium complex respectively. The response times are less than 3?s. The europium complex exhibits a linear response in a concentration range lower than 1.0?×?10?6?m (Y?=??666.86X?+?730.1). Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 14 September 2011 | 10:49 am

Detection of hydrogen sulphide using cataluminescence sensors based on alkaline-earth metal salts

Detection of hydrogen sulphide (H2S) was conducted based on cataluminescence (CTL) sensors, using alkaline-earth metal carbonates as catalysts. Optimal working conditions, analytical characteristics and the response properties of the sensor were investigated. CTL intensity examination showed that sensors fabricated with CaCO3, SrCO3 or BaCO3 could be used to detect H2S gas sensitively. The optimal sensing temperature was about 320?°C. Under the sensing conditions with temperature at ca. 320?°C and gas flow rate in the range 180–200?mL/min, the linear range of CTL intensity vs H2S concentration was 25–500?ppm, with a detection limit of 2?ppm. The response and recovery times of the sensor were within 5 and 25?min, respectively. Also, the sensor had the property of high selectivity to H2S with very weak or no obvious response to 14 other gases, such as NO2, NH3, hydrocarbons and alcohol. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 8 September 2011 | 4:54 pm

Synthesis and properties of a new red luminescence europium complex containing a 2-(benzimidazol-2-yl)-8-octyloxyquinoline as the second ligand

A new Eu(III) complex, Eu(III)(DBM)3BIOQ, has been synthesized with dibenzoylmethane (DBM) as the first ligand and 2-(benzimidazol-2-yl)-8-octyloxyquinoline (BIOQ) as the second ligand. The stability of the complex was analysed by DSC–TG. The results show that the Eu(III) complex has a relatively high thermal stability with a melting point of 235?°C and a decomposition temperature (onset) of 252?°C. The fluorescence properties of the compound were also investigated. The fluorescence results reveal that the as-prepared complex shows the characteristic maximum emission spectra of Eu(III) at 611?nm (?ex?=?350?nm). In addition, the photoluminescence spectrum of the complex in the solid state exhibits a single and symmetrical emission band at 611?nm, with a full width at half-maximum of 4.7?nm, showing high colour purity. This finding indicates the possibility for the development of brighter red luminescent materials. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 7 September 2011 | 11:12 am

The fluorescence of Mg–Al–Eu ternary layered hydroxides response to tryptophan

We have studied the fluorescence of Mg–Al–Eu ternary layered hydroxides (TLH) quenched by tryptophan (Trp). IR spectroscopy was used to evaluate the change of Trp structure which was caused by TLH. XRD and TG–DTA results further suggested a structural change of Trp after being reacted with TLH. XPS characterization confirmed a strong chemical reaction between Trp and TLH. These studies may present more direct evidence to explain the interrelation between the structural change of Trp and the fluorescent quenching of TLH. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 September 2011 | 6:12 am

A novel chemiluminescence system for the determination of daidzein and its hydroxyl radical-scavenging capacity

A novel chemiluminescence (CL) system was established for the determinations of daidzein in pharmaceutical preparations and to assess its ability to scavenge hydroxyl radicals. It was shown that a strong CL signal generated when eosin Y was mixed with Fenton reagent was decreased significantly when daidzein was added to the reaction system due to partial scavenging of the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometric relationship with the daidzein concentration. Based on this, we developed a new method for the determination of daidzein, using a flow-injection chemiluminescence (FI–CL) technique. Under the optimal conditions, the linear range of daidzein concentration was 8.0?×?10–8–3.0?×?10–6?mol/L (R?=?0.9982), with a detection limit of 9.0?×?10–9?mol/L (S:N?=?3), and the RSD was 5.8% for 1.0?×?10–6?mol/L daidzein (n?=?11). This method was successfully used in the determination of daidzein in tablets and for evaluation of the hydroxyl radical-scavenging capacity of daidzein. The possible reaction mechanism of the CL system is discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 September 2011 | 5:18 am

Spectroscopic investigations to reveal the nature of interactions between the haem protein myoglobin and the dye rhodamine 6G

In the present investigation, steady-state and time-resolved fluorescence with the combination of circular dichroism (CD) spectroscopic techniques were applied to study the interactions of the well-known dye rhodamine 6?G (R6G) with the haem protein human myoglobin (Mb). From the analysis of the results it appears that the static type of fluorescence quenching mechanism is primarily involved, due to ground-state interactions. Although considerable overlapping of fluorescence emission of the dye R6G with the absorption of Mb in the Q-band region exists, the possibility of occurrences of the excitational singlet–singlet non-radiative energy transfer process from R6G to Mb appears to be unlikely, according to time-resolved fluorescence measurements. From the determinations of the thermodynamic parameters, it was apparent that the combined effect of van der Waals' interactions and hydrogen bonding plays a vital role in Mb–R6G interactions. Induced circular dichroism (ICD) studies demonstrate the possibility of interactions between R6G and Mb. The binding constants, number of binding sites and thermodynamic parameters have been computed. From CD measurements it is apparent that the binding of the dye R6G with the haem protein Mb induces negligible conformational changes in the protein and Mb retains its secondary structure and helicity when it interacts with R6G. The present detailed studies on the interactions with Mb should be helpful in further advancement of medical diagnostics and biotechnology. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 23 August 2011 | 2:35 pm

Evaluation of the antioxidant activity of tetracycline antibiotics in vitro

Tetracyclines are the second most common antibiotic family in medicine usage. These antibiotics exhibit antioxidant potential; however, the exact mechanism remains unclear. The antiradical activity of the seven tetracyclines (TCs; tetracycline, chlortetracycline, oxytetracycline, doxocycline, methacycline, demeclocycline, minocycline) was determined using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and hydroxyl radicals (HO•) generated in a Fenton reaction. Electron spin resonance (ESR), ESR spin-trapping, chemiluminescence and spectrophotometry techniques were applied. It was found that the TCs showed high DPPH antiradical activity in the range 26–96% at 2.5?mmol/L concentration. The second-order rate constants for the reaction between HO• and TCs were calculated, in the range (3.6–9.6) × 109?L/mol/s. The tetracycline compounds also exhibited a strong decrease in light emission (range 61–85% at concentration of 1?mmol/L). This study also showed that TCs promote the generation of singlet oxygen in the presence of H2O2• and Fe(II)/Fe(III) ions. Our findings suggest direct scavenging activity of the examined tetracyclines towards free radicals, and may be relevant to therapeutic strategy. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 23 August 2011 | 2:35 pm

Determination of deferiprone in urine and serum using a terbium-sensitized luminescence method

Optimized conditions, validation and practical applications of a new, rapid and specific fluorometric method for the determination of deferiprone (DFP) in urine and serum samples are reported. The proposed method, which is based on the formation of a luminescent complex with Tb3+ ion, is evaluated in terms of linearity, accuracy, precision, stability, recovery and limits of detection (LOD) and quantification (LOQ). Under optimum conditions (pH 7.5, [Tb3+]?=?3?×?10–4?mol/L, temperature 0?°C and excitation wavelength 295?nm), the relative intensities at 545?nm are linear, with the concentration of DFP in the range 0.072–13?mmol/L for urine and serum samples. The LOD and LOQ, respectively, are calculated to be 0.014 and 0.045?mmol/L for urine and 0.022 and 0.072?mmol/L for serum samples. The intra-day and inter-day values for the precision and accuracy of the proposed method are all < 5%, and the recovery of the method is in the range 97.1–103.8%. The method was applied to human urine and serum samples collected from patients receiving DFP. The results indicated that the method can be successfully applied to the determination of DFP in human urine and serum samples collected for clinical or biopharmaceutical investigations in which simple, rapid, cheap and specific determination methods facilitate and speed up the analytical procedure. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 19 August 2011 | 5:51 am

Highly sensitive chemiluminescence determination of tenoxicam using a cerium(IV)–sodium hyposulphite system in micellar medium

A simple, rapid and precise flow-injection–chemiluminescence (FI–CL) method is presented for the determination of tenoxicam in pharmaceutical preparations and biological samples. The method is based on the weak chemiluminescence signal arising from the reaction of cerium(IV) in a nitric acid medium with sodium hyposulphite being significantly increased by tenoxicam in the presence of sodium dodecyl benzene sulphonate. Several experimental parameters affecting the CL reaction were examined and optimized systematically. Under the optimum conditions, the CL intensity was proportional to the concentration of tenoxicam in the range 7.0?×?10–11–5.0?×?10–8?g/mL. The detection limit was 2.3?×?10–11?g/mL tenoxicam and the relative standard deviation (RSD) was 2.1% for 1.0?×?10–9?g/mL tenoxicam solution (n?=?11). The proposed method was applied to the determination of tenoxicam in pharmaceutical preparations, serum and human urine, with satisfactory results. The possible mechanism of the chemiluminescence reaction is also briefly discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 16 August 2011 | 3:42 pm

Enhancing and inhibiting effects of benzenediols on chemiluminescence of a novel cyclometallated iridium(III) complex

A novel chemiluminescence (CL) system, including the cyclometallated iridium(III) complex {tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium}, potassium permanganate and oxalic acid, is proposed for the determination of benzenediols. This method is based on the fact that hydroquinone and catechol exhibited an inhibiting effect, while resorcinol exhibited an enhancing effect on CL intensity. The optimum conditions for CL emission were investigated. Under optimal conditions, the detection limits of hydroquinone, catechol and resorcinol were 6.4?×?10?8, 2.7?×?10?9 and 8.1?×?10?7?mol/L, respectively. The method has been successfully applied to the determination of benzenediols in different types of water sample. The luminophors of the CL systems were all identified as the metal–ligand charge-transfer (MLCT) excited state of the iridium complex. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 12 August 2011 | 3:27 pm

Flow-injection chemiluminescence determination of melamine in urine and plasma

A novel flow-injection chemiluminescence method for the determination of melamine in urine and plasma was developed. It was found that melamine can remarkably enhance chemiluminescence emission from the luminol–K3Fe(CN)6 system in an alkaline medium. Under the optimum conditions, chemiluminescence intensity had a good linear relationship with the concentration of melamine in the range 9.0?×?10–9–7.0?×?10–6?g/mL, with a correlation coefficient of 0.9992. The detection limit (3?) was 3.5?ng/mL. The method has been applied to determine the concentration of melamine in samples using liquid–liquid extraction. Average recoveries of melamine were 102.6% in urine samples and 95.1% in plasma samples. The method provided a reproducible and stable approach for the sensitive detection of melamine in urine and plasma samples. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 9 August 2011 | 2:14 pm

Enhanced chemiluminescence of the luminol–AgNO3 system by Ag nanoparticles

The oxidation reaction of luminol with AgNO3 can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV-vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol–AgNO3–Ag NPs system indicated that the luminophore was still 3-aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO3, they catalysed the reduction of AgNO3 by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol–AgNO3–Ag NPs CL system were studied by a flow-injection procedure, which led to an effective method for detecting these compounds. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 1 August 2011 | 2:11 pm

Post-chemiluminescence determination of chloramphenicol based on luminol–potassium periodate system

A post-chemiluminescence (PCL) phenomenon was observed when chloramphenicol was injected into a mixture of luminol and potassium periodate after the chemiluminescence (CL) reaction of luminol–potassium periodate had finished. The possible reaction mechanism was proposed based on studies of the CL kinetic characteristics, the CL spectra, the fluorescence spectra and the UV-vis absorption spectra of the related substances. Based on the PCL reaction, a rapid and sensitive method for the determination of chloramphenicol was established. The linear response range was 6.0?×?10?7–1.0?×?10?5?mol/L, with a correlation coefficient of 0.9986. The relative standard deviation (RSD) for 5.0?×?10?6?mol/L chloramphenicol was 2.3% (n?=?11). The detection limit was 1.6?×?10?7?mol/L. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 20 July 2011 | 9:37 am

Fluorescence spectroscopic studies on the interaction of Gemini surfactant 14-6-14 with bovine serum albumin

The interaction of the cationic Gemini surfactant hexamethylene-1,3-bis (tetradecyldimethylammonium bromide) (14-6-14) with bovine serum albumin (BSA) has been investigated by fluorescence quenching spectra and three-dimensional (3D) fluorescence spectra. The Stern–Volmer quenching constants KSV and the corresponding thermodynamic parameters ?H, ?G and ?S have been estimated by the fluorescence quenching method. The results indicated that hydrophobic forces were the predominant intermolecular forces between BSA and the surfactant. Competitive experiments and the number of binding sites calculation show that 14-6-14 can be inserted in site-II (in subdomain IIIA) of BSA. The effect of 14-6-14 on the conformation of BSA was evaluated by synchronous fluorescence spectroscopy and 3D fluorescence spectral methods. The results show that the conformation of BSA was changed dramatically in the presence of 14-6-14, by binding to the Trp and Try residues of BSA. The investigation provides interaction between BSA and 14-6-14 as a model for molecular design and industrial research. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 14 July 2011 | 10:16 am

Synthesis of novel taspine diphenyl derivatives as fluorescence probes and inhibitors of breast cancer cell proliferation

Two novel taspine diphenyl derivatives (Ta-dD) were designed and synthesized by introducing different coumarin fluorescent groups into the basic structure of Ta-dD. The main advantage of these two compounds is that they can be used as fluorescence probes and inhibitors simultaneously. In the present study, the fluorescent properties of the probes were measured and their inhibition of four breast cancer cell lines was tested. Different concentrations of the fluorescence probe were added to MCF-7 breast cancer cells for fluorescence imaging analysis under normal conditions. The results suggested that both of the new compounds have not only fluorescence but also the ability to inhibit effects on different breast cancer cell lines, which indicates their possible further use as dual functional fluorescence probes in tracer analysis. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 14 July 2011 | 10:16 am

Determination of 5-hydroxytryptamine in serum by electrochemiluminescence detection with the aid of capillary electrophoresis

A rapid, sensitive and simple electrochemiluminescence method for the determination of 5-hydroxytryptamine (5-HT) using capillary electrophoresis was proposed. The experimental parameters, including the detection potential, the concentration of Ru(bpy)32+, the concentration and pH of phosphate buffer for separation and detection, the injection voltage and time and the separation voltage on the determination of 5-HT, were optimized. Under the optimized conditions, the linear concentration range for 5-HT was 3.5 × 10-9–5.1 × 10-3 mol/L, with a detection limit of 5 × 10-10 mol/L. The relative standard deviations (RSDs) of the ECL intensity and the migration times for six continuous injections of 1.0?µmol/L 5-HT were 2.48% and 1.3%, respectively. The method was successfully applied to 5-HT assay in samples of human serum in 5?min and the extraction recoveries with spiked serum samples were over 94.4%. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 11 July 2011 | 10:36 am

Highly sensitive spectrofluorimetic determination of rutin based on its activated effect on a multi-enzyme redox system

A highly sensitive and simple spectrofluorimetric method for the determination of rutin, based on its activated effect on a haemoglobin-catalysed reaction, was developed. Under optimum conditions, the concentration of rutin was linear, with decreased fluorescence (?F) of the system under optimal experimental conditions. The calibration graph was linear in the range 1.0?×?10–7–3.0?×?10–5?mol/L, with a detection limit of 7.0?×?10–8?mol/L. The relative standard deviation (RSD) was 3.26% for 11 determinations of 1.0?×?10–5?mol/L. This method was used for the determination of rutin in pharmaceuticals with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 11 July 2011 | 10:34 am

Photoluminescence in rare earth-doped complex hexafluoride phosphors

In this study, using a simple combustion process and a wet chemical process, fluorides showing intense photoluminescence were prepared and developed as low-cost phosphors. The prepared phosphors were characterized by photoluminescence (PL) techniques. PL emission spectra of the phosphor suggest the presence of Eu3+ as well as Eu2+ ions in LiMgBF6:Eu and Li2NaBF6:Eu lattice sites. This article summarizes the fundamentals and possible applications of optically useful inorganic fluoride with visible photoluminescence of doped Eu3+ and Eu2+ ions. Our results on LiMgBF6:Ce and Li2NaBF6:Ce are also reported. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 8 July 2011 | 6:02 am

A highly selective fluorescent probe for pyrophosphate detection in aqueous solutions

A novel and simple fluorescence enhancement method is introduced for selective pyrophosphate (PPi) sensing in an aqueous solution. The method is based on a 1:1 metal complex formation between tris(8-hydroxyquinoline-5-sulphonate) thulium(III) [Tm(QS)3] and PPi ion. The linear response covers a concentration range of 1.6?×?10?7–1.0?×?10?5?mol/L PPi and the detection limit is 2.3?×?10?8?mol/L. The association constant of Tm(QS)3–PPi complex was calculated as 2.6?×?105?mol/L. Tm(QS)3 shows a selective and sensitive fluorescence enhancement toward PPi ion in comparion with I3?, NO3?, CN?, CO32?, Br?, Cl?, F?, H2PO4? and SO42?, which is attributed to higher stability of the inorganic complex between pyrophosphate ion and Tm(QS)3. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 7 July 2011 | 9:32 am

Multifunctional organic–inorganic composite luminescent nanospheres

A simple general strategy was successfully developed for the preparation of magnetic–luminescent multifunctional nanocomposites by incorporating fluorescent (pyrene) and magnetic (Fe3O4) components simultaneously into a poly(styrene-co-methacrylic acid) [poly(St-co-MAA)] copolymer matrix. The nanospheres so prepared were characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The prepared magnetic–fluorescent inorganic–organic nanocomposites have excellent magnetic and photoluminescent properties. They can be used in magnetic separation of trace amounts of sample, fluorescence detection and imaging applications, including magnetic resonance imaging (MRI) and fluorescence imaging. The fluorescence quenching of the nanospheres in the presence of different amounts of Cu2+ ions was also investigated. Under optimal experimental conditions, the relative fluorescence intensity of the composite nanosphere colloidal solution is proportional to the concentration of Cu2+ ions, which indicates that these multifunctional nanocomposites can be used for the magnetic separation and fluorescence detection of Cu2+ ions. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 28 June 2011 | 8:20 am

Serum inverts and improves the fluorescence response of an aptamer beacon to various vitamin D analytes

A dominant aptamer loop structure from a library of nearly 100 candidate aptamer sequences developed against immobilized 25-hydroxyvitamin D3 (calcidiol) was converted into a 5?-TYE 665 and 3?-Iowa black-labelled aptamer beacon. The aptamer beacon exhibited a mild 'lights on' reaction in buffer as a function of increasing concentrations of several vitamin D analogues and metabolites, with a limit of detection of approximately 200?ng/mL, and was not specific for any particular congener. In 10% or 50% human serum, the same aptamer beacon inverted its fluorescence behaviour to become a more intense 'lights off' reaction with an improved limit of detection in the range 4–16?ng/mL. We hypothesized that this drastic change in fluorescence behaviour was due to the presence of creatinine and urea in serum, which might destabilize the quenched beacon, causing an increase in fluorescence followed by decreasing fluorescence as a function of vitamin D concentrations that may bind and quench increasingly greater fractions of the denatured beacons. However, the results of several control experiments in the presence of physiological or greater concentrations of creatinine and urea, alone or combined in buffer, failed to produce the beacon fluorescence inversion. Other possible mechanistic hypotheses are also discussed. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 28 June 2011 | 8:18 am

Determination of diethylstilbestrol based on biotin–streptavidin-amplified time-resolved fluoro-immunoassay

A rapid and sensitive time-resolved fluoroimmunoassay (TR–FIA) based on the biotin–streptavidin amplification system was developed for the determination of diethylstilbestrol (DES). Europium-labelled streptavidin derivatives combined with europium and anhydride of diethylene triamine penta-acetic acid were used to label streptavidin; biotin was coupled with goat anti-rabbit IgG to form a biotin–goat anti-rabbit IgG bridge between streptavidin–europium and the anti-DES antibody in the immunoassay. The DES assay was carried out by measuring the fluorescence of Eu3+–SA at 615?nm. The presented method produced a wide linear range, 0.001–1000.0?ng/mL, and a detection limit up to 0.81?pg/mL for DES. The method was applied to determine DES in serum samples, with recoveries of 97.4–107.8% and RSD 1.32–4.04%. The assay results by the present method showed that biotin–streptavidin amplified TR–FIA for DES detection; it may offer high sensitivity and promising alternative special methods in biological samples. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 22 June 2011 | 8:05 am

Water-soluble mercaptoundecanoic acid (MUA)-coated CdTe quantum dots: one-step microwave synthesis, characterization and cancer cell imaging

ABSTRACT: In this study, a one-step approach for aqueous synthesis of highly luminescent semiconductors, CdTe quantum dots (QDs), using long-chain thiols-mercaptoundecanoic acid (MUA) as surface ligand, was developed in a microwave irradiation system. The synthetic conditions were systematically investigated. The as-prepared MUA-coated QDs were characterized by various spectroscopy techniques, transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The experimental results document that MUA-coated CdTe QDs have small diameter, good stability, high luminescence and long lifetime. Particularly, it was confirmed, using fluorescence correlation spectroscopy (FCS) that, compared with other ligand, MUA formed a thicker ligand layer on the QD surfaces, which will help their stability and conjugation with biomolecules. Furthermore, MUA-coated QDs were successfully used for HeLa cell imaging. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 21 June 2011 | 11:53 am

A terbium-sensitized spectrofluorimetric method for determination of catecholamines in a serum sample with micelle medium

A terbium-sensitized spectrofluorimetric method has been developed for determination of catecholamines such as norepinephrine (NE), epinephrine (EP) and dopamine (DA), using sodium dodecyl benzene sulphonate (SDBS). Fluorescence sensitization of terbium ions (Tb3+) by complexation with catecholamines in the presence of SDBS was observed. The fluorescence intensities of the Tb3+–catecholamine complexes were highly enhanced by introducing SDBS with an emission maximum at 545?nm after excitation at 290?nm. The conditions for the complex formation of Tb3+–catecholamine were investigated systematically and optimized to determine catecholamines in a serum sample. Under the optimum conditions, the fluorescence intensities of the Tb3+–catecholamine complexes were increased linearly with the concentration of NE, EP and DA over the ranges 2.5?×?10–10–1.0?×?10–8, 2.5?×?10–10–1.0?×?10–8 and 2.5?×?10–9–1.0?×?10–7?g/mL with correlation coefficients of 0.999, 0.999 and 0.9996, respectively. The limits of detection (3?) of NE, EP and DA were found to be 4.6?×?10–11, 7.8?×?10–11 and 8.38?×?10–10?g/mL, respectively. Precision of the method was tested at the concentration level of 1.2?×?10?7?g/mL for five replicate measurements of NE, EP and DA, giving relative standard deviations (RSDs) of 1.41%, 1.23% and 1.89%, respectively. The interaction mechanism of the Tb3+–catecholamine complexes system was investigated and presented with ultraviolet absorption spectra. The proposed method has been applied for the quantitative determination of NE, EP and DA in a spiked serum sample and a pharmaceutical preparation sample. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 21 June 2011 | 11:47 am

5d–4f transition in new phosphate-based phosphors

The preparation of Ce3+-doped Sr6AlP5O20 and Ba6AlP5O20 by a combustion method is described. Formation of compounds was confirmed by X-ray diffraction (XRD) analysis. The photoluminescence (PL) emission spectra were observed at 355?nm when excited at 307?nm for the various concentrations. The PL emission spectra of phosphors showed strong Ce3+ emission due to the 5?d???4f transition of Ce3+ ions. The Ce3+ emission intensity in Sr6AlP5O20:Ce phosphor was higher than that in Ba6AlP5O20:Ce and it may be useful for scintillation applications. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 21 June 2011 | 10:54 am

Spectrofluorimetric determination of nomifensine in human plasma and urine by derivatization with fluorescamine

A sensitive, simple and rapid spectrofluorimetric method was developed for the determination of nomifensine in human plasma and urine. The present method was based on the derivatization by fluorescamine in phosphate buffer at pH 4.0 to produce a highly fluorescent product which was measured at 488?nm (excitation at 339?nm). The method was validated according to the ICH guidelines with respect to linearity, limit of detection, limit of quantification, accuracy, precision, recovery and robustness. The assay was linear over the concentration ranges 100–2,000 and 50–2,000?ng/mL for plasma and urine, respectively. The limits of detection were calculated to be 13.9 and 7.5?ng/mL for plasma and urine, respectively. The method was successfully applied to the analysis of the drug in human plasma and urine. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 17 June 2011 | 9:23 am

Determination of dipyrone in pharmaceutical preparations based on the chemiluminescent reaction of the quinolinic hydrazide–H2O2–vanadium(IV) system and flow-injection analysis

A rapid, economic and sensitive chemiluminescent method involving flow-injection analysis was developed for the determination of dipyrone in pharmaceutical preparations. The method is based on the chemiluminescent reaction between quinolinic hydrazide and hydrogen peroxide in a strongly alkaline medium, in which vanadium(IV) acts as a catalyst. Principal chemical and physical variables involved in the flow-injection system were optimized using a modified simplex method. The variations in the quantum yield observed when dipyrone was present in the reaction medium were used to determine the concentration of this compound. The proposed method requires no preconcentration steps and reliably quantifies dipyrone over the linear range 1–50?µg/mL. In addition, a sample throughput of 85 samples/h is possible. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 16 June 2011 | 9:23 am

Wet-chemical preparation of Ce3+-activated K2LaX5 (X?=?Cl, Br or I) phosphors

There has been a renewed interest in Ce3+-activated halide phosphors due to applications as scintillation detectors, especially for positron emission tomography. For K2LaCl5, the light yield increases and the energy resolution (FWHM) improves with increasing Ce3+ doping. K2LaX5 compounds are also important as laser hosts for the mid-IR range. K2LaCl5:Nd crystals show bright mid-IR luminescence, which makes them a candidate for IR laser materials. Efficient emission in the IR range has also been reported in K2LaCl5:U3+. A one-step, wet chemical process for preparing Ce3+-activated K2LaCl5 phosphor is described. Intense luminescence of Ce3+ can be observed in the as-prepared powders without any heat treatment. The availability of such powders opens up several exciting possibilities, such as growing single crystals without going to the high temperatures required for melting the constituent chlorides, or even obtaining processed, transparent, Ce3+-activated materials without taking recourse to crystal growth. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 14 June 2011 | 1:17 pm

ATP bioluminescence rapid detection of total viable count in soy sauce

The adenosine triphosphate (ATP) bioluminescence rapid determination method may be useful for enumerating the total viable count (TVC) in soy sauce, as it has been previously used in food and beverages for sanitation with good precision. However, many factors interfere with the correlation between total aerobic plate counts and ATP bioluminescence. This study investigated these interfering factors, including ingredients of soy sauce and bacteria at different physiological stages. Using the ATP bioluminescence method, TVC was obtained within 4 h, compared to 48 h required for the conventional aerobic plate count (APC) method. Our results also indicated a high correlation coefficient (r?=?0.90) between total aerobic plate counts and ATP bioluminescence after filtration and resuscitation with special medium. The limit of quantification of the novel detection method is 100 CFU/mL; there is a good linear correlation between the bioluminescence intensity and TVC in soy sauce in the range 1?×?102–3?×?104 CFU/mL and even wider. The method employed a luminescence recorder (Tristar LB-941) and 96-well plates and could analyse 50–100 samples simultaneously at low cost. In this study, we evaluated and eliminated the interfering factors and made the ATP bioluminescence rapid method available for enumerating TVC in soy sauce. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 14 June 2011 | 1:17 pm

Luminescence in Li2Sr2Al2PO4F9:Dy3+ - a novel nanophosphor

Earlier research has revealed numerous advantages of the wet chemical method in reaction acceleration, yield improvement, enhanced photoluminescence properties and the evolution of new material phases. In the present study the novel nanophosphor Li2Sr2Al2PO4F9:Dy3+ was synthesized by a one-step wet chemical method. Formation of single-phase compounds was confirmed by X-ray diffraction (XRD) and characterized by photoluminescence (PL) and transmission electron microscopy (TEM) techniques. The average diameter of the particles was calculated from the TEM image as ca. 20?nm. The synthesized nanophosphor exhibited intense blue and yellow emissions at 482 and 575?nm, respectively, owing to the Dy3+ ion, by Hg-free excitation at 387?nm, i.e. solid-state lighting excitation. The results obtained showed that phosphors have the potential for applications in the lamp industry. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 8 June 2011 | 10:21 am

Luminescence properties of a nanoporous freshwater diatom

Freshwater diatom frustules show special optical properties. In this paper we observed luminescence properties of the freshwater diatom Cyclotella meneghiniana. To confirm the morphological properties we present scanning electron microscopy (SEM) images. X-ray diffraction (XRD) studies were carried out to visualize the structural properties of the frustules, confirming that silica present in diatom frustules crystallizes in an ?-quartz structure. Study of the optical properties of the silica frustules of diatoms using ultra-violet-visible (UV-vis) spectroscopy and photoluminescence spectroscopy confirmed that the diatom C. meneghiniana shows luminescence in the blue region of the electromagnetic spectrum when irradiated with UV light. This property of diatoms can be exploited to obtain many applications in day-to-day life. Also, using time-resolved photoluminescence spectroscopy (TRPL) it was confirmed that this species of diatom shows bi-exponential decay. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 27 May 2011 | 8:38 am

Effect of amino acids on aggregation behaviour of sodium deoxycholate in solution: a fluorescence study

The influence of three alkaline amino acids, l-lysine (L-Lys), l-arginine (L-Arg) and l-histidine (L-His), on the aggregation behaviour of sodium deoxycholate (NaDC) in phosphate buffer, pH 7.0, was studied at 25?°C. The fluorescence probe technique based on pyrene was employed to determine accurately the critical aggregation concentration (cac), polarity of the microenvironment and aggregation numbers for the NaDC aggregates. The added amino acids can effectively reduce the cac values and micropolarity of NaDC, indicating that it is easier for NaDC to aggregate in a compact manner in the presence of amino acids. The aggregation numbers of NaDC were increased, indicating that more NaDC molecules connect together to form stable aggregates. The performance of L-Arg is similar to that of L-His, and both have a smaller effect on the above parameters than L-Lys. In view of this, it may be inferred that both electrostatic and hydrophobic interaction are responsible for the interaction between NaDC and amino acids in aqueous solution. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 24 May 2011 | 10:17 am

Fluorescence modulation of 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione by silver nanoparticles and its possible analytical application

The effects of silver nanoparticles on the photophysical properties of 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, popularly known as curcumin, have been investigated using optical absorption and fluorescence techniques. Although absorption spectroscopy suggests a ground-state complex formation, fluorescence quenching data confirms a simultaneous static and dynamic quenching, inferring ground as well as excited-state complex formation. The recovery of fluorescence quenching of the curcumin–silver nanoparticle complex in the presence of ascorbic acid or uric acid emphasizes a strong interaction between the silver nanoparticles and ascorbic acid/uric acid, suggesting that fluorescence recovery after the quenching of curcumin–silver nanoparticle complexes has potential for ascorbic acid or uric acid assay development. Copyright © 2011 John Wiley & Sons, Ltd.

Posted on 24 May 2011 | 10:17 am