Current research reports and chronological list of recent articles.

Luminescence - The Journal of Biological and Chemical Luminescence - provides a forum for the publication of original scientific papers, short communications, technical notes and reviews on fundamental and applied aspects of all forms of luminescence, including bioluminescence, chemiluminescence, electrochemiluminescence, sonoluminescence, triboluminescence, fluorescence, time-resolved fluorescence and phosphorescence.

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Additional research articles see Current Chemistry Research Articles. General information about this topic see bioluminescence.

Luminescence - Abstracts

Simeprevir oxidative degradation product: Molecular modeling, in silico toxicity and resolution by synchronous spectrofluorimetry

In this article, one of the potential degradation products of the novel antiviral drug simeprevir was isolated and characterized by means of infrared (IR) and mass spectrometry. Moreover, comparative molecular docking, ADMET (absorption, distribution, metabolism, excretion – toxicity) and insilico toxicity prediction studies were applied to evaluate the activity of simeprevir and its degradation product. Furthermore,a simple, accurate and selective second derivative synchronous spectrofluorimetric method was developed for the determination of simeprevir in the presence of its oxidative degradation product.The synchronous fluorescence spectra of both compounds were measured in ethanol at pH 2.0 usingΔλ of 140 nm and the peak amplitude of the second derivative spectra were measured at 442 nm. The method was rectilinear over the concentration range of 0.2 to 2.0 μg/ml and validated according to the ICH (International Conference on Harmonization) guidelines. Moreover, the method was statistically compared to the reverse-phase high-performance liquid chromatography (RP-HPLC) method and good results were obtained.
Datum: 10.11.2017

Utility of Cremophor RH 40 as a micellar improvement for spectrofluorimetric estimation of sorafenib in pure form, commercial preparation, and human plasma

An easy, quick, simple and accurate spectrofluorimetric method was recognized and validated for evaluation of sorafenib (SOR) in pure form and biologically in plasma. Cremophor RH 40 (Cr RH 40) used for enhancing the fluorescence activity of SOR in phosphate buffer (pH 7). Cr RH 40 improved the native fluorescence of SOR remarkably in water. The fluorescence spectrum of SOR was observed at 405 nm after excitation at 265 nm. The linearity appeared to be in the range of 5 to 600 ng ml−1 for pure and from 9 to 500 ng ml−1 for plasma using the protein precipitation (ppt) method while from 10 to 500 ng ml−1 for plasma using liquid–liquid extraction method. The precisions and the accuracy of the estimated method gave satisfactory results. The recommended method was effectively applied for determination of SOR in human plasma with high recovery values. The results of some compounds that are possibly found in plasma were studied. The proposed method was also focused on real volunteers and a drug dissolution test.
Datum: 10.11.2017

Enhancement effect on the chemiluminescence of acridinium esters under neutral conditions

Enhancement effect on the chemiluminescence of acridinium ester derivatives under neutral conditions was investigated. Additions of phenols did not enhance the chemiluminescence intensities of acridinium ester derivatives in the presence of horseradish peroxidase and hydrogen peroxide. Additions of cetyltrimethylammonium bromide apparently enhanced the chemiluminescence intensities of phenyl 10-methyl-10λ4-acridine-9-carboxylate derivatives with electron-withdrawing groups at the 4-position of the phenyl group. In particular, the chemiluminescence intensity of 4-(trifluoromethyl)phenyl 10-methyl-10λ4-acridine-9-carboxylate trifluoromethanesulfonate salt was 5.5 times stronger in the presence of cetyltrimethylammonium bromide than in its absence at pH 7. The chemiluminescence intensity of 3,4-dicyano-phenyl 10-methyl-10λ4-acridine-9-carboxylate trifluoromethanesulfonate salt was 46 times stronger in the presence of cetyltrimethylammonium bromide at pH 7 than in its absence at pH 10.
Datum: 08.11.2017

Spectroscopic determination of succinylcholine in dosage forms using eosin Y

Two simple and sensitive analytical assay methods using spectrophotometry and spectrofluorimetry techniques were developed for the estimation of succinylcholine chloride (SUC) in pharmaceutical preparations. The suggested methods are based on the formation of an ion pair complex formed between the drug and eosin Y spectrophotometrically (Method I), or the suppressive effect of succinylcholine on the native fluorescence property of eosin Y (Method II). The spectrophotometric method (Method I) involves measuring the absorbance of the complex between succinylcholine and eosin Y at 550 nm in Britton Robinson buffer of pH 3. However, the spectrofluorimetric method (Method II) involves measuring the quenching effect of the studied drug on the native fluorescence property of eosin Y at the same pH at 550 nm after excitation at 480 nm. The absorbance versus concentration of the drug is rectilinear over the range of 0.5 to 15 μg/ml. The formation constant was 3.5 × 104 and the Gibb's free energy change was −2.5 × 104 J/mol. In Method II, the relative fluorescence intensity was directly proportional to SUC concentration over the range of 0.05 to 1 μg/ml. The proposed methods allowed a successful application to the estimation of succinylcholine ampoules. An explanation of the reaction pathway was postulated.
Datum: 08.11.2017

A sensitive fluorescence quenching method for the detection of tartrazine with acriflavine in soft drinks

In this work, a simple, rapid, sensitive, selective spectrofluorimetric method was applied to detect tartrazine. The fluorescence of acriflavine could be efficiently quenched by tartrazine. The method manifested real time response as well as presented satisfied linear relationship to tartrazine. The linear response range of tartrazine (R2 = 0.9995) was from 0.056 to 5 μmol L−1. The detection limit (3σ/k) was 0.017 μmol L−1, indicating that this method could be applied to detect traces of tartrazine. The accuracy and precision of the method was further assured by recovery studies via a standard addition method, with percentage recoveries in the range of 96.0% to 103.0%. Moreover, a quenching mechanism was investigated systematically by the linear plots at varying temperatures based on the Stern–Volmer equation, fluorescence lifetime and UV–visible absorption spectra, all of which proved to be static quenching. This sensitive, selective assay possessed a great application prospect for the food industry owing to its simplicity and rapidity for the detection of tartrazine.
Datum: 02.11.2017

Fabrication of nitrogen- and phosphorous-doped carbon dots by the pyrolysis method for iodide and iron(III) sensing

A facile and novel strategy to synthesize nitrogen- and phosphorous-doped carbon dots (NPCDs) by single step pyrolysis method is described here. Citric acid is used as carbon source and di-ammonium hydrogen phosphate is used as both nitrogen and phosphorous sources, respectively. Through the extensive study on optical properties, morphology and chemical structures of the synthesized NPCDs, it is found that as-synthesized NPCDs exhibited good excitation-dependent luminescence property, spherical morphology and high stability. The obtained NPCDs are stable in aqueous medium and possess a quantum yield of 10.58%. In this work, a new assay method is developed to detect iodide ions using the synthesized NPCDs. Here, the inner filter effect is applied to detect the iodide ion and exhibited a wide linear response concentration range (10–60 μM) with a limit of detection (LOD) of 0.32 μM. Furthermore, the synthesized NPCDs are used for the selective detection of iron(III) (Fe3+) ions and cell imaging. Fe3+ ions sensing assay shows a detection range from 0.2 to 30 μM with a LOD of 72 nM. As an efficient photoluminescence sensor, the developed NPCDs have an excellent biocompatibility and low cytotoxicity, allowing Fe3+ ion detection in HeLa cells.
Datum: 02.11.2017

Comparison of the thermostability of recombinant luciferases from Brazilian bioluminescent beetles: Relationship with kinetics and bioluminescence colours

Firefly luciferases have been used extensively as bioanalytical reagents and their cDNAs as reporter genes for biosensors and bioimaging, but they are in general unstable at temperatures above 30°C. In the past few years, efforts have been made to stabilize some firefly luciferases for better application as analytical reagents. Novel luciferases from different beetle families, displaying distinct bioluminescence colours and kinetics, may offer desirable alternatives to extend the range of applications. In the past years, our group has cloned the largest variety of luciferases from the three main families of bioluminescent beetles (Elateridae: P. termitilluminans, F. bruchi, P. angustus; Phengodidae: P. hirtus, P. vivianii; and Lampyridae: A. vivianii, C. distinctus and Macrolampis sp2) occurring in Brazilian biomes. We compared the thermostability of these recombinant luciferases and investigated their relationships with bioluminescence spectra and kinetics. The most thermostable luciferases were those of Pyrearinus termitilluminans larval click beetle (534 nm), Amydetes vivianii firefly (539 nm) and Phrixotrix vivianii railroad worm (546 nm), which are the most blue-shifted examples in each family, confirming the trend that the most blue-shifted emitting luciferases are also the most thermostable. Comparatively, commercial P. pyralis firefly luciferase was less thermostable than P. termitilluminans click beetle and A. vivianii firefly luciferases. The higher thermostability in these luciferases could be related to higher degree of hydrophobic packing and disulfide bond content (for firefly luciferases).
Datum: 02.11.2017

A novel spectrofluorimetric method for determination of imatinib in pure, pharmaceutical preparation, human plasma, and human urine

The following paper represents a simple, highly sensitive, responsive validated and developed spectrofluorimetric method for estimation of imatinib (IMB) in its pure, commercial preparation, human urine and human blood plasma. The calibration curve was in the range 4–900 ng ml−1 for pure form and urine and 8–900 ng ml−1 for plasma in a medium contains carboxymethyl cellulose (CMC) and acetate buffer (pH 5) with excitation wavelength (λex) 230 nm and emission wavelength (λem) 307 nm. The limit of detection (LOD) was 0.37 ng ml−1 for the pure form, 0.64 ng ml−1 for human urine, and 0.70 ng ml−1 for human plasma, while the limit of quantitation (LOQ) was 1.2 for pure form, 1.91 for urine and 2.1 for plasma. The suggested method was successfully applied for evaluation of IMB in tablets within 99% mean percentage recovery. The excipients that are usually used as additives in pharmaceutical dosage form did not interfere with the suggested method. The method was efficiently used for estimation of IMB in human urine and human plasma. The effect of some cations that might be present in urine and plasma was also studied. The method was also focused on human volunteers and in vitro drug release.
Datum: 02.11.2017

Simultaneous determination of amlodipine and metoprolol in their combined dosage form using a synchronous fluorescence spectrofluorimetric method

Highly sensitive, rapid, accurate and precise synchronous fluorescence spectrofluorimetric method has been developed for simultaneous analysis of a mixture of amlodipine (AMD) and metoprolol (MET). The method relies on measuring the relative synchronous fluorescence intensity of both drugs at Δλ of 90 nm in acetate buffer solution at pH 5. The experimental parameters influencing the developed method were investigated and optimized. The method was linear over the ranges 0.2–2 μg/ml and 0.5–10 μg/ml for AMD and MET, respectively. The limits of detection were 50 ng/ml for AMD and 130 ng/ml for MET while the limits of quantitation were 150 ng/ml for AMD and 390 ng/ml for MET. The developed method was applied successfully for the determination of the two drugs in their co-formulated tablet. The mean percent recoveries were found to be 100.51 and 99.57 for AMD and MET, respectively.
Datum: 26.10.2017

Synthesis and characterization of KCe(PO3)4 doped with some lanthanide activators

KCe(PO3)4 doped with Dy3+,Tb3+,Yb3+and Nd3+ phosphors were synthesized by a solid state diffusion method. The prepared samples were characterized by X-ray diffraction and photoluminescence. KCe(PO3)4 exhibits emission in ultraviolet (UV) region which indicates weak Ce3+–Ce3+ interaction. The Ce3+–Ce3+energy transfer is not efficient. In light of this, energy transfer from Ce3+ to other lanthanides like Dy3+, Tb3+,Yb3+ and Nd3+ is rather surprising.
Datum: 26.10.2017

A carbonothioate-based highly selective fluorescent probe with a large Stokes shift for detection of Hg2+

Mercury (Hg) is one of the heavy metal pollutants in the environment. Even a very small amount of mercury can cause serious harm to human beings. Herein, we reported a new carbonothioate-based fluorescent probe for the detection of Hg2+ without interference from other metal ions. This probe possessed a very large Stokes shift (192 nm), which could improve the detection sensitivity by minimizing the interferences resulted from self-absorption or auto-fluorescence. With the addition of Hg2+ to the probe solution, considerable fluorescence enhancement was observed. Additionally, the Hg2+ concentration of 0–16 μM and fluorescence intensity showed a good linear relationship (y = 22106× + 53108, R2 = 0.9955). Finally, the proposed probe was used to detect Hg2+ in real water samples, and its result was satisfactory. Therefore, our proposed probe would provide a promising method for the determination of Hg2+ in the environment.
Datum: 25.10.2017

The determination of nitrite by a graphene quantum dot fluorescence quenching method without sample pretreatment

A method for quantitative analysis of nitrite was achieved based on fluorescence quenching of graphene quantum dots. To obtain reliable results, the effects of pH, temperature and reaction time on this fluorescence quenching system were studied. Under optimized conditions, decrease in fluorescence intensity of graphene quantum dots (F0/F) showed a good linear relationship with nitrite concentration between 0.007692–0.38406 mmol/L and 0.03623–0.13043 μmol/L; the limits of detection were 9.8 μmol/L and 5.4 nmol/L, respectively. Variable temperature experiments, UV absorption spectra and thermodynamic calculations were used to determine the quenching mechanism, and indicated that it was an exothermic, spontaneous dynamic quenching process. This method was used to analyse urine samples, and showed that it could be applied to analyse biological samples.
Datum: 25.10.2017

Enhanced red emission from BaMoO4: Eu3+ by Bi3+ co-doping

A series of Bi3+,Eu3+-doped BaMoO4 phosphors was synthesized using a hydrothermal method. The crystal structure, morphology and optical properties of the phosphors were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL) measurements. Three different particle morphologies were detected in the SEM observation. The energy dispersive spectroscopy (EDS) results indicated that the solubility of Bi3+ in spherical or rugby-like BaMoO4 particles was very low and the excess Bi3+ element was cumulated in the irregular particles. Characteristic emissions of Eu3+ ions (5D0  7FJ; J = 0, 1, 2, 3, 4) were observed under excitation in ultraviolet (UV) light, with the most intense transition being the 5D0  7F2 transition. Energy transfer from MoO42− and Bi3+ to Eu3+ can be readily achieved. Red emission intensity of Eu3+ was enhanced by a factor of two by co-doping with a small amount of Bi3+. Optical properties as a function of Bi3+ content were studied and the optimum Bi3+ content in BaMoO4 nanocrystals was determined to be 0.4 mol%.
Datum: 23.10.2017

A comparative study on intrinsic fluorescence of BSA and lysozyme proteins in presence of different divalent ions from their solution and thin film conformations

Optical emission behaviours of lysozyme and bovine serum albumin, from bulk and thin film geometry, were studied in the presence of three different divalent ions (Mg2+, Ca2+ or Ba2+) using different spectroscopic [steady-state fluorescence, UV–Vis and Fourier transform infra-red (FTIR)] techniques. Additionally, protein thin films on silicon surfaces were prepared and morphological studies were carried out using atomic force microscopy. Dynamic quenching was mainly identified for both proteins in the presence of Mg2+, Ca2+ and Ba2+ ions. The molecular conformation of the proteins was modified in thin films compared with that in solution, consequently quenching efficiencies also varied. ATR-FTIR studies confirmed the conformational changes of proteins in the presence of all divalent ions. All metal ions used were divalent in nature and belonged to the same group of the periodic table but, depending on their individual characteristics such as electron affinity, ionic radius, etc., the magnitude of the protein and hydrated ion interaction varied and accordingly the quenching efficiency was modified. Quenching was maximum for Ca2+ ions, followed by the other two ions. Our study clearly illustrates the geometry-dependent physical and biological functions of proteins.
Datum: 20.10.2017

Spectroscopic investigation of the anticancer alkaloid piperlongumine binding to human serum albumin from the viewpoint of drug delivery

Piperlongumine (PL) is a very promising natural agent with a high potential for cancer treatment. To overcome the poor water solubility of PL, there is a need to develop a novel water-soluble formulation in which PL is non-covalently bound to human serum albumin (HSA). PL binding to HSA was studied by various spectroscopic techniques under simulated physiological conditions. Spectroscopic evidence showed that the interaction of PL with HSA could form a PL–HSA complex. The binding constant (Ka) values increased with increasing temperature, and a similar dependence was observed for the number of binding sites (n) values. The number of PL molecules bound to HSA reached 8.1 when the temperature was raised to 308 K. Thermodynamic calculation results suggested that the binding reaction occurred spontaneously but was an entropy-driven process, and hydrophobic forces played a major role in stabilizing the complex. Furthermore, PL binding induced conformational and microenvironmental changes in HSA. Displacement studies indicated that PL and warfarin had separate binding regions in site I. Therefore, it would be possible to develop a novel water-soluble formulation involving PL and HSA. This study may provide some valuable information in terms of improving the poor water solubility of PL.
Datum: 18.10.2017

Highly luminescent nitrogen-doped carbon dots for simultaneous determination of chlortetracycline and sulfasalazine

Here, we have presented a green and facile strategy to fabricate nitrogen-doped carbon dots (N-CDs) and their applications for determination of chlortetracycline (CTC) and sulfasalazine (SSZ). The fluorescent N-CDs, prepared by one-step hydrothermal reaction of citric acid and l-arginine, manifested numerous excellent features containing strong blue fluorescence, good water-solubility, narrow size distribution, and a high fluorescence quantum yield (QY) of 38.8%. Based on the fluorescence quenching effects, the as-synthesized N-CDs as a fluorescent nanosensor exhibited superior analytical performances for quantifying CTC and SSZ. The linear range for CTC was calculated to be from 0.85 to 20.38 μg ml−1 with a low detection limit of 0.078 μg ml−1. Meanwhile, the linear range for SSZ was estimated to be from 0.34 to 6.76 μg ml−1 with a low detection limit of 0.032 μg ml−1. Therefore, the N-CDs hold admirable application potential for constructing a fluorescent sensor for pharmaceutical analysis.
Datum: 18.10.2017

Synthesis and characterization of high quantum yield and oscillator strength 6-chloro-2-(4-cynophenyl)-4-phenyl quinoline (cl-CN-DPQ) organic phosphor for solid-state lighting

A novel blue luminescent 6-chloro-2-(4-cynophenyl) substituted diphenyl quinoline (Cl-CN DPQ) organic phosphor has been synthesized by the acid-catalyzed Friedlander reaction and then characterized to confirm structural, optical and thermal properties. Structural properties of Cl-CN-DPQ were analyzed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDAX) spectroscopy. FTIR spectra confirmed the presence of different functional groups and bond stretching. 1H–NMR and 13C–NMR confirmed the formation of an organic Cl-CN-DPQ compound. X-ray diffraction study provided its crystalline nature. The surface morphology of Cl-CN-DPQ was analyzed by SEM, while EDAX spectroscopy revealed the elemental analysis. Differential thermal analysis (TGA/DTA) disclosed its thermal stability up to 250°C. The optical properties of Cl-CN-DPQ were investigated by UV–vis absorption and photoluminescence (PL) measurements. Cl-CN-DPQ exhibits intense blue emission at 434 nm in a solid-state crystalline powder with CIE co-ordinates (0.157, 0.027), when excited at 373 nm. Cl-CN-DPQ shows remarkable Stokes shift in the range 14800–5100 cm−1, which is the characteristic feature of intense light emission. A narrow full width at half-maximum (FWHM) value of PL spectra in the range 42–48 nm was observed. Oscillator strength, energy band gap, quantum yield, and fluorescence energy yield were also examined using UV–vis absorption and photoluminescence spectra. These results prove its applications towards developing organic luminescence devices and displays, organic phosphor-based solar cells and displays, organic lasers, chemical sensors and many more.
Datum: 18.10.2017

Nitrogen-doped carbon dots as a fluorescent probe for the highly sensitive detection of Ag+ and cell imaging

An easy hydrothermal synthesis strategy was applied to synthesize green-yellow emitting nitrogen-doped carbon dots (N-CDs) using 1,2-diaminobenzene as the carbon source, and dicyandiamide as the dopant. The nitrogen-doped CDs resulted in improvement in the electronic characteristics and surface chemical activities. N-CDs exhibited bright fluorescence emission and could response to Ag+ selectively and sensitively. Other ions produced nearly no interference. A N-CDs based fluorescent probe was then applied to sensitively determine Ag+ with a detection limit of 5 × 10−8 mol/L. The method was applied to the determination of Ag+ dissolved in water. Finally, negligibly cytotoxic, excellently biocompatibile, and highly fluorescent carbon dots were applied for HepG2 cell imaging and the quenched fluorescence by adding Ag+, which indicated its potential applications.
Datum: 18.10.2017

Colorimetric detection of oxalate in aqueous solution by a pyrogallol red-based Cu2+ complex

The pyrogallol red (PR)-based Cu2+ complex was proven to be an effective and selective colorimetric chemosensing ensemble for recognition of oxalate over other anions in a perfect aqueous solution. The addition of oxalate to the PR–Cu2+ complex resulted in a colour change from purple to orange colour due to the regeneration of PR by the chelation of oxalate with Cu2+, while other anions did not induce any significant colour change. Moreover, it was revealed that no obvious interference was observed during the titrations with oxalate into each other anion. Therefore, the PR–Cu2+ complex can be used as a simple and practical colorimetric chemosensor for detecting oxalate.
Datum: 18.10.2017

Synthesis of carbon-based quantum dots from starch extracts: Optical investigations

Carbon-based quantum dots (C-QDs) were synthesized through microwave-assisted carbonization of an aqueous starch suspension mediated by sulphuric and phosphoric acids. The as-prepared C-QDs showed blue, green and yellow luminescence without the addition of any surface-passivating agent. The C-QDs were further analyzed by UV−vis spectroscopy to measure the optical response of the organic compound. The energy gaps revealed narrow sizing of C-QDs in the semiconductor range. The optical refractive index and dielectric constant were investigated. The C-QDs size distribution was characterized. The results suggested an easy route to the large scale production of C-QDs materials.
Datum: 12.10.2017

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Datum: 10.10.2017

Probing the interaction of cephalosporin with bovine serum albumin: A structural and comparative perspective

Cephalosporins belong the largest class of antibiotics used in the treatment of a wide range of infectious diseases caused by susceptible organisms. In the present study, we chose two typical antibiotics cefalexin/cefixime based on their structure, and investigated the interaction of cephalexin/cefixime with bovine serum albumin (BSA) using UV–vis absorption spectra, fluorescence spectroscopy, circular dichroism (CD) spectroscopy and molecular modeling approaches. Spectroscopic experiments revealed the formation of a BSA − cefalexin/cefixime complex. The binding parameters calculated using a modified Stern − Volmer method and the Scatchard method reached 103–104 L·mol−1. Thermodynamic parameter studies revealed that binding characteristics by negative enthalpy and positive entropy changes, and electrostatic interactions play a major role. Site marker competitive displacement experiments and molecular modeling approaches demonstrated that cefalexin and cefixime bind with appropriate affinity to site I (subdomain IIA) of BSA. Furthermore, synchronous fluorescence spectra, CD spectra and molecular modeling results indicated that the secondary structure of BSA was changed in the presence of cefalexin and cefixime. Additionally, the effects of metal ions on the BSA − cefalexin/cefixime system were also assessed.
Datum: 04.10.2017

Application of quinone-based fluorophore and native fluorescence for the spectrofluorimetric determination of agomelatine in dosage form: Identification of acidic and alkaline- induced degradation products by LC–MS/TOF

Three spectrofluorimetric methods were developed for agomelatine (AGM) determination in commercial tablets. Method A is based on measuring the native fluorescence of AGM aqueous solution at 230/360 nm. Methods B and C are based on the formation of a charge transfer complex between AGM and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) with measurement of the formed fluorophore at 365/475 nm and 250/304 nm, respectively. The relative fluorescence intensity (RFI) of AGM–DDQ complex was greatly enhanced in the presence of methyl-β-cyclodextrin (CD). The methods were linear over the concentration ranges of 0.015–0.5, 0.5–8.0, 0.09–6.0 and 0.05–0.2 μg/ml for AGM-native fluorescence, AGM–DDQ, AGM–DDQ–CD and AGM–TCNQ complexes, respectively with excellent correlation coefficients (r = 0.9999). The methods were validated as per the International Conference on Harmonization (ICH) guidelines and all validation requirements were satisfied. The developed methods were extended to the analysis of AGM in commercial tablets. Furthermore, the stability of AGM was studied under different stress conditions (alkaline, acidic, oxidative and photolytic). The potential alkaline and acidic degradation products were identified by LC–MS/TOF.
Datum: 02.10.2017

Selective fluorescence quenching of papain–Au nanoclusters by self-polymerization of dopamine

In this paper, we synthesized a papain-stabilized fluorescent Au nanocluster (NC) probe and studied its interaction with dopamine. As fluorescence of papain–Au NCs is quenched in the presence of dopamine under alkaline conditions, we were able to establish a simple, selective analytical method for dopamine determination. By studying the fluorescence lifetime and dynamic light scattering of the NCs before and after interaction with dopamine, we found that this fluorescence quenching mechanism was possibly due to dopamine self-polymerization that produced polydopamine that cross-linked papain–Au NCs. Based on this new phenomenon, we proposed a highly selective analytical method for dopamine detection. Other small organic molecules, such as amino acids, ascorbic acid and uric acid did not interfere with dopamine detection. Dopamine in the range 20–100 μM can be linearly detected by the fluorescence quenching ratio of gold nanoclusters. Dopamine detection could be visually realized by watching color changes of papain–Au NCs under UV light or daylight, as both fluorescence and absorption of the papain–Au NCs changed during dopamine polymerization.
Datum: 28.09.2017

Reviving near infra-red emission of Ag2S nanoparticles using interfacial defects in the Ag2S@CdS core–shell structure

Ag2S@CdS core–shell particles were synthesized with different Cd source content as a measure of shell thickness using a pulsed microwave irradiation method. The particles were verified structurally using X-ray diffraction, energy dispersive X-ray analysis and transmission electron microscopy. Optical spectroscopy revealed that core–shells show an absorption peak at 750 nm and an emission peak located around 800 nm after 6 min of microwave irradiation. With continued microwave treatment, the NIR luminescence first vanished but it was revived after 12 min of irradiation, which was 100 nm red shifted. This new type of NIR emission in Ag2S with sizes greater than 5 nm is due to the proximity of a highly deficient CdS shell with strong red emission that was stable for more than 6 months in water. A mechanism has been suggested for this type of emission.
Datum: 28.09.2017

Development of an optical sensor for chlortetracycline detection based on the fluorescence quenching of l-tryptophan

A simple and selective spectrofluorimetric method for the detection of chlortetracycline (CTC) was studied. In pH 7.4 buffer medium l-tryptophan (l-Trp), applied as the fluorescence probe, interacted with CTC resulting in fluorescence quenching of the probe. CTC was detected with maximum excitation and emission wavelengths at λex/λem = 275/350 nm. Notably, quenching of fluorescence intensities was positively proportional to the CTC concentration over the range of 0.65–30 μmol L−1 and the limit of detection was 0.2 μmol L−1. Effect of temperature shown in Stern−Volmer plots, absorption spectra and fluorescence lifetime determination, indicated that fluorescence quenching of l-Trp by CTC was mainly by static quenching. The proposed study used practical samples analysis satisfactorily.
Datum: 20.09.2017

A selective and sensitive fluorescent sensor for cysteine detection based on bi-8-carboxamidoquinoline derivative and Cu2+ complex

In this paper, a novel fluorescent sensor 1 for selective and sensitive detection of cysteine was developed based on a complex between bi-8-carboxamidoquinoline derivative ligand (L) and Cu2+. The interaction of Cu2+ with the ligand causes a dramatic fluorescence quenching most likely due to its high affinity towards Cu2+ and a ligand–metal charge transfer (LMCT) process. The in situ generated L–Cu2 complex was utilized as a chemosensing ensemble for cysteine. In the presence of cysteine, the fluorophore, L, was released from L–Cu2 complex because of the strong affinity of cysteine to Cu2+ via the Cu–S bond, leading to the fluorescence recovery of the ligand. The proposed displacement mechanism was confirmed by the results of mass spectrometry (MS) study. Under optimized conditions, the recovered fluorescence intensity is linear with cysteine concentrations in the range 1 × 10−6 mol/l to 8 × 10−6 mol/l. The detection limit for cysteine is 1.92 × 10−7 mol/l. Furthermore, the established method showed a highly sensitive and selective response to cysteine among the 20 fundamental α-amino acids used as the building blocks of proteins, after Ni2+ was used as a masking agent to eliminate the interference of His. The proposed sensor is applicable in monitoring cysteine in practical samples with good recovery rate.
Datum: 20.09.2017

Evaluation of chemical chaperones based on the monitoring of Bip promoter activity and visualization of extracellular vesicles by real-time bioluminescence imaging

It is known that endoplasmic reticulum (ER) stress in cells and extracellular vesicles (EVs) plays a significant role in cancer cells, therefore the evaluation of compounds that can regulate ER stress and EV secretion would be a suitable system for further screening and development of new drugs. In this study, we evaluated chemical chaperones derived from natural products based on monitoring Bip/GRP78 promoter activity during cancer cell growth, at the level of the single cell, by a bioluminescence microscopy system that had several advantages compared with fluorescence imaging. It was found that several chemical chaperones, such as ferulic acid (FA), silybin, and rutin, affected the activity. We visualized EVs from cancer cells using bioluminescence imaging and showed that several EVs could be observed when using CD63 fused with NanoLuc luciferase, which has a much smaller molecular weight and higher intensity than conventional firefly luciferase. We then examined the effects of the chemical chaperones on EVs from cancer cells by bioluminescence imaging and quantified the expression of CD63 in these EVs. It was found that the chemical chaperones examined in this study affected CD63 levels in EVs. These results showed that imaging at the level of the single cell using bioluminescence is a powerful tool and could be used to evaluate chemical chaperones and EVs from cancer cells. This approach may produce new information in this field when taken together with conventional and classical methods.
Datum: 20.09.2017

In situ biosensor for detection miRNA in living cells based on carbon nitride nanosheets with catalytic hairpin assembly amplification

In this study, an ultrasensitive fluorescence turn-on assay for in situ sensing of intracellular microRNA (miRNA) was developed utilizing a carbon nitride nanosheet (CNNS) and a catalytic hairpin assembly (CHA). The CHA showed favourable signal amplification for low-level biomarkers, and CNNS was an excellent candidate as a fluorescence quencher and gene vector. Moreover, the hairpin DNA of CHA could be adsorbed onto the surface of CNNS. An enzyme-free fluorescence biosensor for ultrasensitive sensing of intracellular miRNA in cells based on CHA and CNNS was designed. When faced with target miRNA, the fluorescence was recovered due to the miRNA, which could trigger cycling of CHA circuits, leading to the production of a marked enhanced fluorescence signal. Compared with traditional methods, the proposed method is convenient, with low cytotoxicity, and high specificity and ultrasensitivity. It has promising potential for detection low-level biomarkers.
Datum: 20.09.2017

Boron and nitrogen co-doped carbon dots as a sensitive fluorescent probe for the detection of curcumin

In this present study, a fluorescent probe was developed to detect curcumin, which is derived from the rhizomes of the turmeric. We used a simple and economical way to synthesize boron and nitrogen co-doped carbon dots (BNCDs) by microwave heating. The maximum emission wavelength of the BNCDs was 450 nm at an excitation wavelength of 360 nm. The as-prepared BNCDs were characterized by multiple analytical techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and infrared spectroscopy. The synthesized carbon nanoparticles had an average particle diameter of 4.23 nm. The BNCDs exhibited high sensitivity to the detection of curcumin at ambient conditions. The changes of BNCDs fluorescent intensity show a good linear relationship with the curcumin concentrations in the range 0.2–12.5 μM. This proposed method has been successfully applied to detect the curcumin in urine samples with the recoveries of 96.5–105.5%.
Datum: 15.09.2017

Comparison of molecular interactions of Ag2Te and CdTe quantum dots with human serum albumin by spectroscopic approaches

Ag2Te quantum dots (QDs) have attracted great attention in biological applications due to their superior photoluminescence qualities and good biocompatibility, but their potential biotoxicity at a molecular biology level has been rarely discussed. In order to better understand the basic behavior of Ag2Te QDs in biological systems and compare their biotoxicity to cadmium-containing QDs, a series of spectroscopic measurements was applied to reveal the molecular interactions of Ag2Te QDs and CdTe QDs with human serum albumin (HSA). Ag2Te QDs and CdTe QDs statically quenched the intrinsic fluorescence of HSA by electrostatic interactions, but Ag2Te QDs exhibited weaker quenching ability and weaker binding ability compared with CdTe QDs. Electrostatic interactions were the main binding forces and Sudlow's site I was the primary binding site during these binding interactions. Furthermore, micro-environmental and conformational variations of HSA were induced by their binding interactions with two QDs. Ag2Te QDs caused less secondary structural and conformational change in HSA, illustrating the lower potential biotoxicity risk of Ag2Te QDs. Our results systematically indicated the molecular binding mechanism of Ag2Te QDs with HSA, which provided important information for possible toxicity risk of these cadmium-free QDs to human health.
Datum: 14.09.2017

Enhancement of the luminescence properties of Sr3(PO4)2:Dy3+,Li+ white-light-emitting phosphors by charge compensator Li+ co-doping

Sr3(PO4)2:Dy3+,Li+ phosphors were prepared using a simple high temperature solid method for luminescence enhancement. The structures of the as-prepared samples agreed well with the standard phase of Sr3(PO4)2, even when Dy3+ and Li+ were introduced. Under ultraviolet excitation at 350 nm, the Sr3(PO4)2:Dy3+ sample exhibited two emission peaks at 483 nm and 580 nm, which were due to the 4F9/2  6H15/2 and 4F9/2  6H13/2 transitions of Dy3+ ions, respectively. A white light was fabricated using these two emissions from the Sr3(PO4)2:Dy3+ phosphors. The luminescence properties of Sr3(PO4)2:Dy3+,Li+ phosphors, including emission intensity and decay time, were improved remarkably with the addition of Li+ as the charge compensator, which would promote their application in near-ultraviolet excited white-light-emitting diodes.
Datum: 08.09.2017

Redox luminescence switch based on Mn2+-doped NaYF4:Yb,Er upconversion nanorods

An redox luminescence switch was developed for the sensing of glutathione (GSH), l-cysteine (Cys) or l-ascorbic acid (AA) based on redox reaction. The Mn2+-doped NaYF4:Yb,Er upconversion nanorods (UCNRs) with an emission peak located in the red region were synthesized. The luminescence intensity of the UCNRs could be quenched due to the Mn2+ could be oxidized to MnO2 by KMnO4. Subsequently, when the AA, GSH or Cys was added into the MnO2 modified upconversion nanosystem, which could reduced MnO2 to Mn2+ and the luminescence intensity was recovered. The concentration ranges of the nanosystem are 0.500–3.375 mM (R2 = 0.99) for AA, 0.6250–11.88 mM (R2 = 0.99) for GSH and 0.6250–9.375 mM (R2 = 0.99) for Cys, respectively.
Datum: 07.09.2017

Rapid and sensitive colorimetric detection of ascorbic acid in food based on the intrinsic oxidase-like activity of MnO2 nanosheets

In this paper, we report a colorimetric sensor for the rapid, selective detection of ascorbic acid (AA) in aqueous solutions. Single-layered MnO2 nanosheets were established as an artificial oxidase; consequently colorless 3,3´,5,5´-tetramethylbenzidine (TMB) was oxidized to a blue product (oxTMB), with increase in absorbance at 650 nm. The absorbance of the reaction system decreased after introduction AA, which reduced MnO2 into Mn2+. Under optimum conditions, a detection limit of 62.81 nM for AA in aqueous solutions could be achieved. The linear response range for AA was 0.25–30 μM with a correlation coefficient of 0.996. Importantly, the MnO2 nanosheet–TMB chromogenic reaction exhibited great selectivity as there was no interference from other metal ions, amino acids and small biological molecules. The proposed colorimetric sensing of AA could be applied for fruit, juice and pharmaceutical samples. Moreover, the proposed sensor showed satisfying performance, including low cost, easy preparation, rapid detection, and good biocompatibility.
Datum: 30.08.2017

Terbium (III) coordination polymer–copper (II) compound as fluorescent probe for time-resolved fluorescence ‘turn-on’ detection of hydrogen sulfide

With recognition of the biological importance of hydrogen sulfide (H2S), we present a simple and effective fluorescent probe for H2S using a Tb3+ coordination polymer–Cu2+ compound (DPA/Tb/G–Cu2+). Dipicolinic acid (DPA) and guanosine (G) can coordinate with Tb3+ to form a macromolecular coordination polymer (DPA/Tb/G). DPA/Tb/G specifically binds to Cu2+ in the presence of coexisting cations, and obvious fluorescence quenching is observed. The quenched fluorescence can be exclusively recovered upon the addition of sulfide, which is measured in the mode of time-resolved fluorescence. The fluorescence intensities of the DPA/Tb/G–Cu2+ compound enhance linearly with increasing sulfide concentrations from 1 to 30 μM. The detection limit for sulfide in aqueous solution is estimated to be 0.3 μM (at 3σ). The DPA/Tb/G–Cu2+ compound was successfully applied to sense H2S in human serum samples and exhibited a satisfactory result. It displays some desirable properties, such as fast detection procedure, high selectivity and excellent sensitivity. This method is very promising to be utilized for practical detection of H2S in biological and environmental samples.
Datum: 30.08.2017

Silica-modified luminescent LaPO4:Eu@LaPO4@SiO2 core/shell nanorods: Synthesis, structural and luminescent properties

Monoclinic-type tetragonal LaPO4:Eu (core) and LaPO4:Eu@LaPO4 (core/shell) nanorods (NRs) were successfully prepared using a urea-based co-precipitation process under ambient conditions. An amorphous silica layer was coated around the luminescent core/shell NRs via the sol–gel process to improve their solubility and colloidal stability in aqueous and non-aqueous media. The prepared nano-products were systematically characterized by X-ray diffraction pattern, transmission electron microscopy, energy dispersive X-ray analysis, and FTIR, UV/Vis, and photoluminescence spectroscopy to examine their phase purity, crystal phase, surface chemistry, solubility and luminescence characteristics. The length and diameter of the nano-products were in the range 80–120 nm and 10–15 nm, respectively. High solubility of the silica-modified core/shell/Si NRs was found for the aqueous medium. The luminescent core NRs exhibited characteristic excitation and emission transitions in the visible region that were greatly affected by surface growth of insulating LaPO4 and silica layers due to the multiphonon relaxation rate. Our luminescence spectral results clearly show a distinct difference in intensities for core, core/shell, and core/shell/Si NRs. Highly luminescent NRs with good solubility could be useful candidates for a variety of photonic-based biomedical applications.
Datum: 17.08.2017

Preliminary results on the photoluminescence and optically stimulated luminescence in Cu-doped and Ag-doped ZnB2X4 (B = Li, Na, K: X = Cl, Br) compounds

Photoluminescence, and optically stimulated luminescence in ZnB2X4 (B; Li,Na,K: X; Cl,Br) compounds doped with Cu+ or Ag+ were studied. Double humped emission bands attributable to the activators were observed in all the samples. The observed photoluminescence of Cu+ and Ag+ could be identified with 3d94s13d10 and 4d95s15d10 transitions respectively. The longer wavelength band (400–500 nm range) could be attributed to the Cu+ or Ag+ ion replacing alkali ion at the octahedral alkali site whereas short wavelength band (340–400 nm range) is attributed to a Cu or Ag ion at tetrahedral zinc site. The short wavelength band was found to be intense compared with long wavelength and gave an indication that most of the Cu or Ag ions prefered a tetrahedral Zn site compared with the octahedral alkali site. All the samples exhibit optically stimulated luminescence (OSL). The sensitivity was found to be lattice dependent. The lowest sensitivity of about 1% compared with Al2O3:C was observed in lithium lattices whereas highest the sensitivity of about 290% was observed in the case of Cu-doped ZnNa2Br4.
Datum: 17.08.2017

Synthesis, density functional theory calculations and luminescence of lanthanide complexes with 2,6-bis[(3-methoxybenzylidene)hydrazinocarbonyl] pyridine Schiff base ligand

A pyridine-diacylhydrazone Schiff base ligand, L = 2,6-bis[(3-methoxy benzylidene)hydrazinocarbonyl]pyridine was prepared and characterized by single crystal X-ray diffraction. Lanthanide complexes, Ln–L, {[LnL(NO3)2]NO3.xH2O (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Er)} were prepared and characterized by elemental analysis, molar conductance, thermal analysis (TGA/DTGA), mass spectrometry (MS), Fourier transform infra-red (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. Ln–L complexes are isostructural with four binding sites provided by two nitro groups along with four coordination sites for L. Density functional theory (DFT) calculations on L and its cationic [LnL(NO3)2]+ complexes were carried out at the B3LYP/6–31G(d) level of theory. The FT-IR vibrational wavenumbers were computed and compared with the experimentally values. The luminescence investigations of L and Ln–L indicated that Tb–L and Eu–L complexes showed the characteristic luminescence of Tb(III) and Eu(III) ions. Ln–L complexes show higher antioxidant activity than the parent L ligand.
Datum: 17.08.2017

A sensitive surface-enhanced Raman scattering method for chondroitin sulfate with Victoria blue 4R molecular probes in nanogold sol substrate

Using silver nanoparticles (AgNPs) as the nanocatalyst, l-cysteine rapidly reduced HAuCl4 to make a stable gold nanoparticle sol (Ag/AuNP) that had a high surface-enhanced Raman scattering (SERS) activity in the presence of Victoria blue 4R (VB4r) molecular probes. Under the selected conditions, chondroitin sulfate (Chs) reacted with the VB4r probes to form associated complexes that caused the SERS effect to decrease to 1618 cm−1. The decreased SERS intensity was linear to the Chs concentration in the range 3.1–500 ng/ml, with a detection limit of 1.0 ng/ml Chs. Accordingly, we established a simple and sensitive SERS quantitative analysis method to determine Chs in real samples, with a relative standard deviation of 1.47–3.16% and a recovery rate of 97.6–104.2%.
Datum: 11.08.2017

Effect of erbium ion concentration on structural and luminescence properties of lead borosilicate glasses for fiber amplifiers

This investigation reports, the effect of the concentration of erbium and lead ions on the physical, structural and optical properties of lead borosilicate glasses. These glasses were synthesized by the melt quench method. In the synthesis, the concentration of the erbium (Er3+) ion was varied in the order of 0.0, 0.1, 0.5, 1.0 and 2.0 mol% and lead (Pb2+) ion was varied in the order of 30, 29.9, 29.5, 29 and 28 mol%. The glasses were analyzed using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and UV–vis–NIR spectroscopy. From XRD, the amorphous nature of lead borosilicate glasses was confirmed. The functional groups which were present in the glasses have been identified by analyzing the FT-IR spectrum. From the absorption spectra, the oscillator strengths as well as the Judd–Ofelt (JO) intensity parameters were determined and compared with other hosts. The JO intensity parameters were further used to calculate certain radiative properties for the excited luminescent levels of Er3+ ion. From emission spectra, full width at half maxima (FWHM), stimulated emission cross-sections (σe) and certain lasing parameters were evaluated and compared with reference host glasses. The lifetimes of 4I13/2 excited level of Er3+ ion have also been recorded and analyzed. The calculated and experimental lifetimes were compared in terms of quantum efficiencies. From the photoluminescence analysis, the erbium doped lead borosilicate glasses well suited for optical fiber amplifiers are discussed.
Datum: 08.08.2017

Ratiometric fluorescence detection of superoxide anion based on AuNPs-BSA@Tb/GMP nanoscale coordination polymers

A novel ratiometric fluorescence nanosensor for superoxide anion (O2•−) detection was designed with gold nanoparticles-bovine serum albumin (AuNPs-BSA)@terbium/guanosine monophosphate disodium (Tb/GMP) nanoscale coordination polymers (NCPs) (AuNPs-BSA@Tb/GMP NCPs). The abundant hydroxyl and amino groups of AuNPs-BSA acted as binding points for the self-assembly of Tb3+ and GMP to form core-shell AuNPs-BSA@Tb/GMP NCP nanosensors. The obtained probe exhibited the characteristic fluorescence emission of both AuNPs-BSA and Tb/GMP NCPs. The AuNPs-BSA not only acted as a template to accelerate the growth of Tb/GMP NCPs, but also could be used as the reference fluorescence for the detection of O2•−. The resulting AuNPs-BSA@Tb/GMP NCP ratiometric fluorescence nanosensor for the detection of O2•− demonstrated high sensitivity and selectivity with a wide linear response range (14 nM–10 μM) and a low detection limit (4.7 nM).
Datum: 04.08.2017

Luminescent properties of single-phase Ba2-x-1.5y-1.5zP2O7:xEu2+,yCe3+, zTb3+ phosphors for white light-emitting diode

A series of Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors was synthesized via a co-precipitation method, then their crystal structure, quantum efficiency and luminescent properties were analyzed by XRD and FL, respectively. The results showed that these phosphors not only presented the excitation characteristics of Ba2P2O7:xEu2+,zTb3+, but also exhibited that of the Ba2P2O7:yCe3+,zTb3+ phosphor. Meanwhile, the tri-doped phosphor showed a stronger absorption around 320 nm in contrast with the Eu2+/Ce3+:Tb3+ co-doped phosphor. Not only can energy transfer from Ce3+Eu2+ be observed; the energy transfer mechanism from Eu2+ to Tb3+ is discussed in the tri-doped system. Ce3+ affects the luminescence properties of Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors just as the sensitizer whereas Eu2+ is considered both as the sensitizer and the activator. The chromaticity coordinates of tri-doped phosphors excited at 320 nm stayed steadily in the bluish-white light region,and the emitted color and color temperature (CCT) of these phosphors could be tuned by adjusting the relative contents of Eu2+, Ce3+ and Tb3+. Hence, the single phase Ba2P2O7:xEu2+,yCe3+,zTb3+ phosphors may be considered as potential candidates for white light-emitting diodes.
Datum: 01.08.2017

Improved sensitivity of firefly luminescent intermediate-based protein interaction assay using Ser 440 mutant with lower adenylation activity

Protein–protein interaction assays are important in various fields including molecular biology, diagnostics, and drug screening. We recently designed a novel protein–protein interaction assay, the firefly luminescent intermediate-based protein interaction assay (FlimPIA), that exploited the unique reaction mechanism of firefly luciferase (Fluc). Using two mutant Flucs, each impaired with one of the two half-reactions, namely adenylation and subsequent oxidative luminescent steps, FlimPIA detects the proximity of the two proteins tethered to the mutant Flucs. Here, we found that introducing a mutation into a residue in the hinge region (S440) of the mutant with lowered adenylation activity (‘Acceptor’ Fluc) further improved the response of FlimPIA by lowering the residual adenylation activity. Mutants with bulkier residues showed greater inhibition, probably due to increased steric hindrance at the adenylation conformation. As a result, the FlimPIA with S440 L acceptor showed the best signal/background ratio for the detection of rapamycin-induced FKBP12–FRB interactions.
Datum: 28.07.2017

Investigation of the interaction of aurantio-obtusin with human serum albumin by spectroscopic and molecular docking methods

The interaction between human serum albumin (HSA) and aurantio-obtusin was investigated by spectroscopic techniques combined with molecular docking. The Stern–Volmer quenching constants (KSV) decreased from 8.56 × 105 M−1 to 5.13 × 105 M−1 with a rise in temperatures from 289 to 310 K, indicating that aurantio-obtusin produced a static quenching of the intrinsic fluorescence of HSA. Time-resolved fluorescence studies proved again that the static quenching mechanism was involved in the interaction. The sign and magnitude of the enthalpy change as well as the entropy change suggested involvement of hydrogen bonding and hydrophobic interaction in aurantio-obtusin–HSA complex formation. Aurantio-obtusin binding to HSA produced significant alterations in secondary structures of HSA, as revealed from the time-resolved fluorescence, Fourier transform infrared (FT-IR) spectroscopy, three-dimensional (3D) fluorescence and circular dichroism (CD) spectral results. Molecular docking study and site marker competitive experiment confirmed aurantio-obtusin bound to HSA at site I (subdomain IIA).
Datum: 26.07.2017

Preparation of carbon dot-based ratiometric fluorescent probes for cellular imaging from Curcuma longa

This work derived biocompatible and stable probes based on fluorescent nanoparticles (FNPs) from a natural source, Curcuma longa. The multi-color fluorescence emissions from carbonized Curcuma longa (C-FNPs) obtained through defined dehydration conditions are soluble in water and have a small particle size (~17 nm). The surface passivation with polyethylene glycol (PEG) capped with amine groups in FNPs (P-FNPs) generated a probe with a higher quantum yield and longer fluorescence lifetime than obtained with C-FNPs. The X-ray photoelectron spectroscopy and X-ray diffraction spectra confirmed the associated chemical moieties of C-FNPs and P-FNPs. Furthermore, the prepared material showed non-toxic effects with almost 100% cell viability, even at high concentrations. In conclusion, fluorescence sensors from natural sources may be useful for numerous biomedical research applications.
Datum: 18.07.2017

Characterization of a highly Al3+-selective fluorescence probe based on naphthalimide-Schiff base and its application to practical water samples

A new fluorescent Al3+-probe, N-allyl-4-[3,3′-((2-aminoethyl)azanediyl)-bis(N´-(2-hydroxybenzylidene)propanehy-drazide)]-1,8-naphthalimide (L), was designed and synthesized based on 1,8-naphthalimide. The probe L contains 1,8-naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. The structure of L was determined by single crystal X-ray. L emission at 526 nm increased on addition of Al3+ under excitation wavelength at 350 nm. L exhibited high selectivity and sensitivity fluorescence emission towards to Al3+ in ethanol/Tris–HCl buffer solution (1:1, v/v, pH = 7.2) as compared with other tested metal ions. A good linearity with a correlation coefficient (R2) of 0.99 was observed in the concentration range 2–10 μM. The binding constant and the detection limit of L for Al3+ were calculated to 2.6 × 104 M−1 and 0.34 μM, respectively. The results of experiments that including Job plot, ultraviolet–visible (UV–Vis) light titration, fluorescence titration, ESI-MS and 1H NMR titration, indicated a 1:1 stoichiometric complex between L and Al3+. L was highly effective in monitoring Al3+ in real-life Yellow River and tap water samples.
Datum: 18.07.2017

An electrochemiluminescent method for glutamate measurement in small microdialysate samples in asphyxiated young rats

Glutamate (Glu) quantification has been performed by a combination of intracerebral microdialysis through which the samples are obtained and analyzed by high performance liquid chromatography (HPLC); its measurement requires a large expenditure of time (15–30 min per sample) and special training. Therefore, an alternative method is presented here, based on the electrochemiluminescence produced by the use of an enzymatic reactor, containing glutamate-oxidase, mixed and incubated with microdialysate from dorsal striatum (DS) and prefrontal cortex (PFC) of young rats asphyxiated during the neonatal period, under a global asphyxia model in order to test this method. Using this approach, we found high extracellular Glu concentration in the DS of asphyxiated animals, but only during K+ stimulation, while in the PFC, only a delay in the rise of Glu after K+ stimulation was observed, without any difference in extracellular Glu content when compared with controls. This new method permitted a fast measurement of Glu in brain dialysate samples, it significantly reduces the cost of the analysis per sample, since only a single device and pump are needed without using columns and high pressure inside the system or complex hardware and software to control pumps, detector, fraction collector or any other peripheral used in HPLC.
Datum: 18.07.2017

A rhodamine-triazole fluorescent chemodosimeter for Cu2+ detection and its application in bioimaging

A rhodamine-based fluorescent chemodosimeter rhodamine hydrazide-triazole (RHT) tethered with a triazole moiety was developed for Cu2+ detection. In aqueous medium, the RHT probe exhibited high selectivity and sensitivity toward Cu2+ among other metal ions. The addition of Cu2+ triggered a fluorescence emission of RHT by 384-fold (Φ = 0.33) based on a ring-opening process and a subsequent hydrolysis reaction. Moreover, RHT also showed a selective colorimetric response toward Cu2+ from colorless solution to pink, readily observed with the naked eye. The limit of detection of RHT for Cu2+ was calculated to be 1 nM (0.06 ppb). RHT was successfully demonstrated to detect Cu2+ in Chang liver cells by confocal fluorescence microscopy.
Datum: 17.07.2017

Investigation on the pH-independent photoluminescence emission from carbon dots impregnated on polymer matrix

Highly luminescent, polymer nanocomposite films based on poly(vinyl alcohol) (PVA), and monodispersed carbon dots (C-dots) derived from multiwalled carbon nanotubes (MWCNTs), as coatings on substrates as well as free standing ones are obtained via solution-based techniques. The synthesized films exhibit pH-independent photoluminescence (PL) emission, which is an advantageous property compared with the pH-dependent photoluminescence intensity variations, generally observed for the C-dots dispersed in aqueous solution. The synthesized C-dots and the nanocomposite films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), ultraviolet (UV) − visible spectroscopy and photoluminescence spectroscopy (PL) techniques. The TEM image provides clear evidence for the formation of C-dots of almost uniform shape and average size of about 8 nm, homogeneously dispersed in aqueous medium. The strong anchoring of C-dots within the polymer matrix can be confirmed from the XRD results. The FTIR spectral studies conclusively establish the presence of oxygen functional groups on the surfaces of the C-dots. The photoluminescence (PL) emission spectra of the nanocomposite films are broad, covering most part of the visible region. The PL spectra do not show any luminescence intensity variations, when the pH of the medium is changed from 1 to 11. The pH-independent luminescence, shown by these films offers ample scope for using them as coatings for designing diagnostic and imaging tools in bio medical applications. The non-toxic nature of these nanocomposite films has been established on the basis of cytotoxicity studies.
Datum: 17.07.2017

An OFF–ON–OFF type fluorescent probe based on a naphthalene derivative for Al3+ and F− ions and its biological application

A novel fluorescent probe-based naphthalene Schiff, 1-(C2-glucosyl-ylimino-methyl)-naphthalene-2-ol (L) was synthesized by coupling d-glucosamine hydrochloride with 2-hydroxy-1-naphthaldehyde. It exhibited excellent selectivity and highly sensitivity for Al3+ in ethanol with a strong fluorescence response, while other common metal ions such as Pb2+, Mg2+, Cu2+, Co2+, Ni2+, Cd2+, Fe2+, Mn2+, Hg2+, Li+, Na+, K+, Fe3+, Cr3+, Zn2+, Ag+, Ba2+ and Ca2+ did not cause the same fluorescence response. The probe selectively bound Al3+ with a binding constant (Ka) of 5.748 × 103 M−1 and a lowest detection limit (LOD) of 4.08 nM. Moreover, the study found that the fluorescence of the L − Al3+ complex could be quenched after addition of F− in the same medium, while other anions, including Cl−, Br−, I−, NO2−, NO3−, ClO4−, CO32−, HCO3−, SO42−, HSO4−, CH3COO−, PO43−, HPO42−, S2− and S2O32− had nearly no influence on probe behaviour. Binding of the [L − Al3+] complex to a F− anion was established by different fluorescence titration studies, with a detection limit of 3.2 nM in ethanol. The fluorescent probe was also successfully applied in the imaging detection of Al3+ and F− in living cells.
Datum: 17.07.2017

Zero and second-derivative synchronous fluorescence spectroscopy for the quantification of two non-classical β-lactams in pharmaceutical vials: Application to stability studies

The formation of metal chelates with various ligands may lead to the production of fluorescent chelates or enhance the fluorescence of the chelating agent. This paper describes two sensitive, selective and computer-solved methods, namely, zero order (SF) and second-derivative synchronous spectrofluorimetry (SDSFS) for nano-quantitation of two carbapenems; meropenem (MP) and ertapenem (EP). The methods are based on the chelation of MP with Tb3+ and EP with Zr4+ in buffered organic medium at pH 4.0 to produce fluorescent chelates. In the zero order method, the relative synchronous fluorescence intensity is measured at 327.0 nm at Δλ = 70.0 and 100.0 nm for MP and EP, respectively. The second method utilizes a second-derivative technique to enhance the method selectivity and emphasize a stability-indicating approach. The peak amplitudes (2D) of the second-derivative synchronous spectra were estimated to be 333.06 and 330.06 nm for MP and EP, respectively. The proposed synchronous spectrofluorimetric methods were validated according to the International Conference on Harmonization (ICH) guidelines and applied successfully for the analysis of MP and EP in pure forms, pharmaceutical vials and in synthetic mixtures with different degradants of both drugs. Under optimum conditions, the mole-ratio method was applied and the co-ordination ratios of MP–Tb3+ and EP–Zr4+chelates were found to be 1:1 and 1:3. The formation constants for the chelation complexes were evaluated using the Benesi–Hildebrand's equation; the free energy change (ΔG) was also calculated. The results indicated that EP–Zr4+ was more stable than the MP–Tb3+ chelate. Moreover, the developed methods were found to be selective and inexpensive for quantitative determination of both drugs in quality control laboratories at nano-levels.
Datum: 12.07.2017

A novel colorimetric fluorescence sensor for Fe3+ based on quinoline Schiff base

A novel fluorescent sensor bearing a quinoline and an anisidine moiety has been developed for highly selective detection of Fe3+, which shows photo-induced electron transfer (PET) behavior induced by Fe3+. Binding of Fe3+ to the sensor induced the electron of C = N group transfer from quinoline to iron, the result exhibits fluorescent enhancement. With the features of easy synthesis, simple structural skeleton and excellent sensing ability, the newly synthesized chemosensor also applied as a highly selective fluorescent probe in complex samples containing various competitive metal ions. The probe could fulfill various needs in biological and environmental fields.
Datum: 07.07.2017

A dual discrimination mode for improved specificity towards let-7a detection via a single-base mutated padlock probe-based exponential rolling circle amplification

MicroRNA (miRNA) family members are usually highly homologous sequences, and it is a challenging task to selectively detect one miRNA member from other family members in medical diagnosis. Here, we describe the design of a dual discrimination mode for improved specificity towards let-7a detection over the other members of the let-7 family, in which an intentional base mutation was introduced into the padlock probe of an exponential rolling circle amplification. The inherent discrimination power of the padlock probe and the introduced base mutation constituted a dual discrimination mode, which provided enhanced specificity for let-7a, even over single-base mismatched family sequences. Furthermore, the assay enabled the quantitative detection of let-7a in a dynamic range from 200 amol to 100 fmol. This technique has also been successfully applied to real small RNA samples extracted from human lung cancers. For the first time, through intentionally mutating one base on the padlock probe of the exponential rolling circle amplification (RCA), we improved the discrimination capability for let-7 family members, while maintaining adequate sensitivity. Overall, this dual discrimination mode and the high amplification strategy have the potential to be extended to other short, but highly homologous, miRNA sequences.
Datum: 07.07.2017

Life prediction for a vacuum fluorescent display based on two improved models using the three-parameter Weibull right approximation method

To obtain precise life information for vacuum fluorescent displays (VFDs), luminance degradation data for VFDs were collected from a group of normal life tests. Instead of exponential function, the three-parameter Weibull right approximation method (TPWRAM) was applied to describe the luminance degradation path of optoelectronic products, and two improved models were established. One of these models calculated the average life by fitting average luminance degradation data, and the other model obtained VFD life by combining the approximation method with luminance degradation test data from each individual sample. The results indicated that the test design under normal working stress was appropriate, and the selection of censored test data was simple. The two models improved by TPWRAM both revealed the luminance decaying law for VFD, and the pseudo failure time was accurately extrapolated. It was further confirmed by comparing relative error that using the second model gave a more accurate prediction of VFD life. The improved models in this study can provide technical references for researchers and manufacturers in aspects of life prediction methodology for its development.
Datum: 07.07.2017

Enhanced green emissions of Er3+/Yb3+ co-doped Gd2(MoO4)3 by co-excited up-conversion processes

Improving the emission from rare earth ions doped materials is of great importance to broaden their application in bio-imaging, photovoltaics and temperature sensing. The green emissions of Gd2(MoO4)3:Er3+/Yb3+ powder upon co-excitation with 980 and 808 nm lasers were investigated in this paper. Distinct enhancement of green emissions was observed compared with single laser excitation. Based on the energy level structure of Er3+, the enhancement mechanism was discussed. Moreover, the result of temperature-dependent enhancement revealed that the enhancement factor reached its maximum (2.5) as the sample heated to 120°C, which is due to the competition of two major thermal effects acting in the co-excited up-conversion processes. In addition, the same enhancement of green emissions was also observed in Gd2(MoO4)3:Er3+ powder and NaYF4:Er3+/Yb3+ powder.
Datum: 06.07.2017

Selective spectrofluorimetric method for determination of Lisinopril in pharmaceutical preparations and in presence of hydrochlorothiazide: Application to content uniformity testing

A novel sensitive and cost-effective spectrofluorimetric method has been developed and validated for determination of lisinopril (an angiotensin converting enzyme inhibitor) in its pure form and pharmaceutical preparations. The method is based on the reaction of the drug with ninhydrin and phenylacetaldehyde in buffered medium (pH 7.0) to form a highly fluorescent product measured at 460 nm after excitation at 390 nm. Different experimental parameters were optimized and calibration curve was constructed. The fluorescence-concentration relationship was linear in the range of 0.15–4.0 μg mL−1. The calculated Limit of detection (LOD) and Limit of quantitation (LOQ) were 0.04 and 0.12 μg mL−1, respectively. The method was successfully applied for the analysis of pharmaceutical preparations containing the studied drug either alone or co-formulated with hydrochlorothiazide. The obtained results were in agreement with those of the reported method in respect to accuracy and precession. Moreover, the method was applied content uniformity testing according to United States Pharmacopeia (USP) guidelines.
Datum: 06.07.2017

‘Turn-on’ fluorescent chemosensors based on naphthaldehyde-2-pyridinehydrazone compounds for the detection of zinc ion in water at neutral pH

A series of naphthaldehyde-2-pyridinehydrazone derivatives were discovered to display interesting ‘turn-on’ fluorescence response to Zn2+ in 99% water/DMSO (v/v) at pH 7.0. Mechanism study indicated that different substituent groups in the naphthaldehyde moiety exhibited significant influence on the detection of Zn2+. The electron rich group resulted in longer fluorescence wavelengths but smaller fluorescence enhancement for Zn2+. Among these compounds, 1 showed the highest fluorescence enhancement of 19-fold with the lowest detection limit of 0.17 μmol/L toward Zn2+. The corresponding linear range was at least from 0.6 to 6.0 μmol/L. Significantly, 1 showed an excellent selectivity toward Zn2+ over other metal ions including Cd2+.
Datum: 06.07.2017

Design and synthesis of the BODIPY–BSA complex for biological applications

A quinoxaline-functionalized styryl–BODIPY derivative (S1) was synthesized by microwave-assisted Knoevenagel condensation. It exhibited fluorescence enhancement upon micro-encapsulation into the hydrophobic cavity of bovine serum albumin (BSA). The S1–BSA complex was characterized systematically using ultraviolet (UV)–visible absorption, fluorescence emission, kinetics, circular dichroism and time-resolved lifetime measurements. The binding nature of BSA towards S1 was strong, and was found to be stable over a period of days. The studies showed that the S1–BSA complex could be used as a new biomaterial for fluorescence-based high-throughput assay for kinase enzymes.
Datum: 06.07.2017

The luminescence properties of Sr2–1.5x−1.5yP2O7:xDy3+,yCe3+ phosphor for near-UV-based white LEDs synthesized by a chemical co-precipitation method

A series of Sr2P2O7:Dy3+, Sr2P2O7:Ce3+ and Sr2P2O7:Dy3+,Ce3+ phosphors was synthesized via the one-step calcination process for the precursors prepared by co-precipitation methods. The phases, morphology, quantum efficiency and photoluminescence properties of the obtained phosphors were characterized systematically. These results show that the near-spherical particles prepared through calcining the precursors by means of ammonium dibasic phosphate co-precipitation (method 3) have the smallest particle size and strongest emission intensity among the three methods in the paper. With Dy3+ concentration increasing in Sr2P2O7:Dy3+ phosphors, the luminescence intensity first increases, reaches maximum, and then decreases. A similar trend was followed by Sr2P2O7:Ce3+ with Ce3+concentration increasing. A successful attempt was made to initiate the energy transfer mechanism from Ce3+ to Dy3+ in the host lattice and an overlap between the emission band of Ce3+ and the excitation band of Dy3+ indicated that the Ce3+  Dy3+ energy transfer may indeed exist. It is clear that the photoluminescence intensity of Dy3+ as well as the quantum efficiency of the phosphor can be enhanced markedly by co-doping Ce3+. Sr2P2O7:Dy3+,Ce3+ has its (CIE) chromaticity coordinates in the bluish-white-light region, near the standard illuminant D65. The CIE 1913 chromaticity coordinates of Sr2P2O7:Dy3+ phosphors fall in the white-light region, and are adjacent to the ideal white-light coordinates. In addition, the colour temperature and colour tone of Sr2P2O7:Dy3+ could be adjusted by changing the relative concentration of Dy3+. In short, Sr2P2O7:Dy3+ can be a promising single-phased white-light emitting phosphor for near-UV (NUV) w-LEDs.
Datum: 06.07.2017

Fluorescence sensing of dichlorvos pesticide by the luminescent Tb(III)-3-ally-salicylohydrazide probe

A fluorescent probe was developed and characterized, it consisted of terbium(III) with 3-ally-salicylohydrazide in ethanol, in which the 1:2 [Tb3+:S1] molar ratio was the best stoichiometric ratio for the probe. The ligand 3-ally-salicylohydrazide (S1) was synthesized, then was confirmed by IR, CHN, LC–MS and 1H NMR. The sensitivity of the probe's fluorescence spectra towards the presence of eight organophosphorus pesticides in ethanolic solution was studied, in which the probe showed marked sensitivity towards dichlorvos pesticide. A tangible enhancement of the probe's fluorescence intensity was observed as a consequence of the gradual addition of dichlorvos pesticide. The calculated limit of detection (LOD) was 1.183 μM and limit of quantitation (LOQ) was 3.94 μM. Further characterization of the nature of forces acting in the interaction of the probe with dichlorvos was performed by calculation of binding constants at different temperatures according to the Benesi − Hildebrand equation, and the thermodynamic parameters ΔH, ΔS and ΔG. In order to assess the analytical applicability of the method, the influence of various potentially interfering anion and cations that naturally occur in water and soil were calculated.
Datum: 29.06.2017

Synthesis and luminescence of novel near-infrared emitting BaZrSi3O9:Cr3+ phosphors

The BaZrSi3O9:Cr3+ phosphors were prepared by a high temperature solid state method. Their structures were confirmed with XRD and their luminescence properties were investigated. Under excitation at 455 nm, BaZrSi3O9:Cr3+ phosphors exhibited a broad near infrared emission band peaked at 800 nm, which was assigned to the 4T24A2 transition of Cr3+. The near infrared emission intensity reached a maximum at Cr3+ concentration of 0.7%. There was a concentration quenching phenomenon of Cr3+ in BaZrSi3O9 matrix and the corresponding concentration quenching mechanism was investigated. With efficient near infrared emission in the range of 700–1000 nm, BaZrSi3O9:Cr3+ phosphors may find applications in solar energy conversion.
Datum: 27.06.2017

Carbazole–azine based fluorescence ‘off–on’ sensor for selective detection of Cu2+ and its live cell imaging

A new carbazole–azine based fluorescent sensor was synthesized and characterized. The selectivity of the sensor for Cu2+ over other counter ions in a dimethyl sulfoxide/H2O mixture was shown through enhancement in fluorescence – an off to on transformation. The specificity of the probe towards Cu2+ was evident in ultraviolet/visible, fluorescence, Fourier transform infrared and mass studies. Application of the probe in the cell imaging and cytotoxicity of living cells is illustrated.
Datum: 20.06.2017

Structural and luminescent studies of erbium-doped CaZrO3 green-emitting nanophosphors

Erbium (Er) (0.5, 1.0 and 1.5 wt%)-doped CaZrO3 nanophosphors were synthesized by the sol–gel method using poly(vinyl alcohol) as the chelating agent. Their structural and photoluminescence properties were studied using X-ray diffraction (XRD), field emission scanning electron microscopy–energy dispersive spectroscopy (FESEM-EDS), transmission electron microscopy (TEM), photoluminescence and Fourier transform infrared spectroscopy (FTIR). The XRD patterns of the samples confirm that nanoscale crystallite sizes. Agglomeration of the samples was observed using field emission scanning electron microscopy images. Energy dispersive spectroscopy measurements confirmed the existence of Ca, Zr, O and Er in the samples. Average particle sizes for the samples were calculated from transmission electron microscopy images. FTIR spectra clearly show characteristic absorption bands related to the metal oxides, as well as some other organic molecules. The photoluminescence spectra show bands in the green region. The Commission International de l'Eclairage coordinates were calculated and found to be in green region.
Datum: 14.06.2017

Photoluminescence properties of Ca2Al2O5:RE3+ (RE = Eu, Dy and Tb) phosphors for solid state lighting

Ca2Al2O5:Eu3+, Ca2Al2O5:Dy3+ and Ca2Al2O5:Tb3+ phosphors were synthesized using a combustion synthesis method. The prepared phosphors were characterized by X-ray powder diffraction for phase purity, by scanning electron microscopy for morphology, and by photoluminescence for emission and excitation measurements. The Ca2Al2O5:Eu3+ phosphors could be efficiently excited at 396 nm and showed red emission at 594 nm and 616 nm due to 5D0  7F1 and 5D0  7F2 transitions. Dy3+-doped phosphors showed blue emission at 482 nm and yellow emission at 573 nm. Ca2Al2O5:Tb3+ phosphors showed emission at 545 nm when excited at 352 nm. Concentration quenching occurred in both Eu3+ and Dy3+phosphors at 0.5 mol%. Photoluminescence results suggested that the aluminate-based phosphor could be a potential candidate for application in environmentally friendly based lighting technologies.
Datum: 05.06.2017

A combined spectroscopic and TDDFT investigation of the solute-solvent interactions of two coumarin derivatives

The UV/Vis absorption and fluorescence characteristics of 3-cyano-7-hydroxycoumarin [CHC] and 7-amino-4-methyl-3-coumarinylacetic acid [AMCA-H] were studied at room temperature in several neat solvents and binary solvent mixtures of 1,4-dioxane/acetonitrile. The effects of solvent on the spectral properties are analyzed using single and multi-parameter solvent polarity scales. Both general solute/solvent interactions and hydrogen bond interactions are operative in these systems. The solvation of CHC and AMCA-H dyes in 1,4-dioxane/acetonitrile solvent mixtures has been studied. The solutes CHC and AMCA-H are preferentially solvated by acetonitrile and a synergistic effect is observed for both molecules in dioxane/acetonitrile solvent mixtures. In addition, using the solvatochromic method the ground- and the excited-state dipole moments of both the dyes were calculated. The ground- and excited-state dipole moments, absorption and emission maxima and HOMO–LUMO gap were also estimated theoretically using B3LYP/6–311+ G (d,p) level of theory in the gaseous phase, dioxane and acetonitrile solvents. Furthermore, changes in dipole moment values were also calculated using the variation of Stokes shift with the molecular–microscopic empirical solvent polarity parameter ( ETN). The observed excited-state dipole moments are larger than their ground-state counterparts, indicating a substantial redistribution of the electron densities in a more dipolar excited state for both coumarins investigated.
Datum: 05.06.2017

Paramecium caudatum as a source of nitric oxide: Chemiluminescent detection based on Bluestar® Forensic reagent connected with microdialysis

Nitric oxide (NO) chemistry inside the body is the most interesting part of its behavior. NO is involved in controlling blood pressure, and in transmitting nerve signals and a variety of other signaling processes. To explain the behavior of NO, it is necessary to determine its immediate concentration or observe time-dependent changes in its concentration. In Paramecium caudatum, NO is formed by calcium-dependent nNOS (NOS1)-like protein, which is distributed in the cytoplasm. NO synthesis affects the ciliary beat and consequent motility of cells and blocked NO synthesis reduces the ability of cells to move. The possibility of online coupling of microdialysis (of P. caudatum solution) with NO detection is demonstrated. Direct measurement of NO is carried out using dilute Bluestar® Forensic reagent (luminol–H2O2 system; one of the NO detections is based upon the chemiluminescent reaction between NO and the luminol–H2O2 system, which is specifically reactive to NO). The effect of a nitric oxide synthase inhibitor, NG-nitro-l-arginine methyl ester was observed. NO production was inhibited and the movement of P. caudatum was restricted. These effects were time dependent and after a specific time were reversed.
Datum: 05.06.2017

BSA–AuNPs@Tb–AMP metal–organic frameworks for ratiometric fluorescence detection of DPA and Hg2+

An easy and effective strategy for synthesizing a ratiometric fluorescent nanosensor has been demonstrated in this work. Novel fluorescent BSA–AuNPs@Tb–AMP (BSA, bovine serum albumin; AMP, adenosine 5′-monophosphate; AuNPs, Au nanoparticles) metal–organic framework (MOF) nanostructures were synthesized by encapsulating BSA–AuNPs into Tb–AMP MOFs for the detection of 2,6-pyridinedicarboxylic acid (DPA) and Hg2+. DPA could strongly co-ordinate with Tb3+ to replace water molecules from the Tb3+ center and accordingly enhanced the fluorescence of Tb–AMP MOFs. The fluorescence of BSA–AuNPs at 405 nm remained constant. While the fluorescence of BSA–AuNPs at 635 nm was quenched after Hg2+ was added, the fluorescence of Tb–AMP MOFs remained constant. Accordingly, a ratiometric fluorescence nanosensor was constructed for detection of DPA and Hg2+. The ratiometric nanosensor exhibited good selectivity to DPA over other substances. The F545/F405 linearly increased with increase of DPA concentration in the range of 50 nM to 10 μM with a detection limit as low as 17.4 nM. F635/F405 increased linearly with increase of Hg2+ concentration ranging from 50 nM to 1 μM with a detection limit as low as 20.9 nM. Additionally, the nanosensor could be successfully applied for the determination of DPA and Hg2+ in running water.
Datum: 01.06.2017

A colorimetric and fluorogenic probe for bisulfite using benzopyrylium as the recognition unit

A coumarin–benzopyrylium (CB) platform has been developed for the colorimetric and fluorogenic detection of bisulfite. The proposed probe utilizes coumarin as the fluorophore and positively charged benzopyrylium as the reaction site. The method employs the nucleophilic addition of bisulfite to the benzopyrylium moiety of CB to inactivate the electron-deficient oxonium ion. The driving force for photo-induced electron transfer is considerably diminished, thereby promoting the emission intensity of the coumarin fluorophore. The fluorescence intensity at 510 nm is linear with bisulfite concentration over a range of 0.2–7.5 μM with a detection limit of 42 nM (3δ). CB shows a rapid response (within 30 s) and high selectivity and sensitivity for bisulfite. Preliminary studies show that CB has great potential for bisulfite detection in real samples and in living cells.
Datum: 01.06.2017

Studies on the luminescence properties of cerium co-doping on Ca2MgSi2O7:Eu2+ phosphor by solid-state reaction method

Ca2MgSi2O7:Ce3+, Ca2MgSi2O7:Eu2+ and Ca2MgSi2O7:Eu2+,Ce3+ phosphors were prepared using the solid-state reaction method. The crystal structures of the sintered phosphors were of melilite type, which has a tetragonal crystallography. The chemical compositions of the sintered phosphors was confirmed by energy dispersive X-ray spectroscopy. The different thermoluminescence kinetic parameters [activation energy (E), frequency factor (s) and order of the kinetics (b)] of these phosphors were evaluated and compared using the peak shape method. Under ultraviolet excitation, the emission spectra of both Ca2MgSi2O7:Eu2+ and Ca2MgSi2O7:Eu2+,Ce3+ phosphors were composed of a broad emission band peaking at 530 nm. When the Ca2MgSi2O7:Eu2+ phosphor is co-doped with Ce3+ ions, photoluminescence, afterglow and mechanoluminescence intensity was strongly enhanced. Ca2MgSi2O7:Eu2+ showed some afterglow with a short persist time. On incorporation of Ce3+, efficient energy transfer from Ce3+ to Eu2+ was found and the emission intensity of Eu2+ was enhanced. The mechanoluminescence intensities of Ca2MgSi2O7:Ce3+, Ca2MgSi2O7:Eu2+ and Ca2MgSi2O7:Eu2+,Ce3+ phosphors increased proportionally increased with the increase in impact velocity, which suggests that these phosphors can be used as sensors to detect stress in an object.
Datum: 29.05.2017

A naphthalene derivative as ‘turn-on’ fluorescent chemosensor for the highly selective and sensitive detection of Al3+

A Schiff base compound derived from naphthalene has been synthesized and characterized as an Al3+-selective fluorescent probe. The chemosensor (L) exhibits high selectively for Al3+ in aqueous solution, even in the presence of biologically relevant cations such as Na+, K+, Ca2+, Mg2+, Pb2+ and several transition metal ions. There was no observed interference from anions like Br−, Cl−, HSO3−, SO32−, S2O32−, NO2−, CO32− and AC−. The lowest detection limit for the chemosensor L was found to be 1.89 × 10−8 M with a linear response towards Al3+ over a concentration range of 5 × 10−6 to 4 × 10−5 M. Furthermore, the proposed chemosensor has been used for imaging of Al3+ in two different types of cells with satisfying results, which further demonstrates its value for practical application in biological systems.
Datum: 23.05.2017

A novel chemiluminescence sensor for the determination of indomethacin based on sulfur and nitrogen co-doped carbon quantum dot–KMnO4 reaction

We report on a simple and sensitive sulfur and nitrogen co-doped carbon quantum dot (S,N-CQD)-based chemiluminescence (CL) sensor for the determination of indomethacin. S,N-CQDs were prepared by a hydrothermal method and characterized by fluorescence spectra, Fourier transform infrared spectroscopy and transmission electron microscopy. To obtain the best CL system for determination of indomethacin, the reaction of S,N-CQDs with some common oxidants was studied. Among the tested systems, the S,N-CQD–KMnO4 reaction showed the highest sensitivity for the detection of indomethacin. Under optimum conditions, the calibration plot was linear over a concentration range of 0.1–1.5 mg L−1, with a limit of detection (3σ) of 65 μg L−1. The method was applied to the determination of indomethacin in environmental and biological samples with satisfactory results.
Datum: 19.05.2017

A highly sensitive resonance Rayleigh scattering and colorimetric assay for the recognition of propranolol in β-adrenergic blocker

In this work, a highly sensitive, citrate anion-capped gold nanoparticles (AuNPs)-based assay for the determination of propranolol in real samples with resonance Rayleigh scattering (RRS) and colorimetry was developed. When AuNPs were prepared by the sodium citrate reduction method, citrate anions self-assembled on the surface of AuNPs to form supramolecular complex anions. In BR 4.6 buffer solution, propranolol was positively charged and could bind with AuNPs to form larger aggregates through electrostatic force and hydrophobic effects. This results in remarkable enhancement of the RRS intensity and a color change in the AuNPs solution from red to blue via purple. Thus, a highly sensitive RRS and colorimetric assay the for detection of propranolol was developed with a linear range of 0.2–5.2 and 8–112 ng/ml, respectively. In addition, no difference was seen when comparing R-propranolol with S-propranolol, therefore, this method could not be used in the recognition of chiral propranolol. However, upon addition of other β-adrenergic blockers, no phenomenon like that seen with propranolol was observed, meaning that this method can be used for determining the presence of propranolol in a mixture β-adrenergic blockers. Finally, the optimum conditions, factors influencing the reaction, its mechanism and the reasons for enhancement of the RRS were discussed.
Datum: 19.05.2017

Interaction studies of copper complex containing food additive carmoisine dye with human serum albumin (HSA): Spectroscopic investigations

In this study, the interaction between human serum albumin (HSA) and a copper complex of carmoisine dye; [Cu(carmoisine)2(H2O)2], was studied in vitro using multi-spectroscopic methods. It was found that the intrinsic fluorescence of HSA was quenched by the addition of the [Cu(carmoisine)2(H2O)2] complex and the quenching mechanism was considered as static quenching by formation of a [Cu(carmoisine)2(H2O)2]–HSA complex. The binding constant was about 104 M−1 at room temperature. The values of the calculated thermodynamic parameters (ΔH < 0 and ΔS > 0) suggested that both hydrogen bonds and the hydrophobic interactions were involved in the binding process. The site marker competitive experiments revealed that the binding of [Cu(carmoisine)2(H2O)2] to HSA primarily occurred in subdomain IIIA (site II) of HSA. The results of circular dichroism (CD) and UV–vis spectroscopy showed that the micro-environment of amino acid residues and the conformation of HSA were changed after addition of the [Cu(carmoisine)2(H2O)2] complex. Finally, the binding of the [Cu(carmoisine)2(H2O)2] complex to HSA was modelled by a molecular docking method. Excellent agreement was obtained between the experimental and theoretical results with respect to the binding forces and binding constant.
Datum: 19.05.2017

Spectrofluorometric determination of clonazepam in dosage forms: Application to content uniformity testing and human plasma

The present paper describes a developed and validated simple, highly sensitive and cost-effective spectrofluorometric method for determination of clonazepam (CNP). The proposed method depends on forming a highly fluorescent product through the reduction of CNP with Zn/HCl. The produced fluorophore exhibits a strong fluorescence at λem 350 nm after excitation at λex 250 nm. The use of carboxymethylcellulose (CMC) greatly enhanced the fluorescence intensity of the produced fluorophore to the extent of about 100%. Calibration curve showed good linear regression (r2 > 0.9998) within test ranges of 20–400 ng ml−1 with a lower detection limit of 0.67 ng ml−1 and lower quantification limit of 2.22 ng ml−1 upon using CMC. The method was successfully applied to the analysis of CNP in its pharmaceutical formulations and the results were in agreement with those obtained using a reference method. Furthermore, the content uniformity testing of the tablets was also performed. The application of the proposed method was extended to determine CNP in spiked human plasma sample as a preliminary investigation and the results were satisfactory.
Datum: 18.05.2017

Synthesis and multi-spectroscopic study on DNA-binding, cleavage and biological properties of M(II) complexes based on N2O2 donor Schiff base ligand

A novel Schiff base, (S,Z)-4-(methylthio)-2-((3-oxo-2,3-dihydro-1H-inden-1-ylidene)amino)butanoic acid (L) and four M(II) complexes (where M = Co, Cu, Ni and Zn) were synthesized and characterized. The DNA-binding characteristics of the complexes were investigated using various spectroscopic methods and viscosity measurements. Analysis of the results suggests that all the complexes bind to calf thymus DNA via intercalation. Among the four, Cu(II) complex was found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365 nm. These complexes also exhibit good antioxidant activities against 2,2-diphenyl-1-picrylhydrazyl radical. In vitro antibacterial and antifungal assay indicates that these complexes are good antimicrobial agents.
Datum: 18.05.2017

Novel enantioselective fluorescent sensors for tartrate anion based on acridinezswsxa

Novel chiral fluorescence sensors L-1 and D-1 incorporating N-Boc-protected alanine and acridine moieties were synthesized. The recognition ability of the sensors was studied by fluorescence titration, 1H NMR spectroscopy and density functional theory (DFT) calculations. The sensors exhibited good enantioselective fluorescent sensing ability toward enantiomers of tartrate anion for the selected carboxylate anions and formed 1: 1 complexes by multiple hydrogen bonding interactions.
Datum: 17.05.2017

Synthesis and luminescence properties of brick-shaped lanthanum–organic frameworks with mesoporous and macroporous architectures

Generally, metal–organic frameworks (MOFs) are made up from kinds of repeating microporous structure. Here, a series of Eu3+ ions activated terephthalate-based lanthanum–organic frameworks (La–MOFs) was synthesized by a hydrothermal reaction. By controlling the reaction time, we obtained some unique brick-shaped La–MOFs in a micron scale size range, and these La–MOFs showed tunable mesoporous and macroporous architectures. It is speculated that the change in the composition and structure of building units results in the formation of this mesoporous and macroporous heterogeneous architectures. Powder X-ray diffraction patterns and Eu3+ luminescence behavior support the speculation.
Datum: 17.05.2017

Luminescence, circular dichroism and in silico studies of binding interaction of synthesized naphthylchalcone derivatives with bovine serum albumin

Chalcones possess various biological properties, for example, antimicrobial, anti-inflammatory, analgesic, antimalarial, anticancer, antiprotozoal and antitubercular activity. In this study, naphthylchalcone derivatives were synthesized and characterized using 1H NMR 13C NMR, Fourier transform infrared and mass techniques. Yields for all derivatives were found to be >90%. Protein–drug interactions influence the absorption, distribution, metabolism and excretion (ADME) properties of a drug. Therefore, to establish whether the synthesized naphthylchalcone derivatives can be used as drugs, their binding interaction toward a serum protein (bovine serum albumin) was investigated using fluorescence, circular dichroism and molecular docking techniques under physiological conditions. Fluorescence quenching of the protein in the presence of naphthylchalcone derivatives, and other derived parameters such as association constants, number of binding sites and static quenching involving confirmed non-covalent binding interactions in the protein–ligand complex were observed. Circular dichroism clearly showed changes in the secondary structure of the protein in the presence of naphthylchalcones, indicating binding between the derivatives and the serum protein. Molecular modelling further confirmed the binding mode of naphthylchalcone derivatives in bovine serum albumin. A site-specific molecular docking study of naphthylchalcone derivatives with serum albumin showed that binding took place primarily in the aromatic low helix and then in subdomain II. The dominance of hydrophobic, hydrophilic and hydrogen bonding was clearly visible and was responsible for stabilization of the complex.
Datum: 17.05.2017

A porphyrin-based fluorescence method for zinc determination in commercial propolis extracts without sample pretreatment

The quantification of zinc in over-the–counter drugs as commercial propolis extracts by molecular fluorescence technique using meso-tetrakis(4-carboxyphenyl)porphyrin (H2TCPP4) was developed for the first time. The calibration curve is linear from 6.60 to 100 nmol L−1 of Zn2+. The detection and quantification limits were 6.22 nmol L−1 and 19.0 nmol L−1, respectively. The reproducibility and repeatability calculated as the percentage variation of slopes of seven calibration curves were 6.75% and 4.61%, respectively. Commercial propolis extract samples from four Brazilian states were analyzed and the results (0.329–0.797 mg/100 mL) obtained with this method are in good agreement with that obtained with the Atomic Absorption Spectroscopy (AAS) technique. The method is simple, fast, of low cost and allows the analysis of the samples without pretreatment. Moreover the major advantage is that Zn-porphyrin complex presents fluorescent characteristic promoting the selectivity and sensitivity of the method.
Datum: 17.05.2017

Tuneable luminescence properties of EDTA-assisted ZnS:Mn nanocrystals from a yellow-orange to a red emission band

Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn2+ ions by a wet chemical route stabilized by ethylenediamine tetra-acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)–visible light and photoluminescence (PL) studies. These results showed the presence of cubic phase and spherically shaped nanocrystals. A blue shift with respect to their bulk counterpart was observed. PL emission spectra were observed with a fixed blue peak and the yellow-orange bands were red shifted towards the red region under the same excitation wavelength. The orange-red bands were attributed to the radiation transition of electrons in 3d5 unfilled shells of Mn2+ ions [4T1(4G)-6A1(6S)]; the ZnS matrix varied with Mn2+ concentration. Shift and increase in the intensity of the PL and absorption bands were observed with increase in Mn content. The study showed that Mn2+-doped ZnS nanocrystal emission bands can be tuned from the yellow-orange to the red regions under a controlled synthesis process and could be used as promising luminescent emitters in the biology field upon functionalization with suitable materials. Further studies on construction with various other materials will be useful for practical applications.
Datum: 17.05.2017

Influence of quercetin on the interaction of gliclazide with human serum albumin – spectroscopic and docking approaches

Protein-binding interactions are displacement reactions which have been implicated as the causative mechanisms in many drug–drug interactions. Thus, the aim of presented study was to analyse human serum albumin-binding displacement interaction between two ligands, hypoglycaemic drug gliclazide and widely distributed plant flavonoid quercetin. Fluorescence analysis was used in order to investigate the effect of substances on intrinsic fluorescence of human serum albumin (HSA) and to define binding and quenching properties of ligand–albumin complexes in binary and ternary systems, respectively. Both ligands showed the ability to bind to HSA, although to a different extent. The displacement effect of one ligand from HSA by the other one has been described on the basis of the quenching curves and binding constants comparison for the binary and ternary systems. According to the fluorescence data analysis, gliclazide presents a substance with a lower binding capacity towards HSA compared with quercetin. Results also showed that the presence of quercetin hindered the interaction between HSA and gliclazide, as the binding constant for gliclazide in the ternary system was remarkably lower compared with the binary system. This finding indicates a possibility for an increase in the non-bound fraction of gliclazide which can lead to its more significant hypoglycaemic effect. Additionally, secondary and tertiary structure conformational alterations of HSA upon binding of both ligands were investigated using synchronous fluorescence, circular dichroism and FT-IR. Experimental data were complemented with molecular docking studies. Obtained results provide beneficial information about possible interference upon simultaneous co-administration of the food/dietary supplement and drug.
Datum: 17.05.2017

Photoluminescent properties of novel design heteroleptic Zn(II) complexes

Three novel heteroleptic Zn(II) complexes containing 8-hydroxy quinoline and various pyrazolone-based derivatives were synthesized and their structures confirmed by 1H–nuclear magnetic resonance, mass spectrometry, Fourier transform infra-red spectroscopy, UV–vis analysis and element analysis. All three complexes showed good photoluminescence properties in the solid state and in solution in the maximum emission range from 475 to 490 nm with a quantum yield of 0.45 to 0.51. Absorption spectra revealed that the complexes possessed a maximum absorption range of 272–281 nm with a band gap of 2.59–2.68 eV. The highest occupied molecular orbital and lowest unoccupied molecular orbital of all the complexes were determine by cyclic voltammetry. All complexes displayed high thermal stability. These characteristics were assessed to find suitability for an alternative cheap light emitter for organic light-emitting diodes.
Datum: 17.05.2017

Chemiluminescence detection of trace iodide with flow injection analysis of KMnO4-carbon dots system

Ultra-weak chemiluminescence (CL) from the reaction of iodide and KMnO4 was strongly enhanced by carbon nanodots (CNDs) in an acidic medium. The CL intensity was directly proportional to the concentration of iodide in the solution. Therefore, a flow-injection CL system with high sensitivity, selectivity and reproducibility is proposed for the determination of iodide. The proposed method exhibited advantages over a linear range of 3.0 × 10−6–1.0 × 10−4 mol/L and had a detection limit of 3.5 × 10−7 mol/L. The method was successfully applied to the evaluation of iodide in food samples with recoveries of between 96 and 103%. The relative standard deviations were 2.1 and 4.1% for intra- and inter-assay precision, respectively.
Datum: 17.05.2017

Thermoluminescence properties of Eu-doped and Eu/Dy-codoped Sr2Al2SiO7 phosphors

We report the thermoluminescence properties of Sr1.96Al2SiO7:Eu0.04 and Sr1.92Al2SiO7:Eu0.04Dy0.04 phosphors. These phosphors were prepared by a high-temperature solid-state reaction method. The prepared phosphors were characterized by X-ray diffraction. A 254 nm source was used for ultraviolet (UV) irradiation and a 60Co source was used for γ-irradiation. The effect of heating rate and UV-exposure were examined. The thermoluminescence temperature shifts to higher values with increasing heating rate and thermoluminescence intensity increases with increasing UV exposure time. The trapping parameters such as activation energy (E), order of kinetics and frequency factor (s) were calculated by peak shape method. The effect of γ- and UV-irradiation on thermoluminescence studies was also examined.
Datum: 15.05.2017

Effect of TiO2 nanoparticles on some photophysical characteristics of ketocyanine dyes

The effect of titanium dioxide (TiO2) nanoparticles (NPs) on photophysical characteristics of 2,5-di[(E)-1-(4-dimethylaminophenyl) methylidine]-1-cyclopentanone (2,5-DMAPMC) and 2,5-di[(E)-1-(4-diethylaminophenyl)methylidine]-1-cyclopentanone (2,5-DEAPMC) ketocyanine dyes has been studied using absorption, steady-state and time-resolved fluorescence spectroscopy. The magnitudes of association constants determined based on modified absorption spectrum of dyes due to the presence of TiO2 NPs indicate the interaction of TiO2 NPs with dye molecules. The quenching of fluorescence intensity of dyes by TiO2 NPs is observed and it follows linear Stern-Volmer (S-V) equation. The magnitude of quenching rate parameter suggests the involvement of static quenching mechanism. The involvement of electron transfer process in reducing fluorescence intensity of dyes has been discussed. Also, varying influence of TiO2 NPs on two dyes is explained based on the presence of different alkyl substituent in two dyes.
Datum: 12.05.2017

Highly sensitive HPLC method for the determination of galantamine in human plasma and urine through derivatization with dansyl chloride using fluorescence detector

A new method based on fluorescence derivatization with 5-(dimethylamino) naphthalene-1-sulfonyl chloride (dansyl chloride) was developed for the quantitative determination of galantamine in human plasma and urine using high-performance liquid chromatography. The reaction between galantamine and dansyl chloride was optimally realized in 30 min at room temperature and pH 10.5, with a reagent to galantamine molar ratio of 2.13. The derivative was extracted with dichloromethane, and the extract was dried under a nitrogen stream and dissolved in the mobile phase. Chromatographic analysis was performed with an Inertsil C18 column and a mobile phase comprising 40% acetonitrile and 60% 10 mM o-phosphoric acid, 1.2 ml/min. The injection volume was 20 μl. The derivatives were detected with a fluorescence detector (excitation 375 nm/emission 537 nm). The retention time for the dansyl derivative of galantamine was 16.8 min. Linearity was observed between 125 and 2000 ng/ml in water, urine and plasma. The limit of detection and limit of quantification for the developed method were 6.27–70.99 and 18.81–212.97 ng/ml, respectively. Per cent recovery was calculated as 95.15 for urine and 95.78 for plasma. Interday repeatability values for urine and plasma samples (n = 6) at three different concentrations were calculated as a per cent relative standard deviation of 0.24–0.59 and 0.35–0.56. The corresponding per cent relative standard deviation values for intraday repeatability were 0.13–0.51 and 0.04–0.15, respectively.
Datum: 21.04.2017

Pyrophosphate as substrate for alkaline phosphatase activity: A convenient flow-injection chemiluminescence assay

A sensitive and convenient flow-injection chemiluminescence (FI-CL) turn-on assay for alkaline phosphatase (ALP) activity without any label and synthesis is developed. Cu2+ can catalyze the luminol–H2O2 CL reaction. Pyrophosphate (PPi) can chelate Cu2+ and therefore the Cu2+-mediated luminol-H2O2 CL reaction is inhibited. The addition of ALP can catalyze the hydrolysis of PPi into phosphate ions, Cu2+ is released and the chemiluminescence recovers. A detection limit of 1 mU/mL ALP is obtained.
Datum: 21.04.2017

Quantum dots-based fluorescence resonance energy transfer biosensor for monitoring cell apoptosis

The development of advanced methods for accurately monitoring cell apoptosis has extensive significance in the diagnostic and pharmaceutical fields. In this study, we developed a rapid, sensitive and selective approach for the detection of cell apoptosis by combining the site-specific recognition and cleavage of the DEVD–peptide with quantum dots (QDs)-based fluorescence resonance energy transfer (FRET). Firstly, biotin-peptide was conjugated on the surface of AuNPs to form AuNPs-pep through the formation of an Au-S bond. Then, AuNPs–pep–QDs nanoprobe was obtained through the connection between AuNPs–pep and QDs. FRET is on and the fluorescence of QDs is quenched at this point. The evidence of UV–vis spectra, transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy revealed that the connection was successful. Upon the addition of apoptosis cell lysis solution, peptide was cleaved by caspase-3, and AuNPs was dissociated from the QDs. At this time, FRET is off, and thus the QDs fluorescence was recovered. The experimental conditions were optimized in terms of ratio of peptide to AuNPs, buffer solution, and the temperature of conjugation and enzyme reaction. The biosensor was successfully applied to distinguishing apoptosis cells and normal cells within 2 h. This study demonstrated that the biosensor could be utilized to evaluate anticancer drugs.
Datum: 19.04.2017

Chiral determination of cinchonine using an electrochemiluminescent sensor with molecularly imprinted membrane on the surfaces of magnetic particles

A novel molecular imprinting electrochemiluminescence sensor for detecting chiral cinchonine molecules was developed with a molecularly imprinted polymer membrane on the surfaces of magnetic microspheres. Fe3O4@Au nanoparticles modified with 6-mercapto-beta-cyclodextrin were used as a carrier, cinchonine as a template molecule, methacrylic acid as a functional monomer and N,N′-methylenebisacrylamide as a cross-linking agent. Cinchonine was specifically recognized by the 6-mercapto-beta-cyclodextrin functional molecularly imprinted polymer and detected based on enhancement of the electrochemiluminescence intensity caused by the reaction of tertiary amino structures of cinchonine molecules with Ru(bpy)32+. Cinchonine concentrations of 1 × 10−10 to 4 × 10−7 mol/L showed a good linear relationship with changes of the electrochemiluminescence intensity, and the detection limit of the sensor was 3.13 × 10−11 mol/L. The sensor has high sensitivity and selectivity, and is easy to renew. It was designed for detecting serum samples, with recovery rates of 98.2% to 107.6%.
Datum: 19.04.2017

Optical properties of Eu2+/Eu3+ mixed valence phosphor Ca2SiO2F2:Eu2+/Eu3+

The Eu2+/Eu3+ mixed valence phosphor Ca2SiO2F2:Eu2+/Eu3+ was prepared using a solid-state reaction synthesis method in a CO atmosphere, and the optical properties were investigated. The spectroscopic properties revealed that Ca2+ ions were occupied by both Eu2+ and Eu3+ ions in Ca2SiO2F2, and both ions were able to generate their characteristic emissions. A broad 5d  4f Eu2+ band at ~470 nm and narrow 4f  4f Eu3+ peaks upon excitation with n-UV light were observed. The ratio between Eu2+ and Eu3+ emissions changed regularly, and the relative intensity of the red component from Eu3+ became systematically stronger with increasing overall Eu content. As a result, the emission color of these phosphors can be tunable from blue to pink under n-UV light excitation.
Datum: 19.04.2017

Blue organic light-emitting diodes based on fluorene-bridged quinazoline and quinoxaline derivatives

Two blue emitters based on fluorene-bridged quinazoline and quinoxaline derivatives were prepared via the Suzuki reaction. Their photoluminescent properties were investigated. Furthermore, theoretical studies on these materials using the density functional theory calculation were conducted. To explore their electroluminescent properties, multilayered organic light-emitting diodes were fabricated with the following device structure: indium–tin–oxide (180 nm)/4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (50 nm)/blue emitting materials (1 and 2) (30 nm)/bathophenanthroline (35 nm)/8-hydroxy-quinolinato lithium (2 nm)/Al (100 nm). Two devices showed efficient blue emission with the external quantum efficiencies of 1.58% and 1.30%, respectively, at 20 mA/cm2, and Commission Internationale dÉclairage coordinates of (0.18, 0.24) and (0.19, 0.27) at 6.0 V. These results suggest that the self-aggregation properties of emitters would have considerable effects on their photoluminescent and electroluminescent properties.
Datum: 19.04.2017

Enhanced chemiluminescence for trazodone trace analysis based on acidic permanganate oxidation in concurrent presence of rhodamine 6G

A new sensitized chemiluminescence method by acidic permanganate oxidation was developed for the sensitive determination of trazodone. A fluorescent dye as used rhodamine 6G to increase a chemiluminescence intensity. Under optimum conditions, the liner range of the calibration curve was obtained for 1–5000 nmol/L. The limit of detection was calculated from 3σ of a blank was 0.23 nmol/L. The coexistent ions and substances had no interference with the chemiluminescence measurement. The chemiluminescence spectra were measured to elucidate a possible mechanism for the system. The present method was satisfactorily used in the determination of the drugs in pharmaceutical samples and animal serums.
Datum: 19.04.2017

CdSe and CdSe/CdS core–shell QDs: New approach for synthesis, investigating optical properties and application in pollutant degradation

In this work, CdSe quantum dots (QDs) were synthesized by a simple and rapid microwave activated approach using CdSO4, Na2SeO3 as precursors and thioglycolic acid (TGA) as capping agent molecule. A novel photochemical approach was introduced for the growth of CdS QDs and this approach was used to grow a CdS shell around CdSe cores for the formation of a CdSe/CdS core–shell structure. The core–shells were structurally verified using X-ray diffraction, transmission electron microscopy and FTIR (Fourier-transform infrared (FTIR)) spectroscopy. The optical properties of the samples were examined by means of UV–Vis and photoluminescence (PL) spectroscopy. It was found that CdS QDs emit a broad band white luminescence between 400 to 700 nm with a peak located at about 510 nm. CdSe QDs emission contained a broad band resulting from trap states between 450 to 800 nm with a peak located at 600 nm. After CdS shell growth, trap states emission was considerably quenched and a near band edge emission was appeared about 480 nm. Optical studies revealed that the core–shell QDs possess strong ultraviolet (UV) − visible light photocatalytic activity. CdSe/CdS core–shell QDs, showed an enhancement in photodegradation of Methyl orange (MO) compared with CdSe QDs.
Datum: 05.04.2017

Luminescence properties of Ce3+ in orthosilicate oxyapatite NaY9(SiO4)6O2

Ce3+-doped orthosilicate oxyapatite NaY9(SiO4)6O2 phosphors NaY9–x(SiO4)6O2:xCe3+ were prepared by a conventional high-temperature solid-state reaction method, and their spectroscopic characteristics were systematically investigated. The occupancies of Ce3+ ions at two different sites (Wyckoff 6 h and 4f sites) in NaY9(SiO4)6O2 were determined. The influence of doping concentration on the emission intensity of Ce3+ was investigated and the critical distance Rc was estimated in terms of the concentration quenching data.
Datum: 05.04.2017

Micelle-enhanced direct spectrofluorimetric method for the determination of linifanib: Application to stability studies

A new simple stability-indicating spectrofluorimetric method has been developed and validated for the determination of the tyrosine kinase inhibitor, linifanib (LNF). The proposed method makes use of the native fluorescence characteristics of LNF in a micellar system. Compared with aqueous solutions, the fluorescence intensity of LNF was greatly enhanced upon the addition of Tween-80. The relative fluorescence intensity of LNF was measured in a diluting solvent composed of 2% Tween-80: phosphate buffer pH 8.0 (20: 80, v/v) using excitation and emission wavelengths of 290 and 450 nm, respectively. The proposed method was fully validated as per the ICH guidelines. The recorded fluorescence intensity of LNF was rectilinear over a concentration range of 0.3–2 μg/ml with a high correlation coefficient (r = 0.9990) and low limits of detection (0.091 μg/ml) and quantitation (0.275 μg/ml). The applicability of the method was extended to study the inherent stability of LNF under different stress degradation conditions including, alkaline, acidic, oxidative, photolytic and thermal degradation. Moreover, the method was utilized to study the kinetics of the alkaline and oxidative degradation of LNF. The pseudo-first order rate constants and half-lives were calculated.
Datum: 05.04.2017

Interaction between azo dye Acid Red 14 and pepsin by multispectral methods and docking studies

The interaction of synthetic azo dye Acid Red 14 with pepsin was studied by fluorescence spectroscopy, UV–vis spectroscopy, circular dichroism and molecular docking. Results from the fluorescence spectroscopy show that Acid Red 14 has a strong capability to quench the intrinsic fluorescence of pepsin with static quenching. Binding constant, number of the binding sites and thermodynamic parameters were measured at different temperatures. The result indicates that Acid Red 14 interact with pepsin spontaneously by hydrogen bonding and van der Waals interactions. Three-dimensional fluorescence spectra and circular dichroism spectra reveal that Acid Red 14 could slightly change the structure of pepsin. The hydrogen bond is formed between Acid Red 14 and Tyr-189 and Thr-218 residues of pepsin. Furthermore, the binding between Acid Red 14 and pepsin inhibits pepsin activity. The study can provide a way to analyze the biological safety of Acid Red 14 on digestive proteases or other proteins.
Datum: 05.04.2017

Differentiation between sources of mechanoluminescence and acoustic emission in impact-loaded ZnSe and ZnS ceramics

Ductile semiconductor ceramics ZnSe and ZnS were damaged by a falling weight, and the time series of mechanoluminescence (ML) and acoustic emission (AE) pulses were recorded with the nanosecond resolution. The ML lighting appeared in the instance of shock but the AE generation emerged with a delay of 50–100 μsec; however, the maxima of the light and sound emissions coincided in time. This difference in temporal profiles was explained by the difference in prevailing sources of emissions of two types. The detected luminescence in A2B6 compounds was excited, mainly, by moving and multiplying dislocations, while the sound was generated by nucleating and growing cracks. The statistical analysis showed that at the stage of pre-failure deformation, the ensemble of dislocations exhibited a trend to self-organizing; the cracking was fully random. The effect of intergranular boundaries on the dislocation motion manifested itself in the statistics of mechanoluminescence generation.
Datum: 10.03.2017

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