Fluorescence quenching method for the determination of catechol with gold nanoparticles and tyrosinase hybrid system

The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produced...

Fluorescence Quenching of a Novel Eu(Ⅲ) Coordination Compound for the Detection of Trace Amounts of Water： Synthesis, Structure and Photoluminescent Property

A novel luminescent coordination compound Eu（TTA）3（DEDAF）（1, TTA = 1,1,1-trifluoro-3-（2-thenoyl）acetone, DEDAF = 9,9-diethyl-4,5-diazafluoren） has been synthesized and fully characterized by infrared spectrum, elemental analysis, UV-vis spectrum, etc. X-ray single-crystal diffraction analysis reveals that compound 1 shows a mononuclear structure with the europium atom in coordinating to one DAF and three TTA ligands. The mononuclear structure units are assembled into a 3-D polymer by hydrogen bonds and π-π interactions. Photoluminescent property of 1 was investigated in detail at room temperature. Complex 1 emits strong red luminescence. However, it could be quenched even by small amount of water. The fluorescence intensity at 614 nm decreases linearly with the water content increasing（vol% in acetonitrile） in the range of 0.025~0.2% under 278 nm excitation. Thermogravimetric analysis has also been studied, which demonstrates good thermal stability of 1.

Fluorescence Quenching of Anthracene by N,N-Diethylaniline and Phenothiazine in Triton X-100/n-C_(10)H_(21) OH/H_2O Microemulsion

The photo-induced electron transfer reactions of anthracene with N,N -diethylaniline(DEA) and phenothiazine(PTZ) occur in the membrane phase of a Triton X-100/ n -C 10 H 21 OH(1-decanol)/H 2O microemulsion. DEA and PTZ exist in the membrane phase of the microemulsion. Anthracene exists in the oil continuous phase of the W/O microemulsion and in the oil core and membrane phase of the O/W microemulsion.

Spectroscopic Characterization of Eu-Enoxacin-Phen Complexes and Determination of ATP by Fluorescence Quenching

The complex of Eu 3+ and Enoxacin(ENX) and Phen was synthesized. Its compositions is Eu(ENX)_3(phen)Cl_3·2H_2O. Its fluorescence spectra were studied. The results show that the strong fluorescence emitting of 592 and 616 nm for Eu 3+ in the Eu(ENX)_3(phen)Cl_3·2H_2O complex is related to the transitions 5D_0-7F_1 and 5D_0-7F_2 respectively. A sensitive method for the determination of adenosine triphosphate(ATP) by fluorescence quenching is proposed. The method is based on the ability of ATP to inhibit the formation of a strong fluorescent complex of Eu(ENX)_3(phen)Cl_3·2H_2O. In conditions of pH 6.7 in HAc-NaAc buffer and λ_ ex=340 nm and λ_ em=616 nm, the linear range of the determination is 0.4～ 10 μg·ml -1 and the detection limit is 0.034 μg·ml -1 for ATP. The method was applied to determine ATP in adenosine disodium triphosphate injection samples with relative standard deviation of 212% and recovery of 94.8%～1037%.

Synthesis and Fluorescence of Eu-Ibuprofenum-Phen Complex and Determination of ATP by Fluorescence Quenching of Complex

The complex Eu(IB)_3(phen)·2H_2O was synthesized. The results show that the strong fluorescence emitting of 593 and 615 nm for Eu^(3+) in the Eu(IB)_3(phen) complex is related to the transitions (()~5D_0-()~7F_1) and (()~5D_0-()~7F_2,) respectively. A sensitive method for the determination of adenosine disodium triphosphate (ATP) by fluorescence quenching is proposed. The method is based on the ability of ATP to inhibit the formation of a strong fluorescent complex of Eu(IB)_3(phen). In conditions of pH 6.7 HAc-NaAc buffer, λ_(ex)=273 nm and λ_(em)=615 nm, the linear range of the determination was 0.1～10 μg·ml^(-1) and the detection limit was 0.03 μg·ml^(-1) for ATP. The method has been applied to determine ATP in adenosine disodium triphosphate tablets samples with relative standard deviation of 2.18% and recovery of (98.4%～)104.0%.

Aggregation-dependence of Optical Properties and Fluorescence Quenching of a Water-soluble Poly(phenylene ethynylene)

The solvent and surfactant-dependent aggregation behaviors of the anionic poly（phenylene ethynylene） were studied and used to tune optical properties and fluorescence quenching efficiency.

Mechanisms of Fluorescence Quenching of Pr^(3+)-Doped PbWO_4 Crystal

Fluorescence decay curves of the ^3P0 and ^1D2 manifolds in Pr^3＋ doped PbWO4 crystal were measured at room temperature and fluorescence lifetimes of both manifolds were estimated. Combining with the radiative lifetimes of the manifolds calculated on the basis of the modified J-O theory, the main mechanisms for the fluorescence quenching of the manifolds were analyzed. The multi-phonon relaxation and the cross-relaxation energy transfer are the major reasons for the fluorescence quenching of the ^3P0 and ^1D2 manifolds, respectively. The Inokuti-Hirayama model was used to analyze the fluorescence decay curve of the ^1D2 manifold and the cross-relaxation of dlpole-dipole interaction was confirmed. Consequently, the ^3p0 manifold is more favorable as an upper laser level than the ^1D2 manifold.

Amplified Detection of Iron Ion Based on Plasmon Enhanced Fluorescence and Subsequently Fluorescence Quenching

A facile and rapid approach for detecting low concentration of iron ion(Fe3+) with improved sensitivity was developed on the basis of plasmon enhanced fluorescence and subsequently amplified fluorescence quenching.Au1Ag4@Si O2 nanoparticles were synthesized and dispersed into fluorescein isothiocyanate(FITC) solution. The fluorescence of the FITC solution was improved due to plasmon enhanced fluorescence. However, efficient fluorescence quenching of the FITC/Au1Ag4@Si O2 solution was subsequently achieved when Fe3+, with a concentration ranging from17 n M to 3.4 l M, was added into the FITC/Au1Ag4@Si O2 solution, whereas almost no fluorescence quenching was observed for pure FITC solution under the same condition. FITC/Au1Ag4@Si O2 solution shows a better sensitivity for detecting low concentration of Fe3+compared to pure FITC solution. The quantized limit of detection toward Fe3+was improved from 4.6 l M for pure FITC solution to 20 n M for FITC/Au1Ag4@Si O2 solution.

Laser-Induced Recoverable Fluorescence Quenching of Perovskite Films at a Microscopic Grain Scale

Understanding the fundamental properties of metal-halide perovskite materials is driving the development of novel optoelectronic applications.Here,we report the observation of a recoverable laser-induced fluorescence quenching phenomenon in perovskite films with a microscopic grain-scale restriction,accompanied by spectral variations.This fluorescence quenching depends on the laser intensity and the dwell time under Auger recombination dominated conditions.These features indicate that the perovskite lattice deformation may take the main responsibility for the transient and show a new aspect to understand halide perovskite photostability.We further modulate this phenomenon by adjusting the charge carrier recombination and extraction,revealing that efficient carrier transfer can improve the bleaching resistance of perovskite grains.Our results provide future opportunities to attain high-performance devices by tuning the perovskite lattice disorder and harvesting the energetic carriers.

Synthesis and Fluorescence Quenching of Copolymer Containing3, 4, 9, 10-Perylenetetracarboxyl Diimide Side Chains

A photoluminescence material, copolymer of N-vinylcarbazole (VCz) and N,N'- bisallyl-3, 4. 9, 10-ferylenetetracarboxyl diimide (APTC) chromophores P(VCz-APTC) was synthesized. The fluorescence quenching of P(VCz-APTC) by fullerene (C-60) and triethylamine was also studied.

A FLUORESCENCE QUENCHING IMNUNOASSAY METHOD FOR DETERMINATION OF TRACE ALBUMIN USING UNLABELED EUROPIUM CHELATE

A fluoroimmunoassay method using unlabeled europium chelate is described.The principle is similar to that of fluoroimmunoassay method using lanthanide chelate as labels.The procedure is simple because labeling process is omitted.The detection limit is about 10^(10) mol/L antigen.The relative standard deviation of immunoassay is less than 10%.The recoveries of human serum albumin and estradiol protein conjugate are 96-105% and 111% respectively.

Determination of heavy metal ion in landfill leachate with solvent extracting ＆ fluorescence quenching method

Add the masking agent and biscyclohexanoneoxalyldihydraone into the diluted clarificd liquid of the landfill leachate which was treatmented by digestion and centrifugal filtration to complexate all heavy metal ion in the trcatmented liquid, and extracted using CHCl3 many time, then it were demasking and decomposing respectively, and adjusted different pH and formed Me^n＋-PAN coordination compound when these metal ion reaction with PAN. The Fluoresence quenching of Rh6G （λex/λem=543mn/558nm） when the metal ion coordination compound was add into the Rh6G solution step by step, the quenching intensity was directly proportional to the concentration of the metal ion in the certain range. So a new method of fast and simple for determination of trace metal ion in landfill lcachate was established to determine metal ion in sample of different landfill leachate in Three Gorge Water Reservoir, and comparison the classic assay method with satisfactory results.

Determination of Chlorobenzene by Hydroxypropyl-β- Cyclodextrin Sensitized Fluorescence Quenching Method with Neutral Red as a Fluorescence Probe

The fluorescence quenching of inclusion complex of neutral red （NR） and hydroxypropyl-β-cyclodextrin （HP-β-CD） carried by chlorobenzene was investigated. The fluorescence intensity of NR increased due to the formed inclusion complex of HP-β-CD and NR. But the fluorescence intensity of NR-HP-β-CD diminished when chlorobenzene was added, and there was a linear relationship between the fluorescence quenching value of the system （△IF = IF, NR-HP-β-CD - IF, CB-NB-NR-HP-β-CD） and the concentration of chlorobenzene. Based on this, a novel fluorescence quenching method for the determination of chlorobenzene with NR as a fluorescence probe has been developed. Under the optimal conditions, the linear range of calibration curve for the determination of chlorobenzene was 5.0 × 10^-8 - 8.0 × 10^-6 mol/L and the detection limit was 1.0 × 10^-8 mol/L. It has been applied to determination ofchlorobenzene in synthetic waste water samples with satisfactory results.

A selective optical chemical sensor for the determination of iodine based on fluorescence quenching of LiTOE

An optical chemical sensor has been developed for the determination of iodine based on the reversible fluorescence quenching of 2, 2, 7, 7, 12, 12, 17, 17-octamethyl-21, 22, 23, 24-tetraoxaquaterene-Li （LiTOE） immobilized in a plasticized poly（vinyl chloride） （PVC） membrane. The optimum membrane of the sensor consists of 100 mg of PVC, 200 mg of bis （2-ethytbexyl） sebacate （BOS） and 3.0 mg of LiTOE. The maximum response of the optode membrane for iodine is obtained in Tris-HCl buffer solutlon （pH 8.0）. With the optimum conditions described, the proposed sensor responds linearly in the measuring range of 3.90×10^-2 to 3.90×10^-4 mol/L, and has a detection limit of 6.0×10^-8 mol/L. The response time of the sensor is less than I rain. In addition to high reproducibility and reversibility of the fluorescence signal, the sensor also exhibits good selectivity. It is not interfered by some common anions and cations. It is applied for the determination of iodine in table salt samples. The results agree with those obtained by another method.

Potassium Iodide and Acrylamide Fluorescence Quenching Studies on Gamma-Crystallins of Human Lenses in Development and Aging

γ_1-γ_2-and γ_3-crystallin(corresponding to γs-,γC-and γD- crys-tallin respectively)of human fetal,2 year and 20^+ year old lenses areseparated by Sephadex gel chromatography.lodide and acrylamide are usedto quench the tryptophane fluorescence of sub-γ-crystalline fractions and Ksvand fa values are calculated.The results show that iodide has no clear quench-ing effects on all γ-crystallins,the quenching effects of acrylamide on the tryp-tophan fluorescences of γ1-γ2-and γ3-crystallin from lenses of the ...

Pyranine Fluorescence Quenching for the Characterization of Solutions

Fluorescence quenching of pyranine by tryptophan, phenylalanine, and nicotinic acid was investigated by using steady state and time resolved fluorescence spectroscopy. On a comparative basis, nicotinic acid is a very strong quencher of pyranine fluorescence, tryptophan is a moderate quencher and phenylalanine is a weak quencher. The strong quenching is the result of the hydrogen bonding complex between pyranine and amine which existed in both tryptophan and nicotinic acid. Contact complex will form between phenylalanine and pyranine which is the reason of quenching of pyranine by phenylalanine. Associates will form in tryptophan and phenylalanine due to the zwitterion +H3NRCOO- or/and hydrogen bond. Higher concentrations favor the formation of aggregates in the supersaturated solution which made the quenching curve different from unsaturated solution dramatically.

STUDY ON THE MECHANISM OF FLUORESCENCE QUENCHING OF NITROCOMPOUNDS FOR OXAZOLES *

The mechanism of nitrocompounds quenching of the fluorescence of 5, 5′ dipheny1 2, 2′ bisoxazole (POOP) and trans 1, 2 bis [2 (5 phenyloxazolyl)] ethene (POEOP) has been studied. It was found that the fluorescence of oxazoles was quenched mainly by the absorption competition and radiationless energy transfer of nitrocompounds. The fluorescence quenching rate constants of nitrobenzene and nitromethane are 3.0×10 10 L·mol -1 ·s -1 and 1.5×10 8 L·mol -1 ·s -1 respectively for POEOP. This remarkable difference was explicated.

Biosorption of Cu（II） to extracellular polymeric substances （EPS） from Synechoeystis sp.： a fluorescence quenching study

Biosorption of extracellular polymeric substances （EPS） from Synechocystis sp. （cyanobacterium） with Cu（II） was investigated using fluorescence spectroscopy. Three fluorescence peaks were found in the excitation-emission matrix （EEM） fluorescence spectra of EPS. Fluorescence of peak A （Ex/Em = 275/452 nm） and peak C （Ex/Em= 350/452nm） were originated from humic-like substances and fluorescence of peak B （Ex/ Em= 275/338nm） was attributed to protein-like sub- stances. Fluorescence of peaks A, B, and C could be quenched by Cu（II）. The effective quenching constants （lg Ka） were 2.8-5.84 for peak A, 6.4-9.24 for peak B, and 3.48-6.68 for peak C, respectively. The values of lg Ka showed a decreasing trend with increasing temperature, indicating that the quenching processes were static in nature. The binding constants （lg Kb） followed the order of peak A 〉 peak B 〉 peak C, implying that the humic-like substances in EPS have greater Cu（II） binding capacity than the protein-like substances. The binding site number, n, in EPS-Cu（II） complexes for peaks A, B, and C was less than 1. This suggests the negative cooperativity between multiple binding sites and the presence of more than one Cu binding site.

Selective Detection of Mercury（Ⅱ） and Copper（Ⅱ） Based on the Opposite Size-dependent Fluorescence Quenching of CdTe Quantum Dots

Three different size CdTe quantum dots （QDs） capped by 3-mercaptopropionic acid （MPA） have been prepared in aqueous solutions, and their interactions with Cu^2＋ and Hg^2＋ have been investigated. The opposite size-dependent fluorescence quenching of CdTe QDs by Hg^2＋ and Cu^2＋ was observed： Hg^2＋ quenched smaller particles more efficiently than larger ones while larger particles were more markedly quenched by Cu^2＋. Based on the different size responses, Hg^2＋ and Cu^2＋ were respectively detected with high sensitivity and selectivity, for the first time, using the QDs with different sizes but the same components and capping ligands.

Selective Chemosensor of Fe3＋ Based on Fluorescence Quenching by 2,2＇-Bisbenzimidazole Derivative in Aqueous Media

2,2＇-Bisbenzimidazole derivative （L） was designed as a fluorescent chemosensor for Fe3＋. This structurally simple chemosensor displays significant fluorescence quenching with increasing concentrations of Fe3＋. L exhib- ited high selectivity and antidisturbance for Fe3＋ among environmentally relevant metal ions in aqueous media. The method of Job＇s plot indicated the formation of 1 ; 2 complex between L and Fe3＋, and the possible binding mode of the system was also proposed. In addition, further study demonstrates the detection limit on fluorescence response of the sensor to Fe3＋ is down to 10-7 mol·L-1 range. The binding mode was investigated by fluorescence spectra, ESI-MS, IR data, ^1H NMR, ^13C NMR and crystal data.