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.

Ultrafast Fluorescence Quenching in LnFe(CN)_6·4H_2O

对ＬｎＦｅ（ＣＮ）６·４Ｈ２Ｏ（Ｌｎ＝Ｅｕ，Ｔｂ）体系的吸收光谱和荧光光谱的研究表明，两配合物的中Ｅｕ３＋和Ｔｂ３＋离子的荧光发生强烈猝灭，即使是用高功率激光直接激发Ｅｕ３＋的７Ｆ０→５Ｄ０跃迁也是如此，表明该体系中稀土离子的荧光寿命非常短，有可能满足室温超快相干控制的要求．

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.

FLUORESCENCE AND ITS ENHANCEMENT OR QUENCHING OF Eu(TTA)_3 Phen LB FILMS

For the first time, LB films containing Eu(TTA)3Phen are obtained by using composite subphase. Eu(TTA)3Phen itself is dimcult to be transferred onto solid substrate.mixed or alternate LB films are prepared. Hydrogen bonds form between Eu(TTA)3Phen and AA or TPP(-COOH). TOPO and SB have a fluorcscence enhanGement effect on Eu(TTA)3Phen. TPP(-COOH) and Fc have a fluorescence quenching effect on it.

STUDY ON THE SOLUTION FLUORESCENCE QUENCHING FOR POLYSILANES

he solutionfluorescence quenching mechanisms of poly(methylcyclohexylsilane),poly(methylphenethylsilane), poly(methylcyclohexylsilanecomethylphenethylsilane) and poly(methylphenylsilane) are studied by means of steadystate fluorescence,timeresolved fluorescence and UV absorption. The results show that the fluorescence quenching for polysilanes by carbon tetrachloride is the static quenching with energy migration, which is also supported by the qualitative results of the fluorescence quenching behaviors of polysilane by nitromethane (CH3NO2) and 2, 4, 7trinitrofluorenone(TNF).

Interaction between Humic Acid and p-Arsanilic Acid Using Fluorescence Quenching Approach

P-arsanilic acid(p-ASA),as a kind of organoarsenic feed additive,has been widely used in poultry and swine breeding.However,it has caused the arsenic pollution around the farm.Currently data shows humic acid(HA)is closely to the migration and transformation of p-ASA.Therefore,the interaction between p-ASA and HA was investigated by using the method of fluorescence quenching titration.The association constant changed from2.74 to 4.88 L·mol-1at a p H varying from 5 to 9 and reached the maximum at p H 7.In addition,log K varied from4.15 to 5.02 L·mol-1when the temperature increased from 15℃to 35℃.The log K increased with an increase in the concentration of HA.The dominant mechanism between p-ASA and HA is static quenching.The primary interaction force was likely the hydrogen bond,and the binding behavior occurred on the As-O stretch of p-ASA and the carboxylic acid C=O stretch of HA.The results showed that dissolved organic matters could affect the fate and biogeochemical cycling of organoarsenic pharmaceuticals in aquatic ecosystems.

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.

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.

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.

Study on State of Terbium Ion in Liposome by One order Derivative Fluorescence Quenching Method

The state of Tb3+ is investigated in liposome. When the concentration of PC is below CMC (critical micell concentration), most of Tb3+ is associated with PC, the binding constant is about 3.35×103 L/mol. When the concentration of PC is beyond CMC, most of Tb3+ is dimerized, the dimerization constant is about 3.92×104L/mol. In PC?CH?H2O system, the binding constant of Tb3+?CH complex 2.93×104L/mol is obtained.

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.

Interaction of 4-aminosalicylic Acid and Surfactants in Aqueous Solutions Using UV-Vis Spectra and Steady-state Fluorescence Spectroscopy

The interactions of 4-aminosalicylic acid （4-ASA） and surfactants in aqueous solutions were investigated by using UV-Vis spectra and steady-state fluorescence spectroscopy.The results showed that the strongest peak at UV-vis spectra of 4-ASA aqueous solution in the presence of cationic surfactant and cetyltrimethyl ammonium bromide （CTAB） appeared at 206 nm and took a red shift from 206 nm to 221 nm with the increase of 4-ASA concentrations from 0.8×10-5 to 4.4×10-4 mol/L.Similarly,the strongest peak at UV-vis spectra of 4-ASA aqueous solution in the presence of nonionic surfactant and polyvinylpyrrolidone （PVP） appeared at 206 nm and took a red shift from 206 nm to 219 nm with the increase of 4-ASA concentrations from 0.8×10-5 to 4.4×10-4 mol/L.However,the similar phenomena did not appeared in the presence of anion surfactant,sodium dodecyl sulfate （SDS）,the UV-vis spectra of 4-ASA aqueous solution remained the same peak position and the peak value increased with the 4-ASA concentration increase.The results could be attributed to the electrostatic attraction between 4-ASA and CTAB or PVP,as well as the electrostatic repulsion between 4-ASA and SDS.Furthermore,the value of critical micelle concentration （CMC） of surfactants in the presence of 4-ASA was determined with Fluorescence method.The first and second CMC of CTAB was 1.2×10-4 M and 2.4×10-4 M,respectively.The first and second CMC of PVP was 1.2×10-4 M and 2.8×10-4 M.SDS realized the multiple micellizations to form multiple CMC.

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.

On the Question of Defining the Association Constants by the Method of Fluorescence Quenching

A study is made on the previously ignored problem of the dependence of a static fluorescence quenching Stern-Volmer constant?Ksv on the initial concentration of [F]0 fluorophore F. This correlation is shown to exist. It is concluded that the Stern-Volmer quenching constant may be used as association constant K only with .

The Analysis of the Quenching Efficiency of Humic Acid Fluorescence by Cadmium and Copper Ions

In conditions of monochromatic excitation (λexc=337.1), the spectral dependence of the efficiency of fluorescence quenching αλ of humic acids samples by Cd2+ and Cu2+ ions was studied. The difference of αλ dependencies for these ions was established. In the spectral range 350 - 650 nm, changes of the αλ for Cd2+ ion are markedly different from the magnitude for changes αλ, which occur for ion Cu2+. The interpretation of mismatch dependences obtained αλ ions Cd2+ and Cu2+ is carried out within the concept of the availability of different sites, due to the difference in ionic radii (0.108 nm and 0.08 nm for Cd2+ and Cu2+, respectively).

Determination of Bisoprolol Fumarate by Fluorescence Quenching Method

[Objectives]To establish a new method for indirect determination of bisoprolol fumarate based on fluorescence quenching technology.[Methods]In ammonia water and ammonium chloride buffer solution at pH=9.2,whenλexcitation=277 nm andλemission=596 nm,with the increase of CCu2+,the fluorescence signal intensity of bisoprolol fumarate weakened,and the difference between the fluorescence intensity of bisoprolol fumarate itself and the fluorescence intensity of the test solution after the quencher Cu2+was added(ΔF)and Cbisoprolol fumarate showed a good linear relationship.[Results]In the range of 15.39-76.93μg/mL,ΔF=146.7 Cbisoprolol fumarate+482.1,r=0.9988,and the detection limit is 0.1391μg/mL.[Conclusions]The fluorescence quenching method has been applied to the determination of actual samples with a recovery rate of 99.9%and an RSD of 2.7%.The results are satisfactory.