Fluorescence Quenching Studies of Curcumin by Hydrogen Peroxide in Acetonitrile Solution

Summary. Steady state quenching studies of curcumin, 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, fluorescence by hydrogen peroxide were conducted in acetonitrile solution. A quenching rate constant, k_q, of 1.05×10¹⁰M^–1·s^–1 was obtained with a short fluorescence lifetime of 347ps. The reaction rate constant, which is within the diffusion-limited regime, is activation-controlled. The rate constant of deactivation of the thermally excited curcumin was 1.2 orders of magnitude more nonradiative (2.67×10⁹s^–1) than radiative (2.16×10⁸s^–1). The reaction was exothermic with a G° of –1.97eV and solvent reorganization energy of 1.37eV. These values indicate that the electron transfer reaction is solvent-mediated with electron transfer rate constant, k_ET, of 2.16×10¹⁰s^–1.     

功能性碲化镉纳米荧光探针荧光猝灭法测定过氧化氢

用L-半胱氨酸作稳定剂制备了碲化镉量子点,并选取回流时间为21 min,具有发射波长为555 13m的量子点作为测定过氧化氢荧光探针.在pH 8.0的磷酸盐缓冲溶液中,过氧化氢与碲化镉量子点反应而使其氧化,导致其荧光的猝灭.结果显示,荧光强度的减弱程度(△F)与过氧化氢的浓度在1.0×10-7～6.0×10-5mol·L-1之间呈线性关系.此方法的检出限(3s/b)为8.0×10-8mol·L-1应用此方法测定了雨水中过氧化氢的含量,并以此样品作基体,用标准加入法进行了回收试验,测得平均回收率为99.5%.     

谷胱甘肽稳定的CdTe量子点荧光猝灭法测定痕量过氧化氢

以谷胱甘肽稳定的CdTe量子点作为荧光探针,基于荧光猝灭法对过氧化氢进行了定量检测,考察了缓冲溶液体系、量子点浓度、反应时间等多种因素的影响。实验结果表明,在pH=7.2的Na2HPO4-NaH2PO4缓冲液中,反应时间为15min,过氧化氢浓度为1.0×10-6～3.0×10-5 mol/L范围时,其线性回归方程为△F=9.78+7.56c(10-6 mol/L),线性相关系数和检测限分别为0.9992和1.27×10-8 mol/L。谷胱甘肽稳定的CdTe量子点荧光猝灭法已用于水样的测定,回收率在96%～103%之间,相对标准偏差RSD不大于3.3%,结果令人满意。     

A Fluorescence Quenching Method for the Determination of Iodide Ion with Salicylfluorone and Hydrogen Peroxide

Abstract

A highly sensitive and selective fluorescence quenching method has been developed for rapid determination of iodide ion with salicylfluorone (SAF) as fluorogenic reagent (λ_ex = 495 nm, λ_em = 520 nm) at pH 2.5-3.0. The calibration graph is linear over the range 0.05-300 μg/25 ml. The detection limit is 0.05 μ/25 ml iodide. Other halide ions do not interfere with the determination even when present in large excess. The method is rapid and was successfully applied for the determination of iodide ion in sodium chloride, table salt and low sodium salt.     

Fluorescence Quenching of Benzaldehyde in Water by Hydrogen Atom Abstraction

We computed the mechanism of fluorescence quenching of benzaldehyde in water through relaxed potential energy surface scans. Time‐dependent density functional theory calculations along the protonation coordinate from water to benzaldehyde reveal that photoexcitation to the bright ππ* (S₃) state is immediately followed by ultrafast decay to the nπ* (S₁) state. Evolving along this state, benzaldehyde (BA) abstracts a hydrogen atom, resulting in a BAH^. and OH^. radical pair. Benzaldehyde does not act as photobase in water, but abstracts a hydrogen atom from a nearby solvent molecule. The system finally decays back to the ground state by non‐radiative decay and an electron transfers back to the OH^. radical. Proton transfer from BAH⁺ to OH^? restores the initial situation, BA in water.     

Activation of Hydrogen Peroxide by Acetonitrile in the Oxidation of Thioethers: Reaction Kinetics and Mechanism

Kinetics and Catalysis - The kinetics of oxidation of diethyl sulfide (Et2S) with hydrogen peroxide (H2O2) in aqueous solutions of acetonitrile (MeCN) was studied using a kinetic distribution...     

2-氨基咪唑血红素模拟酶催化荧光光谱法测定过氧化氢

基于2-氨基咪唑血红素模拟酶催化过氧化氢氧化对甲酚的反应建立了测定过氧化氢浓度的荧光光谱法。在优化的试验条件下,过氧化氢浓度在1.02×10-8~3.07×10-5 mol·L-1范围内与体系的荧光强度呈线性关系,方法的检出限(3S/N)为8.31×10-9 mol·L-1。本方法用于雨水中过氧化氢的测定,加标回收率在95.1%~99.0%之间,测定值的相对标准偏差(n=6)在1.3%~2.5%之间。     

甲苯-乙醇介质中二茂铁催化分解过氧化氢机理的探讨

甲苯-乙醇介质中二茂铁催化分解过氧化氢机理的探讨;电子转移机理     

近红外光谱用于过氧化氢含量的定量分析研究

用长波近红外光谱仪（傅里叶变换,InGaAs检测器）和短波近红外光谱仪（光栅分光,CCD检测器）对比研究了25％～30％过氧化氢水溶液中过氧化氢含量的定量分析方法。结果表明,应用短波近红外光谱结合长光程样品池对25％-30％过氧化氢水溶液样品中过氧化氢含量进行定量分析,可以显著减少过氧化氢分解对定量分析的干扰,使定量分析的准确度和重复性显著提高。短波近红外光谱定量分析模型RMSECV和RMSEP分别为0．06和0．05;长波近红外光谱定量分析模型RMSECV和RMSEP分别为0．10和0．09。     

荧光分光光度法测定中药对过氧化氢的清除率

基于苯胺被H2O2氧化为硝基苯使其荧光猝灭的原理建立了一种测定中药对H2O2清除率的新方法。研究表明：苯胺荧光在pH7～8之间有最大强度;乙醇浓度为50%（V/V）时,瑞利散射干扰最小,荧光强度最大;苯胺浓度为110mmol/L,H2O2的浓度小于1mmol/L时,苯胺荧光猝灭程度与H2O2浓度呈线性关系,测定了中药厚朴和杜仲对H2O2的清除率,结果与鲁米诺化学发光法测定值一致。     

Determination of Fluoride by Fluorescence Quenching

Abstract

A fluorescence quenching method for the determination of fluoride ion over the concentration range from 10^?9 to 10^?6M is presented. The fluoride ion is added to the fluorescent chelate of aluminum(III) and PAN [1- (2-pyridylazo)-2-naphthol]: the fluoride preferentially complexes the aluminum (III), displacing nonfluorescent PAN. Of the anions tested as possible interferences at equimolar levels, phosphate interferred seriously and iodide interferred somewhat.     

不同供氢底物用于测定H2O2的酶催化动力学研究

研究了牛血红蛋白(hemoglobin,Hb)作为过氧化物模拟酶,以酸性铬蓝K、罗丹明B、亚甲基蓝不同供氢底物测定H2O2的酶催化反应体系的催化特性和反应条件。探讨了采用不同底物测定时的催化反应机理。用于雨水中H2O2含量的测定,结果满意。     

Kinetic Studies on Interactions of Ferreous-porphyrins with Hydrogen Peroxide

In an alkali-methanol solution, both 1- and 2-naphthol can be converted into 2-hydroxy-l,4-naphtho-quinone (HNQ) with selectivity more than 95% by H2O2 over metalloporphyrin catalyst. The UV-Vis spectra indicate that a high valence oxygen-ferreous porphyrin intermediate has been produced by addition of an aqueous solution of H2O2 into the catalytic system. This intermediate formation rate is influenced by the concentrations of low valence ferrous porphyrin H2O2, and NaOH existing in the system. With the aid of the UVVis spectrum varieties, the rate equations and formation rate constants of the intermediate at different temperatures can be determined by changing the original concentration of each reactant. The formation activation energy of this intermediate was also determined by changing temperature.     

Kinetics of Hydrogen Peroxide Decomposition in Guaiacol Solution, Catalyzed by Hexacyanoferrate(II)

The kinetics of hydrogen peroxide decomposition in a guaiacol solution, catalyzed by potassium hexacyanoferrate(II), were studied. The reaction mainly follows the pathway of guaiacol hydroxylation. The reaction order is 1 with respect to H₂O₂, 0.5 with respect to hexacyanoferrate, and from 0.4 to 0 with respect to guaiacol (the latter parameter decreases with increasing guaiacol concentration). The apparent activation energy is 105 kJ mol^{- 1}. A kinetic scheme of the process was proposed. An expression consistent with the experiment was obtained for the rate of hydrogen peroxide decomposition in the presence of guaiacol, catalyzed by hexacyanoferrate(II).     

过氧化氢溶液中单和双金属金-银纳米粒子氧化L-亮氨酸的动力学(英文)

The catalytic activity of surfactant stabilized mono-and bimetallic Au and Ag nanoparticles for the oxidation of an amino acid,L-leucine,was studied using hydrogen peroxide as the oxidant.The Au and Ag nanoparticle catalysts exhibited very good catalytic activity and the kinetics of the reaction were found to be pseudo-first order with respect to the amino acid.The effects of several factors,such as oxidant concentration,ionic strength,pH,and catalyst concentration on the reaction,were also investigated.In particular,optimal oxidant and catalyst concentrations were determined.Very high concentrations of the metal nano-catalysts or the oxidant led to a dramatic increase in reaction rate.Moreover,bimetallic Au-Ag catalysts provided higher selectivity than pure Au or Ag.     

红细胞悬液传感器的研制

以人红细胞作为过氧化氢酶的来源，用尼龙网共价键合，并与氧电极合制得过氧化氢传感器，研究了尼龙网上活化酶的固定化，测试介质等有关实验条件和参数，测得在ｐＨ８的磷酸盐缓冲溶液中，电极响应的线性范围为３×１０＾－５～３×１０＾－３ｍｏｌ／Ｌ，测定了传感器在果珍，鱼浆和磷酸盐缓冲溶液中对过氧化氢的回收率，获得满意结果。     

催化过氧化氢氧化邻苯三酚红固体基质室温燐光猝灭法测定痕量钴

基于硼砂缓冲液中聚丙烯酰胺(PAM)存在下,邻苯三酚红(PGR)于滤纸固体基质上能发射强而稳定的室温燐光,PAM可活化钴离子催化H2O2氧化PGR反应,使PGR的室温燐光猝灭,从而建立了测定痕量钴的新方法。该方法的线性范围为4.8~960(×10-18g/斑)Co2+(浓度范围0.012~2.40×10-9g/L,0.4μL/斑),工作曲线的回归方程ΔIp=12.76+0.1248 mCo2+(×10-18g/斑),n=7,相关系数r=0.9993;检出限为1.2×10-18g/斑(对应浓度为3.0×10-12g/L)。对4.8和960(×10-18g/斑)Co2+重复测定11次(0.4μL点样量),RSD分别为3.6%和4.7%。用PAM比不加PAM时ΔIp增加4.6倍。本方法灵敏、准确、简便快速、重现性好,用于党参、当归、川芎、金银花和VB12中的痕量钴测定,结果满意。     

荧光猝灭法测定磷酰化氨基酸

建立了通过磷酰化氨基酸水解产生无机磷酸盐猝灭铽离子-钛铁试剂络合物(Tb3 -TR)荧光探针的间接荧光法测定三种磷酰化氨基酸。在最佳实验条件下,方法测定磷酰化丝氨酸(P-Ser)、磷酰化苏氨酸(P-Thr)和磷酰化酪氨酸(P-Tyr)的线性范围分别为5.0×10-8~5.0×10-7mol/L、5.0×10-8~6.0×10-7mol/L、5.0×10-8~6.0×10-7mol/L;检出限分别为2.06×10-8mol/L、1.13×10-8mol/L和1.74×10-9mol/L。该方法最后用于卵黄高磷蛋白中含磷量的测定,取得定量结果。     

酪氨酸猝灭Eosin Y的荧光

氨基酸残基对探针分子的荧光猝灭行为可以为生物大分子的结构及构象动力学研究提供重要的信息.本文运用飞秒瞬态吸收光谱和时间相关单光子计数实验系统研究了在水(H₂O)和氘代水(D₂O)溶液中乙酰基取代酪氨酸(AcTyr)对Eosin Y的超快荧光猝灭动力学过程.发现导致AcTyr对Eosin Y荧光猝灭的主要原因是由于它们之间形成了短寿命的基态复合物.我们还发现Eosin Y与AcTyr形成的基态复合物的激发态寿命具有明显的动力学同位素效应,表明AcTyr对Eosin Y的荧光猝灭是通过质子耦合电子转移过程发生的.