芘四磺酸钠水溶液激光闪光光解机理

采用激光闪光光解-瞬态吸收光谱技术研究了355nm激光作用下芘四磺酸钠(PyTS)水溶液的光化学反应机理及其产生水合电子的动力学行为.研究首次发现PyTS水溶液激发单线态(PyTS1*)在260nm、激发三线态(PyTS3*)在300nm及阴离子自由基(PyTS-?)在330nm处的特征吸收峰;分析了生成的水合电子(e-aq)的主要反应途径包括自猝灭反应及与PyTS的反应,得到水合电子与PyTS反应的准一级速率常数为2.7′105s-1;并计算得到在此实验条件下,PyTS水溶液经双光子吸收产生的水合电子量子产率为3.2′10-2.     

Photophysics of ruthenium(II) complexes with 2-(2′-pyridyl) pyrimidine and 2,2′-bipyridine ligands in fluid solution

The photophysics of three complexes of the form Ru(bpy)₃₋(pypm)²⁺ (where bpy2,2′-bipyridine, pypm 2-(2′-pyridyl)pyrimidine and P=1, 2 or 3) was examined in H₂O, propylene carbonate, CH₃CN and 4:1 (v/v) C₂H₅OH---CH₃OH; comparison was made with the well-known photophysical behavior of Ru(bpy)₃²⁺. The lifetimes of the luminescent metal-to-ligand charge transfer (MLCT) excited states were determined as a function of temperature (between −103 and 90 °C, depending on the solvent), from which were extracted the rate constants for radiative and non-radiative decay and ΔE, the energy gap between the MLCT and metal-centered (MC) excited states. The results indicate that ^*Ru(bpy)₂(pypm)²⁺ decays via a higher lying MLCT state, whereas ^*Ru(pypm)₃²⁺ and ^*Ru(pypm)₂(bpy)²⁺ decay predominantly via the MC state.     

金属离子与卟啉的嵌入反应动力学研究(Ⅳ)──乳酸缓冲体系中四吡啶基卟啉衍生物与铜(Ⅱ)的配位反应

研究了在35±0.1℃、离子强度0.5mol/L(KCI)下,乳酸根催化Cu²⁺离子嵌入溴化间-四(N-乙酸甲酯基-3-吡啶基)卟啉和溴化间-四(N-氰乙基-3-吡啶基)卟啉的反应动力学。根据催化剂浓度、溶液的pH值与反应速率间的关系,得到Cu²⁺离子嵌入该类卟啉的反应动力学方程。实验结果表明,该类反应遵循负离子催化卟啉变形机理,变形的卟啉及其与乳酸根离子的缔合物为可能的活性中间体。     

微量热法研究过氧化氢酶反应

利用微量热法和热动力学方程研究了过氢化氢酶反应.该反应遵循Michaelis-Menten动力学,298.15K和pH7.0时,其米氏常数、酶转换数以及摩尔反应焓分别为2.36×10^-2mol/L、1.20×10⁴s^-1和-83.67kJ·mol^-1.过氧化氢酶反应后期对底物是一级反应,其总反应速度常数和一级速度常数分别为k_o=6.31×10⁵L·mol^-1·s^-1和k₁=6.31×10⁵/[E_o]s^-1.该反应服从Ogura机理,其酶-底物三元复合物的分解速度常数为6.00×10³s^-1.     

脉冲辐解研究喹啉和异喹啉与瞬态粒子的反应

通过合理控制反应条件, 使体系在电子束脉冲作用后只剩下所需要的一种瞬态粒子, 用脉冲辐解研究了喹啉、异喹啉分别与水合电子、羟基自由基、氢自由基等几种典型的氧化还原瞬态粒子的反应过程, 研究了各种瞬态产物的吸收光谱及其变化规律, 测定了相关反应的速率常数. 喹啉、异喹啉与水合电子的反应速率常数分别为7.1×10⁹和3.4×10⁹ mol^-1·L·s^-1, 与羟基自由基的反应速率常数分别为7.2×10⁹和3.4×10⁹ mol^-1·L·s^-1, 与氢自由基的反应速率常数分别为5.7×10⁹和3.6×10⁹ mol^-1·L·s^-1. 这一结果表明, 喹啉、异喹啉均能够非常迅速地与水合电子、羟基自由基、氢自由基发生反应, 喹啉比异喹啉的反应速率更快. 运用电子理论分析了瞬态反应产物结构的稳定性差异, 结果表明, 喹啉的反应产物比异喹啉的稳定, 从而揭示了喹啉比异喹啉反应速率快的原因.     

利用表面等离子体共振技术进行TNF免疫复合物的动力学分析

表面等离子体共振 ( Surface plasmon resonance,SPR)技术是近年来发展起来的测定分子间相互作用的技术 ,应用最广泛的是 Pharmacia公司发展的生物分子相互作用实时分析 ( Biomolecular interactionanalysis,BIA)技术 [1～ 3] .它可以实时、原位地测定生物大分子间的相互作用 ,而反应物无需标记 ,可以测定反应的动力学常数 ,这对于进行反应的动力学分析和机理研究 ,以及进行性质鉴定和筛选应用具有非常重要的意义 [4～ 8] .肿瘤坏死因子 ( Tumor necrosis factor,TNF)是临床上用于肿瘤治疗的非常有效的细胞因子类药物 [9] .本文报道了…     

玻碳电极表面因瓦合金的电化学成核机理

在弱酸性因瓦合金(含镍质量分数为32~36 % 的镍铁合金)镀液中, 以线性扫描伏安法、循环伏安法和恒电位阶跃法对因瓦合金在玻碳电极表面的电沉积过程及其成核机理进行研究. 结果表明, 在该体系下, 因瓦合金在玻碳电极表面的电结晶属于扩散控制下的不可逆电极过程. 运用Scharifker-Hills理论模型(SH)拟合实验数据表明, 因瓦合金在玻碳电极表面的共沉积更加符合三维瞬时成核的成核规律. 运用Heerman-Tarallo理论模型(HT)分析得到因瓦合金在玻碳电极表面的成核生长的动力学参数, 当阶跃电位从-1.11 V变化至-1.17 V (vs SCE), 成核密度数(N₀)由0.72×10⁵ cm^-2提高至1.91×10⁵ cm^-2, 成核速率常数(A)从 40.35 s^-1增至 194.38 s^-1, 扩散系数(D)为(7.67±0.15)×10^-5 cm²•s^-1, 变化不大.     

薄层光谱电化学法测定辅酶B12模型化合物的生成速率常数

用薄层光谱电化学方法和单电位-计时吸收光谱法(SPS-CA),测得钴四苯基卟啉(CoTPP)分别与碘甲烷、苄基氯和氯丁烷形成含σ钴-碳键辅酶B₁₂模型化合物的速率常数为11.09、1.62×10²和6.93×10^-2mol^-1·L·s^-1。钴卟啉与这3种卤代烷的反应是二级反应,对各自的反应物Co(Ⅰ)TPP和卤代烷都是一级反应。     

抗癌光敏剂ZnPcSP在溶液中的存在状态及其对活性的影响

研究了两亲性抗癌光敏剂磺基邻苯二甲酰亚胺甲基酞菁锌(ZnPcSP)单体与聚集体的可见吸收光谱特征以及溶剂组成对其聚集平衡的影响,得到了ZnPcSP在一系列溶剂中的聚集平衡常数.进而研究了存在状态对ZnPcSP的S₁₈₀肿瘤抑瘤率的影响.ZnPcSP在生理盐水中主要以三聚体形式存在,而在CEL溶液中,则主要以单体形式存在,后者对S180的抑瘤率是前者的8倍     

溶液中钪与草酸离子的配位作用

提钪工艺中常使草酸钪溶于过量草酸铵溶液中。但文献中有关钪与草酸离子配位作用的报导甚少。等用分光光度法测定了ScC₂O₄⁺配离子的稳定常数,而J·Stary则用分配法测定了SC(C₂O₄)₃^3-配离子的稳定常数,这些工作都没有对溶液中可能生成各级配离子进行研究。     

QUENCHING OF THE FLUORESCENCE OF 8-METHOXYPSORALEN BY PROTONS

Abstract— The quenching of 8-methoxypsoralen (8-MOP) fluorescence by protons was observed to occur at the diffusion controlled rates in aqueous solutions at room temperature. Enhanced basicity of 8-MOP in the excited state compared to the ground state is expected on theoretical grounds. The fluorescence yield. which we determined as 6.3 × 10^--⁴ at pH 1 is surprisingly low and indicative of extremely fast radiationless decay pathways. The fluorescence lifetime of 8-MOP in neutral aqueous solution is on the order of 1–2 ns.     

锗－芦丁极谱络合吸附波的研究

在醋酸盐缓冲底液中,可获得Ge-芦丁的2个灵敏的络合吸附波P₁和P₂,分别对应于络合物中Ge(Ⅳ)还原至Ge(Ⅱ)再还原至Ge(0).两波的检出限分别为8.0×10^-8和4.0×10^-8mol/L.测得电活性络合物的组成为Ge:Rt=1:3,表面电极反应的速率常数(k_s)₁=10.5s^-1,(k_s)₂=1.9s^-1.还测定了有机锗口服液中锗的含量。     

The discrimination between triplet state and radical cation in the pulse radiolysis of bithiophene in CCl4

The triplet state (³2T) and the radical cation (2T⁺√) of 2,2′-bithiophene (2T) are characterized by pulse radiolysis in CCl₄. Two main absorption bands at 360 and 420 nm are respectively attributed to ³2T* and to 2T⁺√. The triplet, induced in an excited state through a Förster mechanism, undergoes a conformational rearrangement (k₆=(6.8±0.9)×10⁶ s⁻¹). The radical cation is produced both through a resonance charge transfer and a second diffusional process; the two oxidizing species are respectively CCl₄⁺√ and (CCl⁺₃Cl⁻)_solv through the mediation of a singlet excited state, ¹2T*.     

[Co(tp)2(Me3en)]ClO4配合物不对称配位氮原子的重氢化研究

合成了[Co(tp)₂(Me₃en)]ClO₄配合物,用离子交换法提纯和分离了该配合物的2对对映体:Δ(R)∧(S)、Δ(S)∧(R)异构体,用高分辨NMR法分别测定了这2对对映体的不对称配位氮原子的重氢化速率常数k_D值分别为:1.0×10⁵和1.8×10⁴L·mol^-1·s^-1(34.0℃),讨论了影响重氢化作用的因素。     

ANALYSIS OF FLUORESCENCE KINETICS AND ENERGY TRANSFER IN ISOLATED α SUBUNITS OF PHYCOERYTHRIN FROM Nostoc sp.

Abstract— The fluorescence decay profiles, relative quantum yield, and transmission of the phycoerythrin a subunit, isolated from the photosynthetic antenna system of Nostoc sp., were measured using single picosecond laser excitation. The fluorescence decay profiles were found to be intensity independent for the intensity range investigated (4 × 10¹³ and 4 × 10¹⁵ photons-cm-² per pulse). The decay profiles were fitted to a model assuming both chromophores absorb and fluoresce. The inferred total deactivation rates for the two chromophores, in the absence of energy transfer and when the effects of the response time of the streak camera and the finite pulse width are properly included, are 1.0 × 10¹⁰s' and 1.0 × 10⁹ s ¹ for the s and f chromophores. respectively, whereas the transfer rate between the two fluorophorcs is estimated to be 1.0 × 10¹⁰ s⁻¹ giving a s→ f transfer rate on the order of (100 ps)⁻¹. Steady-atate polarization measurements were found to be equal to those calculated using the rate parameters inferred from the kinetic model fit to the fluorescence decays. The apparent decrease in the relative fluorescence quantum yield and increase of the relative transmission with increasing excitation intensity is suggestive of ground state depletion and upper excited state absorption. Evidence suggests that exciton annihilation is absent within isolated α subunits for the intensity range investigated (4 × 10¹³ to 4 × 10¹⁵ photons-cm ² per pulse).     

PHOTOCHEMISTRY OF URACIL. INTERSYSTEM CROSSING AND DIMERIZATION IN AQUEOUS SOLUTION

Abstract— Ultraviolet irradiation of ¹⁴C-uracil in aqueous solution results in the formation of hydrate and dimer photoproducts. The rate of dimerization increases with increasing uracil concentration, and decreases with increasing concentration of oxygen in solution. The kinetics are in agreement with a model previously proposed to account for the reactions, in which dimerization occurs by a reaction involving the triplet state of uracil, but hydration occurs from an excited singlet state. Oxygen reduces dimer formation by quenching the triplet. The quantum yield for intersystem crossing (ISC) to the triplet depends on the irradiation wavelength, increasing from 0.0014 at 280 nm to 0.016 at 230 nm. The ratio of rate constants for reaction of the triplet with oxygen and for dimerization is 1.1; the ratio of rate constants for triplet decay and for dimerization is 5.9 × 10^-5 M. The increase in ISC with photon energy suggests that ISC is favoured from excited vibrational levels. The quantum yield for hydration is about 0.002 at pH 4.5 for all wavelengths, but increases as the pH is decreased.     

二氟沙星在中性水溶液中的光化学性质(英文)

对二氟沙星在中性水溶液中的光化学性质进行了研究.在pH值为7.17的水溶液中二氟沙星的紫外吸收峰位于273 nm(摩尔消光系数ε=33000 dm3·mol-1·cm-1),323 nm(ε=15500 dm3·mol-1·cm-1),335 nm(ε=15500 dm3·mol-1·cm-1)处.荧光吸收和发射光谱均显示二氟沙星具有pH效应,其pKa(电离平衡常数)测定分别为5.9和9.8.二氟沙星的荧光量子产额较低,在pH=3.00时达到最大值,为0.06.同时对二氟沙星在中性水溶液中的激光光解和脉冲辐解进行详细研究.激光光解研究发现在水溶液中二氟沙星的三重激发态位于620nm,其摩尔消光系数为7900 dm3·mol-1·cm-1.通过能量转移的方法得到其三重激发态的能量为263.5 kJ·mol-1,三重激发态的量子产额为0.21.在激光激发下,二氟沙星进行单光子电离其量子产额为0.02.脉冲辐解研究表明二氟沙星可以与水合电子(e-aq)及羟基自由基(·OH)快速反应,其二级反应动力学常数分别为1.72×1010和1.0×1010dm3·mol-1·s-1.本文对二氟沙星光化学性质的研究有助于确定其光敏毒性的产生机理.     

A homopolymer based on double B←N bridged bipyridine as electron acceptor for all-polymer solar cells

A homopolymer based on double B ← N bridged bipyridine was reported as a novel polymer electron acceptor. The resulting all-polymer solar cells show power conversion efficiencies of 2.44%–3.04%.     

The Ericksen number and Deborah number cascades in sheared polymeric nematics

Samples of liquid crystalline poly(γ-benzyl-glutamate) solutions are sheared between glass surfaces with gaps, d = 10-500 μ, and shearing velocities, V = 0·05-10 000 μs^-1 so that the Ericksen number E ≡ Vdγ₁/K is varied over a large range, E ≈ 1-10⁷. Here γ₁ is the rotational viscosity and K₁ is the Frank splay constant, with γ₁/K₁ estimated to be approximately 1 s μ^-2 for our samples. We observe by polarizing microscopy a sequence of transitions with increasing Ericksen number analogous to that observed in small molecule tumbling nematics: namely rotation of the director out of the shearing plane and into the vorticity direction at Vd ≈ 25 μ² s^-1, and formation of roll cells at Vd ≈ 50 μ² s^-1. The roll cells become finer with increased Vd in accord with predictions of linear stability theory using the Leslie-Ericksen equations, and at Vd ≳ 500 μ² s^-1, the cells become very irregular, producing director turbulence. The turbulence becomes finer in scale as Vd increases, reaching sub-micron, and possibly molecular scales when Vd ≧ 10⁵ μ² s^-1. At the highest velocities, transitions in orientation and texture are controlled by the Deborah number De≡λV/d, where λ is the molecular relaxation time, and uniform texture-free samples are obtained when De ≳ 5.     

355 nm光照下大气液相中HNO2与C6H5Cl的反应机理

利用瞬态吸收光谱技术进行了有氧、无氧条件下氯苯与亚硝酸水溶液的交叉反应机理研究，初步考察了这些瞬态物种的生长与衰减等行为, 并对其光解产物进行了GC/MS分析.研究表明，HNO₂在355 nm紫外光的照射下可产生•OH自由基, •OH和氯苯反应生成C₆H₅Cl•••OH，反应速率常数为（6.6～7.0）×10⁹ L•mol^-1•s^-1; 在有氧条件下C₆H₅Cl•••OH可氧化为C₆H₅Cl•••OHO2, 反应速率常数为(1.6 ± 0.2)×109 L•mol^-1•s^-1,然后进一步分解; C₆H₅Cl•••OH衰减或与亚硝酸等作用可形成多种含硝基的化合物或醌类物质.