光敏性BZ反应的时空动力学

作为研究非线性时空动力学最理想的化学反应体系之一,三联(2,2'-联吡啶)钌(Ⅱ)(Ru(bpy)₃²⁺)为催化剂的Belousov-Zhabotinsky (BZ)振荡反应具有独特的光敏特性并能呈现丰富的时空动力学行为。研究光控BZ反应有助于我们对一系列物理、化学和生命体系中复杂动力学现象的理解。本文综述了不同实验条件下光效应对钌催化BZ反应均相复杂振荡和空间反应扩散化学波的影响, 以及光响应BZ反应与软物质耦合体系的复杂动力学行为,在此基础上介绍光抑制和光诱导反应机理和模型。对光控BZ反应体系存在的问题和发展方向进行了探讨。     

光敏BZ振荡封闭体系振荡频率关系的研究

溴离子是振荡反应的抑制剂，其浓度减小的速率决定了振荡周期中自催化诱导期持续的时间，而振荡周期的总时长则取决于自催化诱导期，因此，溴离子能够影响体系振荡周期。而体系初始存在溴离子时，体系振荡频率与光强的动力学关系尚未研究。因此，在这项工作中，建立了Ru(bpy)₃²⁺催化Belousov-Zhabotinsky(BZ)均相封闭体系，研究溴离子存在时，体系振荡频率与光强的动力学关系，探究BZ反应物浓度对体系振荡频率曲线的影响。研究发现，初始存在溴离子时，体系振荡频率与光强之间仍然存在非单调关系。反应溶液中初始溴化钠浓度对于各反应物调制“振荡频率-光强”的效应起到不同作用：随着NaBrO₃浓度和MA浓度增高，体系振荡频率整体上向高频区域移动；随着HNO₃浓度的增加，体系振荡频率先向低频区域移动再向高频区域移动；随着NaBr浓度的增加，体系振荡频率向低频区域移动。这一研究为非线性系统的基础研究提供理论参考。     

外控恒电流对BZ电化学反应体系动力学行为的影响

在使用探头对BZ反应体系进行观测时,原来纯粹的BZ反应系变成了由两个子系通过扩散过程耦合成的一类特殊电化学体系,所用的探头能否如实反映该体系的真实振荡行为值得探讨。本文基于FKN机理及Oregonator模型,分别对Pt电极BZ反应体系建立了动力学模型,讨论了两子系出现极限环振荡的动力学行为不一致性及外控电极电流的影响。     

铂电极BZ反应体系的系统动力学分析

在一定的条件下,将铂电极BZ化学反应的六变量高维动力学系约化为三变量体系,同时对该体系进行了全面的系统动力学分析.研究结果表明,通过改变耦合体系的外控参数条件,在将体相保持在均一稳定定态的参数范围内,电极反应相可能进入振荡区,而呈现出电极反应相与体相的动力学行为不一致性.进一步计算出体相处于非振荡状态时,电极反应相产生电化学振荡的外控参数区域.     

溴离子对BZ非催化振荡反应的影响

Br~-对Belousov-Zhabotinsky(BZ)振荡反应起着控制作用。近来发现,一些有机物在被BrO_3~-氧化时,即使没有金属离子Ce~(3+),Mn~(2+),Fe(phen)_3~(2+),也可产生振荡反应,称为非催化BZ振荡反应。本文选择酪氨酸(Tyr)-BrO_3~--H_2SO_4 BZ振荡体系,对Br~-的影响作了系统的研究,对机理作了初步探索。     

CSTR中Ferroin催化BZ反应中的倍周期振荡和混沌

Ferroin催化的BZ反应是化学时空斑图研究中最常用的反应体系, 研究该体系时发现了简单倍周期、混合模式倍周期振荡、混沌以及低流速下溴离子选择电极的混合模式振荡, 并用Györgyi和Field两环偶合的BZ反应模型进行数值模拟解释. 该研究为用于光学测定的时空斑图研究提供了从简单振荡到各种复杂振荡的反应介质, 也表明BZ反应复杂振荡与混沌研究可扩展到不同催化剂催化的溴酸盐驱动的非线性反应体系.     

非线性化学反应与质量作用定律: BZ-CSTR反应体系的 周期调制

以流速为扰动参数,对连续搅拌釜式反应器(CSTR)中的Belousov-Zhabotinsky(BZ)反应体系进行周期扰动,改变扰动周期或扰动强度,在某些条件下,本征振荡可以扰动控制为另一类周期振荡形式,以BZ反应的四变量Montanator模型为基础,对相应流速区域的分叉图进行了周期扰动,计算结果与实验基本定性一致,表明对本体系而言,在分叉点附近质量作用定律依然具有一定的适用性。     

间歇釜中BZ类均相无机振荡反应的研究

在间歇釜中, 以BrO3^--H2PO2^--Mn^2^+-Fe(phen)3^2^+-H2SO4为体系, 本文首次设计了一个纯无机均相BZ类化学振荡体系, 采用溴离子选择性电极和紫外可见分光光度计可分别观察到[Br^-],[Mn^3^+]和[Fe(phen)3^3^+]的振荡现象。对振荡反应产物及总反应计量关系进行了分析, 考察了反应物浓度和反应温度对体系振荡反应的影响, 并由此计算得到振荡反应的表观活化能, 研究了Cl^-,Br^-, Br2, 丙烯腈等因素对振荡反应的影响, 并由此对振荡反应的控制机理作了探索。对体系中两种金属离子的作用进行了分析。在此基础上提出了一种在间歇釜中设计均相BZ类振荡反应的新方法。利用这一方法, 不仅可以设计无机振荡反应, 而且还可以设计一系列由氨基酸、多肽、糖类等具有生物功能的物质参与的化学振荡, 有助于理解生物体内普遍存在的周期性现象。     

氨基酸对Belousov-Zhabotinskii反应的影响

作者研究了18种氨基酸及一种氨基酸酯的盐酸盐对 BZ 反应的影响。反应体系中以邻-菲罗啉亚铁离子为催化剂,其结果见英文表格。这19种氨基酸按其反应特点可以分为四类:(1)甘氨酸和其它烷基取代的天然氨基酸对 BZ 反应没有什么影响。(2)含硫元素的α-氨基酸使 BZ 反应的振荡周期加长,振幅加大,寿命变短。(3)具有吸电子基团取代的α-氨基酸使 BZ 反应的振荡周期缩短,振幅减少,寿命较短。(4)酪氨酸可加强 BZ 反应的振荡。甚至丙二酸不存在时也可进行化学振荡。作者还用不同的氨基酸代替丙二酸在 Mn~(++)和邻-菲罗啉亚铁离子的作用下研究 BZ 反应的化学振荡。上述(1)中的氨基酸、谷氨酸和赖氨酸均可发生5～6次的化学振荡。天冬氨酸和酪氨酸可以发生较长时间的振荡。其它氨基酸则不易发生振荡。     

NiL(ClO4)2催化NaBrO3-MA-H3PO4体系振荡反应的研究

报道了一种反式Curtis环的镍(Ⅱ) 的配合物NiL(ClO4)2(L为2,4,4,9,11,11-六甲基-1,5,8,12-四氮杂环十四-1,5,8,12-四烯)催化NaBrO3-CH2（COOH）2（MA）-H3PO4体系的化学振荡反应。测得该体系的振荡范围,研究、分析了各物种浓度、自由基抑制剂和还原剂、Ag+、Hg2+以及温度对振荡反应的影响。结果表明Br-起重要动力学控制作用,在反应过程中有自由基、Br2产生并参与了反应。同时发现搅拌速度对反应有很大影响。该反应的振荡轨迹与经典BZ反应及其它四氮杂大环配合物催化的体系有所不同。     

甲酸Pt电极电化学氧化体系中时间自组织导致的可利用功耗失

在电极化学反应步骤为控制步骤的条件下,对甲酸阳极氧化体系中出现的电化学振荡的阈值及跨越阈值后状态演化的极限环路径进行了系统动力学计算.同时,根据非平衡电极过程的耗散-涨落理论,进一步对跨越振荡阈值前后的临界区与电化学震荡区的极化曲线及功耗谱进行了随机热力学分析计算.研究结果表明,跨越临界区后单位电化学反应功耗谱出现突降...     

一种新的振荡体系的研究 Ⅰ. 在铑膦催化剂存在条件下的丙烯氢甲酰化振荡现象

丙烯氢甲酰化过程(以下简称氢甲酰化过程),可以用如下反应式表示: 作者在进行氢甲酰化动力学研究中发现,在接近工业生产条件,特别是使用了适当聚合度的正丁醛做溶剂时,只要控制一定的操作条件,即可在反应的母体转化期和诱导期内检测出反应体系的气相中各组分浓度的振荡变化。据作者了解,目前尚未有关于该体系气相组分中浓度振荡的报道。     

Degeneration of Limit Cycle Oscillation in BZ Electrode Reaction System Controlled Externally

A dynamical model of electrode BZ reaction system was establisheed on the basis of three variables Oregonator model and kinetics of electrode process. Under weak periodical constraint approximation, dynamical stability of quasi steady state on the slow manifold of the system is analyzed by means of linearized stability analysis of three variable system. Meanwhile, the corresponding regime favorable for the appearance of limit cycle oscillation is calculated. Computer simulation shows that limit cycle oscillatory regime has degenerated because of the external periodical potential constraint in the electrode phase. In this regime the system behaves as a temporary self-organization. Whereas, outside this regime a kind of response oscillation appear, with same period as the constraint.     

Internal noise coherent resonance for mesoscopic chemical oscillations: a fundamental study.

The effect of internal noise for a mesoscopic chemical oscillator is studied analytically in a parameter region outside, but close to, the supercritical Hopf bifurcation. By normal form calculation and a stochastic averaging procedure, we obtain stochastic differential equations for the oscillation amplitude r and phase theta that is solvable. Noise-induced oscillation and internal noise coherent resonance, which has been observed in many numerical experiments, are reproduced well by the theory.     

Chemical oscillation in electrochemical oxidation of methanol on Pt surface

Based on dual path reaction mechanism, a nonlinear dynamics model reflecting the potential oscilla- tion in electrooxidation of methanol on Pt surface was established. The model involves three variables, the electrode potential (e), the surface coverage of carbon monoxide (x), and adsorbed water (y). The chemical reactions and electrode potential were coupled together through the rate constant ki = exp(ai(e ? ei)). The analysis to the established model discloses the following: there are different kinetics be- haviors in different ranges of current densities. The chemical oscillation in methanol electrooxidation is assigned to two aspects, one from poison mediate CO of methanol electrooxidation, which is the in- duced factor of the chemical oscillation, and the other from the oxygen-containing species, such as H2Oa. The formation and disappearance of H2Oa deeply depend on the electrode potential, and directly cause the chemical oscillation. The established model makes clear that the potential oscillation in methanol electrooxidation is the result of the feedback of electrode potential e on the reactions in- volving poison mediates CO and oxygen-containing species H2Oa. The numerical analysis of the estab- lished model successfully explains why the potential oscillation in methanol galvanostatic oxidation on a Pt electrode only happens in a certain range of current densities but not at any current density.     

Theoretical study on the effects of internal noise for rate oscillations during CO oxidation on platinum(110) surfaces

Very recently, the effects of internal molecular noise in mesoscopic chemical reaction systems have gained growing attention. Using a mesoscopic stochastic model, the effect of internal noise for rate oscillation during CO oxidation on Pt(110) surface is studied analytically. In a parameter region outside but close to the supercritical Hopf bifurcation, a stochastic normal form is obtained from the chemical Langevin equation. By stochastic averaging procedure, the system is simplified and solvable. Noise-induced oscillation and internal noise coherent resonance (which is related to an optimal system size), observed from simulations, are well reproduced by the theory. The theoretical analysis helps to clearly figure out when and how the internal noise affects the system's oscillating dynamics.     

热补偿恒温控制条件下铂电极BZ反应体系中的电化学时间自组织——从极限环型电化学振荡到环面跳跃型非连续电化学振荡

在实验室的热补偿恒温控制条件下, 理论预测的等温恒电流(电压)电化学振荡实际上将发生变异. 用慢流型上准定态的线性化稳定性分析法全面分析了此类恒温控制条件下铂电极BZ反应系在以温度为慢变参数的慢流型上的准稳定性及绕温度轴慢变轨迹的动力学行为. 发现在温度围绕控制值上下往复波动的每一个周期内, 准定态点将穿梭跨越于振荡区与非振荡区之间, 表现为间隙性的沿温度轴的环面型电化学振荡. 计算机模拟结果证实了上述理论分析.     

Open-system nonequilibrium steady state: statistical thermodynamics, fluctuations, and chemical oscillations

Gibbsian equilibrium statistical thermodynamics is the theoretical foundation for isothermal, closed chemical, and biochemical reaction systems. This theory, however, is not applicable to most biochemical reactions in living cells, which exhibit a range of interesting phenomena such as free energy transduction, temporal and spatial complexity, and kinetic proofreading. In this article, a nonequilibrium statistical thermodynamic theory based on stochastic kinetics is introduced, mainly through a series of examples: single-molecule enzyme kinetics, nonlinear chemical oscillation, molecular motor, biochemical switch, and specificity amplification. The case studies illustrate an emerging theory for the isothermal nonequilibrium steady state of open systems.     

Pattern Evolution Induced by Periodic Temperature Modulation in a Binary Polymeric Mixture

Summary: The process of periodic phase separation is numerically studied based on Cahn‐Hilliard‐Cook theory for a binary polymer blend. The model system is quenched blow and above the critical point alternatively. And hierarchic morphologies consisting of large and small domains are observed. As the periodic phase separation proceeds, small domains are created and destroyed periodically, whereas large domains keep growing. Within the first half of each period, the behavior of small domains is similar to the two‐step phase separation. And the quench to one‐phase region during the second half period not only decreases the peak intensity of structure function for large domains, but also eliminates the high‐wave number peak corresponding to small domains. The average order parameter under oscillatory quenches exhibits a periodic behavior. The minimum of average order parameter in each period approaches to its equilibrium value monotonously and the maximum value increase in the early time regime and decrease in the late time regime. The magnitude of oscillation has considerable effects on the evolution of hierarchic structures. Small magnitude of oscillation hinders the formation of hierarchic morphologies. Moreover, large magnitude of oscillation slows down the coarsening of large domains in the early stage of periodic phase separation and accelerates the growth of large domains in the late time regime. In addition, no scaling invariance could be observed for the net growth of large domains.

Snapshot picture of periodic phase separation with \bar \chi , Δχ, and τ_p.     

Interaction of some antioxidants with Belousov-Zhabotinsky reaction based on catechol-BrO 3 − -Mn2+-H2SO4 system

Temporal evolution of a new Mn(II) catalyzed Belousov-Zhabotinsky (BZ) chemical oscillator with catechol (1.2-dihydroxybenzene) as organic substrate is reported within narrow range of concentrations of initial reagents at 30°C. After optimizing the oscillation parameters the system was perturbed with the antioxidants like ascorbic acid and inosine. It is found that ascorbic acid acts as co-substrate within certain concentration limit, whereas inosine acts as a quencher of oscillations. Addition of ascorbic acid to the BZ system decreases induction time thus acting synergistically to help the reaction to enter quickly into the oscillatory regime. A good linear dependence of induction time on the concentration of ascorbic acid (R ² = 0.9948) and inosine (R ² = 0.955) is reported. Inosine has been found to increase the induction time and quench the oscillations. It is mentioned that the magnitude of induction time decreases to a greater extent with ascorbic acid as compared to the magnitude of its increase with the same concentration of inosine. This is pointing to the fact that ascorbic acid is stronger antioxidant than inosine as depicted by their interaction with catechol-based BZ chemical oscillator. Temporal evolution of the BZ reaction with the injection of antioxidants at different stages of reaction is also reported.