Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
Anal Chem. 2010 Jan 1;82(1):84-90. doi: 10.1021/ac9022428.
Finite element simulations of ion transfer (IT) reactions at the nanopipet-supported interface between two immiscible electrolyte solutions (ITIES) were carried out, and the numerical results were generalized in the form of an analytical approximation. The developed theory is the basis of a new approach to kinetic analysis of steady-state voltammograms of rapid IT reactions. Unlike the conventional voltammetric protocol, our approach requires the initial addition of a transferable ion to both liquid phases, i.e., to the filling solution inside a nanopipet and the external solution. The resulting steady-state IT voltammogram comprises two waves corresponding to the ingress of the common ion into the pipet and its egress into the external solution. We demonstrate that both ingress and egress waves are required for characterization of pipet geometry and precise determination of thermodynamic and kinetic parameters for rapid IT reactions. In this way, one can eliminate large uncertainties in kinetic parameters, which are inherent in the previously reported approaches to analysis of nearly reversible steady-state voltammograms of either IT at pipet-supported ITIES or electron transfer at solid electrodes. Numerical simulations also suggest that higher current density at the edge of the nanoscale ITIES increases the significance of electrostatic effects exerted by the charged inner surface of a pipet on IT processes.
采用有限元方法对两种不混溶电解质溶液（ITIES）之间纳米管支撑界面处离子转移（IT）反应进行了模拟，并以解析近似的形式对数值结果进行了概括。所开发的理论是一种新的快速 IT 反应稳态伏安法动力学分析方法的基础。与传统的伏安法协议不同，我们的方法要求将可迁移离子初始添加到两相中，即添加到纳米管内的填充溶液和外部溶液中。所得稳态 IT 伏安图由两个波组成，对应于共同离子进入管和其进入外部溶液的出。我们证明，对于描述管几何形状和精确确定快速 IT 反应的热力学和动力学参数，入口波和出口波都是必需的。通过这种方式，可以消除以前报道的在纳米管支撑 ITIES 处的 IT 或在固体电极处的电子转移的近可逆稳态伏安法分析中，固有存在的动力学参数中的大不确定性。数值模拟还表明，纳米尺度 ITIES 边缘的更高电流密度会增加管内表面带电对 IT 过程施加的静电效应的重要性。
