Department of Chemistry, Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, USA.
ACS Nano. 2013 Jan 22;7(1):108-16. doi: 10.1021/nn303320w. Epub 2012 Dec 11.
We explore the transport of electrons between electrodes that encase a two-dimensional array of metallic quantum dots linked by molecular bridges (such as α,ω alkaline dithiols). Because the molecules can move at finite temperatures, the entire transport structure comprising the quantum dots and the molecules is in dynamical motion while the charge is being transported. There are then several physical processes (physical excursions of molecules and quantum dots, electronic migration, ordinary vibrations), all of which influence electronic transport. Each can occur on a different time scale. It is therefore not appropriate to use standard approaches to this sort of electron transfer problem. Instead, we present a treatment in which three different theoretical approaches-kinetic Monte Carlo, classical molecular dynamics, and quantum transport-are all employed. In certain limits, some of the dynamical effects are unimportant. But in general, the transport seems to follow a sort of dynamic bond percolation picture, an approach originally introduced as formal models and later applied to polymer electrolytes. Different rate-determining steps occur in different limits. This approach offers a powerful scheme for dealing with multiple time scale transport problems, as will exist in many situations with several pathways through molecular arrays or even individual molecules that are dynamically disordered.
我们探索了电子在由分子桥（如α，ω碱性二硫醇）连接的二维金属量子点电极之间的传输。由于分子可以在有限温度下移动，因此在传输电荷的同时，包含量子点和分子的整个传输结构处于动态运动中。然后，有几个物理过程（分子和量子点的物理迁移、电子迁移、普通振动）都会影响电子传输。每个过程都可以在不同的时间尺度上发生。因此，不适合使用标准方法来解决这种电子转移问题。相反，我们提出了一种处理方法，其中使用了三种不同的理论方法——动力学蒙特卡罗、经典分子动力学和量子输运。在某些极限下，一些动态效应并不重要。但总的来说，传输似乎遵循一种动态键渗流图像，该方法最初作为正式模型引入，后来应用于聚合物电解质。在不同的限制下，会出现不同的速率决定步骤。这种方法为处理多个时间尺度的输运问题提供了一种强大的方案，因为在许多情况下，分子阵列或甚至是动态无序的单个分子都会有多个通过的途径。
