Quantized double-layer charging of highly monodisperse metal nanoparticles
Quantized double-layer charging of highly monodisperse metal nanoparticles
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DOI：
10.1021/ja027724q
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发表时间：
2002-11-06
影响因子：
15
通讯作者：
Murray, RW
中科院分区：
文献类型：
--
作者：
Hicks, JF;Miles, DT;Murray, RW
我们描述了电化学观察到的量子化双层 (QDL) 充电的前所未有的分辨率，这是通过降低溶液温度和退火程序来实现的，该退火程序产生己硫醇单层保护的金簇 (C6 MPC)，在充电电容 C-CLU 中具有高水平的单分散性。纳米级金属颗粒的电荷变化中的一个电子之间的电化学势轴上的间距DeltaV= e/C-CLU，由它们的有效电容CCLU决定。具有 Au-140 核的 C6 MPC 的高单分散性有助于（a）详细的旋转圆盘和循环伏安测量，（b）基于假设的可逆、多价氧化还原行为的 QDL 波形模拟，（c）纳米颗粒扩散速率的确定，以及（d）观察 MPC 电荷状态中多达 13 个变化， MpC(6-) 至 MpC(7+)。单电子 QDL 充电峰在接近零电荷 MPC 电势的电势处相当均匀地间隔（AV 常数），但在更正和负的电势处则不规则地间隔。不规则的间距很难用经典的双层电容思想来合理化，并且被认为是由纳米粒子核心的电子态的相应结构（例如，不平滑）密度引起的，这是由于其小的HOMO/LUMO间隙和早期的分子状行为造成的。
We describe unprecedented resolution of electrochemically observed quantized double layer (QDL) charging, attained with use of reduced solution temperatures and with an annealing procedure that produces hexanethiolate monolayer protected gold clusters (C6 MPCs) with a high level of monodispersity in charging capacitance, C-CLU. The spacing DeltaV= e/C-CLU on the electrochemical potential axis between one electron changes in the electronic charge of nanoscopic metal particles is determined by their effective capacitance CCLU. The high monodispersity of the C6 MPCs with Au-140 cores facilitates (a) detailed rotated disk and cyclic voltammetric measurements, (b) simulation of QDL waveshapes based on assumed reversible, multivalent redox-like behavior, (c) determination of nanoparticle diffusion rates, and (d) observation of as many as 13 changes in the MPC charge state, from MpC(6-) to MpC(7+). The single electron QDL charging peaks are quite evenly spaced (AV constant) at potentials near the MPC potential of zero charge, but are irregularly spaced at more positive and negative potentials. The irregular spacing is difficult to rationalize with classical double layer capacitance ideas and is proposed to arise from a correspondingly structured (e.g., not smooth) density of electronic states of the nanoparticle core, resulting from its small HOMO/LUMO gap and incipiently molecule-like behavior.