Long-Range Electronic Communication between Metal Nanoparticles and Electrode Surfaces Separated by Polyelectrolyte Multilayer Films
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- 作者：Jianjun Zhao ; Christopher R. Bradbury ; David J. Fermí ; n
- 刊名：Journal of Physical Chemistry C
- 出版年：2008
- 出版时间：May 1, 2008
- 年：2008
- 卷：112
- 期：17
- 页码：6832 - 6841
- 全文大小：476K
- 年卷期：v.112,no.17(May 1, 2008)
- ISSN：1932-7455
文摘
The dynamics of electron transfer across Au electrodes modified by ultrathin polyelectrolyte multilayers (PEM)and a diluted monolayer of Au nanoparticle was investigated as a function of the film thickness. Au electrodeswere sequentially modified by a self-assembled monolayer of 11-mercaptoundecanoic acid (MUA), followedby alternate adsorption of poly-L-lysine (PLL) and poly-L-glutamic acid (PGA) layers. Submonolayer coverageof citrate stabilized 19.2 ± 2.1 nm Au nanoparticles was achieved by electrostatic adsorption on PLL terminatedsurfaces. In the absence of nanoparticles, cyclic voltammetry and electrochemical impedance spectroscopyof the hexacyanoferrate redox probe showed that the charge-transfer resistance is independent of the numberof adsorbed polyelectrolyte layers. These results revealed that the redox species can penetrate the PEM filmand the electrochemical responses are controlled by the electron tunneling across the initial monolayer ofMUA. The phenomenological charge-transfer resistance decreased by more than 2 orders of magnitude uponadsorption of the Au nanoparticles. Normalization of the electrochemical responses with the number densityof particles revealed that the PEM thickness introduces insignificant effects on the charge-transfer resistance.The effective distance independent electron-transfer kinetic was observed for film thickness up to 6.5 nm.Furthermore, in situ atomic force microscopy studies show that the Au nanoparticles do not introducemeasurable local deformation (compression) of the PEM films. The unique long-range electronic communicationin this system is interpreted in terms of a resonant transport process involving the density of states of trappedredox species at the redox Fermi energy.