The monolayer thickness dependence of quantized double-layer capacitances of monolayer-protected gold clusters

Jocelyn F. Hicks, Allen C. Templeton, Shaowel Chen, Kevin M. Sheran, Ramesh Jasti, Royce W. Murray, Justin Debord, T. Gregory Schaaff, Robert L. Whetten

Research output: Contribution to journalArticlepeer-review

213 Scopus citations

Abstract

This report describes how the electrochemical double-layer capacitances of nanometer-sized alkanethiolate monolayer-protected Au clusters (MPCs) dissolved in electrolyte solution depend on the alkanethiolate chain length (C4 to C16). The double-layer capacitances of individual MPCs (C(CLU)) are sufficiently small (sub-attoFarad, aF) that their metal core potentials change by > 0.1 V increments for single electron transfers at the electrode/solution interface. Thus, the current peaks observed are termed 'quantized double layer charging peaks', and their spacing on the potential axis varies with C(CLU). Differential pulse voltammetric measurements of C(CLU) in solutions of core-size-fractionated (i.e., monodisperse) MPCs are compared to a simple theoretical model, which considers the capacitance as governed by the thickness of a dielectric material (the monolayer, whose chain length is varied) between concentric spheres of conductors (the Au core and the electrolyte solution). The experimental results fit the simple model remarkably well. The prominent differential pulse voltammetric charging peaks additionally establish this method, along with high-resolution transmission electron microscopy and laser ionization-desorption mass spectrometry, as a tool for evaluating the degree of monodispersity of MPC preparations. We additionally report on a new tactic for the preparation of monodisperse MPCs with hexanethiolate monolayers.

Original languageEnglish (US)
Pages (from-to)3703-3711
Number of pages9
JournalAnalytical Chemistry
Volume71
Issue number17
DOIs
StatePublished - Sep 1 1999
Externally publishedYes

ASJC Scopus subject areas

  • Analytical Chemistry

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