First-principles investigation of electrochemical properties of gold nanoparticles

Abstract

A first-principles formalism is employed to investigate the effects of size and structure onthe electronic and electrochemical properties of Au nanoparticles with diameters between0.8 and 2.0 nm. We find that the behavior of the ionization potentials (IPs) and the electronaffinities (EAs) as a function of cluster size can be separated into many-body andsingle-electron contributions. The many-body part is only (and continuously) dependent onparticle size, and can be very well described in terms of the capacitance of classicalspherical conductors for clusters with more the 55 atoms. For smaller clusters,molecule-like features lead the capacitance and fundamental gap to differ systematicallyfrom those of a classical conductor with decreasing size. The single-electron partfluctuates with particle structure. Upon calculating the neutral chemical potentialμ0 = (IP+EA)/2, the many-body contributions cancel out, resulting in fluctuations ofμ0 around the bulk Au work function, consistent with experimental results. The values ofIP and EA changes upon functionalization with thiolated molecules, and themagnitude of the observed changes does not depend on the length of the alkane chain.The functionalization can also lead to a transition from metallic to non-metallicbehavior in small nanoparticles, which is consistent with experimental observations.