Electron self-exchange between [Au140.sup.?0] nanoparticles is faster than that between [Au38.sup.?0] in solid-state, mixed-valent films

The well-defined one-electron steps in the voltammetry of solutions of the nanoparticles Au38(SC2Ph)24 and Au140(SC6)53 enable preparation of solutions containing for example Au38(SC2Ph)24 and Au 38(SC2Ph)24 [[.sup.(CIO4)].sup.-] nanoparticles in known relative proportions. Differences in pre-exponential terms in the activation equations for the two nanoparticles are a smaller contributor to the rate constant difference and could be partly ascribed to differences in tunneling distances.