Electron hopping dynamics in Au38 nanoparticle Langmuir monolayers at the air/water interface

The electron-transfer dynamics between nanoparticles has been studied as a function of interparticle distance by in situ voltammetry of well-defined monolayers of a metal quantum dot nanoparticle Au38(hexanethiolate)24. The interparticle distance is precisely controlled by the Langmuir technique and addition of various lengths of dithiol linkers (HS(CH2)nSH; n = 5, 6, 8, and 9). Voltammograms of Au38 monolayers display a well-defined single-electron charging peak that increases remarkably with decreasing the interparticle distance. The diffusion coefficient and rate constant calculated from the peak current for core-core electron hopping reaction both exponentially increase respectively, from 3.3 × 10-10 to 5.2 × 10-9 cm2/s and 2.2 × 104 to 5.0 × 105 s-1 as the distance decreases from 13.3 to 9.5 Å and then levels off at 8.0 Å. These rate constants are in good agreement with the literature values, demonstrating that the present experimental approach provides a powerful way to investigate the correlation between the electron-transfer dynamics and nanoparticle assembly structure. Copyright © 2006 American Chemical Society.