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.