Electron-phonon coupling dynamics in very small (between 2 and 8 nm diameter) Au nanoparticles

Ultrafast laser experiments were used to study electron-phonon coupling in Au nanoparticles in the 2.5 to 8 nm size range in aqueous solution. The ele ctron-phonon coupling constants for these samples were found to be independ ent of the particle size. This is attributed to a weak interaction between the electron gas and the surface phonon modes in Au. Calculations were perf ormed which show that the coupling between the hot electrons and the surfac e accounts for less than 10% of the total electron energy losses for these particles. Thus, bulk electron-phonon coupling dominates the relaxation of excited electrons in Au particles, for particles as small as several hundre d atoms. (C) 2000 American Institute of Physics. [S0021-9606(00)70813-0].