Hot electron and phonon dynamics of gold nanoparticles embedded in a gel matrix

Using pump-probe technique, the dynamics of the hot carriers in metallic na nodots induced by femtosecond laser pulses are investigated in gold nanopar ticles embedded in hydrogel and in organic gel and compared to that in aque ous solution. We found that changing the surrounding matrix from aqueous so lution to hydrogel and then to organic gel leads to a large increase in the relaxation time of both the electron-phonon (e-ph) and the phonon-phonon ( ph-ph) coupling. Furthermore, the ph-ph relaxation time becomes sensitive t o the type of the organic solvent trapped in the gel network. This indicate s that the relaxation dynamics depend on the thermal conductivity, chemical structure and the molecular dynamics of the surrounding medium. (C) 2001 E lsevier Science BN. All rights reserved.