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.