Heat dissipation from silica-coated gold nanoparticles in both water and ethanol solutions has been examined by time-resolved spectroscopy.. The results show that the characteristic time constant for heat dissipation depends on the thickness of the silica shell and the solvent, even though the shells are much thicker than the thermal diffusion length corresponding to the time scale for these measurements. This is attributed to differences in the properties of the silica shells, that is, the thermal conductivity of the silica depends on how the shell is processed. (C) 2003 Elsevier Science B.V. All rights reserved.