Size dependence of the energy relaxation in silver nanoparticles embedded in dielectric matrices

The electron dynamics is studied in silver nanoparticles of different sizes embedded either in a silicate glass or in a porous alumina matrix, using t ime-resolved optical spectroscopy. The femtosecond pump-probe measurements, made under various conditions of excitation, reveal that the energy relaxa tion is faster as the particle size decreases. For particles with identical size and excitation conditions, the relaxation time is found to be faster for clusters in the alumina matrix. The influence of the surface acoustic m odes and of the heat conductivity of the matrix on the energy relaxation is discussed. (C) 1999 American Institute of Physics. [S0003-6951(99)04150-9] .