Optical modeling of the plasmon band of monolayer-protected nanometal clusters in pure and in polymer matrix thin films as a function of heat treatment

Abstract

The plasmon band shape of thin films of gold nanoparticles and their composites can be quantitatively modeled in a surprisingly simple way by taking into account (i) quantum-size effect of the Au core on its permittivity, (ii) nanostructure effect of the core shell and matrix on the effective medium, and (iii) optical properties of thin films in a transfer-matrix formalism. From the excellent agreement achieved with the optical spectra of these films, neat and when dispersed in poly(3,4-ethylenedioxythiophene) matrices, details of the nanocrystal relaxation, desorption of the ligand shell, and ultimate surface melting and core-core coalescence to give percolating conductive paths during heat treatment were extracted.