Metal nanoparticles on polymer surfaces: 4. Preparation and structure of colloidal gold films

Abstract

The process of the enlargement of gold hydrosol nanoparticles adsorbed on the surfaces of glassy polymers (polystyrene and poly(2-vinylpyridine)) in mixed aqueous solution of chloroauric acid and hydroxy- lamine is studied. It is established that the character of this process depends on the intensity of metal-polymer interaction and the density of nanoparticle packing in an initial monolayer. At a high coverage of a poly(2- vinylpyridine) surface by "seeding" gold particles, their rather uniform growth is observed, whereas, at low cov- erage, the enlargement of adsorbed particles, as well as the nucleation and growth of new particles take place. At the same time, new Au nanoparticles are not formed on the polystyrene surface in the enlargement process, even at low coverages by preliminarily deposited "seeding" hydrosol particles. Adsorbed gold particles can also be enlarged after their preliminary incorporation into the polystyrene surface layer. Such an incorporation (par- tial embedding) is ensured by the annealing of a system at a temperature between "surface" ( ) and "bulk" glass transition temperatures. In this case, the value can be considerably decreased (up to room temperature) by the addition of small amounts of a homologue with a much lower molecular mass in the polystyrene matrix. Lateral conductivity of colloidal Au films formed on a poly(2-vinylpyridine) surface by the enlargement of adsorbed seeding particles is measured. According to these measurements, contacts providing the formation of conductive channels are formed in the process of nanoparticle enlargement. T g T g