Effect of glass pre-treatment on the nucleation of semi-transparent gold coatings

Coatings of gold nanoparticles with a uniform film texture and a neutral blue hue may be applied to glass by an aqueous process and such coatings have recently been proposed for architectural applications. Here, we show that the optical transmission spectrum of these coatings is directly related to the interplay between the nucleation, growth and aggregation of the particles. In particular, prior treatments of the glass substrate in 1:1 sulfuric acid (H2SO4), 98% H2SO4 and buffered hydrofluoric acid (HF) exerted a strong influence on the subsequent particle size and coverage, which is explained here in terms of contact angle and its effect on rates of nucleation. The rate of nucleation on the surface treated with HF is estimated to be twice that of the surface treated with 98% H2SO4. The color of the coatings is the result of inter-particle plasmonic interactions and is, therefore, also controlled by the nature of nucleation and growth process.