Size and concentration controlled growth of porous gold nanofilm



At an air/water interface, diffusion-limited aggregation (DLA) of gold nanoparticles can form porous gold thin films. This porous film roughly consists of a network of irregular nanowires. For this air–water system, external parameters like temperature are well studied, while the influence of internal parameters, e.g., the size and concentration of the nanoparticles, have not been studied in detail. Here, we report on the growth of porous gold nanofilms for different nanoparticle sizes and concentrations to get a relationship between the morphology of the films and the internal parameters. The gold nanoparticles were synthesized by reducing HAuCl4 using sodium citrate. Transmission electron microscopy (TEM) characterization showed a linear relation between the formed gold nanowires and the concentration of HAuCl4 if the concentration of sodium citrate is unchanged. A linear dependency was also found between the wire diameter and the gold nanoparticle concentration, and between the wire diameter and volume fraction of the nanoparticles. The electrical resistance of the films was measured, showing a linear relation between resistance and the inverse of the cross-sectional area of the nanowires. This study shows the relation between the morphology and resistance of the grown porous films and the controllable internal parameters that will be useful in further exploration of this thin-film growth method.