Controlling self-assembled structure of Au nanoparticles by convective self-assembly with liquid-level manipulation

Microwire networks composed of noble metal particles are promising for the use of transparent conductive films. Bottom-up approaches can offer a route to establishing a fabrication technique that is robust and cost-effective, and template-assisted self-assembly techniques are widely used. However, they require additional processes to prepare templates and generally suffer from the difficulty in a large-scale fabrication. A template-free technique thus waits to be developed. In the present study, we explore a template free technique to fabricate colloidal networks of Au nanoparticles. We combine the convective self-assembly method with a liquid-level manipulation scheme in which the suspension is periodically pumped out. By using the technique, we successfully fabricate stripe, grid, and triangle patterns with controlled periodicity and examine the relationship between operation parameters and the resultant structures. We then measure the transparency and conductivity of a grid pattern to demonstrate the property as the transparent conductive film.