Concentration of deposit patterns by nanoparticles modified with short amphiphiles

Abstract

Depositing drops of a nanoparticle suspension onto a substrate is a simple way to model the processes that occur during printing of macroscopic structures from nanoparticles. We investigated the effect of adding short chain length amines on the deposit patterns formed by fused silica nanoparticles. Adding amphiphiles which adsorb at the particle surfaces is expected to modify their wettability and stability. Hence it should be possible to tune the particle interactions and control the patterns formed by the deposited particles. We probed the effects of amine adsorption on the silica particles by measuring the changes to the electrokinetic properties and wettability of the particles. Adding short chain amines to concentrated dispersions of silica nanoparticles induces a transition from a ring-shaped morphology to a more uniform, dot-shaped deposit during evaporative drying. We characterised the size and shape of deposits formed as a function of amphiphile chain length and concentration, and the particle concentration. The variation in the deposition pattern with the alkyl chain length can be accounted for by considering the effect of amine adsorption on the interactions between the particles and the interactions between the particles and the substrate. This is the first report showing how short chain alkylamines can be used to tune the deposition of silica nanoparticles.