Effects of Particle Size on the Monolayer Structure of Nanospheres

Abstract

In this study, the effects of particle size on the monolayer structure of silica nanospheres are investigated by changing the diameters of particles from 10 nm to 100 nm. Suspensions of silica nanoparticles coated on a glass substrate by a bar coater are evaporated to give a monolayer. The structures of the monolayers are observed by scanning electron microscopy (SEM) and quantitatively evaluated in terms of pair correlation function and the Delaunay triangulation. For the comprehension of dominant factors in self-assembling process, the experimental results are compared with the results obtained by simulation. The monolayer of the particles, the diameter of which are 11.4 nm, cannot be fabricated at high coverage corresponding to the particle weight fraction of the suspension. The pair correlation function of the monolayer shows that particles do not contact with each other and are arrayed with a 1 nm gap. A feasible model for the process suggests that hydration force between silica surfaces prevents their contacting, and that particles are arrayed with a constant distance.