Electrospray formation of ring-shaped silica nanoparticles

Electrospray is one of the processes employed for the production of silica nanoparticles (NPs). We have experimentally determined that not only spherical but also ring-shaped NPs can be manufactured by electrospray, and that the shape of the NPs is dependent on ambient humidity and the substrate on which the NPs are deposited. Although the effect of humidity that reflects the evaporation characteristics of the suspension during flight has been reported, we have experimentally determined that the affinity of the sol suspension and the substrate play a crucial role in the formation of torus silica NPs.