Self-Organization of Particles during the Evaporation of Droplets of a Colloidal Solution of a Nanostructure Placed on a Quartz Substrate

An experimental study of self-organization processes that arise during evaporation of droplets of a colloidal solution of nanocarbon in ethanol from the surface of quartz glass is presented. The influence of the distilled-water content in the colloidal solution and the temperature gradient on the substrate on the distribution of nanoparticles and their agglomerates over the contact area of the drop with the surface are discussed. The evaporation of a multicomponent droplet is examined and described from the viewpoint of mass transfer by identifying the characteristic mechanisms of fluid motion in the droplet as the main cause of motion of nanocarbon nanoparticles. A detailed analysis of nanolayers and nanoparticle agglomerates deposited by droplet coating is performed, and the optimal conditions in terms of the substrate temperature and the pure-water content are determined, under which the most uniform spatial distribution of nanoparticles over the contact area of the droplet with the substrate is observed, as well as additional regimes with spatially uniform distributions of nanoparticle agglomerates (more than 10 μm).