Thin Film Coatings Prepared by Direct Thermophoretic Deposition of Flame-Made Nanoparticles

Abstract

This study reports the development of a one-step method for the production of thin film coatings made with metal oxide nanoparticles. An aerosol flame synthesis system is used to produce monodisperse, ultra-fine nanoparticles of different metal oxide, by changing the precursor fed to the flame. The flame reactor is a fuel- lean reactor of ethylene and air. Flame-synthesized nanoparticles are directly deposited by thermophoresis onto different substrate by means of a rotating disc. Substrates were mounted onto the rotating disc that repetitively passes through the flame. Convection due to the rotational motion cooled the substrates, on which particles were deposited as films by thermophoresis. Such a system allowed to obtain submicron coatings of different thickness and porosity, by varying the total time of deposition. Different substrates can be coated using this method, such as aluminum and steel plate. Particle and coating characterization is performed by means of Differential Mobility Analysis, Raman and X-Ray Diffraction spectroscopy, and UV-Vis absorption. A preliminary analysis of the antimicrobial activity of TiO₂ nanoparticle coatings produced with this method has been performed against Candida Albicans, and compared to that of commercial TiO₂ nanopowder. The results are promising for using titania films as protective coatings for applications where an antimicrobial activity is required, such as self-cleaning materials able to reduce microbial infections.