Preparation of a composite coating film via vapor induced phase separation for air purification and real-time bacteria photocatalytic inactivation

Infectious diseases resulted from transmitting of bacteria or virus like COVID-19 via air-borne droplets have brought severe threat to human beings worldwide. Cutting the spreading paths to obtain clean air is one of the promising strategies to prevent people from such dangerous diseases. In this work, we have employed a strategy of spray coating in combination with vapor induced phase separation to prepare a composite coating film to fulfill that purpose. A stable mixture suspension containing micelles of block copolymer of poly(styrene-block-butadiene-block-styrene) and TiO(2) nanoparticles was sprayed onto stainless steel mesh to evaporate solvent in non-solvent vapor atmospheres. A water vapor atmosphere and an ethanol vapor atmosphere were in turn employed to improve the mechanical strength of the obtained coating film. The porous microstructure, the porosity, and the superhydrophobicity of the coating film were carefully characterized and analyzed. The air pressure-drop of the coating film was determined to be lower than 100 Pa, indicating a high air permeability. Moreover, a foggy air containing E. coli was pressed through the coating film via a home-made apparatus to simulate the air purification system, where E. coli contained air-borne droplets were intercepted by the film matrix in a physical manner, and the bacteria was photocatalytically inactivated at the meantime. A filtration efficiency of 99.7% and a 99.6% efficiency of real-time photocatalytic inactivation of E. coli demonstrate the promising potential of the coating film.