Photobiocidal-triboelectric nanolayer coating of photosensitizer/ silica-alumina for reusable and visible-light-driven antibacterial/antiviral air filters

Outbreaks of airborne pathogens pose a major threat to public health. Here we present a single-step nanocoating process to endow commercial face mask filters with photobiocidal activity, triboelectric filtration capability, and washability. These functions were successfully achieved with a composite nanolayer of silica-alumina (Si-Al) sol-gel, crystal violet (CV) photosensitizer, and hydrophobic electronegative molecules of 1H, 1H, 2H, 2H-per-fluorooctyltriethoxysilane (PFOTES). The transparent Si-Al matrix strongly immobilized the photosensitizer molecules while dispersing them spatially, thus suppressing self-quenching. During nanolayer formation, PFOTES was anisotropically rearranged on the Si-Al matrix, promoting moisture resistance and triboelectric charging of the Si-Al/PFOTES-CV (SAPC)-coated filter. The SAPC nanolayer stabilized the photoexcited state of the photosensitizer and promoted redox reaction. Compared to pure-photosensitizer-coated filters, the SAPC filter showed substantially higher photobiocidal efficiency (-99.99 % for bacteria and a virus) and photo-durability (-83 % reduction in bactericidal efficiency for the pure-photosensitizer filter but-0.34 % for the SAPC filter after 72 h of light irradiation). Moreover, after five washes with detergent, the SAPC filter maintained its photobiocidal and filtration performance, proving its reusability potential. Therefore, this SAPC nanolayer coating provides a practical strategy for manufacturing an antimicrobial and reusable mask filter for use during the ongoing COVID-19 pandemic.

Automated summary

This study presents a nanocoating process for manufacturing antimicrobial and reusable mask filters. The nanocoating endows the filters with photobiocidal activity, triboelectric filtration capability, and washability, while maintaining their performance and durability under light irradiation. After washes with detergent, the filters still maintain their antimicrobial and filtration performance. This nanocoating provides a practical solution for tackling the COVID-19 pandemic.