Nanocellulose-reinforced air filter with gradient hierarchical structure for highly effective and reuseable antibacterial air filtration

Since the outbreak of COVID-19, microbial pollutants in the air have attracted people's attention. Existing air filters can only intercept microorganisms but cannot inactivate them. Thus, there is an urgent need to design air filters with antibacterial properties. In this study, we used vacuum-assisted filtration to adjust the pore structure of the traditional glass fiber air filter with cellulose nanofiber (CNF) and tempo-oxidized nanocellulose (TNF), and constructed a graded air filter (GCT) with gradient pore structure and Janus structure. At the same time, the addition of nanofibers increased the mechanical properties of the glass fiber air filter. Finally, the filters were endowed with good photothermal properties and stable antibacterial properties by adding antibacterial agents from previous studies (GCT/Ag-3). GCT/Ag-3 responded under near-infrared light, achieving a 99.9 % antibacterial rate against E. coli and S. aureus within 90s, and maintaining this high efficiency after 6 cycles, which provides a feasibility for the design of antibacterial air filter.