A capture and inactivation system against pathogens in indoor air using copper nanoparticle decorated melamine sponge hybrid air filters

The widespread transmission of coronavirus disease (COVID-19) poses an urgent need for air filter development to prevent pathogens from spreading in indoor spaces. This paper aims to introduce an in situ growth dip coating approach to demonstrate a simple and eco-friendly synthesis of copper nanoparticle (Cu NP) decorated melamine sponge (Cu/MS) air filters. The results showed that the Cu NPs tightly adhered to the melamine sponge (MS), and that their amount was controllable. Introducing increasing quantities of Cu NPs into the MS proportionally improved pathogen capture and inactivation efficiencies. The bare MS showed 94.54% capture efficiency, which was greatly improved up to 96.36% for Cu/MS (1.17 Cu wt%) and 100% for Cu/MS (5.69 Cu wt%) after 30 min. The capture performance of the Cu/MS air filter was stably maintained above 99% after multiple washing cycles due to the strong chemically grown Cu NPs on the MS carrier, indicating its reusability. Additionally, Cu/MS exhibited almost complete inactivation of E. coli (>99.99%) in saline, indicating that Cu NPs play a major role in the bacteria-killing function of Cu/MS. Taking advantage of the eco-friendliness, reusability and dual-functionality, the synthesized Cu/MS sponge filter would be an ideal candidate for the current and future pandemic situations.