A 3D-printed pre-filter with a crystal violet–gold nanocluster hybrid for a reusable visible-light-activated antimicrobial air filtration system

Abstract

Airborne microorganisms pose a persistent threat to public health. In this study, we present a reusable, visible-light-activated antimicrobial filtration system that combines a crystal violet–gold nanocluster (Au@CV)-coated pre-filter with a conventional dust-capturing main filter. Under visible-light irradiation, the Au@CV pre-filter generates reactive oxygen species (ROS), enabling dual antimicrobial mechanisms: (i) direct inactivation of microbes deposited on the pre-filter surface and (ii) airflow-assisted ROS inactivation of microorganisms captured on the downstream main filter. The study of photobactericidal mechanisms shows that Au nanoclusters on CV promote charge-carrier transfer and redox reactions, leading to the generation of multiple ROS. The Au@CV filter achieved up to a 4.7-log reduction in viable bacteria after 3 h of exposure to visible light. Furthermore, ROS transported from the pre-filter to the main filter enabled ∼98% antibacterial efficiency even in the absence of airflow, while the performance strongly depended on airflow direction and velocity, underscoring the critical role of airflow in ROS delivery. Additionally, the Au@CV filter remained stable after the tape adhesion test and water immersion. We believe that this work can open a new avenue for designing and realising practical antimicrobial technology against the threat of infectious bioaerosols.