Recently, bioaerosols, including the 2019 novel coronavirus, pose a serious threat to global public health. Herein, we introduce a visible-light-activated (VLA) antimicrobial air filter functionalized with titanium dioxide (TiO2)-crystal violet (CV) nanocomposites facilitating abandoned visible light from sunlight or indoor lights. The TiO2-CV based VLA antimicrobial air filters exhibit a potent inactivation rate of ~99.98% and filtration efficiency of ~99.9% against various bioaerosols. Under visible-light, the CV is involved in overall inactivation by inducing reactive oxygen species production both directly (CV itself) and indirectly (in combination with TiO2). Moreover, the susceptibility of the CV to humidity was significantly improved by forming a hydrophobic molecular layer on the TiO2 surface, highlighting its potential applicability in real environments such as exhaled or humid air. We believe this work can open a new avenue for designing and realizing practical antimicrobial technology using ubiquitous visible-light energy against the threat of infectious bioaerosols.

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Real-time on-site monitoring of bioaerosols in an air environment is important for preventing various adverse health effects including respiratory diseases and allergies caused by bioaerosols. Here, we report the development of an on-site automated bioaerosol-monitoring system (ABMS) using integrated units including a wet-cyclone bioaerosol sampler, a thermal-lysis unit for extracting adenosine triphosphate (ATP), an ATPdetection unit based on the immobilization of luciferase/luciferin for bioluminescence reactions, and a photomultiplier tube-based detector. The performance of the bioaerosol detection system was verified using Escherichia coli (E. coli) as a model source. Each unit was optimized to process ∼9.6 × 10 5 times the concentrated ratio of collected bioaerosol samples, using a 3 min lysis time to extract ATP, and has a detection limit of ∼375 colony-forming units (CFUs)/mL with more than 30 days of stability for the immobilizedluciferase/luciferin detection unit supported by a glass-fiber conjugation pad. After the integration of all units, the ABMS achieved E. coli bioaerosol monitoring with continuous detection at 5 min intervals and a minimum detection limit of ∼130 CFU/m air 3 . Furthermore, the rapid responsivity and stable operation performance of the ABMS under test-bed conditions and during a field test demonstrated that the ABMS is capable of continuously monitoring bioaerosols in real-time with high sensitivity. The monitoring system developed here with immobilization strategies for bioluminescence reactions triggered by ATP extracted from collected bioaerosol samples using a simple heat-lysis method may help establish sustainable platforms to obtain stable signals for the real-time detection of bioaerosols on-site.

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