Diseases caused by inhalation of volatile organic compounds (VOCs), air-borne bacteria, viruses and fungi are a ubiquitous concern in healthcare and other indoor settings. Thus, developing air purification technology that could disinfect pathogens and reliably detect, monitor and neutralize VOCs is essential for maintaining public health. Reactive oxygen species (ROS) are established disinfecting agents and are known to react with multiple VOCs. However, current ROS-based air purifiers are limited by high energy production, health hazards and inefficient disinfection due to time consuming and impractical use. While VOC detectors suffer from low selectivity and reproducibility and are not intended for remediation. It has been confirmed that single-walled carbon nanotubes (SWCNTs) generate ROS in aqueous media when illuminated with solar radiation. However, low efficiency due to competitive reactions between ROS and water and unclear reaction mechanisms hinder its practical application. Here, SWCNTs were studied in a non-aqueous ionic liquid (IL) to form a suspension system for generating superoxide (O2−) under UV light. A new method to in-situ monitor the O2− level in the system was established using electrochemical characterizations. The O2− level was quantitatively determined by combining cyclic voltammetry and chronoamperometry. The SWCNTs/IL system generated 4.11 mM of O2− in a mini-scale generator, which was in excess of germicidal levels for ROS and successfully inhibited E. Coli growth and the SARS-CoV-2 spike protein binding to the human ACE2 receptor. The kinetics of the photodynamic effect and the stability of the materials were also investigated using electrochemical techniques and spectroscopy. The IL proved to be an ideal media that could extend the lifetime of O2− from a few microseconds in water to at least 65 h, while the SWCNTs could continuously generate O2− for at least 540 h under UV radiation. Moreover, by combining this method with linear discriminant analysis (LDA), the system was found to selectively detect, monitor and neutralize several hazardous VOCs via reaction with O2−. This work is intended for future application as a completely green, sustainable and safe method for air quality monitoring and purification.
