The COVID-19 pandemic has led to recommendations or requirements for the use of face masks in many public places. Face masks made of various cloth materials can filter aerosol particles, such as those released by a cough or sneeze, and help to reduce the spread of diseases, including COVID-19. However, live bacteria or viruses on the surface of the masks could still be contagious.

Gang Sun, University of California, Davis, USA, and colleagues have developed a functionalized cotton fabric that releases reactive oxygen species (ROS) when exposed to daylight and kills microbes attached to the fabric. The team prepared the antimicrobial fabrics by activating cotton fabric in an NaOH solution and then attaching positively charged chains of 2-diethylaminoethyl chloride (DEAE-Cl) to the fabric. Then, they dyed the functionalized cotton using anionic photosensitizers, which release ROS upon exposure to light. These dyes were attached to the cationic chains by strong electrostatic interactions.

The team found that a fabric made with the dye rose Bengal as the photosensitizer killed over 99.9 % of bacteria (such as E. coli) added to the fabric within 60 min under daylight exposure and inactivated over 99.9 % of T7 bacteriophage, a virus thought to be more resistant to ROS than some coronaviruses, within 30 min. The material can be hand-washed at least ten times and exposed to sunlight for at least seven days without losing its antimicrobial activity. According to the researchers, the fabric is promising for making reusable, antibacterial, and antiviral cloth face masks and protective suits.

• Daylight-Induced Antibacterial and Antiviral Cotton Cloth for Offensive Personal Protection,
  Peixin Tang, Zheng Zhang, Ahmed Y El-Moghazy, Nicharee Wisuthiphaet, Nitin Nitin, Gang Sun,
  ACS Appl. Mater. Interfaces 2020.
  https://doi.org/10.1021/acsami.0c15540