Visible-Light-Active Organic Dye/Alumina-Silicate Nanocomposites for Photobiocidial-Triboelectric Fabric Coating

Controlling airborne microorganisms (called bioaerosols) is vital for protecting public health. In the 21st century, bioaerosols have threatened public health in various forms, from severe acute respiratory syndrome in 2002, to pandemic influenza A in 2009, to Middle East respiratory syndrome coronavirus in 2012 and COVID-19 in 2019 [1]. COVID-19 is still an ongoing threat, with more than 536 million infections and 6.31 million deaths worldwide (as of 15 June 2022) [2]. Therefore, there is a need to develop innovative bioaerosol-inactivating materials. Various fiber-based filters composed of organic or inorganic antimicrobial materials, such as copper, silver nanoparticles, chitosan, and natural products, have been developed to filter against bioaerosols [3]. However, these air filters effectively inactivate only microorganisms in direct contact with antimicrobial agents; therefore, their effectiveness gradually decreases as dust accumulates over the antimicrobial material. In addition, conventional filter disinfection technologies based on ultraviolet (UV) irradiation, plasma, and thermal energy have been developed; however, these technologies require additional energy and devices [4].<br/>Recently, visible-light–driven (VLD) biocidal technologies, based on sunlight or indoor light energy, have been a focus of research in the field of photocatalysis [5]. VLD biocidal surfaces or air filters have been prepared using photosensitizing dyes such as triarylmethane, phenothiazine, and xanthene derivatives [6]. The photosensitizing dyes are inexpensive and have various applications; however, because of their high affinity to water, they easily leach into the environment when they come into contact with moisture [7]. To become incorporated into polymer fibers, the dyes need to be firmly immobilized to guarantee the durability and washability of the fibers.<br/>We introduce a novel fiber functionalization method that uses silica-alumina sol-gel (SAS) to endow a fibrous membrane with photocatalytic biocidal activity and reusability. The transparent SAS matrix immobilizes crystal violet (CV) photosensitizer dye and binds electronegative 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOTES) molecules to its surface [8]. Moreover, the SAS matrix enhances the dispersity of the photosensitizers (suppressing self-quenching) and protects them from degradation by ROS, enhancing the photodurability. The SAS/PFOTES-CV (SAPC) nanolayer produced more ROS <i>via</i> enhanced redox reaction and showed excellent photobiocidal efficiency (~99.99% for bacteria and a virus) under visible light irradiation (3 h, 7.2 mW cm^-2) and photodurability (~83% reduction in bactericidal efficiency for the CV alone but ~0.34% for the SAPC filter after 3 days of light irradiation). Moreover, PFOTES bonded to the SAS thin film increased water resistance and triboelectrification ability of the filter. The SAPC filter maintained its filtration and antimicrobial properties after cyclic washing tests, which demonstrates that the excellent reusability. Our SPAC-based nanolayer coating technology is applicable to various textiles of face masks and protective clothing and can control the spread of COVID-19 and other airborne contagious diseases.<br/><br/><b>References</b><br/>[1] A. Nalbandian, <i>et al.</i>, <i>Nat. Med</i>. 27 (<b>2021</b>) 601–615.<br/>[2] “COVID-19 Dashboard.” The Center for Systems and Engineering (CSSE) at Johns Hopkins University.<br/>[3] S. Kumar, <i>et al</i>., <i>Nano Lett</i>. 21 (<b>2021</b>) 337–343.<br/>[4] R. K. Campos. <i>et al</i>., <i>ACS Nano</i> 14 (<b>2020</b>) 14017–14025.<br/>[5] P. Li <i>et al</i>, <i>Nat. Commun.</i> 10 (<b>2019</b>) 2177.<br/>[6] P. Tang <i>et al</i>., <i>ACS Appl. Mater. Interfaces</i> 12 (<b>2020</b>) 49442–49451.<br/>[7] K. J. Heo, <i>et al</i>., <i>Nano Lett.</i> 21 (<b>2021</b>) 1576–1583.<br/>[8] S. B. Jeong <i>et al.</i>, <i>Chem. Eng. J.</i> 440 (<b>2022</b>) 135830.<br/><br/><b>Acknowledgement</b><br/>This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2022R1F1A1074255).<br/><br/><b>*Corresponding Author</b>: D. Y. Choi; E-mail: [email protected]