Efficient N95 Mask Disinfection Method with Photon Up-and-Down Conversion Materials

The covid-19 pandemic poses many challenging problems to physicists. For example, what are the best virus disinfection methods? Recent research has shown that under a 254nm UVC lamp, N95 masks can be disinfected and reused. However, 254 nm irradiation is not very efficient as UV photons bounce inside the mask and cause unnecessary photodegradation to the mask polymers. As an alternative approach, we propose embedding upconverting nanoparticles (UCNPs) and photon down-conversion materials inside the mask. By illuminating the mask with near infrared (NIR) light that can more efficiently penetrate deep into the mask layers, the UCNPs will convert NIR light into UV at the mask fiber surfaces for virus disinfection, while the photon down-conversion material within the fibers will convert the UV back to NIR before it has a chance to cause irreversible damages. One further advantage of this method is that we have now shown that certain UCNPs can emit in the far UVC region (200nm). Unlike 254nm UV light, which is detrimental to human skin and eyes, the shorter wavelength of far UVC is unable to penetrate through even the top layer of skin cells. Our disinfection method thus holds potential for active disinfection, that is, disinfecting the surfaces of objects during human presence.