Air Flow Disinfection from COVID-19 Based on Doped Atanase Coating Using Atmospheric Plasma

Abstract

Currently UV disinfection equipment is used to some extend to combat COVID-19 pandemic in high human traffic areas. Infections spread very quickly from person to person inside of closed air flow systems as in airplanes. Often using this equipment is prohibited due to harmful UV radiation and ozone emission.Therefore, safer solution is needed. Adding hydroxyl radicals to air flow is equally efficient to UV/ozone in virus disinfection, but safer as neither UV used, nor ozone generation.UV disinfection equipment market projects to reach USD 9.2 billion by 2026 from an estimated USD 4.8 billion in 2021, at a CAGR of 14.0% from 2021 to 2026. This marketplace can be captured by the hydroxyl generators.Hydroxyl radicals attack essential cell components and are therefore lethal to pathogenic viruses and bacteria – both in the air and on surfaces. Pathogenic viruses suffer from oxidation of their surface structures. Hydroxyl radicals disrupt the lipid envelope and/or capsid around the virus, causing lysing.However, the rate of generation of these radicals should exceed 1015 OH molecules cm−3s−1 to reach a globally averaged OH concentration ([OH]g) above 106 molecules cm−3 to inactivate SARS with the same efficiency as the UV light. The anatase TiO2 particles are used to generate these hydroxyl groups through photocatalytic reaction. The photon flux around of 2 × 10 15 photons cm − 2 s−1 is required to achieve this rate of the hydroxyl generation. Pure atanase has wide band gap – thus need UV for photocatalysis, and low quantum yield due to electron-hole recombination. We solve these problems by modifying band gap and by using small nanoparticles.We use Nitrogen doping of TiO2 to narrow the band gap. Thus, photocatalysis under visible light is enabled, no UV required. We use 20 nm nanoparticle coating instead of thick blanket TiO2 films thus mitigating hole recombination and increasing quantum yield.Efficiency is additionally increased by enlarging the surface area - laminate nanoparticles onto the 3D light transmitting hollow article, like matrix made from the fused together capillaries with the inner diameter around 0.5 mm and length around 5-10 mm. It increases the rate of generation of the hydroxyl groups due to accessibility of the photons to the TiO2 nanolayer illuminated from outside and inside. Also, the photocatalytic process can be promoted by electric field applied to the matrix . The field separates charge carriers thus reducing the recombination between electrons and holes and, thus better quantum yield, improved photocatalytic performance.With our atmospheric plasma beam technology and equipment we fabricate the hydroxyl reactor. We form a 3D matrix laminated by the TiO2 nanolayer. Our laminating instrument is a focused plasma beam generated by the atmospheric pressure inductively coupled plasma (ICP) discharge in nitrogen. Precursor is a commercial anatase TiO2 nanoparticles injected into this discharge. Nitrogen atoms incorporate into the interstitial positions of the TiO2 lattice of the nanoparticles. The supersonic plasma beam is generated by the nozzle attached to the plasma reactor and the TiO2 nanoparticles with increased nitrogen content are deposited on the inner walls of the capillaries of the matrix.This laminated matrix is encircled by the top and bottom metal meshes connected to the high voltage capacitor. This is a key part of the hydroxyl generator incorporated into the racetrack-like bore of the commercial Dyson air purifier. The matrix is positioned between two flanges closing the bore of the Dyson purifier from both sides. One of them supports the LED emitting photons piercing the matrix and the opposite one supports the mirror directing the reflected light back to the matrix and doubling the illumination. Humid air flow is generated by the Dyson air filter and injected into the gap between the LED and the top of the matrix. Water thus delivered to the TiO2 nanolayer for photocatalytic hydroxyl radicals’ generation.It is reasonable to suppose that nanocoating, doping and electric field novelties will lead to a synergistic effect and increase photocatalytic activity to inactivate SARS and its highly contagious Delta variant. Inserting our hydroxyl generator into commercial Dyson air purifier increases cost-efficiency and time-to-market.