RAPID: Defect-Chemistry Design of Titanium Dioxide for Enhanced Virucidal Photodynamic Properties

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NON-TECHNICAL DESCRIPTION: The goal of this research project is to develop synthesis and processing routes to optimize the efficacy of titania-based nanoparticles for inactivating SARS-CoV-2 surrogate coronaviruses. The chemistry and stoichiometry of titania particles are tuned through a novel flow-synthesis processing route and subsequent thermal annealing to make the material photoactive in the visible-light range of the electromagnetic spectrum. Such light activation leads to the production of reactive oxygen species, which are believed to be central to the antiviral activity of such oxide materials. Being able to control and optimize the antiviral activity of materials such as titania, which can easily be coated onto surfaces or integrated into fibers, can have direct and immediate impact on the production of antimicrobial coatings and personal protective equipment (PPE). As such, the research results are proactively directed towards groups researching and developing PPE materials for the COVID-19 pandemic. The graduate students involved in the research are team-mentored in a highly interdisciplinary and societally relevant research activity that spans materials research, photochemistry, virology, and materials manufacturing.TECHNICAL DETAILS: This research program aims to develop the fundamental science linking the chemistry of titanium dioxide, or titania, to its antiviral properties. The research is motivated by the urgent need to develop coatings and personal protective equipment (PPE) that can inactivate the COVID-19 virus. In this research, precise synthesis of titania nanoparticles is achieved via a micro-scale flow synthesis platform with in situ diagnostics. The high-throughput experimental platform enables the research team to study systematically the important variables of particle size, phase, and doping concentrations on the light absorption and photodynamic properties of titania. An important variable in the study is oxygen stoichiometry, which is systematically controlled through low-partial-pressure oxygen annealing. The reduction reaction induces oxygen vacancies into the titania lattice, which, in turn, lower the optical band gap of the material. The consequences for reactive oxygen species generation, which are critical for antiviral efficacy, have not, however, previously been established. Therefore, this research measures the effects of nanoparticle stoichiometry on the generation of individual reactive oxygen species: superoxide, singlet oxygen, hydrogen peroxide and hydroxyl radicals under visible light illumination. Finally, the efficacy for inactivating SARS-CoV-2 surrogate coronaviruses is assessed, allowing for the development of full synthesis-structure-property-function relationships for this important antimicrobial photodynamic material. Moreover, the research translates the knowledge and processing conditions of the most efficacious materials to groups producing antiviral materials for the COVID-19 crisis. The participating graduate students are involved in all aspects of this highly interdisciplinary research activity, which provides them unique experience in the material design process, while contributing to practical solutions for the containment of the COVID-19 virus.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.