Ï㽶ÊÓƵ

Date: Thursday, November 17th 2022 |ÌýTime: 12:00 pm |ÌýMacdonald Engineering Building RM: 267Ìý

*The session will also be accessible via zoom

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Light is the most abundant and fastest moving energy resource on Earth. Sunlight is the primary driver of many environmental transformation and decay processes, while environmental remediation technologies that harness sunlight can be driven by a sustainable energy source, typically do not require consumable chemicals, and have greater mobility for use in isolated and off-grid locations. This seminar will discuss processes and technologies that harness solar energy for water treatment, with particular emphasis on disinfection of viral pathogens. Disease causing pathogens remain the most acutely deadly category of environmental contaminant. Compared to other types of pathogens, much less is known about the environmental transmission of viruses due to the challenges presented in detecting, characterizing, and culturing these smallest biological organisms. Research aiming to understand the fate and persistence of viruses in the environment, and the development of innovative and efficient methods to detect and control their spread has never been more vital. Understanding light induced inactivation is key to predicting the fate of viral pathogens in the environment, while engineered light-based treatment systems provide opportunities to develop sustainable, practical, and effective methods for controlling viral pathogens.

A meta-analysis of available sunlight inactivation rate constants for viruses and their surrogates revealed little correlation between pathogens and their common surrogates, as well as knowledge gaps in the wavelength dependent damage mechanisms. To study these mechanisms, we used a genome-wide PCR approach to study photodamage in the genomes of human norovirus and a common surrogate bacteriophage MS2. In contrast to previous work indicating that UV inactivation occurs primarily through the formation of pyrimidine dimers which render the viral genome non-replicable after a single photon absorption event, we found that the single-hit inactivation assumption is invalid under simulated solar radiation, highlighting the need for further mechanistic analysis of genomic photoproducts and the contribution of non-genomic damage to viruses under environmentally relevant conditions.

Harnessing solar energy for water treatment is a highly desirable approach to provide safe water in resource limited locations. The preferred photocatalytic nanomaterial for water treatment applications, TiO₂, has a relatively wide bandgap, limiting its spectral overlap with the most abundant solar wavelengths. Nanomaterials exhibiting surface plasmon resonance can act as light antennae when incoming resonant light radiation generates an intense electric-field enhancement leading to absorption cross-sections many times greater than the size of the particle ─ essentially,Ìýthe particle can absorb more light than incident on it. Recently, we developed a novel nanomaterial enabled system for sustainable solar photothermal disinfection, leading to the first demonstration of direct solar nanoparticle-enhanced thermal inactivation of bacteria and viruses in drinking water. Likewise, we have synthesized composite plasmonic-photocatalytic nanomaterials that can enhance the light absorption properties of TiO₂Ìýpermitting more effective degradation of organic contaminants. We further optimize these approaches through the fabrication of prototype reactors from immobilized nanomaterial films for application in flow-through validation tests.

Dr. Stephanie Loeb

Dr. Stephanie Loeb is an Assistant Professor in the Department of Civil Engineering at Ï㽶ÊÓƵ. Prof Loeb's research interests encompass materials science and environmental engineering, with particular expertise in the areas of nanotechnology, photonics, and environmental virology. The use of light, a ubiquitous source of energy, is a common theme among her research projects, which aim to understand how light from natural and artificial sources drive environmental processes, and to develop novel light harnessing materials-based technologies for environmental remediation. Prior to joining McGill, she was a post-doctoral research fellow at Stanford and received her PhD from Yale University in Chemical Engineering. She has a MASc from the University of Toronto in Civil Engineering and completed her bachelor’s degree in Physics and Nanoscience jointly between UofT and the National University of Singapore.