School of Civil and Environmental Engineering

 Ph.D. Thesis Defense Announcement

 Visible to UV Upconversion Materials for Surface Disinfection and Photocatalyst Sensitization

 by:

Stephanie L. Chinnapongse Cates

 Advisor: 

Dr. Jaehong Kim (CEE)

Committee Members: 

Dr. John Crittenden (CEE); Dr. Ching-Hua Huang (CEE); Dr. Angus Wilkinson (CHEM), Dr. Sotira Yiacoumi (CEE)

Date & Time: April 3 @ 11:00am

Location:  Mason 3133

Abstract: 

UV radiation is utilized in a number of environmental technologies, most notably for the disinfection of water, air, and surfaces through the use of UVC fluorescent lamps. Recently, our group developed a luminescent material that could emit germicidal UVC simply by irradiating it with a household fluorescent lamp, thus introducing a new type of antimicrobial surface powered by low-intensity visible light. The materials were doped with praseodymium ions (Pr3+) which have the unique capability of converting visible light to higher energy UV using an optical mechanism called upconversion. While visible-to-UV upconversion materials appeared promising for environmental application --particularly because solar irradiation could be used for their activation --their practical application was thwarted by low light conversion efficiencies. Herein we discuss the pursuit of new material forms and modifications designed to improve the efficiency of Pr3+-based upconversion systems. These enabled successful enhancement of antimicrobial activity and led to a proof of concept for upconversion-sensitized TiO2 photocatalysis. Correlations between material properties and optical behavior will be presented, followed by commentary on how these strategies might be used to further advance upconversion systems toward environmental application.