His current research interests include: (1) fundamental phosphor development for improving the efficiency of visible-to-UV upconversion; (2) development of visible light-activated photocatalysts; (3) microbial inhibition and singlet oxygen photosensitization by silicon nanocrystals; and (4) material technologies for enhancing solar water disinfection for the developing world. This research integrates environmental engineering with materials science and physical chemistry. Students in the Cates Lab will utilize solid state synthesis methods, laser spectroscopy, wet chemical experiments, microbial enumeration, and crystallography.