Band edge energies (Table ) were measured by diffuse reflectance UV-vis spectroscopy (DRUV-vis). In short, samples were intimately ground with magnesium oxide (MgO; Sigma-Aldrich, 99.995%) in a 1:10 ratio of Ti-silicate to MgO by mass. These samples were loaded into a Harrick diffuse-reflectance accessory and spectra were obtained using a spectrophotometer (Agilent, CARY5) with pure MgO as the background.