title: Water as probe molecule for midgap states in nanocrystalline strontium titanate by conventional and synchronous luminescence spectroscopy under ambient conditions.
abstract: Alkaline earth metal titanates are broad bandgap semiconductors with applications in electronic devices, as catalysts, photocatalysts, sorbents, and sensors. Strontium titanate SrTiO3is of interest in electronic devices, sensors, in the photocatalytic hydrogen generation, as catalyst and sorbent. Both photocatalysis and operation of electronic devices rely upon the pathways of relaxation of excited charge in the semiconductor, including relaxation through the midgap states. We report characterization of nanocrystalline SrTiO3at room temperature by "conventional" vs. synchronous luminescence spectroscopy and complementary methods. We determined energies of radiative transitions in the visible range through the two midgap states in the nanocrystalline SrTiO3. Further, adsorption and desorption of vapor of water as "probe molecule" for midgap states in the nanocrystalline SrTiO3was studied, for the first time, by luminescence spectroscopy under ambient conditions. Emission of visible light from the nanocrystalline SrTiO3is significantly increased upon desorption of water and decreased (quenched) upon adsorption of water vapor, due to interactions with the surface midgap states.
authors.affiliation: Chemistry Department, Rutgers University, 315 Penn St., Camden, NJ 08102, USA.
authors.forename: Sean
authors.initials: S
authors.lastname: Taylor
authors.affiliation: Chemistry Department, Rutgers University, 315 Penn St., Camden, NJ 08102, USA. Electronic address: alexsam@camden.rutgers.edu.
authors.forename: Alexander
authors.initials: A
authors.lastname: Samokhvalov
keywords: Luminescence; Midgap state; Strontium titanate; Synchronous; Water adsorption