Defect complex formation in TiO2 nanoparticles by sub-band excitation

TL;DR

This study investigates defect formation in TiO2 nanoparticles under sub-band excitation, revealing complex defect states and their optical emissions, with ESR measurements showing defect evolution upon light exposure.

Contribution

It introduces a detailed analysis of defect complex formation in TiO2 nanoparticles induced by sub-band excitation, combining optical and ESR techniques.

Findings

Identification of polychromatic emission due to defect states

Detection of Ti+3 and VO defects via ESR in dark conditions

Formation of Ti+3-VO and Ti+4-V+O defect complexes under visible light

Abstract

Anatase TiO2 is an indirect band-gap material with large degree of sub-stoichiometry, selective excitation of its native defect reveals polychromatic emission in blue, green and red spectral regions due to self trapped excitons and singlet-singlet transition of defect states. Electron spin resonance measurement in dark shows presence of isolated Ti+3, deep lying, and surface lying VO at 1.986, 2.04 and 2.023 g values respectively, whereas , on exposure with visible light in situ ESR measurement reveals the formation of defect complex of Ti+3-VO and Ti+4-V+O.