EPR of Charge Carriers Stabilized at the Surface of Metal Oxides

Point Defects in Electron Paramagnetic Resonance

“…The total spin density on the Oion is therefore ρ tot = 0.832 [29]. The spin density values indicate that the unpaired electron wave function has a small s character, probably due to some degree of spin polarization, and that the unpaired electron spin density is mainly localized in a p orbital of oxygen as expected for an Oradical ion and as actually found for bulk examples of VO centers [28]. The axial symmetry of both g and A tensors and the comparison of their experimental values with those calculated by DFT unambiguously indicate that the hole is stabilized on the surface site having the lowest coordination.…”

Influence of Formate Adsorption and Protons on Shallow Trap Infrared Absorption (STIRA) of Anatase TiO2 During Photocatalysis

“…Electron and hole trapping occurs at defects such as oxygen/metal vacancies or at truncated crystallite surfaces. EPR studies have characterized many electron trap sites, ,− and to a lesser extent hole trap sites, ,, though most investigations have been carried out at low temperature and in vacuo to suppress the rapid annihilation of photogenerated electron–hole pairs. Spectroscopic insight into structural changes in the TiO 2 lattice could provide clarification of the chemical nature of trapping sites.…”

Charge trapping in TiO2 polymorphs as seen by Electron Paramagnetic Resonance spectroscopy

“…The initial light induced separation is followed by charge migration to the surface, charge trapping and, eventually, charge transfer to adsorbed entities. 10,11 All the above steps are the object of often sophisticated investigations and are still not yet fully understood. In particular the nature of the charge traps, their location (surface, subsurface, bulk), the stability of the trapped charge and their propensity to detrapping are all issues of vital importance.…”