Photoinduced chesorluminescence from radical processes on ZrO2 surfaces

Luminescence of photoactivated pristine and Cr-doped MgAl2O4 spinel

“…The similarity between the PhICL, PhL and ThL spectral characteristics infers that the physical relaxation associated with PhICL, at least partly, occurs through electron trapping by the excited A c c e p t e d M a n u s c r i p t states of Cr 3+ -states. Accordingly, based on the present results and the mechanisms reported elsewhere [7][8][9]18] we propose the following mechanism. The initial step is dissociation of molecular hydrogen on the surface-active hole centers OS - [7][8][9]18] yielding hydrogen atoms (eqn 2).…”

“…Accordingly, based on the present results and the mechanisms reported elsewhere [7][8][9]18] we propose the following mechanism. The initial step is dissociation of molecular hydrogen on the surface-active hole centers OS - [7][8][9]18] yielding hydrogen atoms (eqn 2). The highly energetic hydrogen atoms subsequently interact with surface irregularities, such as low-coordinated surface oxygen atoms O 2-(LC)s [18] to generate free electrons (eqn 3).…”

“…However, in our study of the PhICL phenomenon occurring on the photoactivated surfaces of ZrO2 and -Al2O3 we observed that the PhICL spectra were very similar to the emission spectra of the photoand/or thermoluminescence of the metal oxides [7,8]. This inferred that the physical pathway of relaxation occurred in solids, and that the primary chemical process of dissociative adsorption of H-bearing molecules led to the additional excitation of the solids.…”

“…The Photo-Induced Chemisorption Luminescence (PhICL [4][5][6][7][8][9]) is a remarkable and attractive phenomenon to observe in such interconnection between chemical and physical relaxation pathways in a single process when chemical relaxation through interaction of electron-donor molecules (H2, CH4, H2O, NH3) with photoactivated surface active sites triggers the physical relaxation process of * Corresponding author email: nick.serpone@unipv.it Tel/Fax: (+1) 514-489-9551 luminescence observed as a flash of light (the PhICL phenomenon). This phenomenon was originally observed by Andreev and Kotel'nikov on the photoactivated surfaces of Al2O3, BeO and MgO [4,5] as a result of dissociative adsorption of either water or dihydrogen.…”

In situ picosecond transient diffuse reflectance spectroscopy of opaque TiO2 systems under microwave irradiation and influence of oxygen vacancies on the UV-driven/microwave-assisted TiO2 photocatalysis

“…Thus additional electron color centers can form upon trapping the electrons either by oxygen vacancies or by Ti 4+ species. 42 O À + H 2 -OH À + H…”