An experimental and theoretical evaluation of surface states in MgO and other alkaline earth oxides

Photoluminescence quenching in compressed MgO nanoparticle systems

“…[13][14][15] MgO nanocube ensembles have been the subject of numerous previous investigations and are perhaps some of the best understood ceramic nanomaterials. [16][17][18][19] In previous work, a variety of spectroscopic techniques [20][21][22][23][24][25] as well as first-principles theoretical calculations [26][27][28][29] have been used to investigate the electronic properties of MgO nanocubes formed by the controlled combustion of magnesium vapor. UV diffuse reflectance spectroscopy reveals two absorption bands far below the bulk absorption threshold of MgO (7.8 eV) which have been attributed to corner (4.6 eV) and edge sites (5.2 eV).…”

The surface sites of sulfated zirconia studied in situ by laser-induced fluorescence spectroscopy

“…This band is attributed to the coordinatively unsaturated surface sites, (Zr 4+ -O 2À ) Low Coordination , of the zirconia [21]. Similar luminescence behavior and assignment were also reported on MgO and SrO [21,22]. After simulating these spectra based on Gaussian curve for a fluorescence band [23], as shown in Table 1, the emission band at ca.…”

Photophysical Processes Related to Photoadsorption and Photocatalysis on Wide Band Gap Solids: A Review

“…Therefore the dispersed wide band gap solids may be rated as a potential competitors for relatively narrow band gap solids. As the example, the absorption band assigned to exciton-like excitation of 3-coordinated oxygen corner sites in MgO peaks at 4.6 eV, [5,6,10] while the bulk exciton band maximum is located at 7.7 eV. Similar, the STE in the subsurface (0001) layer in α quartz (E g = 11 eV) has dropped in energy by 0.7 eV in respect to the energy of bulk exciton (3.7 eV), the further energy drop by 0.5 eV occurs due to reaction of STE with OH − group at the surface with formation of OH radicals [22].…”

“…It is commonly accepted to tell the difference between the so called photoelectric active and photoelectric inactive light absorption depending on whether or not the free charge carriers appear in solids under illumination (see, for example [3]). On the other hand the absorption of light quanta can be related with regular crystal sites (fundamental or intrinsic absorption) and with crystal imperfections, i.e., with intrinsic and extrinsic lattice defects (see, for example [4][5][6]). Among the intrinsic defects are vacancies, interstitials and their aggregations (point or zerodimensional defects).…”

“…i.e., vacancies occupied by two electrons, electrons captured by divacancies and so on [8,9]. The specific absorption originates from the surface states of solid particles [5,10]. The surface states correspond to the regular surface sites, crystallite edges, kinks, corner ions and atoms, and with intrinsic surface defects such as vacancies and single ions and atoms.…”