UV-sensitized nanomaterial semiconductor catalytic reduction of CoIII(N-N)33+/nm-TiO2 and Co:TiO2 formation: SEM-EDX and HRTEM analyses

Interfacial electron transfer induced by 254 nm light at nanomaterial (nm) titanium dioxide/Co-III(N-N)(3)(3+) interface in binary mixed solvent media such as water/methanol (or 1,4-dioxane) has been probed. The distinct photo reduction of cobalt(III) complexes, Co-III(N-N)(3)(3+); (N-N)=(NH3)(2), en (1,2-diamino ethane), pn (1,2-diamino propane), tn (1,3-diamino propane), and bn (1,4-diamino butane), by excited nm-TiO2 particles: Co-III + nm-TiO2 + h nu -> TiO2 (h(+);e(-)) + Co-III -> nm-TiO2 (h) + Co-II is solvent controlled. The electron transfer from the conduction band of TiO2 (e(-), CB) onto the metal centre of the complex consists of (i) electron transport from CB into surface-adsorbed species A: Co-III(N-N)(3)(3+) (ii) solution phase species B: Co-III(N-N)(3)(3+) (sol.), accumulated at the surface of the nanoparticle. In addition, UV irradiation of Co-III(N-N)(3)(3+) stimulates generation of Co-aq(II) ion, due to charge transfer transition, in solution phase. After UV irradiation, cobalt-implanted nm-TiO2 separated as gray ultrafine particles, which were isolated. Photo efficiency of the formation of Co-II ion was estimated and the cobalt implanted nanomaterial crystals isolated from the photolyte solutions were subjected to SEM-EDX, X-ray mapping, and HRTEM-SAED analyses. Solvent medium was found to contribute in both the formation of Co-II ion and interstitial insertion of cobalt into the lattice of nm-TiO2.