UV-sensitized nanomaterial semiconductor catalytic reduction of CoIII(N–N)3 3+/nm-TiO2 and Co:TiO2 formation: SEM-EDX and HRTEM analyses

Abstract

Interfacial electron transfer induced by 254 nm light at nanomaterial (nm) titanium dioxide/CoIII(N–N)33+ 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, CoIII(N–N)33+; (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: CoIII + nm-TiO2 + hν → TiO2 (h+;e−) + CoIII → nm-TiO2 (h) + CoII 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: CoIII(N–N)33+ (ii) solution phase species B: CoIII(N–N)33+(sol.), accumulated at the surface of the nanoparticle. In addition, UV irradiation of CoIII(N–N)33+ stimulates generation of \( {\text{Co}}_{\text{aq}}^{\text{II}} \) 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 CoII 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 CoII ion and interstitial insertion of cobalt into the lattice of nm-TiO2.