Stoichiometric and sodium-doped titanium silicate molecular sieve containing atomically defined –OTiOTiO– chains: Quantum ab initio calculations, spectroscopic properties, and reactivity

摘要: Ab initio calculations on a linear –OTiOTiO– chain embedded in an envelope of (SiO4) tetrahedra, mimicking the structure Na2TiSi5O13 molecular sieve (ETS-10), confirm that peculiar optical properties solid are associated with presence chains behaving as quantum wires. The [in UV-Vis (ultraviolet-range)] and magnetic [(ESR) electron spin resonance] these can be modified by adsorbing Na vapors. sodium atoms diffusing into channels undergo ionization process formation Na+ (localized main channels) Ti3+ (in chain, which so becomes nonstoichiometric wire) characterized Ti/Na ratios 2–4 range. Successive adsorption oxygen at room temperature leads to partial (Ti/Na∼2) or total (Ti/Na∼4) restoration stoichiometry predominant oxide. minor fraction superoxide negative ions whose revealed ESR spectroscopy is also observed. Total original samples always obtained when made 473 K. sample keeps its structural integrity during reduction successive oxidation process.