AUTHOR=Kniec Karolina , Marciniak Lukasz TITLE=Different Strategies of Stabilization of Vanadium Oxidation States in Lagao3 Nanocrystals JOURNAL=Frontiers in Chemistry VOLUME=7 YEAR=2019 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00520 DOI=10.3389/fchem.2019.00520 ISSN=2296-2646 ABSTRACT=

The spectroscopic properties of LaGaO₃, doped with V ions, were examined in terms of the possibility of the stabilization of particular vanadium oxidation states. It was shown that three different approaches may be applied in order to control the ionic charge of vanadium, namely, charge compensation, via incorporation of Mg²⁺/Ca²⁺ ions, citric acid (CA)-assisted synthesis, with various CA concentrations and grain size tuning through annealing temperature regulation. Each of utilized method enables the significant reduction of V⁵⁺ emission band at 520 nm associated with the V⁴⁺→ O²⁻ CT transition in respect to the ²E→ ²T₂ emission band of V⁴⁺ at 645 nm and ¹E₂ → ³T_1g emission band of V³⁺ at 712 nm. The most efficient V oxidation state stabilization was obtained by the use of grain size modulation, which bases on fact of different localization of the V ions of given charge in the nanoparticles. Moreover, the CA-assisted synthesis of LaGaO₃:V determines V valence states but also provides significant separation of the nanograins. It was found that superior charge compensation was achieved when Mg²⁺ ions were introduced in the matrix, due the more efficient lability, resulting from the comparable ionic radii between Mg²⁺ and V ions.