Scheelite-related MBi1-xV1-xMoxO4 (MII- Ca, Sr) solid solution-based photoanodes for enhanced photoelectrochemical water oxidation

The photoelectrochemical properties of scheelite-related MBi_1-xV_1-xMo_xO₄ (M^II = Ca, Sr, x = 0.1 to 0.9) solid solutions deposited on conductive glass (coated with SnO₂, F-doped) have been investigated as photoanodes in photoelectrochemical (PEC) water splitting. The variation of the final annealing temperature during the preparation of the conduction electrodes as well as the value of substitution x have been shown to affect the PEC performance. The micropowders of MBi_1-xV_1-xMo_xO₄ (M^II = Ca, Sr, x = 0.1 to 0.9) samples were first fabricated vi a solid-state method; they were characterised by SEM microscopy and powder and single crystal X-ray diffraction, and the band gap values were estimated using diffusive reflectance data. The value of substitution x = 0.1 in the cases of samples containing calcium and strontium affords the highest PEC performance reported for the whole range of substitution. These results demonstrate a promising approach for the beneficial utilization of BiVO₄-substituted scheelite-related solid solutions in photo-electrochemical cells towards efficient and inexpensive photoanodes.

Structural features of hydroxyapatite and carbonated apatite formed under the influence of ultrasound and microwave radiation and their effect on the bioactivity of the nanomaterials

The samples of hydroxyapatite and carbonate substituted hydroxyapatite (CHA) were obtained under the influence of physical factors, namely ultrasound (US) and microwave (MW) radiations. The results of Fourier transform infrared spectroscopy and X-ray diffraction analysis have proved the formation of the calcium deficient hydroxyapatite and B-type CHA with the Ca/P ratio in the ranges 1.62-1.87. In vitro studies have showed the increased bioactivity of the samples, synthesized under the influence of physical factors as compared to the standard ones. The samples of both groups, synthesized under the influence of 600 W MW, have shown the greatest stability in biological environment. In vivo tests confirm that obtained under US and MW radiations hydroxyapatite-based biomaterials are biocompatible, non-toxic and exhibit osteoconductive properties. The usage of US and MW radiations can significantly shorten the time (up to 5-20 min) of obtaining of calcium deficient hydroxyapatite and B-type CHA in nanopowder form, close in structure and composition to the biological hydroxyapatite.

Luminescence study of nanosized Al2O3:Tb3+ obtained by gas-dispersed synthesis

Terbium-doped Al₂O₃ samples were obtained by gas-dispersed synthesis. It was shown that the resulting powders, with particle sizes of 10-70 nm, consist of a mixture of transition aluminas, among which the δ ^*-polymorph is dominant. The luminescence properties of Al₂O₃:Tb³⁺ have been studied upon excitation in the UV-visible range of the spectrum. It was found that Tb³⁺ ions cause several groups of inhomogeneously broadened emission bands in the range of 470-640 nm, which are characteristic for disordered materials. In addition, the emission spectra contain a broad band at about 450 nm and several narrower ones in the 680-720 nm region. These features are attributed to surface defects and impurity Cr³⁺ ions occupying Al³⁺ octahedral positions, respectively.

Structural transformation of Bi1−x/3V1−xMoxO4 solid solutions for light-driven water oxidation

The influence of Mo content in the solid solutions of Bi_1−x/3V_1−xMo_xO₄ (x = 0.05–0.20) on the morphology, band gap, structure and light-driven water oxidation properties has been studied by SEM, powder XRD and vibrational spectroscopy.