Bhupendra Joshi

The present work is focused on the removal of NOx with reduced blue TiO₂ with Fe (blue Fe-TiO₂)- and Cu (blue Cu-TiO₂)-doped photocatalyst. TiO₂ was reduced via lithium in EDA (blue TiO₂). Fe and Cu ions were doped in the reduced TiO₂ (blue Fe-TiO₂ and blue Cu-TiO₂). The material resulted in a core-shell structure of amorphous and anatase phase. XPS suggests the existence of Ti³⁺ species and oxygen vacancies within the structure of TiO₂. Additionally, valence bond (VB)-XPS shows the generation of intermediate levels at the band edge of the doped photocatalyst. Photocurrent, electrochemical impedance spectroscopy and cyclic voltammetry confirmed the enhanced charge-separation process in doped reduced TiO₂. The photocatalysts were tested for the photo-oxidation of NOx. Blue Fe-TiO₂ reveals the efficiency of 70% for NO elimination and 44.74% for NO₂ formation. The improved efficiency of the doped photocatalyst is related to the re-engineered structure with Ti³⁺ species, oxygen vacancies, and charge traps. Electron spin resonance (ESR) measurement was carried out for blue Fe-TiO₂ to confirm the formation of reactive oxygen species (ROS). Furthermore, ion chromatography was used to investigate the mechanism of NOx oxidation. In conclusion, the doped blue TiO₂ has a strong tendency to photo-oxidize NOx gasses.

The transparent polycrystalline ceramics have acquired an interest in different fields such as transparent armor windows, cutting tools, IR windows, wear and scratch resistant parts (watches, bearings, and displays), and synthetic opals and rubies.

Intense near-infrared to visible and near-infrared upconversion emissions are realized in Er³⁺/Ho³⁺/Tm³⁺ doped α-sialon ceramics.

Ag–BaMoO4 co-doped with Er3+/Yb3+ microcrystals were synthesized by the microwave hydrothermal process. The crystal structures and particle morphology were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. XRD patterns indicate the tetragonal scheelite structure of BaMoO4. Elemental composition was analyzed by X-ray photoelectron spectroscopy (XPS). UV-Vis diffuse reflectance spectra, Raman spectra and photoluminescence spectra were analyzed by UV-Vis diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence spectroscopy, respectively. Two strong green emission peaks (526 nm and 554 nm) and a weak red emission peak (661 nm) were identified, which were associated to the 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of the Er3+ ions, respectively. Moreover, two photonic processes were observed. The surface plasmon resonance (SPR) with upconversion luminescence behavior of the Ag–BaMoO4: Er3+/Yb3+ samples were clearly described.

Bismuth vanadate (BiVO4) powder with a hierarchical structure was successfully synthesized by the microwave-assisted hydrothermal method in the presence of EDTA of different concentration. EDTA has a crucial role in triggering the morphology of the sample together with enhancing the photocatalytic activity. Morphology, phase, crystalline structure, and optical properties of the synthesized samples were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance spectroscopy (UV-vis DRS), respectively. Different morphological variations of BiVO4 were obtained with different contents of EDTA. The obtained BiVO4 samples showed well crystalline monoclinic structure. The photocatalytic efficiency of the prepared samples were evaluated by the degradation of methylene blue (MB) under simulated solar light irradiation. The photocatalytic activity of BiVO4, synthesized by using 0.5 g of EDTA, was found to be enhanced.

Intense visible and near‐infrared frequency upconversion and a frequency downconversion photoluminescence have been reported for the first time in Tm ³⁺ and Er ³⁺ co‐doped transparent α‐Sialon ceramics under 980 nm excitation. The α‐Sialon ceramics were prepared by hot‐press sintering technique. Intense upconversion bands at 554, 678, 803 nm, and a downconversion band at 1530 nm were observed as a result of the efficient energy transfer between Er ³⁺ and Tm ³⁺ ions. The quadratic dependence of upconversion intensities on the excitation power indicates that the upconversion process is governed by two‐photon absorption process. The sintered samples of thickness 0.20 mm have transparency above 80% in the range of 2000 to 4200 nm and it reaches as high as 82% at 3350 nm. Moderately low phonon energy was found with the highest frequency band at 828 cm ⁻¹ . These novel properties manifest the potential applications of transparent α‐Sialon ceramics as a multifunctional material.