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Luminescent Li3Ba2Gd3Mo8O32:Tb3+ phosphors were synthesized using the sol–gel method, and extensively characterized through various spectroscopic techniques, including x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, photoluminescence (PL) excitation, and emission. SEM micrographs revealed the irregular and non-uniform morphology and size of the prepared phosphors. The FT-IR spectra offered insights into the functional groups and bonding within the phosphor. The PL excitation spectra at a 545 nm emission wavelength displayed a slight shift in peak positions with a prominent peak at 283 nm, corresponding to the characteristic 4f8 → 4f75d1 transitions of Tb3+ ions, while under excitation at λexc = 283 nm, PL emission spectra exhibited distinct peaks associated with 5D4 → 7Fj (j = 6, 5, 4, 3) transitions. Notably, the transition 5D4 → 7F5 at 545 nm demonstrated strong and particularly high intensity in the Li3Ba2Gd3Mo8O32:0.09Tb3+ phosphor. Photometric analysis showed the potential of this phosphor to serve as a vivid green light source for various display applications. The Li3Ba2Gd3Mo8O32:Tb3+ phosphor may be used for creating sensors for environmental monitoring. Future research could explore its biocompatibility for biomedical applications and improve its targeting and photostability. [ABSTRACT FROM AUTHOR]

In this work, the synthesis of Ho3+-doped calcium titanate perovskite (CaTiO3) revealed significant photoluminescence (PL) properties, predominantly displaying a distinct green emission. The investigation explored Ho3+-doped CaTiO3 perovskite synthesized via the sol–gel method. Structural analysis confirmed an orthorhombic crystal structure through powder x-ray diffraction (XRD) and Rietveld refinement, while Fourier transform infrared (FT-IR) spectroscopy confirmed the presence of functional groups in Ho3+-doped CaTiO3. Diffuse reflectance spectroscopy (DRS) revealed a charge transfer band between O2− and Ho3+ ions in the range of 250–350 nm, supported by photoluminescence excitation (PLE) spectra. A bandgap of 3.39 eV was found for Ho3+-doped CaTiO3. At 0.03 mol Ho3+, the PLE band intensity was saturated, indicating optimal excitation efficiency. Emission spectra revealed distinct intra 4f–4f transitions, particularly a green emission at 545 nm under 454 nm excitation corresponding to 5F4 + 5S2 → 5I8 transition. The PL intensity reached its peak at 0.03 mol Ho3+ and then decreased due to concentration quenching. Color purity reached ~90%, highlighting its potential in applications requiring precise green emission. The results of the study suggest that this perovskite is well suited for optoelectronics, lighting, displays, or industries that require specific green light emission properties. [ABSTRACT FROM AUTHOR]

A series of terbium-activated yttrium oxyorthosilicate (Tb3+:Y2SiO5) phosphor was prepared through the sol–gel technique at a high calcination temperature of 1100°C. The phase purity was examined by the x-ray diffraction (XRD) analysis and found to be X1 type for all series of samples. The existence of functional groups in the prepared samples was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. The sample exhibited absorption bands of Si-O-Si and Y-O groups at wavenumbers between 717 cm−1 and 550 cm−1 , and the NO3 groups appeared between 800 cm−1 and 1020 cm−1 in the FT-IR spectra. Under 244-nm excitation, the photoluminescence spectra were recorded in the 350 to 650 nm wavelength range. A possible cross-relaxation mechanism between the 5D3 and the 5D4 levels for the concentration quenching of two distinct emission transitions has been described in detail. The dipole–dipole interaction is most responsible for concentration quenching, as evidenced by the Dexter theory. The CIE chromaticity analysis of the Y2SiO5:Tb3+ phosphor was illustrated by a CIE 1931 color calculator. These findings demonstrate the suitability of the Tb3+-activated Y2SiO5 matrix as a UV-excitable, color-tunable emitter with Tb3+ ion variations and an efficient green light-emitting phosphor in the fields of solid-state lighting devices. [ABSTRACT FROM AUTHOR]

The production of hydrogen from water with semiconductor photocatalysts can be promoted by adding small amounts of metals to their surfaces. The resulting enhancement in photocatalytic activity is commonly attributed to a fast transfer of the excited electrons generated by photon absorption from the semiconductor to the metal, a step that prevents deexcitation back to the ground electronic state. Here we provide experimental evidence that suggests an alternative pathway that does not involve electron transfer to the metal but requires it to act as a catalyst for the recombination of the hydrogen atoms made via the reduction of protons on the surface of the semiconductor instead.

We report simultaneous removal of NO and SO2 by Fe(II)EDTA2− absorbent in a wet absorption system. Effects of various operation parameters, such as Fe(II)EDTA2− concentration, solution volume, NO inlet concentration, and pH of absorption solution on NO absorption in a semi-batch reaction, were investigated. NO loading capacity increased with increasing NO inlet concentration since NO loading capacity was highly influenced by NO inlet concentration. NO loading capacity increased in neutral and alkaline environments compared to that in an acidic one. To evaluate NO absorption performance of practical flue gas components, simultaneous absorption of NO and SO2 in the presence of O2 over Fe(II)EDTA2 was carried out. As a result, when all gas emission components (NO, SO2 and O2) were introduced, simultaneous removal of NO and SO2 was obtained with a high NO loading capacity (ca. 88.8%). Antagonistic effects of both SO2 and O2 played an essential role in the regeneration of Fe(III)EDTA and Fe(II)EDTA-NO2 to Fe(II)EDTA2, keeping a neutral pH of absorption solution and resulting in a dramatic improvement in the absorption of NO and SO2. [ABSTRACT FROM AUTHOR]

The effects of operating parameters such as reaction temperature, space velocity, and feed gas composition on the performance of the methane dry-reforming reaction (DRM) over the Ni/Al2O3 catalyst are systemically investigated. The Ni/Al2O3 catalyst, which is synthesized by conventional wet impregnation, showed well-developed mesoporosity with well-dispersed Ni nanoparticles. CH4 and CO2 conversions over the Ni/Al2O3 catalyst are dramatically increased as both the reaction temperature is increased, and space velocity is decreased. The feed gas composition, especially the CO2/CH4 ratio, significantly influences the DRM performance, catalyst deactivation and the reaction behavior of side reactions. When the CO2-rich gas composition (CO2/CH4 > 1) was used, a reverse water gas shift (RWGS) reaction significantly occurred, leading to the consumption of hydrogen produced from DRM. The CH4-rich gas composition (CO2/CH4 < 1) induces severe carbon depositions followed by a reverse Boudouard reaction, resulting in catalytic activity drastically decreasing at the beginning followed by a stable conversion. The catalyst after the DRM reaction with a different feed ratio was analyzed to investigate the amount and structure of carbon deposited on the catalyst. In this study, we suggested that the optimal DRM reaction conditions can achieve stable performances in terms of conversion, hydrogen production and long-term stability. [ABSTRACT FROM AUTHOR]

Gd3+-doped CaMgSi2O6 phosphors with varying dopant content were processed successfully using sol-gel preparation. Prepared products were verified by x-ray diffraction data, which indicated the formation of a monoclinic phase. Scanning electron microscopy suggested the formation of tightly aggregated phosphor particles. A strong photoluminescence emission peak of 6P7/2 → 8S7/2 at 313 nm was observed in the studied phosphors under 273-nm excitation. The changes in emission intensity were also monitored with respect to the concentration of Gd3+. X-band electron paramagnetic resonance (EPR) spectra of the phosphors revealed the fine structure lines of Gd3+ ions typical of orthorhombic or lower symmetry. In addition, the intensity of the EPR spectrum from Gd3+ showed saturation beyond 0.03 mol of Gd3+ doping. [ABSTRACT FROM AUTHOR]