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Herein we demonstrate the influence of aliovalent (Ca2+) substitution in the single-phase orthorhombic La 1-x Ca x FeO 3 (with x = 0.01, 0.03, 0.05, 0.07, 0.09) nanoparticles prepared by simple combustion method. The samples were systematically studied using XRD, SEM-EDS, and UV–Vis-DRS characterization techniques for their structural, microstructural-elemental, and optical (band structure) characteristics. Also, the catalytic attributes were evaluated through photocatalytic studies against indigo carmine in the presence of visible light. It was observed that La 1-x Ca x FeO 3 nanoparticles crystallized in orthorhombic structure at its as-synthesized form. The SEM analysis showed that the spherical nanoparticles with high porosity and agglomerations were further reduced with increasing Ca2+ concentration. The inclusion of Ca2+ also demonstrated the change in the band structure, as the band gap of the material reduced from 2.24 eV to 1.75 eV while the Ca2+ content increased from 1 mol% to 9 mol%. Furthermore, elevating the Ca2+ levels in the La 1-x Ca x FeO 3 resulted in enhanced photocatalytic decomposition of the indigo carmine dye, exhibiting a maximum efficacy of 96.5 % at neutral pH and a stabilization period of 120 min under visible light. The increase in photocatalysis is attributed to the formation of Fe4+ ions and oxygen vacancies induced by the aliovalent cation (Ca2+) replacement at the La3+ site in the LaFeO 3 host matrix. The results suggest that the prepared LaFeO 3 nanoparticles are potential nano-catalysts for photocatalytic activities against indigo carmine under visible light. [ABSTRACT FROM AUTHOR]

Significant optical nonlinearities in amorphous nanocomposites are essential for developing advanced communications and photonic devices. In this regard, the borate glasses are considered substantial and readily available commercial hosts. The present work demonstrates the white light emission and decay properties in lithium bismuth boro-phosphate glasses reinforced with gold nanoparticles (AuNPs) prepared via melting and quenching technique. Also, their non-linear optical properties are evaluated in the present study. Numerous characterization methods were used to extensively examine the produced glasses, including XRD, HR-TEM, FTIR, XPS, MAS-NMR, DSC, UV–Visible, Photoluminescence, and Z-scan techniques. Following the addition of AuNPs into the glass matrix, an increase in the refractive index and density of the glasses was observed. The amorphous features of the glass sample are disclosed by XRD examination, and DSC research demonstrates the thermal stability of the glasses after the addition of AuNPs, as shown by the rise in T g values from 459 °C to 486 °C. HR-TEM results reveal the presence of Au metal nanoparticles having a cubic crystal structure with an average size of 14 nm, while XPS analysis shows that the valence of Au is 0, i.e. Au0 or, in other words, the metallic nature of gold in glasses. FTIR, MAS-NMR, and UV–Visible spectral studies demonstrate the substantial modifications in the physical, structural, and optical properties brought about by incorporating AuNPs into the glass matrix. The PL spectra of glasses containing AuNPs show three distinct, sharp emissions at 494, 611, and 738 nm, out of which the blue emission (494 nm) is found to be predominant and has an overall emission in the region of yellow on the CIE diagram with an average lifetime of 12.23 μs. Glasses containing AuNPs have a white light correlated colour temperature (CCT) of 5129 K and CIE chromaticity (x, y) coordinates of (0.346, 0.413). Additionally, we utilized a Z-scan technique to measure the nonlinear absorption coefficient and nonlinear refractive index. Our experimental data show that the values obtained are consistent with the theoretical closed and open aperture values. Based on our findings, it appears that the glasses we prepared have the potential to be utilized in optical switching applications. [ABSTRACT FROM AUTHOR]

The kinetics of catalytic reduction of U(VI) by H 2 over Pt/SiO 2 was investigated as a function of various parameters. The effect of agitation speed and particle size on the reduction of U(VI) was studied initially to eliminate the mass transfer resistance. Later, the effect of catalyst loading, concentration of U(VI), HNO 3 , N 2 H 4 , H 2 pressure and temperature on the reduction of U(VI) was studied. Langmuir–Hinshelwood– Hougen–Watson (LHHW) approach was employed to derive kinetic model equations and understand the reaction mechanism. Among the various models, the model – IX corresponding to the adsorption of nitric acid on the catalyst surface was found to be suitable for explaining the concentration profiles of U(VI) and HNO 3 in all the temperature and pressure range. The activation energy of the reaction was determined to be around 22.6 kJ mol−1 indicating the reduction of U(VI) with H 2 was falling in chemical and diffusion controlled regime. [Display omitted] • Synthesis and characterization of Pt/SiO 2 catalyst for the reduction of U(VI) by H 2. • Effect of various parameters on the kinetics of U(VI) reduction. • Modelling the kinetics of U(VI) reduction by LHHW approach and validation. • Mechanism of U(VI) reduction. [ABSTRACT FROM AUTHOR]

In this study, the distribution of dissolved inorganic nitrate (DIN), phosphorus (DIP), and silicate (DSi) in surface waters of 70 coastal rivers in India's Western Ghats (WG) has been determined. The nutrient concentrations in individual rivers appear to be influenced by catchment geology, land use, and climate. The entire WG region contributes 0.31 Tg of DIN, 0.03 Tg of DIP, and 5.65 Tg of DSi annually to the coastal Arabian Sea. The annual ratios of N:P, Si:N, and Si:P suggest that most of these rivers are limited by P rather than N, and there is an excess supply of Si, primarily from natural sources. P limitation is severe during monsoon periods, while N limitation is observed in the Deccan Traps region. The annual export of 0.31 Tg of DIN from WG rivers could support 2.05 Tg of carbon (new production) on the Arabian Sea coast, indicating that the riverine export of DIN can significantly remove atmospheric CO 2 through biological pumps in the Arabian Sea. The study also confirms that the excess input of Si from natural processes relative to the anthropogenic supply of limited P and N further supports the idea that riverine nutrient inputs from small west-flowing tropical mountainous rivers do not contribute to coastal eutrophication along the Eastern Arabian Sea coast. • Soil acts as a major source for DIN and DIP; intense chemical weathering favors high silicate loads. • These nutrient fluxes represent a significant land-based supplier of nutrients to the coastal region of the eastern Arabian Sea. • The west-flowing coastal rivers of India carry 0.31 Tg of DIN and have a potential of 2.05 Tg of carbon (primary) production. [ABSTRACT FROM AUTHOR]