Comparative photocatalytic study of visible light driven BiVO4, Cu2O, and Cu2O/BiVO4 nanocomposite for degradation of antibiotic for wastewater treatment.

Semiconductor-based photocatalysts have become increasingly used in the removal of pollutants from wastewater, especially antibiotics. A series of composite-based cuprous oxide and bismuth vanadate (Cu2O/BiVO4) composite-based photocatalysts were synthesized by using the chemical method. The structure of the Cu2O/BiVO4 composite was verified by using x-ray diffraction, scanning electron microscopy, photoluminescence, Fourier transform infrared spectroscopy, and UV-visible spectra. The degradation of methylene blue (MB) and tetracycline (TC) was investigated to check the photocatalytic activity of the Cu2O/BiVO4 composite series. The quantity of Cu2O was varied from 1% to 7% by weight to prepare the series of Cu2O/BiVO4 composites. The analysis of results verified that 5% Cu2O/BiVO4 exhibits an outstanding photocatalytic activity as compared to 1%, 3%, and 7% Cu2O/BiVO4, pure Cu2O, and pure BiVO4 under visible light irradiation. The optimum value of photocatalytic degradation achieved with 5% Cu2O/BiVO4 was 97% for MB dye and 95% for TC in 120 min, which is greater than the photocatalytic degradation of pure BiVO4 (MB 45% and TC 72%), pure Cu2O (MB 57% and TC 80%), 1% Cu2O/BiVO4 (MB 72% and TC 85%), 3% Cu2O/BiVO4 (MB 83% and TC 88%), and 7% Cu2O/BiVO4 (MB 87% and TC 91%). The stability and reusability of Cu2O/BiVO4 were also investigated. To check the major role of trapping in degradation, a trapping experiment was also performed by using three trapping agents: BQ, EDTA, and tBuOH. The results showed that Cu2O/BiVO4 exhibits an improved photocatalytic activity in the degradation of antibiotics in polluted water because the recombination rate of the electron-hole pair decreased and the surface area increased, which increased the active sites for redox reactions. Such a photocatalytic composite with high efficiency has various applications, such as energy production, environmental remediation, and water remediation.

Early stage nanocrystallization as a method of enhancement of electrical properties of lead/barium titanate doped vanadium borate glasses.

Glass-ceramic nanocomposites (GCNs) of (10 - x) BaTiO3 (BT)-xPbTiO3 (PT)-60V2O5-30B2O3 with x = 0, 2.5, 5, 7.5 and 10 mol% were formed during heat treatment of conventional melt quenching glasses. X-ray diffraction was used to ensure glass and GCNs formation. Glasses and GCNs densities were measured by Archimedes principle. Fine polar clusters of lead titanate and/or barium titanate incorporation into vanadium borate glass matrix strongly depend on the composition. It was found out that the electrical conductivity of the initial glasses can be considerably improved by proper early stage of nanocrystallization at temperatures approaching the crystallization temperatures determined by DSC method. GCNs show massive increase in electrical conductivity (up to 6 orders of magnitude) as a function of BaTiO3 content. By increasing BaTiO3 content, the activation energy values have been found to increase. The enhancement in electrical conductivity of GCNs can be attributed to the increase in the crystalline phases in the glassy matrix which increases the concentrations of the V ion pairs.

Intrinsic and strain dependent ultralow thermal conductivity in novel AuX (X = Cu, Ag) monolayers for outstanding thermoelectric applications.

A large power factor and ultralow lattice thermal conductivity in 2D-monolayers of AuX (X = Cu and Ag) are achieved via first principles calculations. Low phonon frequency, small Debye temperature and high Gruneisen parameter limit the intrinsic thermal conductivity of both the studied materials. An ultra-low lattice thermal conductivity of 0.13 (0.30) W m-1 K-1 and 0.66 (1.59) W m-1 K-1 is obtained for unstrained AuCu and AuAg monolayers, respectively, at 700 (300) K, which further reduces to 0.04 (0.09) and 0.26 (0.63) W m-1 K-1 at 6% biaxial tensile strain. Such values of thermal conductivity are lower than the critical thermal conductivity for the state-of-art thermoelectric materials (kl < 2 W m-1 K-1). The peak values of ZT for unstrained monolayers are 2.20 and 1.40, which enhances to 3.61 and 2.91 at 6% strain for AuCu and AuAg monolayers, respectively. Interestingly pudding-mold band textures are found to be responsible for this unusual thermoelectric behaviour. The stability concerns (chemical/dynamic/mechanical) of these monolayers are ensured to stimulate experimental determinations for novel synthesis and possible applications.

Photoluminescence Emission Studies on a Lanthanum-Doped Lead Free Double Halide Perovskite, La:Cs2SnCl6.

Recent advances in bandgap engineering have increased the possibility of vacancy ordered double halide perovskites (VO-DHPs), Cs2SnX6 where X = Cl, Br, I with designable optoelectronic features. Doping with La3+ ions modulates the band gap from 3.8 to 2.7 eV, allowing a steady room temperature dual emission (PL) centered at 440 and 705 nm in Cs2SnCl6. Pristine Cs2SnCl6 and La:Cs2SnCl6 both have a crystalline cubic structure with a space symmetry of Fm3m. The cubic phase correlates well with the Rietveld refinement. SEM analysis confirms anisotropic development with huge micrometer-sized (>10 µm) truncated octahedral structures. DFT investigations show that the insertion of La3+ ions into the crystal lattice leads to the band splitting. The present study elaborates the experimental understanding of the dual PL emission properties of La:Cs2SnCl6 leaving a scope for detailed theoretical study on the origin of the complex electronic transitions involving f-orbital electrons.

Synthesis of mesoporous Ag/α-Fe2O3/TiO2 heterostructures with enhanced and accelerated photo/-catalytic reduction of 4-nitrophenol.

4-Nitrophenol (4-NP) is reported to originate disadvantageous effects on the human body collected from industrial pollutants; therefore, the detoxification of 4-NP in aqueous contamination is strongly recommended. In this study, the heterojunction mesoporous α-Fe2O3/TiO2 modulated with diverse Ag percentages has been constructed via a sol-gel route in the occurrence of a soft template P123. The formation of biphasic crystalline TiO2 anatase and brookite phases has been successfully achieved with the average 10 nm particle sizes. The photo/-catalytic reduction of 4-NP has been performed utilizing NaBH4 as a reducing agent with and without visible illumination. All Ag/Fe2O3/TiO2 nanocomposites exhibited significantly higher photo/-catalytic reduction efficiency than pure Fe2O3, TiO2 NPs, and Fe2O3/TiO2 nanocomposite. 2.5% Ag/Fe2O3/TiO2 nanocomposite was considered the highest and superior photocatalytic reduction efficiency, and it almost achieved 98% after 9 min. Interestingly, the photocatalytic reduction of 4-NP was accelerated 9 times higher than the catalytic reduction over 2.5% Ag/Fe2O3/TiO2; its rate constant value was 709 and 706 times larger than pure TiO2 and Fe2O3 NPs, respectively. The enhanced photocatalytic reduction ability of Ag/Fe2O3/TiO2 nanocomposite might be referred to as significantly providing visible light absorption and a large surface area, and it can upgrade the effective separation and mobility of electron holes. The stability of the synthesized catalysts exhibited that the obtained catalysts can undergo a slight decrease in reduction efficiency after five successive cycles. This approach highlights a novel route for constructing ternary nanocomposite systems with high photo/-catalytic ability.

Electronic Structure-, Phonon Spectrum-, and Effective Mass- Related Thermoelectric Properties of PdXSn (X = Zr, Hf) Half Heuslers.

We hereby discuss the thermoelectric properties of PdXSn(X = Zr, Hf) half Heuslers in relation to lattice thermal conductivity probed under effective mass (hole/electrons) calculations and deformation potential theory. In addition, we report the structural, electronic, mechanical, and lattice dynamics of these materials as well. Both alloys are indirect band gap semiconductors with a gap of 0.91 eV and 0.82 eV for PdZrSn and PdHfSn, respectively. Both half Heusler materials are mechanically and dynamically stable. The effective mass of electrons/holes is (0.13/1.23) for Zr-type and (0.12/1.12) for Hf-kind alloys, which is inversely proportional to the relaxation time and directly decides the electrical/thermal conductivity of these materials. At 300K, the magnitude of lattice thermal conductivity observed for PdZrSn is 15.16 W/mK and 9.53 W/mK for PdHfSn. The highest observed ZT value for PdZrSn and PdHfSn is 0.32 and 0.4, respectively.

Effect of Strain on the Electronic Structure and Phonon Stability of SrBaSn Half Heusler Alloy.

This paper presents the strain effects on the structural, electronic and phonon properties of a newly proposed SrBaSn half Heusler compound. Since it is stable considering chemical thermodynamics, we tested its strength against uniform strain w.r.t phonon spectrum and it produces a direct bandgap of 0.7 eV. The direct bandgap reduces to 0.19 eV at -12% strain beyond which the structure is unstable. However, an indirect gap of 0.63 eV to 0.39 eV is observed in the range of +5% to +8% strain and afterwards the strain application destabilizes the structure. From elastic parameters, the ductile nature of this material is observed.

Investigation of BaO reinforced TiO2-p2O5-li2O glasses for optical and neutron shielding applications.

The optical and radiation shielding characteristics of 15TiO2-70P2O5 - (15 - x) Li2O-x BaO x = (0 ≤ x ≤ 10 mol%) glasses were reported in this study. The glass status of the investigated samples was established by XRD. Although the molar volume decreases within 39.8-31.2 cm3 mol-1, the density was increased from 2.908 to 4.11 g cm-3 with the addition of BaO. UV-Vis-NIR spectroscopy was utilized for the examination of the optical characteristics of all compositions. E indir opt. and E dir opt. both increased from 2.7 to 3.07 eV and 2.79 to 3.31 eV, while E u decreased from 0.368 to 0.295 eV. Furthermore, the Phy-X/PSD code was used to evaluate the gamma-ray shielding parameter. Within the energy range of 15 keV to 15 MeV, the equivalent atomic number, as well as the EBF and EABF parameters, was evaluated. Overall, excellent material properties were detected for a glass with a high BaO content, which could be useful for future optical, shielding, and fast neutron shielding properties.