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In this work, pristine, 0.02, 0.04, and 0.06 M neodymium (Nd)-doped barium tungstate nanostructures were synthesized via a simple co-precipitation method for the water oxidation process. The obtained X-ray diffraction high-intensity peak at a 2θ value of 26.4° corresponding to the (112) lattice plane confirmed the formation of a tetragonal structure of BaWO4. Moreover, the BaWO4 morphology was examined by scanning electron microscopy, which showed the existence of nanospindles. An energy-dispersive X-ray spectrum confirmed the subsistence of the produced materials, for example, barium (Ba), tungsten (W), oxide (O), and neodymium (Nd), with weight percentages of 28.58, 46.63, 16.64, and 8.16%, respectively. The 0.04 M Nd-doped BaWO4 product was explored to attain a high surface area of 18.18 m2/g, a pore volume of 0.079 cm3/g, and a pore diameter of 2.215 nm. Compared to the other prepared electrodes, the 0.04 M Nd-doped BaWO4 product exhibited low overpotential values of 330 mV and 450 mV to deliver current densities of 10 mA/cm2 and 50 mA/cm2, respectively. In addition, the optimized electrode achieved a small Tafel slope value of 158 mV dec–1 and followed the Volmer–Heyrovsky mechanism. Moreover, the electrical conductivity of BaWO4 was tuned due to the addition of a rare-earth metal dopant, and it exhibited the charge-transfer resistance and solution resistance values of 0.98 and 1.01 Ω, respectively. The prepared electrocatalyst was further studied by using cyclic voltammetry, and it exhibited a high double-layer capacitance value of 29.3 mF/cm2 and high electrochemically active surface areas of 1.465 cm2. The electrochemical performance was greatly improved depending on the concentration of the doping agent, and it was well consistent with the obtained results. The best electrocatalyst was subjected to a chronoamperometry test, which exhibited excellent stability even after 20 h. Hence, this work suggests that alkaline metal tungstates have a cost-effective, efficient, and promising electrocatalyst, and it is a new approach for the water oxidation process.

In this context, we synthesize pristine and transition metal (Fe, Co, Ni, and Cu) (TM)-doped uniform, 3D-rhombohedral manganese carbonate (MnCO3) microcrystals using a simple hydrothermal method. T...

A novel Gd2O3 nanosheet was synthesized by the template-free chemical coprecipitation method. Interestingly, upon calcination at 600 °C, nanoparticles were transformed into a nanosheet, as observed from field emission scanning electron microscopy (FESEM) images. An increase in the calcination temperature to 600 °C increases the particle size to 50 nm, which results in aggregation. A sheetlike Gd2O3 exhibits superparamagnetism from 300 K. The highly selective nonenzymatic sensing of riboflavin (RF) was studied using a modified glassy carbon electrode with Gd2O3 nanosheets, and its various applications were made possible by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The redox behavior of the RF was determined. The newly fabricated sensor showed high sensitivity, stability, and reproducibility and was also tested with a commercial vitamin B2 tablet and a milk powder sample.

Current research is paying much attention to heterojunction nanostructures. Owing to its versatile characteristics such as stimulating morphology, affluent surface-oxygen-vacancies and chemical compositions for enhanced generation of reactive oxygen species. Herein, we report the hydrothermally synthesized TiO2@MoS2 heterojunction nanostructure for the effective production of photoinduced charge carriers to enhance the photocatalytic capability. XRD analysis illustrated the crystalline size of CTAB capped TiO2, MoS2@TiO2 and L-Cysteine capped MoS2@TiO2 as 12.6, 11.7 and 10.2 nm, respectively. The bandgap of the samples analyzed by UV–Visible spectroscopy are 3.57, 3.66 and 3.94 eV. PL spectra of anatase phase titania shows the peaks present at and above 400 nm are ascribed to the defects in the crystalline structure in the form of oxygen vacancies. HRTEM reveals the existence of hexagonal layered MoS2 formation on the spherical shaped TiO2 nanoparticles at the interface. X-ray photoelectron spectroscopy recommends the chemical interactions between MoS2 and TiO2, specifically, oxygen vacancies. In addition, the electrochemical impedance spectroscopy studies observed that L-MT sample performed low charge transfer resistance (336.7 Ω cm2) that promotes the migration of electrons and interfacial charge separation. The photocatalytic performance is evaluated by quantifying the rate of Congo red dye degradation under visible light irradiation, and the decomposition efficiency was found to be 97%. The electron trapping recombination and plausible photocatalytic mechanism are also explored, and the reported work could be an excellent complement for industrial wastewater treatment. © 2020, The Author(s). The authors (Dr. G. Ramalingam & Prof. G. Ravi) acknowledge the financial support from MHRD-SPARC (ID: 890/2019), UKIERI, DST-SERB(EEQ/2016/00198), RUSA 2.0 Grant No. F.24-51/2014-U, Policy (TN Multi-Gen) by the Government of India and UK projects. Part of this work was developed under “Smart Surfaces for Automotive Components (SMART4CAR)” Project, receiving funding from COMPETE agency, PT2020 funding program, under contract No.: POCI-01-0247-FEDER-045096. The project team members, Jordi Llobet, Helder Fonseca and Patrícia C. Sousa are also acknowledged. The author J. S. Ponraj acknowledges the funding and support from EU-EC/MSCA-COFUND-2015-FP Nano TRAIN for Growth II N°: 713640, INSPIRE Faculty Scheme (DST/INSPIRE/04/2016/000292) and SERB-EMR (EMR/2017/004764).

Micro- and nano-crystalline polymorphs of CuFeS2 have been synthesized by using simple, low temperature solvothermal and precipitation methods. A solvothermal process at 170 °C, using ethylenediamine produced micro- and nano-crystalline CuFeS2 with various shapes and morphologies, which include polygons, pyramids, hexagonal rods and plates etc. In addition to the expected tetragonal, chalcopyrite phase, a new, relatively low symmetry, hexagonal, wurtzite phase of CuFeS2 was also obtained. The wurtzite phase fraction was found to be ~21 wt% by Rietveld analysis using X-ray powder diffraction data. Further, the effects of solvent concentration, reaction temperature and annealing on the crystallites have been studied. By the solvothermal process carried out at 140 °C, hexagonal, wurtzite phase CuFeS2 was obtained with a phase fraction as high as ~92 wt%. A relatively, simple and low-temperature precipitation process using (NH4)2S and distilled water produced micro- and nano-crystalline CuFeS2 with various shapes including rods, hexagonal plates, and spheres etc. The synthesis methods reported here are believed to be beneficial for the further development of CuFeS2 in the field of nanotechnology.