Zinc oxide nanoflakes supported copper oxide nanosheets as a bifunctional electrocatalyst for OER and HER in an alkaline medium.

Bifunctional electrocatalysts are the attractive research in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in the overall water-splitting reactions. The design and development of the cost-effective OER/HER bifunctional electrocatalysts with superior catalytic activity are still remaining as the big challenges. Herein, we have developed the CuO-ZnO nanocomposite as a bifunctional OER/HER electrocatalyst via simple chemical precipitation method. The nanocomposite was investigated for its crystalline structure, surface morphology and the functions of elements using XRD, FT-IR, SEM, TEM and XPS characterization techniques, respectively. The nanocomposite exhibited the excellent activity for the overall water-splitting in an alkaline medium. The CuO-ZnO nanocomposite showed the less onset potential of 1.4 and 0.15 V versus RHE in 1M KOH (Tafel slopes value of 0.180 and 0.400 V dec-1) for OER and HER, respectively. Hence, the as-prepared bifunctional electrocatalyst displayed the high stability for 10 h in the water electrolysis processes.

Enhanced visible light-driven photocatalytic performance of CdSe nanorods.

Cadmium selenide (CdSe) semiconductor nanorods are prepared in hydrothermal process using hydrazine hydrate (N2H4.H2O) and ammonia (NH3.H2O) as reducing agents. The reaction time is increased to 7 h and the amount of hydrazine hydrate used is also increased to 15 mL which have resulted in diminished stacking faults in the CdSe nanorods prepared. The crystal structure, morphological variations, and size of the prepared CdSe nanorods are examined by XRD analysis. The crystalline size of the CdSe nanorods is 20-30 nm in diameter. HRTEM images reveal the formation of high order CdSe nanorods of the length about 25-40 nm. The bandgap in the CdSe nanoparticles is determined to be 2.17 eV. The peak at 595 nm in photoluminescence (PL) spectrum indicates oxygen vacancy defects in the prepared CdSe sample. The variation of dielectric properties with respect to temperature and frequency of pelletized CdSe is studied. High photocatalytic efficiency (98%) of catalyst/H2O2 is also achieved for decomposition of Rhodamine-B dye.

Silver decorated CeO2 nanoparticles for rapid photocatalytic degradation of textile rose bengal dye.

High quality silver (Ag) decorated CeO2 nanoparticles were prepared by a facile one-step chemical method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), fourier transform infrared spectrometer (FT-IR), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), UV-Visible absorption (UV-Vis), photoluminescence (PL) and thermogravimetric analysis. The decoration of Ag on CeO2 surface was confirmed by XRD, EPR and HR-TEM analysis. Harmful textile pollutant Rose Bengal dye was degraded under sunlight using the novel Ag decorated CeO2 catalyst. It was found that great enhancement of the degradation efficiency for Ag/CeO2 compared to pure CeO2, it can be ascribed mainly due to decrease in its band gap and charge carrier recombination rate. The Ag/CeO2 sample exhibited an efficient photocatalytic characteristic for degrading RB under visible light irradiation with a high degradation rate of 96% after 3 h. With the help of various characterizations, a possible degradation mechanism has been proposed which shows the effect of generation of oxygen vacancies owing to the decoration of Ag on the CeO2 surface.

Optical and structural characterization of CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles.

Core-shell CdS/ZnS (Zn 0.025-0.125 M) and CdS:Cu(2+) (1%)/ZnS nanoparticles were successfully synthesized using a chemical method. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR TEM), photoluminescence (PL) and UV/Visible (UV/Vis) techniques were used to characterize the novel CdS/ZnS and CdS:Cu(2+) /ZnS core-shell nanoparticles. All absorption peaks of the synthesized samples were highly blue-shifted from the bulk CdS and ZnS. Very narrow and symmetric PL emission was observed in the yellow region for core-shell CdS/ZnS. Furthermore, the PL emission of CdS/ZnS was tuned into orange region by incorporate the Cu ion into the core CdS lattice.

Synthesis, effect of capping agents and optical properties of manganese-doped zinc sulphide nanoparticles.

Mn(2+)-doped ZnS nanoparticles have been successfully synthesized by a chemical precipitation method, using non-ionic surfactants such as PMMA and PEG. The particles were prepared in an air atmosphere at 80 °C. X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible and photoluminescence (PL) studies were used to investigate the effect of the capping agent on the size, morphology and optical properties of the ZnS-Mn(2+) nanoparticles. Enhanced PL was observed from the surfactant-capped ZnS-Mn(2+) nanoparticles. The PL spectra showed a broad blue emission band in the range 460-445 nm and a Mn(2+)-related yellow-orange emission band in the range 581-583 nm.

Luminescence study of monodispersed ZnS nanoparticles.

Monodispersed ZnS nanoparticles have been successfully synthesized by a chemical precipitation method in an air atmosphere using polyvinylpyrrolidone (PVP) and sodium hexametaphosphate (SHMP) as surfactants. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR), UV-Vis optical absorption and photoluminescence (PL) spectra. Prepared surfactants capped ZnS nanoparticles are highly homogeneous and well dispersed. Optical absorption spectra showed a strong blue shift from the uncapped particles due to the quantum confinement effect. The capped ZnS emission intensity is enhanced than more the uncapped particles. The size of the synthesized particles is around 4-6.5 nm range.

Synthesis and study of optical properties of transition metals doped ZnS nanoparticles.

ZnS and transition metal (Mn, Co, Ni, Cu, Ag and Cd) doped ZnS were synthesized using chemical precipitation method in an air atmosphere. The structural and optical properties were studied using various techniques. The X-ray diffraction (XRD) analysis show that the particles are in cubic structure. The mean size of the nanoparticles calculated through Scherrer equation is in the range of 4-6.1 nm. Elemental dispersive (EDX) analysis of doped samples reveals the presence of doping ions. The scanning electron microscopic (SEM) and transmission electron microscopic (TEM) studies show that the synthesized particles are in spherical shape. Optical characterization of both undoped and doped samples was carried out by ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The absorption spectra of all the samples are blue shifted from the bulk ZnS. An optimum doping level of the transition metals for enhanced PL properties are found through optical study.

Structural and optical study of mixed structure of ZnO(hexagonal)/ZnS(cubic) nanocomposites.

ZnO, ZnS and ZnO/ZnS nanocomposites were successfully synthesized by chemical method in an air atmosphere. Water-ethanol matrix was used as solvent. The as-obtained samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible (UV-vis) and photoluminescence (PL) spectrophotometer. The results showed that the ZnS nanoparticles are cubic in structure with the size of about 5 nm growed on the surface of the hexagonal ZnO nanocomposites. The optical study of ZnO/ZnS nanocomposites showed an enhanced PL emission in visible region. The photoluminescence property of the ZnO/ZnS core/shell nanocomposites is varied with respect to the shell thicknesses. PL quenching is observed by increasing of shell thickness on ZnO.

Luminescence properties of multilayer coated single structure ZnS/CdS/ZnS nanocomposites.

Water soluble ZnS, CdS and multilayer coated ZnS/CdS/ZnS nanocomposites were successfully synthesized by chemical method in an air atmosphere. Structural, morphology and optical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible absorption (UV-vis) and photoluminescence (PL) spectrometer. The obtained particles are highly crystalline and monodisperse with an average particle size of 4.3-5.6nm range. A significant red shift was observed by increasing the CdS thickness in ZnS/CdS/ZnS nanocomposites. The PL position of ZnS and CdS compound is tuned in the visible region by the way of alteration layer thickness.

Synthesis and optical characterization of single phased ZnS:Mn²âº/CdS core-shell nanoparticles.

Uncoated ZnS, ZnS:Mn(2+), CdS and different thickness of CdS coated ZnS:Mn(2+) core-shell nanoparticles were successfully synthesized by a simple chemical method in an air atmosphere. X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were used to characterize the uncoated and the novel ZnS:Mn(2+)/CdS core-shell nanoparticles. The results show that the size of the ZnS:Mn(2+)/CdS core-shell nanoparticles is less than the bare ZnS:Mn(2+). The PL study of ZnS:Mn(2+)/CdS core-shell nanoparticles shows an enhanced intensity than ZnS:Mn(2+). The coating of CdS layer over ZnS:Mn(2+) tuned the PL emission in the visible region. Addition of cadmium acetate (Cd 4 and 5M) in ZnS:Mn(2+) shows a distinct PL peak centered at 542 nm. The presence of Mn(2+) ions in ZnS lattice and the growth of the CdS on ZnS:Mn(2+) nanoparticles were confirmed by the ESR spectra.