School Of Basic And Applied Sciences

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    One pot synthesis of Au embedded ZnO nanorods composite heterostructures with excellent photocatalytic properties
    (Central University of Punjab, 2018) Biswas, Rathindranath; Haldar, Krishna Kanta
    Here, we have designed a noble composite nanostructure by embedding Au nanoparticles into ZnO nanorods surface in one pot synthesis as a photocatalyst. The formation the composite nanostructure was confirmed by X-ray diffraction, Xray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) investigations. Microscopic studies suggest that spherical Au nanoparticles are nucleated on the ZnO nanorods surface. XPS shows shifting of peak positions towards higher binding energy indicating charge transfer from ZnO to Au in the composite nanostructures. This is unambiguously confirmed by the steady state spectroscopic studies. It is found that 95.7% of Methylene blue (MB) dye is degraded by the composite nanostructure after 140 min under UV light illumination, and the apparent rate constant is found to be 0.013 min-1 . This new class of Au nanoparticles embedded ZnO nanorods composite nanostructure opens up new possibilities in photocatalytic, solar energy conversion, photovoltaic, and other new emerging applications.
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    Promising field electron emission performance of vertically aligned one dimensional (1D) brookite (?) TiO2 nanorods
    (Royal Society of Chemistry, 2016) Devan, R.S.; Ma, Y.-R.; More, M.A.; Khare, R.T.; Antad, V.V.; Patil, R.A.; Thakare, V.P.; Dhayal, R.S.; Schmidt-Mende, L.
    We evidence field-electron emission (FE) studies on the large-area array of one-dimensional (1D) brookite (?) TiO2 nanorods. The pure 1D ?-TiO2 nanorods of 10 nm width and 760 nm long were synthesized on Si substrate utilizing hot-filament metal vapor deposition technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis evidenced the ?-TiO2 nanorods to be composed of orthorhombic crystals in brookite (?) phase. X-ray photoemission spectroscopy (XPS) revealed the formation of pure stoichiometric (i.e. 1 : 1.98) 1D TiO2 nanorods. The values of turn-on field, required to draw current density of 10 ?A cm-2, was observed 3.9 V ?m-1 for pristine 1D ?-TiO2 nanorods emitters, which were found significantly lower than doped/undoped 1D TiO2 nanostructures (i.e. nanotubes, nanowires, nanorods) based field emitters. The enhanced FE behavior of the TiO2/Si emitter can be attributed to modulation of electronic properties due to the high aspect ratio of vertically aligned TiO2 nanorods. Furthermore, the orthodox emission situation of pristine TiO2/Si emitters exhibit good emission stability and reveal their potentials as promising FE material. ? 2016 The Royal Society of Chemistry.
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    Nickel oxide decorated zinc oxide composite nanorods: Excellent catalyst for photoreduction of hexavalent chromium
    (Academic Press Inc., 2018) Singh, Simranjeet; Ahmed,Imtiaz; Haldar, Krishna Kanta
    In light of the growing interest and ability to search for new materials, we have synthesized Nickel oxide (NiO) nanoparticles decorated Zinc (ZnO) nanorods composite (NiO/ZnO) nanostructure. The NiO/ZnO heterostructure formation was confirmed by X-ray powder diffraction and high-resolution transmission electron microscopy (HRTEM). The fabricated environmental friendly NiO/ZnO composite nanostructure shows a well-defined photoreduction characteristic of hexavalent Chromium (Cr) (VI) to tri-valent Chromium (Cr) (III) under UV-light. Such an enhanced photoreduction property is attributed due to the decreased electron-hole recombination process which was proved by photoluminescence (PL) spectroscopy, photocurrent study, and electrochemical impedance spectroscopy. Furthermore, the photocatalytic activity rate of the NiO decorated ZnO nanorods was much higher than that of bare ZnO nanorods for the reduction of chromium (VI) and the rate is found to be 0.306 min?1. These results have demonstrates that suitable surface engineering may open up new opportunities in the development of high-performance photocatalyst. ? 2018 Elsevier Inc.
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    Size dependent tunnel diode effects in gold tipped CdSe nanodumbbells
    (American Institute of Physics Inc., 2017) Saraf, Deepashri; Kumar, Ashok; Kanhere, Dilip; Kshirsagar, Anjali
    We report simulation results for scanning tunneling spectroscopy of gold-tipped CdSe nanodumbbells of lengths ?27 ? and ?78 ?. Present results are based on Bardeen, Tersoff, and Hamann formalism that takes inputs from ab initio calculations. For the shorter nanodumbbell, the current-voltage curves reveal negative differential conductance, the characteristic of a tunnel diode. This behaviour is attributed to highly localized metal induced gap states that rapidly decay towards the center of the nanodumbbell leading to suppression in tunneling. In the longer nanodumbbell, these gap states are absent in the central region, as a consequence of which zero tunneling current is observed in that region. The overall current-voltage characteristics for this nanodumbbell are observed to be largely linear near the metal-semiconductor interface and become rectifying at the central region, the nature being similar to its parent nanorod. The cross-sectional heights of these nanodumbbells also show bias-dependence where we begin to observe giant Stark effect features in the semiconducting central region of the longer nanodumbbell. ? 2017 Author(s).