Vapor-liquid-solid growth of one-dimensional tin sulfide (SnS) nanostructures with promising field emission behavior.

Single-crystalline ultralong tin sulfide (SnS) nanowires has been grown by a thermal evaporation technique under optimized conditions on gold-coated silicon substrates, and for the first time, field emission investigations on the SnS nanowires at the base pressure of 1 × 10(-8) mbar are reported. It has been revealed that the surface morphology of the as-synthesized SnS nanostructures is significantly influenced by the deposition temperature and duration. Structural and morphological analyses of as-synthesized SnS nanostructures have been carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). To understand the optical and electronic properties of as-synthesized SnS nanowires, ultraviolet-visible (UV-vis), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) studies were carried out. The SEM and TEM measurements reveal the formation of ultralong SnS nanowires, with an average diameter of 80 nm. A plausible explanation on the vapor-solid-liquid (VLS) growth mechanism based on the experimental results and reported literature has been presented. Furthermore, the field emission characteristics of the SnS nanowires are found to be superior to the other metal chalcogenide nanostructures. The synthesized SnS nanowire emitter delivers a high current density of ∼2.5 mA/cm(2) at an applied electric field of ∼4.55 V/µm. The emission current stability over a period of 6 h is observed to be good. The observed results demonstrate the potential of the SnS nanowire emitter as an electron source for practical applications in vacuum nano/microelectronic devices.

Nanostructured N-doped TiO2 marigold flowers for an efficient solar hydrogen production from H2S.

Nitrogen-doped TiO2 nanostructures in the form of marigold flowers have been synthesized for the first time using a facile solvothermal method. The structural analysis has shown that such an N-doped TiO2 system crystallizes in the anatase structure. The optical absorption spectra have clearly shown the shift in the absorption edge towards the visible-light range, which indicates successful nitrogen doping. The nitrogen doping has been further confirmed by photoluminescence and photoemission spectroscopy. Microscopy studies have shown the thin nanosheets (petals) of N-TiO2 with a thickness of ∼2-3 nm, assembled in the form of the marigold flower with a high surface area (224 m(2) g(-1)). The N-TiO2 nanostructure with marigold flowers is an efficient photocatalyst for the decomposition of H2S and production of hydrogen under solar light. The maximum hydrogen evolution obtained is higher than other known N-TiO2 systems. It is noteworthy that photohydrogen production using the unique marigold flowers of N-TiO2 from abundant H2S under solar light is hitherto unattempted. The proposed synthesis method can also be utilized to design other hierarchical nanostructured N-doped metal oxides.

Hierarchical nanostructured ZnO with nanorods engendered to nanopencils and pin-cushion cactus with its field emission study.

In the present investigation, we report the synthesis of highly crystalline ZnO nanorods engendered to pin-cushion cactus and 1D nanopencil like nanoforms on zinc (Zn) foil via a simple sonochemical assisted hydrothermal route. The work reported herewith is attractive for two reasons: (i) the facile one step solution approach assisted by prior ultrasonication converts nanorods/nanobelts into nanopencils, and (ii) the sharp and quasi-aligned ZnO nanopencils are potential field electron emitters. In addition, the controlled growth of pinhole like ZnO nanopencils and aligned hexagonal ZnO nanodisc was obtained. The changes in the growth rate, diameter, density, and surface area of highly oriented ZnO nanorods are examined. Considering the significances of such novel morphologies, technically detailed formation mechanism has been proposed. The field emission study of pin-cushion cactus like ZnO nanopencils was performed. Field emission measurements demonstrate remarkably low turn-on field which is explained on the basis of a sequential enhancement mechanism involving the consecutive stem and tip contribution. The Folwer-Nordheim (F-N) plot showed nonlinear behavior indicating the semiconducting nature of the emitter. Significantly, emission current is stable at the preset value of 3 µA over the period of 3 h. The simplicity of the synthesis route coupled with the promising emission properties is envisaged to be an important candidate for potential nanoelectronic devices. These unique imperative ZnO nanostructures may have potential for sensors, solar cell, photocatalysis, varisters, etc.