Vertically aligned NiS nano-flakes derived from hydrothermally prepared Ni(OH)2 for high performance supercapacitor

In present work,the vertically aligned Ni S nano-flakes composed thin film is prepared by anionic exchange process in which hydrothermally prepared Ni（OH）2is used as a parent thin film and Na2S as a sulfide ion source.This synthesis process produced fully transformed and shape-controlled nano-flakes of Ni S from nano-flowers of Ni（OH）2.The electrochemical supercapacitor properties of Ni S electrode are studied with cyclic voltammetry（CV）,galvonostatic charge discharge（GCD）and electrochemical impedance spectroscopy（EIS）techniques.Highly porous surface area（85 m^2/g）of Ni S nano-flakes makes large material contribution in electrochemical reaction stretching specific capacitance（Cs）of 880 F/g at scan rate of 5 m V/s and 90%electrochemical stability up to 4000 CV cycles in 2 M KOH electrolyte.Further,the flexible solid-state symmetric supercapacitor device（Ni S/PVA–Li ClO4/Ni S）has been fabricated using Ni S electrodes with polyvinyl alcohol（PVA）–lithium perchlorate（Li ClO4）gel electrolyte.The Ni S/PVA–Li ClO4/Ni S device exhibits specific capacitance of 56 F/g with specific energy of 14.98 Wh/kg and excellent cycling stability after 2000 cycles.In addition,the Ni S/PVA–Li ClO4/Ni S device demonstrates illumination of red light emitting diode（LED）for 60 s,which confirms the practical applicability of Ni S/PVA–Li ClO4/Ni S device in energy storage.

Cadmium sulfide thin films growth by chemical bath deposition

Cadmium sulfide（Cd S） thin films have been prepared by a simple technique such as chemical bath deposition（CBD）. A set of samples Cd S were deposited on glass substrates by varying the bath temperature from 55 to 75 °C at fixed deposition time（25 min） in order to investigate the effect of deposition temperature on Cd S films physical properties. The determination of growth activation energy suggests that at low temperature Cd S film growth is governed by the release of Cd^（2＋） ions in the solution. The structural characterization indicated that the Cd S films structure is cubic or hexagonal with preferential orientation along the direction（111） or（002）, respectively. The optical characterization indicated that the films have a fairly high transparency, which varies between55% and 80% in the visible range of the optical spectrum, the refractive index varies from 1.85 to 2.5 and the optical gap value of which can reach 2.2 e V. It can be suggested that these properties make these films perfectly suitable for their use as window film in thin films based solar cells.

Mobility and sulfidization of heavy metals in sediments of a shallow eutrophic lake, Lake Taihu, China

The technique of DGT（diffusive gradients in thin films） using three diffusive gel thicknesses was applied to estimate the mobility and bioavailability of heavy metals in sediments and porewater of Lake Taihu, China. The DGT results showed significantly positive correlations between Co, Pb, Cd and Mn, and Ni and Fe concentrations in porewater. Cu and Zn showed a significantly negative correlation with Mn, due to Cu combination with carbonates and Zn derived from agricultural pollution, respectively. The rank order of average concentrations of Co, Ni and Cd at each station was DGT1.92〉DGT0.78〉 DGT0.39, suggesting stronger resupply from sediments to porewater when using thicker diffusive gels. Comparing centrifugation and DGT measurements, Co, Ni and Cd are highly labile; Mn and Fe are moderately labile; and Cu, Zn and Pb are slightly labile. The variations of AVS concentrations in sediment cores indicate that metal sulfides in deeper layers are easily diffused into surface sediments.