Buyong Wan

Flexible full-solid state supercapacitors based on zinc sulfide spheres growing on carbon textile with superior charge storage

Nowadays, it is essential for us to design and fabricate efficient and cost-effective electrode materials for energy conversion and storage systems. Nanostructures are remarkable electrode materials due to their high surface area and large number of active sites. Herein zinc sulfide (ZnS) nanospheres with large surface area are hydrothermally grown on a flexible carbon textile (CT). The specific area and porosity are analyzed in detail under different pressures. The electrode based on the ZnS assembled CT (ZnS-CT) exhibits a high capacitance of 747 F g−1 at a scan rate of 5 mV s−1 in the LiCl aqueous electrolyte. The ZnS-CT is directly used as the binder free electrode for the fabrication of the symmetric flexible full solid state supercapacitor. The ZnS-CT supercapacitor shows excellent electrochemical performance along with light weight, thinness and good flexibility. The ZnS-CT supercapacitor demonstrates good capacitive behavior with a high specific capacitance of 540 F g−1 (areal capacitance of 56.25 F cm−2) at a scan rate of 5 mV s−1 with good rate capability and excellent cycling stability (94.6% retention of initial capacitance after 5000 cycles) at a constant current density of 0.8 mA cm−2. A high energy density of 51 W h kg−1 at a power density of 205 W kg−1 is achieved, indicating excellent ion accessibility and charge storage ability. Furthermore, three charged supercapacitors connected in series can light 4 red color light emitting diodes (2.0 V, 15 mA) for 2 min. ZnS nanospheres with large specific surface area combined with flexible carbon textile substrate offer to be a promising material in energy storage devices with high energy.

Raspite PbWO4 nanobelts: synthesis and properties

Raspite PbWO4, which is rare in nature, poses a great challenge to laboratory preparation and only limited optical and spectroscopic investigations have been conducted on raspite PbWO4 crystals from nature. In this article, we report that raspite PbWO4 nanobelts can be obtained by a facile composite-salt-mediated synthesis method without using any surface-capping agent. The nanobelts are well crystallized with lengths up to hundreds of microns. The synthesis method is simple and cost effective. Our investigation demonstrates that the raspite PbWO4 nanobelts possess excellent blue–green luminescent property at low temperature and highly sensitive photocurrent response to light switches at room temperature. The growth mechanism of the raspite PbWO4 nanobelts, the structure characteristic and the luminescent mechanism are discussed in detail.

Vertically Aligned TiO2 Nanorod Arrays as a Steady Light Sensor

Vertically aligned TiO 2 nanorods have been prepared directly on Ti foil through a one-step environmentally friendly and template-free solution method. X-ray diffraction, field-emission-scanning electron microscopy, and energy-dispersive X-ray spectroscopy have been employed to characterize the synthesized samples. The control of morphology and size of the TiO 2 nanorods can be achieved by varying the solution concentration, hydrothermal temperature, and synthesis time. The influence of nanorod size on the conductivity has been investigated by electrochemical impedance spectroscopy, and the results indicate that the electrical conductivity of thin nanorod arrays is better than that of thick nanorod arrays. Meanwhile, the electrode based on the thin nanorod arrays has shown a highly sensitive and steady photocurrent response under simulated sunlight and UV illumination, which indicates that the nanorod TiO 2 arrays could be a candidate for use in optoelectronic sensor.

Glassy State Lead Tellurite Nanobelts: Synthesis and Properties

The lead tellurite nanobelts have been first synthesized in the composite molten salts (KNO3/LiNO3) method, which is cost-effective, one-step, easy to control, and performed at low-temperature and in ambient atmosphere. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectrum, energy dispersive X-ray spectroscopy and FT-IR spectrum are used to characterize the structure, morphology, and composition of the samples. The results show that the as-synthesized products are amorphous and glassy nanobelts with widths of 200–300 nm and lengths up to tens of microns and the atomic ratio of Pb:Te:O is close to 1:1.5:4. Thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) and investigations of the corresponding structure and morphology change confirm that the nanobelts have low glass transition temperature and thermal stability. Optical diffuse reflectance spectrum indicates that the lead tellurite nanobelts have two optical gaps at ca. 3.72 eV and 4.12 eV. Photoluminescence (PL) spectrum and fluorescence imaging of the products exhibit a blue emission (round 480 nm).

Magnetic and optical properties of Mn doped ZnO nanocrystalline films

We have investigated the properties of Mn-doped ZnO nanocrystalline films grown on zinc foil by hydrothermal method. The microstructure, optical and magnetic properties of these films have been characterized by SEM, XRD, XPS and UV-vis spectrum. The XPS spectra show the doping manganese exists as Mn2+. From UV-vis spectra, the shift in band gap and greater reflectivity can be observed due to Mn doping in ZnO. The magnetic property measurement of the Mn-doped ZnO exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.3902×10−3 emu/cm2 and a coercive field of 47 Oe.

The synthesis and photoelectric response of single-crystalline V 4 O 7 nanowires

Vanadium oxide (V<inf>4</inf>O<inf>7</inf>) nanowires have been synthesized via a hydrothermal route. The synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that the products are of anorthic phase and single crystalline nanowires with diameter of 150 nm and length up to 100 µm. The formation mechanism of the V<inf>4</inf>O<inf>7</inf> nanowires was discussed. Light sensitivity has been investigated on the electrode made from the V<inf>4</inf>O<inf>7</inf> nanowires at different biases. The fast current response has been observed under alternative control of light on and off within 1 s interval, indicating a potential application of the V<inf>4</inf>O<inf>7</inf> nanowires as optical sensors/switches.