Shibin Sun

Solvothermal synthesis of Ce-doped tungsten oxide nanostructures as visible-light-driven photocatalysts

Cerium (Ce)-doped tungsten oxide nanostructures have been generated by using a simple solvothermal method with cerium chloride salts and tungsten hexachloride as precursors. The as-synthesized samples were characterized by electron microscopy, x-ray diffraction and x-ray photoelectron spectrometry. The photocatalytic activities of the samples were evaluated by degradation of methyl orange in an aqueous solution under visible light irradiation. Results showed that the as-synthesized samples underwent morphological evolution with decreasing W/Ce molar ratio, from one-dimensional bundled nanowires through straighter, shorter and thicker bundled nanorods to two-dimensional bundled blocks, then to a mixture of bundled nanorods and agglomerated nanoparticles, and finally to particle agglomerates. The Ce-doped tungsten oxides exhibited better photocatalytic activities than that of the undoped tungsten oxide. The cerium-doped tungsten oxide bundled blocks synthesized with a W/Ce molar ratio of 15:1 possessed the most effective photocatalytic activity among the tested samples. These novel nanomaterials may find potential applications as visible-light-driven photocatalysts.

MnO2/g-C3N4 nanocomposite with highly enhanced supercapacitor performance

A novel sandwich-like MnO2/g-C3N4 nanocomposite (NC) based on the integration of high-density MnO2 nanorods (NRs) onto the surfaces of two-dimensional (2D) g-C3N4 sheets has been successfully fabricated through a facile soft chemical route at low temperature. The MnO2/g-C3N4 NC electrode enhanced the supercapacitor (SC) performance, benchmarked against both the bare MnO2 NRs electrode and the MnO2/graphene oxide (GO) NC electrode, exhibiting high specific capacitance of 211 F/g at a current density of 1 A/g, with good rate capacity and cycling stability. The sandwich-like hybrid structure, the unique 2D structure of the g-C3N4 sheets and the presence of nitrogen in the g-C3N4 all contributed to the promising SC performance of the MnO2/g-C3N4 NC. This work demonstrated the advantages of the g-C3N4 sheets over the commonly-used GO sheets in the design of novel hybrid composite for enhanced capacitance performance of MnO2-based electrochemical SCs, and the results could be extended to other electrode materials for SCs.

Large-scale production of tungsten trioxide nanoparticles for electrochromic application

Large-scale, high yield production of tungsten trioxide (WO3) particles was successfully realized by using a facile, high-temperature, catalyst-free, solid evaporation route with ammonium paratungstate tetrahydrate as raw material. The crystalline structure, size, and morphology of the as-synthesized WO3 particles were systematically investigated by combined techniques of X-ray diffraction and electron microscopy, as a function of reaction temperature, deposition temperature, carrier gas flow rate, and size of the quartz tube. With low carrier gas flow rate (1–2 L min−1), the WO3 products collected from different deposition regions were found to exhibit a diversity of forms, such as thick rods, irregular, polyhedral, and octahedral particles, depending on the reaction temperature. At a reaction temperature of 1350 °C, increasing the carrier gas flow rate led to the formation of semi-spherical or quasi-spherical WO3 particles with decreased size and improved size distribution. A reaction temperature of 1350 °C and an Ar flow rate of 6 L min−1 yielded optimized quasi-spherical WO3 nanoparticles with high size uniformity, which have been found to exhibit stable electrochromic performance with high colour contrast and H+ insertion ability. The WO3 nanoparticles that can be effectively produced in high quantity are promising electrochromic candidates for potential applications in large-area smart windows.

THERMAL PROCESSING OF BUNDLED TUNGSTEN OXIDE NANOWIRES

Taking the wide band gap one-dimensional (1-D) tungsten oxide nanowires as an example, we here demonstrate systematically the physical characteristics of thermally processed nanowires at temperatures ranging from 400°C to 1000°C, for the first time. Accompanied by a significant drop of specific surface area from 151 m2/g for the as-prepared nanowires to 109 m2/g and 66 m2/g subject to annealing at 400°C and 450°C, dramatically morphology evolution and phase transformation have also been observed. The nanostructured bundles became straighter, larger in diameters and shorter in length, and eventually became irregular particles with size up to 5 µm. The Brunauer-Emmett-Tettler (BET) result suggests that 400°C can be considered as a top temperature limit in nanodevice design where high surface area is important, e.g. in gas sensors. A protocol for thermally processing of these bundled tungsten nanowires has been established.

Ag-W18O49-GO Nanocomposite as Highly Effective Antibacterial Agent with Capturing-Killing Mechanism

In this work, a novel nanocomposite (NC) based on the decoration of Ag nanoparticles (NPs) and W18O49 nanorods (NRs) on the GO surfaces was prepared using combined techniques of solvothermal method and photochemical process. Compared with the Ag-GO NC, the Ag-W18O49-GO NC exhibited enhanced long-term antibacterial activity against the bacterium of Bacillus sp.1NLA3E (Bacillus sp.). The antibacterial mechanisms of both the Ag-GO and Ag-W18O49-GO NCs were distinctly revealed by observation of the direct interaction between the Ag NPs, W18O49 NRs, or GO sheets and the bacterial cells. Results showed that the GO sheets in the NCs mainly acted as supports for trapping or wrapping the bacterial cells, and it was the Ag NPs or W18O49 NRs grown on the GO surfaces that caused direct damage to the cells. The synergistic effects between the Ag NPs or W18O49 NRs and the GO sheets resulted in the prominent long-term antibacterial effect of the Ag-W18O49-GO NC. This work provides in-depth understanding of the mechanism...