Xueting Chang

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.

Prolonged antibacterial effect of silver nanocomposites with different structures

This study describes the synthesis of silver nanocomposites (Ag NCs), with different structures, decorated with silica nanoparticles (SiO2 NPs) and their antibacterial activity was evaluated. The core-shell microspheres were fabricated by the deposition of polydopamine (PDA) formed by the spontaneous oxidative polymerization of dopamine. Simultaneously, Ag(+) ions were reduced to nanosilver and subsequently deposited on the surface of the SiO2/PDA spheres to form SiO2/PDA/Ag NPs. Moreover, nanosilver encapsulated in mesoporous SiO2 NPs (Ag-MSN) were investigated for bactericidal activity to facilitate comparisons. Bacterial growth curves and reactive oxygen species (ROS) assays indicated that both Ag-MSN and SiO2/PDA/Ag NPs exhibited antimicrobial activity; however, at different stages, due to their distinct structures. This study revealed that the production of ROS and damage to the membrane were the two major mechanisms of the bactericidal activity of Ag NCs. The antibacterial mechanisms for each NC are discussed and supported by observations from transmission electron microscopy.

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.

Promoting Barrier Performance and Cathodic Protection of Zinc-Rich Epoxy Primer via Single-Layer Graphene

The effect of single-layer graphene sheets (Gr) on the corrosion protection of zinc-rich epoxy primers (ZRPs) was investigated. Scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS) were used to characterize morphology and composition of the coatings after immersion for 25 days. The cross-sectional SEM images and X-ray photoelectron spectroscopy (XPS) confirmed that the addition of single-layer graphene facilitated assembling of zinc oxides on the interface between the coating and the steel. The open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) measurements revealed that both the cathodic protection and barrier performance of the ZRP were enhanced after addition of 0.6 wt. % Gr (Gr0.6-ZRP). In addition, the cathodic protection property of the Gr0.6-ZRP was characterized quantitatively by localized electrochemical impedance spectroscopy (LEIS) in the presence of an artificial scratch on the coating. The results demonstrate that moderate amounts of single-layer graphene can significantly improve corrosion resistance of ZRP, due to the barrier protection and cathodic protection effects.

Copper Sulfide-Based Plasmonic Photothermal Membrane for High-Efficiency Solar Vapor Generation

Solar vapor generation has attracted tremendous attention as one of the most efficient ways of utilizing solar energy. It is highly desirable to develop low-cost, eco-friendly, and high-efficiency solar absorbers for practical applications of solar vapor generation. Herein, a three-dimensional plasmonic covellite CuS hierarchical nanostructure has been synthesized as the light-absorbing material via a facile one-pot hydrothermal method for structurally integrated solar absorbers with microporous poly(vinylidene fluoride) membrane (PVDFM) as the supporting material. A broadband and highly efficient light absorption has been achieved in the wavelength of 300-2500 nm, along with high water evaporation efficiencies of 90.4 ± 1.1 and 93.3 ± 2.0% under 1 and 4 sun irradiation, respectively. Meanwhile, stable performance has been demonstrated for over 20 consecutive runs without much performance degradation. To the best of our knowledge, this is the highest performance among the copper sulfide-based solar absorbers. With the additional features of low-cost and convenient fabrication, this plasmonic solar absorber exhibits a tremendous potential for practical solar vapor generation.

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...