Changqing Song

Synthesis of Au-Decorated V2O5@ZnO Heteronanostructures and Enhanced Plasmonic Photocatalytic Activity

A ternary plasmonic photocatalyst consisting of Au-decorated V2O5@ZnO heteronanorods was successfully fabricated by an innovative four-step process: thermal evaporation of ZnO powders, CVD of intermediate on ZnO, solution deposition of Au NPs, and final thermal oxidization. SEM, TEM, EDX, XPS, and XRD analyses revealed that the interior cores and exterior shells of the as-prepared heteronanorods were single-crystal wurtzite-type ZnO and polycrystalline orthorhombic V2O5, respectively, with a large quantity of Au NPs inlaid in the V2O5 shell. The optical properties of the ternary photocatalyst were investigated in detail and compared with those of bare ZnO and V2O5@ZnO. UV-vis absorption spectra of ZnO, V2O5@ZnO, and Au-decorated V2O5@ZnO showed gradually enhanced absorption in the visible region. In addition, gradually decreased emission intensity was also observed in the photoluminescence (PL) spectra, revealing enhanced charge separation efficiency. Because of these excellent qualities, the photocatalytic behavior of the ternary photocatalyst was studied in the photodegradation of methylene blue under UV-vis irradiation, which showed an enhanced photodegradation rate nearly 7 times higher than that of bare ZnO and nearly 3 times higher than that of V2O5@ZnO, mainly owing to the enlarged light absorption region, the effective electron-hole separation at the V2O5-ZnO and V2O5-Au interfaces, and strong localization of plasmonic near-field effects.

Highly efficient field emission properties of a novel layered VS2/ZnO nanocomposite and flexible VS2 nanosheet

Multi-layered VS2 nanosheets were synthesized via a facile hydrothermal process without using any additives or surfactants. Due to the large quantities of sharp edges, a VS2 nanosheet can serve as an efficient edge emitter for field emission (FE). The FE properties of VS2 nanosheets were investigated for the first time. The results indicated that the VS2 nanosheets had an excellent field emission performance with a turn-on field of ∼1.4 V μm−1 and a threshold field of ∼2.6 V μm−1 on a Si substrate. Moreover, the FE properties of ZnO-coated VS2 nanosheets were also investigated. The VS2/ZnO nanocomposite showed enhanced field emission properties with a turn-on field of ∼1.2 V μm−1 and a threshold field of ∼2.2 V μm−1, as well as an excellent emission stability without significant current degradation, which resulted from a well contacted metal–semiconductor junction and extra emission sites. In addition, the FE properties of the VS2 nanosheets were preserved on a highly flexible polyethylene terephthalate (PET) substrate. Approximately the same values of the turn-on field (∼1.8 V μm−1) and the threshold field (∼3.2 V μm−1) were measured on bent and unbent PET substrates.

Cu2S@ZnO hetero-nanostructures: facile synthesis, morphology-evolution and enhanced photocatalysis and field emission properties

A novel hierarchical three-dimensional (3D) Cu2S@ZnO heteroarchitecture was successfully synthesized by a facile three-step synthetic process. FESEM and TEM analyses revealed the formation of the hierarchical 3D structure of the as-prepared Cu2S@ZnO. The purity and crystalline phase of the individual component in the 3D Cu2S@ZnO were determined by a powder X-ray diffractogram. The formation of the hierarchical 3D structure of the as-prepared Cu2S@ZnO leads to multiple p–n junctions formed at p-Cu2S@n-ZnO interfaces, which promote the generation and separation of photoinduced electrons and holes and thus improves the photocatalytic efficiency tremendously. According to the data, after irradiation for 40 min, the remaining MB in solution is about 35% for Cu2S nanoflowers and 9% for Cu2S@ZnO binary nanoflowers. Also, the increases in the overall aspect ratio and the ZnO nanoparticles act as extra emission sites, which help to enhance the field emission properties. The turn-on fields and threshold fields for the Cu2S nanoflowers as well as the Cu2S@ZnO nanoflower hybrid emitters are 3.3 and 9.2 V μm−1, 2 and 6.3 V μm−1, respectively. Compared with the Cu2S nanoflowers, the Cu2S@ZnO hetero-nanoflowers show excellent improvements in both photocatalytic and field emission applications.

Synthesis of a MoS2@MWNT nanostructure with enhanced field emission and electrochemical properties

A polyol method was first employed to synthesize MoS2@MWNT nano-flower composites. Due to their high conductivity, large aspect ratio and sharp edges, an excellent field emission performance was obtained relative to pure MoS2 with the turn-on field decreasing from 5.3 V μm−1 to 2.7 V μm−1 and the threshold field decreasing from 8.0 V μm−1 to 5.3 V μm−1. When used as anode materials for Li-ion batteries in an aqueous electrolyte, the composites exhibit a highest specific capacity of 1217 mA h g−1 at a current of 100 mA g−1, excellent cycling stability and high-rate capability, and a high specific capacity of 851 mA h g−1, which was still retained at a high current density of 1600 mA g−1.