Quanshui Li

PHOTOLUMINESCENCE SPECTRA AND MAGNETIC PROPERTIES OF HYDROTHERMALLY SYNTHESIZED MnO2 NANORODS

In this paper, single crystalline tetragonal MnO2 nanorods have been synthesized by a simple hydrothermal method using MnSO4⋅ H2O and Na2S2O8 as precursors. The crystalline phase, morphology, particle sizes and component of the as-prepared nanomaterial were characterized by employing X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDS). The photoluminescence (PL) emission spectrum of MnO2 nanorods at room temperature exhibited a strong ultraviolet (UV) emission band at 380 nm, a prominent blue emission peak at 453 nm as well as a weak defect related green emission at 553 nm. Magnetization (M) as a function of applied magnetic field (H) curve showed that MnO2 nanowires exhibited a superparamagnetic behavior at room temperature which shows the promise of synthesized MnO2 nanorods for applications in ferrofluids and the contrast agents for magnetic resonance imaging. The magnetization versus temperature curve of the as-obtained MnO2 nanorods shows that the Neel transition temperature is 94 K.

Molecular dynamics simulation of dealloyed layer-enhanced dislocation emission and crack propagation

Abstract Three-dimensions molecular dynamics (MD) method by employing the embedded atom method (EAM) potential is used to simulate the effect of stress corrosion-induced dealloyed layer existed on the surface of a crack of Cu 2 Au alloy on dislocation emission and crack propagation. The simulations show that the existence of a dealloyed layer enhances dislocation emission and crack propagation, i.e., decreases the critical stress intensity for dislocation emission from K Ie =0.62 MPam 1/2 to K Ie *=0.556 MPam 1/2 and that for crack propagating after emitting large amounts of dislocations from K IP =1.14 MPam 1/2 to K IP *=1.06 MPam 1/2 . This indicates that dealloyed layer-induced tensile stress can help the applied stress to enhance dislocation emission and crack extension.

Enhanced UV-Visible Light Photocatalytic Activity by Constructing Appropriate Heterostructures between Mesopore TiO2 Nanospheres and Sn3O4 Nanoparticles

Novel TiO2/Sn3O4 heterostructure photocatalysts were ingeniously synthesized via a scalable two-step method. The impressive photocatalytic abilities of the TiO2/Sn3O4 sphere nanocomposites were validated by the degradation test of methyl orange and •OH trapping photoluminescence experiments under ultraviolet (UV) and visible light irradiation, respectively. Especially under the visible light, the TiO2/Sn3O4 nanocomposites demonstrated a superb photocatalytic activity, with 81.2% of methyl orange (MO) decomposed at 30 min after irradiation, which greatly exceeded that of the P25 (13.4%), TiO2 (0.5%) and pure Sn3O4 (59.1%) nanostructures. This enhanced photocatalytic performance could be attributed to the mesopore induced by the monodispersed TiO2 cores that supply sufficient surface areas and accessibility to reactant molecules. This exquisite hetero-architecture facilitates extended UV-visible absorption and efficient photoexcited charge carrier separation.

Induction of zinc particles on the morphology and photoluminescent property of globular Zn/ZnO core/shell nanorod heterojunction array architectures

Zn/ZnO metal/semiconductor nanostructures were successfully synthesised by a facile zinc-rich chemistry liquid-phase approach with zinc microspheres as sacrificial templates at ambient temperature. A series of globular Zn/ZnO core/shell structures and hollow microsphere architectures self-assembled by Zn/ZnO nanorod heterojunction arrays were obtained by controlling the amount of zinc particles. The structure, morphology, composition and optical properties of the products have been characterised by X-ray diffraction, scanning electron microscopy, Raman spectroscopy and photoluminescent spectroscopy. A possible growth mechanism of the Zn/ZnO nanostructures has been proposed based on the structural analysis. The growth mechanism of Zn/ZnO hollow microspheres is ascribed to Kirkendall effect. A new strong blue emission at 440 nm and a green emission around 500 nm with an enhancement over one order of magnitude compared with the pure ZnO sample have been observed. These emission bands are attributed to two kinds of mechanisms that have been discussed in detail.

Synthesis and characterization of 3D Cu0.45Mn0.55O2 nanoflowers with novel photoluminescence and magnetic properties

In this paper, three-dimensional (3D) Cu0.45Mn0.55O2 nanoflowers self-assembled by interconnecting dense stacked single-crystalline nanoplates have been prepared using the template-free hydrothermal growth method. The morphology, phase structure and composition of the as-prepared nanomaterial were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDX). FESEM and TEM analyses show that the size of 3D Cu0.45Mn0.55O2 nanoflowers is in the range of 1–1.5 μm and the thickness of interconnected nanoplates is about 40 nm on the average. The photoluminescence (PL) spectra of the as-prepared Cu0.45Mn0.55O2 nanostructures at room temperature exhibits prominent emission bands located in red–violet spectral region. Moreover, magnetic investigations revealed the weak ferromagnetic behavior of the as-prepared Cu0.45Mn0.55O2 nanoflowers and reported for the first time using vibrating sample magnetometer (VSM).

Tunable Synthesis of 3D ZnS Architectures and the Optical Properties

The complex 3D ZnS architectures with two morphologies—sea urchin-like and flower-like structure—have been synthesized by changing the solvent under solvothermal conditions. The morphology, phase structure and optical properties of the products have been characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results show that the as-prepared two kinds of 3D ZnS architectures show wurtzite structure and are highly crystalline. Two emission bands and a broad emission band are observed for sea urchin-like and flower-like structure, respectively, and attributed to defects and elemental S surface states luminescence.