Wuyou Fu

Synthesis of Cu2O nanoframes and nanocages by selective oxidative etching at room temperature.

In recent years, hollow-structure particles (HSPs) have been widely studied due to their unique structures and potential applications. One successful synthetic strategy involves direct construction of HSPs from functional building blocks by processes such as the Kirkendall effect, acid etching, coordination-polymer self-template-directed growth, and solid-state thermal decomposition process for the preparation of Cu7S4, [2] Fe2O3, [3] ZnO, and MnO2 [5] HSPs. However, all of the reported HSPs require further heator acid-treatment processes, which have disadvantages such as increased costs and environmental pollution. Therefore, it remains a great challenge to develop a simple, mild (at room temperature), and environmentally friendly method for the one-pot synthesis of HSPs with well-defined shape. Cu2O is a typical p-type direct band gap semiconductor with a band gap of 2.17 eV and has potential applications in solar-energy conversion, electrode materials, sensors, and catalysts. Considerable effort has been devoted to obtaining hollow Cu2O structure by employing techniques such as hydrothermal synthesis, microemulsions, template synthesis, and acid etching. Qi and co-workers prepared octahedral Cu2O nanocages by Pd-catalytic reduction of an alkaline copper tartrate complex with glucose followed by a catalytic oxidation process. More recently, truncated rhombic dodecahedral Cu2O nanoframes and nanocages were synthesized by particle aggregation and acid etching. In both synthetic processes, expensive and acidic or toxic solvents were used. Here we report a cheap and green synthetic route for Cu2O nanoframes and nanocages with single-crystal walls. In our synthetic strategy, polyhedral Cu2O particles were first prepared by adding a weak reducing agent (glucose) to a solution of copper citrate complex with polyvinylpyrrolidone (PVP) as capping agent, and then Cu2O nanoframes and nanocages were obtained in situ by oxidative etching at room temperature. Perfect Cu2O nanoframes were taken from the reaction mixture after the solution was exposed to air for 16 days at room temperature. Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) images provided insight into the nanostructure and morphology of the Cu2O nanoframes. As shown in Figure 1A, the Cu2O nanoframes are

Large-Scale Synthesis and Microwave Absorption Enhancement of Actinomorphic Tubular ZnO/CoFe2O4 Nanocomposites

Actinomorphic tubular ZnO/CoFe(2)O(4) nanocomposites were fabricated in large scale via a simple solution method at low temperature. The phase structures, morphologies, particle size, shell thickness, chemical compositions of the composites have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The as-synthesized nanocomposites were uniformly dispersed into the phenolic resin then the mixture was pasted on metal plate with the area of 200 mm x 200 mm as the microwave absorption test plate. The test of microwave absorption was carried out by the radar-absorbing materials (RAM) reflectivity far field radar cross-section (RCS) method. The range of microwave absorption is from 2 to 18 Hz and the best microwave absorption reach to 28.2 dB at 8.5 Hz. The results indicate that the composites are of excellence with respect to microwave absorption.

Electrodeposition of Cu2O films and their photoelectrochemical properties

Well-defined cuprous oxide (Cu2O) thin film electrodes were electrodeposited on indium-doped tin oxide (ITO) substrates from a slightly acidic Cu(II) acetate solution. The morphologies of Cu2O film were tunable by altering the deposition potential, reaction time, solution temperature and the NaCl concentration. In particular, the Cu2O morphologies evolved from dendritic branching to cube-like with the increasing of the NaCl concentration. A growth mechanism was proposed according to the experimental results. In addition, a photocurrent of 0.06 mA cm−2, an open-circuit photovoltage (Voc) of 0.38 V, and a significant energy conversation efficiency of 0.01% were obtained under 100 mW cm−2 UV-visible illumination of the dendritic Cu2O thin film.

Simple synthesis method of Bi2S3/CdS quantum dots cosensitized TiO2 nanotubes array with enhanced photoelectrochemical and photocatalytic activity

A TiO2 nanotubes array film with nanowires directly formed on top (denoted as TiO2 NTWs) was prepared by an anodization method (potentiostatic anodization growth). Bi2S3 QDs were sensitized on the CdS/TiO2 NTWs array by a simple successive ionic layer adsorption and reaction (S-SILAR). A short-circuit photocurrent density of 2.16 mA cm−2 was obtained under an illumination of AM 1.5 G. The data of the photoelectrochemical performance test show that Bi2S3/CdS co-modification can boost the photocurrent density of the bare TiO2 NTWs by up to 308%. The photocatalytic activity was tested by treating rhodamine B (RhB) and methyl orange (MO) solutions, which were degraded completely after 240 min and 210 min, respectively. The present study shows the Bi2S3/CdS/TiO2 NTWs array can be applied in photocatalytic devices, and the greatest advantages are low-cost, easy reuse and recyclability.

Synthesis, optical and gas sensitive properties of large-scale aggregative flowerlike ZnO nanostructures via simple route hydrothermal process

Large-scale aggregative flowerlike ZnO nanostructures, consisting of many bunches of nanorods at different orientations with a diameter of about 60 nm and a length of 1 µm, have been synthesized through a simple hydrothermal process at a lower temperature. The x-ray power diffraction pattern indicates that the novel flowerlike ZnO nanostructures are hexagonal, and the selected area electron diffraction reveals that the ZnO nanorods are single crystal in nature and preferentially grow along [0 0 1]. Raman spectrum, room-temperature photoluminescence and UV–vis absorption spectra are also discussed. Furthermore, the influence of the reaction time on the morphology of the ZnO nanostructures is investigated, and a possible growth model is proposed. Finally, the gas sensor based on the ZnO nanostructures exhibits high sensitivity for ethanol as well as quick response and recovery time due to the high surface-to-volume ratio.

Structural, electrical and optical properties of yttrium-doped ZnO thin films prepared by sol–gel method

Yttrium-doped ZnO thin films were deposited on silica glass substrates by the sol–gel method. The structural, electrical and optical properties of yttrium-doped ZnO thin films were investigated systematically and in detail. All the thin films have a preferred (0 0 2) orientation. When compared with the electrical resistivity values of films without annealing treatment, the values of films annealed in the reducing atmosphere were decreased by about three orders of magnitude. The lowest electrical resistivity value was 6.75 × 10−3 Ω cm, which was obtained in the 0.5 at% yttrium-doped ZnO thin film annealed in nitrogen with 5% hydrogen at 500 °C. In room-temperature photoluminescence (PL) spectra, two PL emission peaks are found in the pure ZnO thin film; one is the near-band-edge (NBE) emission at 3.22 eV and the other is a green emission at about 2.38 eV. Nevertheless, the green emission is not found in the PL of the yttrium-doped ZnO thin films. The low-temperature PL spectrum of the undoped ZnO thin film at 83 K is split into well-resolved free and bound excition emission peaks in the ultraviolet region, but the NBE emission of the 5 at% yttrium-doped ZnO thin film at 83 K has only one broad emission peak.

Synthesis and Photocatalytic Activity of Fe-doped TiO2 Supported on Hollow Glass Microbeads

In this paper, Fe-doped TiO2 photocatalyst supported on hollow glass microbeads (Fe-TiO2/beads) is prepared by dip-coating method, which uses hollow glass microbeads as the carriers and tetrabutylorthotitanate [Ti(OC4H9)4] as the raw material. The phase structure, ingredient, morphologies, particle size and shell thickness of the products are characterized by X-ray powder diffraction (XRD), energy-dispersive spectroscopy (EDS) and field emission scanning electron microscope (FESEM). The feasibility of photocatylic degradation of Rhodamine B (RhB) under illumination of UV-vis light is studied. The results show that the core-shell structure catalyst is composed of Fe-doped anatase TiO2 and hollow glass microbeads, and the catalytic activity of the TiO2 is markedly enhanced by Fe ion doping. The optimum concentration of Fe ion is 0.1% (molecular fraction) in the precursor and the photocatalytic activity can be increased to 98% compared with that of the undoped one. The presence of ferrum elements neither influences the transformation of anatase to rutile, nor creates new crystal phases. The possible mechanism of photocatalytic oxidation is also discussed.

A NiO/TiO2 junction electrode constructed using self-organized TiO2 nanotube arrays for highly efficient photoelectrocatalytic visible light activations

One dimensional (1D), self-organized TiO2 nanotube arrays are known to have excellent charge transport properties and a NiO/TiO2 junction is efficient in separating electron–hole pairs. This paper describes the synthesis of a NiO/TiO2 junction electrode constructed using self-organized TiO2 nanotube arrays combining the above two properties. The self-organized TiO2 nanotube arrays used in this study were prepared by anodizing titanium films, which resulted in closely packed n-type TiO2 tubes with an inner pore diameter of 60–90 nm, a wall thickness of approximately 15 nm and a length of 600 nm. The NiO/TiO2 junction was synthesized by electroless plating and annealing which resulted in TiO2 nanotube arrays coated with a layer (about 200 nm in thickness) of NiO particles (20–40 nm). The resulting NiO/TiO2 junction electrode enabled us to obtain an enhanced photocurrent (3.05 mA cm−2) as compared with a TiO2 electrode based on TiO2 nanotube arrays (0.92 mA cm−2) under AM 1.5 G (100 mw cm−2) at a bias of 0.65 V.

High catalytic activity of a PbS counter electrode prepared via chemical bath deposition for quantum dots-sensitized solar cells

A PbS counter electrode (CE) has been fabricated by a chemical bath deposition method, and can function as a counter electrode with high catalytic activity for quantum dots-sensitized solar cells (QDSSCs). The PbS nanoparticles can act as an excellent electrical tunnel for fast electron transport from an external circuit to the CE. Electrochemical impedance spectroscopy reveals a low charge transfer resistance (Rct1) between polysulfide and PbS, the optimized PbS CE shows an Rct1 as low as 15.42 Ω cm2. The current density–voltage curves of the QDSSCs were investigated under AM 1.5 light at 100 mW cm−2. CdS quantum dots-sensitized solar cells with the PbS CE achieved a power energy conversion efficiency of 2.91% and showed no obvious degradation of current density over 72 h under ambient conditions.

Simple synthesis and characteristics of Mo/MoS2 inorganic fullerene-like and actinomorphic nanospheres with core?shell structure

High yields of Mo/MoS2 inorganic fullerene-like and actinomorphic nanospheres with a core?shell structure have been successfully synthesized by the one-step reaction of sulfur and molybdenum nanospheres under a hydrogen atmosphere, in which the Mo nanospheres were prepared by the wire electrical explosion method. The shell thickness of MoS2 is about 4?10?nm and exhibit an expansion of about 4.2?1% along the c-axis. Observed from high-resolution transmission electron microscopy images, unreacted molybdenum lying between the (002) layers of MoS2 contributes to the larger expansion besides the strain in the bent layer and the crystal defects; the preferred growth orientations for MoS2 on the surface of Mo have two directions under different annealing temperatures: parallel to the (110) plane of Mo, presenting an actinomorphic phase, and perpendicular or having certain angles to the (110) plane, showing a fullerene-like phase. The actinomorphic Mo/MoS2 can be used for catalysis and intercalation. The fullerene-like phase can be applied as a solid lubricant to enhance the structural rigidity and load bearing capacity of hollow MoS2. In addition, the core?shell nanospheres exhibit a little higher onset temperature and a narrow temperature range against oxidation with a weaker exothermic peak than conventional 2H-MoS2.