Minghui Shao

Low-temperature solution synthesis of CuO/Cu2O nanostructures for enhanced photocatalytic activity with added H2O2: synergistic effect and mechanism insight

CuxO (CuO, CuO/Cu2O, and Cu2O) nanostructures have been controllably synthesized through a facile low-temperature solution method. The morphologies and compositions of CuxO nanostructures were well controlled by tuning the reductant amount of hydroxylamine hydrochloride, which experienced the transformation of nanosheets to octahedrons as well as the phase change of CuO to Cu2O. The as-grown samples showed photodegradation selectivity to MO (maximum photocatalytic efficiency of 52% for methyl orange (MO) and 16% for rhodamine B (RhB) after 180 min photodegradation) and different photocatalytic activities in the absence or presence of H2O2 (62% without H2O2 and 82% with H2O2). The morphological transformations of as-grown samples were observed after the photocatalytic measurement in the presence of H2O2. The structural and morphological features after photodegradation were studied by XPS, SEM, and TEM investigations, revealing the possible mechanism of the as-prepared samples whereby the photodegradation of organic dyes occurred on the surface with respect to the adsorption ability, structure, and morphology of CuxO. In addition, H2O2 played an important role in the photodegradation of organic dyes.

Fabrication and properties of ZnO/GaN heterostructure nanocolumnar thin film on Si (111) substrate

Zinc oxide thin films have been obtained on bare and GaN buffer layer decorated Si (111) substrates by pulsed laser deposition (PLD), respectively. GaN buffer layer was achieved by a two-step method. The structure, surface morphology, composition, and optical properties of these thin films were investigated by X-ray diffraction, field emission scanning electron microscopy, infrared absorption spectra, and photoluminiscence (PL) spectra, respectively. Scanning electron microscopy images indicate that the flower-like grains were presented on the surface of ZnO thin films grown on GaN/Si (111) substrate, while the ZnO thin films grown on Si (111) substrate show the morphology of inclination column. PL spectrum reveals that the ultraviolet emission efficiency of ZnO thin film on GaN buffer layer is high, and the defect emission of ZnO thin film derived from Zni and Vo is low. The results demonstrate that the existence of GaN buffer layer can greatly improve the ZnO thin film on the Si (111) substrate by PLD techniques.

One-pot hydrothermal synthesis of CdS decorated CuS microflower-like structures for enhanced photocatalytic properties

CdS decorated CuS structures have been controllably synthesized through a one-pot hydrothermal method. The morphologies and compositions of the as-prepared samples could be concurrently well controlled by simply tuning the amount of CdCl2 and thiourea. Using this strategy, the morphology of the products experienced from messy to flower-like morphologies with multiple porous densities, together with the phase evolution from pure CuS to the CdS/CuS composites. Serving as a photocatalyst, the samples synthesized with the addition of 1 mmol cadmium chloride and 3 mmol thiourea during synthetic process, showed the best photocatalytic activity, which could reach a maximum photocatalytic efficiency of 93% for methyl orange (MO) photodegradation after 150 min. The possible mechanism for the high photocatalytic efficiency of the sample was proposed by investigating the composition, surface area, structure, and morphology before and after photocatalytic reaction.

One-Step Solvothermal Method to Prepare Ag/Cu2O Composite With Enhanced Photocatalytic Properties.

Ag/Cu2O microstructures with diverse morphologies have been successfully synthesized with different initial reagents of silver nitrate (AgNO3) by a facile one-step solvothermal method. Their structural and morphological characteristics were carefully investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the experimental results showed that the morphologies transformed from microcubes for pure Cu2O to microspheres with rough surfaces for Ag/Cu2O. The photocatalytic activities were evaluated by measuring the degradation of methyl orange (MO) aqueous solution under visible light irradiation. The photocatalytic efficiencies of MO firstly increased to a maximum and then decreased with the increased amount of AgNO3. The experimental results revealed that the photocatalytic activities were significantly influenced by the amount of AgNO3 during the preparation process. The possible reasons for the enhanced photocatalytic activities of the as-prepared Ag/Cu2O composites were discussed.

Hierarchical flowerlike metal/metal oxide nanostructures derived from layered double hydroxides for catalysis and gas sensing

The development of advanced functional materials for catalytic reduction and gas sensing is one of the most important issues for the detection and prevention of environmental pollution. Herein, hierarchical peony-like metal/metal oxide (Co/Al2O3 and Co3O4/Al2O3) composites assembled with uniform nanosheets were successfully synthesized using CoAl layered double hydroxides as self-sacrificial templates. Co/Al2O3 composites exhibited high surface dispersions and low metal–support interactions which can be confirmed by a series of structure and morphology characterizations. With the above advantages, Co/Al2O3 composites showed remarkable catalytic ability and stability towards 4-nitrophenol (4-NP) reduction with a nearly 100% conversion within 3 minutes and a conversion efficiency over 98% after 10 successive recycles. After that, Co/Al2O3 composites with different Co/Al ratios were fabricated to investigate the optimal Co content in the catalytic reduction of 4-NP. The results indicated that when the Co/Al ratio reaches 4 : 1, the fabricated composites have the best catalytic reduction abilities. Furthermore, the fabricated Co3O4/Al2O3 gas sensors exhibited a superior response time of 1 s towards 50 ppm ethanol with a sensing response of 8.9. These excellent catalytic reduction and gas sensing abilities could be attributed to the unique peony-like hierarchical structure which could provide large surface areas and abundant active sites. More importantly, this work provided a new synthesis strategy to design materials with enhanced catalytic reduction and gas sensing abilities, which will be beneficial to the development of highly effective catalysts and gas sensing materials.

Anodic Oxidation Synthesis of One-Dimensional TiO2 Nanostructures for Photocatalytic and Field Emission Properties

One-dimensional (1D) TiO2 micro/nanostructures have received more and more attentions because of their potential applications in environmental issues. This paper reviews the most recent activities in TiO2 nanostructures with an emphasis on the authors’ own results especially on those synthesized using anodic oxidation method. The review begins with a survey of the effects of fabrication methods and the experiment conditions on the obtained TiO2 nanostructures, and then focuses on their 1D nanostructures, including the syntheses, characterizations, formation mechanisms, photocatalytic, and field emission properties. Finally, we conclude this review with the perspectives and outlooks on the future developments in this field.

Template-assisted electrodeposition of iron nanostructures.

A facile approach to prepare iron nanostructures (nanowires, nanotubes, branched and multi-branched nanotubes) is reported by reduction of metal sulfide salts in the pores of an anodic aluminum membranes (AAMs) template with a back side Au sheet. The crystal structures and morphologies of Fe nanostructures are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM) and transmission electron microscope. The results indicate that the Fe nanostructures can replicate the inner architectures of the templates. The thickness of the Au film deposited on the back side of the AAMs and the inner structures of AAMs are the two key factors to determine the final morphologies of Fe nanostructures. This approach can be broadened to fabricate other metal nanostructures.