Advanced Materials Research Vols. 652-654

Abstract: CuO nanosheets in rectangle shape with widths around 90 nm and lengths about 180 nm were prepared via a hydrothermal route in the presence of CTAB. MnO2 nanoparticles with diameters around 10nm were loaded onto the surface of CuO nanosheets via an immersion approach followed by a calcination process. X-ray diffraction (XRD), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were applied for the characterization of the as-prepared MnO2 loaded CuO nanosheets. It was found that CTAB played a crucial role in the morphology-controlled synthesis of CuO nanosheets. The hindrance effect resulted from the preferred adsorption of CTAB on certain facets leading to the formation of CuO nanosheets. MnO2 loaded CuO nanosheets can be expected to be a promising catalyst for the heterogeneous catalytic ozonation due to its composite phases, high dispersity, and large specific surface area.

Abstract: Polyacrylonitrile (PAN) nanofibers were fabricated via electrospinning technique, and the modified Fe-polyacrylonitrile nanofibers photocatalysts(Fe-AO-n-PAN) were prepared by a reaction between PAN nanofibers (AO-n-PAN) containing amidoxime group and ferric chloride. Then Fe-AO-n-PAN were used as heterogeneous catalysts in the oxidative degradation reaction of C.I. Reactive Red 195(RR195) in water. This paper investigated the influences on the degree of the conversion from nitrile group to amidoxime group (CP%); analyzed the impacts on the Fe (III) ions content (Q_Fe-PAN) in Fe-AO-n-PAN; and studied the effects of Q_Fe-PAN on the decoloration rate of the dye. The results indicated that the CP% value were greatly enhanced not only with concentration of NH₂OH•HCl increasing, but also gradually with the prolongation of reaction time. In addition, the Q_Fe-PAN of Fe-AO-n-PAN increases with the rise of C_Fe and the CP% value. Finally, Fe-AO-n-PAN have remarkable catalytic activity on the degradation of RR 195, and higher Q_Fe-PAN could promote the catalytic performance of Fe-AO-n-PAN.

Abstract: An improvement in the previously reported seed-mediated chemical synthesis of gold nanorods (GNRs) is reported. Gold nanoparticles were prepared by reducing gold salt with a polysaccharide, chitosan, in the presence of tripolyphosphate (TPP). The obtained gold nanoparticles were characterized with UV-vis spectroscopy and transmission electron microscopy. The study shows that TPP plays an important role in the formation of GNRs.

Abstract: Calcium oxalate dihydrate (COD) nanoparticles with an average size of about 200 nm was prepared by complex precipitation method using potassium oxalate (K2Oxa) and CaCl2 as raw materials, NTA as complexing agent. The effects of initial reactant concentrations, pH in reaction system and dispersion media on morphology and size of the nanoparticles were investigated. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared resonance (FTIR), zetasizer Nano-ZS and transmission electron microscopy (TEM). The results indicated that the prepared sample was COD and its morphology was nearly all elliptical.

Abstract: The three-dimensional dandelion-like zinc oxide nanostructure composed of single-crystal ZnO nanorods was prepared by means of Kirkendall effect while using solvothermal method and taking Zn powder as the source of zinc. In the paper, the composition, structure and appearance of the sample were studied by means of XRD, SEM, RDS, SEAD, TEM, HRTEM and other methods. The method was widely used as a new method for the large-scale preparation of nano/micro zinc oxide material.

Abstract: This thesis is about preparing nano zinc oxide with multilayered cage-like structure by hydrothermal method, and characterizing the structure, composition, and the morphology of the product by means of XRD, SEM, EDS, TG-DTA, N2 absorption method and so on. The photocatalytic activities of ZnO with different morphologies have been evaluated. The result shows that, the multilayered cage-like nano ZnO has higher photocatalytic activity under the radiation of high-pressure mercury lamp; and its photocatalytic performance is better than ZnO nanorod. This method has following advantages: the process is simple and ecofriendly, it doesn't require the introduction of the surfactant, and it is convenient to be employed in mass production etc.

Abstract: Relaxation and local structure changes of a molten Cu297 nanocluster have been studied by molecular dynam ics simulation using embedded atom method when the cluster is rapidly quenched to 850K, 800K, 700K, 600K, 500K, 400K, 300K, 200K, and 100K. With decreasing quenching temperature, details of structure change and relaxation are analyzed. The simulation results show that the final structures are molten at 850K, like-icosahedral geometry at 800K-500K, mainly based on a faced center cubic structure at 400K-200K, non-crystal at 100K. The average energy of atoms is the lowest at 200K. The simulation reveals that the quenching temperature has great affect on the relaxation processes of the Cu297 cluster after β relaxation region.

Abstract: In this work, ZnO nanowires have been successfully grown and developed into a hydrogen gas sensor. The growth technique uses a modified carbothermal reduction at 900 °C to produce ZnO nanowires. This technique has been achieved without using carrier gas and omitted several others parameters. Silicon wafer was used as substrate and gold as catalyst. Elemental analysis and crystal structure were evaluated using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) analysis. Nanowires with the smallest diameter of approximately 25 nm were observed. The hydrogen sensor developed showed response to 500 ppm hydrogen at temperature of 250 °C, 175 °C and 100 °C. The highest and lowest sensitivities were achieved at 250 C (~ 80%- 90%) and 100 °C (~ 15%), respectively. The response times were 10 to 15 s whereas the lowest recovery time was 240 s.

Abstract: Nanofiber are defined as diameter less than 1 micron is under development for future medical application. The simple method was used to prepare a nonwoven in nanofiber of shellac (SHL) and polyvinylpyrrolidone (PVP) is electrospinning machine. The objective of the present study was to investigate the effect of electrospinning process on the physical properties. The SHL/ PVP nanofiber was prepared by dissolving in various rations of SHL/PVP in ethanol solution. Properties of obtained SHL/PVP nanofibers were elucidated. The results demonstrated that nanofibers of SHL/PVP were easily formed after spinning with diameter ranging from a few nanometers to several micrometers. SHL and PVP blended fiber could be formed by the hydrogen bonds attributing to the change in physicochemical properties via FT-IR. This study indicated that a simple method to create nanofiber nonwovens of multiple dissimilar composite polymers providing an approach for controlling diameter size distribution independently from fiber formation. Hence, the knowledge gained should support the development of the product for medical application in near future.

Abstract: An cost effective, and simple method of preparation of surface modified graphene has been described in this work. Graphene oxide (GO) was synthesized from flake graphite by following a modified Hummers’ method. In comparison with other strong reducing agents used in GO reduction, we found thioglycolic acid (TGA) has its unique advantages in forming stable water dispersion of reduced GO. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the successful reduction of GO to graphene. Scanning electron microscopy (SEM) images of the product confirm the presence of thin sheets.