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1.
CuO hollow nanospheres with an average diameter of 400 nm and shell thickness of 40 nm have been successfully synthesized via a simple thermal oxidation strategy with Cu2O solid nanospheres as the precursor. The products have been characterized by X-ray diffraction, transmission electron microscopy and field emission scanning electron microscopy. The formation of CuO hollow nanospheres mainly results from the Kirkendall effect on the basis of temperature-dependent experiments. Furthermore, the electrochemical performance of CuO hollow nanospheres as anode materials for lithium ion batteries has been evaluated by cyclic voltammetry and galvanostatic discharge-charge experiments. The as-prepared CuO hollow nanospheres assembled by nanoparticles exhibit higher initial discharge capacity and better cycle performance than the reported CuO nanoparticles. The hierarchical hollow nanospheres have been demonstrated to take the advantages of nanoparticles and hollow architectures, which could not only shorten the lithium ion transport distance and increase the kinetics of conversion reactions, but also provide suitable electrode/electrolyte contact area and accommodate the volume change associated with lithium ion insertion and extraction.  相似文献   

2.
ZnO–CuO core–shell nanorods and CuO-nanoparticle–ZnO-nanorod integrated structures were synthesized for the first time by a two-stage solution process. Scanning electron microscopy and high-resolution transmission electron microscopy show that the diameter and the length of the nanorods are around 60 and 800 nm, respectively. The morphologies of outer CuO could be varied from nanoparticles to nanoshells by adjusting the solvent and dipping processes of copper (II) nitrate solution. The CuO nanoparticles are single-crystalline or highly textured structures with size of around 30 nm. The CuO shell with thickness of around 10 nm is constructed of nanocrystals with sizes in the range of 3–10 nm embedded in an amorphous matrix. Room-temperature cathodoluminescence measurements of the CuO–ZnO nanocomposites exhibit relatively sharp ultraviolet emissions at 380 nm as well as broad green and yellow emissions at 500 and 585 nm. The p-CuO/n-ZnO one-dimensional nanocomposites are promising for optoelectronic nanodevice applications.  相似文献   

3.
We observed a small-signal gain of Ar2* emission at 126 nm by use of a hollow fiber to guide the high-intensity laser propagation in high-pressure Ar. The small-signal gain coefficient was measured to be 0.05 cm(-1) at 126 nm. Kinetic analysis revealed that the electrons produced by the high-intensity laser through an optical-field-induced ionization process initiated the Ar2* production processes. The increase in the emission intensity was measured to be exp(2.5), with an increase in the fiber length.  相似文献   

4.
Silica capsules with hollow macroporous core–mesoporous shell (HCMS) were synthesized through template-assisted replication of submicrometer-size polystyrene spheres as templates. The silica mesoporous shell exhibited highly ordered hexagonal structure as confirmed by X-ray diffraction pattern and TEM image. The pore diameter and BET surface area of this sample were found to be 2.1 nm and 1387 m2/g, respectively.  相似文献   

5.
Nanosheet-based microspheres of ZnO with hierarchical structures, hollow prism, and coralline-like ZnO nanostructures were successfully prepared by ultrasonic irradiation in acidic ionic liquids (AILs). The hollow spherical is made up of many thin petals, the thickness of which is only about 90 nm. In the presence of AIL2, the one prepared at a frequency of 40 kHz is a mixture of nanofibers with diameters ranging from less than 30 nm to about 100 nm. ZnO nanostructure (with AIL1) reveals lozenge-shape hollow prism structures. The products were hollow prism structure covered with some nanometric-size nanoparticles. The average size of the nanoparticles is in the range of 40?C80 nm. It is found that the ultrasonic irradiation time, ultrasonic frequency, and the AILs influence the growth mechanism and optical properties of ZnO nanostructures. Producing Zno nanostructures by different traditional methods (e.g., hydrothermal method) requires basic media. These methods are not economical and environmentally friendly in many industrial processes. In so doing, a critical problem has been the point that, normally, a high concentration of base causes reactor metal corrosion. This is a simple and low-cost method, which can be expected to be applied in industry in the future. Also, importantly, the structures synthesized in this experiment can indicate a new way to construct nanodevices by self-organization in one step.  相似文献   

6.
利用传输矩阵方法,研究了一维电介质-金属光子晶体的光学特性,该光子晶体通过在Si/SiO2组成的电介质型光子晶体中插入一定厚度Al层形成。计算结果表明,金属层的引入可以有效提高反射效率,[Si(46nm)/SiO2(60nm)/Al(10nm)/SiO2(60nm)]5结构的单位周期传输衰减从[Si(46nm)/SiO2(120nm)]5的7.2dB增大到了20dB;可以得到更宽频率范围的全方向反射带隙,例如[Si(46nm)/SiO2(60nm)/Al(30nm)/SiO2(60nm)]5结构即可提供550nm带宽的全方向反射;同时讨论了金属吸收、金属层厚度及插入位置对其光学特性的影响。这种电介质-金属光子晶体有望作为性能优异的光学反射镜得到应用。  相似文献   

7.
Rime-like NiO Nanowires/nanofibers hierarchical architectures have been fabricated employing a co-precipitation reaction and electrospinning method. The synthesized hierarchical structure was characterized using SEM, XRD and BET analysis methods. The effects of growth temperature and reaction time on the morphologies of the as-prepared structures were investigated by SEM characterization and a possible mechanism for the formation of NiO hierarchical structures is proposed. Based on the nitrogen adsorption and desorption measurements, the BET surface area of the as-obtained sample is 61.0 m2/g and the pore sizes of ca. 5.0 nm. The catalytic efficiency of the NiO nanomaterials developed was evaluated by the photocatalytic degradation of acetaldehyde. In comparison with sphere-like and fiber-like structures, the NiO hierarchical structures show an excellent ability to rapidly acetaldehyde pollutant, which may be attributed to its unique hierarchical and porous surface structures.  相似文献   

8.
In this article, synthesis of nano-sized silica hollow spheres applying positive charged polystyrene as sacrificial templates was introduced. Firstly, nano-sized polystyrene particles were synthesized by emulsifier-free emulsion polymerization under solvothermal condition. Secondly, silica hollow nanospheres were formed through a simultaneous ‘coating-etching’ process. PVP played a key role in the evolution of nano-sized hollow spheres even if the templates were positive charged and the formation mechanism was different from that of previous studies. TEM results revealed that the morphologies of nano-sized silica hollow spheres not only strongly relied on the amount of reactant, but also the sequence of adding them. TGA illustrated that the interiors of nano-sized silica hollow spheres were not completely ‘hollow’. Brunauer-Emmett-Teller (BET) analysis showed that this material had a specific area of 399 m2/g. The water retention property of the materials was also investigated.  相似文献   

9.
Porous copper oxide microrods have been synthesized via calcining copper glycinate monohydrate microrod precursor which was prepared in mild conditions without any template or additive. Several techniques, such as X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller (BET) N2 adsorption–desorption analyses, were used to characterize the structure and morphology of the products. Scanning electron microscopy (SEM) analyses show that the precursor consists of a large quantity of uniform rod-like micro/nanostructures with typical lengths in the range of 25–40 µm and diameters in the range of 0.1–0.35 µm. The microrod-like precursors transformed into porous microrod products after calcination at 450 °C in flow air for 2 h. The BET surface area of the porous CuO microrods was calculated to be 8.5 m² g−1. In addition, the obtained porous CuO microrods were used as catalysts to photodegrade rhodamine B (RhB), methyl orange, methylene blue, eosin B, and p-nitrophenol. Compared with commercial CuO powders, the as-prepared porous CuO microrods exhibit superior properties on photocatalytic decomposition of RhB due to their porous hierarchical structures.  相似文献   

10.
Photoluminescence properties of a single tapered CuO nanowire   总被引:2,自引:0,他引:2  
Photoluminescence spectroscopy has been employed in order to explore the optical emission properties of a single CuO nanowire, grown on a copper grid in static air by simple thermal oxidation method. As the diameter of the single tapered CuO nanowire decreases, the green emission of the nanowire gradually shifts towards the higher energy side. A steady blue shift of 20 nm of the photoluminescence (PL) peak has been attributed to nanosize effect. Higher surface to volume ratio and enhanced surface defects along the growth direction of the nanowire might be responsible for the observed PL behavior. In addition, crystallization process along the length of the nanowire during growth to form pure CuO structure from the precursor state may also have some role in observed shift in the PL peak.  相似文献   

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