CuO/ZnO Nanocomposite Gas Sensors Developed by a Plasma‐Assisted Route

CuO/ZnO nanocomposites were synthesized on Al₂O₃ substrates by a hybrid plasma‐assisted approach, combining the initial growth of ZnO columnar arrays by plasma‐enhanced chemical vapor deposition (PE‐CVD) and subsequent radio frequency (RF) sputtering of copper, followed by final annealing in air. Chemical, morphological, and structural analyses revealed the formation of high‐purity nanosystems, characterized by a controllable dispersion of CuO particles into ZnO matrices. The high surface‐to‐volume ratio of the obtained materials, along with intimate CuO/ZnO intermixing, resulted in the efficient detection of various oxidizing and reducing gases (such as O₃, CH₃CH₂OH, and H₂). The obtained data are critically discussed and interrelated with the chemical and physical properties of the nanocomposites.     

Deposition of ZnO multilayer on LiNbO3 single crystals by DC-magnetron sputtering

Zinc oxide (ZnO) thin films were deposited on LiNbO₃ (LN) single crystals with 200 nm thicknesses by three different ways, where coating of zinc (Zn) film was followed by thermal oxidation for four, two, and one steps with 50, 100, and 200 nm thicknesses repeatedly. Sample, which was produced at 4-step of deposition and oxidation of Zn layer, showed high transmittance and low structural defect due to a lower photoluminescence intensity and Urbach energy. Average grain size in X-ray diffraction (XRD), scanning electron microscopy (SEM) micrograph, and atomic force microscopy (AFM) images for multilayer of ZnO was lower than monolayer of ZnO thin films. Applying multilayer coating technique leads to decrease of surface roughness and scattering on light on surface and fabrication of LiNbO₃ waveguides with lower optical loss.     

Facilitating epitaxial growth of ZnO films on patterned GaN layers: A solution-concentration-induced successive lateral growth mechanism

The hydrothermal epitaxy of ZnO films on a patterned GaN layer with a honeycomb etching hole array is demonstrated. Through m-planes of the GaN layer exposed on the vertical walls of the etching holes, highly crystalline ZnO films via multiple lateral growth stages can be realized. It is found that higher concentrations of zinc nitrate hexahydrate (ZNH) and hexamethylenetetramine (HMT) in hydrothermal solution yield a larger number of ZnO molecules to speed up ZnO growth during the initial stage of hydrothermal growth, also create secondary crystals and initialize further lateral growth stages to bridge neighboring ZnO prisms after smooth surfaces formed on the m-plane of a ZnO prism. A successive lateral growth mechanism that strongly depends on ZNH and HMT concentrations in the hydrothermal solution is proposed and discussed.     

The synthesis of Cu/plate-like ZnO nanostructures and their self-assembly mechanism

A composite Cu/ZnO nanostructure with Cu nanoparticles supported on ZnO hexagonal nanoplates has been successfully fabricated by a heating approach, using their metal oleate salts as the precursors without any additives. Combined Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and other examination technologies, the structural properties and formation mechanism of as-synthesized Cu/ZnO nanocomposites are studied in detail. The results reveal that the nanostructures are plate-like with uniform shape and size, and Cu nanoparticles exhibit specific (111) plane matching with the (002) facet of ZnO, indicating a surface-induced interaction mechanism. Further characterization demonstrates that copper nanoparticles can be generated by a decomposition/self-reduction route of copper salts, and the oleate ions act as dual roles in the process: reducing and protecting agents. The difference of decomposition temperature between metal oleates also plays important roles in the formation of Cu/ZnO nanostructure. In addition, the catalytic performance of these nanocomposites is evaluated and it can be found that compared with Cu/rod-like ZnO, as-synthesized samples are highly selective for methanol.     

Local piezoelectric response of ZnO nanoparticles embedded in a photosensitive polymer

Local piezoelectric properties of ZnO nanoparticles (NPs) embedded in a photo‐epoxy polymer are investigated by piezoresponse force microscopy (PFM). Integrating ZnO NPs into a photosensitive SU‐8 polymer matrix not only retains the highly desired piezoelectric properties of the ZnO, but also preserves photosensitivity and optical transparency of the SU‐8 polymer. These results have strong implications for simple photolithography based low‐cost fabrication of piezoelectric microelectromechanicalsystems (MEMS) and nanoelectromechanicalsystems (NEMS) in both sensing and energy harvesting applications. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

聚苯胺／ZnO复合材料纳米线的制备及界面特性研究

为获得优异性能的纳／微米结构的有机一无机复合功能材料，进而探讨在纳／微米结构的电子器件或其它领域的潜在应用，在纳米线聚苯胺（PANi）悬浮液的存在下，采用水热方法进行了ZnO的生长，并用所制得的ZnO／PANi复合材料构筑了叉指结构的聚合物基柔性化学传感器原型器件。采用透射电镜（TEM）、X射线衍射（XRD）、X射线光...     

Effect of incorporation of reduced graphene oxide on ZnO-based dye-sensitized solar cells

Here, we demonstrate a facile method to improve the cell performance of ZnO-based dye sensitized solar cell by incorporating different amount of reduced graphene oxide (rGO). Overall photo-to-current conversion-efficiency (PCE) of the device 3 with 0.75 mL rGO exhibits a 1.3 times improvement compared to bare ZnO. The electrochemical impedance spectroscopy (EIS) measurements show that the enhancement could be attributed to the improvement of electron transport/injection and the decrease of the charge recombination in the device, which arise from the formation of rGO-based Schottky junction in ZnO-photoanode.     

Fast Photodegradation of Malachite Green using Nano-ZnO on Ceramic MgAl Carbonate Layered Double Hydroxides Support

The nanopowders of Mg-Al carbonate layered double hydroxides (MgAl-LDH) were prepared via coprecipitation process. ZnO nanoparticles were homogeneously coated on the ceramic MgAl-LDH surface. After calcination at 500 ℃ for 4 h, X-ray diffraction and scanning electron microscopy were employed to investigate the crystal structure and morphology, respectively. It was demonstrated that ZnO nanoparticles were successfully prepared on ceramic MgAl-LDH support. The obtained nano-ZnO photocatalyst showed a high pho-tocatalytic degradation of malachite green. The enhanced photocatalytic property can be attributed to both high photocatalytic activity of ZnO and good adsorption behavior of ceramic MgAl-LDH, in which the aky structure of MgAl-LDH plays an important role.     

Crystallization Behavior and Properties of B-Doped ZnO Thin Films Prepared by Sol-Gel Method with Di erent Pyrolysis Temperatures

Boron-doped zinc oxide transparent (BZO) films were prepared by sol-gel method. The effect of pyrolysis temperature on the crystallization behavior and properties was systematically investigated. XRD patterns revealed that the BZO films had wurtzite structure with a preferential growth orientation along the c-axis. With the increase of pyrolysis temperature, the particle size and surface roughness of the BZO films increased, suggesting that pyrolysis temperature is the critical factor for determining the crystallization behavior of the BZO films. Moreover, the carrier concentration and the carrier mobility increased with increasing the pyrolysis temperature, and the mean transmittance for every film is over 90% in the visible range.     

Fine luminescent patterning on ZnO nanowires and films using focused electron-beam irradiation

ZnO thin films and nanowires (NWs) were precisely treated by focused electron-beam (E-beam) irradiation with a line width between 200 nm and 3 μm. For both ZnO films and NWs, an increased green emission was clearly observed for the E-beam-treated parts. Using a high-resolution laser confocal microscope, the photoluminescence intensities for E-beam-treated ZnO structures increased with increasing dose 1.0 × 10¹⁷–1.0 × 10¹⁸ electrons/cm². The resistivity of a single ZnO NW increased from 56 to 1800 Ω cm after the E-beam treatment. From the results for the annealed ZnO thin films, we analyzed that the variations in PL and resistivity were due to the formation of vacancies upon focused E-beam irradiation.