Xiao Ping Zou

ZnO Nanorod Arrays and Nanowires by Hydrothermal Growth

We are reporting here on an inexpensive and facile fabrication method for ZnO nanorod arrays by hydrothermal growth at low temperature (90°C). In our experiment, ZnO nanostructures were grown on glass substrate using an equimolar (0.1M) aqueous solution of Zn(NO3)2•6H2O (zinc nitrate hexahydrate) and C6H12N4 (HMTA) as precursors solution, and using ammonia solution to controlling the pH levels. It enable easily obtained arrayed ZnO nanorods on substrate, and nanowires which grown on nanorod arrays were identified after about 1 month in the air. The growth process of nanorods and the formation mechanism of nanowires were investigated.

Influence of Potassium Chloride on the Electrochemical Deposition of ZnO Plate Films

KCl is usually used as the supporting electrolyte in electrochemical deposition of Zinc oxide materials. Besides the role of supporting electrolyte, it can also influence the morphology of the fabricated materials. In this work, ZnO and zinc hydroxide chloride hydrate (Zn5(OH)8Cl2•H2O) mixture with platelet-like morphology were electrochemically deposited directly on ITO-coated glass substrates at 65°C. The electrolyte was 0.1M Zn(NO3)2•6H2O with KCl concentration varied from 0 to 3.2M. It was found that only ZnO thin film was obtained when the concentration of KCl was below 0.02M. Plates structure appeared as the concentration of KCl increased to 0.04M. Plentiful plates were obtained when the concentration of KCl was 0.05M-0.2M. From the X-ray diffraction, it was confirmed that the plate films was the mixture of ZnO and Zn5(OH)8Cl2•H2O. The plates showed perfect single crystal structure confirmed by selected area electron diffraction. Zn and Zn5(OH)8Cl2•H2O were obtained when the concentration of KCl was above 0.8M.

High-Quality Single-Walled Carbon Nanotubes Synthesized by Floating Catalyst Chemical Vapor Depostion

High-quality single-walled carbon nanotubes (SWNTs) are a key aspect in the emerging field nanotechnology. Although many approaches have been developed, the research on the synthesis of SWNTs is still needed. In this study, we report the synthesis of high-quality SWNTs by floating catalyst chemical vapor deposition, which employs ferrocene as the catalyst precursors. We obtained massive deposits at low temperature region. The deposits were characterized by scanning electron microscopy, transmission electron microscopy, and visual laser Raman spectroscopy. The Raman spectrum obtained from raw deposits shows clear radial breathing mode at the range from 180cm-1 to 300cm-1 and high-intensity graphite mode at 1577.7cm-1 with a shoulder at 1550.5cm-1, and almost no detectable peak around at 1545cm-1, which is induced by defects, is observed. These results indicate that the deposits are high-quality SWNTs.

Carbon Nanotubes Synthesized by Rapid Quenching of Red-Hot Graphite Rod in Ethyl Alcohol

In order to meet the requirements of various applications, considerable efforts have been focused on the new approaches for synthesizing carbon nanotubes. Recently, simple thermal chemical vapor deposition growth technique by pyrolyzing ethyl alcohol has been developed. However, this method needs metallic catalyst. Here, we demonstrate that it is possible to synthesize multi-walled carbon nanotubes without the aid of any catalyst. The as-synthesized products were analyzed by high-resolution transmission electron microscopy (HRTEM). The HRTEM images show that the products are straight multi-walled carbon nanotubes. The synthesis technique of carbon nanotubes is cost-effective because of the catalyst-free process.

Large-Scale Synthesize ZnO Micro/Nano Rods Fabricated from Aqueous Solutions at Low Temperature

ZnO micro/nano rods were grown　on fluorine doped tin oxide (FTO) substrates by aqueous chemical growth (ACG) using Zn(NO3)2•6H2O and C6H12N4 at low temperature. For comparison, the yield of nanorods on indium-tin-oxide (ITO) substrates with same parameters was also discussed. SEM, TEM, SAED and XRD were utilized to characterize morphologies and structures of ZnO crystals. It was indicated that the temperature and the concentration of the solution significantly leads to the yields of the ZnO. Single-crystalline ZnO micro/nano rods could be synthesized via an aqueous solution route without adding alkali solution at 70°C in large area.

2-D ZnO Nanostructures on Aluminum by Solution Method

Two-dimensional ZnO nanostructures with various morphologies were synthesized on aluminum by solution method at 90°C. In our experiment, 0.1M zinc chloride (ZnCl2) was used as a ZnO precursor, and different volume of ammonia solution (25％) was added to the solution. We characterize the morphology and nanostructure of 2-D ZnO nanostructures and study the growth mechanisms of these 2-D structures. It should be noted that the existence of Cl﹣ plays an important role on the formation of 2-D structures.

Lead Hydroxide Nanowires Obtained from Lead Nitrate Solution by Adding Chloride Ions

The synthesis of lead hydroxide nanowires by solution-phase chemical reactions of lead nitrate with alkali by adding sodium chloride was reported. The obtained lead hydroxide nanowires have a length of a few micrometers and a diameter of about several tens of nanometers. The selected-area electron diffraction reveals that these lead hydroxide nanowires are single crystalline. Controlled experiments indicate that lead hydroxide nanowires prefer to form at higher concentration of chloride ions in lead nitrate precursor solutions, such as Cl- : Pb2+ = 5:1 and 6:1.

ZnO Porous Plate Films Application in Quantum Dot Sensitized Solar Cells

As a kind of semiconducting and promising material, ZnO has been extensively used in dye-sensitized solar cells (DSSCs). Quantum dot sensitized solar cells (QDSSCs) has more potential to increase the efficiency of solar cells compared with DSSCs. Here we developed a simple and effective way to fabricate ZnO porous plate films by electrochemical deposition and anneal in air on ITO-coated glass substrates. CdS quantum dots were attached to the surface of the porous plate films by chemical bath deposition technique. Quantum dot-sensitized ZnO porous plate films solar cells exhibited short-circuit current ranging from 0.22-0.57mA/cm2 and open-circuit voltage of 0.42 -0.57V when illuminated with 100 mW/cm2 simulated AM 1.5 G irradiation.

Carbon Nanofibers Synthesized by Ethanol Catalytic Chemical Vapor Deposition

. Carbon nanofibers have been attracted many attentions for their potential applications in nanocomposites and electromagnetic wave-absorbing materials due to their remarkable mechanical, electrical and other properties. Ethanol as carbon source possesses low toxicity, easier storage and transportation. In this paper, we report ethanol catalytic chemical vapor deposition (ECCVD) for synthesizing carbon nanofibers. We utilized ferrocene as catalyst precursor and use ethanol as carbon source to synthesize carbon nanofibers by ethanol chemical vapor deposition. The deposits were characterized by employed scanning electron microscopy, transmission electron microscope and Raman spectroscopy.

Preparation of Silica Nano-Rods by CVD

The straight silica nano-rods with a diameter of about 200nm and smooth surface were synthesized by chemical vapor deposition method at 1300°C. The as-synthesized samples were characterized by means of scanning electron microscopy, energy dispersive x-ray, and transmission electron microscopy. The results show that as-synthesized silica nano-rods have a uniform size, well-defined shape, and smooth surface. However, the morphologies and microstructures of silica nano-rods are affected by synthesis conditions, such as the concentration of the SiOx and the the deposition temperature. On the basis of these experimental results, a possible growth mechanism of silica nano-rods in this process is proposed.