化学气相沉积法制备GaN纳米线和纳米棒

采用浸渍法在未抛光的硅衬底上涂抹一层NiCl2薄膜,通过化学气相沉积法(CVD)制备出高质量的GaN纳米线和纳米棒.X射线衍射(XRD)、傅立叶红外吸收光谱(FTIR)、选区电子衍射(SAED)和高分辨透射电子显微镜(HRTEM)的分析结果表明,采用此方法得到了六方纤锌矿结构的GaN单晶纳米线.通过扫描电镜(SEM)观察发现纳米线的形貌,纳米线的直径在50～200nm之间,纳米棒的直径在200～800nm之间.     

Synthesis of ITO nanowires and nanorods with corundum structure by a co-precipitation-anneal method

Tin-doped indium oxide (ITO) nanowires and nanorods were synthesized by a co-precipitation-anneal process. Both the nanowires and the nanorods had nearly uniform diameter of ca. 60 nm. The nanowires had long and straight morphology with length up to several micrometers. Moreover, the products were the ITO with corundum structure.     

Synthesis and characterization of single crystalline PbO nanorods via a facile hydrothermal method

Single crystalline β-PbO nanorods with diameter range from 40 to 120 nm and length up to 500 nm have been synthesized via a facile hydrothermal method in the presence of citrate. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electro-microscope (HRTEM) and SAED were used to characterize the as-obtained samples. An interesting intermediate state of self-assembled β-PbO rod-like nanoparticles was found and the possible formation mechanism of single crystalline β-PbO nanorods was also discussed.     

Synthesis and photoluminescence of ZnO nanowires/nanorods

We report growth of ZnO nanowires on various substrates using a vapour phase transport method and show that the growth mechanism is vapour-liquid-solid growth. We present photoluminescence data for samples grown on a-plane sapphire at room and low temperatures indicating that the optical quality of these structures is potentially excellent, with intense emission and narrow bound exciton linewidths. The intensity decays rapidly with increasing temperature, indicating a strong temperature-activated non-radiative mechanism whose origin is unclear. We observe a high energy excitonic emission close to the band edge which we assign to the “surface” exciton in ZnO at ∼3.368 eV. This assignment is consistent with the large surface to volume ratio of the nanowire systems under consideration and also indicates that this large ratio has a significant effect on the luminescence even at low temperatures. These surface effects may also be responsible for the rapid decay of the luminescence with increasing temperature via a temperature-activated surface recombination. The nanowire systems appear to offer the prospect of extremely efficient excitonic emission for device applications, and we note that one of the important aspects of achieving this potential will be control of the surface effects via passivation or other means.     

A facile method to prepare PbS nanorods

PbS nanorods with an average diameter of about 30 nm have been successfully prepared through a simple polyglycol-assisted route for the first time. The obtained PbS nanorods have been characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electronic diffraction (SAED). Experiments show that polyglycol plays an important role for the control of the morphology of PbS nanostructures. The preliminary result of the UV-vis absorption spectrum of the PbS nanorods is also presented.     

Selenium nanowires and nanotubes synthesized via a facile template-free solution method

Trigonal selenium (t-Se) nanowires and nanotubes were successfully prepared on a large scale via an environment-friendly synthetic process, in which no templates or surfactants were employed. These t-Se nanowires having a width of 70-100 nm and length up to tens of micrometers were synthesized in absolute ethanol at room temperature, while t-Se nanotubes with outer diameter ranging from 180 to 350 nm were obtained at 85 °C in water system. SEM and TEM analyses of the samples obtained at different stages indicated that the formation of these t-Se 1D nanostructures was governed by a “solid-solution-solid” growth process. The amorphous Se (a-Se) nanoparticles were initially generated and then would transform into crystal seeds for the subsequent growth of nanowires or nanotubes. Detailed experiments found that temperature and solvents as well as concentrations of starting materials were crucial to the formation of final morphology.     

Fabrication of single crystalline cadmium nanowires by a facile low temperature vapor phase method

Single-crystalline cadmium nanowires were successfully fabricated by vaporization of cadmium metal powders in a horizontal quartz tube furnace at 250 degrees C. The vaporization was carried out for 30 minutes and yielded nanowires of diameters of 80 to 250 nm and lengths up to several tens of microns. The nanowires were deposited on a Si (111) substrate kept at the lower temperature zone (150-175 degrees C) of the furnace. When the deposition temperature was lower than this, hexagonal nanodisks were produced. The possible mechanism for the formation of the obtained nanostructures is discussed.     

Synthesis and characterization of silver molybdate nanowires, nanorods and multipods

Silver molybdate nanowires, nanorods and multipods like structures have been prepared by an organic free hydrothermal process using ammonium molybdate and silver nitrate solutions. The powder X-ray diffraction (PXRD) patterns reveal that the silver molybdate belongs to anorthic structure. The thickness, 200–500 nm, for silver molybdate nanorods/wires and 2–5 μm for microrods are identified from SEM images. UV-visible spectrum of silver molybdate nanorods/nanowires shows maximum absorbance at 408 nm. Photo-luminescence (PL) spectrum exhibits UV emission at 335 nm, violet emission at 408 nm and a weak green emission at 540 nm. The influence of hydrothermal synthesis conditions on silver molybdate nanowires, nanorods and multipods compositions were established.     

A facile shape-selective growth of ZnO nanotips and graded nanowires from its oriented nanorods in a saturated ZnS solution

A facile solution-based route is developed for the preparation of distinctive ZnO nanostructures via a dissolution-growth of ZnO nanorods in a saturated ZnS solution at a water-bath temperature of 95?°C. In the dissolution-growth process, a series of novel morphologies including nanotips, tapered and graded nanowires can be conveniently achieved by simply changing the heating time. The pointed ends of the nanotips have a diameter of several nanometers, and the graded nanowires have a gradient change in diameter from a few to tens of nanometers along the longitudinal direction with the size of the thin end matching the Bohr exciton radius of ZnO. Furthermore, the formation mechanism from the ZnO nanorods to the nanotips, to the tapered and graded nanowires is discussed based on shape-evolution observations.     

Synthesis of aluminum borate nanorods by a low-heating-temperature solid-state precursor method

Well-crystalline Al₄B₂O₉ nanorods were synthesized by a low-heating-temperature solid-state precursor method. This process does not involve the use of metal catalyst or protective gas. The products were characterized by thermogravimetry and differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed the products to possess a single phase, large surface area, narrow size distribution of 20-30 nm and lengths up to several micrometers. A self-catalytic growth mechanism of the aluminum borate nanorods is proposed.     

Synthesis of nanorods and nanowires using biomolecules under conventional- and microwave-hydrothermal conditions

In this paper, we review our work on the synthesis and characterization of one-dimensional (1D) nanorods/nanowires and assemblies of inorganic materials with the assistance of several biomolecules under conventional- or microwave-hydrothermal conditions. Two classes of biomolecules have been investigated. One is sugars and their derivatives, and the other is amino acids and their polymers, peptide, and protein. With the assistance of sugars or their derivatives, different kinds of 1D elemental tellurium (Te) and selenium (Se) nanostructures with different sizes and morphologies have been obtained. With the assistance of amino acids or their polymers, 1D semiconductor sulfides and oxide nanowires and assemblies have been successfully synthesized. By providing confined spaces or serving as functional templates for site-specific nanomaterials nucleation or binding, biomolecules appear to direct the growth and/or the assembly of the nanomaterials.     

Synthesis of aluminium borate nanowires by sol-gel method

A sol-gel process followed by annealing was employed to fabricate single crystal aluminium borate (Al₄B₂O₉ and Al₁₈B₄O₃₃) nanowires. The diameter of Al₄B₂O₉ nanowires synthesized at 750 °C annealing is ranging from 7 to 17 nm, and that of Al₁₈B₄O₃₃ nanowires synthesized at 1050 °C annealing is about 38 nm. Instead of the well-known vapor-liquid-solid (VLS) mechanism, self-catalytic mechanism was used to explain the growth of the nanowires.     

Synthesis of nanowires,nanorods and nanoparticles of ZnO through modulating the ratio of water to methanol by using a mild and simple solution method

ZnO nanowires, nanorods and nanoparticles through modulating the ratio of water to methanol have been synthesized by using a mild and simple solution method. The as-prepared ZnO nanostructures have been characterized by atomic force microscopy and X-ray photoelectron spectroscopy. With the increase of the ratio of water to methanol, the morphology of ZnO nanostructures varied form denser nanowires, to sparse nanowires, to nanorods, and then to nanoparticles. The ratio of water to methanol is supposed to play an important role in the formation of ZnO nanostructures. The mechanism of formation is related to the chemical potential, which is simply proportional to their surface ratio.     

Synthesis and investigation of silicon carbide nanowires by HFCVD method

Silicon carbide (SiC) nanowire has been fabricated by hot filament chemical vapour deposition (HFCVD) mechanism in the temperature range of 600–800°C. Synthesis is performed under vacuum in the atmospheres of hexamethyldisiloxane/alcohol (HMDSO/C₂H₅OH) vapour and hydrogen (H₂) gas mixture. In this research dependence of SiC properties on temperature is discussed. Morphology and structural properties of SiC nanowire grown on glass substrate were characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy diffraction spectrometer (EDX), and four-point probe (4PP). Also Mountains Map Premium (64-bit version) software is used to investigate morphological features of samples. In this context, the analysis of the motifs, depth histograms, statistical parameters, texture direction, fractal, and the peak count histograms of the nanostructure surface of samples are carried out. According to analysis, SiC films had a good crystal quality without defects or low residual stress. We found that increasing substrate temperature increases silicon and oxygen doping amount. We also found that electrical resistivity and surface roughness increased by increasing substrate temperature. This study showed that SiC nanowires with high density grew on the free catalyst glass substrate, and the alignment of SiC nanowires decreased.     

Embedding ZnO nanorods into porous cellulose aerogels via a facile one-step low-temperature hydrothermal method

A facile effective one-step low-temperature hydrothermal approach was employed to in situ embed ZnO nanorods into the porous cellulose aerogels. Besides, the preparation of cellulose aerogels is based on a green NaOH/polyethylene glycol solution. The rod-like ZnO has average diameter of about 348 nm and length of about 1.49 μm, and displays wurtzite phase. Meanwhile, the scanning electron microscope and transmission electron microscopy observations confirm that the nanorods are tightly anchored to the aerogels matrixes, and exhibit good dispersion without dramatic agglomeration, indicating that the cellulose aerogels are a class of ideal green matrix materials to support nanoparticles. Moreover, the method might also be extended to fabricate other multifunctional cellulose-based nanocomposites.     

High-yield synthesis of single-crystalline 3C-SiC nanowires by a facile autoclave route

Single-crystalline 3C-SiC nanowires have been synthesized in large scale through a one-step autoclave route by the reaction of SiCl₄, (C₅H₅)₂Fe and metallic Na at 500 °C. Electron microscopy investigations show that the nanowires have typical diameters of 15-50 nm, lengths up to several tens of micrometers and grow along the [111] direction. The possible growth mechanism of the nanowires is discussed.     

ZnO纳米棒的低温湿化学制备

在低温反应条件下,通过超声的方法,以DBS作为表面活性剂,制备了ZnO纳米棒。化学反应的低温条件由冰水浴提供,温度为0~5℃。扫描电子显微镜和光学显微镜观察表明,所制备的纳米棒形状均一,截面为六方型,直径100nm,长度1μm; X 射线衍射表征指出所得到的纳米棒为六方晶型。同时,我们也研究了反应温度、表面活性剂含量、超声、回流时间对ZnO纳米棒形貌的影响。与其它制备方法相比,低温与超声技术可以更为方便获得分布均一,长径比较小的ZnO纳米棒。     

Self-assembled polyaniline nanorods synthesized by facile route of dispersion polymerization

We report the preparation of ordered polyaniline nanorod arrays by a simple method without the use of any template. The synthesis method is by a chemical route, viz. dispersion polymerization of aniline in polyvinyl alcohol. The nanorods obtained have a diameter of 100-500 nm and a length of a few micrometers. Films containing the nanorod assembly have been characterized by SEM, XRD and FTIR spectroscopy. We have also measured I-V characteristics and the temperature dependence of the conductivity of the films. We discuss the formation mechanism of the self-assembled nanostructures, the morphology of the films, and the crystallinity and the transport mechanism.     

Synthesis,characterization and optical properties of CdS nanorods by a simple solution chemistry method

In this paper, we prepared CdS nanorods with controllable size via a facile wet route. Cadmium acetate and sulfur powder were used as precursors and alkylamine and trioctylphosphine (TOP) as solvents in the reactions. Transmission electron microscopy (TEM) studies showed that the length of the nanorods could be controlled by varying ripening time and the amount and types of organic surfactants. Moreover, the result of spectral characterizations demonstrated that the as-prepared nanorods had strong absorption and two photoluminescence emissions in the visible region.