反应时间对球状及棒状ZnO纳米晶的影响

本实验采用溶液法合成球状及棒状ZnO纳米晶。X射线衍射分析(XRD)显示合成的纳米晶为六方纤锌矿结构ZnO。紫外可见光(UV-vis)光谱和透射电镜(TEM)图表明通过改变反应时间可以控制ZnO纳米棒的长度。随着反应时间从90min延长到360min,纳米棒的长度可以从25nm长大到60nm。同时,纳米晶的室温光致发光谱(PL)具有强烈的近带边发射,在LED和LD等光电器件上有一定的应用前景。     

ZnO纳米棒的微波合成及Pt掺杂对其气敏性能的改善

以Zn(NO3)2·6H2O和NaOH为原料,CTAB为表面活性剂,微波加热到90℃,反应30min,成功制备了ZnO纳米棒.X射线衍射仪(XRD)和扫描电镜(SEM)结果表明,产物是六方纤锌矿结构ZnO纳米棒,长度为1～5μm,直径为50～100nm左右.对ZnO纳米棒进行了Pt掺杂,并对掺杂前后的气敏性能进行了对比...     

ZnO纳米带梳的制备及生长机理的研究

采用化学气相沉积(CVD)法成功制备出ZnO纳米带梳,实验过程不需要催化剂.X射线衍射仪(XRD)分析结果表明,ZnO纳米带梳为高度结晶的六方纤锌矿结构;利用扫描电子显微镜(SEM)观测,所制样品是由纳米带组成梳状形貌,纳米带梳的形成经过两个步骤:先通过VS机制形成微米带,而梳的齿通过自催化生长平行于(0001)极性面形成.对样品的光致荧光(PL)谱测量发现了位于～395nm和495nm处的室温光致发光峰.     

Sn掺杂ZnO纳米带的制备及其光致发光性能研究

采用热蒸发法制备了单晶Sn掺杂ZnO纳米带,其中Sn的掺杂含量约为5%(原子分数).X射线衍射(XRD)结果表明Sn掺杂ZnO纳米带为单相纤锌矿结构.X射线光电子能谱(XPS)表明样品中Sn的价态为4+.样品的室温光致发光谱(PL)在445.8nm处存在较强的蓝光发射峰,对其发光机制进行了分析.     

纳米氧化锌的溶剂热法合成及其光学性能

以醋酸锌为原料,以乙二胺一水为混合溶剂,利用溶剂热法低温快速制备出分散均匀的氧化锌(ZnO)纳米粒子.探讨了溶剂热条件如温度和时间对于ZnO纳米晶的形成及其形貌和光学性能的影响.X-射线粉末衍射和能量散射x-射线能谱分析表明,产物是纯的六方纤锌矿结构的ZnO.透射电镜形貌观察显示,产物为均匀纳米粒子,直径为20～30 nm.所合成粉体紫外可见光谱表明,其紫外吸收大约为2.98eV,计算其直接带隙宽度为3.10eV.光致发光光谱显示ZnO纳米粒子具有良好的结晶性和光学性质.     

ZnO纳米棒的制备与气敏性能的研究

以Zn(NO3)2·6H2O和NaOH为原料,CTAB为表面活性剂,通过微波辅助液相反应过程在低温下成功地制备了ZnO纳米棒.X射线衍射谱和扫描电镜结果表明,产物是六方纤锌矿结构ZnO纳米棒,长度为5～30μm,直径为0.1～1μm.气敏性能测试表明,所制备的ZnO纳米棒对H2S气体具有较好的选择性,但灵敏度不高.对ZnO纳米棒进行In掺杂后,对H2S气体的灵敏度和选择性大幅提高,在工作温度为332℃时,对体积分数为50X10-5的H2S灵敏度为29.217,说明In掺杂的ZnO纳米棒是有潜力的探测H2S气体的气敏传感器材料.     

一维纳米ZnO制备技术及应用研究进展

一维纳米ZnO由于具有良好的光学、电学和压电性能,在纳米光电子器件方面具有潜在的应用价值,已受到广泛的关注和重视.介绍了ZnO纤锌矿的晶体结构及性质,阐述了一维纳米ZnO的制备技术及其在光电子器件、传感器以及太阳能电池等方面的潜在应用,并进一步探讨了目前存在的问题及其今后的研究发展方向.     

纳米ZnO颗粒的制备及其对颗粒污泥硝化反应的影响

通过溶胶凝胶法制备纳米氧化锌颗粒.利用XRD、红外光谱和SEM图谱对制备的纳米氧化锌的物相和形貌进行表征,在实验溶液中检测纳米氧化锌的溶解,通过SEM观察ZnO对污泥形态的影响,同时也研究ZnO对污泥硝化反应的影响.结果表明,实验制备的六方纤锌矿ZnO粉末纯净,结晶性良好,而且ZnO颗粒为纳米颗粒且分散性良好.在实验溶...     

ZnO纳米棒水热法制备及其发光性能

采用水热法在玻璃基底上成功制备出了ZnO纳米棒.用x射线衍射仪(xRD)和扫描电子显微镜(SEM)对ZnO纳米棒的晶体结构和表面形貌进行了表征,初步探讨了ZnO纳米棒的生长机理;同时对ZnO纳米棒的光致发光性能进行测量,分析了水热温度和反应时间对ZnO纳米棒光致发光性能的影响.结果表明:ZnO纳米棒呈现六方纤锌矿结构,具有沿(002)晶面择优生长特征;随着水热反应温度的升高,ZnO纳米棒的发光强度逐渐增强;随着反应时间的延长,ZnO纳米棒发光强度在1～3 h内增强,而在3～10 h反而减弱.     

阵列纳米ZnO的一种新颖的制备方法及其光致发光特性研究

将锌粉、炭粉和氧化锌粉末混合,用简单的热蒸发方法一步就合成了大量的尖锥状纳米ZnO阵列,该方法克服了其它制备方法需要先单独制备催化剂再合成ZnO的缺点而且得到产物不含杂质.用SEM、EDX、XRD和PL对样品进行了形貌、结构和发光特性分析.结果表明,生成的锥状阵列纳米ZnO为六方纤锌矿结构,产物中氧的含量不足,初步探讨了阵列纳米ZnO结构的生长机理和光致发光性质.     

ZnO四足和多足纳米结构的制备和光致发光性能研究

采用简单的热蒸发法,在没有使用载气和催化剂的情况下成功制备出ZnO四足和多足纳米结构。采用场发射扫描电镜、X射线衍射、高分辨透射电子显微镜和荧光分光光度计研究了ZnO纳米结构的形貌、结构和光致发光性能。结果表明所合成的ZnO是由具有六方纤锌矿结构的四足和多足纳米结构组成,足部呈棒状并沿[0001]方向生长。提出了四足和多足ZnO纳米结构的生长机制。在室温下的光致发光光谱中,494nm处出现一个较强的绿色发射峰,391nm处出现一个较弱的紫外发射峰。     

Urchin-like ZnO nanostructures: Synthesis, characterization and optical properties

Urchin-like ZnO nanostructures have been synthesized by a two-step thermal evaporation method. The product was characterized with scanning electron microscopy, X-ray powder diffraction, transmission electron microscopy, and spectrofluorometry. The results of characterization revealed that the urchin-like ZnO nanostructure consists of a spherical metallic Zn core and wurtzite ZnO nanowires growing on the surface of the ZnO buffer which covers the Zn core and the growth directions of wurtzite ZnO nanowires are along <10-10>. According to the analysis on these results, a possible two-step growth mechanism was proposed to explain the formation of the urchin-like ZnO nanostructures. The fluorescence-emission mechanisms were also discussed.     

Influence of process variables on growth of ZnO nanowires by cathodic electrodeposition on zinc substrate

Influence of the deposition duration and electrolyte concentration on the structural and morphological features of the ZnO thin films, grown by cathodic electrodeposition on zinc substrate followed by annealing in air at 400 °C, have been investigated. The surface morphology of the as-synthesized films shows two distinct features, presence of ‘2-dimensional nanosheets’ on the area near the electrolyte-air interface and ‘granular’ nanostructures, below the interface region. However, upon annealing, the formation of ZnO nanowires, possessing length of several microns and diameter less than 20 nm, on the entire substrate is observed. The X-ray and selected area electron diffraction patterns clearly confirm the polycrystalline nature of the ZnO nanowires.     

Chemical vapor deposition-based growth of aligned ZnO nanowires on polycrystalline Zn<Subscript>2</Subscript>GeO<Subscript>4</Subscript>:Mn substrates

ZnO nanowires have been grown on polycrystalline Zn₂GeO₄:Mn substrates for the first time using a chemical vapor deposition method. Both Zn and ZnO sources were used to supply Zn vapor in the growth process of ZnO nanowires. The Zn₂GeO₄:Mn substrates were prepared using solid-state ceramic synthesis methods, and average grain sizes of ~1 μm were achieved. The nanowires of diameters in the range of 100–200 nm and length of ~30 μm were observed. In addition to nanowires, other morphologies of ZnO nanostructures, such as ZnO tetrapods, were observed when Zn powder was used as the source for the CVD growth. The results reveal that polycrystalline substrates are also promising as novel alternative substrates for growth of ZnO nanostructures. The as-synthesized ZnO nanowire/Zn₂GeO₄:Mn composites are being developed for future electroluminescent devices.     

Synthesis of doped ZnS one-dimensional nanostructures via chemical vapor deposition

ZnS one-dimensional (1D) nanostructures doped with Mn or Cd have been rapidly synthesized in large scale via a chemical vapor deposition process. Using Zn and S as precursors and MnCl₂ or Cd as doping source, the doped ZnS 1D nanostructures were obtained. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to characterize the as-synthesized ZnS nanostructures. The catalytically grown ZnS 1D nanostructures, including nanowires and nanoribbons, are tens of micrometers in length. All the products are wurtzite ZnS in structure and preferentially grow along the [001] direction. The room temperature photoluminescence properties of these doped ZnS nanostructures are presented.     

Catalyst-free synthesis of well-aligned ZnO nanowires on In0.2Ga0.8N, GaN, and Al0.25Ga0.75N substrates

Well-aligned ZnO nanowires have been synthesized vertically on In0.2Ga0.8N, GaN, and Al0.25Ga0.75N substrates, using a catalyst-free carbon thermal-reduction vapor phase deposition method for the first time. The as-synthesized nanowires are single crystalline wurtzite structure, and have a growth direction of [0001]. Each nanowire has a smooth surface, and uniform diameter along the growth direction. The average diameter and length of these nanowires are 120-150 nm, and 3-10 )m, respectively. We suggest that the growth mechanism follow a self-catalyzing growth model. Excitonic emission peaked around 385 nm dominates the room-temperature photoluminescence spectra of these nanowires. The room-temperature photoluminescence and Raman scattering spectra show that these nanowires have good optical quality with very less structural defects.     

Synthesis, characterization and optical properties of star-like ZnO nanostructures

Star-like ZnO nanostructures were synthesized in bulk quantity by thermal evaporation method. The morphologies and structure of ZnO nanostructures were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results demonstrated that the as-synthesized products consisted of star-like ZnO nanostructure with hexagonal wurtzite phase. The legs of the star-like nanostructures were preferentially grown up along the [0001] direction. A vapor-solid (VS) growth mechanism was proposed to explain the formation of the star-like structures. Photoluminescence spectrum exhibited a narrow ultraviolet emission at around 380 nm and a broad green emission around 491 nm. Raman spectrum of the ZnO nanostructures was also discussed.     

Structural and optical properties of ZnO nanostructures grown on silicon substrate by thermal evaporation process

Two types of one-dimensional ZnO nanostructures have been synthesized on silicon substrate by the thermal evaporation of metallic zinc powder in the presence of oxygen without the use of any catalyst or additives. Detailed structural analysis revealed that the formed ZnO nanostructures are single crystalline with wurtzite hexagonal phase and grow along the [0001] direction in preference. Presence of a sharp and strong, optical phonon Raman-active E₂ (high) mode and suppressed E₁ (LO) mode in the Raman spectra, in both the cases, confirmed the good crystallinity with the wurtzite hexagonal phase for the as-grown products. A sharp and dominant near band edge emission with a suppressed green emission is observed from the as-synthesized nanostructures which affirmed the good optical properties with very less structural defects for the grown nanostructures.     

Self-catalytic growth and photoluminescence properties of ZnS nanostructures

Mass production of uniform wurtzite ZnS nanostructures has been achieved by a H₂-assisted thermal evaporation technique. X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) observations show that the ZnS nanostructures consist of nanobelts, nanosheets with a hexagonal wurtzite structure. The as-synthesized nanobelts have a length of several tens of micrometers and a width of several hundreds of nanometers. Self-catalytic vapor-liquid-solid (VLS) growth and vapor-solid (VS) growth are proposed for the formation of the ZnS nanostructures because neither a metal catalyst nor a template was introduced in the synthesis process. Room-temperature photoluminescence measurement indicates that the synthesized ZnS nanostructures have a strong emission band at a wavelength of 443 nm, which may be attributed to the presence of various surface states.     

Raman spectra and photoluminescence properties of In-doped ZnO nanostructures

In-doped ZnO nanostructures with four different morphologies, which are nanotetrapods, nanocombs, nanowires, and nanodisks, have been synthesized on silicon substrates by a simple thermal evaporation method. The XRD patterns show the In-doped ZnO nanostructures are all with the hexagonal wurtzite structure, and a slight difference in lattice parameters had been detected among the samples with various morphologies. The Raman spectra demonstrate that the vibrational mode of 2LA, which is very weak in undoped ZnO, was strongly enhanced with indium ion doping into ZnO structures. The photoluminescence (PL) measurements indicate that the nanodisks have a relative strong ultraviolet (UV) emission than other three kinds of samples.