氧化锌自组装微球的微波水热合成与影响因素

以Zn(NO3)2.6H2O和聚乙二醇(PEG,Mn=2000)为原料,采用微波水热法制备出了结晶性能良好的ZnO微球。利用XRD、EDS、SEM、TEM对样品进行了表征,并系统研究了微波水热过程中辐照时间、水热温度、表面活性剂和超声处理等因素对产物形貌和结构的影响。实验表明,ZnO微球是由很多直径约300nm,长1μm的ZnO棒自组装而成,微球直径约为2μm,自组装结构的形成可能与PEG模板的导向作用有关。延长微波辐照时间,ZnO微球的直径有所增加,微球结构的完整性受微波水热温度影响较大。     

ZnO纳米棒及其3D组装结构的微波水热合成与表征

以Zn(NO3)2.6H2O、NaOH和聚乙二醇(PEG,Mn=2000)为原料,采用微波水热法制备了结晶性能良好的ZnO纳米棒及其3D组装结构。利用EDS、XPS、SEM、TEM、FTIR对样品进行了表征,结合光致发光(PL)谱研究了样品的PL性能,并对ZnO纳米棒及其3D组装结构的生长机理进行了简要分析。结果表明,ZnO纳米棒的直径约为300nm,长径比约为3,3D组装结构的直径约为2μm,ZnO纳米棒及其3D组装结构的生长可能与PEG模板的导向作用有关。PL谱表明样品在413~464nm内有很强的蓝光发射特性,这与样品的微观结构有很大关系。     

水热法制备菜花状氧化锌

以Zn(NO3)2.6H2O和N2H4.H2O为原料,采用水热法在180℃制备了菜花状的氧化锌(ZnO)纳米棒束、不规则的长短棒晶须体以及柱状晶须束。用XRD、SEM、FE-SEM及HR-TEM对样品进行了表征。具有六方纤维锌矿结构的ZnO棒或柱的直径分别在100、200nm和1μm左右。以负离子配位多面体生长基元理论讨论了ZnO晶体的生长过程及N2H4.H2O浓度对ZnO形貌的影响。     

无模板合成海胆状薄水铝石超结构及其形成机理

在乙醇-水溶液体系中,在无模板剂的情况下,水热合成由纳米棒自组装成的独特海胆状薄水铝石(AlOOH)超结构.采用XRD、SEM、TEM和SAED对其物相结构和形貌进行了分析,讨论了铝盐前驱体、醇水比例和反应温度对产物形貌的影响.研究结果表明:当铝盐前驱体为AlCl3.6H2O,醇水体积比为1:2,反应温度为200℃时,得到形貌规则、分散均匀的三维海胆状薄水铝石超结构,该海胆状超结构是由直径60~80nm的纳米棒自组装而成,海胆球直径为6~10μm,选区电子衍射表明该海胆状薄水铝石的多晶本质.在薄水铝石海胆状超结构的形成过程中,定向附着机制起到关键性作用.     

在二氧化钛修饰的基体上生长氧化锌纳米棒阵列的研究

以硝酸锌和六亚甲基四胺为主要原料,采用简单、低温的水热法在预先用金红石二氧化钛薄膜修饰过的硅基体上生长了高取向性的ZnO纳米棒阵列．运用扫描电子显微镜(SEM),透射电子显微镜(TEM)和X射线衍射(XRD)对产物的结构和形貌进行了表征．并且讨论了溶液浓度对ZnO形貌的影响．测试结果表明,在0．025mol／L的Zn(NO3)2·6H2O和C6H12N4水溶液中70℃反应4h后的ZnO纳米棒的平均直径为100nm,平均长度为1μm,属于六方纤锌矿结构且沿c轴择优取向生长．并且对制备出的ZnO纳米棒阵列薄膜进行了室温下的荧光测试,发现ZnO纳米棒阵列膜在389nm处具有很强的紫外发射峰,在466nm处有一个比较弱的发射峰．     

晶面择优取向ZnO纳米棒阵列膜的制备及其光催化活性研究

采用简单、低温的方法,在修饰过的Zn片上成功制备出具有高度取向的ZnO纳米棒阵列.用SEM、XRD和PL技术对制备出的ZnO纳米棒的结构和谱学特性进行了表征,并通过降解甲基橙溶液研究了其光催化活性.结果表明,ZnO纳米棒是六方钎锌矿晶,与基底垂直,具有沿(002)晶面择优生长的特征.统计结果显示,湿化学反应24h后90%以上的ZnO纳米棒直径为80～140nm,长度为4μm.在PL谱中观察到3个荧光发射带,中心波长分别位于386nm的紫带、524nm的绿带和450～500nm附近的蓝带.ZnO纳米棒的光催化反应为一级反应,表观速率常数与甲基橙的初始浓度有关.     

花状ZnO超细结构的水热自组装

通过简单的水热合成路线,合成出由ZnO纳米棒束组装的花状结构.其组成结构单元ZnO纳米棒沿［001］晶向生长,呈很好的单晶结构.大部分纳米棒直径约为500nm,长约6.0μm.研究结果表明,在无水乙二胺存在的条件下,氨水（28%, v/v）在ZnO花状结构的形成过程中起到了至关重要的作用.调节氨水的含量,组成结构单元ZnO纳米棒可以组装成不同的花状结构.当加入氨水的量使得溶液的pH值达到10时,即可得到由ZnO纳米棒束组装成的花状结构,并简单讨论了这种花状结构的形状结构的形成机理.      

二氧化钛纳米棒自组装微米球的制备、性能及其生长机理

用水热法在180℃一步合成了TiO2纳米棒自组装微米球,并对其光催化性能和形成机理进行了分析。采用X-射线衍射(XRD),扫描电镜(SEM),透射电镜(TEM)和氮气吸附(BET)对催化剂的物相、颗粒粒径及比表面积进行了表征,结果显示产物为金红石型结构,呈纳米棒自组装微米球形貌,微米球中纳米棒的直径约为30纳米。氮气吸附解附实验表明微米球比表面积为31.2m2/g,介孔的尺寸为3.88nm。催化实验显示其在可见光下的催化能力优于P25。     

离子液体辅助水热合成CeO_2纳米棒（英文）

以CeCl6·6H2O和NH3·6H2O为原料,使用离子液体1-丁基-3甲基咪唑氯盐([Bmim]Cl)辅助水热法在160℃下合成了Ce O2纳米棒。采用X射线衍射(XRD)和高分辨透射电子显微镜(HRTEM)对样品的结构和形貌进行了表征。实验结果表明:使用离子液体辅助水热法制备的产物为Ce O2纳米棒,而没有离子液体时产物则为外形无规则的纳米颗粒。所制备的纳米棒直径为13~25 nm,长度为200~500 nm。增大离子液体的用量将得到纳米颗粒。此外,升高水热温度至180℃所得样品为直径19~24 nm的纳米球,该纳米球由2 nm的纳米晶团聚而成。     

CTAB辅助水热法合成TiO_2微球

以TiCl3为前驱物,NaCl为矿化剂,十六烷基三甲基溴化铵(CTAB)为表面活性剂,用水热法制备出了纳米TiO2微球。用XRD和SEM对制备的样品进行表征。结果表明:微球为金红石型,直径约为1~5μm,微球由纳米棒放射状组装而成,纳米棒长度约为500nm,直径约为40nm。并研究了表面活性剂浓度、矿化剂浓度、反应时间等实验条件对微球的影响。     

The effects of addition of citric acid on the morphologies of ZnO nanorods

ZnO nanorods of 25-100 nm in diameter and 0.2-1 μm in length were fabricated through citric acid assisted annealing process. The microstructure of ZnO nanorods was characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and field-emission scanning electron microscopy, respectively. As a result, it was found that ZnO nanorods were single crystalline and pure. The effects of the growth conditions such as addition of citric acid, annealing temperature on the morphologies of ZnO nanostructures have also been investigated. At the given temperature the length decreased but the diameter increased with addition of the mass of citric acid. With the rising of the calcining heat, the shape of ZnO changed from rod to granule for a given amount of citric acid. Finally, the mechanism for citric acid assisted annealing synthesis of the ZnO nanostructure is discussed.     

Synthesis of well dispersed, regular shape ZnO nanorods: effect of pH, time and temperature

In this paper we presented a systematic study on the morphological variation of ZnO nanostructure by varying the pH of precursor solution, reaction time and reaction temperature via cetyl trimethylammonium bromide-assisted hydrothermal method. The phase and structural analysis was carried out by X-ray diffraction, showed the formation of single phase ZnO with hexagonal wurtzite structure in all the specimens. Morphological and structural analysis was carried out by scanning electron microscopy and transmission electron microscopy showed that the shape of ZnO nanorods were greatly influenced by pH of precursor precipitate while size was affected by reaction time as well as temperature. The selected area diffraction pattern showed that the as synthesized ZnO nanorods were single crystalline in nature and preferentially grow along [0001] direction. A plausible growth mechanism of as prepared ZnO nanostructures was discussed in detail. Furthermore, the optical property of as prepared ZnO nanostructures was studied by photoluminescence spectroscopy.     

Synthesis and photoluminescence properties of aligned Zn2GeO4 coated ZnO nanorods and Ge doped ZnO nanocombs

Aligned Zn₂GeO₄ coated ZnO nanorods and Ge doped ZnO nanocombs were synthesized on a silicon substrate by a simple thermal evaporation method. The structure and morphology of the as-synthesized nanostructure were characterized using scanning electron microscopy and transmission electron microscopy. The growth of aligned Zn₂GeO₄ coated ZnO nanorods and Ge doped ZnO nanocombs follows a vapor-solid (VS) process. Photoluminescence properties were also investigated at room temperature. The photoluminescence spectrum reveals the nanostructures have a sharp ultraviolet luminescence peak centered at 382 nm and a broad green luminescence peak centered at about 494 nm.     

Structural analysis of vertically-aligned single crystalline ZnO nanorods grown on different seed layers with chemical solution deposition

We report the structural properties of the vertically-oriented ZnO nanorods fabricated on various ZnO seed layers with chemical solution deposition (CSD) technique. The ZnO nanorods were prepared using an aqueous solution with Zinc nitrate (Zn(NO3)2 x 6H2O, Aldrich) and hexamethylenetetramine (HMT, Aldrich) in a convection oven. A-plane sapphire substrates with a deposited ZnO thin film were placed upside down in a quartz holder to avoid any micro-crystalline contamination. Especially, our hydro-thermal syntheses are automatically processed on precision pump drive systems (Masterflex) to accurately control the pH of the aqueous solution. The [002] crystal orientation of the ZnO seed layer was observed by the X-ray diffraction pattern. Structural features of ZnO nanorods were systematically analyzed by scanning electron microscopy and tunneling electron microscopy, together with selective area electron diffraction patterns. Experimental observations clearly demonstrated the dependence of the growth direction of the ZnO nanorods on the crystal structures of the ZnO seed layers.     

Synthesis of ZnO nanorods from aqueous solution

In the present work, crystalline one-dimensional ZnO nanorods were synthesized by a PVP (polyvinylpyrrolidone)-assisted hydrothermal process with zinc acetate as the precursor. The major advantage of this technique is the use of water as the solvent: cheaper and more environmentally friendly than alcohol. The as-synthesized ZnO nanorods have diameters of 50-200 nm and lengths up to 5 μm. X-ray powder diffractometry (XRD), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), Fourier transmission infrared spectroscopy (FTIR) were used to characterize the structural and the chemical features of the ZnO nanorods.     

Defect induced room temperature ferromagnetism in well-aligned ZnO nanorods grown on Si (100) substrate

In this work, we report the fabrication of high quality single-crystalline ZnO nanorod arrays which were grown on the silicon (Si) substrate using a microwave assisted solution method. The as grown nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photo-luminescence (PL) and magnetization measurements. The XRD results indicated that the ZnO nanorods are well oriented with the c-axis perpendicular to the substrate and have single phase nature with the wurtzite structure. FE-SEM results showed that the length and diameter of the well aligned rods is about ~ 1 μm and ~ 100 nm respectively, having aspect ratio of 20-30. Room-temperature PL spectrum of the as-grown ZnO nanorods reveals a near-band-edge (NBE) emission peak and defect induced green light emission. The green light emission band at ~ 583 nm might be attributed to surface oxygen vacancies or defects. Magnetization measurements show that the ZnO nanorods exhibit room temperature ferromagnetism which may result due to the presence of defects in the ZnO nanorods.     

Chemical bath deposition of ZnO nanorods for dye sensitized solar cell applications

ZnO nanorods using various molar concentrations have been synthesized through the chemical bath deposition method. X-ray diffraction result shows that the ZnO nanorods are of hexagonal structure. The morphology of the ZnO nanorods has been examined by scanning electron microscopy. The ZnO nanorods have diameters ranging from 100 to 200 nm and length of 1–3 μm. Dye-sensitized solar cells have been assembled by using ZnO nanorod film photoelectrode sensitized using natural dye extracted from lantana camara as sensitizer. The ZnO nanorods have been used as electrode material to fabricate dye sensitized solar cells which exhibited an efficiency of 0.71 %, the maximum efficiency was obtained for films deposited for 0.07 M concentration.     

A simple one-step solvothermal synthesis of hierarchically structured ZnO hollow spheres for enhanced selective ethanol sensing properties

A simple one-step solvothermal method, using ethanolamine as solvent without any additives except zinc source, has been employed to synthesize hierarchically structured ZnO hollow spheres consisting of numerous orderly and radical nanorods with diameter of several tens nanometers and length of 2–3 μm. The ethanolamine and the solvothermal process play the critical role in the synthesis of the ZnO hollow spheres by the primary formation of ZnO crystal nucleus and subsequent transformation into nanorods, which self-assemble into hollow spheres. The morphology and structure of the spheres have been characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and Brunauer–Emmett–Teller N₂ adsorption–desorption analyses. The results also indicate that the sensor based on the prepared ZnO hollow spheres exhibit good ethanol sensing performance, which can be attributed to its structural defects and high surface-to-volume ratio that significantly facilitate the absorption of oxygen species and diffusion of target gas. Besides, the sensor shows high selectivity to ethanol because ZnO as a basic oxide is favored for dehydrogenation of ethanol.     

Growth specificity of vertical ZnO nanorods on patterned seeded substrates through integrated chemical process

A simple and cost effective method has been employed for the random growth and oriented ZnO nanorod arrays over as-prepared and patterned seeded glass substrates by low temperature two step growth process and growth specificity by direct laser writing (DLW) process. Scanning electron microscopy (SEM) images and X-ray diffraction analysis confirm the growth of vertical ZnO nanorods with perfect (0 0 2) orientation along c-axis which is in conjunction with optimizing the parameters at different reaction times and temperatures. Transmission electron microscopy (TEM) images show the formation of vertical ZnO nanorods with diameter and length of ∼120 nm and ∼400 nm respectively. Photoluminescence (PL) spectroscopic studies show a narrow emission at ∼385 nm and a broad visible emission from 450 to 600 nm. Further, site-selective ZnO nanorod growth is demonstrated for its high degree of control over size, orientation, uniformity, and periodicity on a positive photoresist ZnO seed layer by simple geometrical (line, circle and ring) patterns of 10 μm and 5 μm dimensions. The demonstrated control over size, orientation and periodicity of ZnO nanorods process opens up an opportunity to develop multifunctional properties which promises their potential applications in sensor, piezoelectric, and optoelectronic devices.     

Effects of initial precursor and microwave irradiation on step-by-step synthesis of zinc oxide nano-architectures

ZnO nano-architectures were produced with the aid of a fast, simple and low cost microwave-assisted synthesis method. Solid semispherical ZnO nanoparticles on the order of 600 nm in diameter along with rice-like ZnO nanorods 95 nm thick were produced from butanol, triethanolamine (TEA), and zinc acetate dihydrate. Solid spherical ZnO nano-architectures with an average diameter of 250 nm were produced from the same starting materials in addition to NaOH. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to characterize the ZnO nano-architectures as well as the precursor. This method is cheap, fast and simple; capable of producing large quantities of each ZnO nanostructure. Investigation of the step-by-step formation mechanism for each ZnO nanostructure was conducted.