采用高分子自组装ZnO纳米线及其形成机理

介绍了一种能在各种晶面的硅衬底上制备垂直于衬底取向生长的ZnO纳米线阵列的新方法. 该法采用高分子络合和低温氧化烧结反应, 以聚乙烯醇(PVA)高分子材料作为自组装络合载体来控制晶体成核和生长. 首先通过PVA侧链上均匀分布的极性基团羟基(—OH)与锌盐溶液中的Zn²⁺离子发生络合作用, 然后滴加氨水调节络合溶液pH值为8.5±0.1, 使络离子Zn²⁺转变为Zn(OH)₂, 再将硅片浸入此溶液中, 从而在硅衬底表面得到较均匀的Zn(OH)₂纳米点, 随后在125 ℃左右Zn(OH)₂纳米点通过热分解转化为ZnO纳米点, 其后在420 ℃烧结过程中衬底上的ZnO纳米点在PVA高分子网络骨架对其直径的限域下逐渐取向生长成ZnO纳米线, 并且烧结初期PVA碳化形成的碳通过碳热还原ZnO为Zn, 再在氧气氛中氧化为ZnO的方式在纳米线顶端形成了催化活性点, 促进了纳米线顶端ZnO的吸收. 烧结后碳逐渐氧化被完全去除. 采用场发射扫描电镜(FE-SEM)、透射电镜(TEM, HR-TEM)和X射线衍射(XRD)对纳米线的分析结果表明, ZnO纳米线在硅衬底上分布均匀, 具有六方纤锌矿结构, 并且大多沿[0001]方向择优取向生长, 直径为20～80 nm, 长度可从0.5至几微米. 提出了聚合物控制ZnO结晶和形貌的网络骨架限域模型以解释纳米线的生长行为.     

基于ZnO纳米线的螺旋线形跨尺度葡萄糖传感器

制备了一种基于螺旋线形跨尺度结构的酶传感器, 并对该传感器进行了表征和性能测试. 将ϕ 30 μm键合Au丝以螺旋线方式手工缠绕在ϕ 125 μm光纤纤芯上, 在该Au螺旋线上用水浴法合成ZnO纳米线, 得到螺旋线形跨尺度结构; 在ZnO纳米线上物理吸附葡萄糖氧化酶(GOD), 制备了葡萄糖传感器工作电极. 利用扫描电子显微镜(SEM)图像和MatLab图像处理算子分别对螺旋线形跨尺度结构表面形貌及其上活力为50 units/mg的GOD吸附效果进行了定性和定量表征, 分析了非高斯粗糙表面与GOD吸附效果的影响关系. 基于三电极体系采用循环伏安法和计时安培法测试了制备的12个工作电极的性能, 测得该类传感器的灵敏度为(1.410±0.665) μA·L/(mmol·cm²), 线性范围为0~(4.292±0.652) mmol/L, Michaelis-Menten常数为(3.571±1.280) mmol/L, 检出限为(14.085±8.393) μmol/L. 使用活力更高的GOD可以得到性能更好的螺旋线形跨尺度葡萄糖传感器. 该类传感器可广泛应用于医药、 生物、 食品加工及环境监测领域中尿酸、 尿素、 胆固醇、 过氧化氢和苯酚等的检测.     

表面形貌对螺旋线形跨尺度电化学葡萄糖传感器性能的影响

将键合金丝以螺旋方式紧密绕制在光纤纤芯上,用水浴法在其表面合成氧化锌纳米线,再将葡萄糖氧化酶物理吸附在纳米线上,得到了螺旋线形跨尺度葡萄糖酶电极。提取了该跨尺度结构及相应酶电极的表面形貌,表征了该批酶电极的电化学性能。结果表明,氧化锌纳米线的合成参数对跨尺度结构的表面形貌、葡萄糖氧化酶的固定效果、跨尺度电化学葡萄糖传感器的性能有显著影响;当生长液Zn2+浓度为25 mmol/L时,跨尺度结构表面形貌的粗糙度为0.10μm、相关长度0.29μm,此时葡萄糖氧化酶的固定效果最好,对应的葡萄糖传感器灵敏度为2.15μA/(mmol/L·cm2)、线性范围0~4.5 mmol/L、检出限9.2μmol/L、Michaelis-Menten常数3.68 mmol/L。研究结果不但有助于螺旋线形跨尺度酶电极的批量制备,还可显著提高其测量精度。     

三维分级结构ZnO的制备及光催化性能

以聚乙烯醇/醋酸锌复合纳米纤维为模板, 采用模板辅助共沉积技术制备了三维尖晶石型ZnO纳米线/纳米纤维分级结构, 并采用SEM, XRD对其形貌和晶型结构进行了表征. 在光催化降解乙醛性能实验中, 三维分级结构ZnO表现出比纳米粒子和纤维更好的光催化性能. 这主要归因于ZnO纳米线的次级结构和开放的三维网络结构更有利于乙醛分子和氧分子的扩散和传输, 从而提高了乙醛的光降解速率.     

Ag/ZnO/ZnSe三元异质结的合成及其可见光光催化性能

以Ag纳米线为模板,通过两步水浴法合成了Ag/ZnO/ZnSe三元异质结光催化材料。利用场发射扫描电子显微镜(FESEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)以及透射电子显微镜(FETEM)对样品的形貌和结构进行了表征。结果显示,Ag/ZnO/ZnSe三元异质结为蠕虫状的Ag/ZnO二元异质结外镶嵌着ZnSe小颗粒。在可见光下,对比纯Ag纳米线、纯ZnO纳米球、Ag/ZnO异质结对罗丹明B的可见光降解效率,结果发现Ag/ZnO/ZnSe异质结表现出了更高的光催化效率。其光催化性能的提高主要是由于Ag/ZnO/ZnSe异质结的作用促使电子空穴对的分离,降低了电子空穴对的复合机率,从而提高了材料的光催化效率。     

ZnO/PPy异质纳米复合材料的制备、表征及其气敏特性

室温下, 采用原位聚合法, 以吡咯(PY)为单体, 氯化铁(FeCl₃·6H₂O)为氧化剂, 在塑料基片上聚合生长了聚吡咯(PPy)纳米微球. 然后在聚吡咯基片上生长ZnO种子, 将表面种有ZnO种子的PPy元件置于六次甲基四胺与硝酸锌的混合溶液中, 90 ℃水浴中, 在PPy微球上生长了ZnO纳米棒, 合成了PPy/ZnO异质纳米复合材料. 分别通过X射线衍射仪(XRD)和场发射扫描电镜(FESEM)对PPy/ZnO异质纳米复合材料的结构和形貌进行了表征. 制备了塑料基的PPy/ZnO异质纳米复合材料气体传感器, 在室温下, 对10×10^-6-150×10^-6 (体积分数)浓度范围的氨气进行了气敏测试, PPy/ZnO气敏元件对氨气响应的灵敏度基本呈线性关系, 且对甲醇、丙酮、甲苯等有机气体表现出很好的选择性. 最后, 对PPy/ZnO异质纳米复合材料的形成机理进行了简要分析.     

具有核壳结构的ZnO纳米棒@Ni-Co双氢氧化物复合物纳米片阵列的制备及其电化学性能

通过两步水热合成法制备了具有核壳结构的ZnO纳米棒@Ni-Co双氢氧化物复合材料纳米片阵列.首先,以碳布为基底,水热法生成的ZnO沉积在碳布上形成ZnO纳米棒花簇.其次,以ZnO纳米棒为模板,水热法生成的Ni-Co双氢氧化物纳米片沉积在ZnO纳米棒表面,形成ZnO纳米棒@Ni-Co双氢氧化物纳米片复合材料阵列.形貌、结构分析和电化学性能测试表明,以碳布为基底,成功地合成了以ZnO纳米棒为模板并具有核壳结构的ZnO纳米棒@Ni-Co双氢氧化物复合材料纳米片阵列,该复合材料纳米片阵列具有较大的纵横比,且分散均匀.合成的ZnO纳米棒@Ni-Co双氢氧化物复合材料纳米片阵列具有良好的电化学性能,当电流密度为1 A/g时,其比电容值可达531.6 F/g,该复合材料在超级电容器电极材料领域具有良好的应用前景.     

ZnO纳米线/棒阵列的水热法制备及应用研究进展

氧化锌(ZnO)纳米线/棒阵列的质量决定了所构建光电器件的性能. 为了制备出比表面积更大、垂直性更好以及无根部融合的高质量ZnO纳米线/棒阵列, 本文概述了近几年两步水热法可控制备ZnO纳米线/棒阵列的研究进展, 分别探讨了种子层、生长液和生长方法对纳米线/棒阵列形貌的影响, 详细分析了氨水、六次甲基四胺和聚乙烯亚胺对于促进纳米线/棒阵列生长的作用机理, 提出了通过微流控技术可控制备ZnO纳米线阵列提高纳米线生长效率的方法. 最后介绍了ZnO纳米线/棒阵列的形貌对于提高染料敏化太阳能电池、纳米发电机、气体传感器和场发射器件性能的重要作用, 并对未来两步水热法制备ZnO纳米线/棒阵列的发展趋势进行了展望.     

Cu2O/ZnO的形貌可控制备及光催化性能

以CuSO₄和ZnCl₂为原料, 采用温和的液相还原法制备得到Cu₂O/ZnO微米结构高效光催化剂. 研究了不同[Cu²⁺]/[Zn²⁺]比条件下所得Cu₂O/ZnO复合物的形貌和光催化活性. 通过5.5 h的光照, Cu₂O/ZnO光催化剂对甲基橙染料的降解率为(77.5±0.1)%. 将多形貌Cu₂O/ZnO复合物作为阳极, 铂片作为对电极, 中间注入甲基橙溶液, 组装“三明治”结构拟电池, 研究了复合物的光降解机制.     

酸碱度调控氧化锌纳米材料形貌及其光催化还原CO2研究

利用水热法合成了形貌可控的氧化锌(ZnO)微纳材料。利用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),紫外-可见(UV-Vis)分光光谱和比表面积分析(BET)等技术对所制备的ZnO材料进行了表征。不同酸碱度(pH值)条件下,经过500 ℃退火2 h制备的ZnO均为纤锌矿结构。随着前驱液pH值的增加,所得ZnO从片状晶体变为棒状晶体。片状ZnO主要暴露极性晶面,棒状ZnO主要暴露非极性晶面。从生长角度考虑,在溶液为弱酸性条件下(pH 6.5),溶液中游离的氯离子(Cl^-)抑制了ZnO在锌极性面({Zn²⁺}_{crystal surface})的生长,水热反应产物为片状Zn₅(OH)₈Cl₂·H₂O,退火后得到微孔片状ZnO;当溶液中添加氢氧根(OH^-)后,锌离子(Zn²⁺)被络合为四羟基锌络合离子(Zn(OH)₄^2-),该络离子促进了ZnO在{Zn²⁺}_{crystal surface}的生长,从而得到棒状晶体。利用上述催化剂,在氙灯照射下进行光催化还原二氧化碳实验,发现极性面较多的片状ZnO具有更高的光催化性能。     

Synthesis of variable-aspect-ratio, single-crystalline ZnO nanostructures

Variable-aspect-ratio (length/diameter), one-dimensional (1-D) ZnO nanostructures (nanorods and nanowires) were prepared in alcohol/water solution by reacting a Zn2+ precursor with an organic weak base, tetramethylammonium hydroxide (Me4NOH). The effect of the experimental parameters (temperature, base concentration, reaction time, and water content) on nucleation, growth, and the final morphology of the ZnO nanostructures was investigated. The low-temperature syntheses (75-150 degrees C) yielded aspect ratios of the 1-D ZnO nanostructures that depended on the water content. The individual ZnO nanorods and nanowires were determined to be perfect, single crystals with their c axes as the primary growth direction.     

Preparation of ZnO Nanowires and Study of Surface‐adsorbate Interaction by Fourier‐Transform Infrared Spectroscopy

To study the surface‐adsorbate properties of ZnO nanowires, a hydrothermal method was modified to grow ZnO nanowires directly on ZnSe, which were then characterized by attenuated total reflection infrared (ATR‐IR) spectroscopy. To prepare ZnO nanowires directly on ATR sensing element of ZnSe, ZnO seed layers were first formed by annealing of ZnO seeds on ZnSe surfaces. The ZnO seed layers then were exposed to growth solution, forming ZnO nanowires directly on the ATR crystals. The interaction properties of the resulting surfaces were studied by an ATR‐IR method. The diameter, length and distribution of the ZnO nanowires can be tuned by adjusting the growth conditions, particularly the growing time and the concentrations of reagents. Two surfaces, namely Zn‐rich and Zn‐O ion‐pair surfaces were studied in detail for their adsorption properties toward compounds bearing different functional groups. By examination of several volatile organic compounds (VOCs), it was found that the Zn‐rich surface is less selective and interacts with compounds bearing the functional groups of amino and hydroxyl. The Zn‐O ion‐pair surface is more selective and a much stronger interaction was observed with non‐aromatic amino compounds. These results indicate that the improving of the selectivity of a ZnO‐based sensing device can be achieved by tuning the surface structure of the ZnO nanomaterials.     

Synthesis and characterization of ZnO nanowires by thermal oxidation of Zn thin films at various temperatures

In this research high-quality zinc oxide (ZnO) nanowires have been synthesized by thermal oxidation of metallic Zn thin films. Metallic Zn films with thicknesses of 250 nm have been deposited on a glass substrate by the PVD technique. The deposited zinc thin films were oxidized in air at various temperatures ranging between 450 °C to 650 °C. Surface morphology, structural and optical properties of the ZnO nanowires were examined by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and photoluminescence (PL) measurements. XRD analysis demonstrated that the ZnO nanowires has a wurtzite structure with orientation of (002), and the nanowires prepared at 600 °C has a better crystalline quality than samples prepared at other temperatures. SEM results indicate that by increasing the oxidation temperature, the dimensions of the ZnO nanowires increase. The optimum temperature for synthesizing high density, ZnO nanowires was determined to be 600 °C. EDX results revealed that only Zn and O are present in the samples, indicating a pure ZnO composition. The PL spectra of as-synthesized nanowires exhibited a strong UV emission and a relatively weak green emission.     

Controlled growth of semiconducting oxides hierarchical nanostructures

Semiconducting ZnO hierarchical nanostructure, where ZnO nanonails were grown on ZnO nanowires, has been fabricated under control experiment with a mixture of ZnO nanopowders and Sn metal powders. Sn nanoparticles are located at or close to the tips of the nanowires and the growth branches, serving as the catalyst for the vapor-liquid-solid growth mechanism. The morphology and microstructure of ZnO nanowire and nanonail were measured by scanning electron microscopy and high-resolution transmission electron microscopy. The long and straight ZnO nanowires grow along [0001] direction. ZnO nanonails are aligned radially with respect to the surface the ZnO nanowire. The long axis direction of nanonails forms an angle of ∼30° to the [0001] direction.     

Zn2+ release from zinc and zinc oxide particles in simulated uterine solution

Zn²⁺ release from Zn and ZnO particles with different sizes in simulated uterine solution were investigated by absorbance measurements. The effects of pH and human serum albumin (HSA) on Zn²⁺ release were also studied. The morphology of Zn and ZnO particles was observed by scanning electron microscopy, and the corrosion products of zinc nanoparticles were analyzed by XRD. The results indicate that the maximum release ratios of Zn²⁺ from Zn and ZnO nanoparticles are higher than those from Zn and ZnO microparticles. Zn²⁺ release ratio depends not only on the pH of the simulated uterine solution but also the presence of human serum albumin. It decreases as the pH of the uterine solution increases. The trends of Zn²⁺ release ratios are almost the opposite for solutions with and without HSA. XRD analysis results indicate that zinc oxide is the main corrosion product of zinc particles.     

聚合物基ZnO纳米线的制备和生长机理研究

采用独特的高分子溶液自组装生长方法, 在经化学镀预处理的基底上利用高分子溶液的网络络合效应制备了ZnO纳米线. 通过场发射扫描电子显微镜(FE-SEM), X射线能谱仪(EDS)等对样品的表面形貌及组成进行了观测表征. 结果显示, 纳米线直径约50 nm, 长度达到了数微米; 产物Zn、O化学计量比接近1∶1. 通过Si基底经化学镀工艺预处理和未经化学镀预处理对ZnO纳米结构、紫外吸收和PL性能影响的分析比较, 发现了化学镀Ni对于纳米线长度和直径尺寸的控制更为有效; 在PL图谱中, 经化学镀预处理的样品在中心波长385 nm出现了由激子碰撞复合所形成的近紫外发光峰. 进一步还分析了在不同的pH值和反应时间下样品的紫外吸收和光致发光性能. 通过以上实验, 讨论并提出了ZnO纳米线的生长机理及过程, 认为纳米线的生长是在化学镀催化剂和高分子双重作用下进行的.     

Synthesis and Characterization of ZnO Nanowires

Zinc oxide is a wide bandgap (3.37 eV) semiconductor with a hexagonal wurtzite crystal structure. ZnO prepared in nanowire form may be used as a nanosized ultraviolet light-emitting source. In this study, ZnO nanowires were prepared by vapor-phase transport of Zn vapor onto gold-coated silicon substrates in a tube furnace heated to 900 ?C. Gold serves as a catalyst to capture Zn vapor during nanowire growth. Size control of ZnO nanowires has been achieved by varying the gold film thickness…     

Molten salt route toward the growth of ZnO nanowires in unusual growth directions

ZnO nanowires with unusual growth directions, such as the approximate 102 and the 100 directions, were prepared by using the LiCl molten salt synthetic method. Intrinsic crystallographic structures and the growth directions of the as-prepared ZnO nanowires were investigated by using selected area electron diffraction and high-resolution transmission electron microscopy. In the present case, Li+ and Cl- ions of molten salts may bind with O2- and Zn2+ ions, respectively, of the {101} and {001} polar surfaces of the ZnO crystals, resulting in the decrease of their surface energies and tuning the growth directions by blocking the growth on the polar surfaces. A combination of the growth along the <102>, <100>, and <210> directions may lead to the formation of complex tree like ZnO dendrites. Strong green light emission was observed from room-temperature PL spectra of the as-prepared ZnO nanowires. This molten-salt synthetic process could be extended to synthesize other kinds of unusual 1D nanomaterials with specific crystal structures and properties.