一维有序ZnO纳米棒阵列的制备与表征

通过改进传统水热法的密闭、高压的条件,在非密闭、常压环境下在氧化铟锡玻璃衬底上自组装生长了取向高度一致并且分散性好的ZnO纳米棒阵列.首先将乙酸锌溶胶旋涂到氧化铟锡玻璃衬底上,经热处理得到致密的ZnO纳米晶薄膜,然后将其垂直放入前驱体溶液中通过化学溶液沉积生长得到ZnO纳米棒阵列.室温条件下,对样品进行了SEM和XRD的测试.表明生成的氧化锌纳米棒阵列沿c轴取向,实现了定向生长,且纳米棒结晶较好,为六方纤锌矿结构,直径约为40 nm,长度达到微米量级.室温下的吸收光谱表明,由此方法得到的纳米棒纯度较高,有强的紫外吸收.室温下,观测到了该有序ZnO纳米棒阵列在387 nm处强的窄带紫外发射,半高宽小于30 nm,在468 nm处还有一强度较弱的蓝光发射峰.     

氧化锌叶片状纳米晶的结构和光谱特性

熔盐法对sol-gel法生成的前驱物处理合成新颖的叶片状的氧化锌纳米结构,TEM照片显示其长度300-500nm,宽度为50-80nm,两头尖端约呈25°夹角,形状基本沿中轴呈中心对称。其生长过程进行了研究:弯曲了的ZnO纳米棒闭合形成框架结构,框架内沿中轴方向并排生长的ZnO纳米线填满框架内的空隙形成叶片状的氧化锌纳米结构。Raman谱测量发现该结构是晶化的六角相氧化锌。对叶片状的氧化锌的声子限制效应进行了研究,并与纳米颗粒氧化锌予以比较。435cm-1的E2峰的Fano不对称具有正的Fano耦合系数。发现在585nm处出现光致发光峰,归于ZnO纳米结构中氧缺陷的作用。     

煅烧温度对Cu掺杂ZnO纳米粉体的制备及发光性能的影响

在PVA溶液中制备ZnO∶Cu纳米粉体的前驱体,经过煅烧获得ZnO∶Cu纳米粉体,考察煅烧温度对制备过程及发光性能的影响。利用XRD、TEM分析了产物的结构和形貌,XRD分析结果表明,当煅烧温度高于500℃时,可以使PVA完全分解,制备出具有六角纤锌矿结构的ZnO∶Cu粉体。TEM结果表明,粉体呈球形,大小均匀,分散性好,平均粒径为20～25 nm。在342 nm波长光的激发下,在ZnO∶Cu的室温PL光谱中可以观察到两个中心波长位于458 nm和486 nm的较强的蓝光发射峰,经400℃煅烧处理的ZnO∶Cu纳米粉体的蓝光发射最强。煅烧后的ZnO∶Cu只有微弱的绿光发射(510～530 nm),Cu的掺杂使ZnO的绿光发射变为蓝光发射。蓝紫光的发射波长随煅烧温度的升高产生明显的红移,由300℃时的404 nm红移至600℃时的422nm,发射强度随温度升高先增大后减小。     

氧化锌纳米晶体的光谱分析

采用沉淀法并通过控制前驱体的煅烧温度来制备粒径不同的氧化锌(ZnO)纳米晶体,对粒子的透射电镜照片进行分析,结果表明,制备出的纳米粒子分散性好、形貌一致、粒径分布集中。样品的X射线衍射光谱分析表明,随着前驱体煅烧温度增加,晶体粒径增大、结晶度提高;样品的紫外-可见吸收光谱的峰位随粒径减小而发生蓝移,这一实验结果表明ZnO纳米晶体呈现出较明显的量子限域效应;红外吸收光谱测量结果表明,用沉淀法制备的ZnO纳米晶体的表面会吸附一小部分残余的离子,对红外吸收光谱中的ZnO特征振动峰随粒径减小发生宽化和红移的现象进行了理论分析;光致发光光谱测量结果表明,ZnO纳米晶体在紫外区(360 nm)存在一较弱的发光峰,而在可见区(468 nm)存在一较强的发光峰,与理论计算结果进行比较后,认为锌空位点缺陷是导致ZnO纳米晶体可见区发光的主要原因。     

Co3O4纳米晶的制备和表征

发现了一种新制备Co3O4纳米晶的新方法。这种方法是先将高分子聚乙烯吡咯烷酮(PVP)和乙酸钴溶解到溶剂中缓慢蒸发溶剂,然后干燥形成的前驱体,最后在400℃温度下煅烧制备了Co3O4纳米晶。生成的产物用XRD,SEM,TEM等测试方法进行了表征。结果发现在不同的溶剂中形成前驱体所制备的Co3O4纳米晶具有不同的形貌特征,使用乙醇溶剂时生成了大量的由Co3O4纳米晶自组装形成的Co3O4微米球;而使用水溶剂时则生成的全都是Co3O4纳米晶。实验结果表明在不同溶剂中形成的前驱体对于最终制备的Co3O4纳米晶形态有着很大的影响。     

醋酸锌热解温度对ZnO纳米棒的结构及光学性质的影响

采用水热法在普通载玻片上热解醋酸锌生成的ZnO种子层上制备ZnO纳米棒, 采用 X射线衍射仪、扫描电镜、分光光度计等测试手段详细研究了醋酸锌热解温度对 ZnO纳米棒的结构和光学性质的影响. 结果表明: 纳米棒的结晶质量、端面尺寸、宏观应力和透射率与醋酸锌热解温度有密切关系. 随着热解温度的增加, ZnO纳米棒具有的c轴择优取向性先增强后减弱, 拉应力先减小后增大, 可见光区的平均透射率先增大后减小. 热解温度为350 ℃时, ZnO纳米棒c轴择优取向性最强, 拉应力最小, 平均透射率最大. 端面尺寸诱导的表面散射 是影响ZnO纳米棒可见光区平均透射率的主要机制. 关键词： 醋酸锌 水热法 ZnO纳米棒     

Cu掺杂ZnO纳米材料的制备及表征

利用CuO作为前驱体对ZnO进行了Cu掺杂研究,分别在不同温度下获得了ZnO纳米带及有纳米带构成的微米花状结构,对其生长机理进行了分析。并且以Cu片为衬底获得了ZnO的纳米梳以及有纳米梳构成的多层结构ZnO。XRD表明产物中只有ZnO单质相的存在,EDS证明产物中存在Cu元素。ZnO室温下的PL谱表明其UV与深能级发射强度比随Cu掺杂量的增加而变大,说明Cu的掺杂能够降低ZnO的缺陷峰强度。     

乙二醇溶剂中纳米氧化锌的制备

以乙二醇作为溶剂 ,氢氧化钠 (1mol· L-1)、氯化锌 (1mol· L-1)为原料 ,在非水体系中 ,15 0℃温度下化学沉淀法制备纳米级氧化锌粒子 ,反应时间为 2 h。用 XRD、FT- IR、TG- DTA、TEM表征粒子的结构和特征 ,德拜 -谢乐公式计算粒子的平均粒径。在实验条件下 ,前驱体生成与氧化锌粒子形成同步实现 ,粒子粒径为 2 0 nm左右 ,其表面被有机物包覆。     

水热法制备Co掺杂ZnO纳米棒及其光学性能

采用水热法在石英衬底上以Zn(CH3COO)2.2H2O和Co(NO3)2.6H2O水溶液为源溶液,以C6H12N4(HMT)溶液作为催化剂,在较低温度下制备了Co掺杂的ZnO纳米棒。采用X射线衍射(XRD)和扫描电子显微镜(SEM)对所生长ZnO纳米棒的晶体结构和表面形貌进行了表征,考察了Co掺杂对ZnO纳米棒微观结构和对发光性能影响的机制。结果表明:Co掺杂的ZnO纳米棒呈六方纤锌矿结构,具有沿(002)面择优生长特性,Co掺杂使ZnO纳米棒的直径变细;同时室温光致发光(PL)谱检测显示Co掺杂ZnO纳米棒具有很强的近带边紫外发光峰,而与深能级相关的缺陷发光峰则很弱。本研究采用水热法在石英衬底上于较低温度下生长出了具有较高光学质量的Co掺杂ZnO纳米棒。     

ZnO纳米棒的低温溶液法制备、光电特性研究及其在有机/无机复合电致发光中的应用

利用水热法制备了垂直于衬底的定向生长的ZnO纳米棒,利用扫描电子显微镜及光致发光的方法对其形貌及光学特性进行了表征,利用场发射性能测试装置对ZnO纳米棒的场发射性能进行了测试.结果表明:利用水热法在较低的温度(95 ℃) 下生长了具有较好形貌和结构的ZnO纳米棒,并表现出了较好的场发射特性,当电流密度为1 μA/cm²时,开启电场是2.8 V/μm,当电场为6.4 V/μm时,电流密度可以达到0.67 mA/cm²,场增强因子为3360.稳定性测试表明,在5 h内,4.5 V/μm的电场下,其波动不超过25%.将制备的ZnO纳米棒应用到有机/无机电致发光中,其中ZnO纳米棒为电子传输层,m-MTDATA(4,4',4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) 为空穴传输层,得到了ZnO的342 nm的紫外电致发光,此发光较ZnO纳米棒光致发光的紫外发射有约40 nm的蓝移. 关键词： ZnO纳米棒 场发射 水热法 有机/无机复合电致发光     

Growth of ZnO nanorods by aqueous solution method with electrodeposited ZnO seed layers

ZnO nanorod arrays on ZnO-coated seed layers were fabricated by aqueous solution method using zinc nitrate and hexamethylenetetramine at low temperature. The seed layers were coated on ITO substrates by electrochemical deposition technique, and their textures were dominated by controlling the deposition parameters, such as deposition potential and electrolyte concentration. The effects of the electrodeposited seed layers and the growing parameters on the structures and properties of ZnO nanorod arrays were primarily discussed. The orientation and morphology of both the seed layer and successive nanorods were analyzed by using X-ray diffraction (XRD), SEM and TEM. The results show that the seed layer deposited at −700 mV has evenly distributed crystallites and (0 0 2) preferred orientation; the density of resultant nanorods is high and ZnO nanorods stand completely perpendicular onto substrates. Meanwhile, the size of nanorods quite also depends on the growth solution, and the higher concentration of growth solution primary leads to a large diameter of the ZnO nanorods.     

Structural and optical properties of poly-vinylpyrrolidone modified ZnO nanorods synthesized through simple hydrothermal process

The synthesis of nanocrystalline zinc oxide (ZnO) in the presence of poly-vinylpyrrolidone (PVP) as capping agent through hydrothermal process, and their structural and optical properties were reported. PVP modified ZnO nanorods grown hydrothermally involve a heterogeneous chemical reaction in the presence of water as a solvent medium and reaction temperature of 100 °C for 7 h in a hot air oven and calcined in air at 500 °C for 3 h. Crystal structure, phase purity and average crystallite size of ZnO were studied by powder X-ray diffraction (PXRD). The strain associated with the as-prepared samples due to lattice deformation was estimated by Williamson–Hall (W–H) analysis. Structural morphology was investigated using scanning electron microscopy (SEM), which showed the formation of nanorods with PVP capping. The growth mechanism of ZnO nanorods and its capping by poly-vinylpyrrolidone are briefly discussed through FT-IR adsorption spectra. The optical behavior of the samples was analyzed through photoluminescence (PL) spectroscopy with an emission spectra in visible region ∼418 nm indicate the applicability of using it as a transport material in solar cells.     

硝酸铟诱导的电沉积氧化锌纳米柱光学性质裁剪

为在新型太阳能电池等光电器件中应用ZnO纳米结构,需要对ZnO纳米结构阵列的几何形貌及光电物理性质进行裁剪与操控。采用电化学沉积路线制备ZnO纳米柱阵列,In(NO3)3与NH4NO3两种盐类被溶入在传统Zn(NO3)2主电解液中。对ZnO纳米柱阵列进行扫描电子显微镜、透射反射光谱、光致发光光谱测试,分析其形貌与光电物理性质。随着引入的In(NO3)3浓度的增加,ZnO纳米柱阵列的平均直径随之由57 nm减小至30 nm。同时ZnO纳米柱的阵列密度也可降低,进而增大纳米柱间距至41 nm。由于新的盐类的引入,ZnO纳米柱的光学带隙由3.46 eV蓝移至3.55 eV。随着电解液中In(NO3)3的增加,ZnO纳米柱的斯托克斯位移由198 meV减小至154 meV,ZnO纳米柱中的非辐射复合可以得到一定程度的抑制。通过在主电解液中引入In(NO3)3与NH4NO3两种盐类,可对ZnO纳米柱的直径、密度、间距、透射反射率、光学带隙、近带边发射与非辐射复合进行操控与裁剪。     

Alignment-controlled hydrothermal growth of well-aligned ZnO nanorod arrays

ZnO nanorod arrays (ZNAs) were prepared via a two-step seeding and solution hydrothermal growth process. Effects of preparing parameters such as seed layer, colloid concentration, substrate and precursor concentration, on the alignment control of ZNAs were systematically investigated. The deviation angle of ZnO nanorods was measured to evaluate the alignment of arrays. Results show that seed layer not only controls the vertical orientation of ZNAs, but also the compactness of ZNAs. Altering colloid concentration and substrate can influence the microstructure of ZnO seed layer and affect the ordered alignment of ZNAs. The precursor concentration has an insignificant effect on the alignment of ZNAs but has great impact on the morphology of ZNAs. Alignment-controlled and well-aligned ZnO nanorods with different diameter and aspect ratio can be obtained by properly controlling the preparing parameters. A growth mechanism was proposed for the growth of ZnO nanorods.     

The study of low temperature hydrothermal growth of ZnO nanorods on stents and its applications of cell adhesion and viability

The hydrothermal growths of the ZnO nanorods with the densities ranging from 157 to 73 nanorods/μm² were achieved by diluting the ZnO seed solution. However, the ZnO seed nanocrystals started to agglomerate for the seed solution diluted below 1% of the original nano-crystalline solutions and resulted in the formation of clustered nanorods. With the assistance of a surfactant, Triton X-100, the nanorod density can be further reduced to 4 nanorods/μm². The diameters of the nanorods depended on the concentration of the seed solution and agitation speed of the nanorod growth solution. More diluted seed solution used and less agitation of the growth solution, the larger diameter of the nanorods was obtained. This indicated that the nanorod growth mechanism was controlled by the diffusion of reactants. With sufficient agitation of the growth solution, the nanorod can be uniformly grown with subjects on any arbitrary geometry. We have demonstrated ZnO nanorods growth on both inside and outside of biliary stents as well as on nitinol wires used as metal stents. The effect of nanorod density on the NIH 3T3 and HUVEC cells growth was also investigated in this study and the results suggested nanorod-coating to be a suitable method for controlling cell adhesion and viability on implantable devices.     

The growth mechanism of ZnO single-crystal nanorods synthesized by polymer complexing with zinc salts

The growth mechanism of single-crystal ZnO nanorods synthesized by the method of polymer complexing with zinc salts is investigated. The annealing temperature is controlled at about the decomposition temperature of dihydrate zinc acetate (Zn(O₂CCH₃)₂·2H₂O) of 573 K. By changing the annealing time, the ZnO nanostructures can be modified from nanoparticles to nanorods. As a result, the formation of single-crystal ZnO nanorods can be observed. Through investigating the Fourier transform infrared spectra of (a) polyvinyl pyrrolidone (PVP), (b) Zn(O₂CCH₃)₂·2H₂O and (c) the mixture of PVP and Zn(O₂CCH₃)₂(H₂O)₂, the interaction between PVP and Zn(O₂CCH₃)₂·2H₂O can be observed. PVP plays an important role in the growth of the single-crystal ZnO nanorods. We analyze the growth process of ZnO nanorods by observing their TEM images at different moments. Consequently, our results indicate that the single-crystal ZnO nanorods were formed by self-assembling the ZnO nanoparticles. PACS 61.46.Hk; 61.46.Df; 78.30.-j; 81.07.-b; 81.16.Be     

Low-temperature growth of ZnO nanorods on PET fabrics with two-step hydrothermal method

An effective low-temperature growth method to fabricate hexagonally oriented ZnO nanorod arrays onto PET fabrics is reported. The effect of substrate pre-treatment and C₆H₁₂N₄ concentration on the structure of ZnO nanorod arrays were investigated in details by X-ray diffraction (XRD), FE-SEM and ultraviolet protection factor (UPF). The results show that substrate pre-treatment, C₆H₁₂N₄ concentration indeed have great influence on the growth of ZnO nanorod arrays. It is indispensable to introduce a ZnO seed layer on the substrate and under growth condition of n(C₆H₁₂N₄):n[Zn(NO₃)₂] = 1:1, T = 90 °C, t = 3 h, the well-aligned ZnO nanorod arrays with 40-50 nm in diameter and 300-400 nm in length were achieved on the pre-treated PET fabrics. The ZnO nanorods grown on PET fabrics possessed an ultrahigh ultraviolet protection factor of 480.52 in this study, indicating an excellent protection against ultraviolet radiation in comparison with the untreated PET fabrics.     

Controllable growth of well-aligned ZnO nanorod arrays by low-temperature wet chemical bath deposition method

Well-aligned ZnO nanorod arrays were synthesized by low-temperature wet chemical bath deposition (CBD) method on Si substrate under different conditions. Results illustrated that dense ZnO nanorods with hexagonal wurtzite structure were vertically well-aligned and uniformly distributed on the substrate. The effects of precursor concentration, growth temperature and time on nanorods morphology were investigated systematically. The mechanism for the effect of preparation parameters was elucidated based on the chemical process of CBD and basic nucleation theory. It is demonstrated that the controllable growth of well-aligned ZnO nanorods can be realized by readily adjusting the preparation parameters. Strong near-band edge ultraviolet (UV) emission were observed in room temperature photoluminescence (PL) spectra for the samples prepared under optimized parameters, yet the usually observed defect related deep level emissions were nearly undetectable, indicating high optical quality ZnO nanorod arrays could be achieved via this easy process chemical approach at low temperature.     

聚乙烯亚胺对氧化锌纳米阵列形貌的影响

采用化学沉淀法,以硝酸锌和六次亚甲基四胺的水溶液为生长溶液,在涂覆氧化锌晶种层的玻璃衬底上制备了定向生长的氧化锌纳米棒阵列,并研究了添加剂聚乙烯亚胺的浓度对氧化锌纳米棒形貌和结构的影响。X射线衍射和场发射扫描电镜的结果表明,合成的氧化锌纳米棒阵列较为均匀致密,具有六方纤锌矿结构,且有沿(002)晶面择优生长的特性;随着聚乙烯亚胺浓度的增加,氧化锌纳米棒的直径减小,直径分布趋于均匀,且氧化锌纳米棒的形貌也从锥状转变为柱状结构;另外,聚乙烯亚胺的加入对氧化锌的生长速度具有抑制作用,当聚乙烯亚胺的浓度增加至0.012 mol·L-1时,无氧化锌阵列生长。对氧化锌纳米棒阵列进行了拉曼光谱表征,结果表明,随着溶液中聚乙烯亚胺浓度的增加,氧化锌纳米棒的氧空位缺陷减少。最后,对聚乙烯亚胺浓度对氧化锌纳米阵列影响的机理进行了探讨。