一种P掺杂ZnO纳米梳的制备及其光致发光性能研究

采用化学气相沉积(CVD)方法制备了P掺杂ZnO纳米梳,扫描电子显微镜(SEM)结果显示,纳米梳状产物均匀分布在Si衬底上。P掺杂ZnO纳米梳为高度结晶的六方纤锌矿结构,ZnO中P的掺杂含量约为2%(原子分数)。室温光致发光(PL)光谱表明,P掺杂ZnO纳米梳在样品不同区域的发光性能略有不同,但是均出现3个发光峰:紫外、绿光和近红外发光峰。同时PL结果也表明样品的整体结晶质量比较好。     

梳状氧化锌纳米材料的制备及结构、性能的表征

通过纯锌粉蒸发，在600-650℃无催化条件下成功制备了高质量的梳状ZnO纳米结构。通过扫描电镜（SEM）及高分辨透射电镜（HRTEM）观察，所制备的梳状ZnO纳米结构具有两种典型形貌，且皆为单晶结构，分析表明其生长由气-固生长机理控制。室温光致发光谱显示，梳状ZnO纳米结构在385nm附近形成紫外发射峰；在以495nm为中心的范围内，形成较宽的绿光发射峰。     

ZnO一维纳米材料的制备与表征

首先以乙醇为溶剂,乙酸锌为前驱体,油酸钠为表面修饰剂,采用溶液化学法,制得ZnO纳米粒子。以自制ZnO纳米粒子为基体,通过煅烧方法制备针状ZnO纳米线束。通过紫外-可见吸收光谱(UVVis)、荧光光谱(FL)、透射电子显微镜(TEM)、X射线衍射(XRD)和扫描电子显微镜(SEM)等方法对合成的样品进行表征。结果表明,所合成ZnO纳米粒子样品UV-Vis吸收光谱在355nm给出ZnO纳米粒子的特征吸收峰,FL光谱显示在400和550nm处产生荧光发射。ZnO纳米粒子尺寸约为5nm且粒径分布较窄。自制ZnO纳米粒子样品经500℃煅烧后可得到针状ZnO纳米线束。纳米线为六方晶系纤锌矿结构ZnO单晶纳米线,长度约为10μm,直径约为100nm,长径比约为100,且具有良好的紫外发光性能。     

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.     

纳米木质素诱导制备金盏花状纳米ZnO及光催化性能

以纳米木质素为形貌诱导剂,以硝酸锌和氨水为原料,采用水热合成法制备金盏花状的纳米ZnO。通过X射线衍射(XRD)和扫描电子显微镜(SEM)对样品的结晶特性及形貌进行了表征分析,并对其光催化性能进行了测定。研究结果表明,纳米木质素能诱导纳米ZnO在其表面沉积和生长,形成晶粒大小为42.3nm的金盏花状结构,该金盏花状纳米ZnO室温下2.5h内对孔雀石绿的紫外光降解效率为91.3%。     

简单水热法制备棒状纳米氧化锌及其表征

以Zn(NO3)2和NaOH为原料,在不使用任何添加剂的条件下,采用水热合成法在不同的合成时间和合成温度下制备棒状纳米ZnO颗粒。通过X射线衍射(XRD)、透射电镜(TEM)、光致发光谱(PL)、电导率测试对样品进行表征。结果表明,所制备的纳米ZnO粉末具有六方红锌矿结构并沿(101)面择优生长;随着合成时间和温度的增加,样品的纯度逐渐增加;合成时间为25h,温度为200℃时,样品的结晶最好,样品基本成棒状,平均直径约为30～40nm,长度约为300～400nm、电阻率最大,且在376nm和500～600nm处有明显发射现象。深入分析了上述结果的形成原因。     

BSCCO超导体中均匀排布ZnO缺陷的纳米复合制备

通过纳米复合掺杂的方法,在BSCCO超导体中引入了均匀排布的纳米ZnO缺陷.研究并比较了不同掺杂方法对超导体性能以及ZnO在超导体中分布状态的影响.测试结果表明,不同掺杂方法所制备的样品均有明显的超导现象;经HRSEM表征,纳米复合掺杂所得样品中ZnO缺陷呈线状均匀排布,粒径约为100 nm.     

ZnO/Zn2SnO4纳米电缆结构表征与发光特性

ZnO、Zn2SnO4均为直接带隙宽禁带氧化物半导体,是优异的功能材料.以ZnO、SnO2为原料,通过共热蒸发法,合成了ZnO/Zn2SnO4纳米电缆结构.该纳米电缆结构为以ZnO为芯,Zn2SnO4为鞘,直径为50~100nm,长度可达上百微米.通过TEM分析手段,发现该纳米电缆结构中,ZnO的生长方向为<0001>方向,ZnO芯与Zn2SnO4鞘之间形成晶格外延关系.室温下光致发光谱结果显示,该纳米电缆结构在紫外区域(380.58nm附近处)存在很强的带边发光,而在可见光区域没有明显的发光带,这一结果表明:Zn2SnO4鞘层的存在能有效抑制ZnO表面的缺陷发光.ZnO/Zn2SnO4纳米电缆结构可以抑制电子-空穴的复合,在染料敏化太阳能电池等方面有一定的应用潜力.     

ZnO纳米棒阵列、纳米片及其发光和光催化特性

首先通过溶胶-凝胶法在Si片基底上制备1层ZnO纳米薄膜,作为纳米棒的晶种层,然后利用金属浴沉积法在ZnO纳米薄膜基础上制备择优取向的ZnO纳米棒阵列,最后通过水热法二次成核结晶形成纳米片。研究证明,ZnO纳米棒阵列和纳米片均沿着c轴取向。在Cu2+抑制极性面生长的作用下,形成的ZnO纳米片结构均匀,分布面积广,单片ZnO纳米片的厚度约为8 nm,面积呈平方微米级,较大的有40μm2左右。ZnO纳米结构的生长取向对其物理化学性能具有重要影响。高度沿c轴取向的ZnO纳米棒有利于紫外光发射和激光器的发展,但极性面的缩小不利于光催化反应。     

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准一维纳米结构生长形态的演化机理

利用气相生长系统,通过调控实验参数,制备了多种形貌的ZnO准一维结构,如纳米条带、[011-0]和[21-1-0]取向的单侧生齿的梳状纳米条带、微米尺度的梳状结构,由多节状六角棱柱和八角棱柱组装成的微米条带等.通过X射线衍射、扫描电子显微镜及其所加载的能谱分析和背散射电子衍射仪、高分辨透射电子显微镜等分析技术, 对其中具有代表性的介观结构进行了系统的形貌分析和细致的结构解析.分析出基本的结构单元及其复合体, 揭示了显微尺度下ZnO晶体的外形多样性以及其形态演化中的关联和规律,即ZnO纳米条带、梳状结构和多节状微米条带具有晶体结构上的同一性.     

Stacking fault directed growth of thin ZnO nanobelt

Thin ZnO nanobelts with an average width of 7.5 nm have been synthesized using vapor-phase transport method. It was found that stacking faults directed the growth of the thin nanobelts along the <01 1¯0> direction with {2¯ 1¯10} top/bottom surfaces and {0001} side surfaces. The {0002} stacking fault with translation of 1/3<01 1¯0> extends throughout the entire length of the ZnO nanobelts. The growth steps at the {01 1¯0} growth fronts resulted from the {0002} stacking fault are believed to direct fast axial growth of the thin ZnO nanobelts. The thin ZnO nanobelts are expected to be promising candidates for highly sensitive chemical and biological sensor applications.     

Preparation of high purity ZnO nanobelts by thermal evaporation of ZnS

High purity one-dimensional ZnO nanobelts were synthesized by thermally evaporating commercial ZnS powders in a hydrogen-oxygen mixture gas at 1050 degrees C. It was found that these ZnO nanobelts had a single crystal hexagonal wurtzite structure growing along the [0001] direction. They had a rectangle-shaped cross-section with typical widths of 20 to 100 nanometers and lengths of up to hundreds of micrometers with lattice constants of a = 0.325 nm and c = 0.520 nm. The self-catalytic hydrogen-oxygen assisted growth of ZnO nanobelt is discussed. The photoluminescence (PL) characterization of the ZnO nanobelts shows strong near-band UV emission (about 383 nm) and one broad peak at 501 nm, which indicates that the ZnO nanobelts have good potential application in optoelectronic devices.     

Twinning-induced ZnO bicrystalline nanobelts

ZnO bicrystalline nanobelts induced by three types of twinning have been synthesized by thermal evaporation method. The morphology and microstructure of the ZnO bicrystalline nanobelts have been studied by means of scanning electron microscopy, transmission electron microscopy and high resolution electron microscopy. <21­1­3>/{2­112} twinning-induced ZnO bicrystalline nanobelts are dominant in the product. ZnO bicrystalline nanobelts induced by <011­1­>/{011­2} and <033­2­>/{011­3} twinnings take up low fraction of the product. High oxygen partial pressure favors formation of the ZnO bicrystalline nanobelts.     

化学溶液法外延组装ZnO分级纳米结构

采用气相法、液相法相结合的方法外延组装了一种形貌新颖的复杂ZnO分级纳米结构--"纳米毛刷".首先用热蒸发的方法制备了宽面为极性面的ZnO纳米带,然后采用化学溶液法,在强碱溶液中在ZnO纳米带的极性面上外延生长Zno纳米棒阵列,实现了ZnO分级纳米结构"由下而上"地外延组装.采用负离子配位多面体生长基元模型讨论了ZnO分级纳米结构的外延组装机理.这种ZnO分级结构的实现,可望作为ZnO纳米器件的原型材料构建新型光电器件.     

Morphology, structures and properties of ZnO nanobelts fabricated by Zn-powder evaporation without catalyst at lower temperature

Uniform ZnO normal nanobelts and toothed-nanobelts have been successfully synthesized respectively through pure zinc powder evaporation without catalyst at 600°C. Experimental results indicate that the key to the fabricating method is to control the gas flow rates and the partial pressures of argon, oxygen and zinc vapor. Scanning electron microscopy and high-resolution transmission electron microscopy observations show that the ZnO nanobelts have several types of single crystalline morphology. HRTEM images reveal that there are numerous screw dislocations and the growth is around the dislocations in the toothed-nanobelts. The growth of ZnO nanobelts is controlled by vapor-solid and screw dislocation mechanisms. Room temperature photoluminescence spectra of the toothed-nanobelts showed a UV emission at ∼390 nm and a broad green emission with 4 subordinate peaks at 455–495 nm.     

Field emission from zinc oxide nanostructures and its degradation

Arrays of zinc oxide (ZnO) nanowires and nanobelts were synthesized by the thermal evaporation of mixed powders of ZnO and graphite. Neither catalyst nor vacuum environment was involved in the fabrication. For comparison, the ZnO nanowires were grown on a pre-deposited transitional ZnO film on a brass substrate and the ZnO nanobelts were grown directly on a Si substrate. Their field emission properties were systematically measured. Current density of 10 μA/cm² was achieved at the fields of 5.7 and 6.2 V/μm from the nanowires and nanobelts, respectively. Also, the emission sites were found to distribute uniformly on the whole cathode. In the preliminary test on the stability, the ZnO nanobelts, which were sharp at the tip but wide at the root, exhibited better robustness than the ZnO nanowires. The post-test scanning electron microscopy (SEM) observation showed that the degradation of their field emission capability resulted from the breaking of the nanowires, which was tentatively attributed to the resistive heating during the field emission. In contrast, the shedding of the ZnO from the substrate was not so serious as imagined.     

Necktie-like ZnO nanobelts grown by a self-catalytic VLS process

ZnO nanobelts with triangular top/bottom surfaces (so-called necktie-like nanobelts) are synthesized by a vapor transport deposition method. Scanning electron microscopy observations show that the ZnO nanobelts have a necktie-like morphology and are capped by particles. Transmission electron microscopy examinations indicate that the nanobelts have top and bottom surfaces of ± (11–20), and grow along [1–100]. The particles adhered at tips of the nanobelts are proved to be ZnO. On the basis of SEM and TEM observations, it is believed that the growth of the necktie-like ZnO nanobelts is a VLS process catalyzed by Zn droplets, i.e. a self-catalytic VLS growth. The result reported here is new evidence for such a mechanism.     

Synthesis of hierarchical ZnO nanobelts via Zn(OH)F intermediate using ionic liquid-assistant microwave irradiation method

ZnOHF nanobelts (NBs) were synthesized under microwave irradiation in the presence of ionic liquid, 1,2,3-trimethyl-imidazole tetrafluoroborate. The ranges of width, length and thickness of the NBs are ca. 500-800 nm, several micrometers and 100 nm, respectively. Porous polycrystal ZnO NBs with hierarchical structure were obtained after careful heat treatment of the intermediate ZnOHF at 400 °C for 2 h. The structural characters of the ZnO NBs were investigated by XRD, SEM, TEM, HRTEM and XPS measurements, and their absorption and photoluminescence properties were studied as well. The characterization results support the proposed reaction mechanism that the hierarchical ZnO NBs were produced via ZnOHF intermediate and subsequent removal of one of its decomposition products, ZnF₂, by hot water. This may be a facile method to fabricate porous ZnO NBs with hierarchical structure.