导电纳米氧化锌颗粒的制备与表征

氧化锌由于氧空位等本征缺陷的存在表现出n型半导体的性质，该性质使得氧化锌纳米颗粒可以用作导电材料。为了提高纳米氧化锌颗粒的电导率，通过简单、经济、新颖的液相反应法和喷雾热解技术对纳米氧化锌进行Al掺杂，并分析了掺杂工艺、电导测试方法对纳米氧化锌导电颗粒电阻率的影响。     

纳米ZnO晶体的制备及其荧光性能研究

采用直接沉淀法，通过改变沉淀剂（氨水、NaOH）及反应时间制备纳米ZnO粒子，并通过扫描电子显微镜、荧光显微镜对所得产物的形貌及其荧光性能进行分析表征。结果显示：不同沉淀剂制备的ZnO纳米粒子的形貌和尺寸均不相同，用Zn（NO3）2和NH3．H2O反应可制得花状的纳米粒子，而用Zn（NO3）2和NaOH反应则会生成球状的纳米粒子，其尺寸分别为500和200nm左右；反应前期，反应时间主要影响粒子的尺寸，随反应时间的增加粒子的形貌也发生变化；与以NaOH为沉淀剂制备的纳米ZnO粒子相比，以氨水为沉淀剂制备的纳米ZnO粒子具有好的荧光性能。     

A study of ZnO nanoparticles and ZnO-EG nanofluid

This study deals with the synthesis and characterisation of ZnO nanoparticles and suspension of ZnO-ethylene glycol (EG) nanofluid. Crystalline ZnO nanoparticles are synthesised using the chemical method. The nanofluids were synthesised by the dispersion of ZnO nanoparticles in EG solution using an ultrasonicator. The prepared ZnO nanoparticles are characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and UV-Vis absorption spectrum. The particle size distribution and ultrasonic parameters of the synthesised nanofluid are measured with the help of acoustic particle sizer (APS-100) and ultrasonic interferometer. The observed features of ZnO nanoparticles and ZnO-EG nanofluids are discussed in correlation with known properties of other nanofluids.     

纳米ZnO的沉淀法制备、表征及影响因素分析

用Zn(NO₃)₂·6H₂O对作原料、Na₂CO₃作沉淀剂,制得了纳米ZnO粉体.用TG-DSC、XRD和TEM分别对前驱体和纳米ZnO粉体进行了表征.结果表明:所得前驱体在253℃左右分解为六方纤锌矿型纳米ZnO,颗粒大小约为15～20nm,粒径分布窄,基本无团聚,粉体的比表面积为64.12m²·g^-1实验发现,当反应物浓度从2.0mol·L^-1减小至1.0、0.5mol·L^-1时,纳米ZnO粉体的粒径基本无变化,但颗粒间的团聚状态减轻;在用无水乙醇洗涤沉淀前,先用蒸馏水或稀氨水清洗对得到的纳米ZnO粉体的团聚状态没有明显的区别.     

Small angle neutron scattering and photoluminescence property of wet chemistry process synthesised ZnO nanoparticles

We report the synthesis of zinc oxide (ZnO) nanoparticles from aqueous solution at 25°C and subsequent heating of the solution at 115°C by the suitable selection of the solution chemistry and the control of the alkaline conditions. The structure of the synthesised ZnO particles was studied by X-ray diffraction (XRD), confirming the formation of Wurtzite structure. The optical property of synthesised ZnO nanoparticles is investigated through room temperature photoluminescence (PL) measurement. The PL of ZnO nanoparticles shows a strong UV emission band at approximately 385 nm, a blue–green band at approximately 473 nm and a very weak green band at approximately 554 nm, although polydispersity of the sample shows no presence on the PL spectrum. Small angle neutron scattering is used to determine the size and the size distribution of ZnO nanoparticles. The SANS data analysis and model fitting predict the size as about 18–20 nm, which is closely matched with XRD and transmission electron microscopy results with Gaussian distribution.     

沉淀法制备ZnO超细粉及其对乙醇气敏性研究

利用直接沉淀法制备ZnO超细粉 ,通过改变沉淀剂类型、浓度、煅烧温度等条件选择制备ZnO超细粉的最佳工艺条件。利用激光散射测定其粒径。利用X 射线衍射对ZnO超细粉进行分析 ,并对ZnO超细粉的气敏性进行研究。     

Fabrication of ZnO nanorods using metal nanoparticles as growth nuclei

ZnO nanorods were produced by pulsed laser deposition (PLD). Drops of nanoparticle colloid (gold or silver) were placed on silica substrates to form growth nuclei. All nanoparticles were monocrystalline, with well-defined crystal surfaces and a negative electrical charge. The ZnO nanorods were produced in an off-axis PLD configuration at oxygen pressure of 5 Pa. The growth of the nanorods started from the nanoparticles in different directions, as one nanoparticle could become a nucleus for more than one nanorod. The low substrate temperature used indicates the absence of a catalyst during the growth of the nanorods. The diameters of the fabricated 1-D ZnO nanostructures were in the range of 50-120 nm and their length was determined by the deposition time.     

Synthesis of ZnO nanoparticles and study of their antibacterial and antifungal properties

In this paper, ZnO nanoparticles have been synthesized with and without the use of surfactants under different reaction conditions. The size of the ZnO nanoparticles varied in diameter (2 nm-28 nm) according to the reaction conditions employed. Promising particle size dependent antibacterial and antifungal activities of the ZnO nanoparticles have been observed. Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Infrared spectroscopy (FTIR) techniques were used to characterize the particle size and morphology.     

Shed light on submerged DC arc discharge synthesis of low band gap gray Zn/ZnO nanoparticles: Formation and gradual oxidation mechanism

Synthesis of colloidal metal oxides with controllable size and morphology is burgeoning field of research in nanoscience. Low band gap gray Zn/ZnO colloidal nanoparticles were fabricated by plasma-liquid interaction of DC arc discharge in water. Scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy were employed for morphology, crystal structure and optical characterizations respectively. Optical emission spectroscopy was used to investigate the plasma properties during the synthesis and formation mechanism of nanoparticles. Nanoparticles with different size and shape were fabricated only by adjusting discharge current during synthesis without introducing any chemical agent. Electric discharge current was set to 20, 50, 100 and 150?A during synthesis. Estimated values of plasma excitation energies were 2.41, 2.66, 2.86 and 3.04?eV and diameter size of nanoparticles were 63, 42, 37 and 29?nm for these applied currents respectively. Synthesized nanoparticles were dark gray as prepared and became more transparent gradually getting white color finally. XRD and UV–vis results revealed that the oxidation process was time dependent. The colloidal nanoparticles composed of two metal and metal-oxide phase and white crystalline ZnO was achieved after complete oxidation process. These results provided a flexible and versatile method to synthesize metal oxide nanoparticles with controlled composition.     

纳米氧化锌的气流粉碎改性及应用研究

利用气流粉碎改性工艺,以硬脂酸为改性剂,对纳米氧化锌进行解团聚和表面改性,并借助SEM、XRD、FT-IR和激光粒度分析等对改性产品进行了表征,探讨了改性纳米氧化锌在天然橡胶中的应用。结果表明,与改性前相比,改性纳米氧化锌的解团聚效果明显;颗粒表面亲油疏水,在有机溶剂中有较好的分散性;并且能较好地提高天然橡胶的硫化性能和力学性能。证明该工艺对纳米氧化锌进行表面改性是可行的。     

Preparation of nano-sized flower-like ZnO bunches by a direct precipitation method

In this work, nano-sized ZnO particles were prepared by a direct precipitation method with Zn(NO₃)₂·6H₂O and NH₃·H₂O as raw materials, and the impact of the synthesis process was studied. The optimal thermal calcined temperature of precursor precipitates of ZnO was obtained from the differential thermal analysis (DTA) and the thermal gravimetric analysis (TGA) curves. The purity, microstructure, morphology of the calcined ZnO powders were studied by X-ray diffraction (XRD), energy dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized ZnO powders had a wurtzite structure with high purity. The final products were of flower-like shape and the nanorods which consisted of the flower-like ZnO bunches were 20–100 nm in diameter and 0.5–1 μm in length. The effect of process conditions on the morphology of ZnO was discussed.     

Effect of oxidation and heat treatment on the morphology and electronic structure of carbon-encapsulated iron carbide nanoparticles

Carbon-encapsulated iron carbide nanoparticles have been produced by co-carbonization of a mixture of an aromatic heavy oil and ferrocene at 450 °C under autogenous pressure. Transformations of the morphology and electronic structure of nanoparticles induced by air oxidation and subsequent heat treatment in a nitrogen atmosphere were examined using transmission electron microscopy, X-ray diffraction, near edge X-ray absorption fine structure spectroscopy, and X-ray emission spectroscopy. It was found that hollow nanoparticles, composed of iron oxides and oxidized carbon, were developed with thermal air oxidation of the initial product at 280 °C for 5 h. The mild oxidation of the product (250 °C for 3 h) followed by the carbonization at 500–550 °C yielded the hollow nanoparticles containing iron carbide/oxides and defective graphite-like carbon. The further annealing of nanoparticles at 1000 °C produced carbon nanocapsules with highly graphitized carbon walls and partially filled by spherical iron carbide nanoparticles.     

Effects of different complexing agents on the physical properties of ZnO nanoparticles

ZnO nanoparticles have been synthesised via a co-precipitation method using different complexing agents. X-ray diffraction (XRD) analysis revealed that ZnO nanoparticles were composed of a single hexagonal wurtzite phase. Transmission electron microscopy (TEM) analysis indicates that the samples prepared without any complexing agent have slight agglomeration characteristics presenting a prismatic morphology and a wider size distribution from 22 to 72?nm, which provides good material packing density. However, samples synthesised using urea and glycine are similar and show spherical-like morphology. XRD and TEM analyses indicate that complexing agents also have an important role in the size of the ZnO nanoparticles, where the average particle size of 47 and 22?nm were obtained using urea and glycine, respectively.     

Direct synthesis of monodispersed ZnO nanoparticles in an aqueous solution

Monodispersed ZnO nanoparticles with mesopores were successfully prepared via a simple route through the transformation of Zn(NH₃)₄²⁺ precursor in the presence of sodium oleate and hydrazine at 80 °C with the pH of 8.5. Hydrazine and sodium oleate were used to control the size at 30-60 nm and to improve dispersion properties of ZnO nanoparticles. The samples were characterized by TEM, XRD, IR and TG-DTA, and the results suggest that the grains are composed of ZnO and a small quantity of oleate. The oleate plays an important role in preventing the ZnO nanoparticles from aggregating.     

Synthesis of ZnS nanoparticles of required size by precipitation in aerosol microdroplets

Zinc sulphide (ZnS) nanoparticles were prepared by an aerosol method from zinc acetate and sodium sulphide (Na₂S) aqueous solutions. Aqueous solution of zinc acetate was dispersed into the form of microdroplets, which were introduced by airflow to vigorously stirred aqueous solution of Na₂S, which was in excess. Microdroplets served as microreactors, so the reaction took place only in limited volume. Particle size distribution was studied by transmission electron microscopy and by dynamic light scattering measurements. In this work, the equation that allows us to predict the final size distribution of ZnS nanoparticles using exact concentration of zinc acetate was derived and ZnS nanoparticles with predicted mean particle diameter around 50 and 70?nm were successfully synthetised.     

Sol-gel synthesis,structural and enhanced photocatalytic performance of Al doped ZnO nanoparticles

In this research ZnO and Zn_1?x Al_xO (x = 1, 3, 5, 7% mol) nanoparticles were synthesized by sol-gel method. The effect of Al concentration on the structure, morphology, absorption spectra and photocatalytic properties investigated by using X-ray, TEM, EDS and UV–Vis spectrophotometer approaches. Hexagonal, spherical and rod-like structure was achieved as the dominant structure for undoped nanoparticles, low and high concentrations of doped Al, respectively. Photocatalytic activity of nanoparticles was measured by degradation of methyl orange as a pollutant under radiation of ultraviolet (UV). The experimental test results indicate that the best photocatalytic performance is at of 5% of Al. Furthermore, the doped ZnO nanoparticles have more activity in visible area compared with undoped nanoparticles. The absorption amount in this area increases by raising the Al concentrations. Furthermore, the band gap of the particles decreases from 3.22 eV to 2.93 eV by increasing Al percentage.     

不同形貌纳米ZnO的合成及其光催化性能研究

以Zn(NO3)2·6H2O和NH4HCO3为原料,采用直接沉淀法制备了不同形貌和微观结构的纳米氧化锌。详细研究了反应终点pH值及沉淀前驱物的后处理方式等对粉体的晶体结构、形貌、粒径分布和团聚状况的影响。通过调节反应条件可分别获得网络状或颗粒状纳米氧化锌;光催化降解实验结果表明,网络状纳米氧化锌的光催化性能优于纳米颗粒状产物,而且该网络状和颗粒状纳米氧化锌的光催化活性均明显优于商品光催化剂P25。     

Synthesis and characterization of ZnO/MgO solids prepared by deposition of preformed colloidal ZnO nanoparticles

The ZnO/MgO solids were prepared by colloidal technique which involves the deposition of preformed colloidal ZnO nanoparticles on magnesia. The morphology of ZnO nanoparticles was investigated by transmission electron microscopy and UV-Vis absorption and diffuse reflectance spectroscopy. We found a good agreement between the average radius and the particle size distribution of the ZnO nanoparticles obtained by both methods. It was shown the ability to control the size of the supported ZnO nanoparticles (3.8-4.4nm) by varying pH of the colloidal solution.     

均匀沉淀法制备ZnO、Fe/ZnO光催化剂

以六水合硝酸锌、九水合硝酸铁和CO(NH2)2为原料,采用均匀沉淀法并且改变实验条件制备了纯纳米ZnO和纳米Fe/ZnO光催化剂.通过X射线衍射(XRD)和扫描电子显微镜(SEM)对所有样品进行表征,并对部分样品进行了X射线能谱分析仪(EDS)测试.结果显示所有样品均为六方纤锌矿结构.此外,所有样品均由小颗粒聚集在一起...     

Composition and crystallinity of silicon nanoparticles synthesised by hot wire thermal catalytic pyrolysis at different pressures

The effect of pressure on the structure and composition of silicon nanoparticles synthesized by hot wire thermal catalytic pyrolysis (HW-TCP) of pure silane has been investigated. Light brown powders were produced at silane pressures of 10 and 50 mbar, at a flow rate of 50 sccm, using a tungsten filament at temperatures of 1900 °C and 1800 °C respectively. As determined by transmission electron microscopy and X-ray diffraction, the particles produced at lower pressure have sizes around 10 nm, whereas those produced at higher pressure are typically 50 nm. High resolution transmission electron microscopy (HR-TEM) shows a surface layer of between 2 and 5 nm thickness, which was confirmed by X-ray photoemission spectroscopy to be an oxide shell. Both X-ray diffraction and HR-TEM confirm a high degree of crystallinity in both sets of particles, with Raman spectroscopy indicating an increase in crystalline fraction with synthesis pressure.