The effect of surface properties on visible luminescence of nanosized colloidal ZnO membranes

Luminescence properties of nanosized zinc oxide (ZnO) colloids depend greatly on their surface properties, which are in turn largely determined by the method of preparation. ZnO nanoparticles in the size range from 3 to 9 nm were prepared by addition of tetramethylammonium hydroxide ((CH3)4NOH) to an ethanolic zinc acetate solution. X-ray diffraction (XRD) indicates nanocrystalline ZnO membranes with polycrystalline hexagonal wurtzite structure. The ZnO membranes have a strong visible-emission intensity and the intensity depends upon hydrolysis time. The infrared spectra imply a variety of forms of zinc acetate complexes present on the surface of ZnO particles. The effect of the ZnO membrane surface properties on photoluminescence is discussed.     

Non-Basic Solution Routes to Prepare ZnO Nanoparticles

Nanocrystalline ZnO particles were prepared from alcoholic solutions of zinc acetate dihydrate without using base such as NaOH or LiOH through a colloid process carried out at a low temperature of 60°C. A comparative study of chemical reactions from zinc acetate dihydrate to ZnO was made using different types of monool solvents, i.e. methanol, ethanol, and 2-methoxyethanol. It was revealed that layered hydroxide zinc acetate was formed as an intermediate and its transformation into ZnO was a key reaction step in any of the solutions. Reaction time necessary for the precipitation of ZnO was greatly influenced by the solvents used. Methanol was useful for the preparation of the ZnO nanoparticles, which were chemically pure in terms of cation impurities and exhibited green photoluminescence by the ultraviolet excitation.     

In situ and simultaneous nanostructural and spectroscopic studies of ZnO nanoparticle and Zn-HDS formations from hydrolysis of ethanolic zinc acetate solutions induced by water

The simultaneous formation of nanometer sized zinc oxide (ZnO), and acetate zinc hydroxide double salt (Zn-HDS) is described. These phases, obtained using the sol-gel synthesis route based on zinc acetate salt in alcoholic media, were identified by direct characterization of the reaction products in solution using complementary techniques: nephelometry, in situ Small-Angle X-ray Scattering (SAXS), UV-Vis spectroscopy and Extended X-ray Absorption Fine Structures (EXAFS). In particular, the hydrolytic pathway of ethanolic zinc acetate precursor solutions promoted by addition of water with the molar ratio N=[H₂O]/[Zn²⁺] = 0.05 was investigated in this paper. The aim was to understand the formation mechanism of ZnO colloidal suspension and to reveal the factors responsible for the formation of Zn-HDS in the final precipitates. The growth mechanism of ZnO nanoparticles is based on primary particle (radius ≈ 1.5 nm) rotation inside the primary aggregate (radius <3.5 nm) giving rise to an epitaxial attachment of particles and then subsequent coalescence. The growth of second ZnO aggregates is not associated with the Otswald ripening, and could be associated with changes in equilibrium between solute species induced by the superficial etching of Zn-HDS particles at the advanced stage of kinetic.     

Study on luminescence characteristic of the ZnO/polymer hybrid films

The cyclohexane solution of PS (polystyrene) and the ethyl acetate solution of PMMA (polymethyl methacrylate) were used as flowing liquid; the ZnO/polymer hybrid colloids were successively produced by focused pulsed laser ablation of ZnO target in interface of solid and flowing liquid. As solvent in the hybrid colloids has volatized, the ZnO/polymer hybrid films were obtained. The hybrid colloids were characterized by high-resolution transmission electron microscopy (HRTEM) and select-area electron diffraction (SEAD). The results show a good dispersion of the ZnO nanoparticles in the polymer matrix. The hybrid films were characterized by fluorescence spectrum, Fourier transform infrared spectroscopy (FTIR) spectroscopy, thermogravimetry with FTIR (TG/FTIR), and X-ray photoelectron spectrum. The results show the ZnO/polymer hybrid films can radiate strong blue light under ultraviolet. Meanwhile, the ZnO/polymer hybrid films have higher chemical stability than ZnO nanoparticles because nano-ZnO nanoparticles were enwrapped by polymers. In addition, the ZnO hybrid films have higher thermal stability then the related pure polymers because of strong interaction among ZnO nanoparticles and polymers.     

纳米氧化锌粒子分散性对其吸收光谱的影响

在异丙醇中用氢氧化钠分别与醋酸锌及溴化锌反应制备了纳米氧化锌粒子. 分别用高分辨率电子显微镜及原位紫外吸收光谱测定了粒子大小及分布. 实验结果表明, 粒子的增大服从LSW (Lifshitz-Slyozov-Wagner)模型, 即粒子体积随老化时间线性增大；但粒子的分布不符合LSW模型, 这与他人的研究结果不一致. 用计算机数值模拟确定了纳米氧化锌分布函数对其紫外吸收光谱的影响, 发现在紫外吸收边附近光谱发生弯曲, 且随粒子分布标准方差(SD)的增大, 弯曲更显著, 引起紫外吸收光谱红移, 这将导致用吸收边计算氧化锌粒子大小时产生正误差. 就单分散(SD/γ<5%, γ是粒子的平均半径)纳米氧化锌而言, 这种正误差仅为2%, 但当粒子分布的SD/γ达到15%时, 所产生的正误差可高达15.1%.     

有机修饰氧化硅对抗紫外纳米ZnO的原位表面修饰

以正硅酸乙酯和二甲基二乙氧基硅烷作为共前驱体,通过溶胶-凝胶反应得到有机修饰氧化硅;用有机修饰氧化硅对碱式碳酸锌进行原位表面改性,通过对表面改性碱式碳酸锌进行热处理得到表面改性纳米ZnO;分析了表面改性纳米ZnO的结构和性能.结果表明,经有机修饰氧化硅改性处理的纳米ZnO具有强憎水性,与有机相的相容性较强,光催化活性得...     

Application of ZnO nanoparticles to enhance the antimicrobial activity and ultraviolet protective property of bamboo pulp fabric

Hyperbranched polymer HSDA was synthesized from methyl acrylate, tetraethylenepentamine, and dodecanoic acid by melt polycondensation. ZnO nanoparticle colloidal solution was prepared in one step by mixing Zn(NO₃)₂ and HSDA aqueous solution under hydrothermal condition. The results of transmission electron microscopy and ultraviolet–visible (UV–Vis) spectroscopy indicated that ZnO nanoparticles were formed in colloidal solution. Bamboo pulp fabric was treated with ZnO nanoparticle colloidal solution by an impregnation method to provide the bamboo pulp fabric with antibacterial and UV protective properties. The whiteness, antibacterial activity, UV protective property, and washing durability of the ZnO nanoparticle-treated fabrics were determined. The results indicated that the bamboo pulp fabric treated with ZnO nanoparticles showed good UV protective properties and its ultraviolet protection factor (UPF) can reach 90.38. The UPF value of treated fabric drops to 70.42 after washing for 20 times, but it retains good UV protective properties. The ZnO nanoparticle-treated fabric showed 99.91 % bacterial reduction of Staphylococcus aureus and 99.97 % bacterial reduction of Escherichia coli. The fabric retained over 98.93 % reduction level even after being exposed to 20 consecutive home-laundering conditions. In addition, the results of scanning electron microscopy and X-ray spectroscopy confirmed that ZnO nanoparticles were fixed and well dispersed on bamboo pulp fabric.     

Palladium nanoparticles from solvated atoms—stability and HRTEM characterization

Palladium particles of nanometric dimensions were synthesized by the chemical liquid deposition method in which the Pd atoms were co-deposited at 77 K with 2-propanol, acetone, and tetrahydrofurane vapor to obtain colloidal dispersions. The colloidal dispersions were characterized by UV–visible spectrophotometry, transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). The palladium colloids synthesized by use of these solvents are very stable. A strong absorption band in the UV region suggests that quantum confinement occurs in the nanoparticles obtained by this procedure. Studies of TEM micrographs reveal average size distributions between 1 and 5 nm for all Pd colloids. Whereas particle sizes in Pd–2-propanol colloids are not very sensitive to concentration change, the particle-size average in Pd–acetone and Pd–THF increases by 0.5 nm when the concentration increases from 10^–3 to 10^–2 mol l^–1. The HRTEM results show the high crystallinity of Pd nanoparticles and three low-energy structure shapes were found: cuboctahedron, tetrakaidecahedron, and icosahedron.     

High Photocatalytic Properties of Zinc OxideNanoparticles with Amidoximated BacterialCellulose Nanofibers as Templates简

The freshly prepared water-wet amidoximated bacterial cellulose （Am-BC） serves as an effective nanoreactor to synthesis zinc oxide nanoparticles by in situ polyol method. The obtained ZnO/Am-BC nanocomposites have been characterized by field emission scanning electron microscopy （FE-SEM）, X-ray diffraction （XRD）, Fourier transformed infrared spectroscopy （FTIR） and thermogravimetric analysis （TGA）. The influence of the zinc acetate concentration on the morphologies and size ofZnO nanoparticles and the possible formation mechanism were discussed. The results indicated that uniform ZnO nanoparticles were homogeneously anchored on the Am-BC nanofibers through strong interaction between the hydroxyl and amino groups of Am-BC and ZnO nanoparticles. The loading content of ZnO nanoparticles is higher using Am-BC as a template than using the unmodified bacterial cellulose. The resultant nanocomposite synthesized at 0.05 wt% shows a high photocatalytic activity （92%） in the degradation of methyl orange.     

Novel Green Route of Synthesis of ZnO Nanoparticles by Using Natural Biodegradable Polymer and Its Application as a Catalyst for Oxidation of Aldehydes

ZnO nanoparticles have been synthesized by using biodegradable natural biopolymer viz. Gum Tragacanth. This single step approach is very cost effective and reproducible. The reaction time and concentration of precursor zinc acetate play a major role in the nature and growth of ZnO nanoparticles. ZnO nanoparticles were characterized by X-ray diffraction, SEM, FTIR, EDAX, UV-visible spectroscopy and TEM. ZnO nanoparticles with 20-30 nm in diameter and hexagonal morphology were found; dispersed uniformly. Raman spectrum shows the mode E₂ high at 437 cm^?1 that is related to the vibration of wurtzite Zn-O bond in crystal structure of ZnO. The space between adjacent lattice fringes is ～ sharp 2.42 Å. UV-visible absorption spectrum shows the sharp absorption band at 308 nm assigned to the intrinsic transition from valance band to conduction band. The ZnO nanoparticles display superior catalytic activity of conversion of aldehyde to acid as compared to bulk-ZnO material, because of high surface area of ZnO nanoparticles. A trace amount of ZnO nanoparticles catalyst required for organic conversion. The ZnO nanoparticles as catalyst are highly stable, recyclable and efficient in its activity.     

Colloids based on gold nanoparticles dispersed in castor oil: Synthesis parameters and the effect of the free fatty acid content

Herein, we present our results related to the synthesis of colloidal solutions of gold nanoparticles (AuNPs) dispersed in castor oil. These colloids were prepared via a wet chemistry process by mixing specific amounts of castor oil, ethanol, and aqueous solutions of tetrachloroauric(III) acid and sodium hydroxide. The size and shape of the AuNPs obtained could be modulated by the amount of gold source added and the Au/OH^– molar ratio used. In this study, we observed that the free fatty acid content in the reaction medium was an important parameter to be considered in the syntheses of the colloidal solutions and the respective form and shape of the AuNPs produced. Thus, we evaluated the effect of oil acidity by adding different amounts of myristic acid (MA) in the reaction medium. The colloids were characterized by UV–vis spectroscopy, and the size and shape of the AuNPs produced were characterized by transmission electron microscopy (TEM).     

Adhesion of Colloidal SiO(2) Particles on ZnS-Type Phosphor Surfaces

The interaction between colloidal SiO(2) particles and the surface of ZnS-type phosphors has been studied. The green emitting phosphor ZnS:Cu,Al,Au applied in color television tubes was chosen as a model compound. After the surface of the phosphor particles (d(50)=5.0 μm) was treated in different manners like washing with H(2)O, HCl, or H(2)O(2) as well as precoating with colloidal ZnO particles (d(50)=81 nm), colloidal SiO(2) particles (d(50)=207 nm) were added. Thereafter, the amount of adhered SiO(2) was investigated based on SEM and ESCA analysis. By ESA measurements the surface charge of the colloids and the differently treated ZnS materials was investigated. Based on the experimental results it can be concluded that colloidal SiO(2) particles adhere sufficiently only if ZnO is present on the ZnS surface. The SiO(2) particles are located on top of the ZnO. Finally, the attractive interactions in the system ZnS-ZnO-SiO(2) are discussed in more detail. Copyright 2000 Academic Press.     

Pd/ZnO和Ag/ZnO复合纳米粒子的制备、表征及光催化活性

 用焙烧前驱物碱式碳酸锌的方法制备了ZnO纳米粒子，采用光还原沉积贵金属的方法制备了Pd／ZnO和Ag／ZnO复合纳米粒子，并利用ICP，XRD，TEM和XPS等测试技术对样品进行了表征，初步探讨了贵金属在ZnO纳米粒子表面形成原子簇的原因．以光催化氧化气相正庚烷为模型反应，考察了样品的光催化活性以及贵金属沉积量对催化剂活性的影响．结果表明：沉积适量的贵金属，ZnO纳米粒子光催化剂的活性大幅度提高．同时，深入探讨了表面沉积贵金属的ZnO纳米粒子光催化剂活性有所提高的内在原因．     

Fabrication of zinc/silver binary nanoparticles,their enhanced microbial and adsorbing properties

Monometallic ZnO nanoparticles were prepared by hydrolysis of zinc acetate with ammonium hydroxide solution. Bimetallic zinc-silver nanoparticles (ZnO-AgNPs) were prepared using metal displacement galvanic cell reaction in presence of cetyltrimethylammonium bromide (CTAB). The optical and photo-physical properties of both NPs were determined. Surface plasmon resonance (SPR) intensity of ZnO-AgNPs depends on the ratio of metal salt precursors and other experimental conditions. The optical band gap (2.98 eV), agglomeration number (26819.92), and molar concentration (1.14 × 10⁻⁴ mol/liter) of ZnO-AgNPs were determined. Langmuir adsorption monolayer, Freundlich, intraparticles diffusion and multilayer adsorption isotherms used for the determination of maximum adsorption efficiency and adsorption isotherm parameters to the removal of safranin dye from an aqueous solution. The kinetics of safranin removal has also been discussed with pseudo-first order, pseudo-second order, intraparticle diffusion and multilayer kinetic models. The antibacterial and antifungal activities of ZnO, Ag and ZnO-AgNPs were determined against human pathogens using growth kinetic and disk diffusion methods. The concentrations of ZnO-AgNPs have significant effect on the bacterial growth kinetics. The death rate constants increase with increasing the NPs concentrations. It has been found that the ZnO-AgNPs hold higher microbial activities than that of monometallic counterpart, ZnO and AgNPs. Mechanism of bacterial growth and death was discussed.     

Spherical Zinc Oxide Nano Particles from Zinc Acetate in the Precipitation Method

The liquid precipitation method using zinc acetate dihydrate was applied for the synthesis of uniform and spherical ZnO nanoparticles. The ultrafine zinc oxid was prepared in a water‐ethanol mixture solution. The solution containing zinc cation was soluble in water. The surface‐active agent triethanolamine (TEA) was soluble in ethanol. Then alkali precipitated by adding n‐propylamine. The spherical zinc oxide particle morphology was found to be highly dependent on the zinc salt concentration, ethanol‐water ratio, and the surface‐active agent additive. The process can produce white ZnO powder of 50–90 nm in size. The morphology of zinc oxide showed a powder shape by transmission electron microscopy (TEM), the crystallization phase structure of zinc oxide by X‐ray diffraction (XRD), and the zinc oxide remaining by using an organic analysis by infrared spectroscopy (IR).     

纳米片状ZnO的室温制备及其胶状前体的稳定性分析

以醋酸锌和氢氧化钠为原料,采用室温直接沉淀法得到了ZnO的前体胶状醋酸锌碱式盐,通过控制pH值,在室温下分别制备了碱式盐Zn5(OH)8(Ac)2·2H2O和六方晶系纤锌矿ZnO,并利用X射线衍射、扫描电子显微镜和能谱(EDS)等测试技术对产物进行表征。 结果表明,采用直接沉淀法在pH值为7的环境下得到了具有{n{[Zn5(OH)8(H2O)2]2+}·(2n-x)Ac-}x+·xAc-胶团结构的稳定胶体体系,室温下干燥后的产物的成分为碱式盐Zn5(OH)8(Ac)2·2H2O;而在pH值为14时,胶状前体发生聚沉生成白色沉淀,室温干燥后得到纳米片状ZnO。 还考察了pH值对胶状前体稳定性的影响,并探讨了ZnO的生成机理。     

Synthesis of ZnO/polystyrene composites particles by Pickering emulsion polymerization

ZnO/polystyrene composite particles were synthesized by Pickering emulsion polymerization. ZnO nanoparticles were first prepared by reaction of zinc acetate and sodium hydroxide in ethanol medium. Then different amount of styrene monomer was emulsified in water in the presence of ZnO nanoparticles either by mechanical stirring or by sonication, followed by polymerization of styrene. Two kinds of initiators were used to start the polymerization, azobisisobutyronitrile (AIBN) and potassium persulfate (KPS). The X-ray diffraction pattern verified the crystal structure of ZnO and FT-IR spectra evidenced the existence of ZnO and polystyrene (PS) in ZnO/polystyrene composite particles. Different morphologies were observed for the composite particles when using different initiators. From TEM photographs, AIBN-initiated system produced mainly core-shell composite particles with PS as core and ZnO as shell, while KPS-initiated system showed both composite particles and pure PS particles. Two schemes of reaction mechanism were proposed to explain the morphologies accordingly. Both systems of composite particles showed good pH adjusting ability.     

Germanium nanoparticles from solvated atoms: synthesis and characterization

Germanium nanoparticles were synthesized by the chemical liquid deposition method (CLD) in which the Ge atoms, produced resistively, were co-deposited with 2-propanol, acetone and tetrahydrofurane vapors to obtain colloidal dispersions. The colloidal dispersions were characterized by UV-vis spectrophotometry, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and Infrared Spectroscopy (FTIR) techniques. The Germanium colloids are, in general, kinetically unstable. Strong absorption bands in the UV region suggest that nanoparticles obtained by this procedure exhibit quantum confinement. In the Ge colloids, the particle size distribution is highly sensitive to concentration change. For example, the TEM measurements revealed for the Ge-2-propanol colloid, particle sizes close to 3 nm for a concentration of 10^–3 M and 30 nm for a concentration of 10^–2 M. The HRTEM and SAED showed the high crystallinity of the nanoparticles, and it was possible to observe the typical lattice spaces of a diamond cubic Ge structure. The FTIR studies revealed the Ge-organic nature of the particles surface. Mechanisms and structures have been proposed for surface reactions.     

Synthesis and optical properties of ZnO nanostructures in imidazolium-based ionic liquids

Different morphologies of ZnO nanostructures have been synthesized by a simple reflux method, in imidazolium-based ionic liquids and water as a solvent. The effects of ionic liquid as a template with different concentrations and the amount of sodium hydroxide on the morphology and size of nanostructures were investigated. The structural and optical properties of these ZnO particles were studied by using XRD, SEM and UV–Visible. The characteristic results revealed that using different ionic liquids in water not only prevent a drastic increase in the crystallite size of the zinc oxide species but also provide suitable conditions for the oriented growth of primary nanoparticles with nano sheet and nano hallow block. The results show that the longer alkyl chain at position-1 of imidazole ring or using dicationic ionic liquid with a definite concentration cause the more width of nano sheet. A possible mechanism was proposed to explain the formation of ZnO nanostructures with different morphology.     

双盘状ZnO的可控制备

采用水热法制备了形貌可控、 尺寸均一的双盘状ZnO. X射线粉末衍射(XRD)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)等测试结果表明, 制备的ZnO具有六方纤锌矿结构, 由2个直径约为4 μm, 厚度约为600 nm的圆盘复合而成. 考察了反应温度和乙酸锌与柠檬酸钾的摩尔比对产物形貌与尺寸的影响, 实现了双盘状ZnO的可控合成, 并初步探讨了其形成机理. 荧光光谱显示, 双盘状ZnO的紫外发射峰半高宽约为10 nm, 比块体ZnO的紫外发射峰半高宽(18 nm)窄, 表明双盘状ZnO具有更好的光学特性.