液相制备金属纳米结构中导向剂对形貌影响机理的研究进展

基于应用与性能方面的考虑,综述了成分、结构和尺寸等几方面液相可控合成制备纳米金属粉的研究,重点在油水相结构中表面活性剂的作用、液相中表面小分子与金属离子发生作用的原理及强度和离子液体形貌影响机理研究等方面,阐述了导向剂对金属纳米形貌的影响机理.     

液相法制备纳米粒子的粒径控制研究

液相法是目前制备纳米粒子的重要方法之一.本文简要地阐述了液相法制备纳米粒子时粒径控制的机理,并在液相法过程特征的基础上,重点分析了影响粒径分布和形状控制的几个最主要因素,详细解释了化学计量学方法在控制纳米粒子粒度及其分布方面的应用.     

合成工艺对水相合成金纳米颗粒的影响

分别采用柠檬酸三钠和硼氢化钠为还原剂在水相中还原氯金酸制备了稳定的金纳米溶胶。通过透射电子显微镜、激光粒度分析仪、紫外-可见分光光度计对所制备的金纳米颗粒的形貌、结构、粒度分布以及光学特性进行表征,研究了还原剂用量、加热反应时间、反应温度、pH值对水相制备金纳米颗粒的影响。结果表明通过调节合成工艺,可以实现金纳米颗粒的可控生长,制备出平均粒径在5～70nm粒度分布均匀的球形金纳米颗粒。     

水热及溶剂热制备形貌可控CuInS_2光伏材料的研究进展

纳米CuInS_2材料是一种直接带隙半导体材料,其禁带宽度为1.50eV,吸收系数高达10~5cm~(-1),在太阳电池领域有着广阔的应用前景.水热及溶剂热法是液相制备纳米粉体的常用方法之一,其用于制备形貌可控的CuInS_2光伏材料具有独特的优势.介绍了黄铜矿型CuInS_2晶体的结构和性质以及水热及溶剂热法的原理和特点;综述了近年来国内外水热及溶剂热法制备不同形貌与结构CuInS_2光伏材料的研究现状,研究了其制备特点及制备机理;最后探讨了目前存在的问题及今后研究的方向.     

一种无水无氧制备CdS纳米晶的新方法

以醋酸镉和硫为原料,采用二硫化四乙基秋兰姆TETD和2,2-二硫代二苯并噻唑为成核剂,利用无水无氧系统在ODE的溶液中制备了尺寸可控、单分散、均一的半导体CdS纳米材料.采用XRD、粒度分析、SEM技术分别表征产物的结构、粒度和形貌.通过改变两种成核剂的使用量及反应时间可以得到不同粒径的CdS纳米晶.研究表明,在一定范围内,成核剂使用量增加或者反应时间延长都会导致产物的粒度变大,因此通过调节成核荆的使用量和反应时间从而实现对CdS纳米晶的可控生长.     

纳米银液相可控制备的研究进展

纳米银(银纳米颗粒)是一类新兴的银基功能材料。近15年来,随着液相纳米制备技术的快速发展,纳米银的光学、电学性能以及广谱抗菌等生物活性得以深入地研究,并在光电以及生物医学领域获得了重要应用。大量的研究表明,纳米银的上述优异特性强烈依赖于其尺寸、形貌和结构。因此,纳米银的可控制备将是对其特性的合理调控及后续应用的前提。评述了基于液相的纳米银可控制备的研究进展:首先讨论了液相体系中纳米银的生长机制,之后介绍了主要的制备方法,包括直接化学还原法、种子介导生长法、模板法、光诱导法、微波辅助还原法等。在此基础上,根据颗粒的维度,将纳米银分为零维、一维和二维结构,对上述纳米银的代表性结构的可控制备方法及研究现状分别进行了评述。最后简述了纳米银液相可控制备的未来发展方向。     

各向异性银纳米材料的制备及生长机制研究进展

银纳米材料具有许多特异性能,在电学、光学、催化等领域得到了广泛应用,其性能在很大程度上受到形貌、尺度、晶体结构和结晶度等因素的影响,因而研究银纳米材料形貌和尺度的可控制备具有十分重要的意义。从水体系和非水体系两方面综述了液相化学还原法制备银纳米材料的研究工作进展,详细论述了线(棒)形、片(盘)形、立方体形等特异形貌银纳米粒子的制备方法和实验条件;探讨了银纳米材料各向异性形貌的影响因素;提出了不同形貌银纳米晶的形成机理。分析指出晶种的晶型结构尤其是缺陷结构对晶体的最终形貌有很大影响;加入表面修饰剂是防止银纳米颗粒团聚和控制形貌的有效方法。提出了此类研究目前存在的主要问题,展望了其发展方向和趋势。     

模板法制备纳米片状银粉的粒径与形貌控制

模板合成法广泛应用于纳米材料的研究.表面活性剂在水溶液中可以形成多种自组装胶体结构,被认为是纳米材料制备的有效模板,对非球形贵金属纳米粉体的制备很有效.对片状银粉的制备方法进行了总结,特别是纳米片状银粉的模板法制备,探讨了模板法制备纳米片状银粉的原理与影响因素,分析了模板法制备纳米片状银粉的粒径与形貌控制关键,并对纳米片状银粉粒径与形貌控制提出了一些建议.     

微波辅助液相还原法制备超细铜粉

以硫酸铜为原料,水合肼为还原剂,采用微波辅助液相还原法制备了超细铜粉,研究了微波的引入对超细粉体制备的影响,通过XRD、激光粒度分析和TEM表征了粉体的结晶性能、粒度度以及粉体的形貌,研究表明,微波的引入可以明显加速晶化反应的进行,在较短时间内制得的铜纳米晶发育好于传统热处理方式制得的铜纳米晶。     

纳米Au/C催化剂的制备及催化应用研究

选择柠檬酸钠还原法制备尺寸可控的胶体Au纳米粒子溶液,用TEM和UV-Vis吸收光谱对Au纳米粒子的尺寸及形貌进行了表征。然后将Au纳米粒子负载于活性炭上制得了Au/C催化剂。将Au/C催化剂用于液相催化氧化葡萄糖和乙二醛反应,结果表明Au/C催化剂的催化活性较高,这一制备方法较为成功。并对催化反应机理进行了探讨。     

Nonspherical Noble Metal Nanoparticles: Colloid‐Chemical Synthesis and Morphology Control

Metal nanoparticles have been the subject of widespread research over the past two decades. In recent years, noble metals have been the focus of numerous studies involving synthesis, characterization, and applications. Synthesis of an impressive range of noble metal nanoparticles with varied morphologies has been reported. Researchers have made a great progress in learning how to engineer materials on a nanometer length scale that has led to the understanding of the fundamental size‐ and shape‐dependent properties of matter and to devising of new applications. In this article, we review the recent progress in the colloid‐chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt), highlighting the factors that influence the particle morphology and discussing the mechanisms behind the nonspherical shape evolution. The article attempts to present a thorough discussion of the basic principles as well as state‐of‐the‐art morphology control in noble metal nanoparticles.     

Cobalt nanoparticles prepared by three different methods

This work aimed to study cobalt nanoparticles (Co-NPs) preparation using three different methods in order to evaluate the effect of synthesis variables that can influence the nanoparticle size distribution and particle shape. The synthesised nanoparticles were characterised by Transmission Electron Microscopy. The first synthesis employed decomposition of Co₂(CO)₈, at high temperatures. This procedure resulted in spherical nanoparticles with low size distribution. The size of Co-NPs could be tuned by modification of precursor/surfactant, nevertheless the stirring and injection time influenced the size distribution. Using polyol process, at high temperatures, it was produced undefined-shape nanoparticles. This result suggests that the solution composition, i.e. the amount of trioctylphosphine and oleic acid was not suitable to control both size and shape of nanoparticles. Finally, the method based on reduction with NaBH₄ resulted spherical nanoparticles with tiny sizes, indicating that in this case a variation on amount of reductant would be more efficient on the particle size control than a variation in concentration of oleic acid. These results indicated that, for each method, a different variable exists for the control of the distribution size and the shape of the formed particles.     

Shape Control of Colloidal Metal Nanocrystals

Colloidal metal nanoparticles are emerging as key materials for catalysis, plasmonics, sensing, and spectroscopy. Within these applications, control of nanoparticle shape lends increasing functionality and selectivity. Shape‐controlled nanocrystals possess well‐defined surfaces and morphologies because their nucleation and growth are controlled at the atomic level. An overall picture of shaped metal particles is presented, with a particular focus on solution‐based syntheses for the noble metals. General strategies for synthetic control are discussed, emphasizing key factors that result in anisotropic, nonspherical growth such as crystallographically selective adsorbates and seeding processes.     

Kinetic Study of the Formation of Polypyrrole Nanoparticles in Water‐Soluble Polymer/Metal Cation Systems: A Light‐Scattering Analysis

A facile way to synthesize nanometer‐sized polymer (polypyrrole, PPy) particles is explored on the basis of the formation of complexes between water‐soluble polymers and metal cations in aqueous solution. The metal cation is used as an oxidizing agent to initiate the chemical oxidation polymerization of the corresponding monomer, and the water‐soluble polymer effectively provides a steric stability for the growth of polymer nanoparticles during the polymerization process. Light‐scattering analyses are performed to give insight into the behavior of the complexes in aqueous solution. In addition, major physical parameters affecting the formation of polymer nanoparticles are investigated, including hydrodynamic radius, radius of gyration, shape factor, and viscosity. By judicious control of these parameters, PPy nanoparticles with narrow size distribution can be readily fabricated in large quantities. It is also possible to control the diameter of the nanoparticles by changing critical synthetic variables. Importantly, PPy nanoparticles of ≈ 20–60 nm in diameter can be prepared without using any surfactants or specific templates; this novel strategy offers great possibility for mass production of polymer nanoparticles.     

A new route for mass production of uniform metal nanoparticles in water by means of laser light induced processes

In this contribution, we report a new route for mass fabrication of metal nanoparticles with monodisperse shape and narrow size distribution in water applying exclusively physical processes. For this purpose, we have combined pulsed laser ablation with the technique of selective laser tailoring. For example, pulsed laser ablation from a gold plate in water results in a large amount of nanoparticles with radii in the range of R = 75 nm with a relatively broad size distribution of sigma = 31%. This broad size distribution has been subsequently narrowed in a single irradiation step to sigma = 20% without a significant change of the mean nanoparticle radius utilizing selective laser tailoring. The main advantage of the laser based process, besides rapid processing, is that no chemicals, which are undesired for many applications, are necessary. Hence, mass production of nanoparticles with narrow size and monodisperse shape distribution in water becomes feasible.     

Gold/palladium and silver/palladium colloids as novel metallic substrates for surface-enhanced Raman scattering

New surface-enhanced Raman scattering (SERS) substrates, composed of gold or silver colloidal nanoparticles doped with palladium, were prepared. These novel colloids are stable and maintain a satisfactory SERS efficiency, even after long aging. The interest in doping the coinage metal nanoparticles with palladium is due to the well-known catalytic activity of this metal. Transmission electron microscopy (TEM) and ultraviolet-visible absorption spectroscopy were used to characterize the shape and size of the metal particles. It was found that these bimetallic colloidal nanoparticles have a core-shell structure, with gold or silver coated with palladium clusters.     

Surfactant‐Free Shape Control of Gold Nanoparticles Enabled by Unified Theoretical Framework of Nanocrystal Synthesis

Gold nanoparticles have unique properties that are highly dependent on their shape and size. Synthetic methods that enable precise control over nanoparticle morphology currently require shape‐directing agents such as surfactants or polymers that force growth in a particular direction by adsorbing to specific crystal facets. These auxiliary reagents passivate the nanoparticles' surface, and thus decrease their performance in applications like catalysis and surface‐enhanced Raman scattering. Here, a surfactant‐ and polymer‐free approach to achieving high‐performance gold nanoparticles is reported. A theoretical framework to elucidate the growth mechanism of nanoparticles in surfactant‐free media is developed and it is applied to identify strategies for shape‐controlled syntheses. Using the results of the analyses, a simple, green‐chemistry synthesis of the four most commonly used morphologies: nanostars, nanospheres, nanorods, and nanoplates is designed. The nanoparticles synthesized by this method outperform analogous particles with surfactant and polymer coatings in both catalysis and surface‐enhanced Raman scattering.     

异丙醇体系中多形态氧化铝纳米粒子的制备研究

本文研究以无毒异丙醇代替苯系溶剂由醇盐水解法制备纳米氧化铝过程中,三维聚酰胺树状物(PAMAMs)及其铵盐、钠盐对氧化铝粒子形态的调控作用,同时研究了水解温度、凝胶温度对颗粒形态的影响.结果表明,在反应物中加入适当的改性剂和控制反应温度,能够使颗粒形状控制为球形、针状、棒状、纤维状及片状,其尺寸范围为3～100nm.