纳米/微米结构粒子合成技术进展

介绍了近年来纳米/微米结构粒子的合成技术进展,将纳米单元(纳米棒、纳米带、纳米片、纳米颗粒)自组装为各种尺度的有序结构会产生更优异的整体协同性质,这对纳米/微米结构粒子的性能研究有重要意义。主要介绍了表面活性剂法、水热法和模板诱导法等。表面活性剂由于具有多种特殊、优异的性能,包覆在纳米粒子表面可使其组装成具有新颖结构的聚集体,是目前研究热点。水热法所得粒子具有纯度高、分散性好、晶形可控,生产成本低等特点已被广泛采用。     

巨型表面活性剂的溶液自组装

两亲性化合物的溶液自组装可形成有序的纳米结构,在纳米科学、生物载药、光电子等领域有着巨大的应用价值。近十年来,以具有三维刚性结构的分子纳米粒子为结构基元,研究者发展了一种分子尺度介于小分子表面活性剂和两亲性嵌段共聚物之间的两亲性化合物——巨型表面活性剂。巨型表面活性剂通过高效的"点击"化学连接亲水的分子纳米粒子头和疏水的聚合物尾链,具有精准的化学结构和灵活的分子构型可调节性。文中系统总结了巨型表面活性剂在溶液自组装方面的研究进展,从自组装体的形成机理角度,阐述了在溶液中巨型表面活性剂的自组装体的形成和演化。通过精准调控巨型表面活性剂的化学结构、分子构型以及实验条件可以得到丰富多样的有趣的自组装结构,这种自下而上构筑有序纳米结构的方法,为纳米技术的应用提供了多样化的材料库。     

AOT表面修饰CdS纳米粒子的合成与表征

以AOT为表面活性剂,硫脲及乙酸镉为原料,磷酸二氢钾为相转移剂,分别在水相和有机相中制备了CdS纳米粒子.UV-Vis光谱表明,CdS纳米粒子具有明显的量子尺寸效应.FTIR光谱分析表明,水相中AOT分子的-S=O、-C-O、-C=O基团指向溶剂,-CH2-基团堆砌在CdS纳米粒子表面,而有机相中则相反.TEM测试结果表明,有机相球形CdS纳米粒子具有较好的自组装行为,其尺寸为5～10nm且分布较窄.     

纳米粒子自组装无机硅/有机硅复合功能膜技术

采用自组装法对纳米粒子表面进行修饰,修饰效果表明:控制了纳米粒子的表面态,使纳米粒子稳定化;赋予纳米粒子无机硅/有机硅复合功能膜,使纳米粒子适用性广、高性能、多功能;不仅扩大了在传统产业中的应用范围,而且还可作为纳米结构的结构单元,用于自组装纳米功能器件等纳米结构材料.文中介绍了这一技术的原理、工艺、修饰效果以及特点.     

应用反胶团体系制备纳米粒子的形态控制

与其他制备方法相比,反胶团体系在制备纳米粒子方面具有明显的优势,这一点在对产物粒子形态的控制方面体现得最显著.表面活性剂在体系中起模板作用,因而可以通过控制表面活性剂形成的胶束的形态来控制产物粒子的形态.着重介绍在用反胶团体系制备纳米粒子的方法中,对产物粒子形态控制方面的研究进展.另外,孤立的纳米粒子与其聚集体的性质并不相同,聚集体的性质受聚集产物自身组装形态的控制,因此还概括了近年来在反胶团体系中制备纳米粒子聚集体的研究工作.     

纳米态电极催化材料Au-Pt/半胱氨酸/Au电极的制备及性能研究

利用自组装技术制备了纳米态Au-Pt/半胱氨酸/Au电极,TEM、ED、XPS等研究表明双金属纳米粒子为Au合金,粒子的平均粒径＜10nm;通过组装时间可以控制双金属纳米颗粒组装的数量.对组装电极的电化学性能进行了测试,通过SEM对其表面结构进行了表征.结果表明,利用自组装方法可以制备纳米态Au-Pt/半胱氨酸/Au电极,该电极具有良好的电催化性能.     

卟啉纳米结构合成获进展 有望提升燃料电池性能

中科院长春光机所发光学及应用国家重点实验室（筹）研究员孙再成与河南大学教育部特种功能材料实验室教授白峰合作,研究了卟啉分子在表面活性剂辅助下的自组装问题。研究表明,卟啉分子可以自组装成从纳米线、纳米短棒到八面体的纳米颗粒。     

表面活性剂辅助室温液相合成BaCO3纳米棒

用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)为形貌控制剂,通过室温液相反应成功制备出BaCO3纳米棒.纳米棒的直径为60～250nm、长度达几微米.用X射线粉末衍射和透射显微镜技术对所制备纳米晶的成分、形状和尺寸进行了表征分析.研究结果表明,表面活性剂对BaCO~纳米棒的形成起着关键的作用.对BaCO~纳米棒的形成机理作了深入的讨论,提出了BaCO3纳米棒的表面活性剂软模板诱导自组装生长机理.     

表面活性剂辅助低温固相合成CuS纳米棒

用表面活性剂聚乙二醇400为形貌控制剂,通过低温固相反应成功制备出CuS纳米棒.纳米棒的直径为10～60 nm、长度为100～600 nm.研究结果表明,在反应过程中,表面活性剂所形成的结构对最终纳米晶的形貌起着决定性的作用.用X射线粉末衍射和透射显微镜技术对所制备纳米晶的成分、形状和尺寸进行了表征分析.对CuS纳米棒的形成机理作了深入的讨论,提出了CuS纳米棒的表面活性剂软模板诱导自组装生长机理.     

金纳米粒子的制备及自组装

金纳米粒子以它独特的光学、电学和催化性质以及在纳米级电子线路中的应用潜力,受到人们越来越多的关注.本文主要评述了金纳米粒子的合成方法和自组装技术,即对各种制备方法和自组装的特点、纳米粒子的生长机理和自组装机理进行了介绍.展望了金纳米材料未来的研究方向和发展趋势.     

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.     

CTAB-Assisted Synthesis of Size- and Shape-Controlled Gold Nanoparticles in SDS Aqueous Solution

Variously shaped gold nanoparticles were hydrothermally prepared by adding the cationic surfactant cethyltrimetylammonium bromide (CTAB) into the anionic surfactant sodium dodecyl sulfonate (SDS) in aqueous solution at 180°C without reducing agents and/or templates. Nanoparticle size and shape were controlled by the surfactant mixing ratio CTAB:SDS = x_CTAB:(1 − x_CTAB) and reaction time. Increasing CTAB concentration from x = 0.01 to x = 0.07 changes the nanoparticle shape from icosahedron to triangle or ellipse. The influence of the cationic/anionic ratio is presumably due to the differing catanionic micelle structures.     

Synthesis of nanocrystalline hydroxyapatite using surfactant template systems: Role of templates in controlling morphology

Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium nitrate and phosphoric acid as starting materials in aqueous phase. Cyclohexane, hexane, and isooctane were used as organic solvents, and Dioctyl sulfosuccinate sodium salt (AOT), dodecyl phosphate (DP), NP5 (poly(oxyethylene)₅ nonylphenol ether), and NP12 (poly(oxyethylene)₁₂ nonylphenol ether) as surfactants to make the emulsion. Effect of synthesis parameters, such as type of surfactant, aqueous to organic ratio (A/O), pH and temperature on powder characteristics were studied. It was found that the surfactant templates played a significant role in regulating the morphology of the nanoparticle. Hydroxyapatite nanoparticle of different morphologies such as spherical, needle shape or rod-like were obtained by adjusting the conditions of the emulsion system. Synthesized powder was characterized using X-ray diffraction (XRD), BET surface area and transmission electron microscopy (TEM). Phase pure HA nanopowder with highest surface area of 121 m²/g were prepared by this technique using NP5 as a surfactant. Densification studies showed that this nanoparticle can give about 98% of their theoretical density. In vitro bioactivity of the dense HA compacts was confirmed by excellent apatite layer formation after 21 days in SBF solution. Cell material interaction study showed good cell attachment and after 5 days cells were proliferated on HA compacts in OPC1 cell culture medium. The results imply this to be a versatile approach for making hydroxyapatite nanocrystals with controlled morphology and excellent biocompatibility.     

液相制备纳米金属粉的粒度及形貌控制研究进展

纳米金属粉的粒度和颗粒形状决定其性能和应用,粒度和形貌的控制对纳米金属粉的制备至关重要.主要从纳米金属粉的粒度可控制备、形貌可控制备和复合结构纳米金属粉的制备3方面阐述了液相制备纳米金属粉的粒度和形貌控制研究现状;并总结了液相制备纳米金属粉的粒度和形貌控制作用机理.     

Viscosity,density, and thermal conductivity of aluminum oxide and zinc oxide nanolubricants

This paper presents liquid kinematic viscosity, density, and thermal conductivity measurements of eleven different synthetic polyolester-based nanoparticle nanolubricants (dispersions) at atmospheric pressure over the temperature range 288 K to 318 K. Aluminum oxide (Al₂O₃) and zinc oxide (ZnO) nanoparticles with nominal diameters of 127 nm and 135 nm, respectively, were investigated. A good dispersion of the spherical and non-spherical nanoparticles in the lubricant was maintained with a surfactant. Viscosity, density, and thermal conductivity measurements were made for the neat lubricant along with eleven nanolubricants with differing nanoparticle and surfactant mass fractions. Existing models were used to predict kinematic viscosity (±20%), thermal conductivity (±1%), and specific volume (±6%) of the nanolubricant as a function of temperature, nanoparticle mass fraction, surfactant mass fraction, and nanoparticle diameter. The liquid viscosity, density and thermal conductivity were shown to increase with respect to increasing nanoparticle mass fraction.     

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.     

Surfactant-induced postsynthetic modulation of Pd nanoparticle crystallinity

Modulation of Pd nanoparticle (NP) crystallinity is achieved by switching the surfactants of different binding strengths. Pd NPs synthesized in the presence of weak binding surfactants such as oleylamine possess polyhedral shapes and a polycrystalline nature. When oleylamine is substituted by trioctylphosphine, a much stronger binding surfactant, the particles become spherical and their crystallinity decreases significantly. Moreover, the Pd NPs reconvert their polycrystalline structure when the surfactant is switched back to oleylamine. Through control experiments and molecular dynamics simulation, we propose that this unusual nanocrystallinity transition induced by surfactant exchange was resulted from a counterbalance between the surfactant binding energy and the nanocrystal adhesive energy. The findings represent a novel postsynthetic approach to tailoring the structure and corresponding functional performance of nanomaterials.     

Controlled synthesis of uniform cobalt phosphide hyperbranched nanocrystals using tri-n-octylphosphine oxide as a phosphorus source

A new method to produce hyperbranched Co(2)P nanocrystals that are uniform in size, shape, and symmetry was developed. In this reaction tri-n-octylphosphine oxide (TOPO) was used as both a solvent and a phosphorus source. The reaction exhibits a novel monomer-saturation-dependent tunability between Co metal nanoparticle (NP) and Co(2)P NP products. The morphology of Co(2)P can be controlled from sheaflike structures to hexagonal symmetric structures by varying the concentration of the surfactant. This unique product differs significantly from other reported hyperbranched nanocrystals in that the highly anisotropic shapes can be stabilized as the majority shape (>84%). This is the first known use of TOPO as a reagent as well as a coordinating background solvent in NP synthesis.     

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.     

表面活性剂在纳米材料形貌调控中的作用及机理研究进展

介绍了表面活性剂在纳米材料合成中的软模板作用和稳定分散作用,重点综述了利用表面活性剂在溶液中聚集形成的胶团、反胶团、微乳液、囊泡、液晶等各种有序聚集体辅助制备纳米材料的作用机理.展望了表面活性剂在纳米材料形貌调控中的应用前景.