亲油性金纳米粒子的合成

利用相转移法成功地合成了粒径在2～7nm的硫醇表面修饰Au纳米粒子.采用透射电子显微镜、纳米粒度分布仪、红外光谱分析仪等现代测试技术对所合成的Au纳米粒子进行了表征.结果表明,表面为硫醇所修饰的Au纳米粒子,在有机溶剂中具有很好的分散性,表面修饰层的存在不仅有效地阻止Au纳米粒子的团聚,而且使得纳米粒子粒径分布窄,粒径可控.     

原位表面修饰纳米CdS粒子的表面结构和光学性能

采用微乳液法合成了纳米尺度硫化镉粒子,并用硫醇和咪唑对粒子进行了原位表面修饰.对纳米硫化镉粒子的形貌与表面结构进行了表征,证实了表面修饰剂与粒子间的键合.电镜观察和紫外-可见吸收光谱的测定发现,表面修饰明显地提高了纳米粒子在溶剂中的分散性,改变了纳米粒子的表面结构,消除了粒子表面导致无辐射弛豫的缺陷,因而提高了纳米粒子分散于溶剂体系的荧光性能.修饰剂与溶剂间的相互作用决定了表面修饰粒子在溶剂中的分散性,对纳米粒子的光学性能也有一定的影响.     

联氨还原法制备铜纳米粒子

在表面活性剂聚乙烯吡咯烷酮(PVP)的保护下,采用水合肼于水体系中还原铜盐而得到铜纳米粒子。通过XRD检验确认该种方法合成的铜纳米粒子具有fcc相;XPS的表征结果显示:铜纳米粒子表面价态为零价,说明制备过程中没有被氧化;用透射电镜和激光光散射仪对粒子的表面形貌和粒径进行了表征分析,结果显示粒径在35nm左右,近似圆球形,在正己烷中分散效果较好。     

微波辐射在联氨还原法制备金属Co纳米微粒中的应用

采用次亚磷酸钠为辅助还原剂,联氨为主还原剂,在微波辐射下还原钴盐制备六方结构o纳米粒子.采用透射电子显微镜和激光散射仪观察并测定纳米Co粒子的形貌、粒径大小及分布,确认Co纳米粒子为类球形,粒径为10～15nm.在正己烷中存在软团聚,团聚体平均尺寸约30nm.采用XPS考察产物的表面价态,证明金属Co纳米晶是以零价态存在的.     

硬脂酸对CeO2纳米粒子的表面修饰研究

利用表面修饰法合成了硬脂酸修饰的 CeO2 纳米粒子,采用透射电子显微镜(TEM)观察了经表面修饰的CeO2 纳米粒子的形貌及分散性,并采用红外光谱(IR)、紫外可见分光光度计等对修饰的CeO2 纳米粒子进行了表征。结果表明:表面修饰剂硬脂酸与 CeO2 纳米粒子表面之间发生了化学键合作用;修饰后的CeO2 纳米粒子表面存在疏水有机基团,阻隔了 CeO2 纳米粒子的团聚,起到了分散作用;同时,修饰后的CeO2 纳米粒子在苯乙烯中的稳定性得到了提高。并且获得了硬脂酸的修饰量与CeO2 纳米粒子的最佳配比。     

聚苯乙烯/纳米SiO2复合颗粒制备与表征

为改善二氧化硅(SiO2)纳米粒子与聚合物基体间的亲和性,使SiO2表面功能化,将硅烷偶联剂KH-570引入C=C基团,采用乳液聚合方法在纳米SiO2粒子表面接枝苯乙烯(St)单体,实现了纳米二氧化硅表面的聚苯乙烯(PS)高分子包覆改性,制备了具有核/壳结构的SiO2-PS复合纳米粒子,产物的单体转化率和接枝效率在80%以上.研究了二氧化硅含量和偶联剂用量对聚合反应的单体转化率和接枝效率的影响,探讨了偶联剂的作用机理,利用FT-IR、TEM、TG对SiO2-PS复合粒子的表面结构进行了表征.结果表明,复合粒子具有明显的核壳结构,壳层厚度在20nm左右,乳液聚合过程可有效使二氧化硅的团聚体剥离呈纳米级颗粒.     

无机纳米粒子表面修饰

在讨论无机纳米粒子团聚机理的基础上综述了纳米粒子表面修饰研究进展。表面修饰包括物理和化学修饰,重点综述了表面聚合物修饰最新研究进展。介绍了以化学键在纳米粒子表面接枝聚合物,其主要方法包括在无机纳米粒子表面引入可聚合碳-碳双键合成大分子单体、此大分子单体与相应乙烯基单体共聚在表面生成聚合物;将引发剂"固定"在纳米粒子表面合成大分子引发剂,以此引发剂引发单体聚合物生成表面接枝聚合物;反应型聚合物链与粒子表面活性基团反应将聚合物链接枝到纳米粒子表面。     

亲油性纳米TiO2／PMMA复合粒子的制备及表征

采用种子乳液聚合法对纳米TiO2进行表面改性,将甲基丙烯酸甲酯包覆在纳米TiO2表面,形成TiO2/PMMA复合粒子。采用FT-IR、UV-Vis、XPS、TEM等分析手段对所得产物的表观形貌、所携带官能团、表面元素变化和在有机溶剂中的分散性等进行了表征。结果表明,复合粒子呈现核壳结构,粒子的团聚现象和分散性都得到改善,亲油性增强。     

前驱体对纳米AlOOH水热制备过程中团聚的影响

为了提高水热产物的分散性,消除水热合成过程中纳米AlOOH颗粒的软团聚和硬团聚,采用振动搅拌的方式制备了前躯体,在水热合成之前进行了离心处理,制备了分散性良好的纳米AlOOH晶粒。用高分辨透射电镜观察了样品形貌,用衍射仪分析了纳米AlOOH晶体点阵结构,用亚微米粒度及电位分析仪检测产物颗粒的表观团聚平均粒径及其分布,以此评价颗粒的团聚行为。通过分析研究探讨了前躯体制备方式对水热产物形貌的影响机理,揭示了化学位差和纳米粒子具有的较高的表面能是导致软团聚的根本原因,指出了杂质离子在结晶过程中的极性配位是导致硬团聚的实质所在。     

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.     

Structure determination of chitosan-stabilized Pt and Pd based bimetallic nanoparticles by X-ray photoelectron spectroscopy and transmission electron microscopy

Chitosan (CTS)-stabilized bimetallic nanoparticles were prepared at room temperature (rt.) in aqueous solution. Palladium (Pd) and platinum (Pt) were selected as the first metals while iron (Fe) and nickel (Ni) functioned as the second metals. In order to obtain the noble metal core-transition metal shell structures, bimetallic nanoparticles were prepared in a two-step process: the preparation of mono noble metallic (Pd or Pt) nanoparticles and the deposition of transition metals (Fe or Ni) on the surface of the monometallic nanoparticles. The structures of the nanoparticles were studied using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XPS results show that Pd and Pt exist mainly in zero valences. The presence of Fe and Ni in the bimetallic nanoparticles affects the binding energy of Pd and Pt. Moreover, the studies of O 1s spectra indicate the presence of Fe or Ni shells. The analyses of TEM micrographs give the particle size and size distributions while the high-resolution TEM (HRTEM) micrographs show the existence of noble metal core lattices. The results confirm the formation of noble metal core-transition metal shell structures.     

Carbon-supported AuPd bimetallic nanoparticles synthesized by high-energy electron beam irradiation for direct formic acid fuel cell

Nanoparticle catalysts of carbon-supported Pd (Pd/C) and carbon-supported AuPd (AuPd/C) for the direct formic acid fuel cell (DFAFC) anode were synthesized by the reduction of precursor ions in an aqueous solution irradiated with a high-energy electron beam. We obtained three kinds of nanoparticle catalysts: (1) Pd/C, (2) AuPd/C of the core–shell structure, and (3) AuPd/C of the alloy structure. The structures of AuPd nanoparticles were controlled by the addition of citric acid as a chelate agent, and sodium hydroxide as a pH controller. The structures of nanoparticle catalysts were characterized using transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, the techniques of X-ray diffraction and X-ray absorption fine structure. The catalytic activity of the formic acid oxidation was evaluated using linear sweep voltammetry. The oxidation current value of AuPd/C was higher than that of Pd/C. This indicated that the addition of Au to Pd/C improved the oxidation activity of the DFAFC anode. In addition, the AuPd/C of the alloy structure had higher oxidation activity than the AuPd/C of the core–shell structure. The control of the AuPd mixing state was effective in enhancing the formic acid oxidation activity.     

Microwave irradiation assisted rapid synthesis of Fe-Ru bimetallic nanoparticles and their catalytic properties in water-gas shift reaction

Fe-Ru bimetallic nanoparticles were prepared by a microwave irradiation assisted glycol reduction method using poly-N-vinyl-2-pyrrolidone (PVP) as protective agent. The structure and morphology of the nanoparticles were characterized by X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDXA) and high-resolution transmission electron microscopy (HRTEM). EDXA and XRD analysis confirmed the presence of Fe and Ru. The bimetallic nanoparticles were subsequently loaded onto an MgAl₂O₄ supporter with K₂O as promoters and used as catalyst for water-gas shift reaction. The results indicated that the FeRu bimetallic nanoparticles exhibit high catalytic activity for water-gas shift reaction due to the synergistic effect between iron and ruthenium. Potassium oxide can enhance the CO selectivity of the catalyst significantly besides increasing the catalyst activity.     

Preparation of ultrafine chalcopyrite nanoparticles via the photochemical decomposition of molecular single-source precursors

The synthesis and characterization of ultrafine CuInS2 nanoparticles are described. Ultraviolet irradiation was used to decompose a molecular single source precursor, yielding organic soluble approximately 2 nm sized nanoparticles with a narrow size distribution. UV-vis absorption, 1H and 31P{1H} NMR, and fluorescence spectroscopies and mass spectrometry were used to characterize decomposition of the precursors and nanoparticle formation. The nanoparticles were characterized by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy energy dispersive X-ray spectroscopy, powder X-ray diffraction (XRD), electron diffraction, inductively coupled plasma analysis, UV-vis absorption spectroscopy, and fluorescence spectroscopy. They have a wurzite-type crystal structure with a copper-rich composition. The hypsochromic shift in their emission band due to quantum confinement effects is consistent with the size of the nanocrystals indicated in the HRTEM and XRD analyses.     

Radiation induced synthesis of Au-Pd nanoparticles of random alloy structure supported on carbon particles using the high energy electron beam

Au-Pd bimetallic nanoparticles supported on carbon particles were synthesized by reduction of precursor ions in an aqueous solution irradiated with a high energy electron beam. The composition of the samples was analyzed by the inductively coupled plasma atomic emission spectrometry (ICP-AES), and the morphology of the samples was observed by the transmission electron microscope (TEM). TEM micrographs indicated that Au-Pd particles of ca. 5-nm were well dispersed on the surface of carbon particles of ca. 30-nm without any serious agglomeration. Addition of citric acid to the initial solution and high pH were found to be effective for formation of random alloy structure in the resultant bimetallic nanoparticles. The change in the bimetallic structure from core-shell to random alloy was identified by techniques of the X-ray diffraction (XRD) and the extended X-ray absorption fine structure (EXAFS).     

Structural and morphological characterization of cerium oxide nanocrystals prepared by hydrothermal synthesis

Colloidal cerium oxide (CeO2) nanocrystals prepared by hydrothermal synthesis were characterized by high-resolution transmission electron microscopy (HRTEM) and three-dimensional electron tomography (3D-ET). HRTEM images of individual CeO2 nanocrystals were then simulated by Blochwave and multislice simulations to determine the atomic arrangement and terminating atoms. The edge length distributions were between 5.0 and 8.0 nm with an average edge length of 6.7 nm. The HRTEM images showed that the CeO2 particles were slightly truncated revealing {220} facets. 3D-ET revealed that the CeO2 nanocrystals exposed predominantly {200} cubic facets. The nanocrystals were truncated at the corners exposing {111} octahedral facets and at the edges {220} dodecahedral facets. Furthermore, 3D-ET revealed the presence of some tetragonal-shaped CeO2 nanocrystals.     

Formation of fractal structures from silicon dioxide nanoparticles synthesized by RF atmospheric pressure plasma enhanced chemical vapor deposition

Fractal structures were formed on silicon substrates from SiO2 nanoparticles homogeneously synthesized in low temperature atmospheric pressure plasma from tetraethoxysilane (TEOS). RF discharge (power absorbed was about 10 W) sustained between two parallel mesh electrodes was used to generate plasma. The average size of nanoparticles was in the range of 8-20 nm and was determined by process parameters. The obtained products were analyzed by SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectroscopy). Values of fractal dimension parameter of bidimensionals agglomerates formed on the substrate surface from nanoparticles were calculated with the use of Gwyddion and others. It was found that values of this parameter of the deposited structures varied in the range of 1.48-2 and were determined by combination of the process parameters. An empirical model explaining mechanism of the fractal structures formation and variation of the fractal dimension parameter with the process parameters was proposed.     

Electrocatalytic applications of platinum-decorated TiO<Subscript>2</Subscript> nanotubes prepared by a fully wet-chemical synthesis

Pt-decorated \(\hbox {TiO}_{2}\) nanotubes Pt@TiO₂ are prepared only by applying a set of facile wet-chemical redox reactions to ion track-etched polycarbonate templates. First, a homogeneous layer of Pt nanoparticles is deposited onto the complex template surface by reducing potassium tetrachloroplatinate with absorbed dimethylaminoborane. Second, the template is coated with a conformal \(\hbox {TiO}_{2}\) layer, using a chemical bath deposition reaction based on titanium(III) chloride. After the removal of the template, the rutile-type \(\hbox {TiO}_{2}\) nanotubes remain decorated with Pt nanoparticles and nanoparticle-clusters on their outside. During the process, neither vacuum techniques nor external current sources or addition of heat are employed. The crystallinity, composition, and morphology of the composite nanotubes are analysed by X-ray diffraction, scanning and transmission electron microscopy as well as by energy-dispersive X-ray spectroscopy. Finally, the obtained materials are examplarily applied in the electrooxidation of ethanol and formic acid, and their performances have been evaluated. Compared to conventional carbon black-supported Pt nanoparticles, the Pt@TiO₂ nanotubes show higher reaction rates. Mass activities of 2.36 \(\hbox {A}\hbox { mg}_{\rm Pt}^{-1}\hbox { cm}^{-2}\) are reached in ethanol oxidation and 7.56 \(\hbox {A}\hbox { mg}_{\rm Pt}^{-1}\hbox { cm}^{-2}\) in the formic acid oxidation. The present structures are able to exploit the synergy of Pt and \(\hbox {TiO}_{2}\) with a bifunctional mechanism to result in powerful but easy-to-fabricate catalyst structures. They represent an easily producible type of composite nanostructures which can be applied in various fields such as in catalytics and sensor technology.     

AuCl4 ions-assisted fabrication of bimetallic {Poly(ethylenimine)-Ag/Au} multilayer polyelectrolyte film and application in electrocatalysis

Bimetallic {Poly(ethylenimine) (PEI)-Ag/Au} multilayer film was in situ simultaneously fabricated by alternating immersions of a substrate in PEI-Ag⁺ and AuCl₄⁻ solutions followed by chemical reduction with NaBH₄ solution. In the process, the AuCl₄⁻ ions not only play an important role of a reaction reagent, but also served as an assembly reagent. Au, Ag nanoparticles (NPs) were observed with a spherical morphology and well-dispersed in the composite multilayer film, and the size of Au NPs in the bimetallic {PEI-Ag/Au} multilayer film was smaller than that of the single Au NPs formed in {PEI/Au} multilayer films. It was also very interesting to observe that this bimetallic {PEI-Ag/Au} multilayer film exhibited more efficient electrocatalytic activity for the oxidation of ascorbic acid than the multilayer film containing only single Au or Ag NPs. These results indicated that this bimetallic composite multilayer film may be potentially applied in electrochemical biosensors.     

Fabrication of PtNi bimetallic nanoparticles supported on multi-walled carbon nanotubes

Platinum/nickel bimetallic nanoparticles supported on multi-walled carbon nanotubes (xPtNi/CNTs) were synthesised. The fabrication process includes the chemical modification on the graphene surface of CNTs by acid treatment and the subsequent deposition of Pt or PtNi bimetallic nanoparticles with different compositions of Pt (x = 100, 90, 80 and 70 wt%). The deposition was carried out using ethylene glycol as a reducing agent in the polyol method or using poly(amidoamine) dendrimer as a platform and sodium borohydride as a reducing agent to load the metal nanoparticles on the CNT surface. The structures of the produced PtNi/CNT nanoparticles were investigated by ultraviolet absorption spectra, X-ray diffraction (XRD) and the composite ratio consisting of 70 wt% of metal content and 30 wt% of CNTs was confirmed by the thermogravimetric analysis. The morphology and the phase identification of the produced PtNi/CNT nanoparticles were investigated by high-resolution scanning electron microscope, transmission electron microscope and XRD measurements. It was observed that the deposited Pt and PtNi bimetallic nanoparticles on the surface of CNTs had average particle sizes of 2–16 nm, when they were prepared from the polyol method. On the other hand, the PtNi/CNT nanoparticles prepared by using a dendrimer as an intermediate had a smaller particle size and more uniform size distribution of the quantum dot size ranged from 2 to 4 nm.