金核/铂壳纳米粒子的光化学合成及电催化活性

在含不同摩尔比的Au(Ⅲ)和Pt(Ⅳ)离子的PEG(聚乙二醇)-丙酮溶液中,采用光化学共还原法合成了一组Au@Pt复合纳米粒子,并以炭黑分别对其负载制成Au@Pt/C催化剂。借助于UV-Vis、TEM和HR-TEM的表征,证实复合纳米粒子为球形的核/壳结构;分别以XPS、EDS和电化学方法分析了复合粒子的化学状态、结构特点和Au@Pt/C催化剂的催化性质。结果表明,不同Au:Pt摩尔比的Au@Pt/C催化剂对甲醇氧化反应具有良好的催化活性和稳定性,其中Au:Pt=1:1时形成的Au@Pt/C催化剂电催化活性最高,约为商品Pt/C催化剂的4倍。简要讨论了核/壳结构产生高催化活性的主要原因。     

在柠檬酸盐溶液体系中金核@铂壳纳米粒子的光化学合成

在含有不同Au:Pt摩尔比的双金属离子和单一Pt(Ⅳ)离子的柠檬酸盐溶液体系中,分别利用光化学共还原和Au晶种生长法合成了Au核@Pt壳纳米粒子。借助于透射电子显微镜的表征,研究了在2种制备方法中复合纳米粒子的尺寸变化规律;利用X射线光电子能谱(XPS)分析了复合纳米粒子的表面化学态和它们的结构,证实形成的Au@Pt纳米粒子为核-壳结构。     

金银复合纳米微粒的光学吸收特性

以NaHB4做还原剂,利用一步共还原氯金酸(HAuCl4)和硝酸银(AgNO3)制备了金银复合结构的纳米颗粒。用透射电子显微镜对所制备的金银复合纳米微粒的形貌和尺寸进行了表征。紫外可见光学吸收光谱的研究表明:通过一步共还原法所制备的金银复合纳米微粒的光学吸收谱具有单峰的等离子体吸收特征,其吸收峰介于纯金和纯银纳米颗粒特征吸收峰之间,且随着反应液中金离子和银离子的摩尔比的增加而向长波方向移动。Mie散射理论的定量计算结果同样说明了实验所观察到的金银复合纳米微粒的光学吸收的组分可剪裁性。     

Monte Carlo simulations of the structure of Pt-based bimetallic nanoparticles

Pt-based bimetallic nanoparticles have attracted significant attention as a promising replacement for expensive Pt nanoparticles. In the systematic design of bimetallic nanoparticles, it is important to understand their preferred atomic structures. However, compared with unary systems, alloy nanoparticles present greater structural complexity with various compositional configurations, such as mixed-alloy, core–shell, and multishell structures. In this paper, we developed a unified empirical potential model for various Pt-based binary alloys, such as Pd–Pt, Cu–Pt, Au–Pt and Ag–Pt. Within this framework, we performed a series of Monte Carlo (MC) simulations that quantify the energetically favorable atomic arrangements of Pt-based alloy nanoparticles: an intermetallic compound structure for the Pd–Pt alloy, an onion-like multishell structure for the Cu–Pt alloy, and core–shell structures (Au@Pt and Ag@Pt) for the Au–Pt and Ag–Pt alloys. The equilibrium nanoparticle structures for the four alloy types were compared with each other, and the structural features can be interpreted in terms of the interplay of their material properties, such as the surface energy and heat of formation.     

Fe—B／Fe3O4纳米复合粒子的吸波性能研究

采用NaBH4溶液还原FeCl3的方法制备Fe-B颗粒,并在Ar／O2气氛下干燥,使其表面不完全氧化,得到了Fe—B／Fe3O4纳米复合粒子。该粒子具有清晰的核壳结构,内核Fe-B尺寸约为20－50nm,外壳Fe3O4厚度约为3nm。将样品与石蜡按质量比1：1制成同轴样品,测试其2～18GHz下的电磁参数并进行分析计算,研究发现,由于偶极子极化、自然共振和涡流损耗,该纳米复合粒子粉末具有优良的吸波性能,其反射损耗RL在频率为12．0GHz的时候达到最小值－31dB,RL值低于－20dB（即吸收率高于99％）的频率范围为10．1～14．2GHz。     

Preparation of novel core-shell nanoparticles by electrochemical synthesis

Nanostructural gold/polyaniline core/shell composite particles on conducting electrode ITO were successfully prepared via electrochemical polymerization of aniline based on 4-aminothiophenol （4-ATP） capped Au nanoparticles. The new approach to the fabrication included three steps： preparation of gold nanoparticles as core by pulse electrodeposition; formation of ATP monolayer on the gold particle surface, which served as a binder and an initiator; polymerization of aniline monomer initiated by ATP molecules under controlled voltage lower than the voltammetric threshold of aniline polymerization, which assured the formation of polyaniline shell film occurred on gold particles selectively Topographic images were also studied by AFM, which indicated the diameter of gold nanoparticles were around 250 run. Coulometry characterization confirmed the shell thickness of polyaniline film was about 30 nm A possible formation mechanism of the Au/polyaniline core-shell nanocomposites was also proposed. The novel as-prepared core-shell nanoparticles have potential application in constructing biosensor when bioactive enzymes are absorbed or embedded in polyaniline shell film.     

Room temperature synthesis of Ag/polypyrrole core–shell nanoparticles and hollow composite capsules

Two kinds of Ag/polypyrrole composite nanoparticles have been prepared via a one-step redox reaction between silver nitrate and pyrrole monomer at room temperature. One is Ag@polypyrrole core–shell nanoparticles that were synthesized by making use of synergic inducing effect of polyvinyl pyrrolidone and p-toluenesulfonic acid existing in aqueous solutions. The other is AgCl@Ag/polypyrrole core–shell composite nanoparticles that were synthesized in the presence of HCl using the in situ-formed AgCl particles as the template. For the latter, its core can be easily removed via a simple dissolving procedure in sodium hyposulfite or ammonium chloride aqueous solutions, obtaining the Ag/polypyrrole hollow composite capsules. Experimental results suggest that the shell thickness and core diameter of the resulting composites can be controlled expediently by adjusting reaction time and concentration of pyrrole monomer.     

Fabrication and characteristics of spindle Fe2O3@Au core/shell particles

The fabrication and characteristics of spindle Fe2O3@Au core/shell particle were investigated, and the effect of the core/shell nanoparticles as the surface enhanced Raman spectroscopy (SERS)-active substrates was studied. By using the seed-catalyzed reduction technique, anisotropic Fe2O3@Au core/shell particles with spindle morphology were successfully prepared. The Fe2O3 particles with spindle morphology were initially prepared as original cores. The Au nanoparticles of 2 nm were attached onto the Fe2O3 particles through organosilane molecules. Uniform Au shell formed onto Fe2O3 core modified by Au nanoparticles through the in-situ reduction of HAuCl4. The shell thickness was controlled through regulating the concentration of HAuCl4 solution. The results of TEM, XRD and UV-vis characterization show that the core/shell particles with the original shape of the Fe2O3 particles are obtained and these surfaces are covered by Au shell completely. The surface enhanced Raman spectrum of the probe molecules adsorbed on these core/shell substrates is strong and the intensity is enhanced with the increase of the thickness of Au shell or the aspect ratio of particles. The spindle Fe2O3@Au core/shell particles exhibit optimum (SERS) activity.     

逐步生长法制备银纳米颗粒及其表面改性研究

利用逐步生长法制备出了一系列具有不同几何尺度的银纳米颗粒并利用正硅酸乙酯的水解,引入偶联剂,对银纳米颗粒进行表面改性,制备出具有包覆层(SiO_2)和中心核(Ag)的复合纳米结构.确定了获得良好性能材料的最佳合成条件,系统研究了这些银纳米和核壳结构的特征、结构形成的材料学原因和光学性质.     

核-壳结构Ag-Au纳米颗粒合金化行为的分子动力学

利用分子动力学方法和改进分析型嵌入原子势函数模拟了核-壳结构Ag-Au纳米颗粒的合金化行为,从原子扩散、微观结构演变以及合金化程度等方面对比分析了壳层厚度对合金化行为的影响。结果表明,壳层较薄时,核-壳界面处原子扩散现象显著,内核表现出多面体形貌,表层Au、Ag原子完全混合。壳层较厚时,表面原子以扩散为主,整个颗粒表面为多面体结构,但内核保持初始球状结构。通过层错生长方式使形貌发生了改变。壳层越薄,体系合金化程度越高     

Ag/Au-decorated Fe3O4/SiO2 composite nanospheres for catalytic applications

Noble metal particles in nanoscale (Au, Ag, Pt, etc.) have attracted intensive research interest due to their promising catalysis properties. However, the practical applications of these nanoparticle catalysts are always jeopardized by two problems. One is the difficulty in recovering the used nanoparticles and the other arises from the low catalytic efficiency due to the aggregation of the nanoparticles. In this work, Ag/Au nanoparticles were distributed onto spherical superparamagnetic carriers (SSCNs), which were fabricated through a facile oil-in-DEG emulsion route. The Ag/Au nanoparticles were attached onto the SSCNs by two steps. The Au seeds were attached onto the silica surface through electrostatic attraction first, and the Ag nanoparticles were grown on the basis of the Au seeds. The obtained Ag/Au–SSCN composite nanospheres demonstrated promising catalytic properties, which could also be recycled very easily by using a magnet.     

棒状金纳米粒子的制备及其光谱特性

以银离子为辅助粒子,十六烷基三甲基溴化铵(CTAB)为表面活性剂,抗坏血酸为弱还原剂,利用晶种法制备棒状金纳米粒子,着重研究晶种用量与氯金酸量的比例对棒状纳米粒子形状和产率的影响。利用透射电子显微镜（TEM）和X射线衍射（XRD）仪对纳米粒子的形貌及晶体结构进行分析,利用紫外可见光谱（UV-Vis）对产物进行光谱表征。结果表明,纳米棒为面心立方结构,其UV-Vis出现位于530 nm处的短波吸收和970~980 nm的长波吸收,随着晶种与氯金酸用量比例的增加,纳米棒的长径比出现先增大后减小的趋势,并最终形成球形颗粒。最后探讨晶种用量影响金纳米棒生长的机制。     

同步合成硒化银-聚苯胺纳米核壳结构及其热电性能

在室温下通过界面法合成硒化银-聚苯胺纳米复合颗粒。粉末X-射线衍射分析与红外分析证实了样品的相组成,透射电子显微镜观察表明复合颗粒为核壳结构:衬度较浅的聚苯胺为壳而衬度较深的硒化银为核。对硒化银-聚苯胺纳米核壳结构的形成机理做了探讨。所得粉末经冷压成型后测试其热电性能,常温下样品的电导率和Seebeck系数分别为5.5S·m-1和179μV·K-1。     

原位一步法合成Ag/Fe2O3磁性核壳纳米粒子

采用原位法在低温下一步合成Ag/Fe2O3磁性核壳纳米粒子,并采用XRD,TEM和UV光谱研究了Ag-Fe2O3核壳纳米复合材料的结构。结果表明,纳米银粒子表面被Fe2O3层包覆,Ag核的平均粒径大约为35nm,Fe2O3壳层平均厚度约为7.5nm或15nm,形成了核壳结构的电磁复合纳米粒子。在室温下,饱和磁化强度达到0.98(A·m2)·kg-1,矫顽力8.48×103A/m;Ag/Fe2O3核壳粒子的导电率达到0.62S/cm。通过此法可以比较容易的控制核和壳的尺寸以及复合粒子的单分散性,并得到较高的产率,在催化剂、医药、光电等领域有着广阔的应用前景。     

Synthesis and characterization of the core–shell Au covered LSMO manganite magnetic nanoparticles

In this work we report the synthesis and characterization of the nanomagnetic perovskite Sr manganites covered with Au shells having different thickness. La_2/3Sr_1/3MnO₃ (LSMO) manganite nanoparticles were first prepared by a sol–gel procedure. The LSMO manganite nanoparticles were chemically covered with gold to produce the core–shell samples. TEM, HRTEM and atomic emission spectroscopy techniques were used to determine the morphology and structure of the LSMO@Au nanoparticles. The bare LSMO nanoparticles have a mean diameter of around 4.4 nm while LSMO@Au nanoparticles have mean diameters between 7.15 and 4.8 nm depending on the gold quantity involved in the capping process. XRD studies show that both core and shell systems have the expected crystalline structure. The formation of the core–shell structure is sustained by the shift of the plasmon resonance wavelength maximum observed in the UV–vis absorbtion spectra of the LSMO@Au samples depending on the gold concentration. The magnetization versus applied magnetic field of the bare LSMO nanoparticles and LSMO@Au samples shows no hysteresis loop indicating the superparamagnetic behavior of these systems. The analysis of the temperature dependences of FC and ZFC magnetizations shows that for all the samples the axial anisotropy energy barriers are increased due to the magnetic dipolar interactions between neighbor nanoparticles.     

金芯-银壳复合纳米微粒光学吸收光谱分析

通过液相还原法制备出金．银复合纳米颗粒。透射电镜图像显示所制备金-银复合纳米颗粒呈球状的芯-壳结构。光学吸收谱的实验表明：金芯．银壳复合结构纳米微粒具有双峰的等离子体吸收带。一个峰值的波长位于纯银纳米颗粒的等离子体吸收带附近；另一个介于纯银和纯金纳米颗粒的等离子体吸收峰之间，且随着反应试样中银的摩尔分数的增加发生蓝移，基于实验分析和Mie散射理论的定量计算。结果认为：该吸收峰的蓝移可归因于银壳层厚度的增加。     

不同壳层厚度Au@SiO_2的表面增强拉曼效应

通过电偶置换反应制备了尺寸在30~35 nm的结晶性良好的Au纳米颗粒,并成功在其表面包覆了不同厚度的Si O2壳层,利用TEM、HRTEM和UV-Vis对样品的结构和形貌进行了表征,并以罗丹明6G(R6G)为探针分子,对Au@SiO_2复合粒子的表面增强拉曼散射(SERS)效应进行了研究。结果显示,相对于Au纳米颗粒,Au@SiO_2复合粒子显著提高了拉曼信号的质量和检测的灵敏度,且Si O2壳层厚度对其SRES效应影响显著,壳层厚度为2 nm的复合粒子对R6G分子的检测极限可达10~(-7)mol/L。     

一种中空金/银双金属纳米颗粒的制备及其SERS性能

以银纳米颗粒为牺牲模板,利用Ag和HAu Cl4之间的置换反应,结合柠檬酸钠同步还原的方法制备了一种中空金/银双金属纳米颗粒。通过对颗粒形貌及局域表面等离子体共振(LSPR)的分析,初步研究了此类金/银纳米颗粒的生长机理,并对影响反应的因素进行了探讨。结果表明,通过控制反应条件可以实现对LSPR的精密调控。该类金/银双金属纳米颗粒可用作为SERS基底,苯硫酚在其表面增强因子可达107,并具有良好的信号重现性。该基底用于atto610标记的生物素与亲和素的SERS检测,检测限可达80 pg/m L。     

有机两相法制备巯基羧酸修饰的小尺寸贵金属纳米粒子

以生物相容性较好的巯基羧酸分子为保护剂、NaBH4为还原剂,采用有机两相法制备金属纳米粒子,实现了对纳米粒子的表面功能化。该方法制备的纳米材料粒径小(5 nm),单分散性好。讨论了巯基羧酸与金属前驱体之间的投料比、还原剂NaBH4的量以及巯基羧酸分子链长等因素对纳米粒子形貌的影响。除Au外,该方法还适用巯基羧酸对Ag、Pt和Pd等多种纳米粒子的表面修饰。     

Electrochemical preparation and characterization of gold-polyaniline core-shell nanocomposites on highly oriented pyrolytic graphite

A simple electrochemical method for the in situ preparation of homogeneously dispersed gold-polyaniline core/shell nanocomposite particles with controlled size on the highly oriented pyrolytic graphite(HOPG)was demonstrated.The HOPG surface was modified preferentially by covalent bonding of a two-dimensional 4-aminophenyl monolayer employing diazonium chemistry.AuCl4 -ions were attached to the Ar-NH2 termination and reduced electrochemically.This results in the formation of Au nuclei that could be further grown into gold nanoparticles.The formation of polyaniline as the shell wrap of Au nanoparticle was established by localized electro-polymerization.These core-shell nanocomposites prepared were characterized by AFM and cyclic voltammetry.The results show that the gold-polyaniline core-shell composites on HOPG have a mean particle size of 100 nm in diameter and the polyaniline shell thickness is about 15 nm.