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.     

In-situ chemical synthesis route for a fiber shaped gold-polyaniline nanocomposite

A facile synthesis route is described for the preparation of a gold-polyaniline nanocomposite material by polymerization of aniline hydrochloride using HAuCl4 as the oxidant. It was found that the oxidative polymerization of aniline hydrochloride leads to the formation of polyaniline with a fiber-like morphology, while the concomitant reduction of HAuCl₄ results in the formation of gold nanoparticles of diameter 2–7 nm. The gold nanoparticles were highly dispersed and stabilized throughout the polyaniline fibers while being in intimate contact with the polymer. The combination formed a uniform metal-polymer composite material.     

基于紫外光辐照法制备CuSe/ZnSe核壳结构纳米粒子

本文成功制备出以CuSe为核心、ZnSe为壳层,具有核壳结构的CuSe/ZnSe纳米粒子。首先采用回流冷凝法制备出CuSe纳米粒子（NPs）。然后,采用一种简单、快速的光化学方法即紫外光辐照法,室温下在CuSe NPs外包覆ZnSe壳层,最终得到CuSe/ZnSe核壳结构纳米粒子。利用X射线衍射(XRD)、能量色散谱仪(EDS)、透射电镜(TEM)、高分辨透射电镜(HRTEM)和光致发光光谱(PL)对合成的CuSe/ZnSe核壳NPs进行了表征。结果分析表明,合成的CuSe纳米粒子具有六方相结构,粒径平均大小在12 nm。制备出的CuSe/ZnSe纳米粒子的核壳结构清晰,生长的ZnSe壳层为立方闪锌矿结构,粒径大小约为15~45 nm。通过ZnSe壳层的包覆使CuSe在475 nm处产生蓝光发射,同时荧光强度显著增强。     

直流电弧等离子体制备NiO包覆Ni纳米颗粒

采用直流电弧等离子体技术制备NiO包覆Ni纳米颗粒,对初产物经过钝化处理得到有氧化膜保护的NiO包覆Ni纳米颗粒.采用高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)、透射电子显微镜(TEM)、选区电子衍射(SAED)、热重和差示扫描量热分析仪(TGA/DSC)以及傅里叶变换红外光谱 (FTIR)等手段对试样的成分、表面组成、形貌、晶体结构、粒度、红外吸收性能和氧化特性进行了分析.结果表明:经过表面钝化处理的NiO包覆Ni纳米颗粒具有明显的核-壳结构,内核为纳米Ni,外壳为NiO氧化物;颗粒呈球形,粒度均匀,分散性良好,粒径分布在20～70 nm范围,平均粒径为44 nm,壳层氧化膜的厚度为5～8 nm;壳核结构可防止纳米Ni颗粒的进一步氧化和团聚,且使红外吸收峰发生蓝移.     

ZnO-TiO_2核壳纳米线结构及其热稳定性研究

采用热还原法和原子层沉积技术制备了ZnO-TiO_2核壳纳米线,研究沉积厚度、沉积温度及退火对于ZnO-TiO_2核壳纳米线晶化和结构的影响。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨率透射电镜(HRTEM)等手段对退火前后核壳纳米线进行表征。结果表明:沉积厚度和温度的增加有利于TiO_2壳层发生非晶向晶化的转变;500℃退火提高了TiO_2的结晶性,但可能会使细核壳纳米线(ZnO纳米线直径80 nm)产生波浪形变形,使150℃沉积的非晶TiO_2壳层形成凸出晶粒,并导致其界面处ZnO缺失。     

Au核壳纳米催化剂的制备及性能研究

采用化学镀工艺,制备了催化性能优良的Au核壳结构纳米催化剂,表面Au颗粒粒径约为16nm,结构致密,单分散程度较高。利用扫描电子显微镜(SEM)和紫外-可见分光光度计(UV-Vis),结合产H2量测试,研究了络合剂和还原剂的加入顺序对Au核壳结构纳米催化剂催化性能的影响。结果表明:先加络合剂所制备样品在亚甲基蓝脱色反应中表现出最高的反应速率和产氢量,具有最高的催化反应活性。较高的纳米Au颗粒粗糙度和Au负载量是其取得优良催化活性的原因。     

Photochemical synthesis of bimetallic Au-Ag nanoparticles with "core-shell" type structure by seed mediated catalytic growth

The colloidal Au core/Ag shell structure composite nanoparticles were synthesized in PEG-acetone solution by photochemical route. The monodispersed Au nanoparticles with average diameter of 3.9 nm were used as growth seeds. The optical property of colloids and the sizes of composite nanoparticles were characterized when the molar ratio of Au to Ag ranges from 4 : 1 to 1 : 4. The results show that a composite nanoparticle structure similar to strawberry shape is formed at the molar ratio of Au to Ag from 4 : 1 to 1 : 1; the composite nanoparticles consisting of a core of Au and shell of Ag were generated at the 1: 4 molar ratio, having a striking feature of forming interconnected network structure.     

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.     

AuCu双金属纳米颗粒的制备、表征及性能探究

采用水热法制备AuCu双金属纳米颗粒,并用X射线衍射(XRD)、透射电镜(TEM)和紫外可见光谱(UV-Vis)进行表征,初步研究了其对4-硝基苯酚(4-NP)还原的催化性能和光热效应。结果表明,制备时不同的AuCl_4~-/Cu~(2+)摩尔比(r_(Au))可以调控AuCu双金属纳米颗粒的组分和形貌,XRD和吸收光谱特征随r_(Au)的增加表现出更明显的金的特征,r_(Au)0.5时得到的颗粒具有典型的核-壳结构;核-壳结构的AuCu双金属纳米颗粒对4-NP还原表现出更好的催化活性,受光热效应影响,532 nm激光照射能够加强催化活性;在激光辐射作用下,不同AuCu双金属纳米颗粒具有相似的光热效应。     

Silk fibroin fibers supported with high density of gold nanoparticles: fabrication and application as catalyst

Silk fibroin (SF) fibers were modified with sulfonated polyaniline and, via an in situ redox technique, a high density of gold (Au) nanoparticles were supported directly on the surface of the fiber. The morphology, formation, and application of the as-prepared product, Au/SPANI-modified SF composite fiber, were investigated. By controlling the concentration of HAuCl₄, the density of Au nanoparticles on the composite fiber could be effectively adjusted. It is suggested that sulfonated polyaniline contributes to the generation of a high density of Au nanoparticles supported on the SF fibers. The composite fiber exhibited good activity when taking the reduction of p-nitrophenol as a model reaction.     

PS@Au核壳复合粒子的可控合成及粒径对催化性能的影响

采用适当的化学镀工艺,通过对核层聚苯乙烯微球粒径的调制,可控合成了粒径连续可调的PS@Au核壳复合粒子,其球形度较高,无团聚,催化活性优良。利用SEM、XRD和UV-Vis,结合催化性能测试,研究了粒径对PS@Au核壳复合粒子催化性能的影响。结果表明:PS@Au核壳复合粒子较大的比表面积是其取得优良催化性能的物理本质,此外,粒径对其表面微观形貌、Au纳米粒子的生长方式及其催化性能都有显著影响。粒径较小时,核层曲率较大,Au纳米粒子呈发散式生长,表现出孤立的纳米颗粒状结构。此时,比表面积和表面能最大,催化活性最高。随着粒径增大,曲率逐渐减小,Au纳米颗粒表现出近似的薄膜状结构,比表面积和表面能逐渐降低,催化性能逐渐下降。核壳复合粒子的粒径达到400 nm时,Au纳米粒子的表面形貌开始由孤立的颗粒状结构向连续薄膜状过度。     

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。     

pH值对CeO2/SiO2纳米复合磨粒分散性的影响

以胶体SiO₂溶液作硅源,采用均相沉淀工艺制备壳-核结构完整的CeO₂/SiO₂纳米复合磨粒。采用X射线衍射仪和透射电子显微镜对复合磨粒样品进行物相组成分析和微观形貌观察;通过粒径分布、Zeta电位分析,研究水相分散系中pH值对CeO₂/SiO₂复合磨粒分散性的影响。结果表明:所制备的CeO₂/SiO₂复合磨粒为壳-核包覆结构完整的纳米微球,粒径约110 nm,内核为无定形SiO₂,壳层为立方萤石型CeO₂;CeO₂/SiO₂复合磨粒的等电位点pH值约为5,其值由SiO₂等电位点向CeO₂等电位点明显偏移。CeO₂/SiO₂复合磨粒在酸性水相介质中分散性差,容易出现严重的团聚现象;而在碱性环境下,CeO₂/SiO₂复合磨粒分散性良好。      

TiO2/SiOx core-shell nanowires generated by heating the multilayered substrates

By heating Au/TiN/Si substrates, we fabricated TiO₂/SiO_x core-shell nanowires. By changing the thickness of predeposited Au layers, we demonstrated that the thickness of the Au layer needs to be optimized to obtain nanowires. High-resolution transmission electron microscopy image, X-ray diffraction spectrum, and selected area electron diffraction pattern coincidentally revealed that the resultant core nanowires had a tetragonal rutile structure of TiO₂, and the shell was comprised of amorphous SiO_x. The dominant growth mechanism was a base-growth mode, in which Au played a catalytic role, resulting in morphological changes with variation of the Au layer thickness. The TiO₂/SiO_x core-shell nanowires exhibited a broad photoluminescence emission band, which comprised four peaks centered at 1.54, 2.34, 2.67, and 2.99 eV, respectively. We expected that the 1.54 eV- and 2.34 eV-centered peaks arised from the TiO₂ core, whereas the 2.67 eV- and 2.34 eV-peaks were ascribed to both the TiO₂ core and the SiO_x shell.     

A catalytic oxidation approach to coat copper powder with polyaniline

To improve the oxidation resistance of fine copper powder, a new catalytic oxidation method was used to coat copper microparticles with polyaniline. In the method, some copper on the surface of copper particles was converted into Cu²⁺, and with the catalysis of Cu²⁺ aniline was oxidized by hydrogen peroxide to form the polyaniline coating layer on copper particles. Detected by field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), it is proved that the composite particles have fine core-shell structure, their core are copper particles and their shell are mainly composed of compact polyaniline. The stability of the composites was tested by Thermogravimetric Analyzer (TGA) in nitrogen and in air. It is found that the particulate composite is more stable than copper particles in air.     

Synthesis of metal–carbon nanocomposites containing nanoparticles of transition metals encapsulated in a graphite-like shell

It was shown that methane decomposition on metal–carbon nanocomposites with transition metal (Co, Fe, and Ni) nanoparticles distributed in the bulk of the amorphous carbon matrix leads to carbon deposition with the formation of a graphite-like shell around a metal core. The resulting “core-shell” structures have a diameter of 10–40 nm and contain up to 50 graphene layers with an interlayer distance of 0.34–0.35 nm. For the synthesis of the initial metal–carbon nanocomposites, a method that we proposed earlier was used, which involves low-temperature formation of carbon structures from carbon-chain chloropolymers based on their dehydrochlorination with the formation of polyvinylenes as reactive carbon precursors.     

Superparamagnetic CoFe_2O_4@Au with High Specific Absorption Rate and Intrinsic Loss Power for Magnetic Fluid Hyperthermia Applications

CoFe_2O_4 nanoparticles(NPs) and surface modified with gold(Au) have been synthesized by a thermal decomposition method. The obtained NPs and formation of CoFe_2O_4@Au core–shell(CS) were confirmed by characterizing their structural and optical properties using X-ray powder diffraction(XRD) patterns, Fourier transform infrared spectroscopy,Raman spectroscopy, UV–Visible and photoluminescence studies. Morphological and compositional studies were carried out using high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy, while the magnetic properties were determined using alternating gradient magnetometer and Mossbauer to define the magneto-structural effects of shell formation on the core NPs. Induction heating properties of CoFe_2O_4 and CoFe_2O_4@Au CS magnetic nanoparticles(MNPs) have been investigated and correlated with magneto-structural properties. Specific absorption rate and intrinsic loss power were calculated for these MNPs within the human tolerable range of frequency and amplitude,suggesting their potential in magnetic fluid hyperthermia therapy for possible cancer treatment.     

The effect of Au/Ag ratios on surface composition and optical properties of co-sputtered alloy nanoparticles in Au–Ag:SiO2 thin films

Gold–silver alloy nanoparticles with various Au concentrations in sputtered SiO₂ thin films were synthesized by using RF reactive magnetron co-sputtering and then heat-treated in reducing Ar + H₂ atmosphere at different temperatures. The UV–visible absorption spectra of the bimetallic systems confirmed the formation of alloy nanoparticles. The optical absorption of the Au–Ag alloy nanoparticles exhibited only one plasmon resonance absorption peak located at 450 nm between the absorption bands of pure Au and Ag nanoparticles at 400 and 520 nm, respectively, for the thin films annealed at 800 °C. The maximum absorption wavelength of the surface plasmon band showed a red shift with increasing Au content. XPS results indicated that the alloys were in metallic state, and they had a greater tendency to lose electrons as compared to their corresponding monometallic state. Moreover, the positive and negative shift of the Au(4f) core-level binding energies was observed for low and high Au concentration, respectively. Also a negative shift of the Ag(3d) binding energies was increased by increasing Au concentration. Diffusion of the particles toward the surface by increasing the temperature has also been illustrated by AFM images. Based on AFM observations, we have found that the particle size reduced from 35 to 20 nm by increasing the annealing temperature from 600 to 800 °C, while particle size increased by increasing Au concentration in films. In addition, lateral force microscopy (LFM) analysis showed that the alloy particles were uniformly distributed on the surface.     

P25@SiO2核壳材料的制备及其选择性光催化性能的研究

目的构筑具有尺寸选择性光催化功能的复合纳米结构,在维持二氧化钛材料光催化性能的同时,减少其对有机大分子材料及有机基底材料的腐蚀行为,拓宽光催化材料的使用范围。方法采用一锅法,通过TEOS围绕P25为核进行水解,制备了多孔SiO_2包覆TiO_2(P25)复合核壳结构(P25@SiO_2)纳米颗粒。结果 TEM、XRD、BET表征显示,这种复合核壳纳米结构具有较好的分散性和很高的比表面积(约528 m2/g)。光催化性能实验证实,这种复合核壳结构具有尺寸选择性光催化效应,即小分子氮氧化物气体(NOx)能通过壳层SiO_2孔道进入核层并降解90%以上,被氧化成硝酸盐固定下来;小分子有机物亚甲基蓝能穿过壳层孔道进入复合结构的核层部分,被氧化分解;大分子有机物胭脂红被壳层有效隔离而不被分解。老化试验显示,涂覆有这种核壳结构材料的有机基材(PET膜)被氧化老化的现象受到抑制。相反,与裸露的有机基材(PET膜)相比,由于壳层的保护作用,涂覆有核壳纳米结构的有机基材具有更好的抗紫外线性能。结论开发的这种具有尺寸选择性光催化的复合核壳结构材料,可以涂覆在各种有机基材的表面,赋予其一定的光催化功能,同时由于壳层的隔离保护作用,对基材的腐蚀作用受到抑制。这种复合核壳纳米结构也可以作为功能添加材料添加到各种涂料材料中,并赋予涂料一定的光催化性能,同时对涂料中的有机物不会产生强烈的分解作用,因此具有很好的应用前景。     

爆轰法制备碳包覆铁镍合金纳米颗粒及其表征

对掺杂硝酸铁和硝酸镍复合炸药前驱体,采用爆轰法合成碳包覆铁镍合金纳米颗粒。通过XRD,TEM,XRF,VSM等方法对合成的碳包覆合金纳米颗粒的形貌特征、结构组成及磁性行为进行了分析表征。结果表明,通过有效调整前驱体中金属源材料比例和碳材料组成,可爆轰合成较为完美的核壳结构碳包覆铁镍纳米颗粒,所得球形的纳米颗粒尺寸主要分布在10～60nm范围内且分散性较好,组成核主要由不同比例的铁镍元素构成,外壳层主要由石墨碳构成;由室温下磁性分析可知,该纳米颗粒表现出良好的超顺磁性。