Preparation and characterization of antibacterial Au/C core-shell composite

An environment-friendly oxidation-reduction method was used to prepare Au/C core-shell composite using carbon as core and gold as shell. The chemical structures and morphologies of Au/C core-shell composite and carbon sphere were characterized by X-ray diffraction, transmission electron microscope, energy dispersion X-ray spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS). The antibacterial properties of the Au/C core-shell composite against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) were examined by the disk diffusion assay and minimal inhibition concentration (MIC) methods. In addition, antibacterial ability of Au/C core-shell composite was observed by atomic force microscope. Results demonstrated that gold homogeneously supported on the surface of carbon spheres without aggregation and showed efficient antibacterial abilities.     

Oxidation of Au nanoparticles on HOPG using atomic oxygen

Various Au nanostructures prepared on highly ordered pyrolytic graphite (HOPG) were oxidized using atomic oxygen under ultrahigh-vacuum conditions, and the oxygen species formed in the Au nanostructures were characterized using X-ray photoelectron spectroscopy (XPS). For an Au thin film, only a single oxygen species could be identified in the O 1s spectrum, which can be attributed to Au-oxide. For Au nanoparticles smaller than ∼10 nm, in contrast, two different oxygen species were detected, which are suggested to be Au-oxide and subsurface oxygen (or dissolved oxygen), respectively. CO titration experiments confirm the formation of different oxygen species depending on the particle size.     

有序金纳米颗粒阵列的制备及光吸收特性研究

采用纳米球刻蚀技术中漂移法在玻璃基片上制备较大 面积不同直径的聚苯乙烯小球掩模板, 采用磁控溅射技术在掩模板上沉积不同厚度的金薄膜, 去除聚苯乙烯小球后, 通过扫描电子显微镜观察到周期排列的三角状金纳米颗粒点阵. 通过紫外-可见分光光度计测试所制备样品的光吸收特性, 发现表面等离子体共振峰随粒径增大发生红移, 随金纳米颗粒高度增加发生蓝移. 基于Mie理论, 利用Matlab软件编程对不同粒径的金阵列光吸收特性进行理论模拟, 并与实验结果进行对比. 关键词： 纳米球刻蚀 金纳米颗粒阵列 表面等离子体共振     

消光式核壳二聚体传感器的设计与光谱特性分析

根据ITO/Au纳米核壳二聚体粒子在生物医学领域的应用合理性,设计了一种实时检测生物液体的核壳二聚体探针消光式传感器;由偶极子理论推导出输出波长与外界环境折射率关系;利用MATLAB设计ITO/Au纳米核壳二聚体粒子结构;采用软件DDSCAT7.3结合离散偶极近似法,利用二聚体有效半径模拟计算了300~950nm可见光到红外光波段不同核壳比、二聚体间距、以及不同介质折射率的消光光谱;根据传感芯片折射率与偶极共振、耦合八级共振的响应关系得出ITO/Au二聚体的折射率灵敏特性。与传统Ag/Au核壳纳米粒子相比,ITO/Au纳米核壳二聚体结构引入了可作为传感芯片灵敏性自参考参数的耦合八级共振峰,同时ITO/Au二聚体结构的折射率灵敏度可达到419nm/RIU。这些工作及其结果对制作消光式传感器具有重要的意义。     

原子层沉积方法制备核-壳型纳米材料研究

采用原子层沉积方法在碳黑纳米颗粒表面分别沉积Al₂O₃, ZnO, TiO₂和Pt, 成功制备出核-壳型纳米材料. 通过高分辨率透射电子显微镜、X射线光电子能谱仪、 能谱仪对材料的表面形貌、晶体结构、薄膜成分进行了表征和分析. 结果表明, 原子层沉积方法是制备核壳型纳米材料的理想方法. 此外, 还分析了采用原子层沉积方法沉积不同材料, 所生长的薄膜材料有单晶、多晶、非晶等多种存在形式的形成原因. 关键词： 原子层沉积 核-壳型纳米材料 碳黑纳米颗粒     

水热法促进EuVO_4@YVO_4核壳结构纳米颗粒中Eu~(3+)的扩散及其对发光性能的影响

采用共沉淀法制备了EuVO4@YVO4核壳结构纳米颗粒,然后用聚电解质聚苯乙烯磺酸钠对其进行包覆和保护,并在200?C下对样品水热处理0—48 h.在水热处理48 h后,样品的发光强度增强了约5倍,平均发光寿命由0.410 ms延长至0.579 ms.对样品的发光衰减曲线的拟合、分析为Eu3+的扩散提供了有力的证据.这种自内而外的扩散降低了样品核心中Eu3+的局域浓度,削弱了浓度猝灭效应,同时又能够避免表面猝灭效应的发生,从而使得样品的发光寿命变长、发光效率迅速提升.     

Au纳米颗粒和CdTe量子点复合体系发光增强和猝灭效应

利用金属蒸发真空多弧离子源注入机, 将Au离子注入到高纯石英玻璃来制备镶嵌有Au 纳米颗粒的衬底材料, 随后将化学方法合成的CdTe量子点旋涂在玻璃衬底上制备了Au纳米颗粒和CdTe量子点复合体系. 通过对镶嵌有Au纳米颗粒的衬底进行热退火处理来控制Au纳米颗粒的生长和分布, 系统研究了Au纳米颗粒的局域表面等离子体共振对CdTe量子点光致发光性能的影响. 利用光学吸收谱、原子力显微镜、透射电子显微镜和光致发光谱对样品进行了表征和测试. 光致发光谱表明, Au纳米颗粒的局域表面等离子体对CdTe量子点的发光有增强效应也有猝灭效应. 深入分析了Au纳米颗粒和CdTe量子点之间的相互作用过程, 提出了关于Au-CdTe 纳米复合体系中CdTe 发光增强和猝灭的新机理. 该实验结果为利用金属纳米颗粒表面等离子体技术制备高发光性能的光电子器件提供了较好的参考.     

Synthesis and self-assembly of magnetic nanoparticles

We report the synthesis and self-assembly of different shapes and sizes of FePt nanoparticles. Our study shows that surfactants and solvent play an important role in the synthesis of different shapes and sizes of FePt nanoparticles. Higher boiling point solvents lead to the formation of spherical nanoparticles and low boiling point solvents form cubic nanoparticles. Our studies also indicate that self-assembly of FePt nanoparticles on substrates is a complex process that is sensitive to the concentration of excess surfactant in the nanoparticle solution.     

Highly sensitive and selective trimethylamine sensors based on WO3 nanorods decorated with Au nanoparticles

One-dimensional tungsten oxide (WO₃) gas sensing materials have been widely used for the detection of trimethylamine (TMA) gas. Furthermore, it is believed that an effective method to improve the gas sensing performance is to introduce noble metals into sensing materials. In this work, a novel gas sensing material was prepared by decorating Au nanoparticles on WO₃ nanorods. Based on field emission scanning electron microscopy (FESEM/EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM), the morphology and microstructure of as-prepared samples were characterized. Results show that Au nanoparticles with diameter of 13–15 nm are loaded on the surface of WO₃ nanorods with length of about 1–2 µm and width of 50–80 nm. Gas sensing tests reveal that the Au@WO₃ sensor has remarkably enhanced response to TMA gas compared with pure WO₃ nanorods. In addition, and the gas sensing mechanism has been investigated based on the experimental results. The superior sensing features indicate the present Au@WO₃ nanocomposites are promising for gas sensors, which can be used in the detection of the trimethylamine gas and this work provides insights and strategies for the fabrication of sensing materials.     

Flexible and transparent resistive switching devices using Au nanoparticles decorated reduced graphene oxide in polyvinyl alcohol matrix

We have investigated the resistive switching mechanism in solution processed Au-reduced graphene oxide-polyvinyl alcohol (PVA) nanocomposites on flexible substrates. Monodispersed gold nanoparticles (Au NPs) attached to reduced graphene oxide (RGO) in aqueous PVA solution have been synthesized using a novel one pot technique. The fabricated hybrid device showed high On/Off switching ratio more than 10³ with low operating voltages. The performance of hybrid device can be effectively enhanced over control RGO device. The switching mechanism occurs from the electrochemical reduction/oxidation process of partially reduced graphene oxide. The proposed devices reveal superior asymmetric bipolar resistive switching characteristics attractive for solution processable flexible and transparent non-volatile memory applications.     

Assembly of single-walled carbon nanotubes on patterns of Au nanoparticles

We report on the assembly of single-walled carbon nanotubes (SWNTs) and gold nanoparticles (NPs) hybrid structure without any surface modification of SWNTs on patterns of Au nanoparticles (NPs). Microscale Au NP patterns were created on composite self-assembled monolayer (SAM) templates of octadecanethiol (ODT) and octanedithiol (OD) through self-assembly of Au NPs via the thiol-Au chemical bond onto the OD region. On such templates, we observed extensive adhesion and strong affinity of SWNTs on the Au NPs and no SWNT on ODT. We also examined systematically the adhesion of SWNTs on ODT with varying coverage of vapour-deposited Au. We observed little SWNT attachment even when there are high-density of Au clusters on the ODT SAM. Extensive adhesion of SWNTs is observed only when the coverage of ODT by Au is almost complete. Dynamic contact angle measurements of dichlorobenzene on the ODT/Au substrates revealed a direct correlation between the surface wettability and the SWNT assembly on a molecular template.     

Radiative quantum efficiency of CdSe/ZnS core-shell colloidal solutions: Size-dependence

Thermo-optical parameters of CdSe/ZnS core-shell nanoparticles suspended in toluene were measured using a thermal lens (TL) technique. TL transient measurements were performed using the mode-mismatched dual-beam (excitation and probe) configuration. A He-Ne laser at λ_p = 632.8 nm was used as the probe beam and an Ar⁺ laser (at λ_e = 514.5 nm) was used as the excitation beam for studies as a function of both core size and concentration of CdSe/ZnS nanocrystals. The fraction thermal load (φ) and radiative quantum efficiencies (η) of the CdSe/ZnS were determined. Dependence on core size (∼2-5 nm) and concentration (∼0.01-0.62 mg/ml) was observed for both φ and η parameters.     

The influence of size effects in Pt and Au nanoparticles studied by 197Au Mössbauer spectroscopy

We present a detailed Mössbauer study of a series of Au and Pt particles in the size range from 1 to 17 nm. All measured spectra can be explained consistently with a refined model, in which the Mössbauer isomer shift varies in the inner core of a small metallic particle due to size effects. The large surface/volume ratio makes surface effects, like screening of considerable importance and even the so-called quantum-size effect may have an influence. The size evolution of the electronic properties of the particles is also discussed.     

Time evolution of Ag-Cu and Ag-Pd core-shell nanoclusters

The possibility of obtaining core-shell nanoparticles by depositing adatoms of a different element B above a cluster of an element A (system B/A) is studied by Molecular Dynamics simulations. We consider the four cases Ag/Cu, Cu/Ag, Ag/Pd and Pd/Ag, which present very different behaviours, and investigate whether it is possible to build up of well-defined core-shell structures.     

Au的金属颗粒对二硫化钼发光增强

二硫化钼(MoS₂)是一种层状的二维过渡金属硫族化合物材料,从块体到单层,禁带由间接带隙变为直接带隙,由于通常机械剥落的单层MoS₂是n型掺杂的,使得其发光效率仍然很低. 在本文中,采用匀胶机旋涂的方法将共振吸收峰在514 nm附近的纳米金颗粒尽可能均匀的铺在单层、双层以及多层的MoS₂样品表面,发现单层和双层样品的光致发光谱(PL谱)分别增强了约30倍和2倍同时伴随着峰位的蓝移,而多层样品的发光强度也略有增强. 拉曼特性揭示了纳米金颗粒对单层和双层MoS₂样品产生了明显的p型掺杂,从而增强了发光;同时纳米金颗粒的表面等离子激元效应对激发光的天线作用也是增强MoS₂的光致发光的一个因素. 关键词： 二硫化钼 光致发光 p型掺杂 Au纳米颗粒     

Transient competition between photocatalysis and carrier recombination in TiO_2 nanotube film loaded with Au nanoparticles

Highly ordered TiO2 nanotube array(TNA) films are fabricated by using an anodic oxidation method. Au nanoparticles(NPs) films are decorated onto the top of TNA films with the aid of ion-sputtering and thermal annealing. An enhanced photocatalytic activity under ultraviolet C(UVC, 266 nm) light irradiation is obtained compared with that of the pristine TNA, which is shown by the steady-state photoluminescence(PL) spectra. Furthermore, a distinct blue shift in the nanosecond time-resolved transient photoluminescence(NTRT-PL) spectra is observed. Such a phenomenon could be well explained by considering the competition between the surface photocatalytic process and the recombination of the photo-generated carriers. The enhanced UV photocatalytic activities of the Au–TNA composite are evaluated through photo-degradation of methyl orange(MO) in an aqueous solution with ultraviolet–visible absorption spectrometry. Our current work may provide a simple strategy to synthesize defect-related composite photocatalytic devices.     

金纳米棒核／二氧化硅壳纳米复合结构的可控制备及细胞成像

采用模板合成以及溶胶凝胶方法制备了金纳米棒核／二氧化硅壳（GNR@SiO2）纳米复合粒子,探讨了这种新型纳米复合结构的可控制备、光谱性质、细胞毒性和细胞成像。通过紫外可见分光光度计、透射电镜、共聚焦显微镜对样品进行表征,结果表明：通过对反应时间的调控,获得的纳米复合粒子的二氧化硅壳层厚度可以控制在20～30nm。由于二氧化硅壳层的存在,大大提高了金纳米棒的稳定性,同时降低了金纳米棒的细胞毒性;此外,由于二氧化硅壳层具有良好的化学修饰作用,因此可以将荧光探针分子标记在二氧化硅壳层表面,修饰后的纳米复合粒子可以通过细胞内吞作用进入细胞,从而实现细胞内的光学成像。因此,该纳米粒子复合材料在生物传感、细胞成像以及光热治疗等方面有着良好的应用前景。     

Synthesis and characterization of core-shell europium(III)-silica nanoparticles

Luminescent core-shell europium(III)-silica nanoparticles were prepared using europium(III) chelate core structure and polyvinylpyrrolidone synthesis strategy for silica shell. Europium(III):naphtoyltrifluoroacetone:trioctylphosphineoxide complex was spontaneously agglomerated from organic solvent to water. Polyvinylpyrrolidone was adsorbed onto the core structure and stable silica shell was synthesized using tetraethylorthosilicate. Nanosized particles with a diameter of 71 ± 5 nm and 11 nm shell thickness were obtained with fluorescence decay rate of 517 μs and excitation and emission wavelengths of 334 and 614 nm, respectively.     

十八胺LB膜吸附组装金纳米颗粒研究

制备了十八胺单层、多层LB膜及粒径为几个纳米的金纳米粒子。pH值小于10.3时十八胺带正电荷,将其置于金纳米溶胶(pH值10.3)中,带负电荷的金纳米粒子与带正电荷的十八胺之间通过静电作用,金纳米颗粒被成功地吸附组装到十八胺LB膜中,形成纳米薄膜。紫外-可见光谱、红外光谱及扫描电镜显示:金纳米颗粒通过这种方法能够很好的组装在十八胺LB膜上,且其组装层整齐有序,同时也受十八胺LB膜层数及组装时间的影响。     

Stabilization of Pt nanoparticles by single stranded DNA and the binary assembly of Au and Pt nanoparticles without hybridization

The non-specific interaction between single stranded DNA (ssDNA) and 12 nm Pt nanoparticles is investigated in this work. The data show a strong and non-specific interaction between the two which can be exploited for the stabilization of Pt nanoparticles in aqueous solutions. Based on the experimental findings, a non-hybridization based protocol to assemble 17 nm Au and Pt nanoparticles (12 nm cubic and 3.6 nm spherical) by single-stranded DNA was developed. Transmission electron microscopy (TEM) and UV–visible spectroscopy confirmed that Au and Pt nanoparticles could be assembled by the non-specific interaction in an orderly manner. The experimental results also caution against the potential pitfalls in using DNA melting point analysis to infer metal nanoparticle assembly by DNA hybridization.