Shape tunable synthesis of anisotropic gold nanostructures through binary surfactant mixtures

In recent years, much effort has been made to produce gold (Au) nanorods of different sizes through the use of binary surfactant mixtures via a seed-mediated growth approach. However, how the ratio of two different surfactants influences the shape of the resulting Au nanoparticles remains to be elucidated. Here, we report the shape-controlled synthesis of Au nanoparticles using a binary surfactant mixture of CTAB (cetyltrimethylammonium bromide) and DDAB (didodecyldimethylammonium bromide) via a silver-assisted seed-mediated growth approach. Decreasing the CTAB/DDAB ratio results in a shape transition from Au nanorods to elongated tetrahexahedra and finally to Au bipyramids. The results showed significant improvement in the yield of Au bipyramidal type nanoparticles in different sizes (nm to μm) by using binary surfactant mixtures without any need for shape selection procedure. By varying the pH and concentration of ascorbic acid, we can control the shape and size of Au nanoparticles (i.e., truncated bipyramids, dogbones, and nanodumbbells) at fixed CTAB/DDAB ratios. A preliminary growth mechanism has been proposed based on the change in the mixed micelle soft-template induced by the increasing concentration of DDAB and reaction parameters (i.e., pH, concentration of ascorbic acid). These results constitute the advances in the understanding for synthesizing anisotropic Au nanoparticles of tunable optical properties via engineering the design of a soft-template. These anisotropic Au nanoparticles, especially, bipyramids of different morphologies and sizes are potential candidates for the enhancement of the optical response and developing label-free biosensing devices.     

Facile synthesis of gold nanoplates by thermally reducing AuCl_4~- with aniline

We herein report a one-step,wet-chemical approach to synthesizing gold nanoplates in large quantities via the AuCl_4~-thermal reduction process by aniline,without introducing additional capping agent or suffactant.It is found that the reduction kinetics of AuCl_4~-is greatly altered by varying the initial molar ratio of aniline to AuCl_4~-.Moreover,further investigation reveals that the in- situ formed polyaniline could serve effectively as a capping agent to preferably adsorb the{111}facets of gold crys...     

Liquid‐Phase Epitaxial Growth of Two‐Dimensional Semiconductor Hetero‐nanostructures

Although many two‐dimensional (2D) hybrid nanostructures are being prepared, the engineering of epitaxial 2D semiconductor hetero‐nanostructures in the liquid phase still remains a challenge. The preparation of 2D semiconductor hetero‐nanostructures by epitaxial growth of metal sulfide nanocrystals, including CuS, ZnS and Ni₃S₂, is achieved on ultrathin TiS₂ nanosheets by a simple electrochemical approach by using the TiS₂ crystal and metal foils. Ultrathin CuS nanoplates that are 50–120 nm in size and have a triangular/hexagonal shape are epitaxially grown on TiS₂ nanosheets with perfect epitaxial alignment. ZnS and Ni₃S₂ nanoplates can be also epitaxially grown on TiS₂ nanosheets. As a proof‐of‐concept application, the obtained 2D CuS–TiS₂ composite is used as the anode in a lithium ion battery, which exhibits a high capacity and excellent cycling stability.     

Growth of individual hydrogen-bonded nanostructures on gold monolayers

The growth of individual nanometer-sized (3.4 +/- 1.4 nm) hydrogen bonded assemblies 1(2) x (DEB)6 on gold monolayers was achieved through an exchange reaction between single isolated calix[4]arene dimelamine 2 (1.1 +/- 0.2 nm) embedded in hexanethiol monolayers and double rosette hydrogen bonded assembly 1(3) x (DEB)6 in solution. The growth process was monitored by tapping mode atomic force microscopy (TM-AFM).     

种子生长法制备Au@Ag核壳纳米粒子

Au@Ag核壳纳米粒子由于具有优异的局部等离子共振性质 (LSPR),近年来引起人们极大的关注,目前,在成像、催化、信息存储、生化传感等领域已经得到了广泛的应用。在制备Au@Ag核壳纳米粒子的方法中,种子生长法的应用最为广泛,因为它可以实现对Ag壳尺寸及形貌的有效控制。本文综述了影响Au@Ag核壳纳米粒子核壳结构尺寸、形貌、Ag壳厚度以及覆盖均匀程度的一些主要因素,包括Au种子的形貌和浓度、AgNO₃浓度、封端剂、还原剂以及其他一些影响因素。研究发现,Au@Ag核壳纳米粒子在表面增强拉曼光谱 (SERS) 方面具有广泛的应用前景。     

Organometallic chemistry and catalysis on gold metal surfaces

As in transition metal complexes, CN-R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of CN-R, primary amines (R′NH₂) and O₂ to give carbodiimides (R′-NCN-R). An analogous reaction of CO, RNH₂, and O₂ gives isocyanates (R-NCO), which react with additional amine to give urea (RNH)₂CO products. The gold-catalyzed reaction of CN-R with secondary amines (HNR′₂) and O₂ gives mixed ureas RNH(CO)NR′₂. In another type of gold-catalyzed reaction, secondary amines HN(CH₂R)₂ react with O₂ to undergo dehydrogenation to the imine product, RCHN(CH₂R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.     

Self-assembly of lysozyme on the surfaces of gold nanoparticles

The interaction of lysozyme(Lys) and gold nanoparticles was investigated via UV-vis absorption and resonance light-scattering method.There are some changes of the plasmon absorption and resonance light-scattering of gold nanoparticles that were observed via the addition of Lys.The normalized plasmon absorption and resonance light-scattering intensity with gold nanoparticles were both linear wilh 1-20 nmol/L Lys.A simple model about the component of the gold nanoparticles and Lys complex was established and the calculated result was fitted well in their concentration ratio.Furthermore,the activity analysis of Lys showed that the interaction was weak and nondestructive.     

Adsorption change of cyclohexyl acetylene on gold nanoparticle surfaces

The conformational changes of cyclohexyl acetylene (CHAL) on gold nanoparticle surfaces were investigated by means of concentration- and temperature-dependent surface-enhanced Raman scattering (SERS). Depending on concentrations and temperatures, the spectral changes of the acetylene ν(C≡C) stretching vibration on gold nanoparticles appeared to be more conspicuous than those of cyclohexyl ring modes. The density functional theory (DFT) calculation was performed at the level of B3LYP/6-31G++(d,p) to compare the energetic stability and vibrational frequencies of the various conformers of cyclohexanethiol (CHT) and CHAL. The DFT calculations were also carried out at the level of B3LYP/LACVP** on the CHAL molecule adsorbed on Au clusters at several sites to explain the spectral changes of the acetylene ν(C≡C) stretching vibration.     

Influence of biomass and gold salt concentration on nanoparticle synthesis by the tropical marine yeast Yarrowia lipolytica NCIM 3589

Cell-associated gold nanoparticles and nanoplates were produced when varying number of Yarrowia lipolytica cells were incubated with different concentrations of chloroauric acid (HAuCl₄) at pH 4.5. With 10⁹ cells ml⁻¹ and 0.5 or 1.0 mM of the gold salt, the reaction mixtures developed a purple or golden red colour, respectively, and gold nanoparticles were synthesized. Nanoparticles of varying sizes were produced when 10¹⁰ cells ml⁻¹ were incubated with 0.5, 1.0 or 2.0 mM chloroauric acid salt. With 3.0, 4.0 or 5.0 mM HAuCl₄, nanoplates were also observed. With 10¹¹ cells ml⁻¹ nanoparticles were synthesized with almost all the gold salt concentrations. The cell-associated particles were released outside when nanoparticle-loaded cells were incubated at low temperature (20 °C) for 48 h. With increasing salt concentrations and a fixed number of cells, the size of the nanoparticles progressively increased. On the other hand, with increasing cell numbers and a constant gold salt concentration, the size of nanoparticles decreased. These results indicate that by varying the number of cells and the gold salt concentration, a variety of nanoparticles and nanoplates can be synthesized. Fourier transform infrared (FTIR) spectroscopy revealed the possible involvement of carboxyl, hydroxyl and amide groups on the cell surfaces in nanoparticle synthesis.     

Gold nanoparticle arrays directly grown on nanostructured indium tin oxide electrodes: Characterization and electroanalytical application

This work describes an improved seed-mediated growth approach for the direct attachment and growth of mono-dispersed gold nanoparticles on nanostructured indium tin oxide (ITO) surfaces. It was demonstrated that, when the seeding procedure of our previously reported seed-mediated growth process on an ITO surface was modified, the density of gold nanospheres directly grown on the surface could be highly improved, while the emergence of nanorods was restrained. By field emission scanning electron microscopy (FE-SEM) and cyclic voltammetry, the growth of gold nanoparticles with increasing growth time on the defect sites of nanostructured ITO surface was monitored. Using a [Fe(CN)₆]³⁻/[Fe(CN)₆]⁴⁻ redox probe, the increasingly facile heterogeneous electron transfer kinetics resulting from the deposition and growth of gold nanoparticle arrays was observed. The as-prepared gold nanoparticle arrays exhibited high catalytic activity toward the electrooxidation of nitric oxide, which could provide electroanalytical application for nitric oxide sensing.     

Voltammetric determination of anabolic steroid nandrolone at gold nanoparticles modified ITO electrode in biological fluids

The electrochemical behavior of nandrolone decanoate (ND) at gold nanoparticles modified indium tin oxide (ITO) electrode was investigated. Oxidation of ND has been carried out in phosphate containing supporting electrolyte in the pH range 2.1-9.2 and a well-defined oxidation peak was noticed. The peak potential (E_p) of the oxidation peak decreases linearly with increasing pH. Linear calibration curve is obtained over the nandrolone decanoate concentration range of 50 nM to 1.5 μM at pH 7.2 with a detection limit of 1.36 × 10⁻⁷ M. The proposed method is effectively applied to detect the concentration of ND in human blood serum and urine samples after 24 and 72 h of intramuscular injection. The method is rapid and does not require any pre-treatment.     

银纳米晶体的制备与表征

在聚乙烯吡咯烷酮存在的条件下,用水合肼还原硝酸银,通过控制反应条件成功制备出了粒径均一、有良好分散性的银纳米微粒,并以此为种子,利用种子诱导生长,在十六烷基三甲基溴化铵的棒状胶束环境中制备出了银纳米棒和纳米线.并用X射线衍射、透射电子显微镜、傅立叶红外光谱和紫外-可见光谱等手段对产品的形貌、结构进行了表征.     

单分散纳米金尺寸的分步晶种生长控制

以聚乙烯吡咯烷酮(poly(vinylpyrrolidone), PVP)为保护剂, 硼氢化钠为还原剂, 合成了尺寸为(1.9±0.4) nm的单分散金胶体, 再以其作为一级晶种, 并分别用抗坏血酸和PVP为还原剂和保护剂, 通过改变各步晶种尺寸和氯金酸与晶种的摩尔比分步逐级合成了尺寸为3.2、4.7、6.3、8.0、10.3、14.0 nm的系列金纳米颗粒. 以LaMer模型为基础, 对分步晶种生长过程中影响金胶体产物尺寸分布(单分散性)的主要因素进行了讨论. 缓慢加入抗坏血酸并降低氯金酸对晶种的相对量对于单分散金纳米颗粒的控制合成有决定性作用. 快速加入抗坏血酸会因二次成核而导致金颗粒尺寸分布范围变宽.     

纳米结构导电聚合物材料研究进展

具有纳米结构的导电聚合物因其诱人的应用前景越来越引起人们的重视。本文综述了聚苯胺、聚吡咯以及聚噻吩等导电聚合物的零维、一维、二维以及三维纳米结构的合成方法,并介绍了聚合物纳米结构的表征以及研究现状和应用前景。参考文献60篇。     

One-step controlled synthesis of anisotropic gold nanostructures with aniline as the reductant in aqueous solution

We report a general and versatile method for controlled synthesis of anisotropic gold nanostructures through the reduction of HAuCl4 by aniline in aqueous solution, without the need for an additional stabilizer or capping agent. In this approach, the reduction kinetics of AuCl-4 can be altered by simply adjusting the initial pH and temperature, inducing the formation of a wide variety of anisotropic nanostructures such as dispersed or multilayered plates, wires with networked or paramecium-like structures, and ginger-shaped particles. AFM, TEM, XRD, EDX, FTIR, and UV-vis-NIR measurements were used to characterize the resulting gold nanostructures. Investigation reveals that in situ formed polyaniline serves effectively as a capping agent to direct the shape of gold nanostructures during the slow growth process. These as-synthesized gold nanostructures exhibit strongly shape-dependent optical properties. This facile approach may be extended to the synthesis of some other anisotropic metal nanostructures such as platinum or palladium.     

Quantitative investigation by atomic force microscopy of supported phospholipid layers and nanostructures on cholesterol-functionalized glass surfaces

Understanding the interaction mechanisms of phospholipids with surfaces is crucial for the exploitation of lipid bilayers as models of the cell membrane as well as templates for biosensors. Moreover, controlling and manipulating lipid nanoparticles for the investigation of their properties by means of single-particle sensitive surface techniques require the ability to tailor the chemical properties of surfaces to achieve a stable and sparse binding of lipid particles, while keeping them from aggregating, or denaturing. Here we present a quantitative morphological and structural investigation by atomic force microscopy of supported phospholipid layers and nanostructures on cholesterol-functionalized glass surfaces, in comparison with other surfaces with different interfacial properties. We show that the functionalization of glass coverslips with cholesterol groups is a viable route for the production of optically transparent, scanning probe microscopy-compatible clean substrates for the effective immobilization of both extended single lipid bilayers and lipid nanoparticles.     

Use of cellulose derivatives on gold surfaces for reduced nonspecific adsorption of immunoglobulin G

This study addresses the design of protein-repellent gold surfaces using hydroxyethyl- and ethyl(hydroxyethyl) cellulose (HEC and EHEC) and hydrophobically modified analogues of these polymers (HM-HEC and HM-EHEC). Adsorption behavior of the protein immunoglobulin G (IgG) onto pure gold and gold surfaces coated with cellulose polymers was investigated and described by quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM) and contact angle measurements (CAM). Surfaces coated with the hydrophobically modified cellulose derivatives were found to significantly outperform a reference poly(ethylene glycol) (PEG) coating, which in turn prevented 90% of non-specific protein adsorption as compared to adsorption onto pure gold. HEC and EHEC prevented around 30% and 60% of the IgG adsorption observed on pure gold, while HM-HEC and HM-EHEC were both found to completely hinder biofouling when deposited on the gold substrates. Adsorption behavior of IgG has been discussed in terms of polymer surface coverage and roughness of the applied surfaces, together with hydrophobic interactions between protein and gold, and also polymer-protein interactions.     

Integration of a highly ordered gold nanowires array with glucose oxidase for ultra-sensitive glucose detection

A highly sensitive amperometric nanobiosensor has been developed by integration of glucose oxidase (GO_x) with a gold nanowires array (AuNWA) by cross-linking with a mixture of glutaraldehyde (GLA) and bovine serum albumin (BSA). An initial investigation of the morphology of the synthesized AuNWA by field emission scanning electron microscopy (FESEM) and field emission transmission electron microscopy (FETEM) revealed that the nanowires array was highly ordered with rough surface, and the electrochemical features of the AuNWA with/without modification were also investigated. The integrated AuNWA–BSA–GLA–GO_x nanobiosensor with Nafion membrane gave a very high sensitivity of 298.2 μA cm⁻² mM⁻¹ for amperometric detection of glucose, while also achieving a low detection limit of 0.1 μM, and a wide linear range of 5–6000 μM. Furthermore, the nanobiosensor exhibited excellent anti-interference ability towards uric acid (UA) and ascorbic acid (AA) with the aid of Nafion membrane, and the results obtained for the analysis of human blood serum indicated that the device is capable of glucose detection in real samples.     

PVP存在下液液界面生长法制备硒纳米线(英)

0IntroductionSelenium(Se)iswellknownforitsphotoelectri鄄calandsemiconductorpropertiesandhasbeensuc鄄cessfullyusedinsolarcells,rectifiers,photographicexposuremetersandxerography[1].Itcouldbeexpect鄄edthattheuniquestructureandthequalityofone鄄di鄄mensional(