钯纳米颗粒形貌控制合成及其SPR／SERS性质

在水溶液中分别以十六烷基三甲基溴化铵（CTAB）和CTAB／柠檬酸钠混合剂为包覆剂合成钯纳米颗粒,并研究其形貌演变．钯纳米颗粒在成核阶段会形成具有不同孪晶结构的晶核,在生长阶段又会选择性的放大某一组晶面,这两个因素导致了钯纳米颗粒形貌的多样性．在合成中CTAB既会影响钯纳米颗粒的成核,也会影响颗粒晶面的选择性生长．通过改变CTAB和还原剂的量可以调控钯纳米颗粒的形貌．溶液中CTAB和还原剂浓度的改变,非常明显地影响合成产物中不同形貌钯纳米颗粒的产率．通过向溶液中引入柠檬酸离子调控纳米颗粒的成核与生长过程,首次合成出了星状钯二十面体和截面为五角星形的钯纳米棒．这些不同形貌的钯纳米颗粒有着不同的表面等离子体共振和表面增强拉曼散射性质．     

十六烷基三甲基溴化铵辅助作用下球形、蠕虫状和网状Pd纳米粒子的制备与表征

以十六烷基三甲基溴化铵(CTAB)为表面活性剂,NaBH4为还原剂,通过调节水相体系中CTAB和NaBH4浓度,合成了一系列不同形貌的Pd纳米粒子,合成过程简便易行且环境友好.结果表明,随着CTAB浓度的增加,Pd粒子形貌由纳米微球逐渐向纳米线网络形态转变.CTAB浓度和NaBH4浓度是决定Pd粒子形貌的两个重要因素.     

三角形银纳米片的合成及其影响因素

报道了一种在不需光照的条件下制备三角形银纳米片的新方法.在表面活性剂BRIJ35存在下,将硝酸银用硼氢化钠和柠檬酸钠还原,在不同温度范围内反应形成各种尺度的三角形银纳米片,探讨了硼氢化钠浓度、BRIJ35浓度和表面活性剂的种类和溶液pH值等因素对银纳米颗粒形貌和尺寸的影响.     

溶剂热法制备银纳米晶

以聚乙烯吡咯烷酮(PVP)作为表面活性剂,利用乙二醇溶剂热法成功制备了银纳米颗粒;利用场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)分析了样品的形貌和晶体结构,并考察了溶剂组成等因素对银纳米颗粒形貌的影响.研究结果表明所得银纳米晶粒径均一,直径约为90nm;增大PVP的加入量会降低产物的粒径,溶剂中水的引入会影响银纳米晶的形貌.     

一种制备高长径比金纳米棒的新方法

报道了一种制备高长径比金纳米棒的新方法. 在25 ℃条件下, 采用种子介导生长法, 通过优化表面活性剂十六烷基三甲基溴化铵(CTAB)的浓度, 制备了长度(200±18.62) nm, 长径比大于10的金纳米棒, 并讨论了金纳米棒的形成机制. 结果表明, 金纳米棒的长径比和纵向吸收波长与CTAB的浓度有关. 此外, 通过提高反应液的离子强度, 利用制备的金纳米棒与球形颗粒不同的静电作用将金纳米棒分离纯化. 运用透射电子显微镜(TEM)和扫描电子显微镜(SEM)对金纳米棒的表面形貌进行表征.     

以单晶银纳米方块为液相外延生长晶种的纳米晶形貌可控合成方法

本文简要综述了以单晶银纳米方块做为可控外延生长的品种来合成各种银纳米晶的相关工作．通过改变银前驱体和晶种颗粒的比例、表面包裹分子及其用量、还原剂浓度、添加欠电位金属阳离子等手段,我们成功地控制了银纳米晶的外延生长方向和裸露晶面,并合成出一系列尺寸、形貌可控的银纳米晶,包括立方体、立方八面体、八面体、八足体、二十四面体、凹面立方八面体和凹面八面体等．除了对合成方法和过程的介绍,本文还简要讨论了每种纳米结构的形成机制．     

利用去湿现象制备具有SERS活性的银纳米粒子图案

构建了具有表面增强拉曼散射(SERS)活性的二维有序环状与盘状的银纳米粒子结构, 利用CTAB包覆银纳米粒子的氯仿溶液直接在图案化的金基底上进行去湿, 当改变银纳米粒子的浓度时可以得到不同的图案. 利用原子力显微镜(AFM)对其结构进行了表征, 以4-巯基吡啶作为探针分子, 采用表面增强拉曼成像技术研究了这种基底的SERS活性, 这将为SERS的研究开拓新的领域.     

银纳米棱镜的形成及其光学性能研究

以有机溶剂作为反应介质,聚合物为稳定剂,通过微波辅助溶液法成功地制备了具有特殊光学性能的银纳米棱镜.利用X射线衍射、透射电子显微镜和紫外-可见光谱等手段跟踪反应过程.结果显示,随着反应的进行,银纳米粒子由10nm左右的球形颗粒逐渐转变为具有规则三角形(或缺角的三角形)形貌的纳米棱镜;同时,紫外-可见吸收峰不但显示出明显的量子尺寸效应,而且吸收峰也由单一的等离子共振吸收峰变为多重的多极吸收峰共同存在,胶体溶液也随之显示出不同的颜色.改变反应物的配比、体系的浓度及无机前驱物都会得到位置和峰形各不相同的吸收曲线,从而得到多彩的纳米银胶体溶液.     

银纳米颗粒对铝金属在酸性介质中的耐蚀性能研究（英文）

采用材料失重、动电位极化和电化学交流阻抗技术,分别测试了温度为30 ℃,浓度为1.0 mol·L~(-1)盐酸溶液中不添加和添加银纳米颗粒时铝的腐蚀速率.结果表明,当银纳米颗粒的浓度为0.014 g·L~(-1)时,其防护效率达96.4%.随着银纳米颗粒的浓度增大,铝/溶液界面的双电层电容值减小,说明铝的表面发生了银纳米颗粒的吸附.朗缪尔吸附等温方程和动力学-热力学模型均可以较好地拟合所得到的实验数据.为了确认铝金属表面与银纳米颗粒的相互作用类型,得到了铝的零电荷电位值.研究发现,通过扫描电子显微镜和能量散射X-射线能谱分析,并结合电化学实验后铝电极表面的外观观察,可以很好地解释材料失重和电化学测试得到的数据.     

CTAB对四-(4-N-甲基吡啶)卟啉SERS谱的影响

研究了阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)对四-(4-N-甲基吡啶)卟啉(H2TMPyP)及其银配合物(AgTMPyP)在Ag胶中的表面增强拉曼散射(SERS)谱的影响.SERS光谱表明,吸附于Ag胶粒的H2TMPyP与衬底银原子结合形成AgTMPyP,加入CTAB后,部分AgTMPyP表面络合物还原为H2TMPyP.相似的去金属化反应也出现在AgTMPyP/Ag胶/CTAB体系中.CTAB的加入使SERS谱带强度明显增加.AgTMPyP的去金属化被认为是由于CTAB的存在使Ag胶颗粒表面附近微环境发生改变.     

Shape‐Dependent Catalytic Activity of Silver Nanoparticles for the Oxidation of Styrene

Metal nanoparticles with different shapes have different crystallographic faces. It is therefore of interest to study the effect of the shape of metal nanoparticles on their catalytic activity in various organic and inorganic reactions. Truncated triangular silver nanoplates with well‐defined planes were synthesized by a simple solvothermal approach. The activity of these truncated triangular silver nanoparticles was compared with that of cubic and near‐spherical silver nanoparticles in the oxidation of styrene in colloidal solution. It was found that the crystal faces of silver nanoparticles play an essential role in determining the catalytic oxidation properties. The silver nanocubes had the {100} crystal faces as the basal plane, whereas truncated triangular nanoplates and near‐spherical nanoparticles predominantly exposed the most‐stable {111} crystal faces. As a result, the rate of the reaction over the nanocubes was more than 14 times higher than that on nanoplates and four times higher than that on near‐spherical nanoparticles.     

Thermal aqueous solution approach for the synthesis of triangular and hexagonal gold nanoplates with three different size ranges

The synthesis of gold nanoplates was carried out in an aqueous solution by thermal reduction of HAuCl(4) with trisodium citrate in the presence of cetyltrimethylammonium bromide (CTAB) surfactant in just 5-40 min. The sizes of the gold nanoplates can be varied from as small as tens of nanometers in width, to several hundreds of nanometers, and even a few microns in width by changing the reagent concentrations, solution temperature, and the reaction time. A [CTAB]/[HAuCl(4)] ratio of 6 in the reaction solution was found to be favorable for the formation of gold nanoplates. The nanoplates possess well-defined shapes with sharp edges. The small nanoplates exhibit mainly a triangular shape, while larger nanoplates show a mixture of triangular, hexagonal, truncated triangular, and other symmetrical structures. The nanoplates are composed of essentially (111) lattice planes, as revealed by both XRD and TEM results. Nanoplates with widths from several hundreds of nanometers to a few microns absorb light strongly in the near-infrared region. The growth mechanism of these nanoplates was investigated. The ability to synthesize gold nanoplates with these different size ranges in large scale in aqueous solution using simple CTAB capping surfactant should allow more diverse applications of gold nanoplates.     

Growth of anisotropic gold nanostructures on conducting glass surfaces

In this paper, we describe a method for the growth of gold nanowires and nanoplates starting from a bilayer array of gold seeds, anchored on electrically conducting indium tin oxide (ITO) substrates. This is based on a seed-mediated growth approach, where the nanoparticles attached on the substrate through molecular linkages are converted to nanowires and nanoplates at certain cetyltrimethylammonium bromide (CTAB) concentration. Our modified approach can be used to make nanowires of several tens of micrometers length at a lower CTAB concentration of 0.1 M. The length of the nanowires can be varied by adjusting the time of the reaction. As the concentration of CTAB was increased to 0.25 M, the nanoparticles got converted to nanoplates. These Au nanoplates are (111) oriented and are aligned parallel to the substrate.     

Solvent-induced shape evolution of PVP protected spherical silver nanoparticles into triangular nanoplates and nanorods

The reaction between silver nitrate and poly(N-vinyl-2-pyrrolidone) (PVP) in pyridine at ambient conditions could lead to the formation of spherical nanoparticles or quadrilateral and triangular silver nanoplates, depending on the silver-to-PVP ratio used. It is proposed that the spherical Ag nanoparticles, which were formed early in the reaction, were transformed into nanoplates through an Ostwald ripening process driven by the bridging flocculation of small spherical Ag nanoparticles. This unique and hitherto unreported shape evolution process was carefully followed by a combination of techniques, viz., UV-visible spectroscopy, TEM, and powder X-ray diffraction.     

Preparation and characterization of silver nanoparticles by chemical reduction method

Silver nanoparticles were prepared by the reduction of AgNO(3) with aniline in dilute aqueous solutions containing cetyltrimethlyammonium bromide, CTAB. Nanoparticles growth was assessed by UV-vis spectroscopy and the average particle size and the size distribution were determined from transmission electron microscopy, TEM. As the reaction proceeds, a typical plasmon absorption band at 390-450nm appears for the silver nanoparticles and the intensities increase with the time. Effects of [aniline], [CTAB] and [Ag(+)] on the particle formation rate were analyzed. The apparent rate constants for the formation of silver nanoparticles first increased until it reached a maximum then decreased with [aniline]. TEM photographs indicate that the silver sol consist of well dispersed agglomerates of spherical shape nanoparticles with particle size range from 10 to 30nm. Aniline concentrations have no significant effect on the shape, size and the size distribution of Ag-nanoparticles. Aniline acts as a reducing as well as adsorbing agent in the preparation of roughly spherical, agglomerated and face-centered-cubic silver nanoparticles.     

Surface enhanced Raman scattering effects of silver colloids with different shapes

By solution-based method, three kinds of silver colloids, self-assembled nanowires, triangular nanoplates and quasispherical nanoparticles, have been synthesized. TEM studies revealed that they exposed different crystal planes, such as {111} crystal planes to triangular nanoplates, mainly {100} and {111} planes to self-assembly nanowires. Hereby, do the distinct shapes and crystal planes have an impact on the surface enhanced Raman scattering (SERS)? The great differences of the SERS spectra of rhodamine B at these Ag colloids confirmed that the shapes and crystal planes of silver have great effect on Raman enhancement, especially the crystal planes.     

Electrostatic-assembly metallized nanoparticles network by DNA template

Eighteen-nanometer gold and 3.5-nm silver colloidal particles closely packed by cetyltrimethylammonium bromide (CTAB) to form its positively charged shell. The DNA network was formed on a mica substrate firstly. Later, CTAB-capped gold or silver colloidal solutions were cast onto DNA network surface. It was found that the gold or silver nanoparticles metallized networks were formed owing to the electrostatic-driven template assembling of positive charge of CTAB-capped gold and silver particles on the negatively charged phosphate groups of DNA molecules by the characterizations of AFM, XPS and UV-vis. This method may provide a novel and simple way to studying nanoparticles assembly conjugating DNA molecules and offer some potential promising applications in nanocatalysis, nanoelectronics, and nanosensor on the basis of the fabricated metal nanoparticles network.     

Concentration of polycyclic aromatic hydrocarbons by chemically modified silver nanoparticles

The ability of silver nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) to concentrate polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions was shown. It was found that fixed PAH molecules are capable of acting as electronic energy donors and of generating sensibilized fluorescence of silver nanoparticles. It was shown by spectral-luminescent investigations of dilute PAH solutions (5 × 10⁻¹⁰−1 × 10⁻⁶ g/ml) in the presence of silver nanoparticles (∼0.7 vol %) that the concentration of PAH molecules from solutions occurs due to its sorption on hydrocarbon CTAB radicals in close contact to the surface of metallic silver. On the basis of the spectral data, the sorption isotherms were obtained and the values of extraction degree and partition coefficients for naphthalene, phenanthrene, anthracene, chrysene, pyrene, and 3,4-benzopyrene were calculated. It was found that the degree of extraction values of the investigated PAHs fall within the range of 73–98%, the partition coefficients (logD) ∼ 6, and the concentration coefficients ∼10⁵.     

Effect of ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA) on the growth, stabilization and morphology of silver nanoparticles

The effect of ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA) in stabilizing different shapes of silver nanoparticles have been examined by electronic absorption spectroscopy and transmission electron microscopy. The silver nanoparticles were prepared by two methods, i.e. γ-irradiation and chemical reduction method. Two types of effects of EGTA were identified which lead to the formation of truncated triangular silver nanoplates and chain—like silver aggregates respectively. Time-dependent infrared attenuated total reflectance (ATR-FTIR) studies showed that the nature of adsorption of EGTA on the silver nanoparticle surface influences the shape of the nanoparticles. Pulse radiolysis studies showed the mechanism of formation of the initial silver nanoclusters.