没食子酸还原法制备金银合金纳米粒子及其吸收光谱研究

用没食子酸一步液相还原制备粒度均匀和性质稳定的Au-Ag合金纳米粒子,研究在不同反应温度和Au／Ag摩尔比下Au-Ag合金纳米粒子的吸收光谱特性。实验结果表明Au-Ag合金纳米粒子仅有1个吸收峰,介于纯Ag和纯Au纳米粒子的吸收峰之间,且随着反应温度的提高,合金纳米粒子的最大吸收峰位逐渐蓝移,吸光度增加,半峰宽变窄。随着Au/Ag摩尔比的增加,合金纳米粒子的最大吸收峰位红移,且与其所含Au摩尔百分数呈线性关系。HRTEM表征结果说明制备的Au/Ag合金纳米粒子近球形、粒度均匀、无包覆现象。EDX分析结果证实单个纳米粒子由Au和Ag组成,其元素组成比与参加反应的Au/Ag摩尔比接近。     

原料加入顺序对制备Cu/Ag纳米粒子的影响

以硫酸铜为原料制备纳米级铜粉,再用化学还原法沉积生长Ag包覆层,制备Cu/Ag复合纳米粒子,使用紫外吸收光谱法监测反应过程.结果表明.加料方式对Cu粒子的粒径会产生影响,向水合肼中滴加聚乙烯吡咯烷铜与硫酸铜的混合液能制得粒径均匀的铜纳米粒子.同时,使用向聚乙烯吡咯烷铜与硫酸铜的混合液中滴加水合肼方法制得Cu2O继而得到...     

Synthesis and characterization of Ag nanoparticles@Polyethylene fibers under ultrasound irradiation

The polyethylene fibers containing Ag nanoparticles were prepared through the chemical reduction under ultrasound irradiation. The effect of reducing reagent, power of ultrasound irradiation, reaction time and temperature in growth of the nanometric Ag were studied. Particle sizes and morphology of nanoparticle are depending on power of ultrasound irradiation. Results show a decrease in the particles size as increasing power of ultrasound irradiation. Also, an increase in temperature led to increase of particle size. The polyethylene fibers containing Ag nanoparticles were characterized with powder X-ray diffraction (XRD) and scanning electron microscopy (SEM).     

单分散银纳米颗粒的超声辅助制备及表面拉曼与荧光增强效应

以硝酸银和甲硼烷叔丁胺络合物分别为反应前驱物和还原剂,在油胺油酸体系中,利用超声辅助方法在室温下制备出粒径为3.4 nm的单分散银纳米颗粒．通过XRD、TEM和EDX对产物进行表征,结果显示产物具有典型的面心立方结构,单分散特征明显、尺寸分布均匀,且最可几尺寸为3.4 nm．超声反应时间、油胺和油酸的用量及其比例对银纳米晶的形貌和尺寸有重要影响,其中油胺溶剂的使用是控制单分散银纳米晶尺寸的关键．同时,研究显示单分散银纳米颗粒对罗丹明6G模型分子具有很强的拉曼增强效应;双光子荧光照片显示其具有很好的荧光增强效应．     

Heterogeneous nucleation and growth of silver nanoparticles on unmodified polystyrene spheres by in situ reduction

The in situ reduction growth of Ag nanoparticles (NPs) on unmodified polystyrene (PS) spheres is investigated via controlling Ag nucleation and growth rates by continuous dripping addition of reductant solution in the absence of surfactants. The sub-micro PS spheres were coated by a uniform coverage of Ag NPs with several shapes like elongated islands, spherical particles, and particle aggregates. The reaction temperature and reductant concentration are demonstrated to influence the crystal structure, distribution, and stability of the Ag NPs on the PS substrates. The heterogeneous nucleation and growth of Ag NPs on PS spheres are found to depend on the inhibition of in-solution reduction and homogeneous nucleation.     

Site‐specific deposition of Ag nanoparticles on ZnO nanorod arrays via galvanic reduction and their SERS applications

A controllable heterostructure consisting of ZnO nanorod arrays with attached Ag nanoparticles at only one end has been synthesized via a facile and convenient galvanic reduction method. Scanning electron microscopic images of these nanostructures showed good selectivity of Ag deposition on the tip of ZnO nanorod arrays. The formation of these regular Ag ZnO heterogeneous nanorod arrays can be explained by a localization of the electrons at the ends of the ZnO nanorods after the electron transfer step. By tuning the reaction time and the concentration of silver nitrate, the density of Ag nanoparticles on the tip of ZnO nanorods can be well controlled. Owing to the introduction of Ag nanoparticles with different densities, the resulting Ag ZnO heterogeneous nanorod arrays have been proved to be a versatile substrate for surface‐enhanced Raman scattering not only for common organic molecules but also for label‐free protein detection. Copyright © 2009 John Wiley & Sons, Ltd.     

Ag/TiO2纳米材料的制备和光致变色性能研究

 采用光催化还原法在不同温度热处理的TiO2薄膜表面沉积Ag纳米颗粒,制备了Ag/TiO2纳米薄膜材料。通过UV-Vis吸收光谱表征对比了不同温度热处理的TiO2对Ag粒子光催化沉积的影响,发现500℃退火处理TiO2薄膜较利于Ag纳米粒子的光催化沉积;在650 nm红色激光照射下,500℃退火处理的Ag/TiO2样品具有明显的光致变色现象,对此变色过程中涉及的机理进行了讨论,且发现随着Ag纳米颗粒光催化沉积时间的增长,Ag/TiO2薄膜光致变色的响应速率提高,但Ag纳米颗粒过多会抑制Ag/TiO2薄膜的变色响应速率。     

Synthesis of PMA stabilized silver nanoparticles by chemical reduction process under a two-step UV irradiation

Poly(methacrylic acid) (PMA) stabilized silver nanoparticles (Ag NPs), also used in the surface modification of clothing fibers, were fabricated via chemical reduction processes under UV irradiation. To obtain an uniform size distribution it has been designed a new “two-step” process which employs two different UV radiation densities in order to control the kinetics of NPs nucleation. The as produced nanoparticles were characterized by UV-vis absorption spectroscopy and TEM microscopy. The results show the reduction of the Ag ions and the nanoparticles nucleation in the first step. In the second step, the final Ag NPs size distribution is controlled through a quick cross-linking of the PMA that freezes out any further modification. A narrow size distribution with more than 80% NPs smaller than 10 nm and none larger than 25 nm was obtained and the long-term stability (one month) of the colloidal solution was verified.     

Antibacterial tourmaline nanoparticles/polyurethane hybrid mat decorated with silver nanoparticles prepared by electrospinning and UV photoreduction

In this study, tourmaline (TM) nanoparticles (NPs) were incorporated in a polyurethane (PU) matrix by electrospinning and silver (Ag) nanoparticles in the form of wire-like structure were further decorated on the TM/PU nanofibrous mat by photoreduction under ultraviolet light irradiation. The incorporation of TM NPs has increased the conductivity of the solution, thus forming thinner fiber diameters compared to neat PU, but with improved tensile strength. Wire-like, agglomerated Ag NPs were decorated on the TM/PU matrix, and exhibited high bactericidal activity depending on the Ag content. The present antibacterial Ag/TM/PU hybrid mat has potential application in water treatment.     

不同Ag壳厚度Au@Ag纳米粒子的调控制备表征及表面增强拉曼光谱的效应

采用化学还原法制备了以Au为核、包覆Ag的双金属核壳Au@Ag纳米粒子,并成功地用于表面增强拉曼光谱(SERS)分析测试。通过改变制备液中Ag/Au的量比来调控Ag壳包覆厚度。采用透射电子显微镜(TEM)和紫外-可见光谱仪(UV-Vis)对Au@Ag纳米粒子的构貌进行表征。TEM显示明显存在核壳结构,且Ag壳层随Ag/Au的量比的增加而逐渐变厚;UV-Vis表明随着Ag/Au的量比的增加,Au@Ag纳米粒子出现了Au核与Ag壳吸收峰的2个等离子体共振峰,同时伴随着Au峰的蓝移和Ag峰的红移。以双甲脒为分析物,考察了不同Ag/Au的量比时的Au@Ag纳米粒子的SERS活性。结果表明,SERS活性随Ag/Au的量比的增加先增大后减小,在6∶5时其SERS增强效应最佳,此时Ag壳厚度约为6 nm。以对巯基苯胺(4-ATP)、结晶紫(CV)和双甲脒为分析测试对象,对比了Au@Ag、Ag、Au 3种基底的SERS活性。结果表明,所制备的Au@Ag纳米粒子的SERS活性要明显优于单纯的Au、Ag纳米粒子。     

Excimer laser photofragmentation of metallic nanoparticles

Copper nanoparticles (Cu NPs) were prepared by different chemical methods possessing different sizes. While, silver nanoparticles (Ag NPs) were prepared by borohydride reduction method. The influences the changes in sizes of Ag NPs and Cu NPs were demonstrated by the absorption spectra. When Ag NPs and Cu NPs irradiated with 193 and 308 nm excimer laser, respectively; the maximum absorption decreased as the number of pulses increased up to 10 thousands pulse; due to the size reduction. The TEM photography gives good criteria about the size reduction process. Moreover, the mechanism of photofragmentation was described.     

One‐pot synthesis of silver particle aggregation as highly active SERS substrate

Silver particles with different degrees of aggregation were synthesized through a sodium dodecyl sulfate‐assisted one‐pot reaction in an aqueous medium. The products were characterized by transmission electron microscopy, scanning electron microscopy and UV‐visible spectroscopy. The results showed that the degree of aggregation of the Ag nanoparticles could be tuned by changing the reaction parameters, such as the reaction temperature and time. A possible formation process of the Ag aggregate is proposed on the basis of a series of experimental results. Moreover, the surface‐enhanced Raman scattering (SERS) effect of the Ag aggregates was evaluated by using rhodamine 6G as a Raman probe molecule. It was demonstrated that the SERS enhancement ability is related to the degree of aggregation of Ag particles, and a high SERS signal can be observed by selecting Ag nanoparticles with the proper degree of aggregation as substrates. Moreover, the aggregates showed good reproducibility and stability to SERS from organic molecules. Copyright © 2010 John Wiley & Sons, Ltd.     

新型C60衍生物／Ag复合纳米材料的制备及光谱性质

利用1,3-偶极环加成反应合成了联吡啶基C60单加成衍生物N-甲基-2-[4′-(4″-甲基-2′,2″-联吡啶基)]-3,4-C60吡咯烷(C60BPY),并用NaBH4还原法和银溶胶直接组装法制备了C60BPY/Ag复合纳米结构。透射电子显微镜(TEM)表明,两种复合纳米结构的粒子粒径分别在30~45nm和40~55nm之间,粒子形状较规则,且分散性较好。在复合纳米结构形成过程中,C60BPY分子有效地控制了银粒子的生长和团聚,起到了很好的稳定和分散作用。紫外-可见吸收光谱中,两种复合纳米结构分别在430和490nm处出现了银纳米粒子的表面等离子体共振吸收峰,说明随着粒径的增大,吸收峰发生了红移。荧光发射光谱显示,C60BPY/Ag复合纳米体系猝灭了C60BPY在720和805nm处的发射峰,并对其机理进行了探讨。这种复合纳米体系有望在光电器件、传感器及催化领域有潜在的应用前景。     

纳米银/丝素复合材料的制备及其光谱性质研究

开发可靠、生态友好的纳米材料合成方法是当今纳米技术发展的一个重要方面,基于天然生物材料如丝素蛋白原位合成来制备纳米贵金属溶胶是一种具有极大发展潜力的方法之一。文章在室温下以丝素原位还原硝酸银制得了纳米银/丝素复合溶胶,通过紫外-可见光谱、原子力显微镜、荧光光谱和共振光散射对其制备过程和光谱性质进行了表征。实验表明丝素链中的酪氨酸残基对AgNO₃还原生成纳米银颗粒起了主要作用,制得的纳米银粒子均匀地包埋在丝素胶体中,具有很好的分散性和稳定性,可长期保存。丝素蛋白与纳米银复合后,荧光强度明显增加,证明了丝素蛋白与纳米银表面之间形成了较强的化学吸附,在银表面形成了一个相对稳定的络合物致密层。同时利用共振散射光谱分析实验进一步证实了纳米银粒子的形成。     

In-situ formation of silver nanoparticles stabilized by amphiphilic star-shaped copolymer and their catalytic application

Silver nanoparticles (Ag NPs) were prepared via in situ reduction of silver nitrate (AgNO₃) using polymeric micelles as nanoreactors without any additional reductant. The micelles were constructed from the amphiphilic star-shaped copolymer composed of poly(?-caprolactone) (PCL) segment, 2-(dimethylamino)ethyl methacrylate (DMAEMA or DMA) units and oligo(ethylene glycol)monomethyl ether methacrylate (OEGMA or OEG) units. The Ag NPs stabilized by those star-shaped copolymers were characterized using UV-vis spectrum, DLS, TEM and FTIR. It confirmed that PDMAEMA exhibited the reducing property unless pH was above 7. The Ag NPs were sphere-like with a diameter of 10-20 nm, which was independent of the architecture of the copolymer and AgNO₃ concentration. Furthermore, the catalytic activity of these Ag NPs was investigated by monitoring the reduction of p-nitrophenol (4-NP) by NaBH₄. The result showed that the Ag NPs formed by coordination reduction can be effectively applied in catalytic reaction.     

In situ nucleation and growth of silver nanoparticles in membrane materials: a controllable roughened SERS substrate with high reproducibility

A controllable roughened silver surface with high surface‐enhanced Raman scattering (SERS) activity and high reproducibility has been developed in this study. This silver surface was prepared by silver nucleation in polyelectrolyte multilayers (PEMs) and silver‐enlarged growth. First, the small Ag nuclei were synthesized by NaBH₄ in situ reduction of Ag ions on a surface of PEMs. Then the small Ag nuclei formed were effectively enlarged by using a mixture of commercially available reagents named Li Silver . The optical properties and morphologies of the silver substrates have been investigated by ultraviolet–visible (UV–vis) spectroscopy and atomic force microscopy (AFM). The UV–vis and AFM results revealed that the small Ag nuclei separately appeared on the PEMs after NaBH₄ in situ reduction. The size of the enlarged Ag nanoparticles can be easily controlled with the immersing cycle in Li Silver. 4‐Mercaptopyridine (4‐MPY) and Rhodamine 6G (R6G) have been used as Raman probes to evaluate the properties of the new SERS substrates. It has been found that the enhancement factor of R6G reached ∼10⁹ after treatment in Li Silver. Reproducibility has been investigated using the SERS signal intensity at 1094 cm⁻¹ of 4‐MPY. Signals collected over multiple spots within the same substrate resulted in a relative standard deviation (RSD) of 6.38%, while an RSD of 10.33% was measured in signals collected from different substrates. Copyright © 2008 John Wiley & Sons, Ltd.     

弯曲银/银同质结纳米线的合成及其SERS表征

用液相法合成弯曲的银/银(Ag/Ag)同质结纳米线, 即由Ag/Ag同质结和Ag纳米棒组成。同质结相邻的两个Ag纳米棒以一定的角度形成弯曲的Ag纳米线, 其角度可能是锐角, 也可能是钝角, 而且其长度可达几个微米。研究发现, 反应温度对弯曲Ag/Ag同质结纳米线的形成具有非常重要的作用, 改变反应温度, 得到的是其它形状的纳米粒子; 同时, 表面增强拉曼光谱(SERS)表征发现, 与Ag纳米球和纳米线相比, 弯曲Ag/Ag同质结纳米线具有更好的SERS活性。     

SiO_2/Ag核壳结构纳米粒子的制备及其表面荧光增强

以罗丹明B掺杂的SiO2球为核,通过化学还原的方法制备了二氧化硅/银核壳结构复合纳米粒子。采用透射电镜(TEM)、紫外-可见-近红外(UV-Vis-NIR)分光光度计和荧光分光光度计对二氧化硅/银核壳结构纳米粒子的表面形貌、表面等离子共振和表面荧光增强特性进行了研究和表征。结果表明,二氧化硅/银核壳结构纳米粒子的表面等离子共振峰具有明显的可调谐性,且其表面荧光增强强烈依赖于银壳层的表面等离子共振,随银壳层厚度的增大而增强。     

Novel fabrication and catalytic application of poly(ethylenimine)-stabilized gold–silver alloy nanoparticles

Novel synthesis of amine-stabilized Au–Ag alloy nanoparticles with controlled composition has been devised using poly(ethylenimine) (PEI) as a reducing and a stabilizing agent simultaneously. The composition of Au–Ag alloy nanoparticles was readily controlled by varying the initial relative amount of HAuCl₄ and AgNO₃. Due to the presence of abundant amine functional groups in PEI, which could act as the dissolving ligand for AgCl, the precipitation problem of Ag⁺ in the presence of Cl⁻ from the gold salt was avoided. On this basis, the relatively high concentrations of HAuCl₄ and AgNO₃ salts were used for the fabrication of Au–Ag alloy nanoparticles. The PEI thus plays triple roles in this study that include the co-reducing agents for HAuCl₄ and AgNO₃, the stabilizing agents for Au–Ag alloy nanoparticles, and even the dissolving agents for AgCl. As a novel material for use in catalysis, the Au–Ag alloy nanoparticles including pure Au and Ag samples were exploited as catalysts for the reduction of 4-nitrophenol in the presence of NaBH₄. As the Au content was increased in the Au–Ag alloy nanoparticles, the rate constant of the reduction was exponentially increased from pure Ag to pure Au.     

Characterization of Ag nanoparticles on Si wafer prepared using Tollen's reagent and acid-etching

Ag nanoparticles on SiO₂/Si surfaces synthesized using the Tollen's reagent and a subsequent acid-etching were characterized using X-ray photoelectron spectroscopy (XPS). Combining the reduction of the Tollen's reagent and the chemical etching, one can create naked Ag nanoparticles with various sizes in the size range below ∼10 nanometers (nm). The reduced particle size by the chemical etching was identified using positive core level shifts with increasing etching time. Ag nanoparticles smaller than ∼3 nm undergo a reversible oxidation and reduction cycle by reacting with H₂O₂/H₂O and a subsequent heating under vacuum to 150 °C, which was not found for the bulk counterparts and larger particles, demonstrating unique chemical properties of nanoparticles compared to the bulk counterparts.