聚丙烯胺稳定铜纳米粒子的制备及其SERS活性研究

报道了聚丙烯胺稳定的球形和棒状铜纳米粒子的制备方法。在水溶液中空气条件下,通过水合肼还原二价铜离子到铜纳米粒子。聚丙烯胺的作用除稳定粒子防止聚集外,也可使粒子分散在水溶液中。该法的优点是在室温下,无需惰性气体保护,即可制备水溶液中分散的铜纳米粒子。紫外光谱和透射电镜监测了铜纳米粒子的生长过程。发现氢氧化钠的用量,聚丙烯胺浓度,反应时间等因素都影响到铜纳米粒子的组成,尺寸,形貌和聚集程度。氢氧化钠用量决定了制备粒子的组成成分是铜或氧化亚铜。所制备的球形铜纳米粒子表现出优良的表面增强拉曼散射活性。     

Carbon nanotubes as nanoparticles collector

This communication reports on a new method for the collection of nanoparticles using carbon nanotubes (CNT) as collecting surfaces, by which the problem of agglomeration of nanoparticles can be circumvented. CNT (10–50 nm in diameter, 1–10 μm in length) were grown by thermal CVD at 923 K in a 7 v/v% C₂H₂ in N₂ mixture on electroless nickel-plated copper transmission electron microscopy (TEM) grids and Monel coupons. These samples were then placed downstream of an arc plasma reactor to collect individual copper nanoparticles (5–30 nm in diameter). It was observed that the Cu nanoparticles preferentially adhere onto CNT and that the macro-particles (diameter >1 μm), a usual co-product obtained with metal nanoparticles in the arc plasma synthesis, are not collected. Cu–Ni nanoparticles, a catalyst for CNT growth, were deposited on CNT to grow multibranched CNT. CNT-embedded thin films were produced by re-melting the deposited nanoparticles.     

Regenerative synthesis of copper nanoparticles by?photoirradiation

Copper nanoparticles have attracted much attention because of their low cost, and because their use can contribute toward the sustainability of metal resources. In this study, copper nanoparticles were synthesized by the photoirradiation of copper acetate solution at room temperature. The diameter and chemical composition of the obtained copper nanoparticles were analyzed using field-emission scanning electron microscope (FE-SEM) spectrophotometer and an X-ray photoelectron spectrometer. Well-dispersed copper nanoparticles with  ~5 nm in diameter were observed in the solution. On the other hand, when the nanoparticle solution was exposed to fresh air, nanoparticles were not observed in the solution. Furthermore, the copper nanoparticles were recovered from a solution of decomposed nanoparticles by re-photoirradiation.     

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。     

One-step green route to narrowly dispersed copper nanocrystals

We report a total “green” chemical method in aqueous solution for synthesizing stable narrowly distributed copper nanoparticles with average diameter less than 5 nm in the presence of Polyvinylpyrrolidone (PVP) as a stabilizer and without any inert gas protection. In our synthesis route, ascorbic acid, natural vitamin C (VC), an excellent oxygen scavenger, acts as both reducing agent and antioxidant, to reduce the metallic ion precursor, and to effectively prevent the common oxidation process of the newborn pure copper nanoclusters.     

新型膜状金纳米活性基底的制备及拉曼光谱增强研究

贵金属纳米粒子作为增强基底已经广泛应用于表面增强拉曼光谱(SERS)研究,传统的贵金属纳米基底在制备方法、增强能力、准确性等方面仍有待改进和提高。采用一种简易、高效的方法制备出了一种具有膜状结构的新型金纳米增强基底：以聚乙烯吡咯烷酮(PVP)作保护剂和粘结剂,通过化学还原法制备金纳米基底。实验考察了还原剂种类、反应温度、体系pH和柠檬酸钠浓度对反应的影响,制备出增强效果最佳的新型膜状金纳米基底。利用罗丹明B作为探针分子,考察基底的SERS特征,其增强因子可达6.5×105。利用扫描电镜(SEM)对纳米粒子的结构进行了表征,结果表明其具有膜状结构,且比表面积大,利于分子的吸附。相比于传统的贵金属纳米基底,该实验所制备的新型膜状金纳米基底增强效果更佳、灵敏度和准确度更高,具有很大的应用前景。     

Synthesis of gold and platinum nanoparticles using tetraaniline as reducing and phase transfer agent—A brief study and their role in the electrocatalytic oxidation of glucose

A one-pot synthesis of Au and Pt nanoparticles by the spontaneous reduction of chloroaurate and chloroplatinate ions using tetraaniline molecules has been elucidated. The importance of this work is that tetraaniline acts as a multifunctional molecule that accomplishes the complexation of aqueous chloroaurate and chloroplatinate ions by phase transferring them to organic medium and their subsequent reduction to yield Au and Pt nanoparticles in organic phase. The metal reduction is followed by polymerization of the amine to yield polyaniline, which subsequently caps the Au and Pt nanoparticles. Various analytical techniques have been used for probing the process of reduction of auric and platinic metal precursors like UV-vis, X-ray diffractogram (XRD) and transmission electron micrographic (TEM) analysis. Such prepared nanoparticles are utilized for the fabrication of novel modified electrodes towards the electrocatalytic oxidation of glucose.     

Cadmium (II) pyrrolidine dithiocarbamate complex as single source precursor for the preparation of CdS nanocrystals by microwave irradiation and conventional heating process

The complex of cadmium with pyrrolidine dithiocarbamate Cd(pdtc)₂ has been used as single source precursor for the synthesis of CdS nanoparticles. The formation of CdS nanostructures was achieved by thermal decomposition of the complex under microwave irradiation and conventional heating in presence of hexadecylamine. The CdS nanoparticles with disordered close-packed structure were obtained under microwave irradiation, whereas wurtzite hexagonal phase CdS nanorods were obtained by conventional heating method (up to 150 °C). Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and high resolution transmission electron microscopy (HRTEM) studies also were carried out to study the structure and morphology of nanoparticles. The optical property of the CdS nanoparticles was studied by UV-visible and fluorescence emission spectral studies. Fluorescence measurements on the CdS nanoparticles show a strong emission spectrum with two sub bands that are attributed to band-edge and surface-defect emissions. The reduction of a suitable cadmium metal complex is considered to be one of the single pot methods to generate CdS semiconductor nanoparticles with different shapes and high yield.     

Size,composition and optical properties of copper nanoparticles prepared by laser ablation in liquids

Colloidal copper nanoparticles were prepared by pulsed Nd:YAG laser ablation in water and acetone. Size and optical properties of the nanoparticles were characterized by transmission electron microscopy and UV–visible spectrophotometry, respectively. The copper particles were rather spherical and their mean diameter in water was 30 nm, whereas in acetone much smaller particles were produced with an average diameter of 3 nm. Optical extinction immediately after the ablation showed surface plasmon resonance peaks at 626 and 575 nm for the colloidal copper in water and acetone, respectively. Time evaluation showed a blue shift of the optical extinction maximum, which is related to the change of the particle size distribution. Copper nanoparticles in acetone are yellowish and stable even after 10 months. In water, the color of the blue-green solution was changed to brown-black and the nanoparticles precipitated completely after two weeks, which is assigned to oxidation of copper nanoparticles into copper oxide (II) as was confirmed by the electron diffraction pattern and optical absorption measurements. We conclude that the ablation of bulk copper in water and acetone is a physical and flexible method for synthesis of stable colloidal copper and oxidized copper nanoparticles. PACS 42.62.-b; 81.07.-b; 61.46.+w     

微波辐射法制备水溶性CdTe量子点及其光谱学研究

用半胱胺作为稳定剂,采用微波辐射加热的方法快速合成了水溶性的CdTe量子点。吸收光谱和荧光光谱表明所合成的量子点具有优异的发光性能。透射电子显微镜(TEM)和X射线粉末衍射(XRD)表征了量子点的结构和粒径分布。通过荧光发射光谱研究了反应温度、加热时间和配体浓度对量子点晶体生长速度的影响。反应温度提高或稳定剂半胱胺的浓度减小,纳米晶体的生长速度加快。在一定温度下,随着反应时间的延长,量子点发射波长发生红移。与传统的水相回流方法相比微波加热制备水溶性的CdTe量子点具有反应速度快、得到的量子点尺寸分布均匀、半峰宽较窄和量子产率较高等特点。     

Surface plasmon band tailoring of plasmonic nanostructure under the effect of water radiolysis by synchrotron radiation

Plasmonic metal nanostructures have a significant impact on a diverse domain of fields, including photocatalysis, antibacterial, drug vector, biosensors, photovoltaic cell, optical and electronic devices. Metal nanoparticles (MNps) are the simplest nanostructure promising ultrahigh stability, ease of manufacturing and tunable optical response. Silver nanoparticles (AgNp) dominate in the class of MNps because of their relatively high abundance, chemical activity and unique physical properties. Although MNps offer the desired physical properties, most of the synthesis and fabrication methods lag at the electronic grade due to an unbidden secondary product as a result of the direct chemical reduction process. In this paper, a facile protocol is presented for fabricating high‐yield in situ plasmonic AgNps under monochromatic X‐rays irradiation, without the use of any chemical reducing agent which prevents the formation of secondary products. The ascendancy of this protocol is to produce high quantitative yield with control over the reaction rate, particle size and localized surface plasmon resonance response, and also to provide the feasibility for in situ characterization. The role of X‐ray energy, beam flux and integrated dose towards the fabrication of plasmonic nanostructures has been studied. This experiment extends plasmonic research and provides avenues for upgrading production technologies of MNps.     

Synthesis of copper nanoparticles catalyzed by pre-formed silver nanoparticles

Synthesis of well dispersed copper nanoparticles was achieved by reduction of copper nitrate in aqueous solution using hydrazine monohydrate as a reducer in the presence of preformed silver nanoparticles as catalysts. It has been demonstrated that addition of silver nanoparticles to the reaction mixture leads to formation of aqueous dispersion of copper nanoparticles and also results in a drastic reduction in reaction time compared to procedures reported in the literature. The absorption spectrum of the dispersions, HR-TEM and STEM images and XRD pattern indicate the formation of copper nanoparticles with particle size in the range of 5–50 nm.     

Size controlled synthesis of semiconductor nanocrystals in a continuous-flow mode microcapillary reactor

A microcapillary reactor with 320 μm inner diameter was utilized for CdSe nanoparticle synthesis. The influence of the reaction temperature and flow rate of precursors on the size and size distribution of prepared CdSe nanoparticles was systematically studied. The as-prepared nanoparticles exhibit sharp excitonic absorption and photoluminescence peak (FWHM 30 nm) with a quantum-yield around 10–40%. The microcapillary reactor was also used for CdSe/ZnS core-shell nanoparticle synthesis in continuous-flow mode. The quantum yield of the core-shell nanoparticles was found to be considerably influenced by the reactor temperature and have a close correlation with the thickness of ZnS shell under growth. An optimized quantum yield up to 70% was obtained for the CdSe/ZnS core-shell nanoparticles.     

Polyol mediated hexadecylamine capped silver allied nanobimetallic particles and their fluxional properties

The syntheses of hexadecylamine seed mediated Ag/M (M=Co, Ni, Pd and Pt) allied nanobimetallic particles were successfully carried out by the successive reduction of ligand capped metal ions with polyols, resulting in concomitant precipitation of some high index faceted hybrid Ag/M bimetal nanoparticles. The optical measurements revealed the existence of surface plasmon band and peak broadening that causes diffusion processes of the metal sols to decrease making it possible to monitor the changes spectrophotometrically. The bimetallic nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and electron microscopy techniques which confirm the formation of alloyed clusters.     

Synthesis and ignition of energetic CuO/Al core/shell nanowires

Energetic thermites (mixtures of Al and metal oxides), due to their high energy densities, have broad applications in propulsion, thermal batteries, waste disposal, and power generation for micro systems. Reducing the sizes of Al and metal oxides down to the nanoscale has been shown to be effective in increasing their reaction rates and reducing their ignition delays. However, it remains a challenge to create mixtures of Al and metal oxides with nanoscale uniformity. Here we report synthesis and ignition studies on thermites with a new nanostructure, i.e., CuO/Al core/shell nanowires (NWs). The CuO NW cores were synthesized by the thermal annealing of copper films and served as templates for the deposition of Al shells by subsequent sputtering. The advantage of such a core/shell NW structure is that CuO and Al are uniformly mixed at the nanoscale. The onset temperatures of the exothermic reaction of the core/shell NWs were similar to those of nanoparticle (NP)-based thermites in terms of magnitude, insensitivity to equivalence ratios and sensitivity to heating rates. Moreover, the core/shell NW thermites, compared to NP-based thermites, exhibit greatly improved mixing uniformity and reduced activation energy for the thermite reaction.     

Molecular dynamics simulations of aggregation of copper nanoparticles with different heating rates

Molecular dynamics simulations were employed to investigate the heating rates’ effect on aggregation of two copper nanoparticles. The aggregation can be distinguished into three distinct regimes by the contacting and melting of nanoparticles. The nanoparticles contacting at a lower temperature during the sintering with lower heating rate, meanwhile, some temporary stacking fault exists at the contacting neck. The aggregation properties of the system, i.e. neck diameter, shrinkage ratio, potential energy, mean square displacement (MSD) and relative gyration radius, experience drastic changes due to the free surface annihilation. After the nanoparticles coalesced for a stable period, the shrinkage ratio, MSD, relative gyration radius and neck diameter of the system are dramatically changed during the melting process. It is shown that the shrinkage ratio and MSD have relative larger increasing ratio for a lower heating rate. While the evolution of the relative gyration radius and neck diameter is only sensitive to the temperature.     

Green synthesis of gold and silver nanoparticles using gallic acid: catalytic activity and conversion yield toward the 4-nitrophenol reduction reaction

In the present report, gallic acid was used as both a reducing and stabilizing agent to synthesize gold and silver nanoparticles. The synthesized gold and silver nanoparticles exhibited characteristic surface plasmon resonance bands at 536 and 392 nm, respectively. Nanoparticles that were approximately spherical in shape were observed in high-resolution transmission electron microscopy and atomic force microscopy images. The hydrodynamic radius was determined to be 54.4 nm for gold nanoparticles and 33.7 nm for silver nanoparticles in aqueous medium. X-ray diffraction analyses confirmed that the synthesized nanoparticles possessed a face-centered cubic structure. FT-IR spectra demonstrated that the carboxylic acid functional groups of gallic acid contributed to the electrostatic binding onto the surface of the nanoparticles. Zeta potential values of ?41.98 mV for the gold nanoparticles and ?53.47 mV for the silver nanoparticles indicated that the synthesized nanoparticles possess excellent stability. On-the-shelf stability for 4 weeks also confirmed that the synthesized nanoparticles were quite stable without significant changes in their UV–visible spectra. The synthesized nanoparticles exhibited catalytic activity toward the reduction reaction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride. The rate constant of the silver nanoparticles was higher than that of the gold nanoparticles in the catalytic reaction. Furthermore, the conversion yield (%) of 4-nitrophenol to 4-aminophenol was determined using reversed-phase high-performance liquid chromatography with UV detection at 254 nm. The silver nanoparticles exhibited an excellent conversion yield (96.7–99.9 %), suggesting that the synthesized silver nanoparticles are highly efficient catalysts for the 4-nitrophenol reduction reaction.     

Microwave-assisted synthesis of CuO/ZnO and CuO/ZnO/Al2O3 precursors using urea hydrolysis

Binary CuO/ZnO and ternary CuO/ZnO/Al₂O₃ catalysts have been rapidly synthesized in a multimode microwave oven by the homogeneous precipitation of aurichalcite and hydrotalcite-like precursors using urea hydrolysis. For purposes of comparison, the same catalysts were prepared under conventional heating. The corresponding metal nitrates were mixed with various amounts of urea to yield different urea/(ΣM⁺) molar ratios. The precipitation proceeded stepwise, copper being the first metal to be hydrolyzed. It was found that the higher the urea content, the higher the alkalinization of the solution, an effect which favored the precipitation of Zn (II) (the most pH dependent metal), and in turn, the synthesis of aurichalcite and hydrotalcite-like precursors.Microwave-synthesized catalysts presented similar characteristics to those obtained under conventional heating, but in considerably reduced aging times. Microwave radiation proved to be more efficient than conventional heating under harsh conditions of precipitation, i.e., lower molar ratios of urea with respect to the metal cations in the solution.     

Microwave assisted one pot synthesis of biocompatible gold nanoparticles in Triton X-100 aqueous micellar medium using tryptophan as reducing agent

The present work reports an environmentally benign process for the synthesis of gold nanoparticles via microwave-assisted heating method, using a basic amino acid l-Tryptophan as reducing agent. The synthesis was carried out in the presence of a nonionic surfactant Triton X-100 (TX-100) aqueous micellar system. Influence of various reaction parameters such as microwave irradiation time and concentrations of precursor ion were analyzed. The effect of pH on the plasmonic properties and stability of synthesized AuNPs were studied in detail. The various size distributions of gold nanostructures obtained were characterized and analyzed by ultraviolet visible spectroscopy (UV-Vis), TEM and DLS analysis. Fourier transform infrared (FT-IR) measurements were carried out to identify the interaction sites responsible for capping and efficient stabilization by the amino acid as well as the surfactant. The synthesized gold nanoparticles were stable for more than 6 months at ambient conditions.     

液相法制备金属纳米粒子

液相法是在均相溶液中，利用各种途径引发化学反应，通过均相或异相成核及随后的扩散生长而制备出粒径分布窄且表面功能化的纳米尺度材料．介绍了液-液两相法、反相胶束、高温液相法等制备单分散金属纳米粒子的方法和高温液相法制备金属纳米粒子的影响因素，以及近年来在金属纳米粒子的制备和性能研究上的进展，尤其是Co等多种磁性纳米粒子的制备、磁性研究．