合成聚丙酰胺-硫属半导体复合纳米材料的新技术

在水溶液体系中采用同步聚合－水解技术制备聚丙烯酰胺－半导体纳米复合材料，该ＳＰＨ技术是基于丙烯胺单体的聚合和ＭＳ纳米粒子的形成同步发生，使生成的半导体纳米粒子可均匀分散在聚丙烯酰胺基质中，该技术还为制备其它有机聚合物－金属硫化物纳米复合物提供了一种新途径。     

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．     

飞秒激光直写生物凝胶模板原位合成纳米粒子

为了制备具有可控复杂形状和特定化学性质的聚合物微结构,提出了一种飞秒激光直写生物凝胶模板原位合成纳米粒子的方法。首先,采用飞秒激光直写技术加工带有COOH基团的复杂三维结构的生物凝胶模板,用氢氧化钠处理使COOH基团离子化为COO^-基团;然后,用金属盐溶液处理,使金属离子与COO^-基团螯合,形成纳米粒子结晶核。通过多次循环盐溶液处理步骤,控制模板中纳米粒子的粒径与含量。实验结果表明：所制备的生物凝胶模板具有亚100 nm分辨率和10 μm量级尺寸,纳米粒子含量高达9%。该法简单高效,具有很好的应用前景。     

用手性氨基酸制备手性纳米金粒子

正手性纳米粒子的几个潜在应用,包括光学晶体和传感器。但是,纳米金属晶体粒子制备起来却非常的困难。最近出现一个通过手性氨基酸制备手性等离子体纳米金粒子的新奇方法。韩国首尔大学(Seoul National University)的Hye-Eun Lee和同事在"种子"纳米粒子上使用手性(L或D)氨基酸,当种子生长时会倾向于另一种手性。这样生成的纳米粒子,即使在溶液     

静电纺丝法制备聚丙烯腈/银纳米粒子复合纳米纤维及其SERS特性

利用静电纺丝技术制备了一种聚丙烯腈/银纳米粒子复合纳米纤维的表面增强拉曼光谱基底。通过调节聚丙烯腈溶液的浓度可得到不同直径、不同厚度的纤维薄膜,将聚丙烯腈的N,N-二甲基甲酰胺溶液与硝酸银溶液混合得到聚丙烯腈/Ag种子溶液,然后利用静电纺丝技术制备聚丙烯腈/Ag种子/AgNO₃复合纳米纤维;加入AgNO₃并利用水合肼二次还原后可制备适合拉曼检测的聚丙烯腈/Ag纳米粒子复合纤维膜,聚合物纤维表面和内部的金属纳米粒子的密度可调节。通过调节不同的纳米粒子的密集程度,可构筑出具有较高的电磁场增强效果的特殊的“热”结构(高局域强电磁场的亚波长区域)。而聚合物纤维内部的银纳米粒子可通过溶胀作用吸附更多的探针分子,提高拉曼检测的灵敏度。该基底有很好的SERS信号,并且可大规模制备。     

金属纳米颗粒等离激元共振增强非线性介质谐波的发展现状

随着纳米加工和制备技术的不断发展,金属纳米粒子的等离激元光学特性已得到了广泛的研究与应用。本文基于金属纳米颗粒等离激元共振特性,分析了金属纳米颗粒等离激元共振对介质谐波的增强机制,综述了该增强机制在近几年所取得的最新研究成果及其在生物成像领域的应用。金属纳米颗粒等离激元共振在增强介质非线性特性领域的发展趋势是从简单的金属纳米颗粒向复杂形状纳米颗粒和金属纳米颗粒组装体的发展,这些新型金属纳米颗粒在非线性光学、生物医学上的疾病诊断和治疗有良好的实际应用前景。     

基于气相沉积等离激元纳米粒子/三维石墨烯-镍泡沫复合结构的高灵敏度表面增强拉曼检测

本文提出一种基于气相沉积银纳米粒子和三维石墨烯-镍泡沫的复合等离激元结构.该结构是利用气相纳米团簇束流技术将高密度的银纳米粒子直接沉积于三维石墨烯-镍泡沫的表面制备而成.与传统银纳米结构相比,复合三维等离激元纳米结构具有"热点"数量多,局域场更强的特点,可作为基于表面增强拉曼技术的高灵敏度化学传感器.拉曼测试实验结果表明,该三维纳米结构在表面增强拉曼检测中可获得灵敏度高,重复性好的探针拉曼信号.通过进一步的理论模拟,发现该三维等离激元结构中增强的拉曼信号主要归因于纳米粒子与纳米粒子之间以及纳米粒子与石墨烯-镍泡沫衬底之间的多重近场耦合效应.     

一种制备金纳米粒子的新方法

报道了一种温和的、低成本、有效制备高纯度单分散金纳米粒子的新方法.采用种子生长法,在表面活性剂十八烷基苄基二甲基氯化铵(BDAC)体系下液相合成金纳米粒子.通过改变实验中反应温度和反应时间等条件,制备了粒径为25-50nm的金纳米粒子,运用透射电子显微镜(TEM)对纳米粒子的形貌进行分析,利用紫外可见光谱(UV-Vis)对产物进行光谱表征,并讨论了金纳米粒子的形成机制.结果表明,金纳米粒子的粒径随反应温度的升高及反应时间的加长有增大的趋势.     

AgNPs/MIL-101(Cr)纳米复合材料的制备及其SERS光谱应用

金属有机框架(Metal Organic Frameworks,MOFs)是一类新型的多孔状的高结晶性材料。MOFs借助于过渡金属离子和有机配体的有序组装,以配位作用构筑起晶体结构。MOFs材料可作为纳米粒子的稳定载体用于与金属纳米粒子组合形成新型的纳米复合材料。这一新型的纳米复合材料可作为SERS基底应用于SERS光谱分析研究。我们将Ag纳米粒子封装在MIL-101(Cr)这种MOFs材料中,MOFs材料所具备的大的比表面积和多孔状的结构可使分析物分子预富集且更加接近金属银纳米粒子表面,从而有助于改善SERS光谱分析与检测性能。借助于多种表征手段与数据分析,我们对此纳米复合材料的制备条件进行了优化。以对巯基吡啶为光谱探针表征了该纳米复合材料的SERS光谱活性,计算了增强因子。在此基础上,将该纳米复合材料用于水溶液中超痕量葡萄糖的SERS光谱检测,探讨了应用SERS光谱技术对葡萄糖进行定量分析的可行性。     

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。     

Field emission characteristics study for ZnO/Ag and ZnO/CNTs composites produced by DC electrophoresis

A simple controllable method is reported for the coating of ZnO nanowires with Ag nanoparticles and ZnO/carbon nanotubes (CNTs) composite. It has been achieved through DC electrophoresis AgNO₃ electrolyte and CNTs in the presence of isopropanol dispersion of ZnO nanowires. In the present work, the influence of Ag nanoparticles and CNTs on the field emission properties of the composite materials is studied. The results of this research demonstrate a remarkable enhancement of field emission current of ZnO nanowires in case of CNTs mixture and Ag nanoparticles coating.     

Investigation of size distribution of silver nanoparticles

In this work, we present a physical methodology of preparing silver nanoparticles suspended in the deionized water. For this purpose, we apply the DC spark method and present the size distribution (by Zetasizer) and optical properties (by UV/VIS) of the nanoparticles in two different voltages. The obtained results using the DC spark method show that the fabrication of silver nanoparticles in deionized water without any surfactants and stabilizers is relatively cheap and pollution free. Using the method, we could prepare the silver nanoparticles smaller than 5 nm.     

Fast and economic signal processing technique of laser diode self-mixing interferometry for nanoparticle size measurement

The size of nanoparticles is measured by laser diode self-mixing interferometry, which employs a sensitive, compact, and simple optical setup. However, the signal processing of the interferometry is slow or expensive. In this article, a fast and economic signal processing technique is introduced, in which the self-mixing AC signal is transformed into DC signals with an analog circuit consisting of 16 channels. These DC signals are obtained as a spectrum from which the size of nanoparticles can be retrieved. The technique is examined by measuring the standard nanoparticles. Further experiments are performed to compare the skimmed milk and whole milk, and also the fresh skimmed milk and rotten skimmed milk.     

Time dependent magnetically induced variations in optical transmission of magnetite nanoparticle aqueous suspension

We observe time dependent variations in the light intensity transmitted through an aqueous suspension of Fe₃O₄ nanoparticles caused by applied DC magnetic field. Two types of variations can be distinguished. Fast response takes less than 1ms while slow variations occur at the time interval fromseconds to hundreds of minutes. Possible mechanisms of these variations are discussed. Formation of chain-like structures consisted from iron oxide nanoparticles is responsible for the slow variations. It is also accompanied by a diffraction pattern when the magnetic field is orthogonal to the light beam. Fast variations are due to particle rotation and reorientation of the magnetic moment inside a nanoparticle.     

Synthetic and biogenic magnetite nanoparticles for tracking of stem cells and dendritic cells

Accurate delivery of cells to target organs is critical for success of cell-based therapies with stem cells or immune cells such as antigen-presenting dendritic cells (DC). Labeling with contrast agents before implantation provides a powerful means for monitoring cellular migration using magnetic resonance imaging (MRI). In this study, we investigated the uptake of fully synthesized or bacterial magnetic nanoparticles (MNPs) into hematopoietic Flt3⁺ stem cells and DC from mouse bone marrow. We show that (i) uptake of both synthetic and biogenic nanoparticles into cells endow magnetic activity and (ii) low numbers of MNP-loaded cells are readily detected by MRI.     

Synthesis,characterization, conductivity and sensor application study of polypyrrole/silver doped nickel oxide nanocomposites

Conducting polymer composites of polypyrrole (PPy) and silver doped nickel oxide (Ag-NiO) nanocomposites were synthesised by in situ polymerisation of pyrrole with different contents of Ag-NiO nanoparticles. The formation of nanocomposites were studied by Fourier transform infrared (FTIR) and UV–vis spectroscopy, field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and AC and DC conductivity measurements. The sensitivity of ammonia gas through the nanocomposite was analysed with respect to different contents of nanoparticles. Spectroscopic studies showed the shift in the absorption bands of polymer nanocomposite than that of pure PPy indicating the strong interaction between the nanoparticles and polymer chain. FESEM revealed the uniform dispersion of nanoparticles with spherically shaped metal oxide particles in PPy matrix. The XRD pattern indicated a decrease in amorphous domain of PPy with increase in loading of nanoparticles. The higher thermal stability and glass transition temperature of polymer nanocomposites than that of pure PPy were revealed from the TGA and DSC respectively. The dielectric properties, DC and AC conductivity of nanocomposites were much higher than PPy and these electrical properties increases with the loading of nanoparticles. The nanocomposites showed an enhancement in sensitivity towards ammonia gas detection than PPy.     

Size-dependent spin-reorientation transition in Nd2Fe14B nanoparticles

It is well known that some ferromagnetic properties like Curie temperature are size dependent. In this Letter we will report that the spin-reorientation temperature of Nd₂Fe₁₄B material is also size dependent. By using a surfactant-assisted ball milling technique, Nd₂Fe₁₄B nanoparticles with different size about 6, 20 and 300 nm were successfully obtained. Spin-reorientation transition temperature of the NdFeB nanoparticles was then determined by measuring the temperature dependence of DC and AC magnetic susceptibility. It was revealed that the spin-reorientation transition temperature (Tsr) of the nanoparticles is strongly size dependent. Tsr of the 300 nm particles is lower than that of the bulk raw material while the Tsr of the 20 nm particles is significantly lower than that for the 300 nm particles. The physics behind this size dependence is discussed.     

Size controlled synthesis of ZnO nanoparticles via electric field assisted continuous spray pyrolysis (EACoSP) reactor

ZnO nanoparticles were synthesized by the continuous spray pyrolysis technique (CoSP) and the effect of applied voltage across the spray nozzle and an annular ground electrode during spray has been studied. X-ray diffraction and transmission electron microscopy studies showed that the product has (hexagonal) wurtzite structure with the average particle size decreasing from 18.5?nm to 12.9?nm in the presence of a high DC voltage (1?kV). The higher value of the absorption peak for the nanoparticles synthesized without voltage is supportive of this behavior. The films deposited by spin coating using these nanoparticles can be used for a variety of applications, particularly as photoelectrodes for dye-sensitized solar cells.     

Properties of surface dielectric barrier discharge plasma generator for fabrication of nanomaterials

This paper presents surface dielectric barrier discharge plasma generators as an efficient source of low-energy ions. Either positive or negative ions can be extracted from a plasma cloud with an external DC field created by the third electrode. Three different cross-section geometries of DBD generators were analyzed, simulated and fabricated. Currents of ions extracted from the plasma cloud were measured and the results were discussed. It was demonstrated that if the third electrode consists of liquid–gas interface, the presented arrangement can be used as a versatile reactor for nanomaterial synthesis (on the example of the synthesis of silver nanoparticles).     

Continuous synthesis of colloidal silver nanoparticles by electrochemical discharge in aqueous solutions

This article presents an electrochemical discharge (ECD) method that consists of a combination of chemical methods and electric arc discharges. In the method, 140 V is applied to an Ag electrode from a DC power supply. The arc-discharge between the electrodes produces metallic silver nanoparticles and silver ions in the aqueous solution. Compared with the original arc discharge, this ECD method creates smaller nanoparticles, prevents clumping of the nanoparticles, and shortens the production time. The citrate ions also reduce the silver ions to silver nanoparticles. In addition, the citrate ions cap the surface of the produced silver nanoparticles and the zeta potential increases. In this article, the weight loss of the electrodes and the reduction of silver ions to silver nanoparticles as a function of citrate concentration and electric conductivity of the medium are discussed. Furthermore, the properties of the colloidal silver prepared with ECD are analyzed by UV–Vis spectroscopy, dynamic light scattering, electrophoresis light scattering, and scanning electron microscopy. Finally, a continuous production apparatus is presented for the continuous production of colloidal silver.