金属纳米颗粒的生物合成研究进展

金属纳米颗粒(Metal nanoparticles,MNPs)因具有小尺寸、高比表面积、高反应活性及独特的光学、电学、热力学特性,已成为催化、传感器、临床诊断、医学治疗、抗菌剂、环境修复等众多领域研究的热点材料.MNPs的种类、形貌、尺寸及表面功能修饰决定着其性能及应用范畴,开发绿色、简单、可控的MNPs合成方法是当前重要的研究方向.生物学方法合成MNPs是利用生物体或生物分子对金属离子前体进行还原或者生物矿化,反应条件温和、能耗低,无需昂贵的设备和有害的化学物质,是一种绿色合成方法,已发展为纳米生物技术的一个重要分支.几乎全部类型微生物和各种植物组织均可开发为MNPs合成与加工的"纳米工厂".细菌、放线菌、酵母和霉菌既可以在细胞内又可以在细胞外合成MNPs,MNPs的合成是生物酶催化的还原反应或者矿化过程,与细胞代谢产生的还原力有关.藻类与植物组织合成MNPs类似,通常是利用其组织提取液中的蛋白质等大分子和多酚类等多种小分子活性成分在细胞外合成MNPs.纳米尺度的病毒可作为MNPs合成与组装的特异性模板.近年来,各种各样的单质金属和金属化合物纳米颗粒的生物合成取得了较大进步,所制备的MNPs在抗菌、催化、传感、生物诊断与生物医药、环境污染物去除等方面得到较好的应用.但是生物合成MNPs仍然面临颗粒形貌、尺寸较难控制,产物不易回收和纯化,大规模生产技术欠缺等问题,因而限制了其产业化应用.本文归纳了不同类型微生物和植物组织提取液合成MNPs的最新进展,总结了MNPs的生物合成机理及应用,分析了生物合成方法面临的主要问题并展望了其未来研究方向,以期为低成本、绿色、可控生物合成MNPs的发展提供参考.     

生物合成纳米晶的研究进展

生物合成纳米材料具有独特的生物光、电、光化学等性质,为纳米材料的应用开辟了新的应用领域。生物合成主要是利用生物分子、微生物、植物及其提取物的还原特性参与纳米晶的合成,具有原料来源广,反应条件温和,产物纳米颗粒不易团聚,以及过程加入的化学试剂和产生的有毒副产物少等特点。生物合成纳米材料,就是在纳米颗粒的生长环境中加入生物分子化合物(微生物如真菌、酵母菌、细菌、放线菌和植物及其提取物),该化合物一般用作保护剂吸附在纳米颗粒的周围,以防止纳米颗粒的团聚,同样,又赋予生物纳米颗粒生物相容性,增加纳米颗粒在生物医学、食品检测等上面的应用。通过对国内外有关生物纳米晶的合成研究文献的查阅与归纳,本文对微生物、植物及其提取物等生物合成纳米晶的方法进行了综述,并对不同生物还原法所合成的纳米晶的特性进行了归纳和展望,以期对生物合成纳米晶的研究提供参考。     

纳米纤维素负载金属纳米粒子复合材料的研究进展

纳米纤维素以其独特的形态特征,优异的机械强度、生物相容性和生物降解性在纳米材料领域得到了广泛的应用.其高比表面积和丰富的活性表面基团可以通过多种物理或化学方法负载纳米金属粒子,为此,综述了银、金、铜和氧化锌等纳米金属粒子在纳米纤维素上的负载方法,并介绍了此类复合材料在抗菌材料、传感器和催化剂等领域的应用.     

线路板印刷用Cu纳米粒子的研究进展

综述了电路印刷油墨用Cu纳米粒子在合成表征及应用方面的研究现状和发展趋势,并从工艺角度对其工业化生产做出了简要分析;归纳了电路板印刷油墨用Cu纳米粒子抗氧化技术进展;展望了今后印刷电子电路中Cu纳米导电材料的研究方向。     

碳纳米管和金属纳米粒子的异质连接研究进展

碳纳米管作为金属纳米粒子的载体材料,用于催化荆、纳米电子学、光学、纳米生物技术等领域.但碳纳米管与金属之间表面张力的差异显著,不利于金属纳米粒子附着.通过碳纳米管表面改性,利用功能基团可实现较好的异质连接.分析了碳纳米管与金属纳米粒子之间的异质连接及其在功能材料中的应用研究状况,探讨了解决碳纳米管/金属复合材料界面结合问题的各种方法,展望了异质连接技术的发展趋势.     

纳米粒子表面功能化研究进展

纳米粒子表面改性包括物理改性和化学改性。物理改性一般采用高能表面改性法对纳米粒子进行修饰;化学改性分为硅烷偶联剂、酯化反应、表面接枝和表面活性剂等方法。     

表面改性纳米粒子在摩擦学领域的应用

概述了无机纳米粒子表面改性的必要性，讨论了纳米粒子的表面改性方法。在此基础上阐述了改性后的纳米粒子在摩擦学领域的研究进展，最后简述了可以适用的纳米粒子种类，指出了纳米粒子改性存在的几点问题。     

纳米细菌纤维素的生物合成

采用木醋杆茵茵株A.xylinumHN001,以椰子水为培养基,生物合成了纳米细茵纤维素(NBC).研究了影响纳米细菌纤维素合成的几个主要因素:培养时间、培养基初始pH值和培养方式.实验所得NBC的产率为1.2g/L.采用凝胶渗透色谱仪(GFC)测定了相对分子质量及其分布,其相对分子质量分布指数(MMD)约为1.0,说明相对分子质量均匀.采用透射电镜测试了形貌,证明NBC分子近似球形,直径约100nm.NBC冷冻干燥后采用红外光谱确证了结构.     

纳米粒子改性环氧树脂的研究进展

介绍了纳米复合材料的制备机理和制备方法，综述了国内外纳米粒子改性环氧树脂在力学性能、热性能、电磁性能、光学等方面的最新研究进展，并对其应用前景进行了展望，最后提出了一种新的方案，以期提高其综合性能，从而拓宽环氧树脂在电子封装材料方面的应用领域。     

包覆壳层对金属纳米粒子活性保护的研究进展

通过在金属纳米粒子表面包覆一层膜而形成核／壳结构,可以对金属纳米粒子的活性起到一定的保护作用,然而包覆层的保护效果会受到环境因素的影响。本文从湿度、酸碱度、老化时间三方面综述了环境因素对包覆壳层保护效果的影响,以及从热稳定性方面考察了包覆层的保护效果。并由此三方面和热稳定性方面提出了对包覆层的最佳选择,指出了今后的研究方向。     

Cobalt nanoparticles prepared by three different methods

This work aimed to study cobalt nanoparticles (Co-NPs) preparation using three different methods in order to evaluate the effect of synthesis variables that can influence the nanoparticle size distribution and particle shape. The synthesised nanoparticles were characterised by Transmission Electron Microscopy. The first synthesis employed decomposition of Co₂(CO)₈, at high temperatures. This procedure resulted in spherical nanoparticles with low size distribution. The size of Co-NPs could be tuned by modification of precursor/surfactant, nevertheless the stirring and injection time influenced the size distribution. Using polyol process, at high temperatures, it was produced undefined-shape nanoparticles. This result suggests that the solution composition, i.e. the amount of trioctylphosphine and oleic acid was not suitable to control both size and shape of nanoparticles. Finally, the method based on reduction with NaBH₄ resulted spherical nanoparticles with tiny sizes, indicating that in this case a variation on amount of reductant would be more efficient on the particle size control than a variation in concentration of oleic acid. These results indicated that, for each method, a different variable exists for the control of the distribution size and the shape of the formed particles.     

Role of metal and dielectric nanoparticles in the performance enhancement of silicon solar cells

The suitability of using spherical metal and dielectric nanoparticles on the top of a silicon solar cell has been investigated. An enhancement index factor (EIF) for each wavelength of light and an averaged EIF for the AM 1.5 solar spectrum, weighted by the photon flux, has been introduced. These factors estimate the effect of the nanoparticles in improving the performance of the solar cells, considering the absorption loss due to joule heating, fraction of radiation scattered into the substrate and the front scattered radiation pattern. A systematic comparison between silver and dielectric nanoparticles (silica, silicon nitride, titanium dioxide) shows that titanium dioxide and silicon nitride nano particles of sizes ≥100?nm exhibit larger enhancements compared to that of silver nanoparticles of similar sizes. Further, as the dielectric constant of the dielectric nanoparticles increases, the optimal particle size corresponding to maximal enhancement shifts towards lower value. At optimal particle sizes, the enhancement is 1.5–2 times greater than that due to silver nanoparticles.     

Modification of magnetic properties of metal nanoparticles using nanotemplate approach

We demonstrate a nanotemplate approach by which different metal magnetic nanoparticles (Ni–Co, Ni–Fe and Co–Pt alloy particles) can be fabricated on a polyimide (PI) film. The process relies on the high interfacial energy between deposited metal and the PI film which forces the deposited metal film to preferentially nucleate on the pre-existing Ni seed particles. During subsequent thermal annealing, the deposited metal film coalesced onto the Ni seed particles to form a monolayer of magnetic nanoparticles on the PI film. Furthermore, the deposition/annealing can be repeated to change both size and constituent of the nanoparticles by introducing a different metal film during deposition. Potentially, any metal film can be deposited onto the Ni seed particles provided that the metal does not react with the Ni seed particles to create a monolayer of metal nanoisland structures with desire magnetic properties.     

Reagent control over the composition of mixed metal oxide nanoparticles

Binary (M¹ ? M² ? O) and ternary (M¹ ? M² ? M³ ? O) metal-oxide nanoparticles (NPs) have been prepared by thermal decomposition in benzyl ether of the appropriate M(acac)_n (M = Fe, Mn, Pd, Cu, Al, Gd) compounds in the presence of a mixture of oleic acid and oleylamine templating (surface capping) ligands, and 1,2-hexadecanediol as an accelerating agent. The metal percentage and the particle size were investigated as a function of the starting composition. The NP composition is controlled by the relative reaction rates of the particular precursors, such that prediction of NP composition from reagent ratios is not straightforward. However, understanding reaction rate limitations allows for alternative synthesis to be developed. In some cases, ligand exchange reaction and subsequent decomposition are possibly more important than thermal decomposition.     

Preparation and characterisation of nanoparticles containing ketoprofen and acrylic polymers prepared by emulsion solvent evaporation method

We have prepared polymeric drug nanoparticles by oil in water (O/W) emulsion solvent evaporation method. We used acetone as solvent for polymer and water as non-solvent. The purpose of this study is to use the emulsion solvent evaporation method in order to prepare nanoparticles and to investigate the effects of the various processing parameters to the characteristics of the nanoparticles. In this research, we use two different forms of acrylic polymers, Eudragit E100 and Eudragit RS. It was found that the size of the nanoparticles depends on different parameters such as the polymer concentration in the organic solvent, surfactant concentration and the volume ratio of oil and water phases. The morphology structure is investigated by transmission electron microscope (TEM). TEM images confirmed that the nanoparticles produced were spherical in shape and the successfully prepared nanoparticles with size 80?nm. The size distribution is measured by laser dynamic light scattering. The size distribution of the nanoparticles was found in the range from 50 to 150?nm. Investigation of Fourier transform infrared spectroscopy indicated the absence of the interactions between the drug and polymer. X-ray diffraction patterns of nanoparticles containing ketoprofen, Eudragit E100 and Eudragit RS showed the amorphous structure.     

Porous ternary complex metal oxide nanoparticles converted from core/shell nanoparticles

We demonstrate an easy and scalable low-temperature process to convert porous ternary complex metal oxide nanoparticles from solution-synthesized core/shell metal oxide nanoparticles by thermal annealing. The final products demonstrate superior electrochemical properties with a large capacity and high stability during fast charging/discharging cycles for potential applications as advanced lithium-ion battery (LIB) electrode materials. In addition, a new breakdown mechanism was observed on these novel electrode materials.

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联氨还原法制备铜纳米粒子

在表面活性剂聚乙烯吡咯烷酮(PVP)的保护下,采用水合肼于水体系中还原铜盐而得到铜纳米粒子。通过XRD检验确认该种方法合成的铜纳米粒子具有fcc相;XPS的表征结果显示:铜纳米粒子表面价态为零价,说明制备过程中没有被氧化;用透射电镜和激光光散射仪对粒子的表面形貌和粒径进行了表征分析,结果显示粒径在35nm左右,近似圆球形,在正己烷中分散效果较好。     

液相法制备纳米粒子的粒径控制研究

液相法是目前制备纳米粒子的重要方法之一.本文简要地阐述了液相法制备纳米粒子时粒径控制的机理,并在液相法过程特征的基础上,重点分析了影响粒径分布和形状控制的几个最主要因素,详细解释了化学计量学方法在控制纳米粒子粒度及其分布方面的应用.     

现代计量测试技术的进展

基于中国计量研究院在计量学领域里的前沿研究成果,介绍了国际上现代计量技术的发展趋势.     

Quantum size effect in TiO2 nanoparticles prepared by finely controlled metal assembly on dendrimer templates

The use of dendrimer templates to make metal-based nanoparticles of controlled size has attracted much interest. These highly branched macromolecules have well-defined structures that enable them to bind metal ions to generate precursors that can be converted into nanoparticles. We describe the sub-nanometre size control of both anatase and rutile forms of TiO2 particles with phenylazomethine dendrimers, leading to samples with very narrow size distributions. Such fine tuning is possible because both the number and location of metal ions can be precisely controlled in these templates. Quantum size effects are observed in the particles, and the energy gap between the conduction and valence bands exhibits a blueshift with decreasing particle size and is dependent on the crystal form of the material. The dependency of the bandgap energy on these factors is explained using a semi-empirical effective mass approximation.