Preparation of silver nanoparticles having low melting temperature through a new synthetic process without solvent

This study presents a new synthetic method of silver nanoparticles using a novel polyoxyethylene maleate-based surfactant (PEOM). Unlike conventional process using large amount of a solvent to dissolve silver salts, large amount of silver salts (AgNO3) can be dissolved and stabilized by our surfactant without solvent. Silver salts can be dissociated within PEOM by the formation of charge complex between hydrophilic-COOH segments and Ag+NO3-, resulting in formation of self-assembled microstructures which acting as a nano-reactor and stabilizer. After reduction using NaBH4, uniform sized silver nanoparticles were formed in the hydrophilic domain of PEOM. Silver contents in the colloids were changed by 0.5 approximately 3 wt%. Distribution of silver nanoparticle sizes was investigated by using TEM and XRD. Melting temperature of silver nanoparticles was measured by differential scanning calorimetry, which depends upon the particle size of silver nanoparticles. The lowest melting temperature of 112 degrees was measured from 3.5 nm average-sized silver particles.     

Fabrication of poly(FOMA-b-EO)/silver nanocomposite hybrid films

A facile synthesis of silver nanoparticles (with a diameter of 5 nm)/polymer hybrid films was studied through auto-reduction of silver nitrate (AgNO3) in poly(1H,1H-dihydroperfluorooctyl methacrylate-b-ethylene oxide) (poly(FOMA(10k)-b-EO(10k micellar thin films at ambient temperature. Silver nanoparticles well dispersed in the block copolymeric micellar films were prepared by rendering the silver precursor AgNO3 to interact favorably with PEO blocks. With annealing of the micellar film containing AgNO3 in supercritical CO2, the domains and continuous phase of the micellar film morphology were inverted and silver nanoparticles with a diameter of 10 nm were produced in PEO domains. The synthesis of silver nanoparticles in the copolymeric films was confirmed by transmission electron microscope and UV-visible spectrophotometric analysis.     

Influence of mesoporous silica and hydroxyapatite nanoparticles on the mechanical and morphological properties of polypropylene

This paper presents the effect of different types of additives on the morphology and mechanical performance of polypropylene (PP). Three different types of nanoparticles, containing mesoporous silica (MCM-41), Hydroxyapatite (HA) and the composite of MCM-41 and HA (MH) were used. Nanocomposites containing PP, 3 wt.% of maleic anhydride grafted polypropylene (PP-g-MA) and 3 wt.% of different nanoparticles were prepared using the melt-compounding technique in a twin-screw extruder. The bulk mechanical response of the nanocomposites such as tensile, flexural and Izod impact properties were studied. The results of mechanical tests show that at the same nanomaterial content, all the nanofillers cause better tensile, flexural and impact strength than neat PP. The MH nanoparticle improves the mechanical properties of PP, better than the other nanoparticles because this nanofiller contains good properties of both MCM-41 and HA nanoparticles in itself. In order to investigate the effect of foam agent on the mechanical properties of neat PP and nanocomposites based on PP, inorganic azodicarboxamide was added to the aforementioned mixtures as chemical blowing agent and the foamed specimens were resulted using the melt-compounding technique. The results reveal that addition of foam agent to mixtures, leads to increase the flexural characteristics of samples, but the tensile properties and impact strength decrease. Scanning electron microscopy (SEM) was used to assess the fracture surface morphology and the dispersion of the nanoparticles. X ray diffractometry (XRD) was used to examine the intercalation effect on the nanocomposites. The observations show that the nanomaterials were well dispersed in the polymer matrix and the enhancement of the interface between the matrix and fillers was obtained by the incorporation of MH, MCM-41 and HA nanoparticles into PP matrix.     

氰酸酯树脂/氧化石墨烯纳米复合材料的制备及表征

通过溶液插层的方法制备氰酸酯树脂/氧化石墨烯纳米复合材料,采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和热重分析(TGA)研究纳米复合材料的结构和性能,采用电子万能试验机研究纳米复合材料的力学性能。研究表明,异氰酸苯酯改性氧化石墨在二甲基甲酰胺中经超声处理后剥离形成氧化石墨烯薄片;添加氧化石墨烯后纳米复合材料的力学性能和耐热性显著改善。当氧化石墨烯的含量为基体树脂的1%时,纳米复合材料的拉伸强度、弯曲强度和冲击强度分别为82.9 MPa、148.6 MPa和12.9 kJ/m2,1000℃时的残炭率达45.1%。     

Antibacterial silver-containing silica glass prepared by ion implantation

Recently, there is much interest in nanocomposites consisting of metal nanoparticles dispersed in dielectric matrix. Silver is the first candidate used in antibacterial research. In the present study, sliver-containing silica glass is prepared by ion implantation. The bactericidal properties of Ag-implanted samples are investigated using E. coli. The implanted samples are characterized by optical absorption spectroscopy, atomic force microscopy and transmission electron microscopy. The size and position of the silver nanoparticles formed by ion implantation can be optimized by adjusting the implanted process parameters. All the implanted samples show antibacterial properties. But the samples with silver nanoparticle-enriched surfaces possess excellent antibacterial properties in comparison with other implanted samples. This indicates that ion implantation is a potential method for synthesizing antibacterial biomaterials.     

Compatibilizing effect of acrylic acid modified polypropylene on the morphology and permeability properties of polypropylene/organoclay nanocomposites

This work dealt with the morphology and permeability properties of polypropylene/organoclay nanocomposites prepared using an acrylic acid grafted polypropylene (PP-g-AA) as compatibilizing agent. Two PP-g-AA containing the same acrylic acid content (6 wt.%) and having different molar masses were tested. The o-MMT content was 0, 1 or 5 wt.% and the PP-g-AA/o–MMT mass ratio was 0/1, 1/1, 2/1 or 5/1. Results of wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM) showed that without the PP-g-AA, the o-MMT was dispersed in the PP/o-MMT in a micrometer scale, similar to a conventional microcomposite. With the PP-g-AA, the o-MMT was much better dispersed and its interlayers were intercalated and partly exfoliated by the polymer chains. CO₂ permeability values decreased for all samples with the incorporation of the organoclay. The compatibilized samples showed a more significant reduction in CO₂ permeability, up to 50% when compared to the neat PP. In general, the PP-g-AA acted satisfactorily in compatibilizing PP/organoclay nanocomposites. Moreover, samples prepared with the compatibilizer/organoclay ratio of 5/1 had better barrier properties.     

Preparation and optical properties of indium tin oxide/epoxy nanocomposites with polyglycidyl methacrylate grafted nanoparticles

Visibly highly transparent indium tin oxide (ITO)/epoxy nanocomposites were prepared by dispersing polyglycidyl methacrylate (PGMA) grafted ITO nanoparticles into a commercial epoxy resin. The oleic acid stabilized, highly crystalline, and near monodisperse ITO nanoparticles were synthesized via a nonaqueous synthetic route with multigram batch quantities. An azido-phosphate ligand was synthesized and used to exchange with oleic acid on the ITO surface. The azide terminal group allows for the grafting of epoxy resin compatible PGMA polymer chains via Cu(I) catalyzed alkyne-azide "click" chemistry. Transmission electron microscopy (TEM) observation shows that PGMA grafted ITO particles were homogeneously dispersed within the epoxy matrix. Optical properties of ITO/epoxy nanocomposites with different ITO concentrations were studied with an ultraviolet-visible-near-infrared (UV-vis-NIR) spectrometer. All the ITO/epoxy nanocomposites show more than 90% optical transparency in the visible light range and absorption of UV light from 300 to 400 nm. In the near-infrared region, ITO/epoxy nanocomposites demonstrate low transmittance and the infrared (IR) transmission cutoff wavelength of the composites shifts toward the lower wavelength with increased ITO concentration. The ITO/epoxy nanocomposites were applied onto both glass and plastic substrates as visibly transparent and UV/IR opaque optical coatings.     

Compatibilizing effect of maleated polypropylene on the mechanical properties of injection molded polypropylene/polyamide 6/functionalized-TiO2 nanocomposites

TiO₂ nanoparticles were pretreated with excessive toluene-2,4-diisocyanate to synthesize TDI-functionalized TiO₂ (TiO₂-NCO), and then the polypropylene/polyamide 6/(PP/PA6, 70/30 wt%) blends containing 3 phr of the TDI-functionalized TiO₂ were prepared using twin-screw extruder followed by injection molding. Maleated polypropylene (PP-g-MAH) was used to compatibilize the blends. The mechanical properties of PP/PA6 blends based nanocomposites were studied through tensile and flexural tests. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to assess the fracture surface morphology and the dispersion of the TDI-functionalized TiO₂, respectively. The dynamic mechanical properties of PP/PA6 based nanocomposites were analyzed by using dynamic mechanical thermal analyzer (DMTA). The strength and stiffness of the PP/PA6 compounds were improved significantly in the presence of PP-g-MAH. This has been attributed to the synergistic effect of TDI-functionalized TiO₂ and PP-g-MAH. The PP-g-MAH compatibilized PP/PA6 compounds showed a homogeneous morphology supporting the compatibility improvement between PP, PA6 and TDI-functionalized TiO₂. TEM results revealed that the TDI-functionalized TiO₂ nanoparticles were exfoliated and uniformly dispersed in blends matrix. Possible chemical interactions between PP, PA6, TDI-functionalized TiO₂ and PP-g-MAH were proposed based on the experimental work.     

Incorporation of silver nanoparticles coated with mercaptosuccinic acid/poly(ethylene glycol) copolymer into epoxy for enhancement of dielectric properties

A novel route to the synthesis of polymer-coated silver nanoparticles (NPs) was developed on the basis of the reduction of Tollens' reagent using mercaptosuccinic acid/poly(ethylene glycol) (MSA/PEG) copolymer as reducing agent and stabilizer simultaneously. The average size of the polymer-coated silver NPs could be controlled in a wide range from 10 to 120 nm by changing the MSA/PEG molar ratio. These surface-coated silver NPs can be uniformly dispersed in polar solvent and a homogeneous silver NPs/acetone dispersion has been prepared. Silver–epoxy nanocomposites have been developed by incorporating these silver NPs into epoxy. The nanocomposites with silver volume content of 25% showed a more than 3000% increase in dielectric constant as compared to neat matrix and a relatively low dielectric loss below 0.05, which meets the main requirement for embedded decoupling capacitors. Moreover, thermal properties of the silver–epoxy nanocomposites were also characterized by thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The initial decomposition temperature and glass transition temperature were elevated with the increase of silver content, which exhibit great thermal stability and facilitate electrical applications requiring higher heat-resistance.     

Size-dependent surface plasmon resonance in silver silica nanocomposites

Silver silica nanocomposites were obtained by the sol-gel technique using tetraethyl orthosilicate (TEOS) and silver nitrate (AgNO(3)) as precursors. The silver nitrate concentration was varied for obtaining composites with different nanoparticle sizes. The structural and microstructural properties were determined by x-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopic (XPS) studies were done for determining the chemical states of silver in the silica matrix. For the lowest AgNO(3) concentration, monodispersed and spherical Ag crystallites, with an average diameter of 5?nm, were obtained. Grain growth and an increase in size distribution was observed for higher concentrations. The occurrence of surface plasmon resonance (SPR) bands and their evolution in the size range 5-10?nm is studied. For decreasing nanoparticle size, a redshift and broadening of the plasmon-related absorption peak was observed. The observed redshift and broadening of the SPR band was explained using modified Mie scattering theory.     

Characterization of silver nanoparticles synthesized on titanium dioxide fine particles

Silver nanoparticles with a narrow size distribution were synthesized over the surface of two different commercial TiO(2) particles using a simple aqueous reduction method. The reducing agent used was NaBH(4); different molar ratios TiO(2):Ag were also used. The nanocomposites thus prepared were characterized using transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), dynamic light scattering (DLS) and UV-visible (UV-vis) absorption spectroscopy; the antibacterial activity was assessed using the standard microdilution method, determining the minimum inhibitory concentration (MIC) according to the National Committee for Clinical Laboratory Standards. From the microscopy studies (TEM and STEM) we observed that the silver nanoparticles are homogeneously distributed over the surface of TiO(2) particles and that the TiO(2):Ag molar ratio plays an important role. We used three different TiO(2)Ag molar ratios and the size of the silver nanoparticles is 10, 20 and 80?nm, respectively. It was found that the antibacterial activity of the nanocomposites increases considerably comparing with separated silver nanoparticles and TiO(2) particles.     

剥离型环氧树脂/蒙脱土纳米复合材料研究

采用阳离子交换的方法对蒙脱土进行了有机化处理,使蒙脱土由亲水性变成亲油性,并且使其层间距由原来的1.2nm扩大到2.2nm.采用X-射线衍射仪研究了有机蒙脱土在环氧树脂中的剥离行为,制备了环氧树脂/蒙脱土纳米复合材料并测试了其性能.实验结果表明,环氧树脂与有机蒙脱土的相容性好,蒙脱土在环氧树脂中完全剥离;环氧树脂/蒙脱土纳米复合材料的力学性能、热性能以及阻隔性能与纯环氧树脂固化物相比均有不同程度的提高和改善.     

超支化聚(胺-酯)为模板Ag纳米粒子的制备

以超支化聚(胺-酯)为模板,采用NaBH4直接还原和紫外灯光照射合成了Ag纳米粒子。超支化聚(胺-酯)对Ag纳米粒子形成起着重要的作用。TEM分析表明,Ag纳米粒子形貌为球形结构,分布均匀,粒径约为45 nm(NaBH4还原)和20 nm(紫外灯光照射)。发现在UV-Vis谱图中420 nm左右有Ag纳米粒子特征表面等离子共振吸收峰。FT-IR分析发现Ag纳米粒子和超支化聚(胺-酯)之间有较强的相互作用,超支化聚(胺-酯)对Ag纳米粒子的稳定性起保护作用。     

Study on gelatin-silver nanoparticle composite towards the development of bio-based antimicrobial film

Nano-scale silver particle stabilized by gelatin protein was prepared through the reduction of aqueous silver nitrate solution by sodium borohydride. Gelatin concentration was varied against a fixed concentration of silver nitrate to optimize the gelatin to metal ratio. Gelatin-protected Ag-nanoparticle was characterized by UV-VIS spectroscopy and transmission electron microscopy (TEM). All the samples exhibited similar yellow color with a characteristic plasmonic band of silver nanoparticles at 412 nm. TEM micrographs also showed the presence of nanoscale silver particles of approximately 3.9 nm. Since silver has strong bactericidal properties and at the same time relatively less toxic to human cell, silver in various forms is ideally suited for a wide range of applications in consumer, industrial and medical products The antimicrobial properties of gelatin-silver nanocomposites were tested by 'cup-plate zone of inhibition' method. The nanocomposites exhibited significant antibacterial and antifungal activity.     

Effect of various combinations of zirconia and organoclay nanoparticles on mechanical and thermal properties of an epoxy nanocomposite coating

An epoxy based nanocomposite coating containing various combinations of treated-zirconia and clay nanoparticles were prepared. Morphology and dispersion of nanoparticles within the nanocomposites were evaluated using optical microscopy, XRD and TEM analyses. Mechanical, thermal properties and corrosion resistance of nanocomposites were studied using; tensile strength measurements, DMTA and DSC analyses and salt spray test.The results showed that simultaneous use of spherical and plate-shape nanoparticles, have a positive effect on the clay exfoliation behavior in resulting nanocomposites.Mechanical properties of nanocomposites containing nano-zirconia slightly increased compared with neat-epoxy coating. Mechanical properties of nanocomposites containing various wt.% of clay or ZrO₂/clay nanoparticles slightly decreased; formation of physical barrier clay stacks, which leads to disturbing curing procedure and decreasing polymer cross-linking density, and development of nano-sized voids in the trapped regions by clay stacks. Corrosion performance of nanocomposites increased with addition of nanoparticles, due to improving barrier properties of the coating.     

超声诱导单分散银胶体的制备及表征

为了研究制备工艺条件对单分散银胶体稳定性的影响,在超声场作用下,以聚乙烯吡咯烷酮(PVP)为保护剂,硝酸银为前驱物,经硼氢化钾还原制备了稳定的单分散银胶体.考察了保护剂和还原剂用量、超声时间和超声功率等因素对银胶体稳定性的影响,利用透射电镜、选区电子衍射和分光光度等技术对制备的银胶体进行了表征.结果表明:银纳米粒子为面心立方(FCC)结构;PVP与AgNO3质量比为1:1时,PVP可有效保护银粒子,获得单分散的球形颗粒;AgNO3与KBH4摩尔比为1:2时,可制得单分散的类球形银纳米颗粒,直径约为20nm;超声50min制得的银胶体主要以单分散的球形纳米颗粒形式存在,粒径在10～20 nm范围内,稳定性好.     

Preparation of silver nanoparticles with antimicrobial activities and the researches of their biocompatibilities

Silver nanoparticles were prepared by chemical reduction method using chitosan as stabilizer and ascorbic acid as reducing agent in this work. The silver/chitosan nanocomposites were characterized in terms of their particle sizes and morphology by using UV spectrophotometer, nano-grainsize analyzer, and transmission electron microscopy. Antibacterial activities of these nanocomposites were carried out for Staphylococcus aureus and Escherichia coli. The silver nanoparticles exhibited significantly inhibition capacity towards these bacteria. Detailed studies on the biocompatibility of the silver/chitosan nanocomposites were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cell adhesion test. The results indicated that these silver/chitosan nanocomposites were benefit for the proliferation and adhesion of L-929 cells, and the biocompatibilities between the nanocomposites and the cells would become better with the culturing days. We anticipated that these silver/chitosan nanocomposites could be a promising candidate as coating material in biomedical engineering and food packing fields wherein antibacterial properties and biocompatibilities are crucial.     

Large-scale fabrication of Ag nanoparticles in PVP nanofibres and net-like silver nanofibre films by electrospinning

Heat treatment of various compositions of AgNO(3)-doped polyvinylpyrrolidone (PVP) composite nanofibres fabricated by electrospinning produced two kinds of silver species: (i) Ag nanoparticles dispersed in PVP nanofibres, when the loading of AgNO(3) was 5?wt%, and (ii)?a net-like silver nanofibre film when the loading of AgNO(3) was five times greater than that of PVP in the composite nanofibres. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible absorption spectroscopy, FT-IR spectra, powder x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were used to characterize the silver nanoparticles and nanofibres. The formation mechanisms are discussed based on the redox reaction between AgNO(3) and PVP during heat treatment; essentially, the weight ratios of AgNO(3) to PVP determined the types of morphologies, from Ag nanoparticles to silver nanofibre film. The present results may find some potential application in the design of new composite materials in the dielectric and electronics areas.     

Comparatively electrochemical studies at different operational temperatures for the effect of layered silicate and spherical silica on the anticorrosion efficiency of PANI nanocomposite coatings

In this paper, a series of PANI nanocomposites have been successfully prepared by in situ oxidative polymerization. The as-prepared PANI nanocomposites were subsequently characterized by WAXRD patterns and TEM. It should be noted that the nanocomposite coating containing 3 wt-% of organophilic clay loading was found to exhibit an observable enhanced corrosion protection on cold-rolled steel (CRS) electrode at higher operational temperature of 50 degrees C, which was even better than that of uncoated and electrode-coated with PANI or PANI nanocomposites with 3 wt-% of amino-modified silica nanoparticles alone at room temperature of 30 degrees C based on the electrochemical parameter evaluations (e.g., E(corr), R(p), I(corr), R(corr) and impedance). The vapor permeability property at three different operational temperatures of PANI and PANI nanocomposite membranes were investigated by vapor permeability analyzer (VPA). Effect of material composition on the molecular weight, optical properties and surface hydrophobicity of neat PANI and PANI nanocomposite, in the form of membrane and solution, were studied by gel permeation chromatography (GPC), ultraviolet-visible absorption spectra and contact-angle measurements, respectively. Finally, electrical conductivity at three different operational temperatures of PANI and PANI nanocomposite powder-pressed pellets was also investigated through the measurements of standard four-point-probe technique.     

Preparation and mechanical properties of exfoliated CoAl layered double hydroxide (LDH)/polyamide 6 nanocomposites by in situ polymerization

Novel exfoliated nanocomposites based on polyamide 6 (PA6)/CoAl layered double hydroxide (CoAl-LDH) have been successfully prepared via in situ polymerization. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated that the inorganic nanoplatelets of CoAl-LDH were homogeneously dispersed in the PA6 matrix. Mechanical testing (by tensile tests and nanoindentation measurements) shows that, compared with neat PA6, the tensile modulus, the yield strength, and the hardness of the nanocomposites are substantially improved by about 100%, 75%, and 25%, respectively, with incorporating only 1 wt% CoAl-LDH. In addition, tensile fracture morphologies of neat PA6 and its nanocomposites are also compared and discussed.