Rapid synthesis and characterization of silver nanoparticle/bis(o-phenolpropyl)silicone composites by platinum

The formation of silver nanoparticle/bis(o-phenolpropyl)silicone composites have been promoted by the addition of chloroplatinic acid (<2 wt%) to the reaction of silver nitrate with bis(o-phenolpropyl)silicone BPPS [(o-phenolpropyl)2(SiMe2O)n, = 2, 3, 8, 236]. TEM and FE-SEM data exhibit that the silver nanoparticles having the size of <20 nm are well dispersed throughout the BPPS matrix in the composites. XRD patterns are consistent with those for polycrystalline silver. The addition of small amount of platinum to the silver accelerated the rate of composite formation by forming a Ag-Pt bimetallic alloy. The size of silver nanoparticles increased with increasing the relative molar concentration of silver salts added with respect to BPPS. However, the addition of platinum (1-5 wt%) to the AgNO3-BPPS mixture did not affect the size distribution of silver nanoparticles appreciably. It was found that in the absence of BPPS, most of the silver nanoparticles undergo macroscopic precipitation by agglomeration, indicating that BPPS is essential to stabilize the silver nanoparticles by coordination.     

A method for synthesizing the core (Ag)/shell (PSt) composite nanoparticles

Core-shell composite materials have been widely used in many fields. In this paper, the core (Ag)-shell (PSt) composite nanoparticles have been successfully fabricated in microemulsions at ambient pressure. Firstly, Ag nanoparticles with about 60-100 nm in diameters were synthesized by reducing silver nitrate by ascorbic acid, and then, styrene polymerized at the surface of Ag nanoparticles by K₂S₂O₄ initiator in microemulsion solutions. The Ag/PSt core-shell composite nanoparticles were identified by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and infrared spectra (IR). Results show that Ag-core nanoparticles were coated with ultra thin PSt shell with thickness of about 3-6 nm.     

紫外辐照法制备载银P(St-co-MMA)复合微球的研究

以聚乙烯吡咯烷酮(PVP)为分散剂,2,2-二甲氧基-2-苯基苯乙酮(BDK)为引发剂,在乙醇和水(V(乙醇)/V(水)=7/3)的混合介质中,由紫外(UV)光引发苯乙烯(St)和甲基丙烯酸甲酯(MMA)进行分散共聚,研究了影响P(St-co-MMA)收率及其微球粒径的因素;在微球分散液中加入一定浓度的AgNO3,经UV原位催化Ag+还原,制备出了负载有Ag纳米颗粒的P(St-co-MMA)复合微球。用透射电子显微镜(TEM)、激光光散射(LLS)和X射线衍射(XRD)对微球的粒径及Ag纳米颗粒的负载情况进行了表征,发现P(St-co-MMA)微球的粒径均一,可控制在500～800nm之间,Ag纳米颗粒较均匀地负载于微球的表面,平均大小为20nm。     

Preparation and characterization of aminosilane-modified silicate supported with silver for antibacterial behavior

The objective of the study was to develop and evaluate aminosilanes-modified silicate impregnated with silver (Ag) nanoparticles, in which Ag dispersion is stabilized, to create a composite that protects against biological warfare agents. A composite based on Ag and organically modified silicate (Ormosil) was prepared by an in situ reduction method, in which silver nitrate, tetraethoxysilane (TEOS) and 3-(2-aminoethylaminopropyl)trimethoxysilane (AES) acted as precursor, linker and colloidal suspension stabilizer, respectively. The physical properties of the Ormosil hybrid and Ormosil/Ag composite were examined using NMR, ESR, SEM, TEM, and TGA spectroscopy, the results of which indicated that Ag was incorporated in the Ormosil matrix after impregnation. Morphological analysis by TEM showed the resulting Ag nanoparticles to be spherical and of a mean size of less than 50 nm. The antibacterial effects of the Ormosil hybrid and the Ormosil/Ag composite were assessed by the zone of inhibition and plate-counting methods, and an excellent antibacterial performance was discovered.     

Preparation and Characterization of Nano-silver Loaded Montmorillonite with Strong Antibacterial Activity and Slow Release Property

Nano-silver loaded montmorillonite (Ag-MMT) was prepared by ion-exchange and then a UV-photoreduction two-step approach was applied. The silver content in Ag-MMT determined by Volhard method was about 6.4 wt%. The morphology and structure of as-synthesized Ag-MMT were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the Ag nanoparticles were spherical and their diameters were about 15-20 nm. Moreover, the structure of MMT did not change. The minimum inhibition concentration (MIC) of Ag-MMT was 100×10-6 and the sterilizing efficiency (SE) of Ag-MMT was approximately 100% against Escherichia coli ATCC 11229 (E. coli). In addition, the slow release property of silver in Ag-MMT was also demonstrated.     

纳米银粒子在高岭石层间的合成与表征

以高岭石-二甲基亚砜作为前驱体,用硝酸银层间取代,以高岭石的层间作为反应器来控制银粒子的大小,采用还原剂水合肼还原出单质银,制备高岭石-纳米银复合物。由红外光谱研究可知,插层作用破坏了层间氢键,二甲基亚砜与高岭石的外羟基形成了氢键,银的插入使得高岭石在2θ=38.1108～38.3942°之间出现了一个陡峭Ag(111)的衍射峰。TEM研究表明,Ag已进入层间,但粒度分布不均匀。     

Ag/GaP nanoparticles with photooxidation property under visible light

This article reports the use of Gallium phosphide (GaP) and Ag/GaP nanoparticles, which can harness visible light to decompose organic dye in aqueous solution. The Ag(1.139 wt%)/GaP and Ag(5.225 wt%)/GaP nanoparticles were prepared by the liquid phase reduction of silver nitrate with hydrazine hydrate. The application of X-ray fluorescence and high-resolution transmission electron micrograph morphology has provided direct evidence of the presence of silver on the GaP nanoparticles. Under visible light, the experiments on the photocatalytic degradation of crystal violet in solution over the GaP and Ag/GaP nanoparticles were carried out. The results reveal that small size and number density of Ag domains deposited on GaP nanoparticles have enhanced photocatalytic efficiencies, as compared to large size and number density of Ag domains. This study suggests the potential of both GaP and Ag/GaP nanoparticles as photofunctional materials for waste-water cleaning.     

Enhanced ferroelectric and dielectric properties of the P(VDF-TrFE)/Ag nanoparticles composite thin films

The scope of the present work was the synthesis of homogeneously dispersed silver (Ag) nanoparticles (NPs) in P(VDF-TrFE) polymer by N,N-dimethylformamide’s reducing reaction on silver nitrate and the study on the surface micromorphology, crystalline phases, electrical and optical properties of the P(VDF-TrFE)/Ag NPs composite thin films. The results demonstrate that incorporating appropriate concentration of Ag NPs improve the ferroelectric and dielectric properties with an increase of 38 % in the remanent polarization and 47 % in dielectric constant respectively compared with the pristine P(VDF-TrFE) films. The reasons for the improved properties are explained by the effective compensation to the bounding charges provided by the appropriate amount of the Ag NPs fillers and Ag NPs’ acting as micro capacitors in P(VDF-TrFE) matrix. Furthermore, the surface plasmon resonance absorption in the composite films thin films is observed at the wavelength of ~415 nm, whose intensity is dependent on the density of the Ag NPs.     

pH sensitive organic-inorganic layered nanomaterials by self-assembly of indigocarmine between the inorganic layers

New pH sensitive organic-inorganic intercalation compounds having different interlayer spacing were prepared. Zn-Al layered double hydroxide (LDH) is an anion exchangeable inorganic layered compound whose interlayer spacing is 0.76 nm. In the reactions of indigocarmine (IDC) with the calcined Zn-Al LDH at pH = 7 (LDH-IDC7), interlayer spacing increased to 2.25 nm. The interlayer spacing of LDH-IDC7 decreased to 1.89 nm by the treatment in basic solution. In the reaction of IDC with the calcined Zn-Al LDH at pH = 10 (LDH-IDC10), interlayer spacing of the intercalation compounds was 1.89 nm. The interlayer spacing of these intercalation compounds was changed reversibly by the treatments in acidic or basic solution.     

Polyurethane–silver fibers prepared by infiltration and reduction of silver nitrate

Silver-incorporating polyurethane fibers were prepared by infiltration of silver nitrate on electrospun polyurethane fibers and reduction with sodium borohydride. They were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray system. The Ag nanoparticles prepared by reduction of silver nitrate showed nano-sized crystals of 4–10 nm in diameter. However, larger aggregated Ag particles of 50–200 nm were also found to be dispersed in the polyurethane matrix when Ag particles were formed in electrospun fibers by the infiltration–reduction process of silver nitrate. As a result, infiltration method of silver nitrate into the electrospun fibers was significantly effective to produce silver-incorporating fibers due to a high specific surface area of fibers.     

Optimisation of nitrate reductase enzyme activity to synthesise silver nanoparticles

Today, the synthesis of silver nanoparticles (Ag NPs) is very common since it has many applications in different areas. The synthesis of these nanoparticles is done by means of physical, chemical, or biological methods. However, due to its inexpensive and environmentally friendly features, the biological method is more preferable. In the present study, using nitrate reductase enzyme available in the Escherichia coli (E. coli) bacterium, the biosynthesis of Ag NPs was investigated. In addition, the activity of the nitrate reductase enzyme was optimised by changing its cultural conditions, and the effects of silver nitrate (AgNO₃) concentration and enzyme amount on nanoparticles synthesis were studied. Finally, the produced nanoparticles were studied using ultraviolet –visible (UV–Vis) spectrophotometer, dynamic light scattering technique, and transmission electron microscopy. UV–Visible spectrophotometric study showed the characteristic peak for Ag NPs at wavelength 405–420 nm for 1 mM metal precursor solution (AgNO₃) with 1, 5, 10, and 20 cc supernatant and 435 nm for 0.01M AgNO₃ with 20 cc supernatant. In this study, it was found that there is a direct relationship between the AgNO₃ concentration and the size of produced Ag NPs.Inspec keywords: enzymes, molecular biophysics, silver, nanoparticles, nanofabrication, microorganisms, cellular biophysics, silver compounds, ultraviolet spectra, visible spectra, light scattering, transmission electron microscopyOther keywords: nitrate reductase enzyme activity, optimisation, silver nanoparticle synthesis, Escherichia coli bacterium, E. coli bacterium, biosynthesis, ultraviolet‐visible spectrophotometer, UV‐vis spectrophotometer, dynamic light scattering technique, transmission electron microscopy, supernatant, metal precursor solution, AgNO₃ ‐Ag     

Synthesis of silver-integrated silica nanostructures using rice hulls and their electrochemical performance for supercapacitor application

We report the synthesis of silver-integrated silica nanostructures using rice hulls and silver chloride through a facile thermal combustion process. The formation of mesoporous silica nanomatrix embedded with silver nanoparticles (SiO₂:Ag 5 wt% and SiO₂:Ag 10 wt%) was confirmed by XRD, FTIR, EDX, BET, and TEM analysis. Also, the obtained results from the above studies revealed that the concentration of silver ions significantly increases the particle size and number of silver nanoparticles formed in the silica matrix. The electrochemical performance was studied using silver-integrated silica nanostructures as a working electrode in KOH electrolyte. The maximum specific capacitance of SiO₂:Ag 5 wt%- and SiO₂:Ag 10 wt%-coated electrode was found to be 517 and 580 F/g at current density of 1 A/g. It was also found that SiO₂:Ag 10 wt% electrode exhibit an excellent stability with the capacitance retention of 94% than SiO₂:Ag 5 wt% (capacitance retention of 85%) after 1000 cycles at a current density of 1 A/g. These results may be attributed to the inherent characteristic of more silver nanoparticles present in the silica nanomatrix in SiO₂:Ag 10 wt%. The intrinsic characteristic of rice hull-derived silica nanostructures such as high surface area and mesoporous structure along with the advantage of silver nanoparticles (conductivity) can facilitate the Faradic redox processes at electrode surface which are responsible for the supercapacitive behavior of the prepared silver-integrated silica nanostructures.

     

Nanosilver particle formation on a high surface area titanate

Titanium based molecular sieves, such as ETS-10, have the ability to exchange silver ions and subsequently support self assembly of stable silver nanoparticles when heated. We report that a high surface area sodium titanate (resembling ETS-2) displays a similar ability to self template silver nanoparticles on its surface. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show high concentrations of silver nanoparticles on the surface of this sodium titanate, formed by thermal reduction of exchanged silver cations. The nanoparticles range in size from 4 to 12 nm, centered at around 6 nm. In addition to SEM and TEM, XRD and surface area analysis were used to characterize the material. The results indicate that this sodium titanate has a high surface area (>263 m2/g), and high ion exchange capacity for silver (30+ wt%) making it an excellent substrate for the exchange and generation of uniform, high-density silver nanoparticles.     

石墨烯/纳米银复合材料的制备、微结构及其导电性能

将不同比例的氧化石墨烯(GO)和硝酸银混合,采用水合肼一步还原制备石墨烯/纳米银(RGO/Ag)复合材料。采用UV-vis、XRD、FTIR和SEM对RGO/Ag复合材料结构组成进行表征分析,并结合热流量和结构变化研究其构成和热处理工艺对导电性的影响。结果表明:Ag基本以类似球形与石墨烯(RGO)复合;RGO/Ag复合材料的导电性与其构成有很大关系,只有当GO加入量小于50wt%时,Ag含量的提高和热处理工艺的优化可以明显改善复合材料的导电性,其中,GO加入量为16wt%的RGO/Ag片方阻值可达到8mΩ/□;当GO加入量高于50wt%时,复合材料导电性与RGO接近,受Ag含量的提高和热处理工艺优化的影响较小。     

A facile and green route to silver nanoparticles in water

Stable water-dispersible silver nanoparticles with a narrow size distribution are obtained by light-assisted spontaneous reduction of silver nitrate with gelatin, which acts as both the reducing and the stabilizing agents, in water. The formation mechanism of the silver nanoparticles involves an in-situ conversion of Ag(+)-gelatin aggregates to gelatin-stabilized silver nanoparticles via a Ag(+)-mediated oxidation of primary amine groups of the gelatin to carboxylic acid groups. The resultant silver nanoparticles are well within the quantum size domain (10 nm). In addition, the nanoparticles are stable in aqueous solutions and can be separated easily by simple pH adjustment.     

Antimicrobial and antifungal agents derived from clay minerals

A silver chelate of 2-(4-thiazolyl)-benzimidazole, dodecyltrimethylammonium cation and hexadecylpyridinium cation have been intercalated between montmorillonite, and the resulting samples were subjected to examination of their thermostabilities by thermogravimetry and carbon dioxide evolution analysis up to 500 °C in air. The degradation behaviour of the intercalant was significantly changed by intercalating between the montmorillonite layers. Two quaternary ammonium cations were released from the montmorillonite both at the same temperature, which was higher than those for the quaternary ammonium cations themselves. This relation was also observed in the case of 2-(4-thiazolyl)-benzimidazole. The improvement of the thermostability after intercalation can be attributed to the bonding between the intercalant and the host montmorillonite layers.     

Photocatalytic and antibacterial properties of a TiO2/nylon-6 electrospun nanocomposite mat containing silver nanoparticles

Silver-impregnated TiO(2)/nylon-6 nanocomposite mats exhibit excellent characteristics as a filter media with good photocatalytic and antibacterial properties and durability for repeated use. Silver nanoparticles (NPs) were successfully embedded in electrospun TiO(2)/nylon-6 composite nanofibers through the photocatalytic reduction of silver nitrate solution under UV-light irradiation. TiO(2) NPs present in nylon-6 solution were able to cause the formation of a high aspect ratio spider-wave-like structure during electrospinning and facilitated the UV photoreduction of AgNO(3) to Ag. TEM images, UV-visible and XRD spectra confirmed that monodisperse Ag NPs (approximately 4 nm in size) were deposited selectively upon the TiO(2) NPs of the prepared nanocomposite mat. The antibacterial property of a TiO(2)/nylon-6 composite mat loaded with Ag NPs was tested against Escherichia coli, and the photoactive property was tested against methylene blue. All of the results showed that TiO(2)/nylon-6 nanocomposite mats loaded with Ag NPs are more effective than composite mats without Ag NPs. The prepared material has potential as an economically friendly photocatalyst and water filter media because it allows the NPs to be reused.     

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.     

Silver nanoparticles incorporated electrospun silk fibers

We present a simple and mass-producible method of incorporating silver nanoparticles on the surface of electrospun silk non-woven membranes for the fabrication of antimicrobial wound dressings. Nanofibrous silk membranes with fiber diameters of 460 +/- 40 nm were electrospun from an aqueous Bombyx mori fibroin solution. The electrospun membranes incorporating silver nanoparticles were prepared by dipping the membranes in aqueous silver nitrate (AgNO3) solution (0.5 or 1.0 wt%) followed by photoreduction. Field emission scanning and transmission electron microscopy showed that silver nanoparticles were generated on the electrospun silk fibroin nanofibers as well as inside them. The interaction between the silver nanoparticles and amide groups in the silk fibroin molecules was characterized using X-ray photoelectron spectroscopy.     

天然石墨-纳米银/聚氨酯导电复合薄膜的制备及性能

采用热处理还原银盐原位引入银粒子的方法, 成功制备了天然石墨-纳米银/聚氨酯(C-Ag/PU)导电复合薄膜。并通过透射电镜(TEM)、 扫描电镜(SEM)观察了该复合薄膜的微观结构, 用X射线衍射仪(XRD)跟踪了银的还原和银粒子的生长过程, 探讨了加热温度和加热时间对银还原过程的影响, 研究了纳米银的生成和聚集对C/PU复合体系导电性能的影响。结果表明, 随着热处理的进行, 银粒子不断地生成和聚集, 最终以纳米尺寸(约10nm)均匀分散在聚合物基体中。纳米银粒子在天然石墨粒子之间起到了桥梁的作用, 改善了复合体系的导电通路, 显著提高了复合体系的导电性。