A convenient approach to synthesize stable silver nanoparticles and silver/polystyrene nanocomposite particles

In this study, silver nanoparticles were prepared by the reduction of silver nitrate in SDS+ isopentanol/styrene/H₂O reverse microemulsion system using sodium citrate as reducing agent. The Ag/PS nanocomposite particles were prepared by in situ emulsion polymerization of the styrene system containing silver nanoparticles that did not separate from the reaction solution. The polymerization dynamic characteristic was studied, at the same time, silver nanparticles and the encapsulation of composite particles were characterized by Fourier‐transform‐infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X‐ray diffraction (XRD) measurement, UV–vis diffuse reflectance spectroscopy, and X‐ray photoelectron spectroscopy (XPS). The results of TEM and UV–vis absorption spectra showed that well‐dispersed silver nanoparticles have a narrow size distribution. XRD showed that Ag and Ag/PS nanocomposite particles were less than 10 and 20 nm in size, which is similar to those observed by TEM. The results of XPS spectra revealed that the microemulsion system can stabilize the silver nanoparticles from aggregation and provided supporting evidence for the polystyrene encapsulated silver nanoparticle structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

Synthesis,characterization, and bactericidal properties of composites based on crosslinked resins containing silver

Two different commercial crosslinked resins (Amberlite GT73 and Amberlite IRC748) were employed for anchoring silver. The ? SH and ? N(CH₂COOH)₂ groups, respectively, present on these resins were used for Ag⁺ chelation from an aqueous solution. The Ag⁺ ions were reduced with three different reductants: hydrazine, hydroxylamine, and formaldehyde (under an alkaline pH). The produced composites were characterized with thermogravimetry/differential thermogravimetry and scanning electron microscopy combined with a backscattered scanning electron detector. Energy‐dispersive X‐ray spectroscopy coupled to scanning electron microscopy allowed the observation of submicrometer particles of silver, and chemical microanalysis of emitted X‐rays revealed the presence of metal on the internal and external surfaces of the composite microspheres. The amount of incorporated silver was determined by titration. The antibacterial activity of the silver/resin composites was determined toward 10³–10⁷ cells/mL dilutions of the auxotrophic AB1157 Escherichia coli strain; the networks containing anchored submicrometer silver particles were completely bactericidal within a few minutes because of the combined action of silver and functional groups of the resins. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of magnetite/polyamino-ester dendrimer based on PCL/PEG amphiphilic copolymers via convergent approach for targeted diagnosis and therapy

The aim in this study is to synthesize amphiphilic linear-dendritic-linear block copolymers consisting of a poly ?-caprolactone linear block, poly(amino-ester) dendritic block and m-PEG linear block. G1, G2 and G3 dendrons were produced by sequential acrylation and Micheal addition reactions, using required amounts of acryloyl chloride and diethanolamine respectively to achieve quantitative growth. Amphiphilic dendrons were synthesized from the reaction of hydroxyl group of G1, G2 and G3 with mPEG-adipoyl chloride and their structures were characterized by FT-IR and ¹H NMR spectroscopy. The amphiphilic dendrons can self-assemble and form micelles in water. Their critical micelle concentration (CMC), particle size and zeta potential were determined by fluorescence spectroscopy and dynamic light scattering, respectively. Convergent dendrimers were prepared by self-assembly of the dendrons around oleic acid-stabilized Fe₃O₄ nanoparticles via the ligand exchange method and their morphologies were characterized by transmission electron microscopy (TEM). The in-vitro release behavior of quercetin from dendrimers and hydrolytic degradation of them were investigated at two pHs (7.4 and 5.8).     

Spherical ferroelectric PbZr0.52Ti0.48O3 nanoparticles with high permittivity: Switchable dielectric phase transition with temperature

The spherical ferroelectric PbZr_0.52Ti_0.48O₃ (PZT 52/48) nanoparticles are prepared via simple and environment friendly high temperature solid state method. The crystal structure and morphology of these particles are characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and field emission scanning electron microscopy (FESEM). XRD analysis and selected area electron diffraction (SAED) pattern of PZT particles revealed its crystalline nature. The energy involved in the synthesis especially during the initiation and termination processes for the formation of PZT particles is found from the high temperature calorimetric study. These particles are spherical in nature with an average diameter of ≤20 nm. The bulk and surface chemical composition of these particles are investigated by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). XPS study reveals that the prepared PZT particles contain titanium ion in two different oxidation states namely Ti³⁺ and Ti⁴⁺. The PZT particles exhibit high permittivity with relatively low dielectric loss. From temperature dependent dielectric analysis, it is seen that there is a switchable dielectric phase transition at or above 80 °C.     

Surface doping of TiO2 powders via a gas–melt reaction using thermal plasma as an excitation source

Surface doping is an effective method to engineer and functionalize powder materials without modulating the internal crystal structure. This study proposed a facile technique for surface doping via a gas–melt reaction using thermal plasma as an excitation source. Doping molten titania (TiO₂) particles with La was preliminarily explored owing to the broad photocatalytic applications of TiO₂. Scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, transmission electron microscope, diffuse reflectance spectroscopy, photoluminescence spectroscopy and Fourier transform infrared spectroscopy were adopted to characterize the morphology, phase composite, chemical state, fine structure, and optical property of the doped TiO₂ powder, respectively. Results indicated that molten TiO₂ doped with La solidified into spherical particles under the effect of surface tension. No modification of the internal crystal structure was indicated in the XRD patterns, except that the diffraction peak of rutile TiO₂ (110) shifted to low angles after surface doping with La. The obtained TiO₂ powder exhibited sensitivity to sunlight and near-infrared light, and a La/Ti atomic ratio of 19.4% was achieved. The diffusivity D_i of La in molten TiO₂ ranged from 10⁻⁸ m²/s to 10⁻⁷ m²/s, as determined from the gas–melt reaction.     

Morphology control and growth mechanism of magnesium hydroxide nanoparticles via a simple wet precipitation method

The nanograde particles of magnesium hydroxide [Mg(OH)₂] with needle-like and disk-like morphologies were synthesized via a simple wet precipitation method. The effects of operation parameters, such as ammonia concentration, Mg²⁺ concentration, reaction temperature and ageing temperature on morphology of magnesium hydroxide nanoparticles were investigated. The samples were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractions (XRD). The influence process and growth mechanism were discussed in details.     

Room temperature synthesis of spherical mesoporous titania

This work reports a facile hydrolysis method for the synthesis of spherical mesoporous titania particles using titanium tetrachloride under mild conditions. The method can be easily controlled or expanded. The influences of various reaction conditions including concentration of Ti⁴⁺ ions and water content on the formation of mesoporous titania particles were systematically investigated. The titania particles were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM) and Brunauer-Emmett-Teller (BET) surface areas. Experimental results showed that the mesoporous titania particles have special surface structure and excellent thermally stable mesoporous structure after annealing at high temperatures (500 °C). The effects of various reaction conditions, such as concentration of Ti⁴⁺, H₂O/n-butanol volume ratio and reaction temperature, on formation, crystal phase, morphology of titania particles were investigated.     

Small AgNP in the Biopolymer Nanocomposite System

In this work, ultra-small and stable silver nanoparticles (AgNP) on chitosan biopolymer (BP/AgP) were prepared by in situ reduction of the diamminesilver(I) complex ([Ag(NH₃)₂]⁺) to create a biostatic membrane system. The small AgNP (3 nm) as a stable source of silver ions, their crystal form, and homogeneous distribution in the whole solid membrane were confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The X-ray photoelectron spectroscopy (XPS) and Auger analysis were applied to investigate the elemental composition, concentration, and chemical state of surface atoms. It was found that ultra-small metallic nanoparticles might form a steady source of silver ions and enhance the biostatic properties of solid membranes. Ultra-small AgNP with disturbed electronic structure and plasmonic properties may generate interaction between amine groups of the biopolymer for improving the homogeneity of the nanometallic layer. In this work, the significant differences between the typical way (deposition of ex-situ-prepared AgNP) and the proposed in-situ synthesis approach were determined. The improved thermal stability (by thermogravimetry and differential scanning calorimetry (TG/DSC) analysis) for BP/AgP was observed and explained by the presence of the protective layer of a low-molecular silver phase. Finally, the antibacterial activity of the BP/AgP nanocomposite was tested using selected bacteria biofilms. The grafted membrane showed clear inhibition properties by destruction and multiple damages of bacteria cells. The possible mechanisms of biocidal activity were discussed, and the investigation of the AgNP influence on the bacteria body was illustrated by AFM measurements. The results obtained concluded that the biopolymer membrane properties were significantly improved by the integration with ultra-small Ag nanoparticles, which added value to its applications as a biostatic membrane system for filtration and separation issues.     

Preparation and characterization of Pani and Pani‐Ag nanocomposites via interfacial polymerization

Polyaniline (Pani) and Polyaniline‐silver nanocomposites (Pani‐Ag) were prepared by employing interfacial polymerization using ammonium persulphate as an oxidizing agent. During the polymerization, the Ag+ is reduced to Ag⁰, and the formations of regular nanocomposite materials were studied by Fourier transform infrared spectroscopy and UV–visible spectroscopy techniques. Scanning electron microscopy and transmission electron microscopy images were conducted to characterize the morphology. Thermogravimetric and differential thermal analysis were carried out to study the thermal stability of the resulting composites. Formation of conducting emeraldine salt form was concluded by electrical conductivity. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Swelling kinetic study and characterization of crosslinked hydrogels containing silver nanoparticles

The ammonium persulfate induced polymerization of acrylamide in the presence of silver nitrate (AgNO₃) and N,N′‐methylenebisacrylamide as a crosslinking agent were used to prepare crosslinked hydrogels containing silver ions. Subjecting this hydrogel to reduction with sodium hydroxide brought to focus the nanosilver hydrogel composites. Characterization of the latter, including proof of existence of silver nanoparticles in the hydrogel, was made. The number of silver nanoparticles embedded in the hydrogel matrix was higher at higher concentration of AgNO₃ used in the preparation of the nanosilver hydrogel composite. The characterization was performed by the use of ultraviolet–visible spectroscopy and transmission electron microscopy. The swellability of the hydrogel containing nanosilver particles was also studied, and the dependence of the swellability on the abundance of silver nanoparticles in the hydrogel composite was verified. It was further disclosed that the kinetic model matched the experimental data; meanwhile, the diffusion of water into the hydrogel was non‐Fickian type. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,Characterisation and DFT Studies of Stigmasterol Mediated Silver Nanoparticles and Their Anticancer Activity

The present investigation reports the facile, reproducible and eco-friendly biological synthesis of nano silver using Ficus Hispida leaf extract (FHLE) as a reductant. The properties of the synthesized silver nanoparticles (Ag-NP’s) is characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy (TEM), UV–visible spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction studies. The synthesized Ag-NPs are found to have spherical shape with average particle size in the range of 50–100 nm. The XRD studies and selected area electron diffraction pattern of TEM images confirm the face cantered cubic structure of biosynthesised silver nanoparticles. The DFT studies reveal that the stigmasterol present in FHLE is responsible for leaf extract to behave as a reducing agent for reduction of Ag⁺ ions into Ag⁰. The antitumor studies against DLA cell lines of the biosynthesized Ag-NPs is found to have 100% inhibition with concentration of 200 µg/ml of Ag-NP’s.     

聚苯胺-木质素磺酸纳米复合物的制备及吸附性能

以木质素磺酸(LS)为分散剂,采用静态聚合法制备了聚苯胺-木质素磺酸(PANI-LS)纳米复合物。通过扫描电子显微镜、透射电子显微镜、红外光谱、紫外可见光谱和广角X射线衍射对纳米复合物的形貌、结构和性能进行了表征。同时,研究了该纳米复合物对银离子的吸附性能。在银离子初始浓度为0.03 mol·L^-1时,PANI-LS纳米复合物对银离子的最大吸附容量为500 mg·g^-1。对吸附后纳米复合物的透射电子显微镜和广角X射线衍射的研究表明,PANI-LS纳米复合物对银离子具有还原作用,吸附后纳米复合物表面有直径为2～7 nm的单质银纳米粒子生成。     

Preparation and characterization of injection‐homo‐polypropylene filled with nano‐CaCO3

Nano‐CaCO₃/homo‐PP composites were prepared by melt‐blending using twin‐screw extruder. The results show that not only the impact property but also the bending modulus of the system have been evidently increased by adding nano‐CaCO₃. The nano‐CaCO₃ particles have been dispersed in the matrix in the nanometer scale which was investigated by means of transmission electron microscopy (TEM). The toughening mechanism of nano‐CaCO₃, investigated by means of dynamical mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM), lies on that the nano‐CaCO₃ particles take an action of initiating and terminating crazing (silver streak), which can absorb more impact energy than the neat PP. At the same time, the nano‐CaCO₃ particles, as the nuclear, decrease the crystal size of PP, the results of which were investigated by means of polarized optical microscope (POM). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Layer‐by‐layer modification of porous polybenzoxazine with silver nanoparticles for enhanced CO2 storage

Polybenzoxazine (PBZ) xerogels have been synthesized via quasi solventless method and coated with silver nanoparticles using the layer‐by‐layer (LbL) deposition method. After coating, the samples were carbonized at 800 °C to obtain high surface area porous carbon materials to be used for CO₂ storage. Evidences of the successful LbL deposition of the coating was provided by ultraviolet–visible and attenuated total reflection–Fourier transform infrared spectroscopy and the silver nanoparticles top layer was confirmed by scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy. Results showed that the samples coated with silver nanoparticles displayed an increased CO₂ capacity from 3.02 to 3.39 mmol g^?1 when compared with the plain carbon PBZ. The LbL method for the modification of the pore surface in porous PBZ is simple and allows the facile tuning of the inner PBZ pore's surface chemistry with metallic nanoparticles that could be enhanced CO₂ storage capacity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45097.     

Nanostructure silver-doped zinc oxide films coating on glass prepared by sol–gel and photochemical deposition process: Application for removal of mercaptan

Silver-doped zinc oxide (SDZO) films have been grown on glass substrate by a novel combination of sol–gel and photochemical deposition processes (SGPD). The effect of sintering on structural, electrical and optical properties was investigated. The films were characterized by UV–vis absorption spectroscopy (UV–vis), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The result of X-ray photoelectron spectroscopy (XPS) revealed that the binding energy of Ag 3d_5/2 for SDZO shifts remarkably to the lower binding energy compared to the pure metallic Ag due to the interaction between silver and zinc oxide. The XRD spectra of the SDZO films indicate that silver was incorporated in the hexagonal crystal structure of zinc oxide. SEM micrographs show the uniform distribution of spherical grains of about 73 nm grain size for the pure zinc oxide thin films. The results indicated that silver doping photochemical deposition was a feasible method to tune the optical properties of zinc oxide nanostructures. SDZO films coated on glass were applied for the photodegradation of mercaptan in water. SDZO films were applied for degradation of mercaptobenzoxazole which reduced the mercaptan concentration to more than 98%.     

Biosorption and bioreduction of diamine silver complex by Corynebacterium

Corynebacterium strain SH09 separated from a silver mine was used for biosorption and bioreduction of diamine silver complex. The biosorption of the diamine silver complex was better than that of silver ions and the maximum of the former was about 350 (mg Ag) (g dried biomass)^?1. After dried cells of SH09 were resuspended in the aqueous solution of diamine silver complex in the dark at 60 °C for more than 72 h, transmission electron microscopy (TEM) observations showed that a large quantity of black particles whose diameter ranged from 10 to 15 nm were formed on the cell wall. The particles were identified as being silver nanoparticles by X‐ray diffraction (XRD) and UV‐vis spectroscopy. Under the same conditions, no bioreduction of silver nitrate was found. According to IR spectra, some functional groups, such as the amide of the proteins, were involved in the processes of biosorption and bioreduction. Copyright © 2004 Society of Chemical Industry     

Manipulation of silver nanostructures using supercritical fluids in the presence of polyvinylpyrrolidone and ethylene glycol

This study reports on a new method for manipulating the size and shape of silver nanostructures using supercritical carbon dioxide (CO₂) in the presence of polyvinyl pyrrolidone (PVP) and ethylene glycol (EG). The temperature and pressure of CO₂ as well as the ratio of the capping agent PVP to the precursor of silver nitrate are used to control the growth of the silver nuclei and grains during the synthesis of silver nanostructures in ethylene glycol. The as-synthesized nanostructures were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and X-ray powder diffraction (XRD). The results indicate that the aspect ratio of silver nanostructures, in particular, increases with an increase in the temperature and pressure of supercritical CO₂ from 3.5 to 50.     

Hydrothermal preparation of Ag-TiO2 nanostructures with exposed {001}/{101} facets for enhancing visible light photocatalytic activity

Nano-composite materials of Ag nanoparticles dispersed TiO₂ nanocubes with exposed {001}/{101} crystal faces were fabricated mainly via a flexible one-step method of hydrothermal treatment with different content of Ag from 1 up to 3 mol%. Prepared photocatalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. These analysis was carried out for understanding the contribution of different content of silver for enhancing the photocatalytic activity of TiO₂ nanocubes. Prepared silver nanoparticles had small particle size and grafted to the {101} crystal face of TiO₂ with the role of template control agent and linking agent. The photocatalytic performance of Ag-TiO₂ nanocubes were researched via Rhodamine B dye removal under visible light irradiation ( ≧420 nm). Ag-TiO₂ composite materials with the content of 2 mol% Ag showed the best photocatalytic activity for degradation of Rhodamine B, which was five times more than bare TiO₂ and associated with the localized surface plasmon resonance (LSPR) propelled effect. The mechanism by which silver enhanced the photocatalytic activity of TiO₂ was also demonstrated.     

Preparation and Characterization of Polypyrrole Silver Nanocomposites via Interfacial Polymerization

Conducting polypyrrole silver (Ppy-AgNC) nanocomposite was synthesized by an interfacial polymerization method. Ag⁺ ions from the AgNO₃ solution were taken in the formation of Ppy-AgNC. The incorporated silver was confirmed by X-ray diffraction (XRD). During the polymerization in a nitrate ion-containing solution, the impregnation leads to the formation of metallic silver. The size distribution of Ag into the polymer is confirmed by transmission electron microscopy (TEM), and proves the formation of a uniform species with spherical particles of Ag (mean diameter of 8-12 nm) branching at the border of Ppy. The thermal behavior of the material was studied by thermogravimetric measurements.     

Preparation of colloidal silver nanoparticles by chemical reduction method

Colloidal silver nanoparticles were obtained by chemical reduction of silver nitrate in water with sodium borohydride (NaBH₄) in the presence of sodium dodecyl sulfate (SDS) as a stabilizer. The obtained nanoparticles were characterized by their UV-vis absorption spectra and transmission electron micrograph (TEM) images. The UV-vis absorption spectra showed that NaBH₄ served not only as a reducing agent but also as a stabilizer, which protects the aggregation of silver nanoparticles. The TEM images showed that the particles were dispersed better with increasing the NaBH₄ concentration.