In Situ Photochemically assisted Synthesis of Silver Nanoparticles in Polymer Matrixes (original) (raw)
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Polymer stabilized silver nanoparticles: A photochemical synthesis route
Journal of Materials Science, 2000
This study describes a novel and convenient way for the preparation of polymer stabilized colloidal silver by an ultra-violet irradiation technique. Methoxypolyethylene glycol (MPEG) generates free radicals in presence of ultra-violet radiation and acts as the reducing agent towards the silver ion. MPEG also serves as a stabilizer of the silver particles formed. C 2004 Kluwer Academic Publishers
A simple method for the preparation of colloidal polymer-supported silver nanoparticles
Journal of Nanoparticle …, 2011
Polysulfone-silver composite nanoparticles have been prepared by combining polymer nanoprecipitation and redox synthesis of silver, in the presence of a glucose-modified cyclosiloxane as stabilizing agent. Based on previous kinetic investigations and on model reactions, we concluded that the reducing agent in this case is the tetrahydrofuran (THF) used as solvent for polysulfone. Dynamic light scattering measurements on the obtained polymersilver composite particles indicated particle average diameter of 176 nm with a polydispersity index of 0.25. The UV-vis spectrum exhibited the silver plasmon resonance. By different microscopic methods (atomic force microscopy-AFM, high resolution transmission electron microscopy-HRTEM, and scanning electron microscopy-SEM), larger polymer particles coated with silver nanoprticles were observed. The Energy Dispersive X-Ray analysis-EDX; confirmed the presence of Ag on the surface of the particles, while the selected area electron diffraction showed single crystalline silver nanospheres with face-centered cubic structure.
In Situ Synthesis of Silver Nanoparticles in Linear and Branched Polymer Matrices
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Silver nanoparticles were synthesized in linear and branched polymer matrices at different tempera-tures. The template role of the host linear Polyacrylamide and star-like copolymer Dextran-graft-Polyacrylamide for in situ synthesis of nanoparticles was studied by TEM, UV-Vis spectrophotometry and Dynamic light scattering. It was shown that the internal structure of polymers in solution drastically af-fects the process of Ag NPs formation. Branched polymer matrix allows to obtain a stable silver colloid even at high temperature when the linear PAA matrix is not efficient. Keywords: Silver Nanoparticles, Polyacrylamide, Branched Polymer
From silver nanoparticles to nanostructures through matrix chemistry
Journal of Nanoparticle Research, 2010
Direct in situ reduction of silver ions by a biopolymer such as agar, without any other reducing nor capping agent is shown in this article to lead either to nanoparticles (typically 12(2) nm in an optimized case) or to more complex nanostructures depending on the reaction conditions used. This approach takes advantage of the porous polymer lattice acting as a template and leads to hybrid Ag-Agar materials with long-term synergic stability. Silver acts as an antibacterial agent for agar whereas the biopolymer prevents agglomeration of the inorganic nanoparticles leading to a stable nanocomposite formed by a thermoreversible biopolymer from which silver nanoparticles can eventually be recovered.
Polymers
A chemical method was successfully used to synthesize silver nanoparticles (AgNPs) with various shapes. The shape of the nanoparticles affects the color of the colloid (spherical—yellow solution, triangular—blue, a mixture of spherical and triangular—green). The NaBH4, which acts as the main reducing agent and H2O2 have a significant impact on the shape of AgNPs. It has also been shown that the ratio between precursor, reducing, and the stabilizing agent is crucial for the formation of the required nanoparticles. The light sensitivity of AgNPs and the presence of H2O2 lead to a significant change in AgNPs’ shape and size with time and to the formation of the dichroic effect. UV–vis spectrophotometry, TEM, SEM/FIB, and EDX methods were used to analyze the shape, size, and composition of the nanoparticles. Polymer matrix composite with AgNPs was prepared by the “ex-situ” method.
Green synthesis and characterization of polymer-stabilized silver nanoparticles
Colloids and Surfaces B-biointerfaces, 2009
Silver nanoparticles (Ag-NPs) were synthesized using a facile green chemistry synthetic route. The reaction occurred at ambient temperature with four reducing agents introduced to obtain nanoscale Ag-NPs. The variables of the green synthetic route, such as acidity, concentration of starting materials, and molar ratio of reactants were optimized. Dispersing agents were employed to prevent Ag-NPs from aggregating. Advanced instrumentation techniques, such as X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (UV-vis), and phase analysis light scattering technique (ZetaPALS) were applied to characterize the morphology, particle size distribution, elemental composition, and electrokinetic behavior of the Ag-NPs. UV-vis spectra detected the characteristic plasmon at approximately 395-410 nm; and XRD results were indicative of face-centered cubic phase structure of Ag. These particles were found to be monodispersed and highly crystalline, displaying near-spherical appearance, with average particle size of 10.2 nm using citrate or 13.7 nm using ascorbic acid as reductants from particle size analysis by ZetaPALS, respectively. The rapid electrokinetic behavior of the Ag was evaluated using zetapotential (from −40 to −42 mV), which was highly dependant on nanoparticle acidity and particle size. The current research opens a new avenue for the green fabrication of nanomaterials (including variables optimization and aggregation prevention), and functionalization in the field of nanocatalysis, disinfection, and electronics.
Synthesis and characterization of silver nanoparticles
2007
Silver nanoparticles have received considerable attention due to their attractive physical and chemical properties. The surface plasmon resonance and large effective scattering cross section of individual silver nanoparticles make them ideal candidates for molecular labeling, where phenomena such as surface enhance Raman scattering (SERS) can be exploited. In addition, silver nanoparticles have recently been shown to be a promising antimicrobial material. In the present research silver colloid was produced by sodium citrate reduction. The colloidal silver was incorporated by dip-coating to the polymer substrate. X-Ray Fluorescence Spectroscopy (XRF), Atomic force microscopy (AFM), ultraviolet-visible spectroscopy (UV-VIS ) and SERS indicate that the produced structures include metallic crystalline silver nanoparticles. The surface plasmon resonance peak in absorption spectra of silver particles showed an absorption maximum at 420-500 nm. The silver - polymer nanocomposites structures with selective light properties as a result of plasmon resonance shifting in the UV-VIS wavelength region were produced.
For the past two decades, there has been considerable interest in metallic nanoparticles in applications for quantum dots and homogeneous superconductors, for magneto-optics, and optoelectronics, and for chemical and biosensors and other devices. 1À4 One of the interesting optical phenomena of metallic nanoparticles is that of localized surface plasmon resonance which is observed as strong absorptions in the UVÀvisÀNIR spectrum due to the collective oscillation of the conduction electrons in the electromagnetic field. 5,6 Since the electromagnetic field can only penetrate a certain depth (∼50 nm for Ag 7 ), the surface electrons are the most important except for small particles. The effect of the silver particle size, shape, and containing medium on the localized surface plasmon resonance is rather complex. Summarizing the literature up to the mid-1980s, Bohren and Huffman 5 report that the plasmon resonance is red-shifted (shifted to longer wavelengths) as the particle size increases, and this has been further documented by Kreibig and Genzel. 8 Thus, in a recent study of the aqueous formation of silver from silver nitrate (the silver cation acting as the oxidizer) and trisodium citrate (acting as a reducer) in acid, the observed decrease in the wavelength maximum (a blue shift) as the concentration of citrate increased was interpreted by Smitha et al. 9 as a decrease in the particle size. However, Manikandan et al. 10 reported a blue shift as the diameter of silver nanoparticles in a ceramic increased. Regarding shape, as the particles become more spherical, the absorption maximum wavelength is predicted to decrease (i.e., the absorption is blue-shifted) 11 and to lower the absorption than less spherical particles such as cubes or rods, for example. The refractive index of the particle coating or of the embedding medium also has an influence on the plasmon resonance and causes a red-shift as the index increases. 6, One of the most useful ways of utilizing the properties of metallic nanoparticles is in the form of polymer composites, and those containing silver or gold particles offer unusual spectroscopic properties, high conductivity, and antibacterial activity. Although nanocomposites were initially prepared from separately formed nanoparticles and a polymer, 13À16 in situ formation of both the polymer and metallic particle provides a greater range of potential polymeric materials and a greater control of the particle size and distribution. Carotenu et al. 17 synthesized silver nanocomposites in poly(vinylpyrrolidone) using ethylene glycol as the solvent and reducer and suggested that they could be used for advanced optical applications. De Santa Maria et al. 18 manufactured silver nanoparticles in aqueous dispersions of styre-neÀdivinyl particles for bactericidal applications by reduction of the silver salt with hydroxylamine. In order to create a composite that protects against biological warfare agents, Wu et al. prepared aqueous dispersions of inorganicÀorganic hybrids incorporating silver nanoparticles by hydrazine reduction of AgNO 3 .
Synthesis and applications of silver nanoparticles
Over the past few decades, nanoparticles of noble metals such as silver exhibited significantly distinct physical, chemical and biological properties from their bulk counterparts. Nano-size particles of less than 100 nm in diameter are currently attracting increasing attention for the wide range of new applications in various fields of industry. Such powders can exhibit properties that differ substantially from those of bulk materials, as a result of small particle dimension, high surface area, quantum confinement and other effects. Most of the unique properties of nanoparticles require not only the particles to be of nano-sized, but also the particles be dispersed without agglomeration. Discoveries in the past decade have clearly demonstrated that the electromagnetic, optical and catalytic properties of silver nanoparticles are strongly influenced by shape, size and size distribution, which are often varied by varying the synthetic methods, reducing agents and stabilizers. Accordingly, this review presents different methods of preparation silver nanoparticles and application of these nanoparticles in different fields.