Embedded Silver Particles Research Articles

Electrochemical modification of the Ti[sbnd]15Mo alloy surface in solutions containing Ag2O, Ag3PO4 and Ca3(PO4)2 particles

Implants with bioactive coatings are becoming increasingly popular in bioengineering. The incorporation of silver nanoparticles into the oxide layer supports the antibacterial effect. This article describes the surface modification of Ti15Mo alloy subjected to the plasma electrochemical oxidation (PEO) process in baths containing Ag compounds: Ag2O, Ag3PO4, and Ag3PO4+ Ca(PO4)2 to incorporate antibacterial silver particles into the oxide layer on the surface of the tested alloy. Scanning electron microscopy revealed changes in the surface porosity of the obtained oxide layers. Energy dispersive analysis, Raman spectroscopy, and X-ray electron spectroscopy determined the chemical composition and distribution of elements on the sample's surface. The tests showed the presence of embedded silver particles and uniform distribution on the surface. The bioactivity of the obtained layer was tested by adhesion tests of bacteria and fungi: Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 2091).

Antibacterial Superabsorbent Polymers from Tara Gum Grafted Poly(Acrylic acid) Embedded Silver Particles.

Tara gum/silver composite superabsorbent polymers were synthesized with tara gum grafted poly(acrylic acid), using K2S2O8 (KPS) as an initiator and N,N′-methylenebisacrylamide (MBA) as a cross-linker. The products were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the silver ions were partially reduced to Ag0 and the amorphous nanoparticles containing Ag0 and Ag2O were around 10~50 nm in size The tara gum/silver composite superabsorbent polymers exhibited an interconnected porous structure with strong water absorption capacity. The swelling ratio of each product could reach 473 g/g in distilled water and 62 g/g in 0.9% NaCl solution. The antimicrobial activity of the samples against Staphylococcus aureus and Escherichia coli increased with the addition of AgNO3 from 0 to 125 mg. This work indicates that the developed tara gum/silver composite superabsorbent polymers can be potentially used for biomedical applications.

Preparation of Chitosan-Silver Nanoparticles in Nonaqueous Medium under Heating

Chitosan-silver nanoparticles are prepared in nonaqueous medium. In this work, sodium dodecyl sulfate (SDS) was introduced into the dimethylformamide (DMF) solution during silver reduction from solution of its precursor salt AgNO3, acting as a stabilizing agent to prevent aggregation of silver nanoparticles, while chitosan is used as the solid support to embedded silver particles therein, resulting in chitosan-silver (CS-Ag) nanoparticle as suspension in the medium. The reaction started as homogeneous system which turned into heterogeneous with the formation of particles. The properties of CS-Ag nanoparticles are studied under two different salt concentrations and characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). Wide particle size distribution of synthesized nanoparticles depicts that concentration of AgNO3, which is responsible for the morphology, stability and particle size distribution, should be optimized, suggesting a lower salt concentration is favorable.

Preparation of Chitosan-Silver Nanoparticles in Nonaqueous Medium under Heating

Chitosan-silver nanoparticles are prepared in nonaqueous medium. In this work, sodium dodecyl sulfate (SDS) was introduced into the dimethylformamide (DMF) solution during silver reduction from solution of its precursor salt AgNO3, acting as a stabilizing agent to prevent aggregation of silver nanoparticles, while chitosan is used as the solid support to embedded silver particles therein, resulting in chitosan-silver (CS-Ag) nanoparticle as suspension in the medium. The reaction started as homogeneous system which turned into heterogeneous with the formation of particles. The properties of CS-Ag nanoparticles are studied under two different salt concentrations and characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). Wide particle size distribution of synthesized nanoparticles depicts that concentration of AgNO3, which is responsible for the morphology, stability and particle size distribution, should be optimized, suggesting a lower salt concentration is favorable.

Multifunctional Silver Poly(vinylidene fluoride) Nanocomposites: Nanoparticle Synthesis, Film Processing, and Structural Characterization

Scope of this work was the synthesis of homogeneously dispersed silver nanoparticles in the ferroelectric polymer poly(vinylidene fluoride) (PVDF) and the study of the resulting properties affecting both the electro-active matrix and the optically-active nanofiller. In the nanocomposites surface plasmon resonances can be tuned across the UV-vis to the NIR spectral range. From IR spectra and DSC measurements it is concluded that the α- to β-phase transformation is observed and no degradation of the polymer matrix occurs. Finally, electrical poling was performed in order to investigate the influence of the embedded silver particles on the polarization behavior of the ferroelectric polymer.

Importance of lattice contraction in surface plasmon resonance shift for free and embedded silver particles

The size evolution of the surface plasmon resonance was investigated for free and embedded silver particles between about 2 to 10 nm in size. The crystal lattice of such particles as analyzed by high resolution electron microscopy show linear contraction with reciprocal particle size. Based on this, a model was presented by combining the lattice contraction of particles and the free path effect of electrons to predict the size evolution of the resonance. The results reveal a contribution of the lattice contraction to the resonance shift according to a roughly linear relation that changes slightly with particle radius (> 1.0 nm) and surrounding media. This surface plasmon resonance shift proceeds linearly with reciprocal size for Ag particles in vacuum and argon, but for Ag particles embedded in glass it appears to be independent of the radius down to nearly 1 nm. All predictions are quantitatively compared to previously reported experimental data and a good agreement is obtained. An unusual red-shift observed for Ag particles in glass may be attributed to a thermal expansion mismatch induced lattice dilatation.

Raman scattering from BaTiO 3 thin film with embedded silver particles

Raman scattering from BaTiO 3 thin films with and without embedded silver particles has been measured at room temperature. It was found that large Raman enhancement occurs in BaTiO 3 thin film with embedded silver particles. The surface-enhanced Raman scattering induced by BaTiO 3 chemically adsorbed on rough surface of silver particles is employed to explain the results.

In situ observation of microstructural changes of embedded silver particles

Thin plasma polymer films with embedded silver particles were deposited by simultaneous plasma polymerization and metal evaporation as multilayer systems. The multilayer consists of a first plasma polymer layer, a plasma polymer metal composite layer and a second plasma polymer layer, and the silver particles are embedded completely. During annealing in situ in the electron microscope, large, nearly spherical silver particles were formed. These recrystallization is a result of atomic diffusion along the particle surface and along the grain boundaries. At a multilayer system with well-separated silver particles, very small particles ( d≤10 nm) disappear during annealing, but no significant changes of the size and shape of larger (20≤ d≤60 nm) particles were found. This was interpreted as a result of atomic diffusion of silver through the polymer matrix (Ostwald ripening).

Determination of thermally induced microstructural changes of embedded metal nanoparticles by lateral and cross-sectional transmission electron microscopy

The size and shape of silver and indium nanoparticles embedded in a plasma polymer matrix formed from benzene or styrene monomer were determined by transmission electron microscopy (TEM) in lateral direction and by cross-sectional transmission electron microscopy (XTEM) in vertical direction. In multilayer assemblies consisting of plasma polymer/plasma polymer metal composite/plasma polymer [ABA], silver as well as indium nanoparticles were embedded only in one plane. XTEM micrographs on samples before and after appropriate thermal annealing (450 K) showed, that the multilayer [ABA] structure was not destroyed. At a higher annealing temperature and time (570 K, 3 h) only parts of the plasma polymer matrix were left. With all thermal annealed samples, reshapening and coalescence of the embedded silver particles was found. For multilayers with embedded indium particles, the second plasma polymer layer was formed mainly as a shell around the large particles. During thermal annealing in the electron microscope, the formation of indium oxide particles inside these shells was observed.

Electron beam initiated oxidation and coalescence of metal particles embedded in a plasma-polymer thin film matrix

Microstructural changes in plasma-polymer thin films with embedded indium or silver nanoparticles were initiated by electron beam irradiation. Oxidation of indium particles was realized by electron beam irradiation in situ with the electron microscope. By means of selected area electron diffraction it was demonstrated, that indium particles oxidize to smaller In 2O 3 crystallites. On the other hand, thermal annealing of the films results only in a formation of an indium oxide shell. At plasma-polymer films with embedded silver particles, the electron beam irradiation with a microfocus electron source results in an increase of the size of the embedded silver particles with a simultaneous decrease of the particle number (coalescence).

Electron beam induced coalescence in plasma polymer silver composite films

Plasma polymer thin films with embedded silver particles (5-50 nm) were irradiated by a small focussed electron beam of 10 kV. Before and after irradiation the films were investigated by transmission electron microscopy (TEM) to characterize the microstructure given by size and shape of the embedded silver particles. The changes of the microstructure after the electron beam irradiation were limited to small lines (<2 μm). Most changes were coalescence of the silver particles. Furthermore, after increased irradiation time and higher energy input areas nearly free of silver particles but without destruction of the plasma polymer matrix were found.

Densitometry and Photographic Printing Illumination of the Negative and Its Effect upon Density*

The nature of the photographic image is such that the value of density is dependent upon the optical system in which the image is employed. Light-scatter by the embedded silver particles has been thoroughly discussed in the literature of photography, but, for the most part only the extreme systems of densitometry—“diffuse” and “specular” have been considered. This paper summarizes the previous conclusions and extends the discussion to certain intermediate optical systems of practical importance.