Papers by Keyword: Silver

Abstract: Human beings are often infected by microorganisms in the living environment. Among various natural and inorganic substances, silver or silver ions have a powerful antibacterial activity. In the present study, the bioactivity and antibacterial activity of the SiO₂–CaO–P₂O₅–Ag₂O was compared with that of its ternary counterpart glass system (as a control sample) in vitro. The molar ratio of silver oxide in the bioactive glass composition was considered as different amount (0.5%, 1% and 2%). The surface characterization was evaluated after soaking in simulated body fluid (SBF). The sharpest apatite peak in X-ray diffraction (XRD) analyse after 7 days soaking in SBF was observed for 2% Ag sample (2%Ag-BG). Hence, the antibacterial effects of 2%Ag-BG sample against 2 gram negatives bacterium were examined by agar plate test. The result showed that the amount of silver did not prevent the HAp formation. Also, the antibacterial properties of 2%Ag-BG sample indicated near 100% bactericidal ratio (according to the width of antibacterial halo).

Abstract: In this paper, we studied growth of AlN/GaN/AlN on Si (111) by using plasma assisted molecular beam epitaxy (PA-MBE) system. The structural and optical characteristics of the sample have been investigated by using high resolution X-ray diffraction (HR-XRD), Raman spectroscopy and photoluminescence (PL). PL spectrum of the sample has shown sharp and intense band edge emission of GaN with the absence of yellow emission band, indicating good crystal quality of the sample. The silver (Ag) metal contact was then deposited on the sample followed by thermal treatment at 500°C and 700°C, respectively. Treated sample at 700°C showed good spherical Ag islands on sample compared to the treated sample at 500°C. The effect of Ag islands on the electrical characteristics of sample was also examined by using I-V measurement. The results showed that the treated sample at 700°C has decreased the photo-current of Schottky diode.

Abstract: In this work, different thicknesses of silver (Ag) thin films were prepared on flexible polyethylene terephthalate (PET) plastic substrates by screen printing technology. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize morphology and surface roughness of the Ag thin films. Crystallinity and crystallites sizes of the films were verified on High resolution X-ray diffraction (HR-XRD) system. From the AFM, rough surfaces were revealed with root mean square surface roughness (RMS) ranging from 20 to 40 nm for different thicknesses of the films and were found to be strongly dependent on the film thickness. The HR-XRD spectra showed different crystalline orientations of Ag thin films (with various thicknesses) produced by the screen printing technique. All the experimental findings were subsequently discussed.

Abstract: A facile method for the synthesis of silver nanoparticles (NPs) has been developed by using sodium phosphate (Na3PO4) as stabilizing agents and glucose the reducing agent, respectively. The obtained silver NPs have been characterized by X-ray diffraction (XRD), UV-visible spectroscopy (UV-vis) and transmission electron microscopy (TEM). It was found that in the presence of sodium phosphate, silver NPs with different morphologies and sizes were obtained. The formation mechanism of diverse silver NPs was studied preliminarily.

Abstract: Silver nanoparticles have been prepared using a “terminated gas condensation” technique. An unprecedented control of 5-6 nm-size nanoparticles with well defined shape and variable surface densities has been achieved. The technology is shown to permit independent control of both, plasmon resonance intensity and frequency position. On the basis of optical measurements, a smart tuning of plasmon resonance intensity with particle density is indeed demonstrated. Moreover, the embedding of NPs in different surrounding medium enables to control the resonance wavelength as experimentally demonstrated and theoretically confirmed.

Abstract: Aggregation problem limits the use of silver nanoparticles (nano-Ag). Liquid chemical reduction method was used to fabricate silver/hydroxyapatite nanoparticles (nano-Ag/HA) by depositing nano-Ag on the surface of hydroxyapatite nanoparticles (nano-HA). The XRD result shows nano-Ag/HA is a hybrid composite of hydroxyapatite and face-centered cubic crystalline silver. The TEM result confirms the size and distribution of nano-Ag are dependent on the mass ratio of deposited nano-Ag and nano-HA, decreasing the mass ratio can obtain nano-Ag with smaller size and less particle aggregation, which can be contributed to the heterogeneous nucleation effect of nano-HA on nano-Ag. Silver/hydroxyapatite/alginate composite dressing was fabricated by spraying nano-Ag/HA onto the surface of the alginate dressing. The test result of disc diffusion method shows the evident antimicrobial activity against Escherichia coli (E. coli) is assigned to nano-Ag/HA, no significant difference can be found between the dressings with 0.01g and 0.02g nano-Ag.

Abstract: As a simple and useful approach, vapor-phase photografting acrylic acid was used to modify the surface of PET films. Catalyst of silver nanoparticles was distributed on the photografting PET films equably after reducing by ascorbic acid. Topography of the pristine, grafting and metallized PET films was characterized by scanning electron microscope (SEM). XRD and FTIR-ATR were also used to analyze the electroless plating copper layer and the grafting PET film respectively.

Abstract: A new modified organo-bentonite using dithizone(D-O-bentonite) was used for preconcentration, separation and determination of silver(I) in natural water by flame atomic absorption spectrometry (FAAS). The experimental conditions for effective adsorption and elution of trace levels of silver (I) were optimized with respect to different experimental parameters. The influences of some common coexisting ions were also examined. The results show that the silver ion could be adsorbed on the D-O-bentonite. The adsorbed quantitively was affected by the pH value of medium and contact time. In the medium of pH 4-8, the contact time was 15 min, and capacity of the sorbent was 19.7 mg·g^-1. The silver(I) adsorbed on the sorbent could be completely eluated by using 1 mol·L^-1 HNO₃. The preconcentration factor is 100. The detection limit of the method for silver was 0.02 µg·L^-1. The method was applied to the pre-concentration/separation of silver in the environmental water with satisfactory results.

Abstract: By using electrospinning method, polyamide 6 (PA 6) nanofibers containing 1 wt% of AgNo₃ were spun from different concentrations solutions (15-25 wt%) for use as composite filter media. The silver ions in PA 6 nanofibers were reduced by ascorbic acid solution to silver particles offering antibacterial properties to the final filter after electrospinning. The results show, fibers with mean diameters less than 160 nm were prepared for use as filter media by electrospinning. The diameter of electrospun fiber was proportioned to the viscosity of PA 6 solution but was inversed to the applied electrical voltage. The viscosities of PA 6 solution were decreased by adding of AgNo₃ from which brought more irregular formation of electrospun fibers. The filtration efficiency of spunbond nonwoven would improve greatly by compositing the electrospun PA6 web with or without silver.

Abstract: Electrohydrodynamic printing of silver ink is demonstrated under an applied pulse voltage. Intermittent cone jets are deposited to form uniform dots with a regular spacing on glass slides while conductive patterns with continual tracks are derived from overlapping dots. After sintering at 250°C for 20 min, the patterns have a lower resistivity of 3.07×10^-8 Ω•m such that a practical application is available in microelectronic devices.