Papers by Keyword: Silver

Abstract: Montmorillonite clay particles were decorated with silver (Ag) nanoparticles by chemical reduction of Ag nitrate with sodium citrate. X-ray diffraction (XRD) and energy dispersive X-ray spectrometry (EDS) confirmed the presence of metallic Ag on the surface of montmorillonite. The average crystallite size of the Ag nanoparticles obtained from the broadening of the 111 Ag peak ranged at 13-16 nm. On the other hand, the apparent particle sizes obtained from the SEM images were about 79-128 nm, suggesting that the nanoparticles are polycrystalline and possibly agglomerated. The increase in the concentration of reducing agent produced smaller Ag nanoparticles with narrower size distribution. The antibacterial test showed that the Ag nanoparticles, with mean size of 79 nm, adsorbed on montmorillonite were able to inhibit the growth of Staphylococcus aureus (S. aureus) with an antimicrobial index of 0.4.

Abstract: Nanoparticles play a fundamental role on nanocomposite properties, as they significantly increase the contact area and allow a homogeneous distribution in comparison to microparticles. Silver nanoparticles (AgNP) have been extensively used in biomedical and engineering applications due to their interesting properties, such as antibacterial activity. Polyethylene terephthalate (PET) is a semi-crystalline polymer and has excellent chemical resistance and thermal stability. Because of its remarkable properties, PET has been used in several industrial applications, such as packaging, electrical, automotive, construction and textile. The aim of this study was to prepare potential antimicrobial PET-AgNP nanocomposite filaments for textile applications. Therefore, AgNP were incorporated in the PET matrix at different concentrations (0.05; 0.10; 0.15; 0.20; 0.25; 0.30; 0.35 and 0.40%) by extruding the PET resin with specific amounts of a 10% (w/w) AgNP/PET master batch. Then, rheological characterization was carried out and filaments were produced for mechanical, optical and thermal analyses. The incorporation of up to 0.20% (w/w) of AgNP in the polymeric matrix has not significantly altered overall properties of PET nanocomposites. Moreover, the nanocomposite incorporated with 0.05% of AgNP demonstrated suitable intrinsic viscosity for fiber processing and PET-like mechanical, thermal and optical properties.

Abstract: Infections after bone implant surgeries have remained one of the leading underlying cause of revision surgery due to implant failure. Despite careful and improved surgery procedures and systemic antibiotic prophylaxis are well practised, the possibility of infection still exists. Many strategies have been studied to prevent post-implant infections, such as anti-bacterial coatings, adhesion resistant coatings, and anti-microbial alloying element. To respond on the challenge of reducing the risks of infections after bone implantations, a review that focused on the effectiveness of anti-bacterial coatings on metallic implants are briefly presented.

Abstract: The deposition using cold gas dynamic spraying of silver-doped hydroxyapatite (HA-Ag) /Titanium (Ti) composite have been fabricated on Al 6061 substrate. The biocompatibility of the obtained HA-Ag/Ti coatings was studied. The ratios of HA-Ag to Ti in their composite powders were 20:80, 50:50 and 80:20 (weight %). The HA-Ag/Ti coatings were successfully deposited using cold spraying parameters of 13-15 bars under helium gas, temperature of between 300-400°C. The biocompatibility results showed that human osteoblast and RAW cells spread and adhered well on the coating surfaces especially at low concentration of HA-Ag contained.

Abstract: In this report, star-shaped silver@gold (Ag@Au) nanoparticles were synthesized in collagen (Coll) suspensions by a seeding growth approach. The silver nanoparticles were used as seeds for Au development. Coll was used as a protecting agent and the effect of its concentration on stability was also examined. Obtained nanoparticles were then characterized by UV-Vis, TEM, XRD and FTIR. The result was confirmed by the maximum surface plasmon resonance peak at 566-580 nm for each sample indicating the formation of branched Ag@Au@Coll NPs. The average diameters of the branched Ag@Au@Coll NPs were revealed to be 30-50 nm depending on the corresponding component ratio and the pH value. It is interesting to note that the concentration of Coll plays a critical role in the stability of the star-shaped gold nanoparticles. The results offer an understanding of the handling of the electronic and the silver@gold based nanoparticles stability properties.

Abstract: The technique of platinum (IV) determination in mineral raw materials with the application of stripping voltammetry has been proposed. The authors determined the registration conditions in the determination of the analytical signal Pt (IV): the composition of background electrolyte, the electrolysis potential. The graphite electrode impregnated with polyethylene was used as a working electrode. The use of stripping voltammetry applied to the assessment of the platinum content in geological objects was demonstrated.

Abstract: Silver nanoparticles (Ag NPs) were synthesized by sparking process. The NPs were continuously deposited onto the substrate by varying the number of sparking cycles ranging from 100-200 and deposited on the glass substrate and annealing at 250-500 °C for 1 hr. The effect of Ag NPs on their structure and optical characteristics were investigated. The optical properties of the NPs have been studied from by Raman spectroscopy and UV-vis spectrophotometer. The morphology of Ag NP was characterized by Scanning Electron Microscope (SEM) and Atomic force microscope (AFM). The results have shown mainly spherical structure of Ag NPs in diameter ranging from 80-100 nm. This study demonstrated that the Ag NPs can be synthesized by sparking process and simply with low cost.

Abstract: Most microorganisms grow on surfaces as biofilms rather than as individual planktonic cells, and cells within biofilms show high levels of resistance against antimicrobial drugs. Thereby biofilm formation complicates treatment and contributes to high morbidity and mortality rates associated with infections. This study explores the physical, optical, and nano-structural properties of silver and copper nanoparticles dispersed in aqueous suspensions (nanoparticulate colloidal water) and examines their in vitro activity against microbial biofilms. Silver and copper nanoparticulate colloidal water of various concentrations were prepared and studied. Their surface energies, surface charge and surface plasmonic resonance properties were determined using contact angle measurement, zeta potential measurement and optical spectrometry, respectively. A model of biofilm formation on the wells of microtiter plates was used to determine the activity of the nanoparticulate suspensions against fungal and bacterial biofilms. Scanning electron microscopy (SEM) was used to observe the nanoparticle interactions with microbial cells within the biofilms. Results show that silver nanoparticle-containing liquids have higher surface energy than their copper counterparts; and that the surface energy increases as the concentration of silver nanoparticles increases. Altogether, the effectiveness of silver nanoparticle colloidal suspensions in controlling biofilm formation is observed and reported. For a given size of silver nanoparticles studied, it is found that the effective concentrations against microbial biofilms are far lower than their cytotoxic concentrations, indicating an overall safety and a good therapeutic index thus substantial application potential.

Abstract: This paper attempts to propose an innovative strategy/model for the recovery of precious metal like silver from e-waste by employing combined technologies. Firstly, silver is leached using free cyanide from electronic scrap thereby forming silver-cyanide complex. In the second step, silver-cyanide is removed using biosorption using passive Eicchornia roots powder biomass. Lastly, the residual silver-cyanide remaining after biosorption is biodegraded using live heterotrophic bacterial consortium. Feasibility study showed that the overall system strategy worked efficiently for the management of e-waste.

Abstract: The system in a package (SiP) including of a system on a chip (SoC) and a double-data-rate-three synchronous dynamic random access memory (DDR3 SDRAM) were studied with respect to the high-speed characteristics. The SiP was the multi-chip-module thin-profile fine-pitch ball grid array (MCM TFBGA) package with four-layer substrate. The high-speed 1600-Mbps data rate DDR3 signals were used in the signal integrity (SI) analysis. The SiP with low-cost silver (Ag) wires displayed a 500.18-ps aperture width in the eye diagram, which was successfully achieved signal integrity (SI) performance requirement. This work demonstrated the SiP with the Ag wires was the great potential solution for the advanced high-speed product applications.