Silver nanocomposites

The oldest and still intensely used biocidal materials release silver ions. Variations in the design of such materials is still the subject of the majority of publications on antimicrobial coatings. The designs cover sparingly soluble silver salts [87], silver nanoparticles [88], silver nanocomposites [89], and elemental silver coatings [32], The release of the silver ions and of other biocides is controlled by the encapsulating matrix, the solubility of the compound, and the material/medium equilibrium constant. 

Fig. 6 Cryo-TEM images of the silver nanocomposite particles prepared using PS-PNIPA particles with different crosslinker content (a) KPSl-Ag (2.5 mol% BIS), (b) KPS2-Ag (5mol% BIS), and (c) KPS3-Ag (10mol% BIS), (d) Influence of degree of crosslinking on the morphology of silver composite particles [60]...

Sun, N., Wang, Y., Song, Y., Guo, Z., Dai, L., Zhu, D. Novel [60]fullerene-silver nanocomposite with large optical limiting effect. Chem. Phys. Lett. 344, 277-282 (2001)... 

PP/silver nanocomposite fibres were prepared with the aim of achieving permanent antibacterial activity in a common synthetic textile. The fibres were melt-spun by coextmsion of PP and PP/silver masteibatches using general conjugate spinning. Masteibatches were made up of a mixture of PP chips and nano-sized silver powder. The antibacterial efficacy of spun fibres was high when the masteibatch was used as the sheath rather than the core. The antibacterial activity of nano-silver in fibres was evaluated after a certain contact time and calculated by percent reduction of two types of bacteria. Staphylococcus aureus and Klebsiela pneumoniae. DSC and wide-angle X-ray diffraction were used for analysis of stractuie, thermal properties and crystallisation behaviour of the spun fibres. SEM was carried out in order to observe particle distribution on the nanocomposite fibres. 17 refs. (2nd International Conference on Polymer Fibres, Manchester, UK, July 2002)... 

Figure 9.9. Colors of a drawn poly(ethylene)-gold and a poly(ethylene)-silver nanocomposite in polarized light with the polarization plane of the incident light and the drawing direction of the nanocomposite parallel (cp = 0°) and perpendicular (cp = 0°), respectively. See color insert.

Figure 9.10. Transmission electron micrograph of a section of a drawn poly (ethylene)-silver nanocomposite showing uniaxially oriented arrays of silver particles. The doble arrow in the left upper corner indicates the drawing direction.

Figure 9.13. A twisted-nematic iiquid crystal display (LCD) equipped with a poly(ethylene)-silver nanocomposite that had been annealed at 180°C for 15 hr and subsequently drawn as described in the text. The drawing axis of the nanocomposite is oriented paraiiei to the poiarizer in the left image and perpendicular in the right image. See coior insert.

In this study [46], poljwinyl alcohol (PVA)/polyaniline (PANI)/silver nanocomposites were tested for antibacterial activity against Escherichia coli and Staphylococcus aureus. The nanocomposite samples resulted in ZOI with diameters of the 7, 8,12, 9 and 8 mm and 10,12,15,9 and 8 mm against Escherichia coli and Staphylococcus aureus, respectively. It was observed that the PVA/PANI composite, which was used as a control matrix, exhibited no antibacterial activity when compared with PVA/ PANI/silver nanocomposites. 

Antimicrobial CS-silver nanocomposites are also potentially new and exciting antimicrobial agents against varions pathogens. CS-silver nanocomposites, either in the form of silver NP or as ionic dendritic strnctures (Ag ) can be easily synthesised by a simple and environmentally friendly in situ chemical reduction process and could be efficient antimicrobial agents. Below specific critical concentrations, the collective action of silver NP and Ag " ions facilitate enhanced and synergistic antibacterial activity. 

Zhu, Y, Qian, Y., Huang, H., Zhang, M., Liu, S. 1996. Sol-gel y-radiation synthesis of titania-silver nanocomposites. Materials Letters 28 259-261. 

R. A. de Barros and W. M. de Azevedo, Polyanihne/silver nanocomposite preparation under extreme or non-classical conditions, Synth. Met., 158, 922-926 (2008). 

Z. Zhou, D. He, Y. Guo, Z. Cui, M. Wang, G. Li, and R. Yang, Fabrication of polyaniUne-silver nanocomposites by chronopotentiometry in different ionic liquid microemulsion systems, Thin Solid Films, 517, 6767-6771 (2009). 

H. H. Zhou, X. H. Ning, S. L. Li, J. H. Chen, and Y. F. Kuang, Synthesis of polyaniline-silver nanocomposite film by unsymmetrical square wave current method. Thin Solid Films, 510, 164-168 (2006). 

Y.C. Liu, H. Lee, and S.J. Yang, Strategy for the synthesis of isolated fine silver nanoparticles and polypyrrole/silver nanocomposites on gold substrates, Electrochim. Acta, 51, 3441-3445 (2006). 

E. Pinter, R. Patakfalvi, T. Fiilei, Z. Gingl, I. Dekany, and C. Visy, Characterization of polypyrrole-silver nanocomposites prepared in the presence of different dopants, J. Phys. Chem. B, 109, 17474-17478 (2005). 

A. Choudhury, Polyaniline/silver nanocomposites Dielectric properties and ethanol vapour sensitivity. Sens. Actual. B, 138, 318-325 (2009). 

Dirix, Y., Bastiaansen, C., Caseri, W., and Smith, R, Preparation, structure and properties of uniaxiaUy oriented polyethylene-silver nanocomposites, J. Mater ScL, 34, 3859-3866 (1999b). 

The complex formed of silver ions and acrylonitrile monomers provides an excellent precursor for the synthesis of polymer/ silver nanocomposite [Wen-Fu and Kai-Tai, 2010 Carotenuto et al., 2005]. When this solution is irradiated with UV, the acrylonitrile polymerized simultaneously Ag gel reduced Ag° [Zhongping et al., 2001]. 

The crystallinity of hydrogel/silver nanocomposite could be established by diffraction studies. The formation of silver nanoparticle confirm by International Centre of Diffraction Data, ICDD, library of silver. The diffraction peaks for hydrogel/silver nanocomposites found at 26 value of 38.1°, 44.26°, 64.50°, and 77.42° are attributed due to (111], (200], (220], and (311] planes of FCC, respectively (Bajpai et al., 2013 Daniel et al., 1996 Murali Mohan et al., 2010]. Pure hydrogel failed to show any peak in the XRD indicating its amorphous nature. In order to check whether the silver nanoparticles were oxidized to silver oxide, the XRD pattern of composite after storing it for three months was compared with original one. If it has the same pattern as that of fresh hydrogel/silver nanocomposite, this indicates its stability at ambient condition. 

Thomas, V., Mural Mohan, Y., Sreedhar, B., Bajpai, S. K. (2007). A versatile strategy to fabricate hydrogel-silver nanocomposites and investigation of their antimicrobial activity. I. Colloid Interface Sci.. 315, 389-395. 

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