Antibacterial Characterization of Silver Nanoparticles against E. Coli ATCC-15224

Silver nanoparticles of mean size 16 nm were synthesized by inert gas condensation （IGC） method. Crystalline structure, morphology and nanoparticles size estimation were conducted by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. Antibacterial activity of these silver nanoparticles as a function of particles concentration against gram-negative bacterium Escherichia coli （E. coli） was carried out in liquid as well as solid growth media. Scanning electron microscopy （SEM） and TEM studies showed that silver nanoparticles after interaction with E.coli have adhered to and penetrated into the bacterial cells. Antibacterial properties of silver nanoparticles are attributed to their total surface area, as a larger surface to volume ratio of nanoparticles provides more efficient means for enhanced antibacterial activity.     

Silver Diffusion and Clustering in Oxyfluoride Glasses Investigated by Molecular Dynamics Simulations

Glasses with compositions (97 – x)[PbF₂:GeO₂]–3Al₂O₃–xAg₂O, with the PbF₂:GeO₂ ratio equals to 1.5 and x varying from 0 to 3%, form silver surface films after thermal treatment near the glass transition temperature. The NPT molecular dynamics simulations of a glass composition 56.4PbF₂–37.6GeO₂–3Al₂O₃–3Ag₂O have been performed, where 0, 20, 40, 60, and 100% of the Ag⁺ ions were reduced to Ag by the fluoride ions. The simulations showed that the silver atoms aggregate into clusters of increasing numbers and sizes as the silver atoms content increases. In addition, the silver atoms diffusion coefficients are at least one order of magnitude larger than the fastest ion in the matrix. These results are consistent with the rapid formation of the metallic surface film observed experimentally.     

Cover Picture: Metallodielectric Two‐Dimensional Photonic Structures Made by Electric‐Field Microstructuring of Nanocomposite Glasses (Adv. Mater. 24/2005)

Nanocomposite glasses containing metallic nanoparticles can be microstructured by electric‐field assisted dissolution of the embedded particles. As reported by Graener and co‐workers on p. 2983, any pattern of the electrode—down to the nanoscale—can be transferred onto the nanocomposite glass, giving 2D metallodielectric microstructures. The cover image shows as the background a regular array of squares with 2 μm periodicity produced using macroporous silicon as an electrode. The insets show the base material, the electrode, a representation of the dissolution process, and an enlarged view of the remaining silver nanoparticles.