D.P. Papadopoulos

The Effect of Silver Nanoparticles Size, Produced Using Plant Extract from Arbutus unedo, on Their Antibacterial Efficacy

Silver nanoparticles (AgNPs) have been demonstrated to restrain bacterial growth, while maintaining minimal risk in development of bacterial resistance and human cell toxicity that conventional silver compounds exhibit. Several physical and chemical methods have been reported to synthesize AgNPs. However, these methods are expensive and involve heavy chemical reduction agents. An alternative approach to produce AgNPs in a cost-effective and environmentally friendly way employs a biological pathway using various plant extracts to reduce metal ions. The size control issue, and the stability of nanoparticles, remain some of the latest challenges in such methods. In this study, we used two different concentrations of fresh leaf extract of the plant Arbutus unedo (LEA) as a reducing and stabilizing agent to produce two size variations of AgNPs. UV-Vis spectroscopy, Dynamic Light Scattering, Transmission Electron Microscopy, and zeta potential were applied for the characterization of AgNPs. Both AgNP variations were evaluated for their antibacterial efficacy against the gram-negative species Escherichia coli and Pseudomonas aeruginosa, as well as the gram-positive species Bacillus subtilis and Staphylococcus epidermidis. Although significant differences have been achieved in the nanoparticles’ size by varying the plant extract concentration during synthesis, the antibacterial effect was almost the same.

Fabrication Methods and Properties of Open and Closed Cell Foams

In this paper we present some simple methods for the fabrication of closed and open cell Al metal foams. The closed cell Al metal foams were fabricated using liquid metallurgy. Their microstructure and morphological characteristics were studied using optical and electron microscopy techniques. The mechanical properties and their relationship to microstructure were established. A three dimensional model was developed relating the cell geometry to the mechanical behavior of Al closed cell foam material. The open cell Al foams were fabricated using sodium chloride powder sinters and liquid Al metal infiltration techniques. The potential of using these cellular structures in various systems is discussed.