Identification and quantification of ionic silver from colloidal silver prepared by electric spark discharge system and its antimicrobial potency study

The study of nanoparticles has become a target of major interest in science. Metallic silver nanoparticles (Ag-0) and ionic silver (Ag+) are the future of the post-antibiotic era, with the latter playing perhaps the central role in this fight. Traditional chemical synthesis methods for colloidal silver (CS) may lead to the presence of toxic chemical species or chemical residues, which may inhibit the effective authentication of CS as an antibacterial agent. To counter these problems a good alternative method-electric spark discharge system (ESDS) was used to fabricate a silver nanoparticles suspension in deionized water with no added chemical additives. Most related research in this field is confined to exploring the composition of nanoparticle, ignoring ions. However, we aim to identify and quantify the proportion of ionic silver in ESDS-CS. The results reveal that ESDS-CS contains both metallic silver nanoparticles and ionic silver. Furthermore, the antimicrobial affect of ESDS-CS on Staphylococcus aureus was also studied. The experimental data suggest that CS solutions with an ionic silver concentration of 30 ppm or higher are strong enough to eliminate S. aureus. In addition, it was found that a solution's antimicrobial potency is directly related to its level of silver ion concentration. (C) 2008 Elsevier B.V. All rights reserved.