Investigation of Antibacterial Properties of Silver Nanoparticles in Flame-Retardant and Standard Expandable Polystyrenes

In this study, we investigated the antibacterial properties of silver nanocomposites in standard and flame-retardant expandable polystyrenes (EPS). To prepare the silver-polystyrene nanocomposite, we solved polymers separately in a solvent before adding nanoparticles into the solution. For both of EPS samples, three different gelatin yellowish solutions of silver nanoparticles in polystyrene were synthesized at 12.5, 25 and 37.5 µg/cm3. TEM and XRD imaging showed that the silver nanoparticles were about 20 nm in diameter. Additionally, SEM imaging was used for the investigation of silver nanoparticles distribution and also morphology of the nanocomposite cross sections. Samples were laid on polymeric nanocomposite disks to study the antimicrobial properties of them in the presence of gram-negative E. coli ATCC 25922 bacteria and gram-positive Staphylococcus aureus ATCC 6538 bacteria through the standardized single disk. Our comparative study showed that flame-retardant expandable polystyrene-silver nanocomposite does not have any antimicrobial property against these bacteria, while standard expandable polystyrene-silver nanoparticle has some antibacterial potential on Staphylococcus aureus ATCC 6538 which was dependent on concentration levels of the silver nanoparticles. Results of this work could be justified based on the roles of silver nanoparticle concentrations, impurities in polystyrenes and structure of the microorganisms. This research may be considered as a base for investigations on antimicrobial properties of polystyrene nanocomposites as well as vast industrial and healthcare applications of them in the future.