Superior bactericidal activity of SDS capped silver nanoparticles: Synthesis and characterization

Silver nanoparticles were synthesized through UV photo-reduction of silver nitrate aqueous solution, containing ethanol and sodium dodecyl sulfate (SDS) using an UV digester equipped with high pressure mercury lamp of 500 W. The synthesized nanoparticles were characterized by UV–vis spectroscopy (UV–vis), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The formation of silver nanoparticles was confirmed from the appearance of surface plasmon absorption maxima at 418 nm. TEM showed the spherical nanoparticles with size in 23–67 nm (average 45 ± 10 nm). The silver nanoparticles were stable for more than 8 months. The antibacterial activity of these SDS capped silver nanoparticles was tested using Pseudomonas aeruginosa as a model strain for gram-negative bacteria. SDS capped silver nanoparticles exhibit a much higher bactericidal activity compared to silver nanoparticles capped with other capping agents. Even at a low silver nanoparticle concentration of 5 μg/ml, complete inhibition of 10⁷ colony forming units (CFU) was achieved with SDS capped silver nanoparticles. This concentration is much lower than the values reported by other authors. This enhanced bactericidal activity is attributed to much efficient transport of silver nanoparticles by SDS to the outer membrane of cell wall compared to the other capping agents and have a better interaction of nanoparticles with the cell.