Silica-silver core-shell particles for antibacterial textile application.

The silica-silver core-shell particles were synthesized by simple one pot chemical method and were employed on the cotton fabric as an antibacterial agent. Extremely small (1-2 nm) silver nanoparticles were attached on silica core particles of average 270 nm size. The optimum density of the nano silver particles was found which was sufficient to show good antibacterial activity as well as the suppression in their surface plasmon resonance responsible for the colour of the core-shell particle for antibacterial textile application. The change in the density and size of the particles in the shell were monitored and confirmed by direct evidence of their transmission electron micrographs and by studying surface plasmon resonance characteristics. The colony counting method of antibacterial activity testing showed excellent results and even the least silver containing core-shell particles showed 100% activity against bacterial concentration of 10(4) colony counting units (cfu). The bonding between core-shell particles and cotton fabric was examined by X-ray photoelectron spectroscopy. The antibacterial activity test confirmed the firm attachment of core-shell particles to the cotton fabric as a result 10 times washed sample was as good antibacterial as that of unwashed sample. The bacterial growth was inhibited on and beneath the coated fabric, at the same time no zone of inhibition which occurs due to the migration of silver ions into the medium was observed indicating immobilization of silver nanoparticles on silica and core-shell particles on fabric by strong bonding.