Preparation of silver nanoparticles of enhanced antibacterial effect with benzalkonium bromide

In the study, a colloidal silver nanoparticles stabilized by a bactericide benzalkonium bromide was prepared by borohydride reduction of silver nitrate in water. A dosage of benzalkonium bromide could greatly influence the stability, the size and the dispersity of the prepared silver nanoparticles. When the concentration of benzalkonium bromide was 1x10(-5)g.mL(-1), most of the silver nanoparticles could be coagulated and the solution had no obvious absorption in UV-vis spectra. When the concentration of benzalkonium bromide reached 10x10(-5)g.mL(-1), a stable dispersion of silver nanoparticles without evident precipitation could be obtained. The results of dynamic light scattering (DLS) and transmission electron microscopy (TEM) showed that the average size of the nanoparticles was about 26 nm. Antibacterial tests proved that the silver nanoparticles capped with benzalkonium bromide exhibited a notable antibacterial effect against both Gram-positive and Gram-negative bacteria. The antibacterial effect of the material against Escherichia coli was four times higher than benzalkonium bromide and two times higher than only with the silver nanoparticles. Silver nanoparticles capped with benzalkonium bromide is a potential bactericide for different applications.