Ultrasmall silver nanoclusters: Highly efficient antibacterial activity and their mechanisms

, respectively. Meanwhile AgNCs demonstrated no apparent antibacterial activity against Gram-positive S. aureus. Then, the antibacterial mechanisms of AgNCs were systematically investigated. We found that AgNCs affected the growth of different E. coli strains in different ways. AgNCs inhibited the growth of E. coli DH 5α mainly through damaging the outer cellular membrane and permeating into the cells, followed by the antibacterial effect of the internalized AgNCs and released silver ions. AgNCs, however, inhibited the growth of E. coli DSM 4230 cells mainly through diffusing into E. coli DSM 4230 cells and damaging their respiratory chain. These results clearly indicated that different bacterial strains (e.g. different E. coli strains) should be taken into consideration in future studies. Our work facilitates further investigation of the design of new antibacterial silver nanomaterials with different sizes.