Bactericidal properties of ZnO–Al2O3 composites formed from layered double hydroxide precursors

ZnO–Al2O3 composites with different Zn/Al molar ratios (R) have been prepared using zinc–aluminium layered double hydroxides (LDHs) ZnRAl–CO3 as precursor. The samples were characterized by XRD, ICP, EDX, EPR and FT-IR. The results show that ZnO is highly dispersed in all of the ZnO–Al2O3 composites. Bactericidal experiments against Staphylococcus aureus ATCC 6538 and Bacillus subtilis var. niger ATCC 9372 were carried out by contacting the bacteria and spores with the ZnO–Al2O3 composites. The composites all showed high bactericidal activity against Staphylococcus aureus ATCC 6538, and the bactericidal efficiency against Bacillus subtilis var. niger ATCC 9372 increased with increasing content of ZnO. The mechanism of bactericidal activity of ZnO–Al2O3 has also been investigated. It is suggested that highly active O2− and •OH species generated on the surface of ZnO–Al2O3 particles react with the peptide linkages in the cell walls of bacteria or spores resulting in their destruction.