Bactericidal properties of ZnO-Al(2)O (3) composites formed from layered double hydroxide precursors.

ZnO-Al(2)O(3) composites with different Zn/Al molar ratios (R) have been prepared using zinc-aluminium layered double hydroxides (LDHs) Zn( R )Al-CO(3) 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-Al(2)O(3) 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-Al(2)O(3) 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-Al(2)O(3) has also been investigated. It is suggested that highly active O(2) (-) and *OH species generated on the surface of ZnO-Al(2)O(3) particles react with the peptide linkages in the cell walls of bacteria or spores resulting in their destruction.