Nickel-oxide-based films exhibiting antibacterial activity against both Gram-negative (Escherichia coli) and Gram-positive bacteria (Bacillus atrophaeus) have been fabricated by electrodeposition from aqueous solutions. However, after annealing of the films, no antibacterial activity has been observed. As-deposited films were found to consist of a mixture of nickel-oxide hydroxide and nickel hydroxide, while annealing resulted in the conversion of the films into pure NiO. Also, annealed films exhibited no production of H(2)O(2), unlike as-deposited films. Thus, antibacterial activity of as-deposited films is related to the presence of nickel-oxide hydroxide/nickel hydroxide which results in the production of reactive oxygen species and antibacterial activity. (C) 2009 Elsevier B.V. All rights reserved.