Applicability and antibacterial activity of polycyclic aromatic compound derivatives used as photocatalysts for water oxidation

Water is oxidized using 5,8-dicyano[5]phenacene, a thin-film catalyst supported on a silica plate by vacuum deposition; hydrogen peroxide is produced under visible-light irradiation. Despite the high hydrogen peroxide production rate during the initial reaction stage, the rate decreases after 12 h, and the reaction is almost terminated after 24 h, possibly because hydrogen peroxide undergoes self-decomposition. The self-decomposition rate of hydrogen peroxide increases with increasing concentration, and attains equilibrium. Additionally, Escherichia coli is efficiently sterilized using this catalyst under visible-light; the antibacterial effect is exhibited even under indoor light. Among several polycyclic aromatic derivatives, 9,10-dicyanoanthracene exhibits the highest hydrogen peroxide production rate and antibacterial activity against E. coli. Its antibacterial efficiency is approximately 16 times higher than that of 5,8-dicyano[5]phenacene. The oxygen species causing these antibacterial effects is investigated using trapping reagents. superoxide anion radicals and hydroxyl radicals induce antibacterial effects; hydroxyl radicals are particularly effective.