ポルフィリン型有機光触媒による可視光殺菌  [in Japanese] Visible-light Assisted Sterilization by Porphyrin-type Organic Photocatalysts  [in Japanese]

A silica gel-supported dihydroxo(tetraphenylporphyrinato)antimony(V) (Sbtpp/SiO_2) could induce remarkable photocatalytic activity for bactericidal reaction of E. coli cells under fluorescent light irradiation. Also the Sbtpp/SiO_2 photocatalyst showed much superior bactericidal activity to the commercially available TiO_2 under irradiation by sunlight. Moreover, visible-light irradiation of the Sbtpp/SiO_2 catalyst was effective for sterilization of Legionella species in the living environment. Under the operation of a cylindrical photocatalytic bactericidal apparatus in a cooling tower for 10 days, the concentrations of Legionella species were reduced to less than the detection limit. Also, a photocatalytic sterilization was conducted with a fountain. The concentrations of Legionella species were reduced to less than the detection limit 12 days after the Sbtpp/SiO_2 catalyst was installed in the fountain receiving sunlight irradiation. The concentrations of Legionella species were kept at less than an environmental quality standard for three months. Dimethoxo(tetraphenylporphyrinato)phosphorus immobilized on silica gel (Ptpp/SiO_2) was examined for the sterilization of E. coli. It was found that the bactericidal reaction obeyed zero-order kinetics by analysis according to Michaelis-Menten's equation. Adsorption of bacteria on the catalyst is thought to be a key pathway. The Ptpp/SiO_2 which was treated with tetraethoxysilane was applied to the sterilization of Legionella species occurring in fountain. Thus the sterilization was able to be performed under the visible light irradiation. Silica gel is most suitable for visible light-driven catalyst support because silica gel is transmitted visible light effectively and immobilize porphyrin chromophores. Sbtpp and Ptpp had high affinity with microorganisms owing to their cationic complexes. The bactericidal effect was mainly attributed to singlet oxygen (O^^1_2) which was generated by energy transfer from the excited triplet state of the porphyrins to O_2.