Visible Light Responsive Pristine Metal Oxide Photocatalyst: Enhancement of Activity by Crystallization under Hydrothermal Treatment AmanoFumiaki YamakataAkira NogamiKohei OsawaMasatoshi OhtaniBunsho 2008 Visible Light Responsive Pristine Metal Oxide Photocatalyst: Enhancement of Activity by Crystallization under Hydrothermal Treatment