Iodine-modified　TiO2　nanocrystallites　(denoted　as　I-TiO2)　were　synthesized　by　a　combination　of　sal-gel　process　(TiO2　sol)　and　solvothermal　method　in　the　presence　of　HI　solution.　Their　photocatalytic　and　anti-bactericidal　activities　were　systematically　investigated　under　visible　light　irradiation.　The　results　showed　that　the　iodine　modifier　existed　in　the　form　of　I-2　is　responsible　for　the　visible　light　response.　Moreover,　the　I-2　significantly　enhanced　the　antibacterial　activity　under　visible　light　and　was　stable　during　the　photocatalytic　process.　In　addition,　an　interesting　post-illumination　catalytic　memory　of　I-TiO2　that　continues　to　inhibit　the　growth　of　Escherichia　colt　in　dark　was　also　observed　after　the　visible　light　was　shut　off.　(C)　2015　Elsevier　B.V.　All　rights　reserved.