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.