We report highly active visible-light driven nitrogen-doped three-dimensional polycrystalline anatase TiO2 photocatalysts (N-3 D TiO2) for environmental and biomedical applications. N-3DTiO(2) is synthesized at a low temperature (<90 degrees C) without thermal treatment via a modified hydrothermal process (HP) and ultrasound irradiation (UI). The N-3D TiO2 is additionally irradiated with visible-light to improve the hydroxylation of its surface. Under visible-light irradiation, the photocatalytic activity of visible-light irradiated N-3DTiO(2) (*N-3DTiO(2); [k] = 1.435 h(-1)) is 26.1 times higher than that of 3DTiO(2) ([k] = 0.055 h(-1)). The N-3DTiO(2) is highly recyclable and retained 91.8% of the initial decolorization rate after fifteen cycles. Interestingly, the *N-3D TiO2 shows very strong antibacterial properties against both Gram-negative Escherichia coil (E. coil) and Gram-positive Staphylococcus aureus (S. aureus) after exposure to visible-light for 3 h. The antibacterial properties of *N-3D TiO2 are more effective than those of TiO2, 3D TiO2, and N-3D TiO2. More than 91.3% of the E. coli is sterilized after ten cycles. There are a large increase in the photocatalytic and antibacterial activity of *N-3D TiO2 relative to that of N-3D TiO2 owing to the hydroxylation of the N-3D TiO2 surface as a result of the visible-light irradiation. These results indicate that *N-3D TiO2 might have utility in several promising applications such as highly efficient water/air treatment, inactivation of pathogenic microorganisms, and solar-energy conversion. (C) 2013 Elsevier B.V. All rights reserved.