A new photocatalyst, namely single-crystalline Bi5O7NO3 nanofibers, was prepared by a facile hydrothermal method in the presence of Triton X-100 and ammonia. Bi5O7NO3 possessing a crystalline sheet morphology could be dissolved and transformed into nanofibers by controlling the reaction time. Samples were characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy. The Bi5O7NO3 nanofiber growth mechanism is discussed in detail. The band gap energy of the as-prepared Bi5O7NO3 photocatalyst was about 2.70-2.90 eV. Results of first-principle density functional theory calculations confirmed that Bi5O7NO3 had a narrow band gap. They revealed that the conduction band bottom was predominantly composed of Bi 6s, Bi 6p, N 2p and O 2p orbitals, while the valence band (VB) top primarily consisted of Bi 6p, Bi 6s and O 2p orbitals. The as-obtained Bi5O7NO3 nanofibers showed good photocatalytic activity and stability for the degradation of Rhodamine B (RhB) under visible light irradiation, which may be ascribed to the highly mobile conduction band (CB) and VB charge carriers. (C) 2010 Elsevier Inc. All rights reserved.