Highly reduced TiO2-δ nanotube arrays with enhanced visible-light absorption and room-temperature ferromagnetism

Abstract The introduction of oxygen vacancies ( V o ) in various oxide nanostructures has been extensively used to modify their physical and chemical properties. Here, we report on a N 2 -flow-annealing method for introduction of V o in titania (TiO 2 ) nanotube arrays prepared by potentiostatic anodization of Ti plates. The investigation of their V o -related optical and ferromagnetic properties shows that the arrays annealed in a strong N 2 flow exhibit stronger visible-NIR absorption and room-temperature ferromagnetism than the ones annealed in sealed N 2 . The two enhanced properties may stem from the introduction of a high concentration of V o , whose formation is facilitated by a strong N 2 flow field over the nanotube arrays.