Ag nanoparticles decorated TiO2 nanotube arrays for ultrasensitive gas sensing

Anodic TiO2 nanotube arrays have attracted extensive interests in the past decade, especially for monitoring or sensing of the gas. In this paper, an ameliorated two-step anodization process was adopted for the preparation of highly ordered and vertically aligned TiO2 nanotube arrays on the Ti metal substrate. The as-prepared TiO2 nanotube arrays were successfully decorated with uniformly distributed Ag nanoparticles through a wetting-ultraviolet radiation deoxidation technology using the AgNO3 solution as precursor and source for Ag element. Field-emission scanning electron microscope (FESEM) was employed for the structural and morphological characterization of the Ag nanoparticles decorated TiO2 nanotube arrays. Then the as-prepared TiO2 nanotube arrays and Ag-decorated TiO2 nanotube arrays were both evaluated for room temperature ethanol gas sensing and the results showed that the Ag-decorated TiO2 nanotube arrays exhibited much higher sensitivity, as well as the reponse speed and recovery rate, than the pure TiO2 nanotube arrays. This phenomenon indicated that the well dispersed Ag nanoparticles onto the TiO2 nanotube arrays could effectively optimize their gas sensing properties. The mechanism of the improvement of gas sensitivity was also discussed in this paper.