Hollow hierarchical TiO2-SnO2-TiO2 composite nanofibers with increased active-sites and charge transfer for enhanced acetone sensing performance

The construction of heterojunction composite nanomaterials is one of the most promising methods for obtaining gas sensors with high sensitivity, low detection limit and fast response-recovery behavior. Herein, we successfully synthesized hollow TiO2-SnO2-TiO2 composite nanofibers. The body consists of hollow SnO2 nanofibers, and the inner and outer surfaces are surrounded by mixed phase TiO2 nanoparticles by a simple two-step method. The hollow SnO2 nanofibers were first fabricated by facile electrospinning technique, and then the TiO2 nanoparticles were subsequently grown on the hollow SnO2 nanofibers via the hydrothermal method. When compared with the sensors based on pure hollow SnO2 nanofibers, the 10 wt% hollow TiO2-SnO2-TiO2 hetero-structures sensor had an excellent sensing performance at the low operating temperature of 280°C and the fast response and recovery characteristics at a low concentration (1 ppm). It presented good selectivity and high response toward acetone compared to pure hollow nanofibers. The main reason for the enhanced acetone gas sensing properties and shortens the response-recovery time was attributed to hollow nanosructure and n-n hetero-junction for hollow TiO2-SnO2-TiO2 composite nanofibers. In addition, the acetone adsorption-desorption mechanism of the hetero-nanofibers was discussed.