In Situ Growing Double-Layer TiO₂ Nanorod Arrays on New-Type FTO Electrodes for Low-Concentration NH₃ Detection at Room Temperature

A novel double-layer TiO2 nanorod array (NRA) gas sensor for room-temperature detection of NH3 was fabricated by employing etched fluorine-doped tin dioxide (FTO) glass as the in situ growing substrate and the new-type gas-sensing electrode via the facile droplet-coating and hydrothermal methods. Due to the synergistic effect of forces, special double-layer TiO2 NRAs with a cross-linked and bridgelike structure is formed, in which adequate point junctions can be generated to construct self-assembled electron pathways required for gas-sensing tests. Gas sensing tests indicate that all samples obtained at different growth times have an excellent gas-sensing response to low-concentration NH3 at room temperature. Among them, the TiO2 NRAs obtained at 6 h (S2) exhibit the highest gas-sensing response to 100 ppm NH3 with a value of 102%. In addition, the growth mechanism, the gas reaction mechanism, and the effect of humidity on the gas sensing performance are also discussed in the present paper.