A visible-light-assisted Pd/TiO₂ gas sensor with carbon nanotubes electrodes for trace formaldehyde detection

Owing to the ppb-level detection standard toward the toxic and harmful gas, the detection of trace gases has become an important subject in the field of indoor environment management. However, the traditional resistive gas sensors hardly meet the requirement due to the weak signal generated by trace gas molecules that are difficult to capture. Herein, a visible-light-assisted Pd/TiO2 gas sensor is proposed to endow the effective detection of trace formaldehyde (HCHO) gas without heating temperature. Benefiting from the enhanced photocatalytic properties of TiO2 by Pd decoration, the visible-light-assisted Pd/TiO2 gas sensor can detect the HCHO gas as low as 80 x 10(-9) at room temperature. The successful preparation of nanoscale TiO2 sensing layer is facilitated by the ultra-thin carbon nanotube interdigital electrode in the gas sensor, which avoids the discontinuity of the sensing layer caused by the excessive thickness of the traditional metal electrode. In addition, the whole preparation process of the Pd/TiO2 gas sensor with carbon nanotube electrodes is compatible with mainstream CMOS fabrication technology, which is expected to realize the batch fabrication and micro-integrated application of gas sensors. It is expected that our work can provide a new strategy for the batch preparation of high-performance trace HCHO gas sensors and their future applications in portable electronic devices such as smartphones.