Exploiting Free-Standing p-CuO/n-TiO Nanochannels as a Flexible Gas Sensor with High Sensitivity for HS at Room Temperature.

Hydrogen sulfide (HS) is an extremely hazardous gas and is harmful to human health and the environment. Here, we developed a flexible HS gas-sensing device operated at room temperature (25 °C) based on CuO nanoparticles coated with free-standing TiO-nanochannel membranes that were prepared by simple electrochemical anodization. Benefiting from the modulated conductivity of the CuO/TiO p-n heterojunction and a unique nanochannel architecture, the traditional thermal energy was innovatively replaced with UV irradiation (λ = 365 nm) to provide the required energy for triggering the sensing reactions of HS. Importantly, upon exposure to HS, the p-n heterojunction is destroyed and the newly formed ohmic contact forms an antiblocking layer at the interface of CuS and TiO, thus making the sensing device active at room temperature. The resulting CuO/TiO membrane exhibited a notable detection sensitivity for HS featuring a minimum detection limit of 3.0 ppm, a response value of 46.81% against 100 ppm HS gas, and a rapid response and recovery time. This sensing membrane also demonstrated excellent durability, long-term stability, and wide-range response to a concentration of up to 400 ppm in the presence of 40% humidity as well as outstanding flexibility and negligible change in electrical measurements under various mechanical stability tests. This study not only provides a new strategy to design a gas sensor but also paves a universal platform for sensitive gas sensing.