Photoactivated solid-state gas sensor for carbon dioxide detection at room temperature

A photoactivated room temperature BaTiO3–CuO thin film for carbon dioxide detection is presented. The response time to carbon dioxide is around 2 min and the sensitivity shows a logarithmic relation between 500 and 5000 ppm of CO2. The electrical changes are related to the physical behavior of the photoactivated material according to the p–n heterojunction formed between the BaTiO3 and the CuO. The chemical reaction that allows the sensing process is based on the interaction of the CO2 and the hydroxyl groupʹs (OH−) adsorbed on the p–n heterojunction. The impedance variations measured are related to the charge migration from the surface to the bulk of the material. The photochemical stimulation allows the possibility of sensing at room temperature (25 ± 1 °C).