Efficient Heterostructures of Ag@CuO/BaTiO for Low-Temperature CO Gas Detection: Assessing the Role of Nanointerfaces during Sensing by Operando DRIFTS Technique.

Tetragonal BaTiO spheroids synthesized by a facile hydrothermal route using Tween 80 were observed to be polydispersed with a diameter in the range of ∼15-75 nm. Thereon, BaTiO spheroids were decorated with different percentages of Ag@CuO by wet impregnation, and their affinity toward carbon dioxide (CO) gas when employed as sensitive layers in a microsensor was investigated. The results revealed that the metal nanocomposite-based sensor had an exceptional stability and sensitivity toward CO gas (6-fold higher response), with appreciable response and recovery times (<10 s) and higher repeatability (98%) and accuracy (96%) at a low operating temperature of 120 °C, compared to those of pure BaTiO and CuO. Such improved gas-sensing performances even at a very low concentration (∼700 ppm) is attributable to both the chemical and electrical contributions of Ag@CuO forming intermittent nanointerfaces with BaTiO spheroids, exhibiting unique structural stability. The CO-sensing mechanism of CuO/BaTiO nanocomposite was studied by the diffuse reflectance infrared Fourier transform spectroscopy technique that established the reaction of CO with BaO and CuO to form the respective carbonate species that is correlated with the change in material resistance consequently monitored as sensor response.