Preliminary mechanistic insights into the detection of ethanol vapour using MnO₂ NRs-CNPs-poly-4-(vinylpyridine) based solid-state sensor operating at room temperature

Semiconductor metal oxide gas sensors are widely used to detect ethanol vapours, commonly used in industrial productions, road safety detection, and solvent production; however, they operate at extremely high temperatures. In this work, we present manganese dioxide nanorods (MnO₂ NRs) prepared via hydrothermal synthetic route, carbon soot (CNPs) prepared via pyrolysis of lighthouse candle, and poly-4-vinylpyridine (P4VP) composite for the detection of ethanol vapour at room temperature. MnO₂, CNPs, P4VP, and MnO₂ NRs-CNPs-P4VP composite were characterised using scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Five sensors were prepared, namely, sensor 1 (MnO_2-NRs), sensor 2 (CNPs), sensor 3 (CNPs-P4VP composite of a mass ratio of 1:3), sensor 4 (MnO₂ NRs-CNPs-P4VP composite of a mass ratio 1:1:3), and sensor 5 (MnO₂ NRs-CNPs-P4VP composite of a mass ratio 2:1:3). All the five sensors were used detect to 2-propanol, acetone, ethanol, methanol, and mesitylene vapours at room temperature, but among all the tested sensors, sensor 4 was highly sensitive to ethanol vapour and less sensitive to 2-propanol, methanol, acetone, and mesitylene vapours. The response and recovery time of sensor 4 towards ethanol vapour at 20.4 ppm were 82 seconds and 74 seconds, respectively. The limit of detection on ethanol vapour using sensor 4 was 789 ppb. During detection, the ethanol vapour undergoes total deep oxidation on the surface of sensor 4.