Ethanol-sensing properties of cobalt porphyrin-functionalized titanium dioxide nanoparticles as chemiresistive materials that are integrated into a low power microheater

Gaseous ethanol detection has attracted significant interest owing to its practical applications such as in breath analysis, chemical process monitoring, and safety evaluations of food packaging. In this study, titanium dioxide (TiO₂) nanoparticles functionalized with cobalt porphyrin (CoPP) are utilized as resistive ethanol-sensing materials, and are integrated with a suspended micro-heater for low power consumption. The micro-heater with the suspended structure inhibits substrate heat transfer, resulting in power consumption as low as 18 mW when the operating temperature is approximately 300 °C. CoPP functionalization allows an enhanced response (197.8%) to 10 ppm ethanol compared to that of pristine TiO₂ nanoparticles. It is confirmed that the sensor response is reliable upon exposure to 10 ppm ethanol for three cycles. In addition, responses of different magnitude are obtained under exposure to ethanol at various concentrations from 9 to 1 ppm, indicating that the resistance change originates from a charge transfer between the sensing materials and target gas. The sensing mechanism of CoPP-functionalized TiO₂ in relation to charge transfer is analyzed, and the performance of the proposed sensor with previously reported TiO₂-based ethanol sensors is compared. Considering that it is processed by batch fabrication, consumes low power, and offers high sensitivity, the proposed sensor is promising for use as a portable sensor in the distributed monitoring of gaseous ethanol.