Highly Sensitive Detection of Benzene, Toluene, and Xylene Based on CoPP-Functionalized TiO₂ Nanoparticles with Low Power Consumption

Among various metal oxides, titanium dioxide (TiO₂) has received considerable interest as a gas-sensing material owing to its high reliability at high operating temperatures. Nonetheless, TiO₂ generally has low sensitivity to target gases. In particular, TiO₂-based sensors have difficulty in sensitively detecting benzene, toluene, and xylene (referred to as BTX). Moreover, the reported TiO₂-based sensors have not simultaneously satisfied the demand for tens of ppb BTX detection and operation with low power consumption. This work proposes a BTX sensor using cobalt porphyrin (CoPP)-functionalized TiO₂ nanoparticles as a sensing material on a suspended microheater fabricated by bulk micromachining for low power consumption. TiO₂ nanoparticles show an enhanced sensitivity (245%) to 10 ppm toluene with CoPP functionalization. The proposed sensor exhibits high sensitivity to BTX at concentrations ranging from 10 ppm down to several ppb. The high reliability of the sensor is also explored through the long-time operation with repeated exposure to 10 ppm toluene for 14 h.