Fabrication and characterization of VOC sensors based on suspended zinc oxide nanorods functionalized by cobalt porphyrin

We report volatile organic compound (VOC) sensors based on suspended zinc oxide nanorods (ZnONRs) functionalized by cobalt porphyrin (CoPP) as sensing material. The ZnONRs are synthesized between two facing micro-bridges to form a two-terminal device. The ZnONRs are designed to be suspended well above the substrate for better exposure to and adsorption of VOC molecules to enhance sensitivity. Both of the two bridges serve as micro-heaters to increase the temperature of ZnONRs. Few studies have investigated the use of micro-heaters to heat these suspended nanostructures for gas sensing. In order to further improve the sensitivity, ZnONRs are functionalized by coating CoPP that excellently adsorbs VOC. The fabricated sensor successfully detected 8 ppb of toluene, one of representative VOCs. Benzene and xylene of 40 ppb were also able to be measured by the fabricated sensor.