High anti-humidity exhaled acetone sensor based on Co3O4 derived from MOF-74

Acetone in human exhaled breath can be used as a biomarker for the early diagnosis of diabetes, because exhaled gas contains a large amount of water and other volatile organic compounds (VOCs), improving the selectivity is still a great challenge. In this work, 1D Co3O4 derived from MOF-74 with high moisture resistance and low detection limit was synthesized and used for the detection of acetone markers in human exhaled gas. The 1D porous Co3O4 with different average grain sizes were obtained by precise control of the MOF-74 pyrolysis temperature in a range of 300–450 ℃. The static gas sensitivity test results indicate that the MOF-74-derived Co3O4 at a pyrolysis temperature of 300 ℃ showed the highest response to 50 ppm acetone at an optimal operating temperature of 175 ℃. In the presence of four interfering gases including ethanol, methanol, formaldehyde and ammonia, the prepared Co3O4 sensor showed good selectivity to acetone. In addition, the exhalation simulation tests show that the detection limit of Co3O4 sensor for acetone in exhaled gas is as low as 500 ppb. Moreover, as the relative humidity increases, the initial resistance of the Co3O4 sensor increases, but the response value to 1.8 ppm acetone at 175 ℃ is almost unchanged. The good acetone sensing properties in exhaled gas were attributed to the unique structure of MOF-74 after pyrolysis, which prevented the nanoparticle agglomeration from occurring and provided more exposed active sites. Furthermore, the effective catalytic activity of surface Co2+ in the Co3O4 tetrahedral ligand of the cubic spinel structure enhances the sensing performance of acetone. With the advantages of low detection limit and high anti-humidity, gas sensors based on Co3O4 derived from MOF-74 are expected to become a potential candidate for the detection of acetone in exhaled gas of patients with diabetes in clinical non-invasive testing.