Polycrystalline hollow MOF derived Co3O4 semiconductor to achieve room-temperature ammonia detection in human exhaled breath

Functional gas-sensing devices, on their portable and non-invasive merits, have stimulated a new exploring in clinical detection of gaseous biomarkers for critical diseases such as hepatopathy and nephropathy. Metal oxide semiconductor (MOS) sensors owing to their high sensitivity and facile manufacture appears to be the most promising for integration into illness surveillance devices. However, the high operating temperature of MOS poses great challenge for their realistic application. Herein, MOF-derived Co3O4 sensor series are prepared by facile manipulation of the morphological structure and crystalline state of their maternal ZIF-67. It shows that polycrystalline hollow ZIF-67 (PH-ZIF-67) derived PH-Co3O4 exhibits the optimum response and selectivity to trace NH3 at room-temperature sensing. PH-Co3O4 has a low limit of detection and well moisture resistance, which further behaves a significant quantitative response to actual exhaled breath of patients with hepatic encephalopathy. Furthermore, the scientific link between performance enhancement and structural adjustment is revealed by XPS, EPR, etc. It is found that the construction of the polycrystalline structure increases the oxygen vacancies generated during calcination, and additionally, the hollow structure provides more chemisorbed oxygen on the extra inner surface, which coupled to enhance the number of reactive oxygen sites responsible for the response improvement.