Influence of electronic and structural defects on In2O3-based sensors decorated with noble metals for detection of microbial volatile organic compounds

Abstract

The aim of this proposal is to test In2O3-based sensors derived from metal-organic frameworks (MOFs) through deposition with noble metals (Ag or Pt) for the detection of microbial volatile molecules. The addition of Ag induces electron transfer with In2O3 by changing the oxidation state of the metal. On the other hand, Pt acts in the activation and spill-over of analyte gases, causing changes in the concentration of ionosorbed oxygen on the material's surface. Therefore, the proposal will evaluate the effectiveness of sensors decorated with noble metals compared to the pure In2O3 structure, aiming to improve selectivity, sensitivity, response time, and operating temperature in the detection of mVOCs. The detection of mVOCs is crucial for applications such as disease diagnosis and food spoilage control. Moreover, the study of electronic defects through the existence of oxygen vacancies is fundamental to understanding the effects on the sensor. These electronic defects (oxygen vacancies) will be investigated by EPR, XPS, and complemented by DFT through the proposed BEPE project. The sensors will be prepared by controlled thermal degradation of MOFs previously synthesized by microwave-assisted solvothermal method and ultrasonic spray. The sensor responses will be examined at different concentrations of mVOCs in the range of parts per million (ppm), such as 1-pentanol, 3-methyl-1-butanol, 2-nonanone, 2-butanone, and ethyl acetate, in an environment with controlled relative humidity ranging from 30 to 85% and operating temperatures (150 to 400 °C). The sensors will be characterized post-mortem to correlate their deactivation with possible structural changes. It is expected that noble metal deposition will contribute to better sensor performance, with lower operating temperature and lower detection limit.