ZnO/NiO-type heterostructures derived from metal-organic frameworks for the detection of microbial volatile organic compounds

Abstract

The motivation for this research is the detection of specific volatile organic compounds produced by microorganisms responsible for diseases and food quality. However, there are not many studies in the literature dealing with the rapid detection and low detection limit of these volatile organic compounds produced by microorganisms (microbial volatile organic compounds, mVOCs). The proposal is to evaluate NiO, a p-type semiconductor oxide, in the role of sensor material in heterostructures derived from metal-organic frameworks (MOF). In addition, the effect of n-p junctions will be studied in order to optimize the sensitivity, selectivity and detection time of mVOCs. The semiconducting metal oxides (SMOs) used in the heterostructures are NiO (p-type) and ZnO (n-type). The nanostructured sensors will be prepared from the thermal decomposition in a controlled atmosphere of the MOFs previously prepared by ultrasonic spray combined with the microwave-assisted solvothermal method. The responses of the sensors will be evaluated in different concentration ranges (in ppm) of the mVOCs in dry conditions and in controlled humidity. It is expected that the MOFs will increase the surface area and porosity of the heterostructures and contribute to the selective adsorption of mVOCs, in addition to better diffusivity in their inner and outer layers. In addition, the adsorption sites for oxygen and the analyte gas, as well as electronic transport, must also be increased in the porous structures. The proposal is an original and promising approach, as there is a lack of studies on the synthesis of highly porous ZnO/NiO sensors to detect mVOCs with high sensitivity, selectivity, stability, reproducibility and that resist interference from the relative humidity of the environment.