Flexible Room-Temperature Ammonia Sensor Using Multi-Heterojunction MoO3/CuO/Cu2O Nanoclusters for Noninvasive Kidney Disease Diagnosis

In this study, a flexible room-temperature ammonia (NH3) sensor is developed based on MoO3/CuO/Cu2O hybrid nanoclusters (HNCs), specifically designed for the noninvasive diagnosis of nephropathy. The MoO3/CuO/Cu2O HNCs achieve an ultralow detection limit of 0.73 ppm, with high sensitivity (0.163 ppm-1) and rapid response and recovery times (16.4 and 90.6 s). The integration of MoO3 (n-type) with CuO and Cu2O (p-type) forms multi-heterojunctions, enhancing gas-sensing performance through efficient charge separation and improved NH3 adsorption. Additionally, the sensor demonstrates excellent mechanical flexibility and long-term stability under dynamic deformation. To address humidity interference in exhaled breath analysis, the sensor with a hydrophobic polytetrafluoroethylene layer is coated via radio frequency sputtering, ensuring effective NH3 detection and differentiation between healthy individuals and kidney disease patients. In this work, the potential of multi-heterojunction nanostructures in developing high-performance, flexible gas sensors for practical health-monitoring applications is highlighted.