Spray-Printed UiO-66/Polyaniline Composite Films: Tuning MOF Content and Conductivity for Enhanced Ammonia Detection

Low-concentration ammonia detection is critical for applications in environmental monitoring, agricultural production, and occupational health protection. To enhance the material's gas-detection capability, a nanocomposite of a MOF and a conducting polymer was synthesized via in situ polymerization and systematically optimized for chemiresistive ammonia sensing. By varying the UiO-66 loading, the trade-off between gas-accessible surface area and electrical conductivity was established. A contactless spray-deposition technique was developed to fabricate composite films on compact interdigitated electrode platforms, overcoming the limitations of conventional drop-casting methods in film uniformity and device reproducibility. The optimized 5 wt % UiO-66/PANI sensor demonstrated exceptional performance, with 138% sensitivity at 100 ppb ammonia, representing nearly a three-fold improvement over pristine PANI (48% at 100 ppb). The sensor exhibited excellent selectivity toward ammonia over common interfering gases, robust stability across varying humidity conditions, and consistent performance over long-term cyclic testing. An open-space demonstration in a laboratory environment validated the sensor's real-time ammonia-monitoring capability, with performance comparable to that of a commercial ammonia sensor. This work provides a systematic approach to optimizing MOF/conducting polymer composites for gas-sensing applications via a reliable selected-area deposition method. The results demonstrate the potential of UiO-66/PANI nanocomposites as a practical platform for ammonia detection in environmental and industrial settings.