Breathing new life into ammonia detection with rGO-MIL-53(Al) composites

The integration of metal-organic frameworks (MOFs) and conductive materials has yielded significant advancements in gas sensing technology. This study explores the synergistic potential of MIL-53(Al) and reduced graphene oxide (rGO) for enhanced ammonia detection. rGO composites with MIL-53(Al) were prepared, varying the proportion of MIL-53(Al), and subsequently characterized using multiple techniques. By leveraging the high surface area and tailored microporous structure of MIL-53(Al) alongside rGO's exceptional charge transport mechanics, our hybrid network demonstrates outstanding gas responsiveness and rapid reaction speeds. Within the investigated material matrix, the 20 wt% rGO-MIL-53(Al) platform exhibited maximum selectivity and optimal signalling performance during ammonia gas exposure. This optimized layer yielded response values reaching -11.40 under 60 000 ppm and -5.61% at 2000 ppm concentrations, while maintaining an easily detectable signal path as low as 1 ppm. Furthermore, long-term durability evaluations proved that the device's electrical signal metrics remained entirely reproducible and highly stable throughout a twelve-month aging interval. At the operating temperature of 110 °C, the target ammonia molecules interact with surface-adsorbed oxygen species, releasing trapped electrons back into the p-type rGO network to modulate carrier concentration via efficient charge transport, resulting in the highest sensing response for ammonia. Among the tested composites, a Gaussian trend in sensitivity reveals that 20% MIL-53(Al) loading, corresponding to the percolation threshold, achieves the optimal balance for the interplay between ammonia gas adsorption capacity and electrical conductivity, yielding the highest sensitivity. The FE-SEM and TEM analysis clearly shows the presence of this kind of interface. Although existing ammonia sensors may demonstrate impressive performance under controlled conditions, their effectiveness is often hindered by the instability of the sensing materials. In contrast, our rGO-MIL-53(Al) composite exhibits excellent structural and chemical stability due to its durable structural framework. This advantageous combination positions our robust material system as a promising candidate for practical long-term gas-sensing applications. This research underscores the promise of MOF-based composites in gas sensing, opening avenues for developing innovative sensing platforms for more accurate and efficient gas detection.