Bioinspired 2D inverse opal PANI/Ag composites for ultra-fast room-temperature ammonia sensing: Synergistic vortex effects and metal catalysis mechanisms

The development of highly sensitive and rapid-response/recovery room-temperature NH₃ sensors is critically demanded for environmental monitoring and healthcare diagnostics, yet remains scientifically challenging. Inspired by the two-dimensional ordered macroporous structure of peacock feathers, two-dimensional inverse opal (2DIO) polyaniline/silver (PANI/Ag) composites were fabricated via a sacrificial templating method. By integrating the advantages of gas diffusion of highly ordered macroporous structures with the catalytic activity of Ag, significant improvements in NH₃ sensing performance were achieved. Computational fluid dynamics (CFD) simulations demonstrated that the 2DIO structure induced vortex effects, which significantly reduced the gas velocity. Concurrently, macroporous channels (~ 240 nm diameter) enhanced adsorption/desorption kinetics. The fabricated 2DIO PANI/Ag sensor exhibited a remarkable response of 1153% to 100 ppm NH₃, with ultra-fast response/recovery times of 3 s/56 s, exhibiting a 420-fold improvement in response/recovery speed compared to pure PANI (126 s/325 s). A further developed wearable detection module successfully discriminated exhalation signals between simulated chronic kidney disease (CKD) patients and healthy individuals, providing a new strategy for noninvasive medical diagnosis. <i>In-situ</i> Fourier transform infrared spectroscopy (<i>in-situ</i> FT-IR) real-time tracking of NH₃ adsorption/desorption processes confirms a chemisorption-dominated sensing mechanism. Density functional theory (DFT) calculations showed that the charge transfer at the PANI/Ag interface enhanced the adsorption of NH₃, which significantly enhanced the molecular affinity. This study provides a viable pathway for developing high-performance flexible NH₃ gas sensors through an interdisciplinary approach combining structural bionics, simulation optimization, theoretical analysis, and experimental validation.