Fast room-temperature NH₃ detection enabled by plasma-engineered UiO-66/rGO on 3D silicon micropillar arrays

Room-temperature NH₃ sensors frequently suffer from planar mass-transfer limitations and sluggish interfacial charge-transfer dynamics, leading to prolonged response times (>150 s). Herein, we report a hierarchical engineering integration strategy—combining material selection, three-dimensional (3D) architecturing, and plasma surface engineering—to address these constraints. First, a UiO-66/rGO composite was synthesized as the sensing material to leverage its high porosity and intrinsic baseline sensing capabilities. Second, transitioning from conventional planar electrodes to a 3D silicon micropillar array established hierarchical gas-diffusion channels, which significantly increased the responsivity from 5.58% to 17.4% while simultaneously accelerating the response kinetics. Finally, O₂ plasma treatment grafted reactive oxygen functional groups and generated surface defects, further enhancing the responsivity to 23.91% and yielding a rapid response time of 77 s toward 40 ppm NH₃. Dynamic sensing tests experimentally verified a practical limit of detection of 0.385 ppm. The sensor also exhibited stable humidity tolerance and robust long-term reliability (>90% performance retention over 30 days). This work demonstrates an effective materials–structure–surface integration paradigm for practical room-temperature NH₃ monitoring.