Dual Heterojunction Strategy on ZIF-8 for High-Performance Ammonia Sensor

The reliable detection of trace ammonia (NH₃) under high-humidity conditions, primarily in exhaled breath and environmental settings, remains a challenge due to issues of long-term stability, selectivity, and interference from other gases. Heterostructure engineering has recently emerged as a promising pathway to overcome these limitations. Here, we present a dual heterojunction sensor based on zeolitic imidazolate framework-8 (ZIF-8) functionalized with a conformal copper oxide (CuO) nanolayer and an electrically conductive poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS) film via a kinetically controlled solvothermal process followed by dip coating. The dual heterojunction within ZIF-8@CuO@PEDOT: PSS nanostructure resulted in enhanced NH₃ absorption, rapid charge transfer, and efficient gas diffusion. The sensor exhibited a fast response magnitude of 9954 toward 50 ppm NH₃, a rapid response/recovery of 8/2 s, excellent long-term stability, and high selectivity against common interfering gases at ambient conditions. The superior sensing performance is attributed to the synergistic interactions among the porous ZIF-8 scaffold, CuO catalytic sites, and the π-conjugated PEDOT: PSS network, which collectively enable efficient signal transduction and robust functionality under different environments. This work introduces a new paradigm in dual heterojunction ZIF-8-based nanostructured sensor, demonstrating strong potential for environmental monitoring and non-invasive clinical diagnostics for kidney dysfunction.