Wide-range and high-accuracy wireless sensor with self-humidity compensation for real-time ammonia monitoring

Real-time and accurate biomarker detection is highly desired in point-of-care diagnosis, food freshness monitoring, and hazardous leakage warning. However, achieving such an objective with existing technologies is still challenging. Herein, we demonstrate a wireless inductor-capacitor (LC) chemical sensor based on platinum-doped partially deprotonated-polypyrrole (Pt-PPy⁺ and PPy⁰) for real-time and accurate ammonia (NH₃) detection. With the chemically wide-range tunability of PPy in conductivity to modulate the impedance, the LC sensor exhibits an up-to-180% improvement in return loss (S11). The Pt-PPy⁺ and PPy⁰ shows the p-type semiconductor nature with greatly-manifested adsorption-charge transfer dynamics toward NH₃, leading to an unprecedented NH₃ sensing range. The S11 and frequency of the Pt-PPy⁺ and PPy⁰-based sensor exhibit discriminative response behaviors to humidity and NH₃, enabling the without-external-calibration compensation and accurate NH₃ detection. A portable system combining the proposed wireless chemical sensor and a handheld instrument is validated, which aids in rationalizing strategies for individuals toward various scenarios.