An ultra-sensitive flexible room-temperature H2S sensor enabled by PANI/MXene/Cu2O ternary nanocomposites for meat spoilage monitoring.

Hydrogen sulfide (H2S), a highly toxic gas released during meat spoilage, necessitates room-temperature real-time detection for accurate freshness assessment and potential health hazards mitigation. In this work, an ultra-sensitive flexible H2S sensor was developed by depositing a polyaniline/MXene/cuprous oxide (PANI/MXene/Cu2O) ternary nanocomposite onto a flexible substrate, and it operates reliably at room temperature. The sensing material was synthesized via in-situ polymerization of PANI on titanium carbide (Ti3C2Tx) MXene, followed by the strategic integration of Cu2O microparticles to construct a hierarchical heterostructure. The sensor exhibits a high response sensitivity of 24.72% ppm-1, a low theoretical detection limit of 0.456 ppb, and fast response/recovery times of 55 s and 35 s. It also delivers good selectivity, repeatability, long-term stability, and mechanical flexibility. A signal acquisition circuit integrating an OPA333 precision amplifier and a microcontroller was assembled for real-time quantitative detection of H2S release during shrimp spoilage, enabling effective tracking of H2S accumulation and discrimination of freshness stages. The enhanced gas-sensing performance stems from the synergistic combination of the highly conductive Ti3C2Tx network, the p-p heterojunction between PANI and Cu2O, and the reduction reaction of PANI with H2S, which facilitates rapid charge transport and effectively modulates the interfacial energy band alignment upon H2S exposure. This study provides an effective strategy for designing high-performance room-temperature flexible gas sensors for real-time meat freshness assessment.