A Cellulose-Based Self-Powered Ammonia Sensor for Food Freshness

Smart packaging for meat products enables real-time evaluation of food freshness by monitoring volatile gases released during spoilage, among which ammonia (NH₃) is widely recognized as one of the most representative indicator molecules due to its close correlation with protein degradation. Compared with conventional sensing systems that rely on external power sources, integrated self-powered ammonia sensors offer advantages such as nondestructive detection, structural simplicity, and portability, demonstrating potential for smart packaging applications. In this work, a mechanically reinforced three-dimensional cellulose-based porous network was constructed through hydrogen-bonding interactions between sodium carboxymethyl cellulose (CMC-Na) and sodium alginate (SA), combined with Ca²⁺-induced ionic cross-linking. Ti₃C₂T_<i>x</i> (MXene) nanosheets were uniformly dispersed within the network to form continuous conductive pathways, which contributed to the elevation of the surface potential for the positive triboelectric material and enhanced the electrical response to NH₃ gas. The fabricated triboelectric nanogenerator (TENG) delivers an open-circuit voltage of approximately 160 V and a maximum short-circuit current of 16 μA. It exhibits a high linearity to NH₃ concentrations ranging from 3 to 100 ppm, with a sensitivity of 1.236 V/ppm, a low limit of detection (LOD) of 0.95 ppm, and rapid response/recovery times of 16 and 38 s, respectively. Notably, the relative voltage variation (ΔV/V₀) reaches as high as 77% under 100 ppm of NH₃ exposure. This study provides a feasible material design strategy and device implementation route for self-powered NH₃-sensing smart packaging systems.