Self-restacked mildly reduced graphene oxide: Ultrasensitive ammonia recognition and real-time quality sensing of lamb

The limited response sensitivity of chemically reduced graphene oxide (RGO) to ammonia (NH 3 ), along with its low limit of detection (LOD) and poor selectivity, significantly restricts its application in the detection of meat freshness. Here, we fabricated homogeneous monolayer RGO self-stacking membrane that exhibited both strong sensitivity and an ultra-low LOD as an NH 3 sensor. The outstanding performance is mainly attributed to the synergistic effects of a high surface area—offering numerous adsorption sites—and residual oxygen-containing functional groups, which promote strong interactions with NH 3 through hydrogen bonding, protonation, and chemical reactions involving -N-H bond dissociation. The comprehensive ex-situ spectroscopic characterizations also clearly demonstrated the adsorption-desorption kinetics of NH 3 . Furthermore, the RGO sensor demonstrated strong potential for monitoring the freshness of lamb, with its responses showing high correlation with total viable count (TVC) and total volatile basic nitrogen (TVB-N) levels. These results underscore the promise of non-hybridized, undoped RGO-based sensors for practical applications in meat freshness assessment.