Aptamer-functionalized solution-gated graphene transistor for rapid detection of trace scandium.

The growing exploitation of rare earth resources has led to the migration and accumulation of Scandium (Sc) within food systems, giving rise to emerging food safety concerns. Conventional techniques for Scandium (III) ions (Sc3+) detection are limited by labor-intensive sample preparation, high instrumentation costs, and poor suitability for rapid on-site screening. Here, we report a highly sensitive and selective biosensor for Sc3+ that integrates a Sc3+-specific nucleic acid aptamer (Sc-1) with a solution-gated graphene transistor (SGGT). The sensing mechanism relies on aptamer conformational changes induced by Sc3+ binding, which modulate the interfacial charge distribution and electric double-layer properties at the gate electrode, producing a quantifiable shift in the graphene channel current. The optimized aptamer-functionalized Sc-SGGT (Scandium-specific solution-gated graphene transistor) biosensors exhibit a wide dynamic range from 1 pM to 100 nM and an excellent sensitivity with a limit of detection (LOD) calculated to be 0.736 pM. They also demonstrate robust anti-interference capability against common coexisting ions and rare-earth analogs. Moreover, spike recovery experiments in real food samples yield excellent recoveries, confirming the method's practicality for complex matrix analysis. Together, these results establish a rapid, sensitive, and reliable strategy for Sc3+ detection, presenting a promising platform for food safety surveillance of rare-earth contaminants.