Hybrid Semiconductor Interfaces for Ultratrace Electrochemical Oxytocin Sensors

The design of hybrid semiconductor–polymer interfaces continues to advance the performance of electrochemical sensors. In this study, an ultrasensitive sensing platform is constructed by integrating a molecularly imprinted polymer (MIP), derived from upcycled polystyrene, with copper‐doped graphitic carbon nitride (CugCN). The Cu dopant modulates the electronic structure of gCN, enhances charge‐transfer kinetics, and increases the density of electroactive sites, while the MIP confers selective host–guest recognition toward oxytocin. The hybrid MIP@CugCN interface provides highly sensitive electrochemical detection of oxytocin, exhibiting a linear response over the concentration range of 100–900 nM with a detection limit of 34 pM as determined by differential pulse voltammetry. The sensor maintains high chemical fidelity, discriminating oxytocin from structurally related interferents, and exhibits robust operational stability, retaining more than 91% of its initial response after 15 days. When applied to untreated milk matrices, the platform provides recoveries of 92%–104% with minimal sample preparation. These results demonstrate that the semiconductor–polymer hybrid engineering provides a practical strategy for the highly selective electrochemical detection of oxytocin in complex milk matrices, with broader potential for food safety applications.