A bifunctional monomer molecularly imprinted electrochemical sensor based on AuNPs@CoNi MOF and electrochemically activated graphite paper for the highly sensitive and specific detection of caffeine

Abstract

This study presents the development of a high-performance electrochemical sensor predicated on a dual-functional monomer molecularly imprinted polymer (MIP) specific recognition mechanism, designed for the highly sensitive and selective detection of caffeine in beverages. Innovatively, the sensor utilizes electrochemically activated graphite paper (EAGP) as the substrate, which, subsequent to electrochemical modulation, integrates a flexible porous architecture with enhanced electrochemical activity, thereby offering a stable platform for the sensing interface. The sensor integrates a cobalt-nickel metal-organic framework–gold nanoparticle composite (AuNPs@CoNi MOF) as a signal amplification element; exploiting the MOF’s elevated specific surface area for effective target molecule enrichment and harnessing the superior conductivity of AuNPs to establish efficient electron transport channels. Density functional theory (DFT) was employed to accurately identify 3-thiopheneacetic acid and o-phenylenediamine as the optimal dual-functional monomer pair, establishing a synergistic dual mechanism of “AuNPs@CoNi MOF enhancement coupled with dual-functional monomer MIP specific recognition.” Moreover, azide-alkyne cycloaddition click chemistry was utilized to accomplish oriented and robust covalent linkage between the composite and the EAGP substrate, resulting in a uniform sensing interface. Experimental findings illustrate that the sensor demonstrates excellent analytical performance, characterized by a detection range spanning from 10 nM to 200 μM and a detection limit reaching as low as 1.5 nM. This innovative architecture not only markedly improves detection sensitivity and selectivity but also offers benefits including cost-effectiveness, portability, and operational simplicity, thereby furnishing a novel technical strategy for rapid on-site screening and large-scale caffeine detection in beverages.