Cobalt nanoparticle-encapsulated N-doped carbon nanotubes on 3D porous carbon: a novel platform for ultrasensitive electrochemical sensing of rutin

Abstract

This work develops an ultrasensitive electrochemical sensor for detecting rutin (Rt) using a composite material, Co@N-CNTs/3DHC. The composite integrates cobalt-encapsulated, nitrogen-doped carbon nanotubes within a three-dimensional porous carbon framework. We synthesized the material through a controlled pyrolysis method. First, cobalt-based metal–organic frameworks were grown in situ on the 3DHC substrate. The addition of dicyandiamide (DCDA) helped direct the morphology, and the 3DHC structure itself effectively suppressed precursor aggregation. This process yielded a uniform network of nitrogen-doped carbon nanotubes (N-CNTs) with diameters near 100 nm, inside which ultrafine cobalt nanoparticles (NPs) were confined. The integrated N-CNTs and 3DHC framework creates a hierarchical porous architecture that promotes efficient mass transport. In addition, the well-dispersed Co NPs substantially improve both electrical conductivity and electrocatalytic activity. Under optimized conditions, the Co@N-CNTs/3DHC/GCE exhibited two well-defined linear ranges from 0.1 to 50 nM and from 50 to 1000 nM, achieving an ultralow detection limit (LOD) of 0.04 nM. Furthermore, it was successfully applied to accurately determine the rutin content in real samples, including buckwheat and rutin tablets, yielding satisfactory recoveries (96.0% to 105.0%). This work provides a novel strategy for developing highly sensitive and stable methods for rutin detection, demonstrating significant potential for practical applications in pharmaceutical quality control and biomedical analysis.