Dual-Analyte Detection of Dopamine and Folic Acid Using a 3D Honeycomb Structured Reduced Graphene Oxide/Polypyrrole-Polyoxometalate Porous Film

Electrochemical sensors capable of detecting different types of biomolecules using a single electrode are highly desirable for simplifying analytical platforms and expanding their practical applicability. Herein, we develop a multifunctional electrochemical sensor based on a 3D honeycomb-like porous rGO/PPy-POM composite film for the independent detection of dopamine (DA) and folic acid (FA), two chemically distinct and clinically relevant biomolecules. The electrode is fabricated through a facile, low-cost, and environmentally friendly breath figure method to create a 3D porous reduced graphene oxide (rGO) framework, followed by codeposition of polypyrrole (PPy) and polyoxometalates (POMs). The synergistic effect of the hierarchical porous structure and the electroactive components significantly enhances the sensor's surface area, charge transfer efficiency, and electrochemical response. The as-prepared porous rGO/PPy-POM electrode exhibits excellent sensing performance toward DA and FA. It achieves a wide linear range of 0-2300 μM and a low detection limit of 72 nM within 0-10 μM for DA detection, while offers a linear range of 0-3500 μM and a detection limit of 82 nM in the low concentration range for FA detection. The sensor also shows excellent selectivity against common interferents, outstanding repeatability and reproducibility, and long-term operational stability. Importantly, in real human urine samples, the sensor yields recovery rates between 96.2 and 109.8%, confirming its reliability and accuracy for practical biological analysis. This work offers a robust strategy for constructing multifunctional electrochemical sensors capable of detecting diverse biomolecular targets using a unified sensing platform.