Design and fabrication of nitrogen- and sulfur-doped carbon quantum dot-integrated cobalt hexacyanoferrate hybrid sensor electrodes for enhanced dopamine detection

Abstract

In this study, we present a novel composite electrode based on nitrogen and sulfur co-doped carbon quantum dots (NSCQDs), synthesized using Senna auriculata biomass, a natural and renewable source. X-ray diffraction (XRD) analysis revealed high crystallinity of the synthesized material, with the NSCQD signature being indistinct due to irregular stacking and low concentration. Scanning electron microscopy (SEM) confirmed the formation of larger spherical hybrid clusters, attributed to the incorporation of NSCQDs. We analyzed the composite electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed efficient electron transfer, minimal background current, and a broad detection range. The DPV analysis exhibited excellent linearity and sensitivity, with a proportional decrease in peak currents over a dopamine concentration range of 20–7000 nM. The sensor achieved a high sensitivity of 0.01521 µA/nM and a low detection limit of 0.1 nM. The modified electrode also demonstrated low noise and high reproducibility, underscoring its practical viability. This sustainable technique not only adheres to green chemistry principles, but it also improves the electrochemical characteristics of NSCQDs, making them extremely useful for dopamine sensing. The combination of NSCQDs and cobalt hexacyanoferrate (CoHCF) produced a composite electrode with high selectivity and sensitivity. The NSCQD/CoHCF composite electrode outperforms many existing sensor technologies and holds significant promise for reliable and efficient dopamine detection in real-world applications.