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

In this study, we present a novel composite electrode based on nitrogen and sul-
fur co-doped carbon quantum dots (NSCQDs), synthesized using Senna auricu-
lata biomass, a natural and renewable source. X-ray diffraction (XRD) analysis
revealed high crystallinity of the synthesized material, with the NSCQD signa-
ture 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 compos-
ite 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 via-
bility. 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 selectiv-
ity and sensitivity. The NSCQD/CoHCF composite electrode outperforms many
existing sensor technologies and holds significant promise for reliable and effi-
cient dopamine detection in real-world applications.