Design and fabrication of Punica granatum peel‑derived NSCQD/iron hexacyanoferrate ternary composite for simultaneous detection of ascorbic acid, uric acid, and resorcinol

This work reports the synthesis of a novel paraffin-impregnated graphite electrode (PIGE) modified by N- and S-doped carbon
quantum dot (NSCQD)/iron hexacyanoferrate composite for the electrochemical detection of resorcinol (RS), uric acid (UA),
and ascorbic acid (AA). Using pomegranate (Punica granatum) peel as the carbon source, the NSCQDs were synthesized
in an environmentally friendly manner. When combined with FeHCF, the NSCQDs formed a high-performance composite
with enhanced electrochemical properties. The morphology, crystallinity, and chemical composition of the composite were
investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron
spectroscopy (XPS) analysis, respectively, which revealed a structure that was clearly defined and contained active spots that
were suitable for redox reactions. Electrochemical tests revealed the sensor’s high sensitivity, measuring 523.4 mA/mol/L
for AA, 451.22 mA/mol/L for UA, and 372.1 mA/mol/L for RS. The sensor has low limits of detection of 2 × 10 −6 mol/L,
3 × 10 −6 mol/L, and 5 × 10 −6 mol/L for AA, UA, and RS, respectively, with a linear detection range of 10 × 10 −6 mol/L to
8000 × 10 −6 mol/L for all analytes. Superior conductivity was brought about by the addition of graphene, redox activity
was increased by FeHCF, and enhanced adsorption and catalysis were achieved by the introduction of electron-rich sites by
NSCQDs. The identification of AA in Limcee tablets, UA in Allopurinol tablets, and RS in hair color solutions served as
examples of real-world applicability. The electrode outperformed traditional electrodes in terms of sensitivity and decreased
oxidation potential, and it demonstrated outstanding stability, maintaining 95% of its performance after 50 cycles. This study
demonstrates the NSC/FeHCF-modified PIGE’s potential for real-world uses in environmental monitoring, pharmaceutical
quality assurance, and clinical diagnostics.