Thiourea-functionalized electroanodized pencil graphite electrode for sensitive electrochemical detection of 4-aminophenol

This study presents a novel and cost-effective electrochemical sensor for the sensitive and selective detection of 4-aminophenol (4-AP) using a pencil graphite electrode (PGE) modified through an electroanodization process in the presence of thiourea. The resulting thiourea-functionalized anodized PGE (ATPGE) demonstrates a porous, graphene oxide-like surface architecture with enhanced electrochemical properties. Surface characterization via field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX) confirmed the formation of nanosheet structures and the successful incorporation of heteroatoms, including sulfur and nitrogen, derived from thiourea. Electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) revealed significantly improved charge transfer and current responses at the ATPGE compared to unmodified electrodes. The ATPGE exhibited a low detection limit of 6 μM and a wide linear response range (10–110 μM) for 4-AP with high sensitivity and reproducibility (RSD < 2%). Additionally, real sample analysis from dam water confirmed the method's applicability, with recovery rates ranging from 94.6% to 103.1%. The fabricated sensor demonstrates high selectivity against common interferents and offers a reliable, low-cost alternative for environmental and pharmaceutical monitoring of 4-AP. • A thiourea-functionalized anodized pencil graphite electrode (ATPGE) was fabricated for the first time for 4-aminophenol detection. • Electroanodization created a porous graphene oxide–like surface, incorporating sulfur and nitrogen heteroatoms that enhanced electron transfer efficiency. • The ATPGE exhibited excellent analytical performance with a low detection limit of 6 μM and two linear ranges (10–40 and 40–110 μM). • Real water analysis demonstrated high accuracy with recovery values of 94.58–103.14% and RSD < 2.5%.