Construction of Pt/TiO₂ heterojunction composite supported on N, P-Co-doped hollow carbon and study on the...

Copper ion (Cu²⁺) is a prevalent heavy metal contaminant in industrial wastewater and natural water bodies. Although it plays a vital role as a trace element in human physiology, overconsumption can result in severe systemic disorders. In this work, a novel electrochemical sensing platform based on P, N co-doped hollow carbon (PNHC) decorated with Pt/TiO₂ nanoparticles (PNHC@Pt/TiO₂) was developed for the ultrasensitive detection of Cu²⁺. The composite was systematically characterized by SEM, TEM, XRD, FTIR, Raman spectroscopy, and XPS, confirming the formation of a core-shell structure with a uniform spherical morphology (104.20 ± 0.21 nm), along with N/P heteroatoms that provide specific coordination affinity toward Cu²⁺. Compared to bare and single-component electrodes, the PNHC@Pt/TiO₂-modified GCE delivered an enlarged electroactive surface area (0.1289 cm²) and lower charge-transfer resistance; under the optimized parameters (pH 5.0, accumulation potential -0.8 V, accumulation time 180 s, and modifier volume 5 µL), this sensor presented a Cu²⁺ linear detection range of 0.001-20 µM, a low limit of detection (LOD) of 0.006 µM (S/N = 3), and a high sensitivity of 6.102 µA µM^-1. The sensor also exhibited excellent selectivity against common interfering ions (K⁺, Na⁺, Ni²⁺, Co²⁺, Zn²⁺, Cd²⁺), good reproducibility, and long-term stability (83.7% current retention after 8 days). Practical applicability was validated by successful determination of Cu²⁺ in tap water, soil, and serum samples with recoveries ranging from 87.1% to 103.3%, demonstrating the reliable performance of the proposed sensor for environmental and biological monitoring.