Construction of Pt/TiO2 heterojunction composite supported on N, P-Co-doped hollow carbon and study on the electrochemical sensing performance for Cu2+

PNHC@Pt/TiO₂ core–shell heterojunction for trace Cu²⁺ monitoring. • N/P doping & O defects boost Cu²⁺ coordination and enrichment. • Low LOD 0.006 µM, wide linear range 0.001–20 µM. • Excellent selectivity against multiple coexisting heavy metal ions. • Reliable recoveries (87.1–103.3%) in tap water, soil, serum. Copper ion (Cu 2+ ) 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/TiO 2 nanoparticles (PNHC@Pt/TiO 2 ) was developed for the ultrasensitive detection of Cu 2+ . 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 Cu 2+ . Compared to bare and single-component electrodes, the PNHC@Pt/TiO 2 -modified GCE delivered an enlarged electroactive surface area (0.1289 cm 2 ) 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 Cu 2+ 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⁺, Ni 2+ , Co 2+ , Zn 2+ , Cd 2+ ), good reproducibility, and long-term stability (83.7% current retention after 8 days). Practical applicability was validated by successful determination of Cu 2+ 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.