Fixed polarity fingerprint photoelectrochemical biosensor based on Zn-TCPP/ZnO composite for simultaneous detection...

In this work, a photoelectrochemical (PEC) biosensor based on a 'fixed polarity fingerprint' strategy was developed for simultaneous detection of bis(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) in the Yangtze River. A uniform Zn-TCPP/ZnO composite was formed by electrostatic self-assembly and modified on an ITO electrode. Two independent zones were immobilized with aptamers corresponding to DEHP and DBP, respectively. On the one hand, ZnO dominated the anodic photocurrent when exposed to UV-visible light. Conversely, Zn-TCPP dominated the cathodic photocurrent under visible light. The two photocurrents exhibited fixed opposite polarities, constituting unique polarity fingerprints for each target. Unlike dynamic polarity switching, this method avoids polarity reversal and interference from coexisting substances in environmental matrices. Sequential detection is achieved simply by switching the light source, without external electron donors/acceptors or complex data processing. The uniform composite ensures excellent signal consistency between the two zones. Under optimal conditions, DEHP showed a linear range of 5.00 × 10^-12∼5.00 × 10^-7 mol/L with a detection limit of 2.03 × 10^-13 mol/L under UV-visible light, while DBP exhibited a linear range of 1.00 × 10^-11∼5.00 × 10^-7 mol/L with a detection limit of 1.24 × 10^-11 mol/L under visible light. The biosensor demonstrated good stability and selectivity, and was successfully applied for simultaneous determination of DEHP and DBP in real water samples.