Bifunctional Carbon‐Sensitized Hollow Heterojunctions for Dual‐Mode Sensing of Emerging Contaminant 6‐PPD

ABSTRACT N‐(1,3‐dimethylbutyl)‐N′‐phenyl‐p‐phenylenediamine (6‐PPD), a ubiquitous rubber tire antioxidant, poses a severe threat to ecological safety due to its pronounced ecotoxicity. This work achieves the unprecedented dual‐mode photoelectrochemical and electrochemical (PEC‐EC) sensing of 6‐PPD through a dual‐mode platform endowed with bifunctional catalytic signal amplification. Integrating a novel hollow Bi@BiOBr/CdLa 2 S 4 heterojunction with multiwalled carbon nanotubes, this dual‐mode platform delivers highly stable, efficiently amplified signals. It demonstrates exceptional sensing performance with remarkably broad linear ranges from 1 to 10000 nM for PEC and 1 to 20000 nM for EC. By coupling Kelvin probe force microscopy and density functional theory with comprehensive characterizations, the intrinsic sensing mechanisms, specifically the charge transfer pathways and catalytic adsorption preferences, are systematically elucidated. Crucially, this dual‐signal cross‐validation ensures reliable quantification in complex real‐world matrices, and portable on‐site analysis is achieved via smartphone Bluetooth integration. Ultimately, by synergizing advanced heterojunction engineering with a dual‐mode sensing strategy, this work establishes a robust and highly efficient methodology for emerging contaminant monitoring with exceptional application prospects.