Interfacial Charge Separation Engineering Enables Dual Small-Molecule Probe-Based Photoelectrochemical Multi-Enzyme Sensing

Photoelectrochemical (PEC) biosensors remain constrained in multianalyte detection due to inefficient charge separation and signal crosstalk. To address these challenges, we developed a dual small-molecule probe-modulated charge separation system by integrating coumarin 6 (C6) and a silane probe (SP) into a titanium-based metal organic framework (Ti MOF). The porous crystalline structure and favorable electron transport properties of the Ti MOF enable efficient interfacial electron redistribution between the molecular probes and the MOF scaffold. Specifically, Cu2+ ions released by pyrophosphatase (PPase) coordinate with C6 to initiate ligand-to-metal charge transfer, while hydroquinone generated by α-glucosidase (α-Glu) induces in situ formation of silicon nanoparticles from the silane precursor. These dual mechanisms collectively create distinct charge separation pathways that suppress electron–hole recombination and enhance photocurrent output. Leveraging the orthogonal recognition mechanisms of the probe-substrate interactions, we achieved selective detection of α-Glu and PPase, with detection limits of 0.27 mU/mL and 0.01 mU/mL, respectively. This work presents a generalizable strategy for multitarget PEC biosensing via probe-directed energy band modulation, offering new insights into the further development of PEC sensing systems.