Iodine-Vacancy BiOI Nanosheets-Embedded on Bi2O3 Electrospun Heterojunction for Label-Free Interleukin-6 Photoelectrochemical Aptasensor with High Signal-to-Noise Ratio.

Lower-background photoelectrochemical (PEC) bioanalysis is crucial for high-sensitivity biomolecule detection and early clinical disease screening by effectively eliminating matrix interference and reducing the background photocurrent noise. In this work, a novel, simple, label-free split-type PEC aptasensor was successfully constructed for interleukin-6 (IL-6) analysis based on electrospun Bi2O3 nanofibers (NFs) coupled with in situ grown iodine vacancy (IV) BiOI nanosheets (IV-BiOI/Bi2O3 NFs). The introduction of heterojunction interfaces and IV in BiOI/Bi2O3 NFs can synergistically regulate light absorption capacity, optimize electronic band structure, efficiently promote the separation and migration of photogenerated electron-hole pairs, and inhibit charge recombination, thus greatly enhancing PEC photocurrent response. Aptamer-capped mesoporous silica nanospheres encapsulate ascorbic acid to specifically recognize IL-6 (10.0 ng/mL), triggering large amounts of AA release. This boost-on photocurrent response yields a 30.9-fold enhancement versus the control group. By separating biorecognition reactions from photocurrent readout, the split-type strategy avoids electrode surface biomodification interference and achieves an ultralow background. The sensor presents a wide linear range, low detection limit (0.6 pg/mL), favorable selectivity, and stability and achieves reliable detection in real serum and sweat samples. This work provides a new paradigm for defective heterojunction-based PEC biosensing with label-free operation, simple fabrication, and a high signal-to-noise ratio.