Marangoni Effect-Mediated Interfacial Regulation of Oriented Laser-Induced Graphene–MOF Heterojunctions toward High-Performance Dual-Mode PEC-SERS Biosensor

Heterojunctions of graphene and MOFs are highly desired for optoelectronic sensing analysis, yet disordered MOF growth severely restricts interfacial charge transfer and sensing performance. Herein, we report a solution-phase synthesis by taking advantage of the Marangoni effect to achieve the oriented growth of a porphyrin-based MOF on laser-induced graphene (LIG), yielding a LIG–MOF heterojunction with vertically aligned spike arrays. The intimate heterointerface enables ordered 3D electron transport and generates an interfacial electric field (IEF) to boost photoelectrochemical (PEC) properties, offering an enlarged carrier density by 3.0 × 105-fold compared with LIG. For surface-enhanced Raman scattering (SERS), a selectively enhanced Raman signal of the MOF by methylene blue (MB) is observed on LIG–MOF, uncovering a competitive charge transfer mechanism. In LIG–MOF, IEF properly directs electrons from LIG to the MOF while blocking electron injection into MB; photoexcited electrons from MB transfer stepwise to the MOF, enhancing its Raman signal. Consequently, a PEC-SERS biosensing chip is developed with LIG–MOF via aptamer-gated controlled MB absorption. The biosensing chip can simultaneously generate in situ PEC and SERS responses under 532 nm laser excitation via the LIG–MOF heterojunction for accurate and sensitive detection of patulin. This work provides a feasible interfacial-engineering strategy for the design and fabrication of high-performance dual-mode biosensors for advanced analytical sensing.