MoS2/TiO2 p–n-Type Heterojunction as a Photoelectrochemical Biosensor for Detecting Dopamine

Dopamine is a crucial neurotransmitter associated with neurological regulation and requires precise detection due to its concentration-dependent correlation with neurological disorders. In this work, a novel photoelectrochemical (PEC) sensor based on MoS2/TiO2 nanotubes (MoS2/TiO2 NTs) with p-n heterojunction nanocomposite was prepared through hydrothermal method. The constructed p-n heterojunction effectively enhanced charge separation efficiency, as systematically verified by multidimensional characterization including XRD, SEM, TEM, XPS, EIS, PL, UV–vis, M–S, etc. Under visible-light illumination, the optimized sensor demonstrated exceptional dopamine detection performance with a low detection limit of 0.074 μM (S/N = 3) in the range of 1–100 μM. This platform exhibited remarkable operational stability, selectivity, and fast response characteristics. Based on electrochemical analysis and density functional theory calculations, the PEC enhancement mechanism was revealed. This work provides new insights into heterojunction engineering for neuroimaging biomarker detection.