In Situ CdS-Mediated Organic Photoelectrochemical Transistor Sensor for Highly Sensitive H2S Detection

Hydrogen sulfide (H2S) serves as an important gasotransmitter implicated in vascular regulation, neuroprotection, and redox homeostasis, and its aberrant fluctuation is closely associated with diverse pathological disorders. Consequently, the development of sensitive and reliable H2S detection methodologies holds considerable significance. Organic photoelectrochemical transistors (OPECTs) integrate photoelectrochemical signal generation with transistor-level amplification, emerging as promising sensing platforms owing to their high sensitivity and low background interference. Nevertheless, the majority of reported OPECT-based sensors rely on the construction of intricate heterojunctions that demand precise energy-level alignment and elaborate material design, thereby elevating system complexity. Herein, an in situ CdS-mediated OPECT sensing platform is innovatively developed for highly sensitive H2S detection and ex vivo analysis of rat brain microdialysates. Specifically, H2S selectively reacts with immobilized Cd2+ to generate n-type semiconductor CdS in situ, which effectively induces and modulates the photovoltage at the gate interface. The modulated photovoltage further regulates the dedoping process of the PEDOT:PSS channel, enabling efficient transduction of interfacial chemical events into amplified current signals. Under optimized conditions, the sensor presents a broad linear response toward H2S ranging from 100 nM to 10.0 mM, with a low detection limit of 51.1 nM. Impressively, by coupling with microdialysis sampling, the platform achieves quantitative analysis of H2S in different regions of rat brain tissue with favorable accuracy and reliability. This work provides a straightforward and efficient strategy for constructing chemically driven photoelectric-transistor coupled amplification sensing systems without complex heterojunction engineering, demonstrating great potential for in situ and in vivo detection of biomolecules in complex biological matrices.