Enhanced Near-Infrared Photogenerated Carrier Transfer via Doublet-State Excitation in D-π-A Structures for Biosensing

The feedback mechanisms of living systems to external signals are vital for survival, particularly through the conversion of light into bioelectric signals by photosensitive molecules, that regulate biological behavior and physiological processes. Nonetheless, the application of materials that rely on near-infrared (NIR) responses for in vivo or opaque sample analysis has been limited. Here, we report the preparation of a C3N2-based doublet-state system for developing novel NIR-responsive materials. Photogenerated carriers are generated from doublet-state dangling bonds in C3N2 and transferred to the highly conductive graphitic materials via donor-π-acceptor conjugated structures, leading to nearly 700-fold enhancement in NIR photoelectric conversion. These materials were further applied for real-time detection of tetracycline in a single drop of whole blood, demonstrating better sensitivity in NIR photoelectrochemical biosensing, which paves the way for broader applications of in vivo biofeedback.