Graphitic Carbon Nitride/Poly(3-hexylthiophene) Nanocomposites for the Photoelectrochemical Detection of H₂O₂ in Living Cells

Herein, a metal-free photoelectrochemical (PEC) cathodic biosensor based on a composite material of graphitic carbon nitride (g-C3N4) and a conjugated polymer of poly(3-hexylthiophene) (P3HT) is proposed. The formation of a p–n heterojunction between g-C3N4 and P3HT through π–π stacking induced a high degree of molecular ordering, efficient charge separation, and a significantly enhanced PEC performance. The g-C3N4/P3HT PEC cathodic sensor implements sensitive and selective detection of hydrogen peroxide secreted from living cells in a wide linear range from 1.0 to 800 μM with a limit of detection of 0.38 μM. We believed that the metal-free PEC cathodic detection strategy opens up an excellent biodetection approach with high biocompatibility.