An "inside-outside" synergistic strategy modification graphitic carbon nitride-based photoelectrochemical aptasensor for highly sensitive detection of sulfadiazine.

An "inside-outside" synergistic modification strategy is proposed to construct a photoelectrochemical (PEC) sensing platform based on a boron-doped carbon nitride/nitrogen-doped carbon quantum dot (BCN/NCQDs) heterojunction. The inside modification refers to boron doping within graphitic carbon nitride to modulate its electronic structure, narrowing the bandgap and extending visible light absorption. The outside modification involves the formation of a 0D/2D heterointerface with NCQDs, which establishes a built-in electric field to facilitate directional charge separation. Material characterization shows that the heterojunction exhibits a photocurrent response of approximately 1100 nA and enhanced charge separation efficiency. An aptamer-functionalized PEC sensor was fabricated for the detection of sulfadiazine, yielding a linear range from 0.01 to 1000 ng/mL and a detection limit of 2.7 pM. The sensor shows selectivity, reproducibility (RSD = 3.253%), and stability in operation. In real water and milk samples, recoveries range from 98.53 to 104.73%, consistent with chromatographic methods. This work presents a strategy for designing photoelectrochemical materials and biosensors.