High-sensitivity detection of norfloxacin in milk and water: a bismuth-based photoelectrochemical aptasensing platform.

A novel photoelectrochemical determination method for norfloxacin (NOR) is presented using binary bismuth-based composites doped with gold nanoparticles (Au NPs). By combining two bismuth-based materials, we developed a sensitive photoelectrochemical aptamer sensing platform in which the NOR-specific aptamer was immobilized on a binary bismuth-based composite doped with gold nanoparticles (Au NPs). This platform utilizes a target-aptamer-specific recognition reaction to detect NOR levels. Spectral analysis of the bismuth composites indicated that the interaction between Bi₂Se₃ and Bi₂S₃ follows a 'Type Z' electron transfer pattern, while Au NPs enhance the signal through surface plasmon resonance effects. NOR was detected linearly over a range of 0.001 to 100 ng/mL, with a detection limit of 1 fg/mL. The method demonstrated excellent specificity and was successfully applied to determine NOR concentrations in spiked tap water and milk samples. Recovery ranged from 96.7 to 110.3%, with relative standard deviations not exceeding 2.3%. These findings suggest that the developed sensor has significant potential for detecting NOR in dairy products and domestic water sources.