Wavelength-regulated switchable photoelectrochemical system for concurrent detection of dual antibiotics

Concurrent detection of antibiotics with high sensitivity and reliability is always of high importance for food safety and environmental monitoring. Herein, a wavelength-dependent photoelectrochemical (PEC) aptasensor based on TiO₂–Ag/nitrogen doped graphene composites (TiO₂–Ag/NDG) was developed for concurrent detection of two antibiotics with signal amplification function. The as-fabricated ternary nanocomposites could concurrently detect two antibiotics using two different aptamer molecules as recognition elements, amplify the photocurrent outputs and perform a photocurrent-switchable operation, where photocurrents could be switched between anodic direction and cathodic direction via simply regulating the irradiation wavelength. Such proposed wavelength-dependent PEC sensing strategy was capable of concurrently detecting chloramphenicol (CAP) with a wide linear detection range from 50 pM–10 nM under irradiation of 380 nm and tetracycline (TET) with a linear detection range from 100 pM to 100 nM under irradiation of 600 nm, respectively. The limits of detection (LOD) for CAP and TET were 16.7 pM and 30 pM, respectively. Moreover, this PEC sensor also displayed good specificity and outstanding reliability in real sample applications. This wavelength-dependent PEC strategy could be conveniently adapted to other applications in food safety biosensing and environmental monitoring.