An ultra-sensitive photoelectrochemical sensor based on ZnIn2S4/rGO nanocomposites for detection of oxytetracycline in water, food and organism samples

Residues of oxytetracycline (OTC) may cause the resistance of bacteria, and even have serious impacts on the ecosystem through the food chain. It was important to monitor OTC of low concentration for preserving human health and environmental safety. In this work, reduced graphene oxide doped ZnIn 2 S 4 (ZnIn 2 S 4 /rGO) nanocomposites were composited by straightforward one-step solvothermal reaction. The nanocomposites had superior light absorption property and stable photocurrent response. Because rGO not only had a large specific surface area for immobilizing abundant ZnIn 2 S 4 , but also accelerated charge transfer as an electron mediator. Additionally, the oxidation potential of OTC was more negative than the valence band potential of ZnIn 2 S 4 . So, OTC can be oxidized by photogenerated holes of the ZnIn 2 S 4 as electron donors, leading significant increase of photocurrent response. Based on this, a “signal-on” photoelectrochemical (PEC) sensor was constructed to achieve ultra-sensitive and specific detection of OTC. This sensor exhibited a wide detection range from 100 fM to 50 nM, an extremely low detection limit (61.2 fM) and excellent analytical performance in actual water, food and biological samples.