Visible-light-driven photoelectrochemical aptasensor based on reduced graphene oxide/Ti–Fe–O nanotube arrays for highly sensitive and selective determination of microcystin-LR

Abstract Microcystin-LR (MC-LR) is one of the highly concerned microcystins with strong hepatotoxicity. In this work, a visible-light-driven photoelectrochemical (PEC) aptasensor has been successfully developed for MC-LR based on reduced graphene oxide (rGO)/Ti–Fe–O nanotubes (NTs). Vertically-aligned Ti–Fe–O NTs are in situ prepared on Ti–Fe alloy by electrochemical anodic oxidation to provide an outstanding photoanode substrate with good visible light response ability. RGO is further electrochemically deposited onto Ti–Fe–O NTs, acting not only as the molecular bridge for immobilization of MC-LR aptamers (Apt), but also as the PEC signal amplification element. Attributed to the large π-conjugated structure of rGO which can effectively promote photo-generated electron-hole separation, as well as the good visible-light activities of Ti–Fe–O NTs, the constructed Apt/rGO/Ti–Fe–O NTs sensor exhibits prominent determination performance for MC-LR with a detection limitation of 5 fM. High selectivity and stability towards MC-LR is further proven to the aptasensor by performing the co-existing experiments and long-termed replicates. Meanwhile, satisfactory results are obtained when applying in real water sample investigation. A promising visible-light-driven PEC platform for highly sensitive and selective detection of MC-LR has thus been provided.