Dual-emission ratiometric fluorescent sensor based molecularly imprinted nanoparticles for visual detection of okadaic acid in seawater and sediment

•A dual-emitting fluorescence nanosensor for okadaic acid (OA) was prepared.•The ratiometric nanosensor based molecularly imprinted polymers was optimized.•The nanosensor possesses self-referencing ability and visual detection for OA.•Seawater and sediments samples were sensitively analyzed by the nanosensor. A dual-emitting ratiometric fluorescence nanosensor based on novel molecularly imprinted polymers (MIPs), which possesses self-referencing ability by nitrobenzoxadiazole (NBD) as recognition signal and new carbon dots (CDs) as interior label, has been prepared for sensitive and visual detection of okadaic acid (OA) in seawater and sediment samples. The analyte can rapidly enhance the fluorescence intensity of NBD at 549 nm, but will not change the CDs’ fluorescence signal at 667 nm. The nanosensor has a linear fluorescence enhancement response in the range of 100∼1770 ng L−1 with a limit of detection of 25 ng L−1, and excellent selective recognition for OA over its interferences. The ratiometric fluorescence nanosensor has been successfully applied to detect OA in seawater and sediment samples. The results show that the nanosensor has high recoveries at four spiking levels of OA ranged from 90.0 % to 107.0 % with the relative standard deviation less than 4.1 % (n = 3). More importantly, a reliable visual sense change with two distinct color tonality from bright pink to yellow green can be easily differentiated by the naked eyes during fluorescence analysis, which demonstrates promising potential for the applications of molecularly imprinted sensors in trace analysis of marine environmental matrix.