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a b s t r a c tA novel molecular imprinting-based turn-on ratiometric fluorescence sensor was constructed via a facile sol-gel polymerization for detection of 2,4-dichlorophenoxyacetic acid (2,4-D) on the basis of photoinduced electron transfer (PET) by using nitrobenzoxadiazole (NBD) as detection signal source and quantum dots (QDs) as reference signal source. With the presence and increase of 2,4-D, the amine groups on the surface of QDs@SiO 2 could bind with 2,4-D and thereby the NBD fluorescence intensities could be significantly enhanced since the PET process was inhibited, while the QDs maintained constant intensities. Accordingly, the ratio of the dual-emission intensities of green NBD and red QDs could be utilized for turn-on fluorescent detection of 2,4-D, along with continuous color changes from orange-red to green readily observed by the naked eye. The as-prepared fluorescence sensor obtained high sensitivity with a low detection limit of 0.14 μM within 5 min, and distinguished recognition selectivity for 2,4-D over its analogs. Moreover, the sensor was successfully applied to determine 2,4-D in real water samples, and high recoveries at three spiking levels of 2,4-D ranged from 95.0% to 110.1% with precisions below 4.5%. The simple, rapid and reliable visual sensing strategy would not only provide potential applications for high selective ultratrace analysis of complicated matrices, but also greatly enrich the research connotations of molecularly imprinted sensors.

We propose a novel molecular imprinting fluorescence nanosensor via a facile surface imprinting polymerization one-pot synthesis strategy for highly selective and sensitive recognition and detection of 4-nitrophenol (4-NP) on the basis of electron transfer induced fluorescence quenching mechanism. By combining the high selectivity of molecularly imprinted polymers (MIPs) and the strong fluorescence property of quantum dots (QDs), the QD@MIPs nanosensor was demonstrated highly selective and sensitive towards 4-NP, with satisfactory rapidity, accuracy, reliability and practicality. This sensing platform is readily constructed in solution without any other labeling or modification steps, and demonstrated remarkable advantages such as simplicity, rapidity and universality, high selectivity and sensitivity, and good reliability and practicability. This work focuses on the microanalysis of trace 4-NP in complicated environmental water samples by using a kind of new high-effective nanoscale sensing material. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59