A dual-response ratiometric fluorescence imprinted sensor based on metal-organic frameworks for ultrasensitive visual detection of 4-nitrophenol in environments

A dual-response ratiometric fluorescence imprinted sensor based on visible/near-infrared emission was established for ultrasensitive, selective and visual detection 4-nitrophenol (4-NP). The molecularly imprinted polymer was incorporated in the ratiometric sensing system consisting of visible emission carbon dots@zeolitic imidazolate framework-8 (CDs@ZIF-8) and near-infrared emission cadmium telluride (CdTe) quantum dots. The CDs@ZIF-8 enhanced the emission of CDs and the fluorescence sensing performance. Compared to short wavelength of fluorophore, the near-infrared emission CdTe is less interference caused by auto-fluorescence of sample. The ratiometric fluorescence imprinted sensor exhibited dual response for 4-NP at 420 nm and 703 nm and a wide concentration response range. Moreover, a good linear response was existed in the two concentration ranges of 0.1 pM-3.0 pM and 0.05 μM-30 μM with the detection limit of 0.08 pM and 0.05 μΜ, respectively. Significantly, the fluorescence color changes can be observed from purple to pink to red with the naked eye. The fluorescence quenching mechanism of the ratimetric fluorescence imprinted sensor was discussed in detail. The ratiometric fluorescence imprinted sensor was used to detect 4-NP in various real samples with satisfactory recoveries of 97.5-106.3%, which provided an interesting avenue for the rapid detection of pollutant with high sensitivity, high selectivity and visualization in real environment.