Preparation And Application Of Near-Infrared Ratiometric Fluorescence Sensor Based On Metal Organic Framework

Ratiometric fluorescence analysis is a detection method with fast response speed and high sensitivity.Compared with the single emission fluorescence,ratiometric fluorescence greatly improves the accuracy of detection results through the self-calibration system of multiple emissions,and has a wide application prospect in the fields of nanoprobes and sensors.However,the fluorescence analysis under visible light is limited by the interference of some self-fluorescence substrates and background fluorescence of environment.Near-infrared fluorescence（650-900 nm）overcomes the interference of light scattering and biomass self-fluorescence and has deep tissue penetration,making it particularly attractive in the field of biosensors.In addition,parallel multichannel fluorescence analysis greatly improves the reliability of the analysis results.Molecular imprinting technology is a kind of technology that can synthesize nanomaterials with specific recognition of target analytes.The technology has been widely used in the fields of biomolecular recognition,chromatographic separation,solid phase extraction,drug delivery,analog enzyme catalysis and biological/chemical sensing.Therefore,the combination of near-infrared ratiometric fluorescence analysis and molecular imprinting technology has broad development prospects in the field of biological/chemical fluorescence sensing.In this paper,multiple functional emission CDs and Cd Te QDs were used as fluorescence sources to construct ratiometric fluorescence emission system.Combined with signal amplification effect of metal organic framework,near-infrared ratiometric fluorescence imprinting sensor was prepared by molecular imprinting technology.The main research contents are as follows:1.The rapid and simple synthesis of highly efficient multi-emission luminescent metal-organic frameworks（LMOFs）with down/up-conversion fluorescence properties becomes critical in potential optical sensing.Here,we present a luminescent dual-ligand co-assisted strategy to one-pot prepare LMOFs for multiplex fluorescence sensing using carbon dots（CDs）and 2-methylimidazole（2-MIM）as dual-ligand to induce Zn²⁺on zeolitic imidazolate framework-8 surface（CDs/MIM-Zn）.The CDs/MIM-Zn exhibited efficient fluorescence-enhanced dual channels triple-emission with Stokes and anti-Stokes type excitation profiles.With the assistance of Stokes and anti-Stokes type optical property of CDs and the intrinsic porosity of MOFs structure,a rapid and sensitive dual-channel detection excited at 370 nm and 790 nm was performed to fluorescence turn off-on detect metal ions and reduced glutathione in real blood samples with the satisfactory recoveries of 98.3-106.4%.The dual channels triple-emission strategy ensured multiplex detection of more analytes in parallel.2.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（Cd Te）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 Cd Te is less interference caused by auto-fluorescence of sample.The ratiometric fluorescence imprinted sensor exhibited dual response for 4-NP at 420nm and 703 nm and a wide concentration response range.Moreover,a good linear response was existed in the two concentration ranges of 0.1 p M-3.0 p M and 0.05μM-30μM with the detection limit of 0.08 p M and 0.05μΜ,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.3.Establishment of green fluorescence sensing system for anti-interference,highly sensitive and selective visual detection of trace thiamphenicol（TAP）in food is of great significance to food safety and human health risk assessment.A simple and rapid one-pot strategy was developed to synthesize a down/up-conversion dual-excitation multi-emission fluorescence imprinted sensor for dual-channel detection of TAP.In this strategy,green biomass carbon dots（b CDs）and abiotic carbon dots（a CDs）with stokes and anti-stokes type emission were anchored respectively to Si O₂ nanospheres and metal-organic frameworks（MOFs）surface to obtain stability-improved and response-enhanced fluorescence signals.Notably,MOFs in situ incorporation fluorescence imprinted sensor guided the coordination induced emission of a CDs and signal-amplification effect of fluorescence sensing.Under dual-excitation（370 nm and780 nm）,the sensor exhibited a dual-channel response toward TAP with two-part linear ranges of 5.0 n M-6.0μM and 6.0μM-26μM with the detection limits of 0.9 n M for the up-channel.Significantly,the fluorescence color changes from blue to purple to red can be seen with the naked eye.The results from the dual-channel TAP assay in actual samples indicated that the green sensor provided a highly sensitive,selective,anti-interference and multiplexed visual detection of TAP in complex sample.