Preparation And Application Of Carbon Dot-based Ion Imprinting Fluorescence Sensor

The development of technology has brought convenience to people but also brought serious safety problems.Ecological safety,drinking water safety,and human health problems caused by heavy metal pollution are becoming increasingly important.Heavy metals are enriching and once they exceed the maximum limit that the human body can tolerate,they may cause serious damage to it.Therefore,the treatment and rapid detection of heavy metal ions in complex water bodies are particularly important.The ion imprinting technique has received increasing attention in the field of heavy metal treatment and fluorescence sensing because of its specific recognition of metal ions.In this thesis,the preparation of copper ion-imprinted（Cu-IIP）polymer and fluorescent carbon quantum dots（CQDs）were investigated for the adsorption performance of Cu-IIP and fluorescence performance of CQDs,respectively.Based on this,ion-imprinted fluorescent sensors（CQDs@Cu-IIP）were prepared by compounding carbon quantum dots into copper ion-imprinted polymers by surface imprinting technique.Besides,a portable fluorescent hydrogel（CQDs HG）was prepared by cross-linking carbon quantum dots into the hydrogel for rapid metal ion detection.The details of the study are as follows.（1）Cu（II）ion-imprinted polymers were successfully prepared by conventional heating and freeze-drying methods using Cu²⁺,APTES,TEOS,and ammonia as template ions,functional monomers,cross-linkers,and initiators,respectively,with water as solvent throughout.The effects of the preparation conditions on the adsorption properties of the polymers were investigated,and the polymers were characterized by FT-IR,EDS,SEM,AFM,and BET techniques.The results confirmed that the products obtained by freeze-drying treatment had better morphology and the adsorption capacity could be increased by 31.05%compared with the conventional thermal drying method.The maximum adsorption capacity of the polymer for copper ions was 56.68 mg/g under the optimized test conditions,and the spiked recoveries in the actual water samples were 96.1%～102.6%.（2）CA was used as the carbon source to prepare CQDs with blue fluorescence and quantum yield of 79%by hydrothermal method,and the prepared fluorescent carbon quantum dots were grafted onto the surface of SBA-15 mesoporous molecular sieve by amination reaction.Then,the ion-imprinted fluorescent sensor CQDs@Cu-IIP was prepared by surface imprinting technique using the aminated SBA-15 as the substrate material,Cu²⁺as the template,TEOS as the cross-linking agent,and APTES as the functional monomer.after optimizing the detection conditions,the fluorescence intensity of the sensor showed good linearity for the Cu²⁺concentration（in the range of 0.25-2 mg/L and 3-10 mg/L,respectively）CQDs@Cu-IIP was applied to the detection of trace Cu²⁺in tap water with the spiked recoveries of 99.29%～105.42%.（3）Carbon quantum dots with good optical properties were synthesized in one step by microwave hydrothermal method using CA and EDA as raw materials and loaded into hydrogels by sol-gel technique to successfully prepare portable fluorescent hydrogels.The morphology,chemical composition,and fluorescence properties of CQDs were characterized by TEM,XPS,fluorescence spectroscopy,and other analytical techniques.The effects of initial concentration and adsorption time on the adsorption..properties of CQDs HG and HG and the fluorescence burst effect of different metal ions on the hydrogels at 370 nm were investigated.The results showed that the relative fluorescence quantum yields of the prepared CQDs were as high as94.1%.The fluorescent hydrogels could be effectively burst by Fe³⁺with the maximum adsorption amount of 39.14 mg/g for Fe³⁺,and the adsorption processes were by the quasi-secondary kinetic model and Freundlich model,respectively.