Preparation And Performance Research Of Nitrogen-doped Carbon Quantum Dot Molecularly Imprinted Fluorescence Sensor

With the rapid development of society,the phenomenon of drug residues in people’s living environment has become more and more serious.Excessive drug residues in the environment will eventually be transferred to humans through the food chain.When the drug residues in the human body exceeds a certain standard,it will have many adverse effects on human health.Therefore,it is very important to find a simple,fast and efficient method for detecting drug residues in the environment.The fluorescence analysis method established by using quantum dots as fluorescent materials is widely used because of its ability to efficiently detect targets.Molecular imprinting technology is a synthetic technology for the purpose of synthesizing molecularly imprinted polymers with specific recognition sites,and is widely used in the specific recognition and detection of targets.Molecularly imprinted polymers have good selectivity,stability and wide applicability.In order to improve the selectivity of the fluorescence analysis method,the fluorescence analysis method and the molecular imprinting technology are combined to prepare a molecularly imprinted fluorescent sensor with superior optical performance and high selective recognition ability.Because of its many advantages,it has gradually become the object of attention of many scientific research scholars.Quantum dots are a kind of fluorescent materials with good fluorescence performance,strong light stability and easy surface modification.Therefore,quantum dots have broad application prospects.In this paper,non-toxic,non-polluting and high fluorescence intensity water phase nitrogen-doped carbon quantum dots（N-CDs）are used as the fluorescent carrier.The molecular imprinting technique was combined with the reverse microemulsion method,the sol-gel method,the precipitation polymerization method,and the ratio fluorescence analysis technique to prepare silicon-based,mesoporous and ratio type molecular imprinting fluorescence sensors.And respectively apply them to the detection of actual samples.The main research contents are as follows:1.Preparation of N-CDs molecularly imprinted fluorescence sensor and its selective recognition of aspirin performance.N-CDs is used as the fluorescent carrier,aspirin is used as the template molecule,APTES is used as the functional monomer,and TEOS is used as the crosslinking agent.N-CDs molecularly imprinted fluorescent sensor was prepared by the inverse microemulsion method.And it has been successfully applied to the detection of aspirin in human saliva and urine samples.The results showed that the best p H of the solution was 6.0,the best detection time was 1.0 min,the detection linear range was0-50μmol·L^-1,and the detection limit was 0.11μmol·L^-1.2.The preparation of N-CDs mesoporous molecularly imprinted fluorescence sensor and its selective recognition of oxytetracycline.On the basis of experiment 1,a molecularly imprinted mesoporous silica fluorescence sensor was prepared,and the detection time was increased from 1.0 min to 0.5 min,which improved the detection rate.N-CDs were used as the fluorescent carrier,oxytetracycline as the template molecule,APTES as the functional monomer,CTAB as the pore-forming agent,and TEOS as the cross-linking agent.N-CDs mesoporous molecularly imprinted fluorescence sensor was prepared by the sol-gel method and applied to the detection of residual oxytetracycline in milk and honey samples.The results showed that the best p H of the solution was 6.0,the best detection time was 0.5 min,the detection linear range was 0-100μmol·L^-1,and the detection limit was 0.035μmol·L^-1.3.The preparation of a ratio-based molecularly imprinted fluorescence sensor based on dual-emission quantum dots and its performance in selective recognition and visual detection of tetracycline.On the basis of experiment 1,a molecularly imprinted ratio fluorescence sensor was prepared,which realized the visual detection of the target.Use TGA modified cadmium telluride quantum dots as the reference signal of the ratio fluorescence sensor,N-CDs as the response signal of the ratio fluorescence sensor,tetracycline as the template molecule,AM as the functional monomer,and EGDMA is used as a crosslinking agent,and AIBN is used as an initiator.The nitrogen-doped carbon quantum dot ratio molecularly imprinted fluorescence sensor was prepared by precipitation polymerization,and it was successfully used for the specific identification and visual detection of tetracycline in milk and egg samples.The results showed that the best p H of the solution was 7.0,the best detection time was 1.0 min,the detection concentration range was 0-140μmol·L^-1,and the detection limit was0.137μmol·L^-1.