Study On The Synthesis Of Biomass-based Carbon Quantum Dots Fluorescent Probes And Application In Small Molecule Detection

Small molecular substances such as uric acid,folic acid and ascorbic acid play important roles in the metabolism of the body.Levels in the normal range are good for normal activity,but too high or too low can cause a series of problems,such as gout,anemia and scurvy.The rapid quantitative detection of small molecules can help people to judge the state of the body.Therefore,the detection of small molecules is very important.Because of its simple equipment,convenient operation and rapid analysis,fluorescence analysis method has attracted more and more attention.In this paper,carbon quantum dots were prepared by using green and environmentally friendly biomass as the main carbon source,and the prepared carbon quantum dots were characterized to study their morphological structure,physical and chemical properties and optical properties.In addition,the as-prepared carbon quantum dots were used as fluorescent probes to achieve rapid detection of small molecular substances including uric acid,folic acid and ascorbic acid.The main research contents of this thesis are as follows:Part 1 Synthesis of pork-based carbon quantum dots and application in uric acid detectionPork-based carbon quantum dots with good stability,water solubility and optical properties were prepared through a simple one-step hydrothermal synthesis method using pork as the main carbon source.Various characterization techniques were used to characterize the morphological structure,element composition and optical properties of the prepared carbon quantum dots.The characterization results showed that the surface of carbon quantum dots is rich in hydrophilic groups such as hydroxyl,amino and carboxyl groups,which also provides a basis for its good water solubility.In addition,studies have shown that the carbon quantum dots have a significant response to uric acid,and uric acid can quench the fluorescence.The mechanism of fluorescence quenching was investigated.It is speculated that the mechanism is static quenching.Under the optimized conditions,the fluorescence quenching degree of carbon quantum dots was in a good linear relationship with the uric acid concentration within a certain range,and the detection limit is 0.05?M.The established method was applied to the detection of uric acid in serum and urine samples,and the results were compared with those obtained by high performance liquid chromatography.The results obtained from the two methods were similar,and the method was feasible.Part 2 Microwave-assisted synthesis of kelp-based nitrogen-doped carbon quantum dots and application in folic acid detectionA method for rapid detection of folic acid by carbon quantum dots that prepared by microwave-assisted synthesis was established.The kelp-based nitrogen-doped carbon quantum dots with higher fluorescence intensity were prepared by microwave method using biomass kelp as the main carbon source and ethylenediamine as the nitrogen dopant.The morphological structure and optical properties of the prepared carbon quantum dots were studied by a series of characterizations and the fluorescence yield was calculated to be 23.5%with quinine sulfate as the standard substance.The results showed that folic acid can quench the fluorescence of kelp-based nitrogen-doped carbon quantum dots.The complex was formed by hydrogen bonding between the groups such as-COOH,-NH₂,-OH on the surface of kelp-based nitrogen-doped carbon quantum dots and-COOH,-NH₂,-OH in folic acid molecules and static quenching occurred.The as-prepared exhibit higher sensitivity and better selectivity for folic acid.Therefore,it can be used as a fluorescent probe for detection of folic acid.Under the optimal conditions,the fluorescence quenching degree of carbon quantum dots is linear with the folic acid concentration?0.02-65?M?.The linear regression equation was F/F₀=-0.0082C+0.9327?r²=0.9917?,and the detection limit was 0.01?M.The proposed method was applied to the detection of folic acid in serum samples,and a rapid method for detecting folic acid was established.Part 3 Synthesis of yam-based nitrogen-doped carbon quantum dots and application in detection of ascorbic acidAn"off-on"fluorescent probe based on the principle of redox was constructed and used for the determination of ascorbic acid in fruits.The yam-based nitrogen-doped carbon quantum dots were prepared using yam as the main carbon source and ethylenediamine as the nitrogen dopant.The prepared carbon quantum dots were characterized by a series of characterization techniques.The results showed that the prepared carbon quantum dots were spherical and uniformly dispersed with each other,with a diameter of about 3 nm.The surface was rich in hydrophilic functional groups such as amino group,hydroxyl group and carboxyl group.The preparation of carbon quantum dots have good optical performance,and the fluorescence can effectively quenched by chromium???,but the fluorescence of the system is recovered after the addition of ascorbic acid.Therefore,a fluorescent probe based on the redox principle was constructed for rapid detection of ascorbic acid.Under the optimized conditions,the fluorescence recovery degree of carbon quantum dots showed a linear relationship with the concentration of ascorbic acid,the correlation coefficient was 0.9939,and the detection limit was 1.2?M.The propoesd fluorescent probe was used for the determination of ascorbic acid in fruits,and the results were similar to those obtained by high performance liquid chromatography,which showed the method has good application prospects.