Synthesis And Modification Of Biomass Fluorescent Carbon Dots And Its Application In Blood Detection

Blood is the most important component in the human body,in which a lot of human health information is stored.Therefore,blood tests are often used for early diagnosis of diseases.Carbon quantum dots（CQDs）are a new type of zero-dimensional carbon nanomaterials with particle size less than 10 nm developed in recent years.Due to its stable and adjustable fluorescence characteristics,low toxicity,good biocompatibility,easy large-scale synthesis as well as functional modification,CQDs can be used as fluorescent probe with very important application value in the field of life sciences such as blood testing.In recent years,the development and utilization of green natural biomass raw materials as the initial carbon source for the preparation of carbon dots can not only effectively reduce the cost of raw materials,but also convert low-value waste resources into high-value carbon nanomaterials,thereby improving the economic value of the raw materials.At the same time,the prepared"green"carbon dots also have excellent optical performance and good biocompatibility which the traditional semiconductor quantum dots do not have,so the biomass carbon dots are favored by more and more researchers.In this thesis,different natural biological raw materials were used as carbon source precursors,and biomass carbon dots with excellent performance were prepared by one-step hydrothermal method.In addition,the synthesized fluorescent carbon dots were doped with elements to improve their fluorescence performance and sensing ability.Finally,two biomass carbon dots were used as fluorescence probes for the high-sensitivity detection of Fe³⁺and cysteine,respectively.The specific research contents are as follows:1.Nitrogen-doped carbon dots（NCQDs）with strong blue fluorescence were synthesized by one-step hydrothermal method using abundant bamboo stems as carbon source and ethylenediamine as nitrogen dopant,with the quantum yield up to 20.02%.The optical,physical and chemical properties of the prepared NCQDs were characterized by TEM,XRD,XPS,FT-IR,UV-vis and FL,which was confirmed that NCQDs have good dispersibility,water solubility,photoluminescence property depending on the excitation wavelength,and excellent stability to extreme pH and high ionic strength.The strong fluorescence quenching of NCQDs caused by the presence of Fe³⁺was observed,which enabled the selective and sensitive detection of Fe³⁺with a linear detection range of 0.01-10μM（R²=0.9910）and the detection limit as low as 0.486μM.The method was applied to the determination of Fe³⁺in human serum samples and the results showed that the recovery as well as relative sandard deviation（RSD）were in the range of 85.90%-112.60%and 0.95%-2.92%,respectively.2.Cobalt-doped carbon dots（Co-CDs）with blue fluorescence were synthesized by hydrothermal method using food waste okara as the carbon as well as nitrogen source,and using cobalt chloride as the modification reagent.The average particle size of Co-CDs was 2.75 nm,and the quantum yield（QY）was about 7.6%.The structural properties and optical properties of Co-CDs were analyzed by various characterization methods.The results showed that the obtained Co-CDs had good water solubility,excitation wavelength dependence,pH stability,and other properties.Based on the fact that the addition of Cys can specifically inhibit the fluorescence of Co-CDs,the development of a sensitivity detection probe for Cys was realized.The newly constructed fluorescent probe showed good linear correlation with Cys in the range of 0.1-10μM,and the detection limit was 0.653μM.Moreovere,It has been successfully applied to the detection of Cys in human serum samples with the advantages of high selectivity,high sensitivity,convenience,rapidness,low cost,etc.,and realized comprehensive utilization of bean dregs,showing great economic and environmental benefits.