Study On The Preparation And Application Of Carbon Nano-dots From Chinese Cabbage

As a kind of natural renewable resource,biomass resources have a large amount,rich sources and huge potential.In recent years,its have been paid more and more attention in research.However,many biomass resources cannot be effectively utilized and become waste.Although the hazard is not as great as that of some other types of waste,it can also cause serious health or environmental problems if not handled properly.Carbon dots,as a new type of carbon nanomaterials,have attracted the attention of researchers in recent years due to their excellent stability,good biocompatibility and peculiar optical properties,and can be obtained from a variety of biomass as raw materials.However,the research goals of producing carbon nanomaterials based on biomass are mostly concentrated on plant-derived biomass materials with high lignin,cellulose,and low water content,and there are problems such as complex process flow,cumbersome material pretreatment,and difficulty in large-scale industrial production.Based on this,we used Chinese cabbage as a representative of terrestrial plant-derived biomass with high water content,low lignin and cellulose,and developed a green and simple synthesis route to make Chinese cabbage into carbon dots with high added value.and the full utilization of materials is realized.After that,we developed it as a fluorescent probe and a colorant for bioimaging.The specific research contents are as follows.1.Using Chinese cabbage as a carbon source and water as the solvent,nitrogen self-doped cyan fluorescent carbon dots(CC-CDs)were directly obtained from the liquid phase by near-critical fluid liquefaction technique.Among them,the fluorescence quantum yield of CC-CDs is 13.6%,bright cyan fluorescence is emitted under the optimal excitation 380 nm wavelength excitation,and the strongest emission peak is near 480 nm.In addition,the morphology,structure,composition and optical properties of CC-CDs were tested and characterized,and the results were discussed.Subsequently,based on fluorescence quenching,CC-CDs were developed as sensitive fluorescent probes for detecting trace Fe³⁺ions in the aqueous phase.Among many cations,CC-CDs have strong selectivity and anti-interference ability to Fe³⁺,and there is a good linear relationship between the concentration of Fe³⁺and the fluorescence intensity of CC-CDs aqueous solution in the concentration range of 0-100?M,and the detection limit is 0.42?M.Based on the excitation dependence of CC-CDs,it was developed as a colorant for polychromatic imaging of living cells.Firstly,it was confirmed that CC-CDs had low toxicity to He La cells and good biocompatibility by the MTT method.After that,the multicolor fluorescence imaging of He La cells incubated with CC-CDs was successfully achieved by a laser confocal microscope.The CC-CDs labeled He La cells showed bright blue,green and red fluorescence under the laser excitation of 405nm,488 nm and 543 nm,respectively.2.Using the liquefied solid carbon of Chinese cabbage as carbon source,thiourea as nitrogen source and sulfur source,the yellow fluorescent carbon spot(HC-CDs)co-doped with nitrogen and sulfur was prepared by one-step Na OH/H₂O₂ oxidation.The quantum yield of the prepared HC-CDs is 55.6%.Under the optimal excitation wavelength of 380 nm,HC-CDs emit yellowish fluorescence,and the strongest emission peak is near 500 nm.The morphology,structure,composition and optical properties of HC-CDs were tested and characterized,and the results were discussed.Based on fluorescence quenching,HC-CDs were developed as a sensitive fluorescence probe for the detection of trace methyl orange(MO)in the aqueous phase,and the reason for HC-CDs fluorescence quenching caused by MO was discussed.In the concentration range of 0-100?M,the concentration of MO has a good linear relationship with the fluorescence intensity of HC-CDs aqueous solution,and the limit of detection is 0.92?M.HC-CDs is developed as a sensitive fluorescence probe for detecting trace TC in the aqueous phase,the linear range for TC is 0-70?M and 80-180?M,respectively,and the calculated limit of detection is 2.84?M.