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

Carbon-based materials play an indispensable role of the development of human society,due to their low price,non-toxic,harmless,stable chemical properties and other advantages,they have extensive applications in the fields of energy,industry,environment,biology and optoelectronics.Among carbon-based materials,carbon nano-dots have attracted the attention of researchers,due to their specific photoluminescence properties.Carbon nano-dots not only have the low toxicity of carbon-based materials,but also have good photoluminescence properties,chemical stability and good biocompatibility,it is expected to completely replace traditional quantum dots,organic fluorescent dyes,and has more in-depth applications in bioimaging and sensing detection.In addition,due to the wide range of raw materials and excellent optical properties of carbon nano-dots,it has been applied in fields such as optoelectronic devices.In terms of preparation,there are countless methods for the synthesis of carbon nano-dots,but the preparation methods are cumbersome,and large-scale synthesis is still a problem that limits the wide application of carbon nano-dots.Therefore,looking for carbon-rich,cheap and easily available raw materials and clean and pollution-free preparation techniques have become the focus of large-scale preparation of carbon nano-dots.Based on this,we use corn stalks as raw materials to prepare blue fluorescent carbon nano-dots through the near-critical water liquefaction technology,furthermore,the solid residue was treated with alkaline oxidation treatment to prepare yellow-green fluorescent carbon nano-dots,and the morphology,structure and fluorescence properties of the prepared carbon nano-dots were tested,and related applications were explored.The research content is as follows:1.In this experiment,corn stalk shells were used as the initial carbon source,and the near-critical water liquefaction technology was used to directly obtain the blue fluorescent carbon nano-dots(b-CNDs)solution.The quantum yield of the carbon nano-dots was 16%,and it appeared blue fluorescence under 365 nm excitation.We use ultraviolet-visible light absorption spectroscopy(UV-Vis),fluorescence spectroscopy(PL),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and infrared spectroscopy(FTIR)to characterize the synthesized carbon nano-dots,and the morphology,structure and optical properties of b-CNDs were analyzed.Based on the analysis results,the performance of b-CNDs was discussed.2.The prepared b-CNDs are used in substance detection applications.The fluorescence of b-CNDs can be effectively quenched by the organic dye Alizarin Red S(ARS).Based on this,a fluorescent probe for detecting ARS is constructed,and the detection range is 10-150?mol/L,the detection limit is 2.65?mol/L.In addition,this experiment detected the cytotoxicity of b-CNDs.Lung cancer cells(A549 cells)were used to detect the toxicity of b-CNDs by MTT method.The test results showed that b-CNDs had low toxicity and good biocompatibility.In addition,this experiment carried out a cell imaging experiment.The cells were cultured in a medium containing b-CNDs.The results of cell imaging were photographed by a confocal microscope.It can be observed that b-CNDs appear blue in the cells.3.In this experiment,the solid coke remaining from the liquefaction of corn stalks was used as the initial carbon source,and green carbon nano-dots(g-CNDs)were prepared by alkali treatment and hydrogen peroxide oxidation.The quantum yield of carbon quantum dots prepared by this method was 44%.Under 380nm excitation conditions,g-CNDs emit green fluorescence.We use ultraviolet-visible light absorption spectroscopy(UV-Vis),fluorescence spectroscopy(PL),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and infrared spectroscopy(FTIR)to characterize the synthesized carbon nano-dots,and the structure and optical properties of g-CNDs were analyzed and discussed.In addition,based on the fluorescence quenching response of g-CNDs to metal ions,it was used for the detection of Cu²⁺and Fe³⁺,and g-CNDs and polyvinyl alcohol were mixed to prepare a luminescent film.The luminescence properties of the film were explored.