Preparation And Application Of Carbon Quantum Dots From Authentic Medicinal Materials In Shanxi

Authentic Chinese medicine is synonymous with high-quality Chinese medicine,which refers to the traditional Chinese medicine with good quality,remarkable curative effect and growing in the specific ecological environment and natural conditions.Carbon quantum dots is a carbon-based zero-dimensional materials with excellent optical stability,good water solubility,low toxicity to organisms,environmental friendliness,wide sources of raw materials,low cost and good biocompatibility.In organisms,free radicals are usually produced through a series of enzymatic or non-enzymatic oxidation reactions.Excessive and overactive free radicals seize electrons in the human body are considered to be the root cause of many diseases and pose a huge threat to human health.Picric acid has hazards such as contact dermatitis,conjunctivitis,bronchitis and chronic poisoning to human health.As a heavy metal pollutant,Pb²⁺has a strong effect on the ecological environment,and also has a serious impact on human health.In this paper,carbon quantum dots were prepared from the authentic Chinese medicine in Shanxi Province and applied to the scavenging of free radicals and the detection of Pb²⁺,which has certain significance for human health and the ecological environment.Chapter 1:A brief review of authentic Chinese medicine in Shanxi Province,free radicals and carbon quantum dots.And the background of the topic and the main research contents are summarized.Chapter 2:Using the authentic Chinese medicine Codonopsis pilosula,Astragalus,Forsythia suspensa and Polygala tenuifolia willd as raw materials,carbon quantum dots with blue-green fluorescence were synthesized by one-step hydrothermal method.The morphology,structure and spectral behavior of carbon quantum dots were studied by transmission electron microscopy,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,UV-vis spectra and fluorescence spectra.Ascorbic acid solution was used as the reference substance to explore their scavenging efficiency of hydroxyl radical.The results showed that the carbon quantum dots prepared by traditional Chinese medicine can scavenge hydroxyl radical in a certain range,and there is a good linear relationship between the scavenging rate of hydroxyl radical and the concentration of carbon quantum dots.The hydroxyl radical scavenging efficiencies of carbon quantum dots prepared from Codonopsis pilosula,Astragalus,Forsythia suspensa and Polygala tenuifolia Willd were82.94%,77.36%,77.02%and 70.87%,and the EC₅₀values were 27.23μg/m L,44.23μg/m L,58.24μg/m L and 52.42μg/m L,respectively.The carbon quantum dots with Codonopsis pilosula as material has the highest scavenging efficiency for hydroxyl radical,and the EC₅₀value is the lowest,which is equivalent to ascorbic acid(the scavenging rate is 95.60%,EC₅₀value is 36.57μg/m L).Through further exploration,it was found that the scavenging rate of hydroxyl radical by the carbon quantum dots made from Atractylenolide III,the main component of Codonopsis pilosula,was 66.37%.Therefore,it is speculated that the Atractylenolide III in Codonopsis pilosula played a major role in the scavenging of hydroxyl radical.Chapter 3:Using the traditional Chinese medicine Codonopsis pilosula as the raw material,the blue fluorescent carbon quantum dots（λex=340nm,λem=440nm）was successfully prepared by one-step hydrothermal method.It is a kind of small size nano materials with excellent optical properties,which has the advantages of environmental-friendly,low environmental pollution and low toxicity.Based on the internal filtration effect,picric acid can selectively quench the fluorescence of carbon quantum dots.The fluorescence intensity ratio（F₀/F）of carbon quantum dots has a good linear relationship with the concentration of picric acid in the range of 1-155μM and195-279μM,and the corresponding detection limit is 63n M.According to this property of carbon quantum dots,it was applied to the efficient and specific detection of picric acid,and the method was successfully applied to the detection of picric acid in water samples,the corresponding recovery was 98.4-103.8%,and the relative standard deviation was less than 3%（n=5）.Chapter 4:Using Atractylenolide III as raw material,blue fluorescent carbon quantum dots for the detection of picric acid and Pb（Ⅱ）were successfully prepared by one-step hydrothermal method（λex=320nm,λem=450nm）.The quantum yield of the carbon quantum dots was 1.7%.The structure,optical properties and surface morp Hology of the synthesized carbon quantum dots were characterized and observed by Fourier transform infrared spectroscopy,UV-Vis absorption spectroscopy,fluorescence spectroscopy,X-ray p Hotoelectron spectroscopy and transmission electron microscopy.It was found that the carbon quantum dots is spherical,and there are abundant oxygen-containing functional groups on its surface.It has good water solubility.Experiments have found that this carbon quantum dots can be used as a on-off sensor for the detection of picric acid and Pb（Ⅱ）,and the fluorescence intensity can be effectively quenched by picric acid.There is a good linear relationship between the fluorescence intensity ratio（F/F₀）and the concentration of picric acid in the range of 0-410μmol/L,and the corresponding detection limit is 53 n M.The addition of Pb（Ⅱ）will effectively increase the fluorescence intensity of the carbon quantum dots-picric acid.In the range of 0-580μmol/L,the fluorescence intensity ratio（F/F₀）and Pb（Ⅱ）showed a good linear relationship,and the corresponding detection limit was 68 nM.