Preparation Of Carbon Quantum Dots And Their Application In Detecting Metal Ions And Degrading Methyl Violet

Due to its excellent biocompatibility,fluorescence stability,low toxicity,easier preparation,surface functionalization,and easier large-scale synthesis,carbon quantum dots have a broader application prospect in the environment.This article investigates the physical,chemical,and optical properties of carbon quantum dots prepared using low eutectic solvents and biomass,and explores their applications in heavy metal ion detection and photocatalytic degradation of organic pollutant methyl violet.1)This study uses a deep eutectic solvent as the carbon source and utilizes a hydrothermal synthesis method to prepare carbon quantum dots with specific metal ion detection performance.Carbon quantum dots were prepared using acetamide-glycolic acid DES and acetamide-citrate DES as carbon sources for specific detection of Pb²⁺and Cu²⁺,respectively.The fluorescence quantum yield of acetamide-glycolic acid CQDs is 20.56%,and the fluorescence quenching rate of Pb²⁺is 72.65%.Within the corresponding concentration range,the detection limit of Pb²⁺can be as low as 500 nmol·L^-1,which can completely realize the trace detection of Pb²⁺;The fluorescence quantum yield of acetamide citric acid CQDs is 18.47%,and the fluorescence quenching rate of Cu²⁺is65.46%.Within the corresponding concentration range,the detection limit of Cu²⁺can be as low as 27.5 nmol·L^-1,which can completely realize the trace detection of Cu²⁺.2)Preparation of biomass carbon quantum dots using biomass as carbon source.Veronica persica Poir flower petals were collected for pretreatment as the carbon source.Hydrothermal synthesis of Veronica persica Poir carbon quantum dots（VP-CQDs）based on biomass material was examined for their optical properties.The fluorescence quantum yield of VP-CQDs was 13.68%,which is low compared to that of deep eutectic solvent carbon quantum dots.The degradation rate was as high as 98.08%after 15 h of simulated light exposure,and the best photocatalytic degradation of methyl violet by VP-CQDs was78.92%at a methyl violet concentration of 10μmol·L^-1.This carbon quantum dot has strong degradability and specific responsiveness to methyl violet.3)Combining the advantages of biomass carbon quantum dots,we explored the identification of suitable biomass carbon source materials to prepare carbon quantum dot materials that can specifically respond to metal lead ions,and also combined with the excellent fluorescence performance of acetamide-ethanolic acid DES as a modification modifier to improve the fluorescence performance of biomass carbon quantum dots.The DES wrapped around the surface of biomass carbon quantum dots can enhance the fluorescence performance advantage of biomass carbon quantum dots.Using walnut green bark as the carbon source and acetamide-ethanolic acid DES as the modifying modifier,a one-step hydrothermal synthesis was designed to cover the amide colour-emitting group in DES onto the surface of biomass carbon quantum dots by covalent coupling,and the two formed a fluorescence energy resonance effect to enhance the fluorescence performance of carbon quantum dots.The N-CQDs in this work overcome the defects of biomass W-CQDs.The fluorescence quantum efficiency was increased from 12.5%to 32.5%.The linear detection limit for Pb²⁺was 1.55 n M in the corresponding concentration range.trace detection of Pb²⁺in the aqueous environment could be met with a 97%recycling rate.The above data confirm that the selected DES is effective in modifying the biomass carbon quantum dots,and a method has been developed to effectively design the carbon quantum dots to improve the sensitivity of Pb²⁺trace detection,which is expected to be applied to the detection of metal ions in the field of environmental monitoring.