Rapid Preparation Of Fluorescent Carbon Dots From Herbal Sources And Their Use In The Analysis And Detection Of Pesticide Residues And Metal Ions

As one of the important members of carbon based nano materials,fluorescent carbon dots（CDs）have attracted much attention because of their advantages of easy preparation and functionalization,good water solubility and biocompatibility,low toxicity,high photostability and reactivity.They are widely used in the analysis and detection of chemical substances（such as pesticides,metal ions）and biological small molecules.In this paper,the widely existing,green and economic herbal medicines are used as raw materials.The fluorescent carbon dots are rapidly prepared by hydrothermal method and used for the rapid detection of pesticide residues and metal ions.Its main research contents include:（1）Rapid preparation and characterization of herbaceous CDs.22 kinds of CDs were synthesized by hydrothermal method.After screening,scutellaria baicalensis,phellodendron amurense,paeonia alba and hibiscus bark were finally determined to prepare four kinds of herbal source carbon dots（SB-CD,PA-CD,PL-CD and CP-CD）.The structure and optical properties of the prepared herbal source CDs were detected and analyzed by UV-vis spectroscopy（UV）,fluorescence spectrophotometer（FL）,X-ray diffraction（XRD）and Fourier transform infrared spectroscopy（FTIR）,The results show that the carbon nanotubes of the four grass-based CDs are monodisperse and spherical,the particle size is about 10-100 nm,and the diffraction peak width is about 22°.Then their luminescence characteristics are analyzed.It is found that the type of solvent and sample concentration will have a certain impact on their fluorescence intensity.In the follow-up study,the carbon point can produce different fluorescence signals after interacting with organophosphorus pesticides.In the follow-up study,the detection of organophosphorus pesticides can be realized,so as to establish a targeted fluorescence analysis method for the next experiment.This study is expected to be applied in pesticide detection,metal ion detection and so on.（2）Herbaceous CDs was used for the detection of pesticide residues.Under the optimal conditions,the detection of agricultural residues of grass derived CDs was studied.The screening of solvent,optimization of concentration and dosage were studied to explore the experiment of herbaceous CDs（SB-CD,PA-CD,PL-CD and CP-CD）acting on three pesticides of permethrin,chlorpyrifos and Isoprocarb.The experimental results showed that the four herbaceous CDs quenched three agricultural drugs of permethrin,chlorpyrifos and isoprocarb to a certain extent.Among them,the detection range of herbaceous CDs for permethrin was 0.41-50μM,and the detection limit was 0.01-1.6 n M;The detection range of chlorpyrifos is 0.1-500μM,and the detection limit is 0.13-17.5 n M;The detection range of isoprocarb is 1-1000μM and the detection limit is 2.33-19 n M.The results show that the fluorescence of herbaceous CDs can be quenched by pesticides to a certain extent,and can be used in the actual detection of agricultural residues.（3）Herbaceous CDs is used for the detection of metal ions.In order to sensitively and quickly detect heavy metal ions,the synthesized CDs acts on four kinds of heavy metal ions through hydrothermal synthesis.The results show that the fluorescence intensity of grass source CDs points will be selectively quenched by metal ions.Among them,the fluorescence intensity of Ba²⁺and CDs shows a good linear reaction between 1-10μM,and the fluorescence intensity of Cu²⁺and CDs shows a good linear reaction between 0.5-20μM,The fluorescence intensity of Ni²⁺and CDs shows a good linear reaction between 0.5-20μM,and the fluorescence intensity of Cd²⁺and CDs shows a good linear reaction between 1.0-15.5μM,and their detection limit is in the range of 0.5-1.5μM.The test results show that this method can be well used for the determination of heavy metal ions in actual water quality.In this paper,the widely existing,green and economical herbal medicines were used as raw materials.The fluorescent carbon dots were rapidly prepared by hydrothermal method and used for the rapid detection of pesticide residues and metal ions.However,due to the limited experimental time,the follow-up experiments and related optimization conditions still need to be further studied and discussed.