The Preparation Of Carbon Quantum Dots Based On Peony Seed Pods And Their Detection Of Iron Ions In Water Environment

With the development of society,the volume of waste is becoming larger and larger,which has become a key factor of environmental pollution.Planting oil peony has become one of the important industries in Shaanxi province.In order to maintain the oil nutritious,the seeds must be picked with the peony seed pods.When the oil is refined,peony seed pods become waste or used as firewood.Therefore,it is of great significance to recycle the peony seed pods.In this paper,three kinds of carbon quantum dots based on peony seed pods were prepared and synthesized for their morphology,structure,composition and properties.The recognition mechanism of carbon quantum dots to iron ions was studied in water environment.and successfully used in actual water samples.The specific contents are as follows:Carbon quantum dots?CQDs?were synthesized by one-step hydrothermal method with peony seed pods as carbon source.The morphological,structural and properties were discussed by TEM,FT-IR,UV-vis and FL.CQDs is a spherical material with a size of about 2.1-4.3 nm.The surface of CQDs has a large number of oxygen-containing groups and hydroxyl groups.Fe³⁺had quenching effect on fluorescence intensity of CQDs.The linear regression equation was obtained:y=-0.01145x+0.95452,the linear coefficient:R²=0.9912,and the detection limit was 0.083?M.The method has been successfully applied to the determination of iron ions in water samples.N,S-doped carbon quantum dots?N,S-CQDs?were synthesized by one-step hydrothermal method with peony seed pods and thiourea as carbon,nitrogen and sulfur source.The morphological,structural and properties were discussed by TEM,FT-IR,UV-vis and FL.Fe³⁺had quenching effect on fluorescence intensity of N,S-CQDs.The linear regression equation was obtained:y=-0.01712x+0.97075,the linear coefficient:R2=0.9934,and the detection limit was 0.050?M.By comparison,the sensitivity and selectivity of N,S-CQDs were significantly improved.Carbon quantum dots with amino and carboxy groups?CNQDs?were synthesized by one-step hydrothermal method with peony seed pods and chitosan as precursors.The morphological,structural and properties were discussed by TEM,FT-IR,UV-vis,FL.Fe³⁺has quenching effect on the fluorescence intensity of CNQDs,and the linear regression equation is obtained:y=-0.02113x+0.99801,the linear coefficient R²=0.9948,and the detection limit is 0.017?M.By contrast,the detection limit of CNQDs has been improved,which may be because the surface defect sites of modified quantum dots have strong binding ability with iron ions,and when CNQDs are excited,the electrons transfer,resulting in fluorescence quenching.