Preparation Of Dopamine Functionalized Carbon Dots And Their Detection Of Fe³⁺ And Fe²⁺

Carbon dots(CDs)are a new type of quasi spherical carbon based zero dimensional nanomaterials with a diameter of less than 10 nm,which have unique optical properties.Compared with traditional semiconductor quantum dots and organic dyes,carbon dots have excellent properties such as chemical inertness,high solubility,easy modification,high resistance to light bleaching,biocompatibility and low toxicity.These excellent properties make carbon dots have broad application prospects in the fields of analysis and detection,biological imaging,biosensor,drug delivery and catalysis.In this paper,the preparation methods,chemical modification,fluorescence mechanism,optical properties and applications of carbon dots were reviewed in detail.The novel functionalized carbon dots were prepared.Based on the novel functionalized carbon dots,fluorescent probes for the detection of Fe³⁺and Fe²⁺were constructed and applied to the detection of Fe³⁺and Fe²⁺in actual water samples.The blue luminescent sulfur nitrogen Co-doped carbon dots(S,N-CDs)were prepared by a simple one-step hydrothermal method using citric acid and thiourea as precursors.Then dopamine monomer was covalently bound to the surface of S,N-CDs by EDC/NHS coupling reaction to obtain dopamine functionalized sulfur nitrogen Co-doped carbon dots(DA-S,N-CDs).By optimizing the experimental conditions,the optimal conditions for the preparation of S,N-CDs and DA-S,N-CDs with excellent fluorescence properties were determined.S,N-CDs and DA-S,N-CDs were characterized by transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),ultraviolet visible absorption spectroscopy(UV-Vis),Fourier transform infrared spectroscopy(FTIR)and fluorescence.The results show that:S,N-CDs and DA-S,N-CDs both have the property of depending on the excitation wavelength;S,N-CDs and DA-S,N-CDs are spherical,with average particle size of about 15nm and 18nm;there are a large number of amino and oxygen-containing functional groups on the surface of S,N-CDs and DA-S,N-CDs;DA-S,N-CDs show good photostability in a wide range of p H,high ionic strength and UV lamp irradiation.Based on the quenching principle,the dopamine catechol residues on the surface of DA-S,N-CDs can specifically interact with Fe³⁺or Fe²⁺to form a stable non-fluorescent complex,which leads to the decrease of fluorescence intensity of DA-S,N-CDs,and a fluorescence sensor system that can simply and quickly detect Fe³⁺and Fe²⁺in the water is constructed.Through the optimization of the factors that affect the detection effect in the detection process,the best detection conditions are determined.Selective and anti-interference experiments were carried out on the detection system.The experimental results showed that other metal cations in the solution had little effect on the detection of Fe³⁺and Fe²⁺.The sensitivity analysis of the constructed fluorescent probes showed that under the optimal detection conditions,the relative fluorescence intensity of DA-S,N-CDs showed good linear correlation with Fe³⁺and Fe²⁺in the range of 5-200?M and 5-300?M(R²=0.9963 for Fe³⁺,R²=0.9985 for Fe²⁺),and the detection limits were 2.86?M and 2.06?M,respectively.Finally,DA-S,N-CDs were used to detect Fe³⁺and Fe²⁺in lake water and tap water with good detection effect.