Synthesis Of Fluorescent Carbon Dots And Their Application In Analytical Detection

As a novel carbon nanomaterial,the particle size of carbon dots（CDs）is generally less than 10nm,and the surface is rich in functional groups.Compared with the early organic dyes and semiconductor quantum dots（QD）,CDs have a series of advantages,such as controllable photoluminescence,unique optical,physical and chemical properties,good water solubility,biocompatibility,low toxicity,low preparation cost and so on.With the passage of time,it has been widely used in the fields of biosensor,chemical analysis,photocatalysis,fluorescence imaging and drug delivery.In this paper,CDs with different fluorescence properties were synthesized by simple one-step hydrothermal method using itaconic acid and citric acid as carbon sources,and N-β-（aminoethyl）-γ-aminopropyl methyl dimethoxysilane（KH-602）,urea and cerium nitrate hexahydrate as additives.After comprehensive summary are as follows:（1）One-step hydrothermal synthesis of Nitrogen/Silicon-doped fluorescent carbon dots（N/Si-CDs）and detection of CAPBlue fluorescent carbon dots N/Si-CDs were synthesized using Itaconic acid and KH-602 as raw materials through a low-cost one-step hydrothermal method.The maximum excitation and maximum emission wavelengths of carbon dots are 360 nm and 450 nm,respectively.The emission wavelength does not change with the excitation wavelength.The fluorescence quantum yield is about 13.7%.At the same time,based on the principle of dynamic quenching between chloramphenicol and carbon dots,the blue fluorescence of carbon dots can be effectively quenched by chloramphenicol.As a result,a novel method for the detection of chloramphenicol was established.Under the best experimental conditions,the linear range is 0-200mg/L,and the detection limit is 5.3mg/L.N/Si-CDs were applied in the detection of Qingshan Lake water,and the recoveries and the relative standard deviations（RSD）were 92%-107%and 1.9%-4.4%,respectively.The detection method possesses a lower detection limit,a wider concentration range and a higher accuracy.（2）The construction of N/Si-CDs/Cd Te ratio fluorescence probe and detection of silver ion.The double emission ratio fluorescence probe based on N/Si-CDs and Cd Te was synthesized.Firstly,Cd Te quantum dots with bright yellow fluorescence were prepared from potassium tellurite,cadmium acetate,sodium borohydride and mercaptopropionic acid.Then,using N/Si-CDs as internal standard and Cd Te quantum dots as detection signal,a new ratio fluorescence probe was constructed and used to detect silver ions.Under the optimum conditions,it can be found that the fluorescence of Cd Te quantum dots is gradually quenched with the addition of silver ions,and there is a good linear relationship in the concentration range of 10-25mg/L(R²=0.989,F₄₅₀/F₅₇₅=0.00756+0.15968X)with 4.71mg/L of limit of detection.The recovery rate of silver ions in the lake water system is 91.7-107.2%,and the detection method has a good selectivity.（3）Synthesis of carbon dots with peroxidase-like activity and ratiometric fluorescent detection of hydrogen peroxide and phytic acidBlue luminescent Nitrogen/Cerium-doped carbon dots（N/Ce-CDs）with peroxidase-like activity were synthesized by one-step hydrothermal method using citric acid,urea and cerium nitrate hexahydrate as precursors.Based on the good fluorescence characteristics and catalytic activity of N/Ce-CDs,a ratio fluorescence sensing platform was constructed and used to detect hydrogen peroxide and phytic acid.In short,N/Ce-CDs catalyzed the oxidation of o-phenylenediamine（OPD）by hydrogen peroxide to produce 2-diaminophenazine（DAP）.DAP may be adsorbed on N/Ce-CDs by electrostatic interaction and interacted with N/Ce-CDs,which effectively quenched the fluorescence of N/Ce-CDs.At the same time,DAP produced a new emission peak at560nm.In addition,phytic acid may significantly inhibit the catalytic effect of N/Ce-CDs on the above oxidation reaction,and effectively protect the fluorescence of the carbon dots from quenching.The linear ranges of H₂O₂ and PA detection,are 0-90μM and 0-4.4μM,respectively,and the detection limits are 1.81μM and 0.14μM（S/N=3）,respectively.The detection method is sensitive and reliable,and shows off a very broad application prospect.