Preparation Of Heteroatom Doped Carbon Dots By Hydrothermal Method And Their Applications In Fluorescence Sensing

In recent years,Carbon Dots（CDs）have gradually become potential substitutes for traditional fluorescent materials due to their excellent physicochemical properties.At present,many studies have shown that heteroatom doping can not only effectively improve the fluorescence quantum yield of CDs,but also redshift the emission spectrum of CDs by changing the band gap and energy level of CDs,thus it is an effective method to improve CDs luminescence performance.Therefore,in this paper,three kinds of fluorescent CDs with tunable emission wavelength were synthesized by the method of element doping using different carbon sources and nitrogen sources,and their properties were comprehensively characterized by kinds of technical analysis means,and they were applied to the detections and cell imaging in the environment.The main contents are as follows:1.Nitrogen-rich and sulfur-rich carbon points（N,S-CDs）were synthesized by one-step hydrothermal method using cysteine（L-cys）and 1-amino-2-naphthol 4-sulfonic acid as raw materials.Since the groups on the surface of N,S-CDs have formed non-luminous coordination complexes with Fe³⁺,fluorescence of CDs was quenched.However,when AA was added,the reduction of Fe³⁺by AA can restore the fluorescence of N,S-CDs,and the continuous and rapid analysis of Fe³⁺and AA can be performed quickly based on the“on-off-on”of fluorescence signal of N,S-CDs.Linear range were 5.00-105μM and 4.97-54.8μM,detection limit were 0.10μM and 2.40 n M,respectively.At the same time,the method can realize the quantitative detection of Fe³⁺in traditional Chinese medicine.2.Using o-phenylenediamine and p-aminobenzoic acid as raw materials and ethanol as solvent for hydrothermal reaction,a novel functional fluorescent probe based on nitrogen doped carbon dots（N-CDs）was constructed.It can emit high intensity yellow fluorescence at 596 nm under excitation at 390 nm wavelength,with a quantum yield of0.36.Based on the fluorescence quenching phenomenon of N-CDs,a highly sensitive and selective Cr（Ⅵ）sensing platform for the detection of Cr（Ⅵ）in actual environmental water samples was established with a detection limit of 1.94μM.N-CDs exhibited selective p H-dependent fluorescence behavior.N-CDs had also been successfully used in Hela cell imaging applications due to their low toxicity and good biocompatibility.This study provided a theoretical basis for the application of green,fast,efficient and real-time fluorescent probes.3.Using Rhodamine B and ethylenediamine as precursors,N,Cl doped carbon point（N,Cl-CDs）was synthesized by a green one-step hydrothermal method.The obtained N,Cl-CDs were characterized,and the results showed that the synthesized N,Cl-CDs had uniform size,good water dispersion and strong orange fluorescence emission.Because the fluorescence mechanism of IFE,N,Cl-CDs was significantly quenching by VB₉and VB₁₂.Meanwhile,based on the synergistic effect of dynamic quenching,the sensitive detection of VB₂was realized.Because of VB₂,VB₉and VB₁₂and N,Cl-CDs role after the color difference,proposed in 15.0μM-125μM,25.0μM-200μM and 25.0μM-150μM within the scope of use of strip of three vitamin visual qualitative and semi-quantitative detection.In addition,the N,Cl-CDs can be applied to biological imaging.