Studies On The Synthesis Of Noveal Multi-elements Co-doped Carbon Dots And Their Applications In Analysis And Cellular Imaging

Carbon dots?CDs?is a new type of"zero-dimensional"fluorescent carbon nanomaterial with a size of less than 10 nm,because of its excellent optical properties and good biocompatibility,it has attracted extensive attention from researchers at home and abroad.In recent years,researchers have made great achievements in the synthesis and application of carbon dots.However,there is still no uniform conclusion about the luminescence mechanism and the relationship between the synthesis method and performance.Therefore,the synthesis,performance and application of carbon dots still needs further investigation.Doping is an effective way to adjust the inherent properties of carbon dots.Doped carbon dots have different groups on the surface due to their different doping elements.It can significantly improve the optical performance and help to provide the functional groups required for target sensing.At present,it is mainly single element doped carbon dots and there are only a few two-element and three-element co-doped carbon dots.In this paper,a variety of organic molecules are used as precursors for the synthesis of two-element,three-element and metal elements co-doped carbon dots via one-step hydrothermal treatment.The composition and optical properties of the synthesized multi-elements co-doped carbon dots were characterized,and study its application in analysis and cellular imaging.The main research contents as follows:?1?Nitrogen-phosphorus co-doped carbon dots?N,P-CDs?were synthesized using sucrose,ethylenediamine?EDA?and phosphoric acid?H₃PO₄?as raw materials,which was heated at80?for 50 min.The structures of N,P-CDs were characterized by TEM,XRD,XPS and FT-IR.Interestingly,the fluorescence of N,P-CDs could be selectively quenched by hemoglobin?Hb?,based on this phenomenon,a fluorescence assay was proposed for determination Hb.Cytotoxicity investigation and cellular imaging experiments have shown that N,P-CDs are almost non-toxic and can be used for multicolor cellular imaging.?2?Nitrogen-boron co-doped carbon dots?N,B-CDs?were synthesized by a one-step hydrothermal method by using 3-aminobenzeneboronic acid?APBA?and 1,2-ethylenediamine?EDA?as precursors.The structures of N,B-CDs were characterized by TEM,XRD,XPS and FT-IR.The maximum excitation and emission wavelengths of N,B-CDs are located at 400 nm and 510 nm,respectively.The absolute fluorescence quantum yield?QY?of N,B-CDs was calculated to be 47.3%by using the integrating sphere.This N,B-CDs-based label-free fluorescent assay showed a sensitive response to?-glucosidase activity by using4-nitrophenyl-?-D-glucopyranoside?NGP?as the specific substrate.4-Nitrophenol which is released from NGP through the catalysis of?-glucosidase can significantly turn off the fluorescence of N,B-CDs through inner-filter effect?IFE?.Cytotoxicity investigation and cellular imaging experiments have shown that N,B-CDs are low cytotoxicity and green fluorescence.Moreover,a novel fluorescent sensing strategy for?-glucosidase activity and its inhibitor acarbose was achieved in living cells.?3?Red-fluorescent nitrogen,boron,sulfur co-doped carbon dots?N,B,S-CDs?were synthesized by a one-step hydrothermal method by using 3-aminobenzeneboronic acid and2,5-diaminobenzenesulfonic acid as precursors.The structures of N,B,S-CDs were characterized by TEM,XRD,XPS and FT-IR.In the UV-Vis absorption spectrum,N,B,S-CDs exhibit three absorption peaks at 234 nm,286 nm and 520 nm,respectively.In the fluorescence spectrum,the maximum excitation and emission peaks of N,B,S-CDs are located at 520 nm and 605 nm,respectively.The fluorescence of N,B,S-CDs can be quenched by Ag⁺due to its chelation with N,B,S-CDs.Due to the stronger binding interaction of Ag⁺with L-Cys,Ag⁺can be taken away from the surface of N,B,S-CDs after the addition of L-Cys.During this process,designed a simple and rapid fluorescence?on-off-on?sensor for Ag⁺and L-Cys.Cytotoxicity investigation and cellular imaging experiments have shown that N,B,S-CDs are low cytotoxicity and red fluorescence.Moreover,it can be used for the efficient detection of intracellular Ag⁺and L-Cys.?4?Nitrogen,phosphorus,sulfur co-doped carbon dots?N,P,S-CDs?were synthesized by a one-step hydrothermal method by using p-aminobenzene sulfonic acid?p-ASA?and phosphonium chloride?THPC?as precursors.The structures of N,P,S-CDs were characterized by TEM,XRD,XPS and FT-IR.The maximum excitation and emission peaks of N,P,S-CDs are located at 360 nm and 505 nm,respectively.The absolute fluorescence QY of N,P,S-CDs was calculated to be 36.8%by using the integrating sphere.The fluorescence of N,P,S-CDs can be quenched by Cr?VI?,on this basis,the N,P,S-CDs can be used as a fluorescence probe for detection of Cr?VI?.Cytotoxicity investigation and cellular imaging experiments have shown that N,P,S-CDs are low cytotoxicity and green fluorescence.?5?Nitrogen,cobalt co-doped magnetic carbon dots?N,Co-CDs?prepared by a facile one-pot hydrothemal method using citric Acid?CA?,diethylenetriamine?DETA?and cobalt?II?chloride hexahydrate?CoCl₂·6H₂O?as the C,N and Co source.The structures of N,Co-CDs were characterized by TEM,XRD,XPS and FT-IR and the magnetic properties were investigated by VSM.In this fluorescence sensor,o-phenylenediamine?OPD?was oxidized by H₂O₂ in the presence of horseradish peroxidase?HRP?to produce 2,3-diaminophenazine?DAP?which exhibited a yellow light emission at 540 nm.DAP then quenched the fluorescence of N,Co-CDs due to inner filter effect?IFE?.So,a ratiometric fluorescence sensor toward H₂O₂ was established by measuring the fluorescence signals of DAP and N,Co-CDs.Furthermore,the ratiometric fluorescence sensor was demonstrated ultrasensitive and highly selective for detection of the metabolites?Cholesterol and Uric acid?involved in H₂O₂-generation reaction.