Preparation Of Nitrogen-doped Carbon Dots And Its Preliminary Application In Environmental And Biological Analysis

Fluorescence method,as a fast,convenient,and simple method of analysis and detection,is widely used in environmental and biological analysis fields.Fluorescence probe technology is an important research direction in fluorescence analysis.Carbon dots,a newly discovered carbon nano-material,have attract extensive research interest due to its excellent optical properties.Carbon dots have excellent optical properties(strong luminous ability,wide and adjustable spectral range,good light stability and easy to function,etc.),while abandoning the shortcomings of traditional luminescent materials such as poor toxicity and poor biocompatibility.Although the development of CDs has made great progress over the past decade since its was discovered in 2004,there are still many key problems unsolved,mainly in the following aspects:(1)There are still few reports on the detection of perfluorinated compounds in the environment based on the carbon dot-based fluorescence analysis method.In a small number of reports,the sensitivity and stability of the method are difficult to meet the requirements of actual sample analysis.(2)When carbon dots are used to detect biological samples,the complex components of biological samples is a major problem,which limits the application of carbon dots.(3)When carbon dots identify tumor cells in biological tissues or organisms,due to insufficient selectivity of carbon dots,they often have weaker or even unable to identify targeted cells.Therefore,this article focuses on carbon dots.The main work is as follows:1.Simple preparation of nitrogen-doped carbon dots and highly selective fluorescence detection of trace perfluorooctyl sulfonate in environmental water samples.Nitrogen-doped carbon dots(N-CDs)were synthesized via hydrothermal treatment of vitamin B1 and triethylamine.The obtained N-CDs showed strong blue fluorescence(?ex=370 nm??em=437 nm),good Water solubility,and excellent fluorescence stability in the pH range of 3?12,ionic strength between 0.01 and 1 mol/L,and 6 hours of ultraviolet irradiation.The mechanism of nitrogen-doped carbon dot fluorescence detection of trace PFOS in aqueous solution was discussed.The result show that N-CDs respond selectively PFOS through electrostatic interactions.N-CDs aggregated slightly when in the presence of low-concentration PFOS which lead to fluorescence enhancement.Even in the presence of other common metal ions,anions and structural analogs such as surfactants,N-CDs are highly selective for PFOS.The response is linear in the 0.3 to 160 nmol/L PFOS concentration range with a detection limit of 0.3 nmol/L under the optimal conditions.The method was applied to the detection of PFOS in surface water samples,and the results obtained were in good agreement with the results of HPLC-MS/MS.2.Magnetic Carbon Microsphere Purification-Nitrogen Doped Carbon Dot Fluorescence Detection of Trace Perfluorooctyl Sulfonate in Egg Samples.The traditional detection method for trace PFOS in egg samples is HPLC-MS.HLB hydrophilic lipophilic equilibrium solid-phase extraction cartridges are usually used for purification,after egg samples are extracted with organic solvents.The egg samples contain a large amount of protein,fat and peptides,which can greatly interfere with the fluorescence signals of N-CDs,causing inaccurate experimental results even after the extract is purified by HLB hydrophilic lipophilic equilibrium solid-phase extraction cartridge.So,a dual-core magnetic carbon microsphere(Fe₃O₄@PDA@C-K)is designed and synthesized as a sample purification material.After the egg sample extract was adsorbed-desorbed by the magnetic carbon microspheres,carbon point fluorescence detection of PFOS content was successfully achieve.The analysis results of batches of actual samples show that there is no significant difference between the detection results of carbon dot fluorescence method and the results of HPLC-MS/MS.The new method is sensitive,fast,simple and accurate.3.The peptide-functionalized carbon dots serve as fluorescent probes to specifically recognize cancer cells.AP2H peptide that can specifically recognize cancer cells was synthesized using peptide solid phase synthesis(SPPS).Using citric acid as the carbon source and polyethyleneimine(PEI)as the nitrogen source,hydrothermal methods were used to synthesize carbon dots(CDs)with high quantum yield,good fluorescence,and rich amino groups.The carbon dots were linked to the AP2H peptide via an amide bond to construct CDs-AP2H with both recognition and reporter groups.CDs and CDs-AP2H probes were used to incubate human hepatoma cells(HepG2)and human embryonic kidney cells(HEK293)simultaneously.The laser confocal scanning microscope result show that obvious fluorescence was observed in HepG2 cytoplasm after CDs-AP2H incubation,and there was only weak fluorescence or even no fluorescence in HEK293 cells.However,Weak fluorescence was observed in HepG2 and HEK293 cells incubated with CDs.These results indicate that the functionalized carbon dots of the peptide are expected to be applied to the detection of liver cancer cells.In addition,the cytotoxicity of CDs and CDs-AP2H was examined,and the results showed that the survival rate of HEK293 cells after incubation with CDs and CDs-AP2H was higher than 95%.