Preparation Of Carbon Quantum Dots Based On Protein Carbon Source And Application Research Of Fluorescence Sensing

Since the first discovery of carbon quantum dots in 2004,carbon quantum dots have been widely used in analytical chemistry,biochemistry,medicine and environmental monitoring and other fields,due to their excellent physical and chemical properties,such as water solubility,excellent optical performance,structure of regulatory,light bleaching and low toxicity,etc.In this paper,protein-rich substances were selected as carbon sources,and multiple carbon quantum dots were obtained by one-step hydrothermal synthesis.Based on the fluorescence properties of carbon quantum dots,A fluorescence sensing platform was designed for detecting Hg²⁺,ciprofloxacin and Fe³⁺,respectively,and their mechanism was studied.The main research contents of this paper are as follows:?1?Nitrogen-doped carbon quantum dots?N-CQDs?were synthesized by one-step hydrothermal method using pork,which is rich in protein,fat and carbohydrates,as carbon source and nitrogen source.Based on the phenomenon that Hg²⁺can cause fluorescence quenching of nitrogen-doped carbon quantum dots with high fluorescence emission,a method for rapid detection of Hg²⁺was established.The nitrogen-doped carbon quantum dots were characterized by transmission electron microscopy?TEM?,X-ray photoelectron spectroscopy?XPS?,FT-IR spectra,etc.The results showed that the surface of the quantum dots contained a large number of hydrophilic groups?hydroxyl,carboxyl,etc.?,indicating a good water solubility.The particle size is about 3.5 nm.In the experimental research,the factors affecting the detection results were optimized.Within the Hg²⁺concentration of 1-10?M,the fluorescence intensity had a good linear relationship with the Hg²⁺concentration?R²=0.999?,and the detection limit was 0.5?M.This method was applied to the detection of Hg²⁺in real samples,with a recovery rate of 88.82%-93.89%and a relative standard deviation of 0.86%-1.1%.?2?Nitrogen-doped carbon quantum dots?N-CQDs?with high fluorescence emission were prepared by one-step hydrothermal synthesis using soybean milk which is rich in a variety of amino acids as carbon source and nitrogen source.A sensitive and selective fluorescence detection method for CIP was developed.The surface chemical components of carbon quantum dots were characterized by X-ray photoelectron spectroscopy?XPS?and FT-IR spectroscopy.It was found that the surface of carbon quantum was covered with-COOH,-NH₂,-OH and other groups.The structure characterization results of TEM show that the average particle size of carbon quantum dots is uniform and about 3 nm in average.Fluorescence spectrum analysis showed that the carbon quantum dots had excellent optical properties,with a quantum yield of 29.85%and a maximum excitation wavelength of 310 nm.Under the optimal experimental conditions,the fluorescence sensitization experiment of ciprofloxacin showed a good linear relationship within the range of the concentration of ciprofloxacin 0.1-10.0?gml^-1.The linear regression equation was y=70.001x+225.64,R²=0.999,and the detection limit was 0.09?g ml^-1.The method has good reproducibility and stability,and the recovery rate is 87.76%-97.63%.?3?Nitrogen-doped carbon quantum dots?N-CQDs?were synthesized by one-step hydrothermal synthesis using soybean milk as carbon and nitrogen sources,and the quantum yield was 29.8%.?-cyclodextrin was used as modifier,coating the surface of a carbon quantum dots with?-CD by chemical reaction,?-cyclodextrin-modified carbon quantum dots??-CD-N-CQDs?were prepared with a quantum yield of 38.2%.It can be seen from TEM that the particle size?9 nm?of modified carbon quantum dots??-CD-N-CQDs?is significantly increased compared with that of unmodified carbon quantum dots?3nm?.The characterization of X-ray photoelectron spectroscopy?XPS?indicates that the modified carbon quantum dots are rich in C,N and O elements with a large number of amino,hydroxyl,carboxyl and other structures.Fluorescence spectra showed that the maximum excitation wavelength of?-CD-N-CQDs was 380 nm,and the fluorescence of?-CD-N-CQDs had obvious excitation dependence as well as the emission light shifted red with the increase of excitation light.Under the optimal experimental conditions,the fluorescence intensity of Fe³⁺in the range of 0.5-10?M had a good linear relationship with the fluorescence intensity of?-CD-N-CQDs fluorescent probe,and the detection limit was 0.1?M.In the spiked recovery experiment of water samples,the recovery rate was 90.27%-95.68%.