Study On Dopamine Detection Methods Using Fluorescent Carbon Quantum Dots

Dopamine,as a neurotransmitter,plays a huge role in living things.When the concentration changes abnormally,it will also lead to different physiological or pathological consequences of the organism.Due to the low content of dopamine in the body,complex matrix,and severe interference,establishing a sensitive and specific detection method for dopamine in vivo is of great significance.Fluorescent carbon quantum dots,a carbon nanomaterial with a size of less than 10nm and fluorescent properties,can be used in various research fields because they can react with certain substances and cause fluorescence quenching.In this dissertation,we mainly prepared fluorescent carbon nanodots with high fluorescence quantum yield,strong optical stability and good biocompatibility,and obtained fluorescent carbon nanomaterials with excellent optical properties.Optimize test conditions and analysis of interfering substances,explore the mechanism of action of this class of materials and dopamine,and thus further apply it to the analysis of human urine.The main research contents of This paper are as follows:Chapter 1.Synthesis of Carbon Quantum Dots from Soymilk and its Application in Dopamine DetectionThe nitrogen-doped carbon quantum dots(N-CQDs)were prepared by one-step hydrothermal treatment with soy milk as both carbon source and nitrogen source.The obtained N-CQDs exhibited excellent water-solubility and high stability.Rapid and accurate dopamine(DA)detection based on the selective fluorescence quenching effect of N-CQDs was achieved.Transmission electron microscope(TEM)image showed that the diameter of particles was about 3nm.Fourier transform infrared(FTIR)and X-ray photoelectron spectroscopy(XPS)spectra analysis demonstrated that the N-CQDs were functionalized with hydroxyl,amino,carbonyl groups,which indicated N-CQDs had better-solubility.Fluorescence quenching ratios kept a linear relationship with the concentrations of DA in the range of 0.1~100?M(R~2=0.9928)with the detection limit of0.05?M.It was successfully applied to determination of DA in urine samples.The satisfactory recoveries are 93.9%~109.6%and the relative standard deviations(RSD)are2.9%~5.4%.Therefore,fluorescence quenching based on nitrogen-doped carbon quantum dots.The method should be used for the detection of dopamine.Chapter 2.Synthesis of Carbon Quantum Dots from polyacrylamide and its Application in Dopamine DetectionNitrogen-doped carbon quantum dots(N-CQDs)were synthesized by one-step hydrothermal method using polyacrylamide as the carbon source and nitrogen source.The prepared N-CQD has a higher quantum yield and exhibits good water solubility and fluorescence properties.In addition,N-CQD can be used as a fluorescent probe for sensitive and selective detection of dopamine.Since dopamine is converted to dopamine-ruthenium under basic conditions,the fluorescence of N-CQD is effectively quenched after addition of dopamine.There was a good linear relationship between fluorescence quenching and dopamine concentration in the range of 0.1-200?M,with a detection limit of 0.05?M.The proposed method shows high selectivity for dopamine in the presence of interfering substances.In addition,this method was successfully applied to the determination of dopamine in urine samples with a recovery of 97.0 to 109.0%and a relative standard deviation of 2.6 to 7.0%.