Study On Rapid Detection Of Dopamine Based On Evanescent Wave

Small molecule dopamine is an important neurotransmitter in the human body.Its concentration level not only affects people’s mood,but also causes neurological diseases such as Parkinson’s,schizophrenia,and Alzheimer’s disease,so it’s importance to measure the concentration.In this thesis,by combining optical fibers with fluorescent gold nanoclusters,an optical sensor is constructed by two different strategies for dopamine concentration detection,which solves the challenge of large amount of samples required for detection,long detection time,and poor specificity.The main research results obtained are as follows:(1)Gold cluster(GSH-AuNCs)with fluorescence properties was prepared by reacting glutathione with chloroauric acid.Gold cluster has a very small size(about 1.4 nm)and glutathione as a ligand are connected to gold atom by Au-S chemical bonds.Under the light irradiation,the gold cluster shows bright orange-red fluorescence(emission wavelength:610 nm).We use semiconductor laser,coupling fiber,photodetector,microfluidic sample cell and other components to build an instrument(evanescent wave fiber sensor),which can detect the fluorescence signal of GSH-AuNCs.Based on the principle that the reaction product of tyrosinase and dopamine can quench GSH-AuNCs,the detection of dopamine concentration can be realized.Studying the fluorescence lifetime of GSH-AuNCs before and after quenching can find that the quenching mechanism is photoelectron-induced transfer.Under the continuous optimization of the detection conditions,only 200 μL of sample can be consumed to detect dopamine in the concentration range of 0-60 nM within two and a half minutes,with a detection limit of 30 nM.(2)Through research,it is found that low concentration of dopamine can enhance the fluorescence intensity of GSH-AuNCs.The GSH-AuNCs were modified to the surface of the optical fiber by chemical reagent treatment.The modified optical fiber sensor is used to detect dopamine,which achieves a sensitive,trace,and reproducible detection of dopamine,with a detection limit of 4.5 nM.Improved the detection limit of GSH-AuNCs fluorescence detection of dopamine.