Fluorescence Spectra And Analytical Applications Of Dopamine And It's Metabolite

Dopamine(DA,3,4-dihydroxyphenethylamine)is a catecholamine secreted mainly by the nervous tissue and adrenal medulla of the adrenal glands and is used as a neurotransmitter and hormone in the blood circulation.Homovanillic acid(HVA,4-hydroxy-3-methoxyphenylacetic acid)is the main metabolite of DA.DA and HVA are involved in the regulation of the central nervous system,endocrine system and cardiovascular system.Abnormal level of DA is closely related to hypertension,myocardial infarction,neuroendocrine tumors,neurodegenerative diseases.Therefore,it is very important to establish a simple and highly sensitive analysis method to detect DA in vivo.HVA content was mainly affected by DA.In addition,the content of HVA in the body would be affected by Fe3+ in the environment.Fe3+is an important trace element.The abnormal content of Fe3+ could damage nucleic acids and cells.Alzheimer's disease and Parkinson's disease are closely related to Fe3+Therefore,exploring the interaction between HVA and Fe3+will help to further understand their role in the pathogenesis of neurodegenerative diseases.This thesis includes three sections.In the first section,we outlined the significance and the progress of the detection of DA and the interaction between HVA and Fe3+,and introduce the sensitization method of rare earth ion luminescence.Besides,we give a brief overview of the influencing factors of metal-enhanced fluorescence(MEF)and the research progress in the analytical methods of gold-silver core-shell nanoparticles(Au@AgNPs).In addition,a new upconversion luminescence method under xenon lamp is introducedIn the second section,Au@AgNPs with different Ag shell thicknesses were synthesized at room temperature,and their fluorescence enhancement effects on Tb(?)-DA complexes were explored.We found that the MEF efficiency of Au@AgNPs is dependent on the thickness of the Ag shell.Under about 7.5 nm thickness of the Ag shell,Au@AgNPs has stronger MEF efficiency than gold nanoparticles and silver nanoparticles.Based on the fluorescence enhancement effect of Au@AgNPs on Tb(?),the Tb(?)-Au@AgNPs fluorescent probe was established for sensitive and selective determination of DA.Under the optimized experimental conditions,the increase in the fluorescence intensity signal of the system and the DA concentration have a good linear relationship in the range of 0.80-300 nM and 300-1000 nM,and the detection limit is 0.70 nM(S/N?3).This method was successfully applied to the standard recovery and determination of DA in human serum samples.Through UV-vis absorption spectra,Zeta potential,dynamic light scattering,TEM,fluorescence lifetime,infrared spectra,Raman spectra and other experimental techniques,the interaction mechanism of Au@AgNPs enhancing Tb(?)fluorescence was discussed in detail.In the third section,we discovered the phenomenon of longer wavelength excitation fluorescence(LExL)of HVA using a common spectrofluorometer with a xenon lamp as excitation source.And the experiment results showed that the LExL of HVA may mainly be assigned to the fluorescence excited by the second-order diffraction light.Under the excitation of 557 nm(LExL)or 287 nm(Stokes fluorescence,SF),adding Fe3+to the HVA solution causes the intrinsic fluorescence at 310 nm of HVA was quenched,and a new fluorescence peak at 424 nm appeared.Thus,a dual-mode ratiometric fluorescence(RF)method for detecting Fe3+ was developed based on the changes of I424 nm/I310 nm of LExL and SF signals.The RF signals of 1g(I424nm/I310 nm)had excellent linearity with Fe3+ concentration in the range of 0.50-100 ?M.Their detection limits were 0.073 ?M and 0.090 ?M(S/N?3)for the LExL and SF methods,respectively.The LExL and SF methods exhibited high selectivity for detecting Fe3+,and the former has stronger anti-interference ability to Cu2+,Fe2+ etc.The two methods were successfully applied for the detection of Fe3+in actual water samples.The interaction mechanism of HVA with Fe3+ was also studied.