Longer Wavelength Excited Luminescence In Aqueous Solutions And Its Analytical Application

Dopamine(DA,3,4-dihydroxyphenylethylamine)is an important neurotransmitter and plays an important physiological role in organisms.The imbalance of DA content is closely related to neurodegenerative diseases,Parkinson's diseases.Dopamine is suitable for the treatment of refractory heart failure,infectious,cardiogenic shock and other diseases.Therefore,the establishment of a sensitive analytical method of dopamine is of great significance for the diagnosis and treatment of related diseases.In addition,dopamine is an endogenous fluorescent substance,and the research of new fluorescent sensor based on DA fluorescence characteristics has potential application values.Iron,an important trace element in human body,is essential for cell metabolism and oxygen transport and nerve transduction.Studies have shown that Alzheimer's disease is related to iron excess deposition and the interaction between iron ions and DA/DA-derived neuromelanins.However,the massive discharge of iron ions in industrial wastewater aggravates environmental pollution and health questions.It is of great significance to study the interaction mechanism between iron ions and DA and to establish a sensitive and selective analytical method for Fe3+ ions.Upconversion luminescence(UCP)is a phenomenon with longer wavelength excitation and shorter wavelength emission.Usually,the excitation wavelength of UCP is in the near infrared region,UCP has little light damage to biological samples and is not interfered by the auto:fluorescence.However,the UCP needs a laser as the excitation source,and water solubility and luminescent efficiency of the UCP materials need to be improved.At present,the newly 'UCP' method using xenon lamp as light source is simple,sensitive,and can be realized in aqueous solution system.However,the mechanism of its luminescence needs to be further studied.The purpose of this paper is to develop a new method of'UCP'analysis on common spectrofluorometer,which can be applied for the detection of specific target analytes.This thesis consists of four parts.In the first part of the thesis,the progresses of fluorescence analysis of DA and iron ions(?)are introduced,and the luminescence methods of rare earth ions are summarized.The new 'upconversion' luminescence methods under xenon lamp in recent years are reviewed.In the second part of the thesis,the spectral characteristics of longer wavelength excited luminescence(LExL,?ex>?em)of DA are studied by common spectrofluorometer with a Xenon-lamp light source.The two-photon absorption cross sections of DA are calculated by density functional theory(DFT).The LExL of DA mainly contains the excitation of second-order diffraction light(?ex/2)and maybe partly the two-photon processes.The dual-mode luminescence methods based on LExL and Stokes fluorescence(SL)of DA were adopted for studying the interaction of DA with Fe3+ and the selective determination of Fe3+.The results show that the interaction between DA and Fe3+ mainly involves the complexation of DA with Fe3+,the oxidation of DA,the formation of PDA-Fe3+ complexes.Compared with SL method,LExL method has better selectivity when Fe3+ coexists with Pb2+,Cd2+,Ag+,K+,Na+,Mn2+ or Co2+ ions.In addition,the linear correlation and stability of LExL method shows better linear correlation,test stability,and the lower detection limitIn the third part of this paper,the LExL(X?x?Aem)of Ce(?)ion at 345 nm is realized under 810 nm near infrared(NIR)excitation.The LExL of Ce3+ ion under xenon lamp is mainly produced by the excitation of third-order diffraction light(?ex/3).The effective energy transfer between Ce(?)and Tb(?)can further realize the Stokes fluorescence of Tb(?)ions.The coordination of DA with Ce(III),Tb(?),and enhances intermolecular and intramolecular energy transfer,thus enhancing their luminescence efficiency.A LExL method of Ce(III)-Tb(?)for the determination of DA under xenon lamp source of common spectrofluorometer was established.