Research On Dual-Color Luminescence And Near Infrared Light Excitation Luminescence Of Rare Earth Ion Complexes And Their Analytical Applications

The fluorescence of rare earth ion has the characteristics of narrow band emission,large Stokes shift and long fluorescence lifetime.Rare earth ion complexes play an important role in the fields of analysis and biological imaging.Various methods such as surfactant sensitization,rare earth co-luminescence effect,and metal surface enhanced fluorescence effect are widely used to enhance the luminescence of rare earth ions.Dual-color rare earth ion luminescent probes has more response signals,compared with green luminescence,red luminescence in longer wavelength region not only has better tissue penetration depth,but also can effectively avoid the interference of endogenous fluorescence of biological substances.Using light with a wavelength near the near-infrared range as the excitation light can effectively reduce light drift effects and reduce light damage.Catecholamines(CAs)are essential for the transmission of information in the nervous system.The imbalance of CAs can lead to a variety of neurological diseases such as Parkinson's disease.Therefore,it is of great significance to establish a sensitive analysis method for CAs concentration monitoring and related diseases diagnosis and research.Curcumin(Cur)has many medicinal values such as anti-inflammatory and anti-cancer.Its daily intake as a food additive is limited,therefore,the highly sensitive and selective analysis method for Cur is very important for its food safety and clinical research.This thesis expands the application of fluorescence analysis of rare earth ion complexes.It was found that CAs could enhance the red and green fluorescence of Eu3+and Tb3+,and the sensitive determination of CAs was realized by the change of Eu3+fluorescence enhancement.The Eu(III)complex was excited by NIRL under xenon lamp,and the sensitive determination of Cur was realized by the change of fluorescence intensity of Eu3+excited by NIRLIn the preface part of the thesis,the fluorescence analysis methods of rare earth ion complexes,the analytical methods of rare earth ion dual-color luminescence and NIRL excitation fluorescence under xenon lamps are briefly summarized.And the analytical methods and research progress of CAs and Cur were reviewedIn the second chapter,the enhancement of Tb3+/Eu3+ dual-color luminescence by catecholamine was studied:when catecholamines(EP or DA)coexist with Eu3+ and Tb3+,the system can emit red and green fluorescence simultaneously.Compared with the single Tb3+ and Eu3+ complexes,the green fluorescence decreased and the red fluorescence increased.The mechanis:study shows that,wheL Eu3+.is present in the Tb3+-EP system,there is effective energy transfer from Tb3+complexes to Eu3+complexes,which makes the fluorescence emission of the system changed from green to red with longer wavelength.Further research found that the concentration of EP and DA has a good linear relationship with the fluorescence enhancement of Eu3+,therefore,a sensitive method for the determination of them was established.In the third chapter,the thesis studies the fluorescence characteristics of Eu3+complex excited by near infrared light and its analytical application:under the excitation of NIRL of xenon lamp,the multicomponent complex system consist of Eu3+,Gd3+,2-thenoyltrifluoroacetone(TTA)and cetyltrimethylammonium bromide(CTAB)can emit characteristic fluorescence of Eu3+,and the fluorescence can be significantly quenched by Cur.Based on the quenching effect of Cur on the Eu3+ complex,a sensitive detection method for Cur is proposed.Under the optimal conditions,under the excitation of 746 nm of xenon light,there is a good linear relationship between the fluorescence quenching degree at 611 nm and the concentration of Cur in the range of 2.0 × 10-9 M-6.0 × 10-8 M.The detection limit(LOD,S/N=3)was 5.2 × 10-10 M.Under the same conditions,the linear range of the Stokes fluorescence method(?ex/?em=360/611 nm)is 1.0 × 10-8M-6.0 × 10-8M,and LOD is 2.6×10-9 M.Both methods were successfully applied to the determination of Cur in real samples.The mechanism study shows that the emission of Eu3+ complexes under NIRL excitation is mainly due to second order diffracted light(SODL)excited fluorescence.The difference between NIRL excited fluorescence and Stokes fluorescence is compared and the luminescence characteristics were significantly different.The fluorescence lifetime and quantum yield,UV-vis spectrum,resonance light scattering spectrum,surface tension curve were used to investigate the quenching mechanism and interaction mechanism of Cur on Eu3+complex.Cur inhibited the intermolecular energy transfer process through the interaction with Gd3+and CTAB,which reduced the fluorescence intensity of Eu3+.