Preparation Of Rare-earth Upconversion Luminescent Materials And Their Application In Fluorescent Probe

The rare-earth upconversion luminescent materials?UCNPs?have a lot of merits including excellent chemical and photo stability,high detection sensitivity and signal-to-noise ratio,greater tissue penetration,weak auto fluorescence background and absence of photo damage to live organisms because of its special energy level structure and the luminescent mechanism.Therefore,UCNPs have quickly become to be a hotspot in the detection of inorganic ions,organic small molecules and biological molecules.Based on this,in this paper,we not only designed,but also synthesized two types of luminescent resonance energy transfer techniques?LRET?nanoprobes composed of UCNPs and metal nanoparticles,in which UCNPs and metal nanoparticles were as the energy donors and acceptors respectively,and used it to detecting manganese ions and melamine molecular.The morphology features and other properties of obtained samples were characterized by SEM,TEM,fluorescence spectrometer,XRD,FT-IR,UV-Vis spectrometer,Zeta potential of punishment and other characterization methods carefully.This paper consists of following three chapters:In Chapter 1:The UCNPs of background,luminesce principles and development prospect of the study were introduced.And then the application of the UCNPs in biological imaging and luminescent probe were discussed in detail.In Chapter 2:A new luminescent probe on the basis of LRET was explored.The positively charged NaYF₄:Yb,Er UCNPs and the negatively Ag NPs were used as the energy donors and energy acceptors respectively,they bound together through electrostatic interaction.The green emission peak of UCNPs located at the 542 nm,which was good overlapped with the absorption spectrum of Ag NPs.As a result,luminescence quenching was observed due to the LRET from UCNPs to Ag NPs.With the addition of manganese ions,LRET process was inhibited and then the luminescence intensities of UCNPs recovered.Moreover,the luminescence recovery was found to show a good linear to its concentration and could be used to detect manganese ion.The response is linear to the concentrations of Mn²⁺in the range from 0.2 to 5?M,and the detection limit is evaluated to be 150 nM?S/N=3?.This probe was easy to operate with satisfactory selectivity and excellent sensitivity,which would be able to satisfy the requirements of Mn²⁺-related detection.In Chapter 3:A green and red light emission together NaYF₄:Yb,Er was synthesized by a simple hydrothermal process,which is as energy donor.Gold nanoparticles was selected as energy receptors.In this study found that the LRET was efficiently when pH=6.864.At the same time,the linear relationship was established between the concentration of melamine molecular and the ratio of fluorescence intensity,The response is linear to the concentrations of melamine in the range from 20 to 200?M,and the detection limit is evaluated to be 11?g/L,which realized the efficient detection of melamine molecular.