Preparation And Properties Of Rare-earth Doped Upconversion Nanoparticles With Core-shell Structure

Recently,rare-earth doped upconversion materials have attracted wide attention from researchers due to factors such as narrow emission band,long fluorescence lifetime,high chemical stability,high luminescence intensity and low potential biotoxicity.It has important application prospects in the fields of fluorescence bioassay,three-dimensional bio-imaging,drug delivery,photovoltaic and photodynamic therapy,three-dimensional display,laser,anti-counterfeiting coding labels.Although rare-earth doped upconversion nanomaterials hold attractive prospects,there are still many problems to be solved.In this research,a series of related rare-earth doped fluoride micro/nano luminescent materials were prepared by high temperature coprecipitation method and hydrothermal method.And their growth process,luminescent properties and practical applications were studied.In the second chapter,the flower-like upconversion nanoparticles were prepared by high temperature coprecipitation at 220°C,and the influencing factors of crystal growth were systematically studied.In the third chapter,the multi-shell structure upconversion nanoparticles NaNdF₄:Yb@NaYF₄:Yb,Er@NaGdF₄@mSiO₂-NH₂-phenanthroline were prepared by coprecipitation method,and its energy transfer process was studied.We found it available in ion detection.In the fourth chapter,different sizes of NaYF₄:Yb,Er micro-rods/tubes were prepared by sodium citrate assisted hydrothermal method.By compounding it with silica aerogel,a new material was prepared.The main content of this thesis is as follows:?1?The upconverting nanoparticles are grown under low temperature conditions?220°C?by adding a mixed solution of ammonium fluoride and sodium hydroxide dropwise,and the prepared nanoparticles with good luminescent properties are snow-like.The effects of reaction temperature,ammonium fluoride dosage,and the addition method of the mixed solution on the growth of nanoparticles were systematically studied.It was found that the growth of the flower-like nanoparticles at low temperature was coordinated by all conditions mentioned above.Flower-like nanoparticles with large size and specific surface area can combine with two-dimensional materials as new optical materials.And a huge amount of energy can be saved by the way of low temperature growth,which will promote the industrial development of nanoparticles.?2?Upconverting green light emission was achieved by dual-wavelength excitation of 980 nm and 808 nm,respectively.Multi-shell nanoparticles of NaNdF₄:Yb@NaYF₄:Yb,Er@NaGdF₄ were prepared by coprecipitation method,and the process of energy transfer of different rare-earth ions were analyzed.At the same time,the nanoparticles are coated with an aminated mesoporous silica layer and coupled with2,9-dicarboxy-1,10-phenanthroline in order to obtain the properties of luminescence and ionic coordination.The final product could be applied in detection of metal ions such as copper.?3?The preparation of NaYF₄:Yb,Er microrod/tube was controlled by adjusting the amount of sodium citrate.And it was composed with silica aerogel through sol-gel method to prepare a highly porous and high-surface-area novel composite material with both properties of luminescence and oxidized gas gel carriers.Comparing the effects of NaYF₄:Yb,Er microrod/tube,NaYF₄:Yb,Er nanoparticle and Tb-BTC metal organic framework on silica aerogel,the optically transparent,struct urally complete silica aerogel was finally obtained,and used for display and anti-counterfeiting.