Eepitaxy Growth And Surface Structure Regulation Of NaREF₄ Nanocrystals

Single particle composite structure nanocrystals,which integrate various characteristic materials into one,have important potential application value in biomedical,clean energy and environmental protection.How to realize the reasonable structure design and accurately control the growth of composite structure nanocrystals is an important direction in the field of nanomaterials research.Rare earth doped up conversion fluorescent nanomaterials are a kind of fluorescent nano materials with unique optical properties.It can emit a photon with shorter wavelength（near infrared,visible or ultraviolet）by absorbing two or more photons with longer wavelength（near infrared light or ultraviolet light）,because it has the characteristics of narrow emission band,large anti-Stokes displacement,low toxicity and high stability.It has important application value in biomedical,display,biological detection,clean energy and other fields.In this paper,we will study the mechanism of surface structure regulation of rare earth doped up conversion fluorescent nanocrystals,systematically study the effects of over metal cation environment aging treatment of different kinds and combinations on the surface structure and properties of nanocrystals;explore the performance of various mature nanocrystals in the growth control of hetero shell epitaxy;and try to taste The core-shell composite nanocrystals with large lattice mismatch were synthesized.The specific research content includes the following four parts:In the first chapter,the basic knowledge of growth control of up conversion nanocrystals doped with rare earth is introduced,and the latest development status and bottleneck problems of upconversion nanocrystals are summarized.In chapter two,the control of the size and morphology of NaYF₄ nanocrystals and the basic control method of the epitaxial growth of NaREF₄ shell are studied.In Chapter 3,the influence of lattice mismatch on the epitaxy of NaREF₄ shell is studied.The different NaREF₄ shells（RE=Lu,Yb,y,Tb,Eu,Gd,Ho,Sm,Nd,Ce,La）are grown by NaYF₄ as the core.In chapter four,the heat treatment process of excess potassium ions is studied systematically,which regulates the surface structure of NaYF₄ nanocrystals.The effect of up conversion fluorescence intensity after surface structure treatment was also characterized.In this paper,by changing the temperature,the proportion of octadecene oleic acid,the proportion of each component,as well as adding different cations,the different treatment of rare-earth tetrafluorofluoride sodium materials.Compared with other fields of research direction is different,we prefer to explore nano materials in the process of crystal growth,what factors lead to the growth of different nanomaterials,by studying these growth principle,is committed to establish a controllable growth,in response to different needs in various fields of morphology the universal law of performance.In this paper,through the following chapter two,three and four,we have gradually studied the laws of several directions of nanomaterial crystal growth.It is concluded that:1,rare earth tetrafluorofluoride sodium nanomaterial is difficult to break through the limit of lattice mismatching degree of 5%at the present stage;2.In the cationic solution rich in K ions and Gd ions,rare-earth tetrafluorosodium nanomaterials will undergo cationic corrosion and form changes of different morphologies.Through these changes,we can regulate the composition of cations to design nanomaterials with different morphologies we need;3.Through the characterization of nanomaterials with different treatments,we can understand how different degrees of treatment will affect the properties of nanomaterials.