Synthesis Of Manganese/Europium Doped Zinc-Based Chalcogenide Nanoclusters And Their Photoluminescence Property

In recent years,ZnS semiconductor nanocrystals have become the research focus and hotspot in the field of inorganic chemistry and material chemistry due to its unique properties in optics.To obtain ZnS nanomaterials with diverse and stable photoluminescence properties,doping impurity ions,controling nanocrystals size,and constructing the core-shell structure are regarded as effective strategies on the post-modification of ZnS.Among them,the doping strategy can directly introduce the active sites and effectively change the energy band structure of ZnS.In 1994,Bhargava et al.published the first case of manganese-doped ZnS nanocrystals with 590 nm yellow orange emission and a quantum yield of up to 18%.This work aroused the public interests in the doped ZnS nanocrystals.However,such traditional ZnS nanocrystals have some disadvantages.For example,traditional synthetic strategy makes the inevitable agglomeration of ZnS nanocrystals,therefore ZnS nanocrystals without uniform size can not serve as ideal structural model for studying size-dependent optical properties.In addition,the disordered and random distribution of the doping ions in the crystal lattice make it extremely difficult to establish a clear structure-function relationship.In view of the above limitations of ZnS nanocrystals,a new class of material should replace the ZnS nanocrystals to solve these problems.Metal chalcogenide supertetrahedral Tn clusters("T" means tetrahedron,"n" is the number of metal layers along the edge of the supertetrahedron)with uniform adjustable size,abundant intercluster assembly mode and precise structure have become perfect structural model for studying the structure-activity relationship.In this thesis,the supertetrahedral Tn clusters are used as research objects.On the one hand,we achievd a breakthrough to push up the size limit to T6;on the other hand,in-situ solvothermal method was applied to introduce doping ions into clusters,and the influence of cluster size,intercluster connection mode and precise doping behavior on the photoluminescence properties were explored.It will provide theoretical guidance for further clarifying photoluminescence mechanism of doped nanomaterials at atomic levels.The research contents are as follows:1.Synthesis of ultralarge zinc-based chalcogenide supertetrahedral T6 cluster and their size-dependent Mn2+-related photoluminescence propertyThe mixed metal strategy,in combination with high-charge-density-organic-amine-assisted crystallization strategy successfully broke through the size limit of metal chalcogenide supertetrahedral Tn clusters,and obtained the so-far largest one(T6-ZnInS,[Zn25In31S84]25-)via precise control of ?/? valence metal ratio.The T6-ZnInS cluster was used as an effective structural model for studying the size-dependent Mn2+-related red emission.It was found that the size of the host material changed the coordination environment of Mn2+ and affected its photoluminescence performance.This study provides innovative theoretical support for the systematic study of the size effect of II-VI semiconductor nanocrystals.2.Synthesis of zinc-based chalcogenide supertetrahedral T4 cluster and effect of intercluster connections on Mn2+-related photoluminescence propertyTwo structurally similar two-dimensional framework chalcogenides were synthesized under solvothermal conditions,and the in-situ Mn2+ doped ones were also created.They are both constructed by supertetrahedral T4 cluster as building blocks,but their assembly modes of intercluster are different.It is the first time to establish that the structural difference of the host material has been a significant impact on the coordination environment of Mn2+,which reveal that the intercluster torsion stress is also an important factor in the regulation of Mn2+-related red emission.3.Precise europium doping in discrete zinc-based chalcogenide supertetrahedral T4 cluster for photoluminescence propertiesA micrometer-sized crystal composed of discrete supertetrahedral T4-MInS(M=Zn,Cd)clusters was obtained via the solvothermal method and the in-situ Eu2+-doped one was also created.The Eu2+-doped material changed the band gap structure of the host and emitted Eu2+-related red broadband emission.This work opens up a new research direction for the development and innovation of cluster-based semiconductor materials with dopant-related optical properties.