Studies On Intercalation Assembly And Property Modulation Of The Luminescent Materials Based On Layered Rare-earth Hydroxides

Stacking two-dimensional layered materials are attracting intense interest because of their structural anisotropy and the fascinating properties that result. At present, these materials can exchange anions in research and explorationhas has been a significant development. In the study of many functional layered materials, Layered rare-earth hydroxides (LRHs), which have the general composition RF2(OH)5X·nH2O (where RE=rare-earth elements and X=anion), are a new group of important inorganic layered matrices. The general structure of LRHs is similar to that of classical layered double hydroxides (LDHs), which consist of alternating positively charged hydroxocation layers and charge-compensating anion layers. Applications using this unique combination of rare-earth element chemistry and layered materials include ion-exchange, photoluminescence, catalysis, and biomedical devices. Not only are those, these materials also of academic importance, serving as an ideal model for studying the cationic size effect on structure stability associated with lanthanide contraction. In many functional features study, as a novel class of inorganic layered functional materials with two-dimensional layered structure, The rich interlayer chemistry, adjustable composition and unique luminescence properties of rare earth elements of LRHs can be used to achieve additional tunability to create numerous opportunities for designing multicolor phosphors. The rich interlayer chemistry, adjustable composition and unique luminescence properties of rare earth elements of LRHs can be used to achieve additional tunability to create numerous opportunities for designing multicolor materials.Up to now, these materials in synthesis strateg, composition diversity, structural features and applications has been a significant development.The dissertation includes following four chapters:Chapter 1:A brief review of progress of lanthanide luminescent hybrid materials and layered rare-earth hydroxides hybrid materials was summarized.Chapter 2:Intercalation assembly of optical hybrid materials based on layered terbium hydroxide hosts and organic sensitizer anions guests.This chapter focuses on the intercalation assembly of optical hybrid materials based on the layered terbium hydroxide (NO3-LTbH) hosts and organic divalent carboxylic sensitizer anion guests by a hydrothermal process. The studies on the interactions between hosts and guests indicate that the type and arrangement of organic guests in the layer spacing of the LTbH hosts can make a difference in the luminescence of the hybrid inorganic-organic materials. In addition, the effects of intercalation conditions on luminescence were also investigated.Chapter 3:Dramatically enhanced luminescence of layered terbium hydroxides as induced by the synergistic effect of Gd3+ and organic sensitizersHost-guest chemistry allows the engineering of new functional materials with tunable properties. This study focuses on layered terbium hydroxides (NO3-LTbH) codoped with Gd3+(N03-LTbH:Gd), which were prepared using the hydrothermal method and successfully modified using sensitizers (H2L4). Luminescence studies showed that compared with the NO3-LTbH precursor the sensitizer-modified NO3-LTbH:Gd exhibited high luminescence intensity and high luminescence quantum efficiency (0= 33%). This performance results from the synergistic effect of codoped Gd3+ and intercalated sensitizers in the organic-inorganic hybrid materials, which led to stronger luminescence properties, and synergistic effect on the enhancement of Tb3+ luminescence was investigated by the spectroscopic characteristics, UV-vis absorption spectrum, lowtemperature phosphorescence, and crystal structures of the layered rare-earth hydroxides. Studies demonstrate that the mechanism for synergistic effect of significant enhancement of Tb3+luminescence is mainly caused by Gd3+ inducing a cascaded energy transfer from the host to Tb3+ via organic sensitizers. The very interesting thing is that LTbH:Gd has multiple roles, including energy-transfer bridges that connect the sensitizers and Tb3+(in host) to enhance the characteristic emission of Tb3+.Chapter 4:Facile fabrication of color-tunable and white light emitting nano-composite films based on layered rare-earth hydroxides.A novel class of color-tunable and white light emitting hybrid phosphors based on efficient energy-transfer between Tb3+ and Eu3+ and the rich interlayer chemistry of the layered rare-earth hydroxides (LRHs) were successfully designed and assembled. Besides, flexible luminescent materials have attracted an extensive amount of interest owing to their broad application in optoelectronic devices. Therefore, novel transparent color-tunable nano-composite film devices have been fabricated facilely by using a solventcasting method based on the compatibility between the LRH hybrid phosphors modified by organic sensitizers and poly(methyl methacrylate) (PMMA) in this paper. A full interpretation to the interaction between the host and guest of the hybrid phosphors was given; the luminescence intensity of hybrid phosphors was significantly enhanced through a cascaded energy-transfer mechanism from the host to Tb3+via organic sensitizers, precisely as induced by the synergistic effect of host and guest. And in the nano-composite films, PMMA acted as a co-sensitizer and improved the optical properties of hybrid phosphors, thus the photoluminescence quantum yield of the films more than doubled compared with that of hybrid phosphors. These findings may open up new avenues for the exploration of hybrid phosphors based on LRHs and fabrication of color-tunable emitting nano-composite films, which can serve as promising materials for use in various optical devices. And the proposed facile synthetic strategy can be easily extended to the synthesis of other highly efficient rare-earth hybrid phosphors.