Study Of Energy Transfer And White Light Communication By Metal Organic Frameworks

Long range energy transfer and exciton migration plays an important role in artificial photosynthesis and light-harvesting system.Previous studies on through-space energy transfer is focused on Forster type singlet excited state and Dexter type triplet excited state,leaving the more important through-bond superexchange energy transfer unexplored.Metal-Organic Frameworks(MOFs)represent a class of hydrid porous materials that are constructed from organic ligands and metal ion nodes.MOF is used to design model system for energy transfer study thanks to its ordered network and chemical tunability.Coumarin 343 and Rhodanmine B are typical organic dye molecules with high molar extinction coefficients and high fluorescence quantum yields.They can serve as energy acceptors for energy transfer study.In this thesis,Zr/Hf-MOLs was synthesized by reacting H3BTB(4,4',4"-benzene-1,3,5-triyl-tri-benzoic acid)with metal ions Zr4+ and Hf4+.We prepared a series of Zr/Hf-BTB&TATB MOLs and Coumarin 343-Zr/Hf-BTB hybrids by doping H3TATB in the network and loading Coumarin 343 on the MOLs via carboxylate exchange.We have observed identical energy transfer rates in a Zirconium based MOL and an isostructural Hafnium based MOL as revealed by measuring the quenched fluorescence of TATB-doped MOLs or the ratiometric emissions of MOLs modified with coumarin-3 43 on the surface,consistent with the dominance of through-space Forster-type energy transfer.Visible-light communication(VLC)is a technology to use everyday lighting for wireless communication.As compared to radio-frequency based technologies such as Wi-Fi or Bluetooth,it provides supplementary solutions when high speed,high security,low radio interference,low cost and bio-friendliness are needed in the information transmission.At present,the study of optical communication,mainly focused on how to improve the communication bandwidth.One way to solve this problem is to increase the intrinsic response frequency of the luminescent coating.The organic ligands of MOFs usually have short lifetimes.Moreover,dye molecules can be with short luminescent lifetimes can be loaded in the MOF channels to construct luminescent materials with multiple emission bands.We used 9,10-anthacenyl bis(benzoic acid)(H2DBA)as ligands to construct a MOF,which shows bright blue-light-emitting and high quantum yield.We achieved a white-light-emitting LED materials by encapsulating a yellow-emitting Rhodamine B in the cavity of blue-emitting MOFs.The restriction of dye molecules in the cavity and energy transfer from ligands to dyes can eliminate the aggregation-caused quenching(ACQ).Moreover,we realized a fast white-light communication using this hybrid materials as the phosphor.