Rare Earth Complexes/Preparation And Luminescentof POSS-Based Hybrid Materials

Rare earth complexes with the emissions in the near-infrared region have a wide range of applications in the field of photoluminescence due to their attractive features,such as large stock shift,emission line spectrum,ideal excitation and emission wavelengths,long fluorescence lifetime.However,rare earth ions have weak luminescence and poor stability,which limit their applications in various fields.In this paper,an organic-inorganic hybrid material of polyhedral oligomeric silsesquioxanes?POSS?was linked with rare earth complexes by copolymerization method to reduce the aggregation effect between rare earth complexes and improve the luminescence intensity of rare earth complexes.The main work is shown as follows:Firstly,8-hydroxyquinoline was used to synthesize 8-hydroxyquinoline-5-formaldehyde,whichwas modified by POSS andto synthesize ligand?Q-POSS?.The modified ligand?Q-POSS?was characterized by ¹HNMR?MS?and FTIR spectroscopy.The lowest triplet energy level of the ligand was determined by low temperature phosphorescence spectroscopy at 21322 cm^-1.Secondly,a series of rare earth complexes were synthesized,that is,POSS modified8-hydroxyquinoline?Q-POSS?and 8-hydroxyquinoline?Q?were used as the ligands for the preparation of Ln?Q-POSS?₃ and LnQ₃(Ln=Er³⁺?Yb³⁺?Nd³⁺).The structures and components of rare earth complexes were characterized by infrared spectroscopy and elemental analysis.The absorption spectra of the ligands and rare earth complexes were determined by UV-visible spectroscopy.The excitation and emission spectra of rare earth complexes were determined by high resolution spectroscopy.Asaresult,the emission intensity of the Ln?Q-POSS?₃ was enhanced obviously compared with that of the unmodified counterparts LnQ₃.For Er³⁺,the emission intensity of the modified rare earth complexes was about 4 times that of the unmodified complexes;for Nd³⁺,the emission intensity of the modified rare earth complexes was about 5 times that of the unmodified complexes;for Yb³⁺,the emission intensity of the modified rare earth complexes was about1 times that of the unmodified complexesBesides,during the experiment,it was discovered by accident that POSS?AIPOSS?showed blue fluorescence after heat treatment in tetrahydrofuran solvent.Fluorescence spectroscopy was used to determine the emission peak at 430 nm.Through controlled trials in which AIPOSS with amino group and OIPOSS without amino group were refluxed under the same condition to determine that intermolecular hydrogen bonds were not the cause of enhanced luminescence.And then,their chemical structures was characterized by²⁹SiNMR spectroscopy,FTIR spectroscopy.High resolution XP spectrum of Si 2p region determined that peak at 102.0 eV is consistent with O-Si-C species.So,we think that this unusual luminescence is most likely caused by the agglomeration between the POSS molecule.