Energy transfer mechanism of carboxymethyl chitosan-Eu³⁺/Tb³⁺ complex materials and application in multicolor LED

Biological macromolecules had been studied as ligands in recent years, which not only give the complexes excellent polymer properties, but also have many advantages such as biodegradability. Carboxymethyl chitosan (CMCh) is excellent biological macromolecular ligand because of its abundant active amino and carboxyl groups, and it can smoothly transfer energy to Ln³⁺ after coordinating. To further study the energy transfer mechanism of CMCh-Ln³⁺ complexes, CMCh-Eu³⁺/Tb³⁺ complexes with different Eu³⁺/Tb³⁺ ratios were prepared by using CMCh as a ligand. The morphology, structure, and properties of CMCh-Eu³⁺/Tb³⁺ were characterized and analyzed by infrared spectroscopy, XPS, TG and Judd-Ofelt theory, thus the chemical structure of CMCh-Eu³⁺/Tb³⁺ was determined. The mechanism of energy transfer was explained in detail, also the Förster resonance transfer model is confirmed, and the hypothesis of energy transfer back was verified by the characterization and calculation methods of fluorescence spectra, UV spectra, phosphorescence spectra and fluorescence lifetime. Finally, CMCh-Eu³⁺/Tb³⁺ with different molar ratios were used to prepare a series of multicolor LED lamps, and it extends the application range of biological macromolecules as ligands.