Novel multi-color photoluminescence emission phosphors developed by layered gadolinium hydroxide via in situ intercalation with positively charged rare-earth complexes

Abstract

The design of multi-color phosphors has aroused great interest for practical optical applications. Herein, for the first time, the stable positively charged Eu(III) and Tb(III) complexes EuL and TbL (L = 2,2′-(4-(2-ethoxyethoxy)pyridine-2,6-diyl)bis(4,5-dihydrooxazole)) have been successfully intercalated in situ into the gallery of layered gadolinium hydroxide (LGdH) utilizing chelation of picolinic acid (pa) anions via ligand exchange reaction. In particular, the resulting hybrid phosphors (LGdH-pa-Eu_1−xTb_xL) exhibit multi-color emissions by simply fine-tuning the molar ratio of Eu(III)/Tb(III), which show red and green primary colors, as well as intermediate colors excited at 310 nm. The luminescence spectra, decay time, and low-temperature phosphorescence spectra analysis indicate that other than the intramolecular energy transfer (ET) process from ligand to RE(III) and intermolecular ET process from Tb(III) to Eu(III), the expected and interesting interaction between host (LGdH) and guest pa anions was also observed, which dramatically enhanced the absorption cross section of pa anions. Finally, a blue emission component 4,4′-distyrylbiphenyl sodium sulfonate (Tinopal CBS) was further introduced into the hybrid material LGdH-pa-Eu_0.2Tb_0.8L, to provide white light emission under the 330 nm excitation. In addition, to determine the potential of these hybrid phosphors in various applications, transparent and multi-color emission composite film devices have been fabricated with poly(methyl methacrylate) (PMMA) using the solvent-casting method.