[Effect of host MCM-41 on the luminescence properties of Tb(aspirin)3phen]

Highly ordered mesoporous material MCM-41A(after calcination) and MCM-41B (before calcination) were synthesized in ethylenediamine (EDA) medium at room temperature, and the rare earth complexes Tb(aspirin)3phen which had been heat treated as an active optical guest was incorporated into the one-dimensional channels of MCM-41A(B). The photoluminescence properties of the organic/inorganic composites Tb(aspirin)3phen-MCM-41A(B) were investigated based on the analyses of excitation and emission spectra to provide information about the relationship between the organic host and the inorganic optical guest. The results from the characterization of PL show that the wide excitation band in the range of 240-375 nm of Tb(aspirin)3 phen is assigned to the carbonyl group n --> pi* transition absorption, benzene ring pi --> pi* transition absorption of aspirin, and phenanthrene absorption of phen. As no excitation band appears in ultraviolet ranges, the characteristic emission peaks of Tb3+ in the emission spectra are related to antenna effect Relative to the excitation band of Tb(aspirin)3phen, the excitation band of Tb(aspirin)3phen-MCM-41B and Tb(aspirin)3phen/MCM-41A splits obviously, and only one narrow excitation peak at 353 nm appears in the excitation spectrum of Tb(aspirin)3 phen-MCM-41A. The excitation bands of Tb(aspirin)3 phen-MCM-41B and Tb (aspirin)3 phen/MCM-41A at short wavelength weakens and disappears gradually, while excitation peaks at long wavelengths is enhanced gradually, and the IL/ILn ratio I, where IL is the emission intensity at 405 nm under 335 nm excitation, and I(Ln) is the emission intensity at 544 nm under 335 nm excitation, also decreases correspondingly. It is suggested that the triplet states and single states of aspirin and phen reduce with different degree after Tb(aspirin)3phen is banded with MCM-41 framework, and the effect of silicon framework on the states of phen is more than that of aspirin. The degree of the effect on the states of organic ligands is in the order of: MCM-41B external surface > MCM-41A external surface > MCM-41A inside surface. In addition, the ratio I also could indicates the degree of the effect of MCM-41 surface lattice field on the ligand energy level and the content of Tb (aspirin)3phen on the MCM-41 surface.