Eu-modification of luminescent hybrid bimodal mesoporous silicas with various anions (NO3, CH3COO,and Cl)

In order to enhance the intensity of luminescent hybrid bimodal mesoporous silica (LHMS), the rare earth Eu³⁺ ion was employed as an enhancer to modify 1,8-naphthalic anhydride (NA) molecules. The modified LHMS were prepared with various anions of europium salts including Cl⁻, NO₃⁻, and CH₃COO⁻. The structure and photoluminescence properties of the obtained samples were characterized by XRD, TEM, N₂-adsorption/desorption, FT-IR, TGA, ICP-OES, and PL measurements. The results showed that the bimodal mesoporous system of BMMs could be preserved after functionalization via grafted Eu³⁺-modified NA molecules onto mesoporous matrix. However, the structure parameters and textural properties of resultant LHMS series were obviously influenced by the anions volume. Meanwhile, the luminescent performances of LHMS series were seriously impacted by both of the binding force between Eu³⁺ and various anions and steric hindrance of the anions, resulting in the intensity of emission peak of obtained LHMS series declining as following order: LHMS-EN (NO₃⁻) > LHMS-EA (CH₃COO⁻) > LHMS-EC (Cl⁻). Finally, the related mechanism was discussed in-depth.