Construction, Characterization, and Photoluminescence of Mesoporous Hybrids Containing Europium(III) Complexes Covalently Bonded to SBA-15 Directly Functionalized by Modified β-Diketone

Abstract

Novel organic−inorganic mesoporous luminescent hybrid materials were prepared by linking the binary and ternary Eu3+ complexes to the functionalized ordered mesoporous SBA-15 with the modified 1-(2-naphthoyl)-3,3,3-trifluoroacetonate (NTA) by co-condensation of tetraethoxysilane (TEOS) in the presence of Pluronic P123 surfactant as a template. 1-(2-Naphthoyl)-3,3,3-trifluoroacetonate (NTA) grafted to the coupling agent 3-(triethoxysilyl)propyl isocyanate (TEPIC) was used as the precursor for the preparation of mesoporous materials. SBA-15 consisting of the highly luminescent ternary complex Eu(NTA)3bpy covalently bonded to the silica-based network, which was designated as Eu(NTA−SBA-15)3bpy, was obtained by introducing EuCl3 and 2,2'-bipyridine (bpy) complex into the hybrid material via a ligand-exchange reaction. In addition, for comparison, SBA-15 doped with Eu(NTA)3·2H2O and Eu(NTA)3bpy complexes and SBA-15 covalently bonded with the binary Eu3+ complex with NTA ligand were also synthesized, denoted as Eu(NTA)3/SBA-15, Eu(NTA)3bpy/SBA-15, and Eu(NTA−SBA-15)3, respectively. The luminescence properties of these resulting materials were characterized in detail, and the results reveal that they all have high surface area, uniformity in the mesostructures, and crystallinity. The efficient intramolecular energy transfer in mesoporous material Eu(NTA−SBA-15)3bpy mainly occurs between the modified ligand NTA−Si and the central Eu3+ ion. Furthermore, Eu(NTA−SBA-15)3bpy exhibited the characteristic emission of Eu3+ ion under UV irradiation with higher 5D0 luminescence quantum efficiency than the pure Eu(NTA)3bpy complex and the other materials. Thermogravimetric analysis on the mesoporous material Eu(NTA−SBA-15)3bpy indicated that the thermal stability of the complex was improved as it was covalently bonded to the host SBA-15 matrix.