Eu based Coordination Polymers: Ligand-Dependent Morphology and Photoluminescence Properties
Published on: 2018-03-13
A facile template-free solvothermal strategy has been developed to synthesize Eu(III)-based coordination polymer (CP) hollow spheres, using N, N-dimethylformamide (DMF) as a solvent and 2-aminoterephthalic acid (H2 ATPA) as a ligand. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental analyses (EA), Fourier transform infrared (FT-IR), Brunauer−Emmett−Teller (BET), and thermogravimetric analysis (TGA). SEM and TEM results show that the Eu-ATPA hollow microspheres have diameters of 200–400 nm and a thickness of about 15–30 nm. Besides, the photoluminescence (PL) properties of the Eu-ATPA hollow microspheres have been investigated in 100-300 K. Results show that the luminescence intensity of Eu-ATPA hollow microspheres decreases dramatically with the increase of temperature between 100 K and 300 K. To investigate the ligand effect on luminescence properties and morphology of the products, a series of Eu-based CPs built from 1,4-benzenedicarboxylate (BDC) and its derivatives have been fabricated. The results demonstrate that the morphologies of the products are sharply different from each other, indicating that their morphologies are ligand-dependent. The emission spectra, quantum yields, and the fluorescence decay curves reveal that the product has the strongest fluorescence intensity when BDC was used as the ligand. Moreover, the luminescence intensity of the products built from electron-withdrawing groups substituted BDC is stronger than those built from electron-donating groups substituted BDC. The order of the fluorescence lifetime and measured photoluminescence quantum yield (PLQY) of the samples is fundamentally the same as the order of the fluorescence intensity.