Luminescent properties and ratiometric optical thermometry of Ln-BDC-F4 compounds

Green Ultrasound-Assisted Synthesis of Rare-Earth-Based MOFs

Rare-earth (RE)-based metal organic frameworks (MOFs) are quickly gaining popularity as flexible functional materials in a variety of technological fields. These MOFs are useful for more than just conventional uses like gas sensors and catalyst materials; in fact, they also show significant promise in emerging technologies including photovoltaics, optical, and biomedical applications. Using yttrium and europium as ionic host centres and dopants, respectively, and 1,3,5-benzenetricarboxylic acid (H3-BTC) as an organic linker, we describe a simple and green approach for the fabrication of RE-MOFs. Specifically, Y-BTCs and Eu-doped Y-BTCs MOFs have been synthesised in a single step using an eco-friendly method that makes use of ultrasound technology. To establish a correlation between the morphological and structural properties and reaction conditions, a range of distinct reaction periods has been employed for the synthetic processes. Detailed analyses of the synthesised samples through powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared spectroscopy (FT-IR) have confirmed the phase formation. Furthermore, thermal analyses such as thermogravimetric analysis (TGA) have been employed to evaluate the thermal stability and structural modifications of the Y-BTC and Eu-doped Y-BTC samples. Finally, the luminescent properties of the synthesised samples doped with Eu3+ have been assessed, providing an evaluation of their characteristics. As a proof of concept, an Eu-doped Y-BTC sample has been applied for the sensing of nitrobenzene as a molecule test of nitro derivatives.

3-Pyridylacetic-Based Lanthanide Complexes Exhibiting Magnetic Entropy Changes, Single-Molecule Magnet, and Fluorescence

Four complexes from lanthanides, 3-pyridylacetate, and 1,10-phenanthroline, formulated as [Ln2(3-PAA)2(μ-Cl)2(phen)4](ClO4)2 [Ln = Gd(1), Dy(2), Eu(3), Tb(4), 3-PAA = 3-pyridylacetic acid, phen = 1,10-phenanthroline], were obtained. The four compounds were characterized by IR spectra, thermogravimetric analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. Compounds 1-4 are isomorphous, and they have a dinuclear structure. Magnetic studies reveal that 1 shows the magnetocaloric effect with -ΔS m max = 19.03 J kg-1 K-1 at 2 K for ΔH = 5 T, and 2 displays a field-induced single-molecule magnet with U eff = 19.02 K. The photoluminescent spectra of 3 and 4 exhibit strong characteristic emission, which demonstrate that the ligand-to-EuIII/TbIII energy transfer is efficient.

Synthsis and characterization of Tb3+/Eu3+ complexes based on 2,4,6-tris-(4-carboxyphenyl)-1,3,5-triazine ligand for ratiometric luminescence temperature sensing

By choosing C3 symmetric 2,4,6-tris-(4-carboxyphenyl)-1,3,5-triazine (TCTZ) as the ligand, a series of lanthanide metal-origanic complexes Tb_1-xEu_x-TCTZ(DMF)·2H₂O(x = 0, 0.01, 1) have been successfully synthesized via solvothermal reaction. The complexes present intense emission although with coordinationofwater molecules. The temperature-dependent photoluminescent (PL) properties of Tb-TCTZ is investigated both in terms of emission intensity and lifetime in order to establish their potentials as luminescent themometers. It shows excellent responseto temperature from 303 to 403 K and exhibits the maximum relative sensitivity(S_r) as high as 5.36% K^-1 at 403 K. Tb_0.99Eu_0.01-TCTZ is evaluated for application as ratiometric luminescence thermometers, which exhibits high sensitivity to temperature in range of 303-403 K, with the maximum absolute sensitivity (S_a) and S_r as 5.16% and 3.22% K^-1 respectively. The obtained maximum sensitivities in this study is superior to many materials reported. Moreover, the emission color changes from green at 303 K to red at 403 K, so that it is also suitable to act as colorimetric luminescent probes.

How does the ligand affect the sensitivity of the luminescent thermometers based on Tb-Eu complexes

Theoretical description of a four-level system for luminescent thermometry was proposed. Based on this description, the sensitivity was proved not to exceed Sr =|E23 - E12|/T2, where T is the temperature and |E23 - E12| is the absolute energy difference between the excited state energy gaps. The analysis was verified for the terbium-europium coordination compounds, the most studied class of four-level thermometry systems, which revealed that most of the examples fall within either this theory or represent three-level systems, where the ligand is not involved in the thermally-activated processes. From this description, it follows that the highest Sr can be reached either when the triplet state is not involved or when the ligand triplet state is very high, which in the case of terbium-europium coordination compounds means exceeding 26 800 cm-1.

Eu(III) complex based on nonsteroidal anti-inflammatory drugs loxoprofen as the ligand: A novel low-toxic luminescent material for cell imaging

Eu(III) 2-{4-[(2-oxocyclopentyl)methyl]phenyl}propanoic acid complex (Eu-LPF), a novel low-toxic luminescent material based on energy transfer between the LPF ligand and Eu³⁺ ion, was synthesized and characterized by means of elemental analysis, thermogravimetric analyses, and FT-IR spectra. The spectroscopic properties of Eu-LPF were studied using UV-vis absorption spectroscopy and steady/transient state luminescence spectroscopy. Furthermore, the cytotoxicity of Eu-LPF on MCF-7 cells was investigated by MTT assay and flow cytometry. Its biocompatibility and utilization for cell imaging were studied as well. The results showed that Eu-LPF exhibited favorable luminescence properties, low toxicity and good biocompatibility, which endowed Eu-LPF with a potential capability for bioimaging and optical detection.