An europium(III) metal-organic framework as a multi-responsive luminescent sensor for highly sensitive and selective detection of 4-nitrophenol and I- and Fe3+ ions in water

A luminescence sensor based on an europium(III)-based lanthanide-organic framework, [Eu(BCB)(DMF)]·(DMF)_1.5(H₂O)₂ (1), was synthesized via a solvothermal method using 4,4',4''-benzenetricarbonyltribenzoic acid (H₃BCB) as a bridging ligand. Single-crystal X-ray diffraction indicates that Eu centers are eight-coordinated with a trigonal dodecahedron and a square antiprismatic configuration, and adjacent Eu atoms are bridged by BCB organic linkers to form a 3D rod-packing structure. Photoluminescence studies show that compound 1 emits bright red luminescence and behaves as a multi-responsive luminescent sensor toward 4-nitrophenol (4-NP) and I^- and Fe³⁺ ions in water with high sensitivity, selectivity and low detection limits. Furthermore, the possible luminescence sensing mechanisms were also investigated by PXRD analysis, UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The recognition mechanism for 4-NP and I^- ions can be attributed to the competition absorption and that for Fe³⁺ ions is considered to be a multi-quenching mechanism dominated by competition absorption. This study demonstrates that the lanthanide-based MOF might be a promising candidate for the detection of 4-NP and I^- and Fe³⁺ ions in aqueous medium.

Simple fluorescence optosensing probe for spermine based on ciprofloxacin-Tb3+ complexation

We developed a facile detection method of spermine based on the fluorescence (FL) quenching of the ciprofloxacin-Tb3+ complex, which shows astrong green emission. Ciprofloxacin (CP) makes efficient bondings to Tb3+ ion as a linker molecule through carboxylic and ketone groups to form a kind of lanthanide coordination polymer. The addition of spermine that competes with Tb3+ ions for the interaction with CP due to its positive charge brings about weakened coordination linkage of CP and Tb3+. The probe exhibited high sensitivity, selectivity, and good linearity in the range of 2-180 μM with a low limit of detection of 0.17 μM. Moreover, we applied this method on the paper strip test (PST), along with the integration of a smartphone and Arduino-based device. The practical reliability of the developed probe was evaluated on human serum samples with acceptable analytical results.

Luminescent Properties of Lanthanoid-Poly(Sodium Acrylate) Composites: Insights on the Interaction Mechanism

The interaction between polyelectrolytes and metal ions is governed by different types of interactions, leading to the formation of different phases, from liquid state to weak gels, through an appropriate choice of metal ion/polyelectrolyte molar ratio. We have found that lanthanide ions, europium(III) and terbium(III), are able to form polymer composites with poly(sodium acrylate). That interaction enhances the luminescent properties of europium(III) and terbium(III), showing that Eu³⁺/poly(sodium acrylate) (PSA) and Tb³⁺/PSA composites have a highly intense red and green emission, respectively. The effect of cations with different valences on the luminescent properties of the polymer composites is analyzed. The presence of metal ions tends to quench the composite emission intensity and the quenching process depends on the cation, with copper(II) being by far the most efficient quencher. The interaction mechanism between lanthanoid ions and PSA is also discussed. The composites and their interactions with a wide range of cations and anions are fully characterized through stationary and non-stationary fluorescence, high resolution scanning electronic microscopy and X-ray diffraction.

Synthesis, crystal structures and, magnetic and photoluminescence properties of lanthanide-based metal-organic frameworks constructed with 2,5-dihydroxybenzene-1,4-dicarboxylic acid

Four new lanthanide(iii) coordination polymers (1–4) have been synthesized by using 2,5-dihydroxybenzene-1,4-dicarboxylate (Dhbdc, C₈H₆O₆²⁻) as a ligand and characterized by elemental analysis, infrared spectroscopy, TGA-DSC (Thermogravimetric Analysis-Differential Scanning Calorimetry) and single crystal X-ray diffraction studies. The isolated complexes include; [Ce(Dhbdc)(H₂O)₃Cl]_n (1) and [Ln(Dhbdc)_1.5(H₂O)₂]_n·3n(C₂H₆O)·nH₂O [Ln = Eu (2), Gd (3) and Tb (4)]. The structural analysis reveals that compound 1 is a two-dimensional polymer in which the cerium atoms are coordinated by six oxygen and two bridging chloride ions adopting a dodecahedral geometry. The compounds 2–4 are isomorphous and their extended structures consist of three-dimensional supramolecular frameworks encapsulating [001] channels occupied by the guest water and ethanol molecules. The metal atoms in 2–4 exhibit a square antiprism geometry. All these compounds have O–H⋯O hydrogen bonds originating from the coordinated water and solvent molecules that help to consolidate the structures. The compounds 1, 3 and 4 were investigated for magnetic properties and they exhibited weak antiferromagnetic coupling interactions between the lanthanides as per the Curie Weiss law. Anisotropic nature of 3 and 4 has been depicted as per magnetization versus field plots. Complex 4 behaves as a soft magnetic material as compared to 3. The luminescence studies indicate that compounds 2, 3 and 4 show ligand-centred fluorescence, which is significantly enhanced in the case of 4.

Four new lanthanide(iii) coordination polymers (1–4) have been synthesized by using 2,5-dihydroxybenzene-1,4-dicarboxylate as a ligand and investigated for magnetic and photo-luminescence properties.

Regioisomeric monopyridine-functionalized triarylethene: small AIEgens with isomeric effect and an efficient platform for the selective and sensitive detection of Pd2+ and Fe3+

Regioisomeric monopyridine functionalized triarylethenes are established as small AIEgens. These compounds are utilized to detect Fe⁺³ and Pd⁺² selectively in nM range. The detection is further extended for the on-site applications.

Multi-functional lanthanide-CPs based on tricarboxylphenyl terpyridyl ligand as ratiometric luminescent thermometer and highly sensitive ion sensor with turn on/off effect

The binary compound Ln-CP Tb_0.897Eu_0.103tcptpy has been developed as a ratiometric luminescent thermometer. Its relative sensitivity can reach up to 8.41% K⁻¹ in the 305 to 340 K range.

Synthesis, Crystal Structures and Photoluminescent Properties of One-Dimensional Europium(III)- and Terbium(III)-Glutarate Coordination Polymers, and Their Applications for the Sensing of Fe3+ and Nitroaromatics

Two lanthanide–glutarate coordination polymers, viz. : {[Eu(C₅H₆O₄)(H₂O)₄]Cl}_n, (1) and [Tb(C₅H₇O₄)(C₅H₆O₄)(H₂O)₂]_n, (2) have been synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and X-ray crystallography. In 1, the Eu(III) ions are coordinated by four O atoms from two bidentate chelating carboxylate groups, one O atom from a bridging carboxylate group and four O atoms from water molecules adopting an EuO₉ distorted tri-capped trigonal prismatic coordination geometry. In 2, the Tb(III) ions are coordinated by six O atoms from three bidentate chelating carboxylates, one O atom from a bridging carboxylate and two O atoms from water molecules to generate distorted tri-capped trigonal prismatic TbO₉ polyhedron. In both compounds, the metal polyhedra share edges, producing centrosymmetric Ln₂O₂ diamonds, and are linked into [001] chains by bridging glutarate di-anions. The crystal structures are consolidated by O–H···O and O–H···Cl hydrogen bonds in 1, and O–H···O hydrogen bonds in 2. Compound 1 exhibits a red emission attributed to the ⁵D₀ → ⁷F_J (J = 1–4) transitions of the Eu(III) ion, whereas 2 displays green emission corresponding to the ⁵D₄ → ⁷F_J (J = 0–6) transitions of the Tb(III) ion. Both the compounds exhibit high sensitivity and selectivity for Fe³⁺ ions due to luminescence quenching compared with other metal ions, which include; Na⁺, Mg²⁺, Al³⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Zn²⁺ and Cd²⁺. Compounds 1 and 2 also show high luminescence quenching sensitivity for 4-nitrophenol over the other aromatic and nitroaromatic compounds, namely; bromobenzene, 1,3-dimethylbenzene, nitrobenzene, 4-nitrotolune, 4-nitrophenol, 2,6-dinitrophenol and 2,4,6-trinitrophenol.

Synthesis, Thermal, Structural Analyses, and Photoluminescent Properties of a New Family of Malonate-Containing Lanthanide(III) Coordination Polymers

Five new Lanthanide(III) complexes of malonic acid (HOOC-CH2-COOH); {[Gd(C3H2O4)(H2O)4]·NO3} n (1), {[Tb(C3H2O4)(H2O)4]·NO3} n (2), {[Ho(C3H2O4)(H2O)4]·NO3} n (3), [Er(C3H2O4)(C3H3O4)(H2O)2] n (4), and {[Eu2(C3H2O4)2(C3H3O4)2(H2O)6]·4H2O} n (5) were synthesized and characterized by elemental, infrared spectral, and thermal analyses. The structures of compounds 1-5 were determined by single crystal X-ray diffraction technique. The X-ray analysis reveals that compounds 1, 2, and 3 are isostructural and crystallized in the orthorhombic space group Pmn21. The lanthanide(III) ions are coordinated by four carboxylate and four water oxygen atoms adopting a distorted square antiprism geometry. The LnO8 square antiprisms are linked into infinite layers by malonate (C3H2O 4 2 - ) dianions sandwiching sheets of nitrate counter ions. Compound 4 contains ErO8 square antiprisms linked into a two-dimensional network by hydrogen malonate (C3H3O 4 - ) anions and malonate dianions. The europium complex, 5 is dinuclear having the two europium(III) ions (Eu1 and Eu2) bridged by carboxylate groups of hydrogen malonate ligands. The europium ions in 5 are nine-coordinate and exhibit a distorted monocapped square antiprism geometry. All the structures are consolidated by O-H⋯ O hydrogen bonds. The photoluminescence spectra of 1-5 exhibit characteristic emissions in the visible region. The IR spectra and thermal data are consistent with the structural results. The room-temperature effective magnetic moments for 1-4 are in good agreement with those expected for the free ions, while the data for 5 indicates that low-lying excited states contribute to the observed moment. The compound 1 was further subjected to quantum computational calculations to explore its optoelectronic properties including; density of states (DOS), dielectric function, refractive index, extinction coefficient, and absorption spectrum, to highlight the possible applications of such materials in the optoelectronics.

A pillared-layer strategy to construct water-stable Zn–organic frameworks for iodine capture and luminescence sensing of Fe3+

Two water-stable pillared-layer MOFs exhibiting sorption behavior towards iodine and luminescence sensing of Fe³⁺ have been successfully constructed.

A water-stable 3D Eu-MOF based on a metallacyclodimeric secondary building unit for sensitive fluorescent detection of acetone molecules

A Eu-MOF with high water stability constructed using a systematic metallacyclodimeric motif as a potential chemical sensor for acetone is reported.

An anionic layered europium(iii) coordination polymer for solvent-dependent selective luminescence sensing of Fe3+ and Cu2+ ions and latent fingerprint detection

An anionic layered coordination polymer [Eu(BTEC)0.5(HCOO)(H2O)2] (1) has been successfully synthesized via a solvothermal method (H4BTEC = 1,2,4,5-benzenetetracarboxylic acid, HCOOH = formic acid). Compound 1 possesses two-dimensional layers, which further generate a three-dimensional supramolecular network by hydrogen bonds existing between carboxylic oxygen, formate anion and H2O molecules of two adjacent layers. Interestingly, 1 shows high luminescence quenching efficiency upon addition of Fe3+ ions when it was dispersed in water even in the presence of interfering ions such as Na+, Ag+, Ca2+, Cd2+, Co2+, Cu2+, Mg2+, Mn2+, Zn2+ and Al3+. When dispersed in DMSO solution, 1 displays excellent sensitivity and selectivity towards both Cu2+ and Fe3+ ions. Possible quenching mechanisms for detection of Fe3+ and Cu2+ ions were carefully investigated and proposed based on a dynamic quenching process, static quenching process and fluorescence inner filter effect. Moreover, the as-prepared particles can be used for visualizing latent fingerprints on various substrates. These results indicate that a Eu(iii)-based coordination polymer has great potential in detection and security application.

Two luminescent lanthanide–organic frameworks containing bithiophene groups for the selective detection of nitrobenzene and Fe3+

Two isostructural lanthanide–organic frameworks containing bithiophene groups can be used as fast-response fluorescent probes for the sensitive detection of nitrobenzene and Fe³⁺ ions through fluorescence quenching.