Europium Coordination Polymer Research Articles

A novel core–shell lanthanide coordination polymer ratiometric fluorescent probe for the ultrasensitive and visual detection of anthrax biomarker

A novel core–shell based lanthanide ratiometric fluorescent probe is designed for the rapid and sensitive detection of 2, 6-pyridine dicarboxylic acid (DPA), which is the biomarker of Bacillus anthracis. The fluorescent dye molecule 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) was encapsulated in silica nanoparticles as a reference signal and externally connected with guanine mononucleotide europium coordination polymers (Eu/GMP) as a response signal so as to construct a double-emission fluorescent sensor. The visual detection was enabled by the fluorescence color change from green to red under an UV lamp with the addition of DPA. In addition, the RGB auxiliary detection platform was built using color scanning software of smartphone. This work presents a novel and efficient method for detecting anthrax biomarkers.

A water stable europium coordination polymer based on mixed organic ligands as a luminescence sensor for the detection of an anthrax biomarker

The development of luminescence sensors capable of detecting anthrax biomarkers is crucial for preventing anthrax. In this study, a two-dimensional europium coordination polymer [Eu(dlba)(phen)·2(H2O)]n (CP-1) was prepared based on a rigid 1,10-phenanthroline (phen) and a flexible 2-(3,5-dicarboxybenzyloxy) benzoic acid (H3dlba) under the hydrothermal conditions. The CP-1 was characterized by powder X-ray diffraction, elemental analysis, thermogravimetric analysis, infrared spectroscopy, and single crystal X-ray diffraction. The CP-1 exhibits excellent water stability and thermal stability. Luminescence experiments demonstrated a high luminescence quenching efficiency (98.1 %) upon addition of the anthrax biomarker dipicolinic acid (DPA). Additionally, the sensor shows good sensitivity and a rapid response time of 30 s. The detection limit is as low as 0.12 µM, which is much lower than the infection dose of spores (60 µM). The sensor has a recovery rate of 95–105 % when tested on actual samples, indicating its potential for practical applications. The luminescence quenching effect may be due to the competitive absorption of DPA, which affects the efficiency of energy transfer from the ligands to the europium ions.

Enhancing the Circularly Polarized Luminescence of Europium Coordination Polymers by Doping a Chromophore Ligand into Superhelices.

Lanthanide-based molecular materials showing efficient circularly polarized luminescence (CPL) activity with a high quantum yield are attractive due to their potential applications in data storage, optical sensors, and 3D displays. Herein we present an innovative method to achieve enhanced CPL activity and a high quantum yield by doping a chromophore ligand into a coordination polymer superhelix. A series of homochiral europium(III) phosphonates with a helical morphology were prepared with the molecular formula S-, R-[Eu(cyampH)3-3n(nempH)3n]·3H2O (S/R-Eu-n, n = 0-5%). The doping of chromophore ligand S- or R-nempH2 into superhelices of S/R-Eu-0% not only turned on the CPL activity with the dissymmetry factor |glum| on the order of 10-3 but also increased the quantum yield by about 14-fold. This work may shed light on the development of efficient CPL-active lanthanide-based coordination polymers for applications.

Synthesis and characterization of a europium coordination polymer as a fluorescent sensor for the selective detection of PO43−, DTZ, and NFT

A new europium coordination polymer [Eu(2,3′-oba)(2,3′-Hoba)(IP)]n (Eu-CP) has been synthesized by hydrothermal reaction using 2,3′-oxbis (benzoic acid) (2,3′-H2oba) and 1H-imidazole [4,5-f] [1,10]-phenanthroline (IP). The semi-rigid ligand 2,3′-H2oba and large rigid ligand IP form a 1D chain structure of the Eu-CP, which is further stacked into a 3D supramolecular architecture through C–H⋯O and O–H⋯N hydrogen bonding. Below 400 °C, the Eu-CP does not decompose. It shows good chemical stability in common solvents and aqueous solutions with pH in the range of 3–12. The Eu-CP emits strong red luminescence, attributed to the 5D0→7FJ (J = 0–4) transitions of the Eu3+ ion. The luminescence quantum yield and lifetime are 61% and 0.94 ms, respectively. The Eu-CP has a broad absorption in the range of 200–400 nm, with a maximum excitation wavelength of 365 nm. Furthermore, Eu-CP is used as a sensor for the detection of PO43−, dimetridazole (DTZ), and nitrofurantoin (NFT) in aqueous systems, and NFT in biological samples (calf serum) based on the luminescence quenching effect. Notably, luminescent Eu-CP@film was prepared for sensing PO43−, NFT, and DTZ, which can be reused more than 20 times, facilitating a visually simple and rapid online detection platform. In addition, we also studied the luminescence quenching mechanism of Eu-CP by analytes.

Structural metamorphosis and photophysical properties of thermostable nano- and microcrystalline lanthanide polymer with flexible coordination chains

ABSTRACT Luminescent lanthanide coordination polymer crystals (LCPCs) represent an area of growing interest in materials chemistry owing to their unique and tailorable functional properties. The LCPCs provide a high level of structural tunability, including size- and morphology-dependent properties; therefore, they are promising materials for next-generation phosphors in a wide range of applications such as light emitting diodes. Here, by controlling the morphology of thermostable europium coordination polymer crystals, [Eu(hfa)3(dpbp)]n, hfa: hexafluoroacetylacetonate and dpbp:4,4’-bis(diphenyl phosphoryl) biphenyl), we realized a novel red phosphor with narrow linewidth emission (FWHM = 7.8 nm). The obtained luminescent LCPCs with unique structures were characterized by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), dynamic light scattering (DLS) and thermogravimetric analysis. Among, them, size tunable crystalline polymer spheres were found to have high internal quantum efficiency (ex., IQE = 79%) and highly thermostability (>300°C), and to exhibit dispersibility in PMMA media. The obtained results on the structural tunability of these materials can be used for the development of synthesis techniques for nanoscale materials based on crystalline lanthanide-based coordination phosphors.

Two Novel Pyrene Tetra-Sulfonate Europium Coordination Polymers: Structure Formation Mechanism Analysis and Sequential Modulation Strategy

For the purpose of broadening the understanding of the sulfonic acid coordination mechanism, a coordination system consisting of Eu(III) ion and 1,3,6,8-pyrene tetra-sulfonate (1,3,6,8-PTS) ligand was chosen as the typical research object. By step regulating the volume ratio of mixed solvents and the molar ratio of metal salts to ligands, two pyrene tetra-sulfonate europium coordination polymers, Eu6(μ6-O)(μ3-OH)8(NO3)6(1,3,6,8-H2PTS)(H2O)10 (1) and Eu(NO3)(1,3,6,8-PTS)0.5(H2O)3·0.5bipy (2), were obtained in sequence. Compound 1 shows a 1D chain-like structure interconnected with 1,3,6,8-PTS bridging ligands and rare [Eu6(μ6-O)(μ3-OH)8(NO3)6]2+ cluster nodes, while compound 2 shows a 2D layered structure. Further structural comparison with compound Eu(1,3,6,8-PTS)(H2O)7·4H2O·Hbipy (EuPTSbp-1) was discussed in detail and the structure formation mechanism was analyzed. On this basis, a sequential modulation strategy for pyrene tetra-sulfonate europium coordination polymers was proposed.

One-dimensional Europium-coordination polymer as luminescent sensor for highly selective and sensitive detection of 2,4,6-trinitrophenol

Three isostructural lanthanide coordination polymers (LnCPs), [Ln(L)6(DMF)]n {HL = 2-(2-formylphenoxy) acetic acid, Ln = Sm (1); Eu (2); Tb (3)} have been synthesized by solvothermal reaction and characterized. Single crystal analyses revealed that the architectures of these LnCPs own one dimensional chain which can be further packed into two-dimensional architectures by hydrogen bonds. Moreover, these LnCPs can offer strategically placed uncoordinated formyl groups, which may act as hydrogen-bond acceptor in the sensing of nitro explosives. Luminescence measurements reveal that LnCPs 2 and 3 exhibit strong luminescence in solid states. LnCP 2 shows quick, highly selective and sensitive detection of 2,4,6-trinitrophenol (TNP) with the high quenching constant (2.6 × 104 M−1) and low detection limit (3.39 μM), which indicates that LnCP 2 is more efficient than most of Eu-based coordination polymers for the sensing of TNP. Furthermore, LnCP 2 represents the first example of one-dimensional Eu-based sensors with formyl group as hydrogen-bonding site in the detection of TNP.

Robust Lanthanoid Picolinate-Based Coordination Polymers for Luminescence and Sensing Applications

Picolinate-based segmented dianionic ligands L12– (5-((4-carboxyphenyl)ethynyl)picolinate) and L22– (5,5′-(ethyne-1,2-diyl)dipicolinate) have been used in the synthesis of the highly robust and luminescent europium(III) coordination polymers [(CH3)2NH2][Eu(H2O)2(L1)2] (1) and [(CH3)2NH2][Eu(L2)2]·H2O·CH3COOH (2). Both 1 and 2 exhibit high selectivity for detection of nitroaromatic compounds since they act as quenchers of the Eu3+ emission. Stern–Volmer plots, using nitrobenzene as a quencher, yielded values of KSV = 150 M–1 and 160 M–1 for 1 and 2, respectively. Luminescence studies in the presence of different metal ions indicate a high selectivity for Fe3+ detection, with KSV values of 471 M–1 and 706 M–1 for 1 and 2, respectively. Both 1 and 2 possess extremely robust extended structures, leading to emissive properties that are stable in a wide pH range.

Luminescent Eu-Coordination Polymer: Selective Detection of Nitrofuran Antibiotic and Treatment Activity on Pain After Radiotherapy Mice with Non-small Cell Lung Cancer

A novel europium coordination polymer (Eu-CP) was generated with the aid of Eu(NO3)3·6H2O with the presence of 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid (H3cpboda) under the solvothermal condition. The structural analysis results show that the prepared Eu-CP shows a 2D layered network based on the [Eu2(R-COO)4] units, and its network features a (3,6)-connected topology. The luminescent studies reveal that the prepared Eu-CP reveals strong red emission, excellent dispersion and high stability, which could be further applied to determine the antibiotic nitrofurazone (NFZ) having low limits of detection and strong quenching constants. Furthermore, the application values of the compound on the pain after radiotherapy in lung cancer mice with the non-small cell were assessed, and simultaneously, the detailed mechanism was investigated. The pain threshold of the radiotherapy mice was measured with analgesia experiment (hot plate method). Moreover, the real time RT-PCR was performed and the cholinergic receptor expression levels on presynaptic membrane were determined.

Europium coordination polymer particles based electrospun nanofibrous film for point-of-care testing of copper (II) ions

Excess free copper in serum has been identified to induce neurodegenerative diseases such as Alzheimer's disease, thus it is very important to determine copper (II) ions (Cu2+) content for human health test. Herein we developed a point-of-care testing (POCT) platform through a luminescence “on-off” recognition mechanism of serum copper. Microsized europium coordination polymer particles (Eu-CPs), which was prepared with citric acid (CA) and europium nitrate hexahydrate through a hydrothermal route, were then successfully loaded with the mixture of 2,6-pyridinedicarboxylic acid (DPA) and poly(vinyl alcohol) (PVA) to form electrospun nanofibrous films (ENFFs). The as-prepared Eu-CPs/DPA/PVA ENFFs exhibited red emission at 618 nm when exciting at 280 nm, with the quantum yields of 22.2% owing to the antenna effect from DPA to Eu3+. Furthermore, the strong luminescence could be selectively quenched by Cu2+ through coordination with DPA to interrupt the antenna effect. With that, Cu2+ was successfully detected in the range of 2–45 μM with a detection of limit of 1.3 μM, well matching with the requirement of clinic test of excess free copper induced neurodegenerative diseases. As a proof of concept at last, this POCT platform was used to detect free copper in spiked serum samples with a recovery of 101.1%–105.2%, demonstrating that this platform provides significant potential for use in clinical test.

Exploiting a new europium(III) coordination polymer based on a zwitterionic ligand as a fluorescent probe for uranyl cations

Two new isostructural lanthanide(III) coordination polymers based on an unreported zwitterionic ligand, namely, [Ln(ox)(L)]n (ox = oxalate, HL = N,N'-dipropionic acid imidazolium, Ln = Eu or La), are synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, infrared spectroscopy, powder X-ray diffraction, and thermogravimetric analysis. The fluorescence properties of the europium coordination polymer are investigated. In addition, the europium-based coordination polymer is utilized for specific sensing of UO22+ ions, showing high selectivity, a fast response time (8 min) and high sensitivity with noticeable quenching ( Ksv = 6.19 × 104 M−1) and limit of detection of 1.95 µM.

Anion-directed assemblies of europium(III) coordination polymers based on 1H-benzimidazole-5,6-dicarboxylate: structures and luminescence properties.

Two europium(III) coordination polymers (CPs), namely, poly[[diaquabis(μ4-1H-benzimidazole-5,6-dicarboxylato-κ6N3:O5,O5':O5,O6:O6')(μ2-oxalato-κ4O1,O2:O1',O2')dieuropium(III)] dihydrate], {[Eu2(C9H4N2O4)2(C2O4)(H2O)2]·2H2O}n (1), and poly[(μ3-1H-benzimidazol-3-ium-5,6-dicarboxylato-κ5O5:O5',O6:O6,O6')(μ3-sulfato-κ3O:O':O'')europium(III)], [Eu(C9H5N2O4)(SO4)]n (2), have been synthesized via the hydrothermal method and structurally characterized. CP 1 shows a three-dimensional network, in which the oxalate ligand acts as a pillar, while CP 2 has a two-dimensional network based on a europium(III)-sulfate skeleton, further extended into a three-dimensional framework by hydrogen-bonding interactions. The structural diversity in the two compounds can be attributed to the different acidification abilities and geometries of the anionic ligands. The luminescence properties of 1 display the characteristic europium red emission with CIE chromaticity coordinates (2/3, 0.34). Interestingly, CP 2 shows the characteristic red emission with CIE chromaticity coordinates (0.60, 0.34) when excited at 280 nm and a near-white emission with CIE chromaticity coordinates (0.38, 0.29) when excited at 340 nm.

Portable ratiometric probe based on the use of europium(III) coordination polymers doped with carbon dots for visual fluorometric determination of oxytetracycline.

A novel ratiometric fluorescent probe for the determination of oxytetracycline (OTC) was developed. The method is based on the use ofadenosine monophosphate/Eu(III) nanoscale coordination polymersdoped withcarbon dots (CDs) (CD@AMP/Eu NCPs). These were fabricated by self-assembly of Eu3+ and AMP on the surface of CDs containing large amounts of hydroxyl and carbonyl groups. Under the excitation at 310nm wavelength, the dopedNCPs display strong pinkemission of Eu3+ at 615nm and blue emission of theCDs at 430nm on exposure to OTC. The ratio offluorescence intensity (F615/F430) of such NCPs displays excellent linear relationship with OTC concentration ranging from 0.2 to 60μM and the limit of detection (LOD) is 25nM (3σ). The doped NCPs were evenly immobilized on common filter paper to prepare avisual ratiometric probe for the determination of OTC. Assisted by a digital camera with an APP color detector, the paper-based test strip was applied for the quantitative determination of OTC with a LOD of 0.5μM and a wide linear scope of 1-100μM. The method was applied to the determination of OTC in milk samples. Graphical abstractSchematic representation of the principle for oxytetracycline (OTC) determination using carbon dots (CD)@adenosine monophosphate (AMP)/Europium (Eu3+) paper-based ratiometic probe.

H2O2-responsive smart dressing for visible H2O2 monitoring and accelerating wound healing

Inflammation or infectious wound could produce high level of hydrogen peroxide (H2O2), which may prevent wound healing process. It could be directly monitored the generated H2O2 to determine the wound microenvironment, which related to its healing status. Europium(III) Coordination Polymers (Eu CPs) had the ability to detect the level of H2O2 and promote wound healing. Thus, a H2O2-responsive smart dressing, fabricated by loading Eu CPs into polyacrylonitrile (PAN) nanofiber mats, has been presented in this study. This theranostic wound dressing can monitor H2O2 level of the wound microenvironment through a simple visible color change. In addition, in vitro cytocompatibility experiments showed that human umbilical vein endothelial cells (HUVEC) and fibroblast cells (L929) could adhesion and proliferation well onto PAN-Eu CPs nanofiber mats, and the RT-qPCR and western blots results indicated that the mats could promote the expression of angiogenic-related genes and factors by HUVEC. Moreover, in vivo animal tests indicated that PAN-Eu CPs nanofiber mats could effectively accelerated wound healing by promoting neovascularization performed by immunohistochemical analysis. Overall, the smart dressing will understand the information of wound microenvironment and reduce the frequency of dressing change, in turn, saving the healthcare cost as well as reducing patient's stress and pain.

A highly sensitive visual sensor for tetracycline in food samples by a double-signal response fluorescent nanohybrid

In this study, a ratiometric fluorescent probe BCDs-Eu/CMP-cit was developed for the detection of tetracycline (TC) in food samples by simply mixing blue fluorescent carbon quantum dots (BCDs) and cytidine monophosphate (CMP)/europium coordination polymer nanoparticles (Eu/CMP-cit CPNs) together. In this ratiometric sensor, the emission of BCDs at 465 nm gradually decreased and that of Eu/CMP-cit CPNs at 620 nm significantly increased with the sequential addition of TC upon being excited at 380 nm, accompanyed by a remarkable fluorescence color change from bright blue to red. It was worth mentioning that both of the two components in BCDs-Eu/CMP-cit nanosystem were employed as response signals with different fluorescent signal output. Hence, the sensitivity to TC is greatly enhanced without being affected by other potentially interfering substances. Under the optimized conditions, a good linear relationship between the concentration of TC from 0.05 to 30 μM and the fluorescence intensity ratio of F620/F465 was obtained. The detection limit was calculated to be 8 nM, which was much lower than that of most of the previously published methods. Moreover, this proposed nanosystem was also successfully applied to the assay of TC in food samples, including fish, lamb, beef, chicken, pork, egg, milk and honey, and the recovery rates were even comparable to those obtained from high performance liquid chromatography (HPLC)-based methods. Importantly, a paper-based visual sensor for TC in various food samples was devised by using filter paper embedded with BCDs-Eu/CMP-cit. The distinct fluorescent color changing from bright blue to red of the filter paper with different concentrations of TC demonstrated a great potential of as-prepared ratiometric fluorescent probe for the visual detection of TC in complicated real samples.

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.

2D europium coordination polymer as a regenerable fluorescence probe for efficiently detecting fipronil.

Recently, considerable attention has been paid to European eggs that were found to contain the poisonous insecticide fipronil. Excessive consumption of fipronil can harm the human body, in particular, the liver, thyroid, nervous system and kidneys. As a consequence, there is an urgent need to develop a method to detect fipronil. In this work, a lanthanide coordination polymer [Eu(SIP)(H2O)4]n (1) (NaH2SIP = 5-sulfoisophthalic acid monosodium salt) was synthesized and characterized by single-crystal X-ray crystallography, elemental analysis, infrared spectrum and powder X-ray diffractions. The X-ray studies show that 1 is a two-dimensional layered structure, which is constructed of fused {[Eu(H2O)4]3(SIP)3} pseudo-hexagonal grids. The luminescence properties of 1 exhibit effective recognition for fipronil in methanol solution. Furthermore, a wide linear range (10-6-10-4 M), a low detection limit of 0.8 μM, high selectivity and excellent recyclability, reveal that 1 can potentially act as a luminescence-based sensor for quantitative and highly sensitive detection of fipronil. To the best of our knowledge, it is the first time that a metal-organic coordination polymer, as a fluorescent-based probe, has been used for the detection of fipronil. Moreover, fluorescent-based test papers of 1 have also been prepared, which can be regarded as a simple and practical method for detecting fipronil.

Ratiometric detection of hydroxy radicals based on functionalized europium(III) coordination polymers.

A ratiometric fluorescent probe is described that is based on a functionalized europium(III) coordination polymer (Eu/DPA-TA). It can be fabricated by using dipicolinic acid (DPA) asa bridging ligand (to sensitize the Eu3+ fluorescence) and terephthalic acid (TA) acting as a functional ligand to recognize the hydroxy radical (•OH). The quenching of Eu3+ fluorescence (measured at excitation/emission wavelengths of 288/615nm) by water is strongly reduced in the presence of TA. This leads to a significant enhancement in the emission lifetime and intensity of Eu3+. Upon the addition of •OH, the fluorescence of Eu/DPA-TA showed ratiometric changes in that the TA sensitized fluorescence (peaking at 445nm) is switched on, while the plain Eu3+ fluorescence (peaking at 615nm) decreases. This finding led to a method for the ratiometric (2-wavelength) detection of OH˙ with a 0.5μM detection limit. The method also allows OH˙ to be detected with bare eyes at OH˙ concentrations as low as 10μM. In our perception, this study paves the way towards the design of new functionalized lanthanide coordination polymers for fluorometric assays and biomedical imaging. Graphical abstract Schematic of a ratiometric fluorescent assay for the detection of hydroxy radical (•OH) based onthe use of a europium(III)/dipicolinic acid coordination polymer (Eu/DPA CP) functionalized with terephthalic acid (TA). A gradual color change from red to blue can be observed and correlated to •OH concentrations.

Au nanoparticle@silica@europium coordination polymer nanocomposites for enhanced fluorescence and more sensitive monitoring reactive oxygen species

Au nanoparticle (Au NP)@SiO2@TDA-Eu nanocomposites were prepared by a two-step process: Au NP@SiO2 nanocomposites were prepared by a modified onepot process. Then the europium coordination polymer was deposited on the surface of the Au NP@SiO2 by mixing 2,2’-thiodiacetic acid [S(CH2COO)22-, TDA] and Eu(NO3)3·6H2O in ethanol via a hydrothermal method. The maximum fluorescent enhancement factor of the nanocomposites was 6.81 at 30 nm thickness of silica between the core of the Au NP and the shell of TDA-Eu. The prepared nanocomposites exhibit more sensitive monitoring of reactive oxygen species.

A water stable europium coordination polymer as fluorescent sensor for detecting Fe3+, CrO42-, and Cr2O72- ions

A europium coordination polymer constructed by the 4′-(4-carboxyphenyl)− 2,2′:6′,2″-terpyridine ligand (HL), namely, [EuL(CH3COO)Cl]n (1), has been prepared by the solvothermal method. Compound 1 was structurally characterized by the elemental analysis, FT-IR, powder X-ray diffractions (PXRD), thermogravimetric (TG) analysis, and single-crystal X-ray diffraction. Complex 1 displays a novel linear chain structure, which further extends to the 3D supramolecular structure via π···π and hydrogen bonds interactions. The luminescent properties of 1 were investigated in detail, which exhibit the fluorescent sensing for detecting Fe3+, CrO42-, and Cr2O72- ions in aqueous solution, respectively. In addition, 1 shows high sensitive and selective sensing for CrO42- and Cr2O72- anions with the great quenching efficiency. Furthermore, the luminescent sensing mechanisms of differentiating analytes are explored in detail. It is worth noting that there exists the weak interaction between Fe3+ ions and carboxylate oxygen atoms of CH3COO– groups through XPS characterization, resulting in the high quenching effect of 1.