Novel Lanthanide (III) Complexes Derived from an Imidazole–Biphenyl–Carboxylate Ligand: Synthesis, Structure and Luminescence Properties

A series of neutral mononuclear lanthanide complexes [Ln(HL)2(NO3)3] (Ln = La, Ce, Nd, Eu, Gd, Dy, Ho) with rigid bidentate ligand, HL (4′-(1H-imidazol-1-yl)biphenyl-4-carboxylic acid) were synthesized under solvothermal conditions. The coordination compounds have been characterized by infrared spectroscopy, thermogravimetry, powder X-ray diffraction and elemental analysis. According to X-ray diffraction, all the complexes are a series of isostructural compounds crystallized in the P2/n monoclinic space group. Additionally, solid-state luminescence measurements of all complexes show that [Eu(HL)2(NO3)3] complex displays the characteristic emission peaks of Eu(III) ion at 593, 597, 615, and 651 nm.

Preparation of Eu0.075Tb0.925-Metal Organic Framework as a Fluorescent Probe and Application in the Detection of Fe3+ and Cr2O72−

Luminescent Ln-MOFs (Eu0.075Tb0.925-MOF) were successfully synthesised through the solvothermal reaction of Tb(NO3)3·6H2O, Eu(NO3)3·6H2O, and the ligand pyromellitic acid. The product was characterised by X-ray diffraction (XRD), TG analysis, EM, X-ray photoelectron spectroscopy (XPS), and luminescence properties, and results show that the synthesised material Eu0.075Tb0.925-MOF has a selective ratio-based fluorescence response to Fe3+ or Cr2O72−. On the basis of the internal filtering effect, the fluorescence detection experiment shows that as the concentration of Fe3+ or Cr2O72− increases, the intensity of the characteristic emission peak at 544 nm of Tb3+ decreases, and the intensity of the characteristic emission peak at 653 nm of Eu3+ increases in Eu0.075Tb0.925-MOF. The fluorescence intensity ratio (I653/I544) has a good linear relationship with the target concentration. The detection linear range for Fe3+ or Cr2O72− is 10–100 μM/L, and the detection limits are 2.71 × 10−7 and 8.72 × 10−7 M, respectively. Compared with the sensor material with a single fluorescence emission, the synthesised material has a higher anti-interference ability. The synthesised Eu0.075Tb0.925-MOF can be used as a highly selective and recyclable sensing material for Fe3+ or Cr2O72−. This material should be an excellent candidate for multifunctional sensors.

New physical and chemical properties of chitosan-samarium composite: synthesis and characterization

Chitosan (CHN) is a natural polymer derived from chitin by deacetylation method and has hydrophilic properties. It has been developed by combining it with other compounds to change their surface structures with suitable chemical surfaces and to increase their abilities and activities. Modification of CHN with lanthanide ions can increase its function as adsorbent for heavy metals, removal anions dye, drug conductor, and/or for oil-water separation. In this paper, chitosan-samarium (CHN-Sm) composites were prepared using impregnation method. The concentration of CHN and Sm were also varied and investigated in details. This modification is aimed to produce CHN-Sm composites with new physical and chemical properties. Various ratio CHN and Sm contents from 2:0.3; 2:0.5; 2:1 and 2:2 (w/w) were observed to enhance the hydrophobic characteristic of CHN. Characterization of the CHN-Sm composites were conducted using FTIR, SEM–EDX and fluorescence spectrophotometer. The emission of the CHN-Sm composites showed the characteristic emission of Sm3+ ions (4G5/2-6H7/2, and 4G5/2-6H11/2), but also a stronger wide emission band (360–500 nm) of the CHN. Furthermore, the CHN-Sm composites can be used as the active site in adsorbent for separation of water-oil.

Synthesis & PL study of GdPO4:Tb,Eu nanophosphor

Tb3+ and Eu3+ ions co-doped containing monoclinic GdPO4 nanocrystals were successfully obtained by a straightforward combustion method. The crystal structure and optical characteristics were investigated by methods: XRD, photoluminescence spectra (PL). The XRD result indicates the GdPO4:10%Tb, x%Eu had monoclinic phase and the average particle size was about 10 nm. Under excitation wavelength at 394 nm, photoluminescent emission spectra of GdPO4:10%Tb, x%Eu nanopowders show strong characteristic emission of Eu3+ ions and no characteristic emission of Tb3+ ions was found. However, under the excitation of 273 nm or 368 nm, the emission spectra of the samples were shown characteristic emission of Tb3+ ions with 5D4 - 7FJ (J=3-6) transitions and Eu3+ ions with 5D0-7FJ (J=0-4) transitions.

Fluorescent Composite Hydrogel of Carboxymethyl Celluose-Eu(Ⅲ)/Polyvinyl Alcohol and Its Application in Functional Paper

A novel carboxymethyl cellulose-Europium(Ⅲ)/polyvinyl alcohol (CMC-Eu(Ⅲ)/PVA) fluorescent hydrogel was prepared by a green and facile method. The hydrogel formed a physical cross-linking network under mild reaction conditions without using volatile organic chemical reagents. A porous structure was formed by the hydrogen bonding and other interaction between the PVA chains and the free hydroxyl on CMC-Eu(Ⅲ) during the composite gel transformation process. The addition of CMC-Eu(Ⅲ) improved the tensile and compressive mechanical properties of PVA hydrogel. When the CMC-Eu(Ⅲ) content was 15%, the maximum tensile stress of the composite hydrogel was 47.25±10.35 kPa and the compressive stress was 10.14±1.90 kPa. Meanwhile, the CMC-Eu(Ⅲ)/PVA hydrogels exhibited a 5D0→7F2 characteristic emission peak of Eu3+ at 615 nm, and emitted stable red fluorescence under UV irradiation at 254 nm. Moreover, the hydrogel was applied in making fluorescent paper as an internal sizing agent. When the amount of hydrogel was 1%, the tensile strength of fluorescent paper reached 3.52 kN/m, which is promising in the application of anti-counterfeiting.

Investigation of Structural and Luminescent Properties of Sol-Gel-Derived Cr‑Substituted Mg3Al1−xCrx Layered Double Hydroxides

In the present work, Cr-substituted Mg3Al1−xCrx layered double hydroxides (LDHs) were synthesised through the phase conversion of sol-gel-derived mixed-metal oxides in an aqueous medium. The chromium substitution level in the range of 1 to 25 mol% was investigated. It was demonstrated that all synthesised specimens were single-phase LDHs. The results of elemental analysis confirmed that the suggested synthetic sol-gel chemistry approach is suitable for the preparation of LDHs with a highly controllable chemical composition. The surface microstructure of sol-gel-derived Mg3Al1−xCrx LDHs does not depend on the chromium substitution level. The formation of plate-like agglomerated particles, which consist of hexagonally shaped nanocrystallites varying in size from approximately 200 to 300 nm, was observed. Optical properties of the synthesised Mg3Al1−xCrx LDHs were investigated by means of photoluminescence. All Cr-containing powders exhibited characteristic emission in the red region of the visible spectrum. The strongest emission was observed for the sample doped with 5 mol% Cr3+ ions. However, the emission intensity of samples doped with 1–10 mol% Cr3+ ions was relatively similar. A further increase in the Cr3+ ion concentration to 25 mol% resulted in severe concentration quenching.

Electrospinning Synthesis of Fe3O4/Eu(DBM)3phen/PVP Multifunctional Microfibers and Their Structure, Luminescent and Magnetic properties

Multifunctional Fe3O4/Eu(DBM)3phen/PVP ((DBM: dibenzoylmethane, phen: 1,10-phenanthroline, PVP: polyvinyl pyrrolidone) microfibers were constructed by simple electrospinning process. The structure and morphology of the microfibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. The diameters of pure PVP microfibers and the microfibers doped only with Fe3O4 nanoparticles (NPs) were uniformly distributed, with an average size of about 360 nm. When 3% Eu(DBM)3phen complex and Fe3O4 NPs were both added to the precursor for electrospinning, the microfibers became very inhomogeneous in diameter. The photoluminescent properties of pure Eu(DBM)3phen complex and composite microfibers were also studied. The characteristic emission peaks of Eu3+ appeared in the composite microfibers. The intensities of emission and excitation spectra gradually decrease with adding more Fe3O4 NPs. The unit mass of the pure europium complex in some composite microfibers gave stronger luminescence than the pure europium complex. The fluorescence lifetime of 5D0 state in the composite microfibers is longer than that of pure europium complex. Additionally, the magnetic properties of Fe3O4 NPs and the composite microfibers were investigated. Fe3O4 NPs and composite microfibers were both superparamagnetic. The saturation magnetization of the composite microfibers was smaller than that of pure Fe3O4 NPs.

Upconversion Luminescence of Silica–Calcia Nanoparticles Co-doped with Tm3+ and Yb3+ Ions

Looking for upconverting biocompatible nanoparticles, we have prepared by the sol–gel method, silica–calcia glass nanopowders doped with different concentration of Tm3+ and Yb3+ ions (Tm3+ from 0.15 mol% up to 0.5 mol% and Yb3+ from 1 mol% up to 4 mol%) and characterized their structure, morphology, and optical properties. X-ray diffraction patterns indicated an amorphous phase of the silica-based glass with partial crystallization of samples with a higher content of lanthanides ions. Transmission electron microscopy images showed that the average size of particles decreased with increasing lanthanides content. The upconversion (UC) emission spectra and fluorescence lifetimes were registered under near infrared excitation (980 nm) at room temperature to study the energy transfer between Yb3+ and Tm3+ at various active ions concentrations. Characteristic emission bands of Tm3+ ions in the range of 350 nm to 850 nm were observed. To understand the mechanism of Yb3+–Tm3+ UC energy transfer in the SiO2–CaO powders, the kinetics of luminescence decays were studied.