Luminescent Sm Research Articles

Synthesis and photo-physics of luminescent Sm(III) complexes derived from β-hydroxyketone and heterocyclic ancillary ligands

A series of six Sm (III) complexes containing organic ligands were synthesized using liquid assisted environment-friendly grinding method. The complexes were characterized through various techniques like UV, IR, NMR, XRD, SEM, EDAX, PL and TGA/DTG. The luminescent properties studies in solid and solution form suggests that 4G5/2 → 6H7/2 (604 nm) and 4G5/2 → 6H9/2 (645 nm) transitions were accountable for the orange and reddish orange emission respectively on UV excitation. An orange colour light emission is also consistent with the outcomes of chromaticity, i.e., colour coordinates, CCT, and CP. To know further about the coordination environment Judd-Ofelt intensity parameters (Ω2, Ω4, Ω6) were calculated. In complexes greater value of Ω2 in comparison to Ω4 and Ω6 is the result of greater covalence. The band gap and Urbach energy obtained lie in the range of semiconductor devices. The HOMO-LUMO gap obtained theoretically and experimentally are in agreement with each other. These complexes have potential application in laser devices. The evaluation of antioxidant and antimicrobial properties of complexes indicates their application in pharmaceutical industry.

Study of Judd-Ofelt, Urbach energy and photosensitization process in luminescent Sm(III) complexes with heterocyclic ligands.

Six samarium (III) complexes were synthesised by employing the β-ketocarboxylic acid as main ligand and five N-donor systems as ancillary ligands through the environmentally safe liquid-assisted grinding method. Various characterisation techniques were employed to determine the structure of the complexes i.e. NMR, IR, XRD and SEM. Photoluminescent studies were carried out in solid as well as in solution form. In solid and solution form emission spectra show maximum intensity peak at 604 and 602nm, respectively, assigned to 4G5/2 → 6H7/2 transition which explains orange emission on UV excitation in complexes. CCT, CP, colorimetric parameters and quantum yield (relative and intrinsic) of the synthesized complexes were calculated. With the help of reflectance spectra, band gap and Urbach energy were determined. Lasing parameters were also calculated by employing FWHM values obtained from Gaussian fitting. Energy transfer study revealed the efficacious energy transfer from ligand to metal's emissive level. Further antimicrobial studies revealed higher activity in case of complexes in comparison to ligand.

Luminescence features of mononuclear Sm(III) complexes with heterocyclic ligands

Three ternary luminescent Sm(III) complexes were synthesized using 4-oxo-4H-1-benzopyran-3-carboxaldehyde (L), 4-Methyl-1,10-Phenanthroline (mphen), 2,2′-Biquinoline (biq), and Bathocuproine (bathocup) organic ligands. The synthesized materials were thoroughly characterized by ESI-MS+, CHN elemental analysis, Thermogravimetric analysis, UV–vis spectroscopy, FTIR, PXRD, FESEM, and PL spectroscopy techniques. The existence of sharp-narrow peaks in X-ray diffractogram confirmed crystallinity in the complexes. The ESI-MS+ and CHN data were in accordance with the proposed molecular formula of prepared materials. The optical bandgap (Eg) assessed from the Tauc plots suggested the direct electronic transition and semi-conducting character of the complexes with bandgap falling in the range 2.86–2.93 eV. The room temperature luminescence studies, carried out in the solution and powder state displayed three noticeable peaks from excited (4G5/2) to ground state (6H5/2, 7/2, 9/2) at ∼566, 601, and 647 nm, under UV excitation. The orange-red emission by the complexes was also confirmed through CIE chromaticity. The complexes possess good thermal stability. The prepared complexes might be potential candidate for liquid lasers, bio-assays, and solid-state lighting applications.

Combination of imine bond and samarium emitter enables turn-off fluorescence detection of hydrazine in vapor and water samples

The development of convenient and efficient fluorescence techniques is of great significance for selective detection and precise determination of biotoxic N2H4 in human health and environmental sciences. By the pre-organization-assisted template synthesis, disclosed here is a luminescent Sm(III) macrocycle-based probe Sm-2m bearing dynamic imine bonds as recognition moieties which provides the selective and ratiometric turn-off fluorescence sensing for N2H4 over various amine species based on the N2H4-induced structure transformation. This fluorescent sensing process finished within 20 min shows the low limit of detection (0.18 μM, 7.2 ppb) and wide linear sensing range (0–60.0 μM). Furthermore, probe Sm-2m is also be used to quantitatively determine N2H4 in vapor gas and water samples through fluorescence color changes, which are evaluated by the Sm-2m-impregnated test paper strips and RGB value outputs. Finally, our proposed smartphone-based analytical method gives satisfactory N2H4 detection results. It is thus believed that this work can shed some lights on development of optical probes and detection techniques for N2H4, even other hazardous chemicals.

Luminescent Sm(III) complex bearing dynamic imine bonds as a multi-responsive fluorescent sensor for F− and PO43− anions together with Zn2+ cation in water samples

We have designed and synthesized a new luminescent mononuclear samarium (III) complex Sm-2h based on the [1 + 1] Schiff-base macrocycle H2L2h, derived from the cyclocondensation reaction between dialdehyde and diamine precursors, and its exact architecture is determined to be [Sm(HL2h) (NO3)2]. The sensing ability of complex Sm-2h is carefully evaluated for various common inorganic ions in solution. It is shown that complex Sm-2h is a multi-responsive fluorimetric sensor with high selectivity for F− and PO43− anions together with Zn2+ cation. The sensing process is rapid within 60 s for F− and PO43− ions and 300 s for Zn2+ ion. Further detailed responsive investigations suggest that its sensing behavior has excellent linear relationship between the fluorescence intensity (or absorption value) and ion concentration. The limit of detection (LOD) for sensing F−, PO43− and Zn2+ ions are as low as 2.61 μM (2.94 μM), 1.92 μM (1.64 μM) and 5.67 μM (3.53 μM), respectively, verified by fluorimetric (or colorimetric) titration experiments. ESI mass spectra prove that these efficient detections originate from the structure collapse of sensor Sm-2h because of the ion-induced imine bond breakage. Moreover, sensor Sm-2h shows excellent sensing performances for F−, PO43− and Zn2+ ions in real water samples, and we also have developed a convenient method to detect these three ions by use of the sensor impregnated test paper strips, providing rapid and distinguishable fluorimetric color changes. Therefore, the macrocyclic Sm(III) complex Sm-2h could be regarded as a valuable candidate for monitoring F−, PO43− and Zn2+ ions in practical applications.

Luminescent macrocyclic Sm(III) complex probe for turn-off fluorescent and colorimetric water detection in organic solvents and liquid fuels

The rapid and sensitive detection of water has attracted wide interests in the chemical and energy industry for its harmful influences, which encourage researchers to explore kinds of materials for sensing water. Herein, we report the sensing performance of a Schiff-base macrocyclic Sm(III) complex Sm-2g as the turn-off fluorescent and colorimetric probe for water detection in organic solvents (DMF, methanol and acetone) and liquid fuels (bioethanol and avgas). It is especially encouraging that the probe Sm-2g exhibits a rapid and sensitive response for water, and it could be easily distinguished by the distinct fluorescence quenching and absorption shift. Electrospray ionization mass spectra prove that this efficient detection is achieved based on the transformation from complex Sm-2g to corresponding dialdehyde precursor, originating from the imine bond cleavage after the addition of water. Furthermore, the Sm-2g impregnated paper strip also provides a convenient way to detect water by its rapid and distinguishable fluorescent color changes in organic media. Therefore, the luminescent Sm(III) complex Sm-2g shows promise as a valuable candidate for the detection of water.

Series of Highly Luminescent Macrocyclic Sm(III) Complexes: Functional Group Modifications Together with Luminescence Performances in Solid-State, Solution, and Doped Poly(methylmethacrylate) Film.

Here, we report our trials to regulate the luminescence performance of the macrocyclic samarium(III) complex and prepare four excellent luminescent Sm(III) complex-doped poly(methylmethacrylate) (PMMA) composites. Four 23-membered [1 + 1] Schiff-base macrocyclic mononuclear Sm(III) complexes, Sm-2a–Sm-2d, originating from dialdehydes with different pendant arms and 1,2-bis(2-aminoethoxy)ethane, have been constructed by the template method. Crystal structures reveal that every Sm(III) ion with the coordination geometry of a distorted bicapped square antiprism is capsulated by the macrocyclic cavity environment forming the “lasso-type” protection. Relative photophysical properties of macrocyclic Sm(III) complexes are carefully investigated in solid-state, methanol solution, and doped PMMA film, and all these show characteristic emissions of the Sm(III) ion associated with satisfactory lifetimes and quantum yields in all media, which could be comparable to reported outstanding examples. Especially, the luminescence performance for this type of Sm(III) complex could be regulated in the solid state by the use of different functional groups in the pendant arm while it is not achieved in solution and the doped PMMA composite. High emitting and air-stable plastic materials could be obtained when these Sm(III) complexes are doped in PMMA with 0.1 wt % mixing ratio, and the corresponding maximum lifetime and quantum yield are 61.2 μs and 0.63% in the case of complex Sm-2a, respectively. We believe that these highly luminescent “lasso-type” Sm(III) complexes and doped PMMA composites are valuable references in the design of luminescent lanthanide(III) hybrid materials.

Self-assembly of one visible and NIR luminescent Sm(III) coordination polymer with flexible Schiff base ligand

Two mononuclear lanthanide complexes [EuL1(NO3)(H2O)DMF] (1) and [SmL1(OAc)(H2O)EtOH] (2), and one lanthanide coordination polymer {Sm(L2)(OAc)}n (3) were synthesized by the use of two Schiff base ligands with a long (CH2)2NH(CH2)2 backbone. The crystal structures of 1–3 were determined by X-ray crystallography. The chromogenic Schiff base ligands in 1–3 can transfer energy to lanthanide ions and these complexes exhibit the typical luminescence of lanthanide ions. In 1 and 2, there is a H2O molecule coordinated with the Ln3+ ion, while there are no solvent molecules coordinated with the lanthanide ion in 3. Interestingly, for the Sm(III) complexes, the lanthanide coordination polymer 3 has longer emission lifetime and higher quantum yield (Φem) than the mononuclear lanthanide complex 2.

An Efficient Visible and Near-Infrared (NIR) Emitting Sm(III) Metal-Organic Framework (Sm-MOF) Sensitized by Excited-State Intramolecular Proton Transfer (ESIPT) Ligand.

We report herein an unprecedented example of a luminescent Sm(III) metal-organic framework (Sm-MOF), in which both the visible and near-infrared (NIR) emissions of Sm(3+) ions are able to be sensitized by an excited-state intramolecular proton transfer (ESIPT) ligand. Due to the solvent-mediated interchange between enol and keto excited states of the ligand and subsequent energy transfer rate to Sm(3+) ions, the luminescent decay lifetime of the Sm-MOF can be tuned in different solvent-grinding systems.

Highly luminescent Sm(III) complexes with intraligand charge-transfer sensitization and the effect of solvent polarity on their luminescent properties.

Samarium complexes with the highest quantum yields to date have been synthesized, and their luminescence properties were studied in 12 solvents. Sensitization via a nontriplet intraligand charge-transfer pathway was also successfully demonstrated in solution states with good quantum yields.

Atomic-scale distortion of optically activated Sm dopants identified with site-selective X-ray absorption spectroscopy

The local structure of luminescent Sm dopants was investigated using an X-ray absorption fine-structure technique with X-ray-excited optical luminescence. Because this technique evaluates X-ray absorption from luminescence, only optically active sites are analyzed. The Sm L3 near-edge spectrum contains split 5d states and a shake-up transition that are specific to luminescent Sm. Theoretical calculations using cluster models identified an atomic-scale distortion that can reproduce the split 5d states. The model with C4v local symmetry and compressive bond length of Sm–O of a six-fold oxygen (SmO6) cluster is most consistent with the experimental results.

Czochralski Growth and Optical Properties οf (Lu_{x}Gd_{1-x})_2SiO_5 Solid Solution Crystals Single Doped with Sm^{3+} and~Dy^{3+}

Solid solution crystals (LuxGd1−x)2SiO5 single doped with Sm 3+ and Dy were grown by the Czochralski method. Segregation coe cients Lu/Gd, melting temperatures and structures of solid solution crystals were determined for 0.15 ≤ x ≤ 0.8. It was found that for x ≥ 0.17 the crystals belong to the monoclinic system within a space group C2/c and their melting temperature diminishes monotonously from 1990 ◦C to 1780 ◦C when x decreases from 0.8 to 0.15. Disparity of ionic radii of Lu and Gd induces structural disorder that brings about an inhomogeneous broadening of spectral lines in absorption and emission spectra of incorporated luminescent Sm and Dy ions. Optical properties of obtained crystals were determined based on results of measurement of absorption and emission spectra and luminescence decay curves. Spectroscopic investigation revealed that Sm doped crystals show intense emission distributed in the visible-near infrared region with the most intense band centred at 605 nm and characterized by a branching ratio of 0.43. Emission spectrum of Dy doped crystals is dominated by a band centred at 575 nm and characterized by a branching ratio of 0.58. It has been concluded that the systems under study are potential laser materials able to generate visible emission upon GaN/InGaN laser diode pumping.

Emission analysis of Sm 3+:Ca 4GdO(BO 3) 3 powder phosphor

This paper reports on the spectral analysis of reddish orange color luminescent Sm 3+:Ca 4GdO(BO 3) 3 powder phosphor. This phosphor powder has been synthesized by a solid state reaction method. Emission spectrum of it has shown four emission transitions of 4G 5/2 → 6H J ( J = 5/2, 7/2, 9/2, 11/2) and among them, the transition 4G 5/2 → 6H 7/2 displays the reddish orange (605 nm) color. Lifetimes of three emissions ( 4G 5/2 → 6H J=5/2, 7/2 & 9/2 ) have been computed based on the measured decay curves. Besides the measurement of emission spectrum of this material, its nature and structural details have also been investigated from XRD, SEM and FTIR studies.

Development of luminescent Sm(III) chelates containing hexadentate to nonadentate ligands: synthesis, photophysical properties and coupling to biomolecules

Seventeen novel samarium (Sm)(III) chelates containing two iminodiacetic acid moieties were synthesised and their luminescence properties were measured with the aim of developing new labels for biochemical applications. The chelates contained different numbers of coordinating groups. According to the results obtained, the Sm(III) chelates that are to be used in time-resolved luminescence biochemical assays should be nonadentate in order to have a sufficient lifetime. Chelates having a terpyridine structure in the ligand seem to be promising alternatives. In addition, an equation for the determination of the number of water molecules in the first coordination sphere of Sm(III) ions in the chelate was developed.