Erbium Complexes Research Articles

Rare-Earth Quinolinates: Infrared-Emitting Molecular Materials with a Rich Structural Chemistry

Near-infrared-emitting rare-earth chelates based on 8-hydroxyquinoline have appeared frequently in recent literature, because they are promising candidates for active components in near-infrared-luminescent optical devices, such as optical amplifiers, organic light-emitting diodes, .... Unfortunately, the absence of a full structural investigation of these rare-earth quinolinates is hampering the further development of rare-earth quinolinate based materials, because the luminescence output cannot be related to the structural properties. After an elaborate structural elucidation of the rare-earth quinolinate chemistry we can conclude that basically three types of structures can be formed, depending on the reaction conditions: tris complexes, corresponding to a 1:3 metal-to-ligand ratio, tetrakis complexes, corresponding to a 1:4 metal-to-ligand ratio, and trimeric complexes, with a 3:8 metal-to-ligand ratio. The intensity of the emitted near-infrared luminescence of the erbium(III) complexes is highest for the tetrakis complexes of the dihalogenated 8-hydroxyquinolinates.

Self-assembled infrared-luminescent Er–Si–O crystallites on silicon

Optically active and electrically excitable erbium complexes on silicon are made by wet-chemical synthesis. The single-crystalline Er–Si–O compound is formed by coating a Si(100) substrate with an ErCl3∕ethanol solution, followed by rapid thermal oxidation and annealing. Room-temperature Er-related 1.53μm photoluminescence is observed with a peak linewidth as small as 4meV. The complexes can be excited directly into the Er intra-4f states, or indirectly, through photocarriers. Er concentrations as high as 14at.% are achieved, incorporated in a crystalline lattice with a 0.9nm periodicity. Thermal quenching at room temperature is only a factor 5, and the lifetime at 1.535μm is 200μs.

Crystallographic report: Crystal structure of tris(2,6‐di‐tert‐butyl‐4‐methylphenolato‐O) (tetrahydrofuran‐O) erbium toluene solvate

AbstractA low‐coordinate aryloxo erbium complex, [(ArO)3Er(THF)](MePh), has been synthesized by the reaction of anhydrous ErCl3 with three equivalents of NaOAr in tetrahydrofuran. The central erbium atom is coordinated by three oxygen atoms of the aryloxo ligands and one oxygen atom of the tetrahydrofuran molecule, resulting in a distorted tetrahedron. Copyright © 2004 John Wiley & Sons, Ltd.

The Er and Yb Complexes with Silicon-Containing Phosphates and Fluorine-Containing Phosphine Oxide: Synthesis, Spectra, and Films

Three new silicon- and fluorine-containing ligands, namely bis(dimethylamido)(3-triethoxysilylpropylamido)phosphate O=P(NMe2)2NHCH2CH2CH2Si(OEt)3, diphenyl(3-triethoxysilylpropylamido)phosphate O=P(OPh)2NHCH2CH2CH2Si(OEt)3, and tris(3,3,3-trifluoropropyl)phosphine oxide O=P(CH2CH2CF3)3 are synthesized. The erbium and ytterbium complexes with amine, phosphate, and phosphine oxide ligands Ln(NH2R)3Cl3, Ln[O=P(NMe2)2NHR]3Cl3, Ln[O=P(OPh)2NHR]3Cl3 (R=CH2CH2CH2Si(OEt)3), Ln[O=P(OPh)3]3Cl3, Ln[O=P(CH2CH2CF3)3]3Cl3 are produced and their electronic absorption spectra and photoluminescence spectra are studied. The silicon-containing compounds form transparent thermostable films on silicate glass or quartz surface.

Time‐resolved luminescence of terbium complexes with poly(2‐ and 4‐vinylpyridine N‐oxide)s in aqueous solution

AbstractTerbium complexes with polymer ligands of poly(2‐ and 4‐vinylpyridine N‐oxide)s (P2VPNO, P4VPNO) in aqueous solution were prepared and characterized. Multi‐exponential decays of the 5D4 → 7F5 terbium transition at 545 nm of [P2VPNO‐Tb3+] and [P4VPNO‐Tb3+] complexes were measured. The non‐linearity of semi‐logarithmic plots of time‐resolved luminescence was more pronounced in [P4VPNO‐Tb3+] than in [P2VPNO‐Tb3+], being reduced by addition of salts such as sodium formate or acetate. We assume that multi‐exponential decays of Tb3+ in the complexes are caused by a back metal‐to‐ligand energy transfer via triplet state of N‐oxide polymer ligand. By carrying out separate experiments in water and deuterium oxide, the number of coordinated water molecules in the [P4VPNO‐Tb3+] complex was estimated as 4‐5, assuming that the Tb3+ aqua complex contains nine water molecules.

Near-Infrared Luminescence of Lanthanide Calcein and Lanthanide Dipicolinate Complexes Doped into a Silica−PEG Hybrid Material

The near-infrared luminescence of lanthanide complexes of 4',5'-bis[N,N-bis(carboxymethyl)aminomethyl] fluorescein (calcein) and pyridine-2,6-dicarboxylic acid (dipicolinic acid, dpa) doped in a hybrid sol-gel material was investigated. The silica-poly(ethylene glycol) (silica-PEG) inorganic-organic materials were prepared at a neutral pH. The lanthanide ions are well shielded from the environment by the calcein and dpa ligands, and the complexes are stable in the sol-gel matrix after preparation. The dysprosium and neodymium dipicolinate complexes showed near-infrared luminescence (NIR-luminescence) by direct excitation to the 4f-levels. The ytterbium dipicolinate complex doped in the sol-gel showed NIR-luminescence by excitation of the ligand in the UV region. All other tested lanthanide ions (Ln = Pr, Sm, Er, Ho) did not show luminescence. Neodymium and ytterbium complexes with calcein show intense NIR-luminescence when the ligand is excited by visible light. The corresponding erbium complex doped in the silica-PEG matrix also showed NIR-luminescence at 1525 nm. No NIR-luminescence could be detected for the other lanthanide complexes doped in the matrix (Ln = Pr, Sm, Dy, Ho).

Synthesis, Characterization and Near‐Infrared Photoluminescence of Monoporphyrinate Lanthanide Complexes Containing an Anionic Tripodal Ligand

AbstractTwelve neutral stable complexes of ytterbium(III) and erbium(III) coordinated by anionic hydridotris(pyrazol‐1‐yl)borate and meso‐tetraphenylporphyrinate, and its derivatives with different substituents in the para position of the phenyl groups, were prepared and characterized. Crystal structure analyses revealed that seven nitrogen atoms, four from the porphyrinate dianion and three from the anionic tripodal ligand, are symmetrically coordinated to the lanthanide ions. Photophysical investigations of the complexes showed an enhancement of near‐infrared photoluminescence as compared to aqua‐coordinated monoporphyrinate lanthanide complexes. The solvent effect and substituent effects on the photoluminescent properties of the complexes were also investigated (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).

Erbium and ytterbium complexes with phosphates and phosphine oxides

The new complexes of erbium and ytterbium with amine, phosphate and phosphine oxide ligands Ln(NH2R)3Cl3, Ln[OP(NMe2)2NHR]3Cl3, Ln[OP(OPh)2NHR]3Cl3, [RCH2CH2CH2Si(OEt)3], Ln[OP(OPh)3]3Cl3, Ln[OP(CH2CH2CF3)3]3Cl3 and Ln[OP(CHCHPh)3]3Cl3 have been synthesised, and their absorption spectra have been measured in both films and solutions.

The Investigation of Erbium Complexes and Erbium Doped Materials

AbstractErbium ion (Er3+) doped materials are of great interest for their optical amplification, lasing and frequency up-conversion properties. When preparing such materials, a major problem that often arises is the formation of Er-rich oxide clusters inducing optical quenching. The materials prepared at low Er3+-ion concentrations to overcome the problem have severely reduced the optical yield. Such clustering might be avoided by preparing suitable precursors. If Er is encapsulated with proper materials, clustering can be avoided and higher doping levels can be achieved. In this study, erbium phenoxide complex was obtained by metathesis reaction of erbium chloride (ErCl3) with potassium phenoxide (KOPh). And heterometallic complexes were also synthesized by encapsulation of the Er with Al or Ti derivatives. The complexes were characterized by elemental analysis, infrared and nuclear magnetic resonance spectroscopic analysis. Their crystal structures were determined by X-ray single crystal diffraction analysis. In addition, the Er-doped organic-inorganic matrices using the erbium complexes were investigated about their optical properties.

Synthesis and Photophysical Properties of Luminescent Erbium(III) Complexes Based on Coumarin Derivatives for Advanced Photonics Applications

The luminescent Er(III)-chelated complexes based on coumarin derivatives such as coumarin-3-carboxylic acid and coumarin 343 were prepared by ligand-exchange reaction in the presence of ErCl3and potassium coumarin derivative salts. The chemical structures of the present complexes were confirmed by elementary analysis, thermal gravimetric analysis. FT-IR, absorption and emission spectroscopies. The coumarin-based Er(III)complexes exhibited the near IR emission, corresponding to the characteristic4I13/2 → 4I15/2transition of trivalent erbium ions, taking place in the region of 1512 or 1530 nm. Their PL intensity also depends on the degree of the spectral overlap between the emission band of coumarin derivative and the absorption band of Er ion.

Near-infrared Fourier transform room-temperature photoluminescence of erbium complexes

A modified Fourier transform (FT) Raman bench spectrometer designed for the detection of weak light emission in the 800–1700 nm wavelength region has been used to demonstrate the advantages of FT spectroscopy for measuring near-infrared photoluminescence spectra of lanthanide complexes with a good resolution and very good sensitivity. This apparatus has been tested with an ultraviolet laser source (325 nm) on three standard erbium complexes. The I13/24→4I15/2 emission of tris-(acetylacetonato) (1,10 phenanthroline) erbium [Er(acac)3(phen)], tris-(4,4,4,-trifluoro-1-(2 thenoyl)-1,3-butenedione) (1,10 phenanthroline) erbium [Er(TTFA)3(phen)] and tris(8-hydroxyquinolinato) erbium [Erq3] has thus been recorded in solution and in the solid state and compared with literature.

Synthesis and crystal structure of [ nBu 4N][Er(pic) 4] · 5.5H 2O: a new infrared emitter

The new erbium(III) complex of picolinic acid (Hpic), [ n Bu 4N][Er(pic) 4] · 5.5H 2O, was synthesized and the crystal structure determined by single-crystal X-ray diffraction. The compound was further characterized using IR, Raman, 1H NMR and elemental analysis. The picolinate ligands (pic −) are coordinated through N, O-chelation to the erbium cations, as shown by X-ray diffraction and spectroscopic results, leading to an eight coordinate complex. Photoluminescence measurements were performed for this compound which exhibits infrared emission.

Photoluminescence of mesoporous silica films impregnated with an erbium complex

Transparent mesoporous silica films were prepared by sol-gel spin coating on silicon wafers at room temperature. An erbium complex, erbium tris 8-hydroxyquinoline (ErQ), was homogeneously impregnated into the pores of the mesoporous silica films, and its concentration was easily controlled by using a solution immersing technique. The ErQ-impregnated mesoporous silica films show a room-temperature photoluminescence at 1.5 µm.

Indirect excitation of Er3+ in sol-gel hybrid films doped with an erbium complex

Transparent sol-gel hybrid films doped with erbium tris 8-hydroxyquinoline were prepared using methyltriethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane as precursors. We obtain a strong 1.53-μm Er3+ luminescence with a wide full width at half-maximum and no thermal quenching. Comparison of absorption of the film with the pump wavelength dependence of Er3+ luminescence intensity indicates the presence of an efficient indirect excitation path for Er3+ via organic ligands.

Novel erbium complexes with low band-gap for infrared laser and optical amplifiers

Two new NIR luminescent erbium(III) crown-ethers have been synthesized and studied by optical spectroscopies. Both the complexes show absorption bands in the visible spectral region (absorption edge at about 500 nm and 600 nm) and exhibit the NIR lanthanide luminescence following excitation of the organic ligand. The absorption bands of these complexes, well in the visible region of the spectrum, make them ideal candidates as active molecules for efficient optically pumped laser and optical amplifier by excitation with commercially available lasers.

LIGAND-SENSITIZED AND UP-CONVERSION PHOTOLUMINESCENCE IN VACUUM-DEPOSITED THIN FILMS OF AN INFRARED ELECTROLUMINESCENT ORGANIC ERBIUM COMPLEX

We observed ligand-sensitized and up-conversion photoluminescence (PL) in vacuum-deposited thin films of an infrared electroluminescent organic erbium complex, erbium (III) tris(8-hydroxyquinoline) (ErQ). The PL intensity at 1.55 µm was increased by three orders of magnitude by changing the photo-excited species from Er3+ to the organic ligand (Q). This strong enhancement was ascribable to ligand-sensitized PL based on the excited state energy transfer from Q to Er3+. We simultaneously detected up-conversion PL from Er3+ in the ultraviolet region. The up-conversion PL is emitted due to excited state absorption, which indicates that vacuum-deposited ErQ thin films are weak electron-phonon coupling systems.

Sorption of Lanthanum, Terbium, and Erbium Complexes of Some Mono- and Bisazoderivatives of Chromotropic Acid in the Presence of Surfactants

Optimal conditions were found for the sorption of lanthanum, terbium, and erbium complexes of some derivatives of chromotropic acid: Arsenazo II, Arsenazo III, Carboxyarsenazo, and Chlorophosphonazo III on Silochrom C-120 silica gel in the presence of tetrabutylammonium bromide (TBA). Diffuse reflection coefficients and molar coefficients of the chromaticity functions of the adsorbates were determined. It was demonstrated that the preconcentration of complexes on the solid matrix in the presence of TBA increases the sensitivity of the determination of rare-earth elements by a factor of 5–50 in comparison with solutions; the use of chromaticity characteristics further increases the sensitivity by 1.5–2 orders of magnitude.

Erbium-silicon-oxide Nano-complexes Prepared by Wet Chemical Synthesis

AbstractAn entirely new method to fabricate optically active and carrier-mediated excitable erbium complexes on silicon is presented. The Er-Si-O nano-complexes are formed by spin-coating a Si (100) substrate with an ErC13 solution, followed by a rapid thermal oxidation and annealing sequence (RTOA). Intense room-temperature luminescence is observed from the Er-Si-O nano-complexes, with a line width as narrow as 4 meV at room temperature. The Er emission at 1.53 μm can be excited both directly and through photo carriers. Formation and optical activation of the Er-Si-O nano-complexes are discussed. In addition, an application of the wet chemical synthesis technique to incorporation of the Er-Si-O nano-complexes into nano-porous silicon waveguides is demonstrated.

Erbium Surface-Enriched Silicon Nanowires

The synthesis of silicon nanowires containing erbium in a discrete layered structure has been achieved. These wires are prepared by the pyrolysis of silane and a volatile erbium complex on a gold catalyst surface, with the relative size of the wire and sample crystallinity affected by the timing in which erbium is introduced into the reactant stream. Products were characterized by field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray analysis. Given their ability to demonstrate the desired near-infrared luminescence at 1540 nm, the synthesis of these erbium surface-enriched Si nanostructures provides a synthetic strategy for new types of optically active layered platforms for studies in fundamental photophysics, carrier transport, and nanophotonics.

Visible absorption spectra of the 4f electron transitions of neodymium, praseodymium, holmium and erbium complexes with fleroxacin and their analytical application.

The absorption spectra of the 4f electron transitions of neodymium, praseodymium, holmium and erbium complexes with fleroxacin in the presence of cetylpyridinium chloride were studied by normal and derivative spectrophotometry. Their molar absorptivity at the maximum absorption bands are about 5.3 (at 571 nm) times greater for neodymium, 2.8 (at 483 nm) times greater for praseodymium, 12.6 (at 448.5 nm) times greater for holmium and 9.7 (at 519 nm) times greater for erbium than those in the absence of complexing agents. The second-derivative spectrum is used both to eliminate the interference from other rare earths and to improve the sensitivity. Beer's law is obeyed from 3.0 - 70 microg ml(-1) for neodymium and holmium, from 6.0 - 70 microg ml(-1) for erbium, and from 12.0 - 70 microg ml(-1) for praseodymium. The relative standard deviations are 1.9% and 1.5% for 7.5 microg ml(-1) of neodymium and holmium, and 2.1% and 1.6% for 15.0 microg ml(-1) of praseodymium and erbium, respectively. Their detection limits (signal-to-noise ratio = 2) are 3.2 microg ml(-1), 1.3 microg ml(-1), (1.1) microg ml(-1) and 2.5 microg ml(-1) for praseodymium, neodymium, holmium and erbium, respectively. A new system for the simultaneous determinations of the praseodymium, neodymium, holmium and erbium in rare earth mixtures with good accuracy and selectivity is proposed.