Gadolinium Atoms Research Articles

The Rare Earth Metal-Rich Indides RE 4RhIn (RE = Gd–Tm, Lu)

The rare earth-transition metal-indides RE 4RhIn (RE = Gd–Tm, Lu) were prepared by arc-melting of the elements and subsequent annealing. Single crystals were grown via slowly cooling of the samples. The indides were investigated via X-ray powder diffraction and several structures were refined from X-ray single crystal diffractometer data: $F{\bar 4}3m$ , a = 1370.7(9) pm, wR2 = 0.049, 428 F 2 values for Gd4RhIn, a = 1360.3(6) pm, wR2 = 0.028, 420 F 2 values for Tb4RhIn, a = 1354.5(2) pm, wR2 = 0.041, 380 F 2 values for Dy4RhIn, a = 1349.2(3) pm, wR2 = 0.029, 410 F 2 values for Ho4RhIn, a = 1342.5(5) pm, wR2 = 0.037, 403 F 2 values for Er4RhIn, a = 1337.8(3) pm, wR2 = 0.038, 394 F 2 values for Tm4RhIn with 14 variable parameters per refinement, and a = 1329.7(3) pm for Lu4RhIn. In this new structure type, the rhodium atoms have a trigonal prismatic rare earth coordination. Condensation of the RhRE 6 prisms leads to a three-dimensional network which leaves voids that are filled by regular In4 tetrahedra (317 pm In–In distance) in Gd4RhIn. The indium atoms have twelve nearest neighbors (3 In + 9 RE) in icosahedral coordination. The gadolinium atoms build up a three-dimensional, adamantane-like network of condensed, face-sharing empty octahedra.

Structure and properties of Gd 4Pd 10In 21

Gd 4Pd 10In 21 was synthesized from the elements in a glassy carbon crucible in an induction furnace and investigated by X-ray powder and single crystal diffraction: C2/ m, a = 2293.3(2), b = 444.49(3), c = 1934.3(1) pm, β = 133.00(1)°, wR2 = 0.0496, 1564 F 2 values, and 106 variable parameters. The five crystallographically independent palladium atoms have all a trigonal prismatic coordination. Together, the palladium and indium atoms build up a three-dimensional [Pd 10In 21] network in which the gadolinium atoms fill distorted pentagonal channels. Magnetic susceptibility measurements show that Gd 4Pd 10In 21 orders antiferromagnetically at T N = 14.2(1) K. Two further magnetic transitions were found at temperatures 11.8 and 6.4 K, respectively. Below T irr = 10 K, strong irreversibility between ZFC and FC magnetic susceptibilities are observed. The zero-field specific heat measurements show a clear peak around the magnetic transition temperatures T N. Measured quadrupole interaction constants by 155Gd Mössbauer spectroscopy give estimations for the V zz component of the electric field gradient tensor at both gadolinium sites in Gd 4Pd 10In 21.

A disymmetric terpyridine based ligand for the formation of luminescent di-aquo lanthanide complexes

The synthesis of ligand H3 based on a disymmetrically substituted terpyridine core functionalised by a carboxylic acid in the 6-position and a bis(carboxymethyl)aminomethyl function in the 6''-position is described. The coordination behaviour of this heptadentate (4N/3O) ligand with lanthanide cations (Ln=Eu, Gd and Tb) was studied in solution showing the formation of complexes with [Ln] stoichiometry. Complexes with general formula [Ln(H2O)2] were isolated from neutral water solutions containing equimolar amounts of cations and ligands, and the complexes were characterized in the solid state (elemental analysis, IR) and in solution (mass spectrometry). The photo-physical properties of the luminescent complexes of Eu and Tb were studied in water solution by means of absorption, steady state and time-resolved emission spectroscopies. Evolution of the luminescence lifetimes of the Eu and Tb complexes in H2O and D2O reveals the presence of two water molecules coordinated in the first coordination sphere of the cations. Despite this important hydration number, the overall luminescence quantum yields of the complexes remained elevated, especially in the case of Tb (Phi=22.0 and 6.5% respectively for Tb and Eu). Upon crystallisation the Gd complex formed dimeric species in which two gadolinium atoms are each heptacoordinated by one ligand, the coordination sphere being completed by a single water molecule and a bridging carboxylate function, pointing to different behaviours in the solid and liquid states.

Amplitude contrast of a single gadolinium atom reconstructed by a wave field restoration method

Single gadolinium atoms in fullerenes encapsulated in a single-wall carbon nanotube were observed by a wave field restoration method based on three-dimensional Fourier filtering in transmission electron microscopy. Single gadolinium atoms were clearly resolved not only in the imaginary part image but also in the real part image of the exit wave field due to an improved signal-to-noise ratio by Fourier filtering and resolution enhancement by correcting spherical aberration and twofold astigmatism. This result indicates that the present method has potential to clarify compositional details of the sample by using their image contrasts.

Reactions of Gadolinium Atoms and Dimers with CO: Formation of Gadolinium Carbonyls and Photoconversion to CO Activated Molecules

Reactions of gadolinium atoms and dimers with carbon monoxide molecules in solid argon have been studied using matrix isolation infrared absorption spectroscopy. Mononuclear Gd(CO)x (x = 1-3) and dinuclear Gd2(CO)x (x = 1, 2) gadolinium carbonyls formed spontaneously on annealing. The Gd(CO)x complexes are CO terminal-bonded carbonyls, whereas the Gd2CO and Gd2(CO)2 carbonyl complexes were characterized to have asymmetrically bridging and side-on-bonded CO, which are drastically activated with remarkably low C-O stretching frequencies. The cyclic Gd2(mu-C)(mu-O) and Gd3(mu-C)(mu-O) molecules in which the C-O triple bond is completely cleaved were also formed on annealing. The Gd2(CO)2 complex rearranged to the more stable c-Gd2(mu-O)(mu-CCO) isomer, which also has a four-membered ring structure with one CO being completely activated.

Growth, structural, IR and magnetic studies of a new gadolinium metaphosphate, Gd(PO 3) 3

The crystal structure of gadolinium metaphosphate Gd(PO 3) 3 has been established by X-ray diffraction. This compound crystallizes in the orthorhombic system (space group C222 1, Z = 4) with cell parameters: a = 8.4530 (3), b = 11.0576 (4) and c = 7.1952 (2) Å. The structure was refined to R 1 = 0.0234 and w R 2 = 0.0502 using 2180 independent reflections ( I > 2 σ( I)). Phosphorus atoms are in slightly irregular tetrahedral oxygen coordination, gadolinium atoms are in considerably distorted dodecahedral oxygen coordination. Formally, the 3D framework in the structure can be described by the PO 4 tetrahedra sharing corners to form helical chains and the GdO 8 polyhedra sharing edges in a zigzag fashion. The shortest Gd–Gd distance is 4.174 (2) Å. The infrared spectrum of the title compound recorded at room temperature in the frequency range of 400–4000 cm −1, confirm the atomic arrangement within the structure. Below T C = 25 K, the magnetic susceptibility evolution is characteristic of a ferromagnetic order. In the high-temperature region above 100 K, the susceptibility follows a Curie–Weiss law with C = 7.91 cm 3 K mol −1 and θ = 9.96 K.

Silver-gadolinium polytetraphosphate AgGd(PO 3) 4 synthesis, structural study, IR spectroscopy and conductivity investigation

Crystals of a new silver-gadolinium, AgGd(PO 3) 4, have been synthesized for the first time by a flux method. The structure [monoclinic, P2 1/ n, a = 7.2378(2) Å, b = 13.0913(5) Å, c = 9.8136(4) Å, β = 90.494(1)°, V = 929.83(6) Å 3 and Z = 4] was solved by a three-dimensional Patterson function and refined to R 1 = 0.0399 ( w R 2 = 0.0885 ) on the basis of 3270 unique observed reflexions using 164 parameters. AgGd(PO 3) 4 is isostructural to NaLa(PO 3) 4, AgLa(PO 3) 4 and AgNd(PO 3) 4. The structure is based upon long chain polyphosphate running along the shortest unit-cell direction and made up of PO 4 tetrahedra (with a period of four tetrahedra) sharing two corners, linked to the polyhedra of gadolinium and silver by common oxygen atoms to the chains. This type of organisation gives rise to a three-dimensional framework. Gadolinium atoms have an eight-fold coordination while silver atoms have approximately six oxygen neighbours. Infrared spectrum of AgGd(PO 3) 4 at room temperature, investigated in the frequency range 400–1500 cm −1, confirms the atomic arrangement within the structure. The electrical conductivity of AgGd(PO 3) 4 has been measured on pellets of the polycrystalline powder and evaluated as a function of temperature. The conductivity of this phase was quite low and the values of 4.01 × 10 −7 and 1.10 × 10 −6 Ω −1 cm −1 were obtained at 803 and 873 K, respectively.

Condensation of Rare Earth Pyrazolates: The Dimeric, Trimeric and Polymeric Units [Gd2(Pz)6(PzH)4], [Nd3(Pz)9(PzH)2] and

Solvent free high-temperature oxidations of rare earth metals with the heterocycle pyrazole as well as in low to non-coordinating solvents were investigated to isolate intermediate stages between monomeric and polymeric pyrazolates of the lanthanides. Reaction conditions were tuned according to simultaneous DTA/TG and temperature dependent X-ray powder diffraction experiments on known monomeric and polymeric pyrazolates, that gave rise to the idea that further structure intermediates could be isolated. Reactions in 1,2,3,4-tetrahydroquinoline gave the dimeric complex [Gd2(Pz)6(PzH)4](PzH)(Tech) (1) as well as the triangular complex [Nd3(Pz)9(PzH)2](PzH)(Tech)2 (2). The solvent free melt synthesis resulted in a new polymeric form of (3) (pyrazole, PzH = C3H3NNH; pyrazolate anion, Pz− = C3H3NN−; 1,2,3,4-tetrahydroquinoline, Tech = C9H13N). All three compounds contain coordinating pyrazolate amide groups and pyrazole molecules the latter decreasing in numbers upon condensation of the building units. According to simultaneous DTA/TG/MS investigations the condensation process can be identified with the release of pyrazole molecules.1 consists of dimeric molecules containing trivalent gadolinium with a C.N. of eight. The two gadolinium atoms show different coordination polyhedra. Only σ coordination and bridging is found for 1. 2 consists of trimeric molecules containing trivalent neodymium. The neodymium atoms also exhibit different coordination polyhedra with C.N.s of eight and nine. Both π and σ coordination is found for 2, the π coordinating pyrazolate ligands acting as lids of the triangular units. Topological analysis of the electron localization function (ELF) for 2 calculated at the scalar-relativistic DFT level reveals only weakly covalent π donor η5-Pz–Nd interactions compared to the stronger covalent σ donor Pz–Nd interactions. The topological analysis of both, the ELF and the electron density reveals no significant differences of the respective charges of the Nd atoms. 3 exhibits a one-dimensional chain structure with EuII and a C.N of ten. It can thus be addressed the β form of the referring formula with a new arrangement of the coordinating ligands. Like the α form 3 shows σ and π coordination of pyrazole and pyrazolate ligands. Simultaneous DTA/TG analysis reveals that the low-temperature α form shows a phase transition into the β form between 110 °C and 130 °C. The three compounds were investigated by low-temperature single crystal X-ray analysis, Mid IR and Far IR spectroscopy.

Atomic Level Characterization Based on Focus Modulation Electron Microscopy

Defocus image modulation processing and three-dimensional Fourier filtering methods are compared from the viewpoint of application to high-resolution phase transmission electron microscopy. Both methods can successfully correct the spherical aberration in TEM by image processing using through-focus images resulting in resolution improvement from the Scherzer resolution limit to the information limit. Comparing the processed images demonstrates that the potential to determine localized atomic structures between the two methods is at the same level when the sample thickness is thin. However, the achieved signal-to-noise ratio is better in images processed by the three-dimensional Fourier filtering method because the filtering process in Fourier space effectively reduces quantum noises involved in the original images. Spherical aberration-free phase observation by the latter method clearly shows the existence of individual gadolinium atoms in C82 molecules encapsulated in single wall carbon nanotubes. It is demonstrated that the three-dimensional Fourier filtering method works effectively for atomic level characterization even when a sample consisting of light atoms is observed under the condition of a low electron dose.

Microstructural evolution of nickel nanoparticle catalysts supported on gadolinium-doped ceria during autothermal reforming of iso-octane

The microstructure and composition of a nanoparticle Ni catalyst supported on gadolinium-doped ceria (Ce1−xGdxO(4−x)/2) were studied using transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The support of the fresh catalyst exhibits a homogenous aggregation of crystalline grains, with sizes ranging between 20 nm and 50 nm. The crystalline structure of the fresh catalyst support is of the CeO2 phase, in which gadolinium atoms exist in a solid solution of CeO2. Nickel in the fresh catalyst is highly dispersed and forms granular crystals that are 5–30 nm in size on the surface of the ceria support. The support of the used catalyst exhibits a bimodal distribution of grains in which smaller grains have similar structure and morphology as those in the fresh catalyst, while the larger sized grains appear dull and exhibit nonfaceted crystal morphology resulting either from the sintering of a number of CeO2 grains or by the occupation of highly defective crystals of Ce2O3 and CeO phases. A thin amorphous layer of carbon also covers most of the larger grains in the used catalyst. The Ni particles could not be imaged by TEM in the used catalyst, but energy dispersive x-ray spectroscopy (EDX) detected their presence. The XPS analysis of the catalyst samples suggests the participation of lattice O atoms from the ceria support in the catalytic reaction. The XPS data also show the presence of carbonate species and a higher hydrocarbon concentration in the used catalyst.

Electron-spin-resonance study of gadolinium borosilicide: A rare-earth ladder compound

Electron-spin-resonance (ESR) measurements were utilized as a microscopic probe to gain more information about the magnetic transition in the REB50 compounds. A gadolinium phase (Gd3+=S87∕2) was synthesized and used for this measurement. GdB50 will not form due to the large size of gadolinium, but we have found that with the addition of a small amount of Si, the lattice constants expand and an isotypic borosilicide is formed which can accommodate the gadolinium phase. This phase has a ladderlike arrangement of the gadolinium atoms and although a broad peak in the specific heat has been observed previously at T∼4K, the transition could not be discerned in the susceptibility due to an inevitable low-temperature tail. However, the ESR absorption intensity was found to exhibit a sharp drop at TN=7K, clearly indicating the magnetic transition. The g factor also exhibited a temperature dependence, decreasing rapidly below 30K, indicating the growth of short-range correlation. The temperature dependence of the ESR linewidth was significantly different from that of a three-dimensional antiferromagnetic system, being indicative of the exchange narrowing of a one-dimensional classical spin system. These results indicate that the Gd ions magnetically form pairs along the bond-alternating ladder which is the direction of the second-nearest metal-metal spacing.

Biocompatible Nanotemplate-Engineered Nanoparticles Containing Gadolinium: Stability and Relaxivity of a Potential MRI Contrast Agent

In this article, we use a nanotemplate engineering approach to prepare biodegradable nanoparticles composed of FDA-approved materials and possessing accessible gadolinium (Gd) atoms and demonstrate their potential as a Magnetic Resonance Imaging (MRI) contrast agent. Nanoparticles containing dimyristoyl phosphoethanolamine diethylene triamine penta acetate (PE-DTPA) were prepared using 3.5 mg of Brij 78, 2.0 mg of emulsifying wax and 0.5 mg of PE-DTPA/ml from a microemulsion precursor. After the addition of GdCl3, the presence of Gd on the surface of nanoparticles was characterized using inductively coupled plasma atomic emission spectroscopy and Scanning Transmission Electron Microscopy (STEM). The in vitro relaxivities of the PE-DTPA-Gd nanoparticles in different media were assessed at different field strengths. The conditional stability constant of Gd binding to the nanoparticles was determined using competitive spectrophotometric titration. Transmetallation kinetics of the gadolinium ion from PE-DTPA-Gd nanoparticles with zinc as the competing ionic was measured using the relaxivity evolution method. Nanoparticles with a diameter of approximately 130 nm possessing surface chelating functions were made from GRAS (Generally Regarded As Safe) materials. STEM demonstrated the uniform distribution of Gd3+ on the surface of the nanoparticles. The thermodynamic binding constant for Gd3+ to the nanoparticles was approximately 10(18) M(-1) and transmetallation studies with Zn2+ yielded kinetic constants K1 and K(-1) of 0.033 and 0.022 1/h, respectively, with an equilibrium constant of 1.5. A payload of approximately 10(5) Gd/nanoparticle was achieved; enhanced relaxivities were observed, including a pH dependence of the transverse relaxivity (r2). Nanoparticles composed of materials that have been demonstrated to be hemocompatible and enzymatically metabolized and possessing accessible Gd ions on their surface induce relaxivities in the bulk water signal that make them potentially useful as next-generation MRI tumor contrast enhancement agents.

Crystal and molecular structure of a new gadolinium nitrate complex with furancarboxylic acid and dipyridyl

The gadolinium nitrato complex with α-furancarboxylic acid (FA) and 2,2′-dipyridyl (Dipy) has been synthesized. According to X-ray diffraction results, the complex is composed of the [Gd(FA)2(NO3)(Dipy)]2 dimers. The crystals are triclinic: a = 9.942(2) A, b = 10.231(2) A, c = 11.037(2) A, α = 85.50(3)°, β = 75.71(3)°, γ = 69.82(3)°, Z = 1. Two gadolinium atoms are linked by four carboxylate groups of furancarboxylic acid molecules. Each gadolinium atom is coordinated to seven oxygen atoms (five belonging to the FA carboxyl groups and two belonging to the bidentate nitrate group) and to two nitrogen atoms (from Dipy).

Measurement of the velocity distribution of neutral atoms using laser-induced fluorescence

Laser-induced fluorescence has been used to measure the Doppler-shifted emission spectra in the atomic beam of gadolinium. The velocity distribution of gadolinium atoms that was deduced from these spectra shows good agreement with a Maxwellian distribution. Based on this good agreement, temperatures of the evaporating source have also been estimated. A new experimental method has been devised in our measurements, which can also be used for other multiline systems similar to gadolinium. This method allows one to effectively eliminate the distorting interference present in Doppler profile measurements for the multiline systems mentioned above.

Photoluminescence from Gd-implanted AlN and GaN Epilayers

ABSTRACTGaN and AlN thin films were implanted with gadolinium (Gd)atoms and characterized using deep ultra-violet (UV) photoluminescence(PL). The Gd-implanted samples were annealed at temperatures up to 1178K in a flowing N2 gas to facilitate recovery of implantation-related damage. Using the output at 195 nm from a quadrupled Ti:sapphire laser, narrow PL emission was observed at 318 nm from the Gd- implanted AlN thin films. This emission is characteristic of the lowest energy 4f transition of the trivalent Gd ion. A boarder emission band, also centered at 318 nm, was observed under excitation at 266 nm. No PL emission was observed from the Gd-implanted GaN thin films at either the bandedge or due to a 4f transition. The dependence of the UV emission on AlN sample temperature was systematically studied. The peak PL emission intensity decreased by less that a factor of 3 over the temperature range of 10 K to 300 K. Decay transients of the UV emission were measured indicating that the lifetime of this emission is very fast.

Syntheses and Structure of Gd3Rh1.940(7)In4

The gadolinium–rhodium–indide Gd3Rh1.940(7)In4 was prepared by arc-melting of the elements and subsequent annealing in a corundum crucible in a sealed silica tube. Gd3Rh1.940(7)In4 adopts the hexagonal Lu3Co1.87In4 type, space group \(P{\bar 6}\), a = 781.4(5), c = 383.8(3) pm, wR2 = 0.0285, BASF = 0.375(1) (merohedric twinning via a twofold axis (xx0)), 648 F 2 values, 22 variables. The structure is derived from the well known ZrNiAl type through an ordering of rhodium and indium atoms on the Ni2 sites. The Rh/In ordering forces a reduction of the space group symmetry from \(P{\bar 6}62m\) to \(P{\bar 6}\), leading to merohedric twinning for the investigated crystal. The Rh1 site has an occupancy of only 94.0(7)%. The investigated crystal had a composition Gd3Rh1.940(7)In4. The main geometrical motif are three types of centered, tricapped trigonal prisms, i.e., [Rh1In26Gd3], [Rh2Gd6In23], and [In1Gd6In23]. The shortest interatomic distances occur for Rh–In (276–296 pm) followed by In–In (297 pm). Together, the rhodium and indium atoms build up a three-dimensional [Rh1.940(7)In4] network, in which the gadolinium atoms fill slightly distorted pentagonal channels. The crystal chemistry of Gd3Rh1.940(7)In4 is discussed on the basis of a group-subgroup scheme.

Synthesis and characterization of a novel Gd(III)–Cu(II) dinuclear adduct

Two novel Gd(III)–Cu(II) dinuclear complexes have been prepared by the acid–base reaction between Gd(hfa) 3 and Cu(2,2-oxomac) ( 1, Cu(2,2-oxomac)Gd(hfa) 3) and between Gd(hfa) 3 and Cu(3,2-oxomac) ( 2, Cu(3,2-oxomac)Gd(hfa) 3). These complexes have been characterized by elemental analysis and infrared spectroscopy. The structure of 1 has been determined by X-ray diffraction. The copper atom is square pyramidal, bound to the four planar nitrogen atoms of the macrocycle and weakly bound to the oxygen atom of a dimethylformamide (dmf) molecule. The gadolinium atom is at the center of a tricapped trigonal prism. The nine-coordinate gadolinium atom is bound to six oxygen atoms of three hfa ligands, the two oxamide oxygen atoms of the copper macrocycle, and one oxygen atom of a second coordinated dmf molecule. Unsymmetric binding of the copper macrocycle to gadolinium leads to a distortion in the bridging atoms not observed in reactions of the copper macrocycles with transition metal hfa’s.

Measurement of isotope shifts of gadolinium levels by laser-induced fluorescence spectroscopy

The results of isotope shift measurements for the gadolinium atom both in a hollow cathode lamp and in an atomic beam are described. Using laser-induced fluorescence spectroscopy, the measurements were performed for four transitions, which are related to the configurations 4f75d6s29D to 4f75d6s6p9D and 4f75d6ss6p9FD.

Structure, magnetic properties and Mössbauer spectroscopy of GdRhSn

Polycrystalline GdRhSn was obtained by a reaction of the elements in a sealed tantalum tube in a high-frequency furnace. The sample was investigated by X-ray diffraction on powder and a single crystal: ZrNiAl type, space group P 6 ¯ 2 m , a = 752.6 ( 1 ) , c = 386.38 ( 6 ) pm, w R 2 = 0.0353 , 454 F 2 values and 14 variables. Both crystallographically independent rhodium atoms have a tricapped trigonal prismatic coordination, i.e. [Rh1Sn 3Gd 6] and [Rh2Sn 6Gd 3]. The shortest distances occur for the Rh–Sn contacts (274 and 283 pm). Together the rhodium and tin atoms build up a three-dimensional [RhSn] network in which the gadolinium atoms fill distorted hexagonal channels. The magnetic and electronic properties of GdRhSn have been studied by means of magnetic AC and DC susceptibility measurements as well as 119Sn and 155Gd Mössbauer spectroscopy. A transition from a paramagnetic to an antiferromagnetic state with non-collinear magnetic ordering takes place at T N = 16.0 ( 1 ) K .

The High‐Temperature Modification of GdNiIn2 ‐ An Intergrowth Structure of MgCuAl2‐Related Slabs

AbstractThe high‐temperature modification of GdNiIn2 was prepared by arc‐melting of the elements and subsequent annealing of the sample at 1270 K. Crystals of HT‐GdNiIn2 were grown with a special annealing program. HT‐GdNiIn2 was investigated by X‐ray diffraction on powders and single crystals. This indide crystallizes in a new structure type, space group Cmcm, a = 433.4(3), b = 1803(1), c = 2983(2) pm, wR2 = 0.1142, 2306 F2 values, and 90 variable parameters. All nickel atoms in the HT‐GdNiIn2 structure have a distorted trigonal prismatic coordination by gadolinium and indium atoms. From a geometrical point of view, the structure of HT‐GdNiIn2 may be described as an intergrowth of distorted LT‐GdNiIn2 slabs with MgCuAl2 structure. The Ni‐In and In‐In contacts have the shortest interatomic distances within the HT‐GdNiIn2 structure. The nickel and indium atoms form a three‐dimensional [NiIn2] polyanion in which the gadolinium atoms fill distorted pentagonal channels. An initial approximation formula may be written as Gd3+[NiIn2]3‐ therefore.