Incorporation Of Gd Research Articles

Modifying optical, electric and magnetic properties of multifunctional Gd3+-doped Ba4La0.95Er0.05TiNb9O30 ceramics

Tetragonal tungsten bronze (TTB) structure Ba4La0.95−xEr0.05GdxTiNb9O30 (BLETN:Gd3+) with different Gd3+ concentrations have been synthesized, and their structural, up-conversion photoluminescence (UC-PL), dielectric, ferroelectric (FE), and magnetic properties have been investigated in this work. With the incorporation of Gd3+, it is found that a BLETN:Gd3+ system exhibits multifold responds to the external electric, magnetic, and optical stimuli. Specially, enhanced UC-PL intensity, obvious relaxor-like FE state, and paramagnetic (PM) feature have been simultaneously realized in this single phase TTB-type compound. It is believed that the BLETN:Gd3+ system involving bright UC emission and promising electromagnetic properties may act as a potential material for future multifunctional device applications.

Pulsed EPR spectroscopy distance measurements of DNA internally labelled with Gd(3+)-DOTA.

Gd(3+) is increasingly used in EPR spectroscopy due to its increased intracellular stability and signal-to-noise ratios. Here we present the incorporation of Gd(3+)-DOTA into internal positions in DNA. Distance measurements via pulsed Electron Paramagnetic Resonance (EPR) spectroscopy in vitro and in cellula proved enhanced stability and efficiency compared to nitroxide labels.

Superparamagnetic behaviour and evidence of weakening in super-exchange interactions with the substitution of Gd3+ ions in the Mg–Mn nanoferrite matrix

The Gd3+ substituted Mg–Mn nanoferrites with generic formula Mg0.9Mn0.1GdxFe2−xO4 (x=0.05, 0.1, 0.2, 0.3) have been prepared for the first time by self-ignited solution combustion method. The X-ray analysis confirmed the formation of single phase cubic spinel structure. Gd3+ substitution has resulted in an increase in the crystallite size (13.4–16.1nm) and lattice parameter (8.35–8.38Å). The M–H and ZFC–FC study revealed that all nanoferrites are of superparamagnetic in nature. The saturation magnetization (Ms) has been observed to decrease with the incorporation of Gd3+ ions. The cation’s distribution has been estimated by using the magnetic characterization method. The magnetic properties such as initial permeability (μi) and magnetic loss tangent (tan δ) have been investigated as a function of frequency. The initial permeability has been observed to be almost constant with frequency and in each nanoferrite an onset of resonance is observed. In addition, very low values of ‘tan δ’ were obtained.

Pr and Gd co-doped bismuth ferrite thin films with enhanced multiferroic properties

Pr and Gd co-modified Bi 0⋅95−xPr x Gd 0⋅05FeO 3 (x = 0⋅00, 0⋅05, 0 ⋅10) (BPGFO) thin films on Pt(111) / Ti /SiO 2 /Si(100) substrates were prepared by a sol-gel together with spin coating technique. A detailed study of electrical and magnetic properties of these thin films is reported. X-ray diffraction analysis shows that, with an increase in Pr content, the crystal structures of BPGFO thin films retain rhombohedral (R3c) symmetry accompanied by structure distortion. Polarization-electric field hysteresis loops of these thin films demonstrate that the incorporation of Pr and Gd into the Bi site of BiFeO 3 thin film could enhance the ferroelectric performance. Compared to other thin films, the optimal ferroelectric behaviours in Bi 0⋅85Pr 0⋅1Gd 0⋅05FeO 3 thin film are ascribed to its large dielectric constant, low dissipation factor and low leakage current density. Room temperature magnetization-magnetic field curves of these thin films indicate that all the samples are of paramagnetic behaviours and the enhanced saturation magnetic properties can be found.

Multifunctional rare-Earth vanadate nanoparticles: luminescent labels, oxidant sensors, and MRI contrast agents.

Collecting information on multiple pathophysiological parameters is essential for understanding complex pathologies, especially given the large interindividual variability. We report here multifunctional nanoparticles which are luminescent probes, oxidant sensors, and contrast agents in magnetic resonance imaging (MRI). Eu(3+) ions in an yttrium vanadate matrix have been demonstrated to emit strong, nonblinking, and stable luminescence. Time- and space-resolved optical oxidant detection is feasible after reversible photoreduction of Eu(3+) to Eu(2+) and reoxidation by oxidants, such as H2O2, leading to a modulation of the luminescence emission. The incorporation of paramagnetic Gd(3+) confers in addition proton relaxation enhancing properties to the system. We synthesized and characterized nanoparticles of either 5 or 30 nm diameter with compositions of GdVO4 and Gd0.6Eu0.4VO4. These particles retain the luminescence and oxidant detection properties of YVO4:Eu. Moreover, the proton relaxivity of GdVO4 and Gd0.6Eu0.4VO4 nanoparticles of 5 nm diameter is higher than that of the commercial Gd(3+) chelate compound Dotarem at 20 MHz. Nuclear magnetic resonance dispersion spectroscopy showed a relaxivity increase above 10 MHz. Complexometric titration indicated that rare-earth leaching is negligible. The 5 nm nanoparticles injected in mice were observed with MRI to concentrate in the liver and the bladder after 30 min. Thus, these multifunctional rare-earth vanadate nanoparticles pave the way for simultaneous optical and magnetic resonance detection, in particular, for in vivo localization evolution and reactive oxygen species detection in a broad range of physiological and pathophysiological conditions.

Fabrication and characterization of compositionally graded Bi1−x GdxFeO3 thin films

Abstract An undoped BiFeO3 thin film, Gd doped Bi0.95Gd0.05FeO3 thin film with a constant composition, Gd up-graded doped Bi1−x GdxFeO3 and Gd down-graded doped Bi1−x GdxFeO3 thin films were successfully grown on Pt (111)/Ti/SiO2/Si (100) substrates using a sol-gel and spin coating technique. The crystal structure, ferroelectric and dielectric characteristics as well as the leakage currents of these samples were thoroughly investigated. The XRD (X-Ray Diffraction) patterns indicate that all these thin films consist of solely perovskite phase with polycrystalline structure. No other secondary phases have been detected. Clear polarization-electric field (P-E) hysteresis loops of all these thin films demonstrate that the incorporation of Gd3+ into the Bi site of BFO thin film have enhanced the ferroelectric performance of pure BiFeO3 thin film, and the Gd down-graded doped Bi1−x GdxFeO3 thin film has the best ferroelectric properties. Compared to other thin films, the optimal ferroelectric behavior of the Gd down-graded doped Bi1−x GdxFeO3 thin film results from its large dielectric constant, low dissipation factor and low leakage current.

Enhanced luminescence in Ln³⁺-doped Y₂WO₆ (Sm, Eu, Dy) 3D microstructures through Gd³⁺ codoping.

Microstructures of Y2WO6 were prepared by applying a hydrothermal synthesis in the presence of sodium dodecyl sulfate (SDS) surfactant, after which the materials were heat-treated at a temperature of 1100 °C. When prepared at pH 3, the spherical 3D microstructures were built from nanosized particles. Raising the pH gave materials built from differently shaped building blocks, which influenced the final architecture. These materials, similarly to other previously investigated and reported rare-earth tungstate materials, were found to show very interesting luminescence properties. However, quantum yield (QY) values have scarcely been reported for such materials. In this work, a detailed study of the photoluminescence characteristics, decay times, and quantum yields of Y2WO6 doped with Sm(3+), Eu(3+), and Dy(3+) is presented. When doped with different concentrations of Ln(3+) ions, the luminescence properties of the samples changed. The 2.5% Dy:Y2WO6 sample gave white-light emission and showed a QY of 17%. For the optimal lanthanide-ion concentrations, the systems were codoped with 2% and 10% Gd(3+) ions to test the possible enhancement of luminescence through energy transfer from W-O and/or Gd(3+) to Ln(3+). The Eu(3+),Gd(3+)-codoped system showed QYs as high as 79%. The Sm,Gd-codoped system showed the highest enhancement of QY. After incorporation of Gd(3+) ions, the 2.5% Sm_10% Gd:Y2WO6 materials showed a QY approximately 2.4 times larger than that of the 2.5% Sm:Y 2WO6 material.

Facile synthesis of catalytically active CeO 2 –Gd 2 O 3 solid solutions for soot oxidation

CeO2–Gd2O3 oxides were synthesized by a modified coprecipitation method and subjected to thermal treatments at different temperatures to understand their thermal behaviour. The obtained samples were characterized by XRD, BET, TEM, Raman and TPR techniques. Catalytic efficiencies for oxygen storage/release capacity (OSC) and soot oxidation were evaluated by a thermogravimetric (TG) method. XRD and Raman results indicated the formation of Ce0.8Gd0.2 O 2−δ (CG) solid solutions at lower calcination temperatures, and TEM studies confirmed nanosized nature of the particles. Raman studies further confirmed the presence of oxygen vacancies and lattice defects in the CG sample. TPR measurements indicated a facile reduction of ceria after Gd3+ addition. Activity studies revealed that incorporation of Gd3+ into the ceria matrix favoured the creation of more structural defects, which accelerates the oxidation rate of soot compared to pure ceria.

Ultrasonic assisted preparation of lanthanide-oleate complexes for the synthesis of multifunctional monodisperse upconversion nanoparticles for multimodal imaging.

The synthesis of multifunctional monodisperse upconversion nanoparticles (UCNPs) of high quality is highly desired for bioimaging. Lanthanide-oleate complexes are excellent precursors for the synthesis of high quality UCNPs with controllable size and shape. In this work, lanthanide-oleate complexes were prepared by an ultrasonic assisted procedure, and used as precursors for further synthesis of multifunctional monodisperse NaYF4:59%Yb(3+),0.5% Tm(3+)@NaYF₄:20%Gd(3+) nanoparticles without the need for further purification. Heavy doping of Yb(3+) in the core and incorporation of Gd(3+) in the shell made the UCNPs promising for upconversion luminescence (UCL), magnetic resonance (MR) and computed tomography (CT) multimodal imaging. The nanoparticles were further functionalized with bombesin peptide for in vivo UCL/MR/CT imaging of prostate tumors.

${\rm HfO}_{2}$ Based High-$k$ Inter-Gate Dielectrics for Planar NAND Flash Memory

We investigate the use of HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based high- k materials as inter-gate dielectric in hybrid floating gate based memory cells for planar NAND flash. The incorporation of Al or Gd in the HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> allows reaching higher k values as compared with pure HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> through different crystalline characteritics. However, a difficult compromise is to be found between the k value and low leakage due to grain boudaries in a material with large crystalline proportions. Hence, HfGdO reaches a k value as high as 23 but shows important leakage that translates into early program saturation and room temperature charge loss. The HfAlO has more moderate k of ~ 16 but shows lower leakage leading to improved device performances. Finally, a three layer stack where a high-k HfAlO layer is encapsulated into Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> thinner layers shows overall best compromise in terms of program/erase window and retention.

TH-C-141-02: Imaging of Targeted Cancer Therapy Using Multifunctional Liposomal Nanoprobes and MRI

Purpose: To develop a multifunctional liposomal nanoprobe that selectively binds to epidermal growth factor receptor (EGFR) over‐expressing tumor cells with an encapsulating a magnetic resonance (MR) imaging contrast agent, gadolinium (Gd) and conjugating an EGFR‐specific monoclonal antibody within liposome particles. The function of the probe is to target cancer overexpressing cells so that uptake of anti‐EGFR targeted therapeutic agents may be imaged. We tested our nanoprobe using a head and neck cancer cell line and Cetuximab, an anti‐EGFR drug. Methods: Encapsulation of Gd within liposome particles was optimized by combining Dipalmitoylphosphatidylcholine (DPPC), cholesterol, 1,2‐dioleoyl‐sn‐glycero‐3‐phospho‐ethanolamine‐N‐(biotinyl)(sodium salt) (DOPE‐Biotin), and Diethylenetriaminepentaacetic acid‐bis(stearylamide)‐Gd (DTPA‐BSA‐Gd). Avidin was included in the liposomal membrane to conjugate with biotin‐modulated anti‐EGFR antibody. The probes were characterized for size, surface potential and structural integrity with dynamic light scattering (DLS) and transmission electronic microscopy (TEM). In‐vitro targeting specificity of the probe was evaluated using fluorescence microscopy by comparing the binding capacity of a fluorescence‐labeled probe in a human head and neck cancer cell line, 15B (high EGFR overexpression) and a human embryonic kidney cell line, HEK293 (low EGFR control). Finally, the in vitro applicability of MRI contrast Gd within the probe was demonstrated by detecting cell‐bound particles with MR imaging. Results: Using TEM scanning, the probes were near spherical in shape and identical in particle size (∼100nm). The surface potential was +5.13mV. The EGFR‐specific targeting assay with fluorescence‐labeled probes showed significantly high occupancy of the probe on the surface of 15B cells in comparison with HEK293 cells. The T1 relaxation time of this EGFR‐specific probe attached to15B cells was measured to be 379.3 ms, shorter than that of control vector without anti‐EGFR conjugation (516.2 ms). Conclusion: We have demonstrated targeting specificity of a nanoprobe in discriminating high and low EGFR‐expressing cells. The incorporation of Gd revealed the cell‐targeting under MR imaging.

EPR assessment of protein sites for incorporation of Gd(III) MRI contrast labels

We have engineered apolipoprotein A-I (apoA-I), a major protein constituent of high-density lipoprotein (HDL), to contain DOTA-chelated Gd(III) as an MRI contrast agent for the purpose of imaging reconstituted HDL (rHDL) biodistribution, metabolism and regulation in vivo. This protein contrast agent was obtained by attaching the thiol-reactive Gd[MTS-ADO3A] label at Cys residues replaced at four distinct positions (52, 55, 76 and 80) in apoA-I. MRI of infused mice previously showed that the Gd-labeled apoA-I migrates to both the liver and the kidney, the organs responsible for HDL catabolism; however, the contrast properties of apoA-I are superior when the ADO3A moiety is located at position 55, compared with the protein labeled at positions 52, 76 or 80. It is shown here that continuous wave X-band (9 GHz) electron paramagnetic resonance (EPR) spectroscopy is capable of detecting differences in the Gd(III) signal when comparing the labeled protein in the lipid-free with the rHDL state. Furthermore, the values of NMR relaxivity obtained for labeled variants in both the lipid-free and rHDL states correlate to the product of the X-band Gd(III) spectral width and the collision frequency between a nitroxide spin label and a polar relaxation agent. Consistent with its superior relaxivity measured by NMR, the rHDL-associated apoA-I containing the Gd[MTS-ADO3A] probe attached to position 55 displays favorable dynamic and water accessibility properties as determined by X-band EPR. While room temperature EPR requires >1 m m Gd(III)-labeled and only >10 µ m nitroxide-labeled protein to resolve the spectrum, the volume requirement is exceptionally low (~5 µl). Thus, X-band EPR provides a practical assessment for the suitability of imaging candidates containing the site-directed ADO3A contrast probe.

Bimodal Imaging Using Neodymium Doped Gadolinium Fluoride Nanocrystals with Near-Infrared to Near-Infrared Downconversion Luminescence and Magnetic Resonance Properties.

Here we report the synthesis, characterization and application of a multifunctional surface functionalized GdF3:Nd3+ nanophosphor that exhibits efficient near infrared (NIR) fluorescence as well as magnetic properties, which can be utilized for bimodal imaging in medical applications. The nanoparticles are small with an average size of 5 nm and form stable colloids that last for several weeks without settling, enabling the use for several biomedical and photonic applications. Their excellent NIR properties, such as nearly 11 % quantum yield of the 1064 nm emission, make them ideal contrast agents and biomarkers for in vitro and in vivo NIR optical bioimaging. The nanophosphors which were coated with poly(maleic anhydride- alt-1-octadicene) (PMAO) were implemented in cellular imaging and show no significant cellular toxicity for concentrations up to 200 μg ml-1. Furthermore, the incorporation of Gd into the nanocrystalline structure supplies exceptional magnetic properties, making them ideal for use as magnetic resonance imaging (MRI) contrast agents. The utility of these NIR emitting nanoparticles in infrared bioimaging and as contrast agent in magnetic resonance imaging was demonstrated by confocal imaging, magnetic resonance and tissue experiments.

The role of Gd2O3 and Y2O3 in corrosion of soda lime silicate glass

Corrosion of soda-lime-silicate glasses containing Gd and Y has been carried out by solution and solid analyses, to investigate the effect of Gd and Y on the chemical durability of silicate glass. The results showed that the incorporation of Gd and Y into silicate glass decreases glass constituent releases and increases chemical durability. The morphology of glass surface and thickness of altered layer were observed that the degree of corroding of the soda lime silicate glass doped with Gd and Y was significantly less than that of the base glass. EDS microanalyses revealed that the effect of Gd and Y on the altered layer is different, the non-congruent dissolution process is observed in the case of Gd doped glasses. Besides, the improving effect of Gd and Y on acid and alkaline resistance of silicate glasses can attribute to their larger ionic radius and higher cation field strength.

Facile sol-gel combustion synthesis and photoluminescence enhancement of CaZrO3:Sm3+ nanophosphors via Gd3+ doping

CaZrO3:Sm and CaZrO3:Sm, Gd nanophosphors were synthesized by a facile and efficient sol-gel combustion method. Their structure and optical properties were studied. The photoluminesce (PL) results showed that the phosphor could be efficiently excited by irradiation at wavelengths in the visible light region (350-430 nm). The CaZrO3:Sm nanophosphor exhibited strong yellow-green, orange and red emissions with peak wavelength centered at 565 nm (4G5/2→6H5/2), 601 nm (4G5/2→6H7/2) and 645 nm (4G5/2→6H9/2), respectively. The incorporation of Gd3+ ions could greatly improve the luminescence intensity. The highest emission intensity was observed with 2 mol.% Gd3+ doped CaZrO3:3 mol.% Sm powder. The material had potential application in the development of materials for LED's and other optical devices in the visible region.

Influence of trivalent Gd and Dy codoping on the structure and electrical conductivity of pyrochlore-type Sm2Zr2O7

SmDy1−xGdxZr2O7 (0 ≤ x ≤ 1.0) ceramics are prepared by solid state reaction method at 1973 K for 10 h in air. The crystal structure and microstructure of SmDy1−xGdxZr2O7 ceramics are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). All the SmDy1−xGdxZr2O7 ceramics (x = 0.2, 0.4, 0.6, 0.8, 1.0) exhibit a pyrochlore structure except for SmDyZr2O7 ceramic. SmDyZr2O7 ceramic has a defective fluorite structure. The incorporation of Gd3+ facilitates a structural evolution from a defective fluorite into an ordered pyrochlore-type structure. Electrical conductivity of SmDy1−xGdxZr2O7 ceramics has been investigated by impedance spectroscopy over a frequency range of 1 Hz to 8 MHz from 673 to 1173 K. The grain conductivity of SmDy1−xGdxZr2O7 ceramics follows the Arrhenius behavior. The grain conductivity of SmDy1−xGdxZr2O7 ceramics increases obviously with increasing Gd3+ content in the temperature range of 673–1073 K, and the optimal grain conductivity value is 1.90 × 10−2 S cm−1 in the composition of SmGdZr2O7 ceramic at 1173 K. All the SmDy1−xGdxZr2O7 ceramics are purely oxide ionic conductors in the test temperature range.

Structural, magnetic, and electrical properties of Gd-doped BiFeO3 nanoparticles with reduced particle size

Pure and Gd-doped BiFeO3 nanoparticles have been synthesized by sol–gel method. The significant effects of size and Gd-doping on structural, electrical, and magnetic properties have been investigated. X-ray diffraction study reveals that the pure BiFeO3 nanoparticles possess rhombohedral structure, but with 10% Gd-doping complete structural transformation from rhombohedral to orthorhombic has been observed. The particle size of pure and Gd-doped BiFeO3 nanoparticles, calculated using Transmission electron microscopy, has been found to be in the range 25–15 nm. Pure and Gd-doped BiFeO3 nanoparticles show ferromagnetic character, and the magnetization increases with decrease in particle size and increase in doping concentration. Scanning electron microscopy study reveals that grain size decreases with increase in Gd concentration. Well-saturated polarization versus electric field loop is observed for the doped samples. Leakage current density decreases by four orders by doping Gd in BiFeO3. The incorporation of Gd in BiFeO3 enhances spin as well as electric polarization at room temperature. The possible origin of enhancement in these properties has been explained on the basis of dopant and its concentration, phase purity, small particle, and grain size.

Ferroelectricity in Gd-Doped HfO2 Thin Films

The incorporation of Gd into HfO2 thin films is shown to induce ferroelectricity. A significant influence of electric field cycling on both polarization as well as small-signal capacitance-voltage measurements can be observed. X-ray diffraction measurements are supported by infrared absorption analysis and give further evidence of the previously proposed non-centrosymmetric transition phase of space group Pbc21.

The Role of Rare Earth Metals on Effective Work Function Modulation of Nickel Fully-Silicided Gate/High-k Dielectric Stacks for n-Channel Metal Oxide Semiconductor Device Applications

It was found that the structural properties with gadolinium (Gd) and europium (Eu) incorporation into nickel (Ni) fully silicided (FUSI) gate electrodes are markedly different and resulted in different degrees of effective work function modulation. It was found that Ni–Gd alloys tend to form stable compounds during silicidation and produced a Si-rich layer with amorphous/nanocystalline structure near the FUSI gate electrode/high-k dielectric interface. This compositional and structural change is the main mechanism responsible for effective work function modulation with Gd incorporation. However, in the case of Europium, Eu atoms tend to segregate outside the Ni-FUSI layer during silicidation and resulted in a uniform NixSiy layer with Eu pile-up layer at the FUSI gate electrode/high-k dielectric interface. This pile-up is believed to be the main cause of effective work function modulation with Eu incorporation. It was also found that the incorporation of Gd and Eu metals into Ni-FUSI gate can remotely scavenge the interfacial oxide layer resulting in lower equivalent oxide thickness (EOT) of the device.

Effect of growth conditions on magnetic and structural properties in Gd‐doped GaN layers grown by plasma‐assisted molecular beam epitaxy

AbstractEffects of growth conditions on structural and magnetic properties in Gd‐doped GaN layers grown by plasma‐assisted molecular beam epitaxy have been investigated. It is found that the growth of Gd‐doped GaN layers with atomically flat surface morphologies requires relatively high Ga fluxes compared with the growth of GaN. For these Gd‐doped GaN layers grown under Ga‐rich conditions, (0002) diffraction spots of GaGdN appear and shift toward low scattering angle side depending on the concentration of Gd, indicating the expansion of the c‐axis lattice constant due to the incorporation of Gd. In contrast, for the Gd‐doped GaN layers grown under N‐rich condition, just the (0002) diffraction spot of GaN is observed irrespective of the concentration of Gd. Although all the samples show hysteresis in the M‐H curves at room temperature, the samples grown under the Ga‐rich conditions have higher coercevities and larger saturation magnetizations than the samples grown under the N‐rich conditions. Based on the findings, we will discuss the origin of ferromagnetic behaviour observed in Gd‐doped GaN (© 2012 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)