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In this study, un-doped MgO–MgAl2O4 and Gd3+-doped MgO–MgAl2O4 nanocomposites have been synthesized via co-precipitation method. The effects of Gd3+ contents on the structureal and optical properties of MgO–MgAl2O4 nanocomposites were investigated using scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction, Fourier-transform infrared and UV–VIS spectroscopies. HRTEM shows that MgO–MgAl2O4 powder are uniform spherical shape nanoparticles. The XRD shows that the nanocomposites consist of face-centered cubic MgAl2O4 and MgO crystal structures. The average crystallite sizes of MgO–MgAl2O4 nanocomposites are in the range of 8–40 nm. The quantitative elemental analysis by EDX illustrates that the nanocomposite samples are nearly stoichiometric MgO–MgAl2O4 48 to 52%, respectively. Scanning electron microscopy was used to study the surface morphology of MgO–MgAl2O4 nanocomposites that reveals the existence of both the individual nanoparticles and their aggregates. The optical bandgap was decreased with the presence of Gd3+ from 4.85 to 3.66 eV for 0.0 and 3% of Gd3+ content, respectively. The photoluminescence of un-doped and Gd-doped MgO–MgAl2O4 nanocomposite showed a green emission in the range (545–565 nm).

NaMnF3:Yb,Er and NaMnF3:Yb,Er@NaGdF4:xEu (x = 0, 0.3, 0.6, and 0.9) samples were synthesized by a simple hydrothermal method. The as-obtained NaMnF3:Yb,Er particles show a single red emission under the irradiation of infrared light (980 nm), due to the energy exchange transfer process between Mn2+ ions and Er3+ ions. Notably, further growth of NaGdF4:Eu on the basis of NaMnF3:Yb,Er enhanced the green up-conversion luminescence of Er3+ ions, which gradually shifted from red to green with the increase of the Gd3+ ion doping amount. In addition, NaMnF3:Yb,Er@NaGdF4:Eu exhibits red color under ultraviolet excitation (397 nm). These results provide a possible means for controlling the luminescence properties of the lanthanide doped up-conversion system. The luminescent film synthesized with NaMnF3:Yb,Er@NaGdF4:Eu can show different luminescent colors under different light irradiation (near infrared and ultraviolet), which indicates that they have potential applications in multi-mode anti-counterfeiting.

Herein, we have developed the thin Gd@PbI2 films on FTO via a facile spin coating route and subjected to various studies. The formation of (001) oriented hexagonal phase Gd:PbI2/FTO films was confirmed by X-ray diffraction & FT-Raman spectroscopy analyses. The size was determined through Scherrer formula in 11–16 nm range. The doping of Gd and its homogeneity was tested and approved by EDX and SEM e-mapping studies. The Gd doping impact on surface morphology was inspected via SEM images and found very low dimension grains formation throughout the films area. Tauc’s formula was employed to obtain energy gap and found in 2.46–2.74 eV for all Gd@PbI2 films. Absorption and refractive indices were estimated in 0.034–1.2 and 1.4–11 between 395 and 2400 nm wavelength regions. Respective dielectric constant and loss values were noted between 3.5 and 112, and 0.13 and 1.4, signify high dielectric constant and low loss values. The optical conductivity was calculated of 1016 order for all Gd@PbI2 films. SELF and VELF related values were also determined. The values of nonlinear optics related parameters were also calculated and revealed that the grown films are potential candidates for opto-nonlinear devices.

Layered dilute magnetic semiconductors are expected as promising candidates for next-generation electric devices, however, the low saturation magnetization limits their applications. Doping of semiconductors can effectively tune the magnetic and optical properties, which further influence on spintronic and optoelectronic applications. The discovery of layered materials opens a new door for spintronic application due to their unique properties. Here, the layered Gd3+ doped SnO crystals are synthesized via a simple hydrothermal method, with morphologies ranging from square shapes to four-pointed star shapes. We investigated the UV–vis absorption spectra, photoluminescence spectra and magnetic characteristics of the samples. The as-obtained Gd3+ doped SnO crystals show robust ferromagnetism at room temperature. From the first-principles calculations results, the substitution Gd dopants and the O vacancies work together to introduce the ferromagnetism. Our results demonstrate the Gd3+ doping tunability of SnO, a ferromagnetic layered material, as a functional material for spintronics and optoelectronics.

Gd3+ and Cr3+ codoped zinc gallogermanate (ZGGO:Cr3+, Gd3+) nanoparticles were prepared by a hydrothermal method in combination with a subsequent vacuum annealing. It is found that Gd3+ doping not only endows ZGGO:Cr3+ nanoparticles with magnetic property, but also results in the decreased nanoparticle size and the enhanced near infrared (NIR) afterglow intensity. Strikingly, amino group functionalized SiO2 layer coating enabling Gd3+ doped ZGGO:Cr3+ nanoparticles well dispersed in water enhances persistent luminescence which is because of the weakened quenching effect of OH− groups in water. Validation of high-quality bioimaging was demonstrated using the surface functionalized Gd3+ doped ZGGO:Cr3+ nanoparticles dispersed in human serum albumin (HSA). In particular, it is found that the longitudinal relaxivity (7.33 s−1(mM)−1) of Gd3+ doped ZGGO:Cr3+ nanoparticles is higher than that of commercial magnetic resonance imaging (MRI) contrast agent (Gd-DTPA) and it leads to the high-quality in vitro T1-weigthed images.

In order to investigate the influence of Gd3+ doping on the photocatalytic activity of BiFeO3, BiFeO3 and BiFeO3:Gd3+ photocatalysts were fabricated by the sol-gel process. The phase, photocatalytic hydrogen production, microstructure, optical and photoelectrochemical properties of the fabricated photocatalysts were investigated. BiFeO3:Gd3+ photocatalyst has a larger ability for the hydrogen production in photocatalysis process than that of BiFeO3. The reason of the higher photocatalytic activity of BiFeO3:Gd3+ photocatalyst was revealed by the measurements of UV–Vis diffuse reflectance spectra, photocurrent curves and electrochemical impedance spectra. Moreover, the magnetic properties of BiFeO3 and BiFeO3:Gd3+ photocatalysts were also investigated to show the easy separation. These results in current work indicate that BiFeO3:Gd3+ is an excellent photocatalyst and has potential applications in photocatalytic hydrogen production.

To enhance the electrochemical properties of the Mn-based lithium-rich layered cathode materials, Li1.20[Mn0.54−xGd x Ni0.13Co0.13]O2 (x = 0, 0.01, 0.02 and 0.03) were synthesized by using the carbonate co-precipitation method. The X-ray diffraction, scanning electron microscope, galvanostatic charge–discharge tests and electrochemical impedance spectroscopy techniques have been carried out to investigate the influences of the Gd3+ doping modification. And the results showed the lower cation mixing degree and superior electrochemical properties were obtained for the LMNCO by the Gd3+ doping. With the Gd3+ doping amount increasing, the capacity retentions after 100 cycles enhanced from 88.5 to 90.9% and then decrease to 86.7% with x = 0.01, 0.02 and 0.03, respectively. While the un-doped LMNCO only delivered the capacity retention of 85.1%. Besides, the discharge capacity of Li1.20[Mn0.52Gd0.02Ni0.13Co0.13]O2 was 29.4 mAh g−1 larger than that of un-doped sample at 5 C high rate. The electrochemical impedance spectroscopy results indicated that the Gd3+ doping modification could restrain the growth speed of charge transfer impedance of LMNCO during the charge and discharge process.

The blue emitting long afterglow phosphor (LAG) Li2ZnGeO4, Li2ZnGeO4:Nd3+, Li2ZnGeO4:Pr3+, and Li2ZnGeO4:Gd3+ were synthesized via traditional high temperature solid-state reaction in air atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectroscope (PL), luminescence decay, long afterglow spectroscope (LAS) and thermal luminescence spectroscope (TSL) were utilized to characterize and analyze the physical properties of the synthesized phosphors. All phosphor samples present bright blue emission with different intensity under a 254 nm UV lamp. The photoluminescence properties revealed the rare earth ionic (Nd3+, Pr3+ and Gd3+) doping enhanced the luminescence intensity of the host emission and did not change profiles of emission spectra. Further, luminescence decay study showed that the luminescence lifetime of Li2ZnGeO4:R3+ (R = Nd, Pr, Gd) phosphors was increased, indicating energy transform occurred in the processes. After light source was removed, all phosphor sample show evident triple exponential decay behavior. Thermal simulated luminescence study indicated that persistence afterglow of Li2ZnGeO4:Nd3+, Li2ZnGeO4:Pr3+, and Li2ZnGeO4:Gd3+ phosphors were originated from suitable electron or hole traps resulted from rare earth ions (Nd3+, Pr3+ and Gd3+) doping in the Li2ZnGeO4 host.

One-micron-sized uniform red-phosphor spheres of an (Y,Gd)BO3 ternary system have been converted from their colloidal moydite precursor spheres facilely synthesized using modified homogenous precipitation. The moydite spheres, possessing the composition (Y0.95−xGdxEu0.05)(B(OH)4)CO3 (0 ≤ x ≤ 0.50), are orthorhombic in structure. Gd3+ is more effective than Y3+ in raising nucleation density, leading to a decreased average size of the precursor particles with a higher addition of Gd3+. The lattice parameters, a and b, increase linearly with increasing Gd incorporation, while the c value shrinks with a higher Gd content. The moydite spheres completely decomposed into hexagonal orthoborate upon heating to 800 °C, while retaining the spherical shape and excellent dispersion of the original particles. However, they lost their spherical shape and underwent significant aggregation at a higher temperature. The lattice constant of (Y0.95−xGdxEu0.05)BO3 calcined at 800 °C follows Vegard's law and increases linearly with an increase in the value of x from 0 to 0.30. Upon excitation with 207 nm wavelength light, (Y0.95−xGdxEu0.05)BO3 spheres show typical Eu3+ emission, with the strongest emission at 610 and 627 nm (5D0 → 7F2 transition of Eu3+) and almost the same CIE chromaticity coordinates of (∼0.632, ∼0.373). The incorporation of Gd3+ resulted in enhanced luminescence intensity and shorter lifetimes (∼5.77–6.56 ms). The optimized doping concentration of Gd3+ is 15 at%. The uniform phosphor spheres obtained in this work are expected to have wide applications for the contemporary interest in high-resolution display technologies.

Gadolinium-doped cadmium oxide (CdO) thin films were fabricated by spray pyrolysis technique using a perfume atomizer on the glass and silicon substrates at 350 °C. The effect of increasing Gd concentration on the electrical, morphological, optical, and structural properties of deposited films was analyzed. Structural analysis of the pristine and doped CdO thin films showed cubic structures with preferred orientation of (200) direction. The estimated crystallite values ranged from 15 to 21 nm. The structural parameters like dislocation density, microstrain, a number of crystallites per unit area, and texture coefficient were also studied. Scanning electron microscope (SEM) images showed uniformly oriented and cauliflower-like nanostructures grown on the glass substrate for 3at.%-doped CdO films. The doped films' optical transmittance is found to be initially increased and systematically decreased with respect to doping concentrations. The band gap value is in the range of 2.42–2.30 eV for various Gd-doping concentrations (0, 1, 3, and 5%), respectively. The photoluminescence spectra (PL) of films were studied at room temperature and confirms the visible and green emission’ peaks are at wavelength 463 and 528 nm, respectively. From the Hall Effect studies, it proved that all the CdO films belong to an n-type degenerate semiconductor, and the low electrical resistivity value was around 3.64 × 10−4 Ω cm. The n-CdO/p-Si structure with different doping concentrations was subjected to photoconductivity studies and found that it is the maximum of 3% Gd concentration. Higher values of photo responsivity and quantum efficiency was found ~365 mA/W and ~76.64%, respectively, for 3at.% Gd-doped CdO films.

Rare earth nitrate as the raw material, NaY/GdF4 upconversion luminescent nanoparticles were prepared by hydrothermal method, its diameter is about 200nm. By changing the Gd3+ doping amount achieved NaYF4 transition from the tetragonal to hexagonal phase, and the upconversion emission intensity can be improved by optimizing Gd3+ content. In 980nm excitation light source for the fluorescence test showed that the introduction of Gd3+ can effectively promote size reduction of NaY/GdF4 crystals and decrease luminous intensity. Through mechanism analysis we know that is related to nanosize effect. At the same time, we discussed the upconversion luminescence mechanism of NaY/GdF4 nanocrystals luminous intensity in different wavelength bands and the SEM show the morphology transformation from spherical to double-flower.

The multiplexing capacity of conventional fluorescence materials are significantly limited by spectral overlap and background interference, mainly due to their short-lived fluorescence lifetimes. Here, we adopt a novel Gd3+ doping strategy in NaYF4 host materials, realized tuning of upconversion photoluminescence (UCPL) lifetimes at selective emissions. Time-correlated single-photon counting (TCSPC), was applied to measure the photoluminescence lifetimes accurately. We demonstrated the large dynamic range of lifetimes of upconversion nanoparticles with good upconversion quantum yields, mainly owing to the dominance of high efficient energy transfer upconversion mechanism. The exceptional tunable properties of upconversion materials allow great potential for them to be utilized in biotechnology and life sciences.

We report the influence of glassing solvent deuteration and Gd3+ doping on 13C dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) performed on [1-13C] sodium acetate at B0 = 5 T and 1.2 K. Our data reveal that at 5 T, glassing solvent deuteration still results in a 40% improvement of the 13C DNP signal when a large electron spin resonance (ESR) linewidth 4-oxo-TEMPO free radical is used, but results in a 60% decrease of the DNP signal in the case of a sample doped with small ESR linewidth trityl OX063. An addition of a trace amount of the Gd3+ complex Gd–HP–DO3A led to a negligible slight decrease on the 13C polarization TEMPO-doped sample, but is still relatively beneficial for the trityl-doped sample with 30% improvement of the DNP-enhanced 13C polarization. These findings indicate that while these DNP optimization steps are still valid at 5 T, the effects are not as pronounced as observed in 13C DNP at B0 = 3.35 T. These DNP results at 5 T are discussed thermodynamically within the framework of the thermal mixing model of DNP.

The effect of doping of Gd3+ ions into Ce: SrF2 on luminescence properties was investigated in (Gd, Ce): SrF2 nanoparticle powders synthesized via the co-precipitation method, which contained fixed amount of Ce3+ ions and variable amounts of Gd3+ ions. (Gd, Ce): SrF2 nanoparticle powders showed UV range emissions under λex = 273 nm and λex = 298 nm excitation. Photoluminescence emission, excitation, and lifetime measurements revealed the existence of Ce3+ → Gd3+ radiative energy transfer and provided evidence to the prevailing effect of Ce3+ in excitation and emission in the (Gd, Ce) co-doped system due to the existence of fully allowed 4f-5d transitions. The presence of Gd3+ was shown to affect the crystal field and symmetry around Ce3+ ions and enhances the absorption efficiency by two-fold. Furthermore, (Gd, Ce): SrF2 transparent ceramics with 13.2% of in-line optical transmittance in the UV spectral range was obtained via the vacuum hot-pressing method. The increase in the UV luminescence emission intensity of Ce3+ in presence of Gd3+, as well as the ability to process (Gd, Ce): SrF2 as transparent ceramics, are what make (Gd, Ce): SrF2 a promising material for optical applications in the UV region.

&beta, NaYF4 microcrystals co-doped with Yb3+, Er3+/Tm3+, and Gd3+ ions were synthesized via a hydrothermal method using rare-earth chlorides as the precursors. The SEM and XRD data show that the doped &beta, NaYF4 form uniform hexagonal prisms with an approximate size of 600&ndash, 800 nm. The partial substitution of Y by Gd results in size reduction of microcrystals. Upconversion luminescence spectra of microcrystals upon 980 nm excitation contain characteristic intra-configurational ff bands of Er3+/Tm3+ ions. An addition of Gd3+ ions leads to a significant enhancement of upconversion luminescence intensity with maxima at 5 mol % of dopant.

Herein, the study on structural, optical and electrical properties of various concentrations (0, 1, 3, 5 wt %) of Gadolinium doped zinc sulphide (Gd: ZnS) thin films by simple nebulizer spray pyrolysis (NSP) method has been presented. X-ray diffraction patterns displayed that the prepared films are of polycrystalline hexagonal structures with (102) a preferred orientation. SEM images showed a smooth surface with nano sized spherical grains. Enhancement of surface roughness viewed from AFM images. Presence of Zn, S, and Gd elements in prepared samples were confirmed through EDAX and Elemental mapping images. E1 (LO), (LA + LO), 2TO, 2LO and 3LO mode of vibrations were explored in the Raman spectrum. Newly, the luminescent center raised at red region (725 nm) was seen in RT Photoluminescence studies. Optical spectra illustrated band gap enrichment and high transparent film (average of 86%) both in Vis-IR region. Activation energy measured from four-point probe method also discussed here.

The results of fabrication process and characterization of Bi1-xGdxFeO3 (x = 0.05, 0.07, 0.10) ceramics are reported in the paper. The samples were prepared by standard solid state reaction method from the mixture of oxides: Bi2O3, Fe2O3 and Gd2O3. The influence of Gd substitution on the microstructure and density of Bi1-xGdxFeO3 was studied. Phase composition and structure of the obtained samples were investigated by Xray diffraction. It turns out that the Bi1-xGdxFeO3 solid solutions with x = 0.05 and 0.07 crystallize in trigonal structure characteristic of BiFeO3 compound. For the sample with x = 0.1, beside the major trigonal phase, 6% of orthorhombic phase typical for GdFeO3 was detected. Hyperfine interaction parameters were studied by M?ssbauer spectroscopy. M?ssbauer results proved that the spin cycloid characteristic of BiFeO3 compound gradually disappears when substituting Gd3+ ions at the Bi3+ sites.

A core-shell structured PANI/Li0.5Fe2.5−xGdxO4 (0.0 ⩽ x ⩽ 0.2) nanocomposite material has been prepared by in situ emulsion polymerization method as is evidenced by X-ray diffraction and Scanning electron microscopy. Transmission electron microscopy confirms the formation of core (ferrite)-shell (PANI matrix) structured nanocomposite material. These materials have been investigated for electromagnetic interference (EMI) shielding in the X-band (8–12 GHz) frequency range. Higher shielding effectiveness (SET) of around 42 dB has been obtained in this study than many other systems reported recently. The main contributing factor has been ascribed to the absorption (SEA = 34–36 dB) instead of reflection (SER = 4.0–6.3 dB), owing to the enhancement in the electromagnetic attributes. Effect of increasing Gd3+ ion content in PANI/Li0.5Fe2.5−xGdxO4 nano-composite has been analyzed for the electromagnetic attenuation. It depicts a decreasing trend of SE with Gd3+ doping except for x = 0.2 sample. This has been attributed to the increasing particle size of ferrites, resulting into the decrease in dielectric (ε′ = 59–56 at 9.5 GHz) attributes owing to increased grain to grain contact. Higher value of SE for x = 0.2 sample can be due to the secondary phase formation in ferrite, which increases the number of grain boundaries and thereby increases ε′. However, increasing magnetization with Gd3+ doping is less likely a factor affecting shielding as compared to dielectric attributes. Such a material with high SE demonstrates the potential of these materials for making future microwave shields. Keywords: PANI, Nano-ferrites, Magnetic properties, Dielectric properties, EMI shielding

The rare earth gadolinium (Gd3+) ions doped nanocrystalline cobalt-zinc ferrites chemically formulated as Co0.7Zn0.3GdxFe2-xO4 (x = 0–0.1) were synthetically prepared by sol-gel self-ignition process. The characterization the ferrite samples was performed by powder x-ray diffraction method. The analysis of x-ray diffractograms (XRD) reveals formation of cubic spinel phase without presence of any ambiguity peak. The calculated particle size of the samples varies between 18 nm and 28 nm showing decreasing trend with Gd3+ doping. The distribution of cations analysed from XRD data propose occupancy of tetrahedral (A)-site by Zn2+ and Fe3+ while octahedral [B]-site by Fe3+, Gd3+ and Co2+ ions. The morphology of the ferrites was studied from the SEM images. The nanocrystalline particles arranged in layers with presence of porous structure can be observed in the SEM images. The particles of spherical shape with mean diameter of 27 nm were observed in the TEM image. The confirmation of peaks revealed by XRD data was performed by SAED image of the ferrite. The fringe width of the lattice fringe in HRTEM confirms formation of pure spinel phase in the Gd3+ doped Co-Zn ferrite. The VSM data analysed for measurement of magnetic parameters viz. coercivity, retentivity and saturation magnetization. The compositional variation of magnetization with Gd3+ doping reveals spin canting due to non-collinearity of spins of (A) and [B]-site. The Y-K angles calculated from cation distribution data were increased with Gd3+ doping due to spin canting. The variation of coercivity with Gd3+ doping was in accordance with the variation of anisotropy constant. The frequency variation of real part (μ') and imaginary part (μ") of μ* (complex permeability) were studied as a function of Gd3+ composition and frequency. The permeability was influenced by magnetic and structural parameters. The domain wall movement and spin rotations were responsible for magnetism in the ferrites.

In this article, transparent oxyfluoride glass ceramics containing β -NaYF4 nanocrystals were successfully prepared via Gd3+ doping. Compared to conventional non-doped glasses, the thermal treatment temperature required for the precipitation of β -NaYF4 nanocrystals can be lowered with the doping of Gd3+. Furthermore, under the same thermal treatment condition, more β -NaYF4 nanocrystals were precipitated in Gd3+ doped ones, which greatly improves the luminescence efficiency of rare earth doped glass ceramics. Possible mechanism for the Gd3+ doping induced enhanced upconversion luminescence phenomenon was proposed, based on thorough structural and optical characterizations. The results revealed that the doping of Gd3+ ions could decrease the crystallization activation energy and promote the formation of Y-F-Na bonding, which helps the precipitation of β -NaYF4 nanocrystals. Consequently, a large enhancement in upconversion luminescence was achieved. Moreover, the strategy can be successfully applied to the development of other glass ceramic systems for various optoelectronic applications.

Gd3+ doped Bi2MoO6 nanoplate crystals were fabricated by solvothermal combined calcination method. The effects of Gd3+ doping with different concentrations on the texture, crystal and optical properties of Bi2MoO6 were investigated by N2 physical adsorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet–visible diffuse reflection spectrum (UV–vis DRS), photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Under simulated solar light irradiation, the influences of Gd3+doping on photocatalytic activity of Bi2MoO6 were evaluated by photocatalytic degradation of Rhodamine B. The characterization results showed that with Gd3+ doping, a contraction of lattice and a decrease in crystallite size occurred. Meanwhile, an increase in surface area over Gd3+ doped Bi2MoO6 was observed. Moreover, Gd3+ doping could obviously enhance the visible light harvesting of Bi2MoO6 and promoted the separation of photogenerated electrons and holes. With optimum Gd3+(6 wt%) doping, Gd/Bi2MoO6 exhibited the best activity and stability in degradation of Rhodamine B.

In3+, Gd3+ were selected as substitution elements for Ce4+ in order to increase electrical conductivity and chemical stability of BaCeO3. A modified sol-gel method was used to fabricate BaCe0.7In0.3-xGdxO3-δ (x = 0, 0.1, 0.2, 0.3) nanopowders. XRD results indicated that the diffraction angle moved to lower with increase of the Gd3 + doping concentration, so that the interplanar spacing gradually increased. The impedance spectra analysis showed that conductivity first increased (x = 0~0.2) and then decreased with the Gd3 + doping increase. The total conductivities at 800oC were 3.8 × 10-3 S·cm-1 (x = 0), 8.0 × 10-3 S· cm-1 (x = 0.1), 2.5 × 10-2 S· cm-1 (x = 0.2), 1.36 × 10-2 S ·cm-1 (x = 0.3). Chemical stability test in CO2 show that all samples except for x=0.3 sample calcination at 800oC for 2h under 100% CO2 and x=0, 0.1 samples heating in boiling water for 12h kept main perovskite structure. Therefore, x=0.1 sample show better electrical conductivity and chemical stability.

Pure Bi4Si3O12(BSO) and Bi4Si3O12:Gd (BSO:Gd) crystals with nominal concentrate of 1.0–6.0 mol% Gd2O3 were grown by the modified vertical Bridgman method. The X-ray powder diffraction, transmission and fluorescence spectra have been investigated on BSO:Gd crystals. Scintillation properties of Gd3+ doped Bi4Si3O12 single crystals have been investigated. Doped with small amount of Gd2O3(1.0–6.0 mol%), the relative light yield and energy resolution of BSO crystals were improved significantly. The experimental data indicates that the sensitization effect of a small amount of Gd3+ doping enables the intrinsic defects reduce, and improve the light yield and a large amount of Gd3+ doping can cause the new crystal field distortion and further affect the intrinsic luminescence of Bi3+. These results indicate that BSO:Gd crystals could be one of the promising candidates for replacing BGO in some applications such as electromagnetic calorimeter and dual readout in nuclear or high energy physics.

A series of Gd3+ dopings in zirconia-toughened alumina (ZTA) systems were undertaken to explore the resultant structural, morphological, hydrothermal aging, and mechanical behavior and imaging contrast abilities. The results from the characterization techniques demonstrate the significance of Gd3+ in preserving the structural stability of ZTA systems. ZTA undergoes phase degradation with 10 wt % Gd3+ at 1400 °C, while the 100 wt % Gd3+ yields GdAlO3 even at 1200 °C. Gd3+ doping at the intermediate level preserves the structural stability of ZTA systems until 1400 °C. Gd3+ occupies the ZrO2 lattice, and its gradual accumulation induces tetragonal ZrO2 (t-ZrO2) to cubic ZrO2 (c-ZrO2) phase transition. α-Al2O3 crystallizes at 1200 °C and remains unperturbed except for its reaction with the free Gd3+ ions to yield GdAlO3. Aging studies and mechanical tests signify the impeccable role of Gd3+ in ZTA systems to resist phase degradation. Further, the imaging contrast ability of ZTA systems due to Gd3+ doping is ...

Ba1-xGdxTiO3+δ, at x = 0, 0.05, 0.1, 0.15, 0.2, (BGT) thin films have been fabricated on SiO2/Si substrate using Sol-Gel method. The microstructure and surface morphology of the fabricated films have been investigated using X-ray diffraction (XRD) and atomic force microscopy (AFM). The XRD results show that the fabricated films are crystalline with perovskite structure. There is a shifting of the preferred peak at 31.5o to a higher angle as the doping ratio increases suggesting a distortion lattice exists in the films, which could be due to the substitution of Gd3+ ions into Ba-site. The decreasing of lattice constants confirms the substitution of Gd3+ in BaTiO3 lattice structure. The microstrain and dislocation density are found to be increased with the increase of Gd3+ doping, which attributed to the reduction of lattice volume that due to the ionic size mismatch effect. The AFM results show decreasing trend in both average grain size and roughness parameters. Therefore, the microstructure and surface morphology of BGT samples is strongly dependent on the Gd3+ doping concentration that mainly due to the difference ionic radius substitution.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.13954

Traditional ferrites are of poor electromagnetic wave (EMW) absorption while doping rare earth elements (REEs) can greatly enhance their permeability to improve the EMW loss performance. In this study, Co-Zn ferrite nanoparticles doped with various amounts of REEs (Gd3+, Nd3+ and Pr3+) were synthesized by a hydrothermal method, and their particle morphology and an EMW absorption performance were characterized by using transmission electron microscopy (TEM) and a Vector network analyzer (VNA). The results show that the initial spherical Co-Zn ferrite nanoparticles present an irregular quadrilateral structure after Gd3+ doping, and the average particle size of Co0.5Zn0.5−xGdxFe2O4 increases from 26 to 50 nm with x increasing from 0 to 0.35. At x of 0.25, the reflectivity absorbance achieves −27.94 dB at 18 GHz with the effective absorption bandwidth (EAB) of 4.08 GHz at a sample thickness of 2.5 mm. When Nd3+ doping amount reaches x = 0.3, the minimum reflection loss (RL) is −25.63 dB at 18 GHz and EAB is 3.91 GHz. Doping Pr3+ (x = 0.25) in the sample broadens EAB, and the minimum RL is −16.1 dB at 16.81 GHz and EAB is 7.31 GHz. This study shows that the magnetic moment produced by doping REES can form magnetic domains, which affects the incident EMW and improves the magnetic loss. It is expected that REEs-doped Co-Zn ferrite nanoparticles can be used as efficient electromagnetic shielding materials in aerospace.

The upconversion emission tuning with size decrease has been achieved through Y3+ or Gd3+ ions doping in lanthanide-doped NaYbF4 nanoparticles prepared by a chemical coprecipitation method. With an increase of the Y3+ or Gd3+ doping concentrations (0−40 mol%), the nanoparticle size is continuously decreased from 250 nm down to 15.8 nm without phase transformation. Compared with Y3+ doping, the particle size decreases more rapidly via Gd3+ doping. Meanwhile, the intensity ratio of red emission to green emission in NaYbF4:2%Er3+ nanoparticles decreases monotonically with increasing Y3+ or Gd3+ doping concentrations, thus producing tunable upconversion emissions. For NaYbF4:2%Tm3+ nanoparticles, the luminescence intensity of the near-infrared upconversion emission at 800 nm was largely enhanced by about 36- and 17-fold for doping of 40 mol% Y3+ and 20 mol% Gd3+, respectively. These results offer an effective strategy to simultaneous control of the size and luminescence properties of lanthanide-doped upconversion nanoparticles.

Gd doped La0.8Sr0.2MnO3 (La0.8-xGdxSr0.2MnO3, LGSMO) ceramics were prepared by a sol-gel method. X-ray diffraction (XRD) patterns showed that all samples exhibited distorted perovskite structures, R3c. When the Gd3+ content x > 0.03, the crystal structure changed to orthorhombic, Pnma. Scanning electron microscopy (SEM) images showed that the ceramics characterize high density and grain boundary connectivity, and higher Gd3+ doping decreased the grain size from 26.72 μm to 7.42 μm. The temperature dependence of resistivity showed a transition from a low-temperature metal to a high-temperature insulator. The resistivity increased with Gd doping content, and the metal-insulator transition temperature, TP, increased first and then decreased, while the temperature coefficient of resistance (TCR) of the samples first decreased and then increased with Gd3+, and the magnetoresistance (MR) increased first and then decreased. The peak TCR at x = 0.06 was 5.18%·K−1, and MR at 0.04 was 34.57%. The electrical transport properties of the ceramics were explained based on the double exchange (DE) interaction mechanism. The obtained material may have application prospects in magnetic devices and infrared detectors.

β-NaYF4:Eu3+ microparticles co-doped with Gd3+ ions were obtained by hydrothermal synthesis at 180 °C using citric acid as a stabilizing agent. All synthesized materials have a β-NaYF4 crystalline phase, where the unit cell volume increases upon the addition of Eu3+ and Gd3+ ions. The particles have a hexagonal prism shape and a size of 40–714 nm, where Eu3+ and Gd3+ doping results in size reduction. Upon 393 nm excitation, phosphors exhibit distinct emission peaks centered at 591, 615, and 695 nm and a weak band at 650 nm attributed to 5D0–7FJ transitions (J = 1–4). The optimum Eu3+ doping concentration was found to be 30% in the NaYF4 host. Concentration quenching was realized through dipole–dipole interactions. Kinetic measurements showed a gradual decline of the 5D0 lifetime from 6.7 ms to 2.2 ms along with an increase in Eu3+ doping concentration. Co-doping of the small Gd3+ number led to an increase of emission intensity and 5D0 lifetime. The effects of Eu3+ doping and Gd3+ co-doping on radiative and nonradiative decay rates were studied using 4f–4f intensity theory.

Micro-size and nano-size samples of (GdxY3−xFe5O12; x = 0, 0.25, 0.5, 0.75, and 1) garnet ferrites were prepared by the standard ceramic method (CER) and the coprecipitation (COP) method. The influences of Gd3+ doping and preparation methods on the optical and dielectric properties were compared for these micro-size and nano-size compositions for the first time. X-ray diffraction data confirmed the formation of a single phase of the garnet cubic structure for all samples. It was found that there is a good agreement between the theoretical and experimental lattice parameter estimated values. The Fourier transform infrared spectroscopy was used to study the cation distributions among the different crystallographic sites. Moreover, values of energy gap (Eg) for the investigated samples were determined from the diffused reflectance spectroscopy measurements. These values were found to be higher for (COP) samples than for (CER) ones and slightly increased by increasing Gd3+ content in both series prepared via the two techniques. Furthermore, resistivity (ρac), dielectric constant (e′), and dielectric loss (e″) showed a decrease with increasing frequency (f) for all samples. For the samples prepared by (CER) method, ρac increases with increasing Gd3+ content while for the samples prepared by (COP) method, ρac increases for 0 ≤ x ≤ 1 except for the sample x = 0.5. Values of ρac for samples prepared by (COP) method are higher than those prepared by (CER) method. Both e′ and e″ had the reverse behavior of ρac. Obtained results were explained according to different models.

Tuning of phosphor luminescence properties, including the emission energy/intensity and thermal stability, is an important way to develop superior luminescent materials for diverse applications. In this work, we discuss the effect of band gap engineering and energy transfer on the luminescence properties of Ce3+ or Pr3+ doped (Y,Gd)AGG systems, and analyze the underlying reasons for their different phenomena. By using VUV-UV excitation spectra and constructing VRBE schemes, the changes of host band structure, 5d excited level energies and emission thermal stability of Ce3+ and Pr3+ with the incorporation of Gd3+ ions were studied. In addition, the energy transfer dynamics was also investigated in terms of the luminescence decay curves. This work demonstrates a way to tune phosphor luminescence properties by combining band gap engineering and energy transfer tailoring and provides an inspiring discussion on the different results of Gd3+ doping on the Ce3+ and Pr3+ emissions.

The promise of hyperpolarized glucose as a non-radioactive imaging agent capable of reporting on multiple metabolic routes has led to recent advances in its dissolution-DNP (dDNP) driven polarization using UV-light induced radicals and trityl radicals at high field (6.7 T) and 1.1 K. However, most preclinical dDNP polarizers operate at the field of 3.35 T and 1.4-1.5 K. Minute amounts of Gd3+ complexes have shown large improvements in solid-state polarization, which can be translated to improved hyperpolarization in solution. However, this Gd3+ effect seems to depend on magnetic field strength, metal ion concentration, and sample formulation. The effect of varying Gd3+ concentrations at 3.35 T has been described for 13 C-labeled pyruvic acid and acetate. However, it has not been studied for other compounds at this field. The results presented here suggest that Gd3+ doping can lead to various concentration and temperature dependent effects on the polarization of [13 C6 ,2 H7 ]glucose, not necessarily similar to the effects observed in pyruvic acid or acetate in size or direction. The maximal polarization for [13 C6 ,2 H7 ]glucose appears to be at a Gd3+ concentration of 2 mM, when irradiating for more than 2 h at the negative maximum of the DNP intensity profile. Surprisingly, for shorter irradiation times, higher polarization levels were determined at 1.50 K compared to 1.45 K, at a [Gd3+ ]=1.3 mM. This was explained by the build-up time constant and maximum at these temperatures.

Yttrium Aluminum Garnet transparent ceramics with different Gd3+ concentrations ((Ce0.001GdxY0.999-x)3Al5O12) ceramics were prepared by the conventional solid state reaction technology and vacuum sintering method, and the ceramic-based LEDs with blue LED were prepared by flip chips and Chip on board package. The extreme circumstance of −40 °C and 150 °C alternate environments, high humidity and high temperature as well as xenon lamp aging test for a long time are mentioned to explore the reliability of phosphor ceramics, respectively. And the thermostability and the effect of Gd3+ doping on the PL properties of ceramics were also investigated. What is more, the effects on the optical performance of the ceramic-based LEDs have been also investigated. As Gd3+ concentration added from 0 to 0.5, the PL spectra peaks of phosphor shifted from 542 nm to 575 nm under the excitation of 460 nm. It can be summarized that the increase of Gd3+ concentration could not improve the thermostability, but enhance the reliability when the x value is x is not greater than 0.4. What is more, the ceramics-based LED of x = 0.3 instead of x = 0.4 has the best reliability after the xenon lamp aging and thermal cycling test. And the ceramics-based LED of x = 0.45 has the best reliability after the high humidity and high temperature test. Compared with Ce:YAG and Ce:LuAG ceramics, although the increase of Gd3+ concentration decreases the thermostability and luminous efficiency, the Gd substitution can enhance the reliability and solve the lack of red light in the spectrum of Ce:YAG and Ce:LuAG ceramics, which has improved the performance of Ce:GdYAG ceramics for high-power warm white LEDs.

MgAl2O4:x% Gd3+ (0 ≤ x ≤ 3) nano-powders were prepared via the citrate sol–gel method. The x-ray diffraction confirmed that the prepared samples consist of the cubic crystalline structures. There was no secondary phases due to Gd3+ doping. The estimated average grain sizes were found to be in the order of 8 nm. Energy dispersive spectroscopy showed the presence of the anticipated elements (Mg, Al, O, and Gd). The scanning electron microscope results revealed that the morphology of the samples is influenced by the Gd3+ concentration. Transmission electron microscopy analysis revealed that the prepared samples are in the nano-scale range. Selected area electron diffraction patterns indicated highly crystalline structure and the intensities of the bright spots varied with Gd3+ concentration. Photoluminescence studies showed two distinct emission peaks at 385 and 392 nm, which are certainly attributed to the defects levels located at different positions on the host material (MgAl2O4). The emission peaks located at 315 and 628 nm were respectively attributed to the 6P7/2 → 8S7/2 and 6G7/2 → 6P3/2 transitions in the Gd3+ ion. The luminescence intensity of the 388 nm decreased with an increase in the Gd3+ concentration. Commission Internationale de l’Eclairage (CIE) coordinates showed that the violet emission color from host cannot be tuned by varying Gd3+ concentration.

Graphene quantum dots (GQDs) are unique derivatives of graphene that show promise in multiple biomedical applications as biosensors, bioimaging agents, and drug/gene delivery vehicles. Their ease in functionalization, biocompatibility, and intrinsic fluorescence enable those modalities. However, GQDs lack deep tissue magnetic resonance imaging (MRI) capabilities desirable for diagnostics. Considering that the drawbacks of MRI contrast agent toxicity are still poorly addressed, we develop novel Mn2+ or Gd3+ doped nitrogen-containing graphene quantum dots (NGQDs) to equip the GQDs with MRI capabilities and at the same time render contrast agents biocompatible. Water-soluble biocompatible Mn-NGQDs and Gd-NGQDs synthesized via single-step microwave-assisted scalable hydrothermal reaction enable dual MRI and fluorescence modalities. These quasi-spherical 3.9-6.6 nm average-sized structures possess highly crystalline graphitic lattice structure with 0.24 and 0.53 atomic % for Mn2+ and Gd3+ doping. This structure ensures high in vitro biocompatibility of up to 1.3 mg ml-1 and 1.5 mg ml-1 for Mn-NGQDs and Gd-NGQDs, respectively, and effective internalization in HEK-293 cells traced by intrinsic NGQD fluorescence. As MRI contrast agents with considerably low Gd and Mn content, Mn-NGQDs exhibit substantial transverse/longitudinal relaxivity (r 2/r 1) ratios of 11.190, showing potential as dual-mode longitudinal or transverse relaxation time (T 1 or T 2) contrast agents, while Gd-NGQDs possess r 2/r 1 of 1.148 with high r 1 of 9.546 mM-1 s-1 compared to commercial contrast agents, suggesting their potential as T1 contrast agents. Compared to other nanoplatforms, these novel Mn2+ and Gd3+ doped NGQDs not only provide scalable biocompatible alternatives as T1/T2 and T1 contrast agents but also enable in vitro intrinsic fluorescence imaging.

Taking advantage of the superior biocompatibility, good stability in a wide pH and temperature range, as well as its strong affinity with DNA of hydroxyapatite (HAp), tetrahedral DNA nanostructures (TDNs) conjugated with AS1411 aptamer (anti-nucleolin overexpressed on tumor cell membranes) were employed as affinity ligands to construct a novel mono-dispersed HAp based probe with Gd3+ doping (Apt-TDNs-GdHAp) for MR imaging. The adsorption of TDNs on the nano-HAp surface facilely accomplished the construction of the Apt-TDNs-GdHAp probes. Meanwhile, the use of hydrophilic TDNs not only favored the phase-transfer from the oil phase to the aqueous phase, but also enhanced the mono-dispersion of this probe due to the well-ordered distribution of TDNs on the surface of nano-HAp. Moreover, Apt-TDNs-GdHAp probe with a better mono-dispersion and crystalinity achieved twice higher longitudinal relaxivity (r1 value) than that of GdHAp synthesized by microwave-assisted method (Microwave-GdHAp), exhibiting much more excellent T1-weighted imaging performance. With the introduction of TDNs, the stability and the tumor-targeting accessibility were also greatly improved, showing its great potential for further bio-applications.

Lanthanide doping is an effective and controllable approach for optimizing the oxidation ability, light absorption and charge separation of photocatalysts. However, the multiple drawbacks of mono-component photocatalysts have not been adequately resolved by the doping of only one or two lanthanide ions. Herein, a novel Gd/Er/Lu-triple-doped Bi2MoO6 photocatalyst was synthesized using a hydrothermal method. The results of trapping and 4-Chlorophenol degradation experiments suggested that the oxidizing efficiency of Bi2MoO6 was clearly enhanced by the generation of hydroxyl radicals after doping with the Gd3+ redox centers. The obtained diffuse reflectance spectra demonstrated that introducing Er3+ ions provides energy upconversion centers to improve light absorption. The obtained X-ray photoelectron and photoluminescence spectra demonstrated that abundant oxygen vacancies were produced in the Bi2MoO6 crystal after the doping of Lu3+ ions, contributing to promoting the separation of charge carriers. In summary, Gd/Er/Lu-triple-doped Bi2MoO6 displays much better photocatalytic performance than single- and double-doped Bi2MoO6 materials, which is attributed to the synergistic effects of the Gd3+, Er3+ and Lu3+ ions. These discoveries demonstrate a novel synergistic effect of the redox centers (Gd3+ doping), energy upconversion (Er3+ doping) and oxygen vacancies (Lu3+ doping) for the design and fabrication of high-efficiency photocatalysts.

Nanocrystalline powders of Gadolinium (Gd3+) substituted nickel ferrite spinel (NiGdxFe2−xO4: x = 0.00, 0.025, 0.050, 0.075 and 0.1) samples were synthesized via sol-gel method. Nickel nitrate hexahydrate and Ferric nitrate hexahydrate were used as the precursors and rare earth Gadolinium nitrate hexahydrate [Gd(NO3)3·6H2O] was used as the dopant. The structural, morphological, magnetic and dielectric properties of the synthesized nanoparticles were examined by XRD, FTIR, HRSEM, EDX, TEM, VSM and dielectric studies. The Scherrer method and Williamson-Hall (W-H) method were used to evaluate the crystallite sizes and lattice strain. The crystallite size of NiGdxFe2−xO4 samples were found to decrease from 25 nm to 11 nm with increase in Gd3+ content. Lattice parameters decrease and lattice strain increases with the increase in Gd3+ content in the sample. HRSEM images showed the spherical morphology and uniform size distribution. The elemental composition analysis confirms the stoichiometric presence of expected elements in the samples. The crystallite size and the particle size calculated from the XRD analysis and HRTEM monographs indicate the correlation of the data obtained from both the measurements. Magnetic studies of the samples were performed using vibrating Sample Magnetometer, in which magnetizations (Ms) decrease with increase in Gd3+ concentration from 36.51 emu/gm to 19.69 emu/gm. As the gadolinium content was gradually increased, coercivity and remnant magnetization were also decreased. Magnetic anisotropy of nickel ferrite was also found to decrease with increasing gadolinium content. The saturation magnetization values were achieved by using the “Law of Approach (LA) to Saturation magnetization” technique. Specific correlation between magnetic interaction and lattice strain was observed in Gd3+ substituted nickel ferrite. Dielectric parameters such as dielectric constant and dielectric loss of the prepared samples decrease with increase of applied frequency and increasing of Gd3+ doping concentration.

NiGdxFe2-xO4 nanoparticles with x = 0.0, 0.03, 0.05, 0.07, and 0.10 were synthesized by co-precipitation method and effect of Gd3+ substitution on various properties of nanocrystalline NiFe2O4 has been studied. Formation of single phase cubic mixed spinel structure is confirmed by X-ray diffraction and Raman spectroscopy and cations distribution has also been proposed from Rietveld refined data. Room temperature Mossbauer spectra showed two ferrimagnetic Zeeman sextets with one superparamagnetic doublet. Octahedral site occupancy of Gd3+ ions in these nanoparticles is suggested by Mossbauer parameters. Within the framework of X-ray photoelectron spectroscopy analysis, the ratio of cation concentration at tetrahedral and octahedral sites has been found to be consistent with proposed cation distribution. Magnetic measurements at room temperature exhibit the reduction in the saturation magnetization from 36 emu/gm to 4.9 emu/gm for x = 0.0 to 0.10 samples. The discrepancy in measured and calculated magnetic moment may be ascribed to the nonzero Yafet–Kittel angles of B site spins, which weaken A–B interaction. The coercivity decreases from 121 Oe to 48 Oe for x = 0.0 to 0.07 samples and again increases to 153 Oe for x = 0.10 sample. The degree of inversion calculated by Raman analysis varies with Gd3+ concentration which is supported by the variation of coercivity. The calculated spin numbers from electron spin resonance spectra decreases with Gd3+ doping which confirms the reduction in magnetization. Both dielectric constant and dielectric loss are found to decrease with the Gd3+ substitution because of the reduced hopping rate for Fe3+ at the octahedral sites in doped nanoparticles. Lower values of dielectric loss suggest that Gd3+ doped NiFe2O4 nanoparticles are suitable for high frequency microwave device applications.

A series of Bi2O3:Yb3+/Er3+ phosphors with different phases and morphologies were obtained by tuning doping ions, which played a vital role in the upconversion luminescence (UCL). Both Er3+ single doped and Yb3+/Er3+ co-doped samples exhibit narrow, nearly pure red emission whether excited by 980 nm or 1550 nm. Compared to the sum of emission intensities excited by two single-wavelength (980 nm and 1550 nm) separately, the red emission from Bi2O3:Yb3+/Er3+ with uneven distributed nanometer or micron blocky particles structure excited by two-wavelength simultaneously was enhanced by a factor of 2.41. To further improve the UCL intensity, optical-inert ions such as Na+, Ca2+ and Gd3+ were doped into this system. Compared to the optical-inert ions free sample (Bi2O3:15% Yb3+, 2% Er3+), the pure red UCL in Bi2O3:15% Yb3+, 2% Er3+ with 6% Na+, 2% Ca2+ and 4% Gd3+ doping is enhanced by 223.83 or 203.73 times under 980 or 1550 nm excitation, respectively. Meanwhile, the UCL mechanism under the multiwavelength was investigated in detail and its model of UC emission process was proposed.

Upconversion nanoparticles (UCNPs) possess a unique type of photoluminescence (PL) in which lower-energy excitation is converted into higher-energy emission via multi-photon absorption processes. In this work, we have used a facile one-step hydrothermal method promoted water solubility to synthesis NaLuGdF4:Yb3 +/Er3 +(Tm3 +) UCNPs coated with malonic acid (MA). Scanning electron microscopy images and X-ray diffraction patterns reveal sphere-shaped UCNPs with an average size of ~ 80 nm crystallized in the cubic NaLuF4 structure. The characteristic vibrations of cubic UCNPs have been taken into account by using Fourier-transform infrared spectroscopy. Based on PL studies, we have determined an optimal concentration of Gd3 + doping. The dependence of upconversion PL intensity on Gd3 + concentration is discussed via the results of magnetization measurements, which is related to the coupling/uncoupling of Gd3 + ions. Particularly, our study reveals that carboxyl-functionalized NaLuGdF4:Yb3 +/Er3 +(Tm3 +) UCNPs have a relatively high cell viability with HeLa cells.

In this paper, (Lu1-xGdx)2O3:Eu (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9) ceramics were consolidated by the solid-state reaction method combined with vacuum sintering without sintering aids. We investigated the effect of the varying contents of Gd2O3 on the structure and spectroscopic properties of (Lu1-xGdx)2O3:Eu ceramics. X-ray diffraction (XRD) patterns indicate that proper amount of Gd2O3 can incorporate well with Lu2O3 and form Lu2O3-Gd2O3 solid solution. However, excessive Gd3+-doping in Lu2O3 will lead to the cubic phase transforming into monoclinic even hexagonal phase. The Gd3+ substitution no more than 50% of Lu2O3 enhances the radioluminescence, and reduces the fluorescence lifetime. Transmittance, photoluminescence, and radiation damage of the (Lu1-xGdx)2O3:Eu scintillation ceramics were also studied.

Herein, user-friendly control of the synthesis of sub-10 nm hexagonal (β-) NaYbF4:Er nanocrystals (NCs) with extremely low-level Gd3+ doping (0%, 10 mol%) was achieved. We reveal for the first time that the effective sodium/fluoride levels during the formation of cubic (α-) nuclei are not only controlled by the sodium/fluoride to rare-earth precursor ratios used, but also sensitively restricted by the in situ NaF generation reaction in a sodium oleate-based solvothermal system. Excessive in situ NaF generation will lead to a respective sodium- and fluoride-deficient environment, delayed α-to-β transition and larger β-NCs. Based on these effects, sub-10 nm monodisperse low-level Gd3+-doped β-NaYbF4:Er was obtained with a user-friendly low fluoride dosage by finely balancing this NaF generation reaction and achieving an intrinsic optimized sodium-fluoride level for NC nucleation. Notably, our work represents the first example where the focus is on the competing in situ NaF generation reaction and its use for nucleation regulation, as well as for the user-friendly control of the solvothermal synthesis of sub-10 nm β-NaYbF4:Er.

Rare earth (RE) ions are known to improve the magnetic interactions in spinel ferrites if they are accommodated in the lattice, whereas the formation of a secondary phase leads to the degradation of the magnetic properties of materials. Therefore, it is necessary to solubilize the RE ions in a spinel lattice to get the most benefit. In this context, this work describes the synthesis of Co–Zn ferrite nanoparticles and the Gd3+ doping effect on the tuning of their magnetic properties. The modified sol–gel synthesis approach offered a facile way to synthesize ferrite nanoparticles using water as the solvent. X-ray diffraction with Rietveld refinement confirmed that both pure Co–Zn ferrite and Gd3+ substituted Co–Zn ferrite maintained single-phase cubic spinel structures. Energy dispersive spectroscopy was used to determine the elemental compositions of the nanoparticles. Field and temperature dependent magnetic characteristics were measured by employing a vibration sample magnetometer in field cooled (FC)/zero field cooled (ZFC) modes. Magnetic interactions were also determined by Mossbauer spectroscopy. The saturation magnetization and coercivity of Co–Zn ferrite were improved with the Gd3+ substitution due to the Gd3+ (4f7)–Fe3+ (3d5) interactions. The increase in magnetization and coercivity makes these Gd3+ substituted materials applicable for use in magnetic recording media and permanent magnets.

The optical nano-thermometers with near-infrared-II (NIR-II) luminescence (1000 ∼ 1700 nm) have drawn growing interest owing to the unique merits such as deep-tissue penetration and excellent spatial resolution. Herein, we report a simple way to improve the NIR-II luminescence and temperature sensing sensitivity simultaneously in Er3+/Yb3+: ZrO2 nanocrystals with the introduction of Gd3+ ions. X-ray diffraction and transmission electron microscopy measurements validate that the addition of Gd3+ ions can change the host lattice parameter and decrease the crystalline grain size of the samples. The optical investigation shows that the remarkable enhancements in the NIR-II emissions of Yb3+ (1036 nm) and Er3+ (1527 nm) are realized via Gd3+ doping under 980 nm excitation, which can be interpreted based on the accelerated radiative transition rate and non-radiative Yb3+-Er3+ energy transfer rate. Meanwhile, the thermal sensing sensitivity of the samples shows a strong dependence on the Gd3+ concentrations, when the fluorescence intensity ratio between Yb3+: 2 F 5 ∕ 2 → 2 F 7 ∕ 2 and Er3+: 4I 13 ∕ 2 → 4I 15 ∕ 2 transitions is chosen for temperature sensing. Both the optimal NIR-II luminescence and thermal sensitivity are achieved in 1 mol%Gd3+ co-doped sample. The proposed route here may help in the development of efficient NIR-II luminescence materials for thermometry in the biological and medical fields.

CeO2 films with mixed doping of gadolinium and zirconium were deposited on NiW substrates by chemical solution deposition. The influences of mixed doping on the epitaxial growth and microstructure of films were systematically investigated. The morphological evolution of films with different dwell times was also discussed. The phase formation, texture and surface morphology of (Ce0.8Gd0.2)1-xZrxO2-δ (CGZO) films were characterized by X-ray diffraction and atomic force microscopy. It was noticed that Zr4+ doping had stronger effect on the crystal structure of CeO2 than Gd3+ doping. The increasing doping content of Zr4+ could be favorable for the self-limited grain growth of the CGZO films and promote the lattice match with substrate. Moreover, the sharp texture and smooth surface of CGZO film could be easily acquired by the mixed doping. The results indicated that the (Ce0.8Gd0.2)1-xZrxO2-δ film was beneficial for the subsequent film growth, which could be a candidate buffer layer for the coated conductors.

Gd doped TiO2 nanoparticles with different dopant concentration were prepared by sol-gel method. The crystalline structure of all samples corresponds to the tetragonal anatase phase. Gd3+ doping inhibit the grain size and increase the micro-strains. The decrease of the nanoparticles size by doping was evidenced by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Specific bands of brookite phase appear in Raman spectra. Electron Spin Resonance (ESR) spectroscopy and high resolution transmission electron microscopy (HRTEM) proved the presence of Gd3+ ions substitutionally incorporated at Ti4+ sites of TiO2 lattice. All the samples show photocatalytic activity against RhB and the best performance was obtained using 0.3% Gd-doped TiO2 nanoparticles. The presence of hydroxyl radical at the solid–liquid interface was evidenced using ESR experiment coupled with spin-trapping technique and their influence on photocatalytic activity of the samples was highlighted. With increasing Gd doping level a little increase of the optical band gap was determined.

In this article, we have synthesized the Gd3+-doped Ni0.5Zn0.5Fe2−x Gd x O4 (x = 0.05, 0.07, 1.0) ferrite samples using solid-state reaction route. The effects of Gd3+ doping on structural, vibrational, electrical and magnetic properties were studied. Structural and vibrational properties were characterized by x-ray diffraction (XRD), Raman, and FTIR spectroscopy. XRD data indicate that the Ni0.5Zn0.5Fe2−x Gd x O4 ceramics crystallize in single-phase spinel cubic (Fd3m space group) structure. Infrared spectra show two strong absorption bands in the frequency range of 400–600 cm−1 which were, respectively, attributed to tetrahedral and octahedral sites of the spinel ferrite. All the prepared samples show the typical dielectric dispersion having Maxwell–Wagner-type interfacial polarization. Decrease in dielectric constant and loss tangent has been observed with frequency and doping concentration. M − H plots reveal that all the samples exhibit ferrimagnetic nature at room temperature. A significant increase in the saturation magnetization has been observed upon the substitution of Gd3+ ions. All the as-prepared samples are isotropic and soft magnetic materials. These ferrite compounds are advantageous in advanced high-density data storage and high-frequency devices applications.

NaYF4:Yb,Er nanocrystals with different structures and sizes have been synthesized via a hydrothermal method. Structures and sizes of the NaYF4:Yb,Er nanocrystals are carefully investigated by changing the Gd3+ ion concentrations and reaction temperatures. It is found that the change of Gd3+ doping concentration and reaction temperature not only induces the phase transition but also causes the size difference. The introduction of Gd3+ ions can promote the phase change from cubic to hexagonal structures, which exhibit the different morphologies (nanoparticle vs nanorods). However, by increasing the reaction temperature slightly, the hexagonal structures can be formed with very low or even without any Gd3+ ions. It is shown that the enhanced up-conversion emission can be achieved by well controlling the Gd3+ ion concentrations at the certain reaction temperature to get the pure nanorods structures with suitable sizes.

ZrO2 samples with variable Gd3+ doping have been prepared by combustion synthesis method followed by annealing at 900 °C. The samples have been characterized by X-ray absorption, Scanning electron microscopy, and electron dispersive X-ray spectroscopy. The optical behaviour was also determined by recording excitation and emission spectroscopy of the phosphor. The emission spectrum contains intense peak at UV region along with peaks at visible region. All the peaks were obtained due to transitions between the energy levels of the Gd3+ ion.