Gadolinium Tungstate Research Articles

Adjustable Emission Color by Gadolinium Tungstate Phosphor for Multiple Applications

Crystalline monoclinic structure Gd2(WO4)3 phosphors were prepared by calcining a co-precipitated precursor at 800°C. The XRD patterns exhibited strong signals at the (-221) and (023) planes. The UV-vis absorption spectrum showed strong absorbance in the UV range, with an estimated bandgap energy of about 4 eV. When excited the synthesized phosphors emitted green (Tb3+), red (Eu3+), yellow (Dy3+), and reddish orange (Sm3+), respectively. Utilizing these luminescent properties, flexible composite sheets were fabricated by mixing the phosphors with PDMS. When applied to UV-LED chips. The composites could be molded into various shapes figures. Under normal light, the composites appeared white, but under UV light, they displayed distinct colors, demonstrating their potential for anti-counterfeiting applications. Additionally, when the synthesized phosphor powder was sprinkled onto a glass substrate with fingerprints and illuminated with a UV lamp, the unique features of the fingerprints were clearly visible, indicating potential use in forensic fingerprint analysis.

Synthesis and Thermoluminescence Characterization of Ba₆Y₂W₃O₁₈ Perovskite Nanosensors for Dosimetry

Through the citrate-assisted sol-gel method, barium gadolinium tungstate (Ba6Y2W3O18) perovskite samples were synthesized, and their luminescence properties were investigated. Through X-ray diffraction (XRD) the crystal structure of the prepared samples was examined. The tunnelling electron microscopy (TEM) analysis has confirmed the agglomeration of the nanoparticles into rods with an average diameter and length of 71 and 214 nm, respectively. The thermoluminescence (TL) properties were investigated by; first, estimating the number of composing TL components using both experimental and computational methods; second, studying the dose-response of the glow curves in response to the irradiated beta dose. The third step in the study of the TL properties was to assess the reusability of the prepared samples in TL dosimetry and the fourth step was to estimate the minimum detectable dose of the phosphor samples. The Computerized Glow Curve Deconvolution (CGCD) method was then used to extract the kinetic parameters of the composing TL peaks.

Multi-walled carbon nanotube wrapped rare earth tungstate nanosheet composites for selective and rapid detection of sulfadiazine

Multi-walled carbon nanotube wrapped rare earth tungstate nanosheet composites are developed for the ultrasensitive and selective electrochemical detection of sulfa drug, sulfadiazine (SAN) as they exhibit high levels of toxicity towards public health and ecosystem. Here, we synthesized Gadolinium tungstate decorated with multi-walled carbon nanotubes (Gd2WO6/MWCNT) though hydrothermal processing and characterized by XRD, SEM, EDX, TEM, and EIS measurement to investigate the phase purity, morphology, and interfacial property. Gd2WO6 is a double perovskite that has high oxygen surface exchange kinetics and the MWCNT possesses high catalytic capability and a larger surface area contributes to the efficient sensing ability. The Gd2WO6/MWCNT possessed a great electrical conductivity owing to the synergism between the Gd2WO6 and MWCNT. The synergistic effect increases the surface area, ionic and electrical conductivity which increases the current response of SAN. Under optimum conditions, the Gd2WO6/MWCNT/GCE displays a broad linear of 0.01 – 671 µM and a LOD level of 2 nM (S/N ratio: 3) with a sensitivity of 0.371 µA µM cm−1. The analytical applicability of the proposed electrode modifier leads to a promising sensor for SAN detection in human urine and water samples with appreciable results.

Highly efficient continuous-wave solid-state Raman crystal lasers at 555 and 559 nm

High-power efficient continuous-wave Nd:YVO4/KGW Raman lasers at 555 and 559 nm are achieved by using a double-sided dichroic coating output coupler to improve the resonance quality factor. The Np-cut potassium gadolinium tungstate (KGW) is used to generate the Stokes waves at 1159 and 1177 nm by placing the polarization of the1064 nm fundamental wave parallel to the Ng and Nm axes, respectively. The lithium triborate (LBO) crystal with the cut angle in the XY plane for the type-I phase matching is used to perform the intracavity sum frequency generation for yielding the green light at 555 nm and the lime light at 559 nm at the optimal phase matching temperature. Experimental results were systematically accomplished to comprehend the optimal cavity length for the conversion efficiency. Under the optimal cavity length, the output powers can reach 6.6 and 6.3 W at a pump power of 22 W for the wavelengths of 555 and 559 nm, respectively. The conversion efficiencies can be up to 30% and 28.6% for 555 and 559 nm, respectively.

Features of cluster ion treatment of the surface of KGd(WO<sub>4</sub>)<sub>2</sub>:Nd single crystal

The features of the surface treatment of single crystals of potassium gadolinium tungstate doped with neodymium ions with low- and high-energy cluster argon ions are considered. Two radically different treatment modes were used: low-energy for more efficient surface smoothing and high-energy for more efficient target etching. Using atomic force microscopy, the topography of the target surface was analyzed before and after cluster ion treatment. Treatment in a low-energy mode was shown to smooth out irregularities on the target surface formed by chemical-mechanical polishing at an etching depth of less than 100 nm. The root-mean-square roughness and maximum height difference of the initial and treated surfaces of potassium gadolinium tungstate doped with neodymium ions were compared. Survey X-ray photoelectron spectra of the initial surface of a KGd(WO4)2:Nd single crystal and after the cluster ion treatment in different modes are presented. The intensities of the potassium and gadolinium peaks were shown to decrease after cluster ion treatment in both modes. A significant decrease in the concentration of potassium atoms in the subsurface layer of the target is explained by the predominant sputtering of potassium as a lighter chemical element. The mutual decrease in the concentrations of gadolinium and potassium atoms can be explained by the weak bonds of these atoms in the lattice of the KGd(WO4)2:Nd single crystal.

Impact of Laser Cavity Configurations and Pump Radiation Parameters on the Characteristics of High-Energy Yellow Raman Lasers Based on Potassium Gadolinium Tungstate Crystals

In this paper, the influence of pump radiation parameters and laser resonator configurations on the characteristics of high-energy 589 nm KGW Raman lasers is investigated and explained. The best energy efficiency is obtained in lasers with a flat resonator, while the best angular characteristics are obtained in lasers with an unstable resonator. The use of stable spherical resonators results in the worst energy and angular characteristics. The angular divergence in lasers with flat cavities increases with pump intensity because of wing growth, whereas the core width remains unchanged. The structure of the wings is recorded and analyzed.

Sub-Nanosecond Passively Q-Switched Yellow and Orange Raman Lasers

Sub-nanosecond high-peak-power passively Q-switched yellow and orange lasers are compactly developed using a near-concentric resonator with intracavity-stimulated Raman scattering (SRS) as well as second harmonic generation (SHG). The fundamental wave is generated from an a-cut Nd:YVO4 crystal. The Stokes wave for an SHG yellow (579 nm) or orange (589 nm) laser is generated from a Np-cut potassium gadolinium tungstate (KGW) with the Ng or Nm axis parallel to the c-axis of Nd:YVO4 crystal. The optimal cavity length is systematically explored in a near-concentric configuration to achieve sub-nanosecond high-peak-power pulses. The shortest pulse widths for the yellow and orange output pulses are down to 0.67 ns and 0.70 ns, respectively. The highest peak powers for the yellow and orange output pulses are up to 176 and 138 kW, respectively.

Low-threshold supercontinuum generation in a homogeneous bulk material at 76 MHz pulse repetition rate.

We report on high average power, low threshold supercontinuum generation in a homogeneous bulk material at 76 MHz pulse repetition rate with amplified as well as unamplified pulses from a Yb:KGW oscillator. An octave-spanning supercontinuum was produced in undoped potassium gadolinium tungstate (KGW), which demonstrated robust, damage-free long-term performance with a total average pump power of 6.4 W. The supercontinuum generation was unambiguously attested by the distinctive features of the phenomenon: beam filamentation visualized via filament-induced luminescence; conical emission and its characteristic angular distribution captured by angle-resolved spectral measurements; and pulse splitting that produced the sub-pulses with well-behaved phases, as retrieved from the measurements employing a second harmonic frequency-resolved optical gating technique.

Microstructure and property of gadolinium tungstate ceramic fabricated via pressureless sintering

Gd2WO6 precursor powder was prepared from Gd2O3 and WO3 via a high-temperature solid-state reaction. Gd2WO6 ceramics with relative densities more than 95% were prepared by secondary sintering method. The effects of temperature on Gd2WO6 phase composition, microstructure, and properties of the ceramic materials were studied. The main reaction temperature of Gd2O3 and WO3 is 1050 °C. However, XRD results show that the reaction already occurs below 1050 °C. The prepared precursor powder contains W17O47. After secondary sintering, local segregation was observed by TEM, and two phases of solid solutions were formed. Gd2WO6 and Gd2(WO4)3. W17O47 dissolved into Gd2WO6 to form Gd2(WO4)3. With increasing sintering temperature, the lattice parameters of Gd2WO6 changed, the overall trend became smaller, and the theoretical density gradually increased. FTIR measurements showed that the ceramic has exxellent luminescence properties and is expected to be used in solid-state light emitters.

KGW and YVO4: two excellent nonlinear materials for high repetition rate infrared supercontinuum generation.

We present an experimental investigation of supercontinuum generation in potassium gadolinium tungstate (KGW) and yttrium vanadate (YVO4) crystals pumped with 210 fs, 1030 nm pulses from an amplified Yb:KGW laser operating at 2 MHz repetition rate. We demonstrate that compared to commonly used sapphire and YAG, these materials possess considerably lower supercontinuum generation thresholds, produce remarkable red-shifted spectral broadenings (up to 1700 nm in YVO4 and up to 1900 nm in KGW) and exhibit less bulk heating due to energy deposition during filamentation process. Moreover, durable damage-free performance was observed without any translation of the sample, suggesting that KGW and YVO4 are excellent nonlinear materials for high repetition rate supercontinuum generation in the near and short-wave infrared spectral range.

Synthesis of Adjacent Stokes Spectra in a Two-Stage Transient Stimulated Raman Chirped-Pulse Amplifier

The synthesis of adjacent overlapped Stokes spectra in two stages of a transient stimulated Raman chirped-pulse amplifier, tuned respectively to the vibrational modes at 901 and 767 cm−1 of a potassium gadolinium tungstate [KGd(WO4)2] crystal, is demonstrated. The contribution of the spatio-temporal overlap of seed and pump pulses, as well as the self-phase modulation, was investigated. The noncollinear configuration allows the composite bandwidth at the central wavelength of 1120 nm to be increased by a factor of 23 compared to the pump pulse bandwidth of 1.6 nm. After reaching a conversion efficiency of 35% in the second stage, the compressibility of a chirped Stokes pulse with a tailored spectrum was also investigated.

Sonochemically Prepared GdWNFs/CNFs Nanocomposite as an Electrode Material for the Electrochemical Detection of Antibiotic Drug in Water Bodies

The work demonstrates the development of an electrochemical sensor for quantification of Chloramphenicol (CA) using pencil graphite electrode (PGE) modified with Gadolinium tungstate nano flakes and carbon nano fibers composite (PGE/GWNfs/CNFs). The composite was further characterized and confirmed by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy, transmission electron microscopy analysis. The prepared GWNfs/CNFs nano composite was fabricated by drop casting method to get PGE/GWNfs/CNFs working electrode. The modified electrode is then analyzed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) methods for its electrochemical and electrocatalytic property. The electrochemical investigation of developed sensor shows enhanced activity towards electro-oxidation of CA. The DPV studies revealed high efficacy characteristics such as sensitivity in the range 0.03984 µA µM−1 cm−2, selectivity, good linear range (5–50 μM), and low detection limit (0.4 μM). The study benchmarks the use of GWNfs/CNFs as an excellent transducer material in electrochemical sensing of CA in standard samples thus, it finds an efficient potential application in the analysis of CA in environment sample analysis.

Noncritical acousto-optic Bragg phase matching: analysis of orthorhombic and monoclinic crystal systems.

Anisotropic acousto-optic diffraction in crystals is the fundamental phenomenon that is used to design acousto-optic tunable filters. Noncritical and quasicollinear phase-matching geometries of Bragg acousto-optic diffraction are compared for acoustic symmetry planes in four crystal systems (tetragonal, trigonal, orthorhombic, and monoclinic). The results for uniaxial crystals are reviewed and generalized for biaxial crystals. It is shown that cubic frequency dependence on the Bragg angle exists in two symmetry planes of orthorhombic crystals and conditionally exists in the symmetry plane of monoclinic crystals. It is also shown that there are two points in the symmetry plane of monoclinic crystals where noncritical phase matching takes place in quasicollinear diffraction geometry that can be used to design high-resolution tunable filters. Phase-matching configurations in α-iodic acid and potassium gadolinium tungstate crystals are analyzed.

Raman wavelength conversion in a multipass cell.

Positively chirped femtosecond pulses at 1030 nm are wavelength-converted using spontaneous and stimulated Raman scattering in a potassium gadolinium tungstate crystal inserted inside a multipass cell. Recirculation in the cell and the Raman material allows both a high conversion efficiency and good spatial beam quality for the generated Stokes beams. The converted pulses can be compressed to sub-picosecond duration. Multipass cells could be an appealing alternative to other Raman shifter implementations in terms of thermal effects, control of the Raman cascade, and overall output beam quality.

High-order stimulated Raman scattering in KGd(WO4)2 employing aperture

An approach that employs the aperture in front of the Raman crystal for the generation of high-order stimulated Raman scattering (SRS) was proposed. Furthermore, first- to fifth-order anti-Stokes components (508, 486, 465, 447, and 430 nm) and first- to fifth-order Stokes components (559, 588, 621, 658, and 700 nm) were generated by a potassium gadolinium tungstate (KGW) Raman generator, which were the highest-order SRS generated in KGW. The effect of the aperture was discussed, and the angular dependence of Stokes was calculated theoretically and experimentally.

Investigation of high-energy extracavity Raman laser oscillator and single-pass Raman generator based on potassium gadolinium tungstate (KGW) crystal

Herein, a high-energy all-solid-state extracavity Raman oscillator and a high-energy single-pass Raman generator based on potassium gadolinium tungstate (KGW) crystal are theoretically and experimentally investigated. First, a high-energy 1064 nm nanosecond laser system with a maximum output energy of 7.03 J at a repetition rate of 1 Hz is built as the pumping source for stimulated Raman scattering (SRS). Then, the output spectra and energy of multiorder Stokes lasers from 1.16 to 1.49 μm are gradually detected as the 1064 nm pumping laser energy increases for both Raman laser structures. For the extracavity Raman oscillator, under a pumping energy of 1.8 J, three-order Stokes lasers with a maximum energy of 448 mJ are obtained when the electric field direction of the pumping laser is parallel to the Ng optical axis of the KGW crystal (E∥Ng). Moreover, to obtain a higher output of the Raman laser without damaging the cavity mirrors, a single-pass Raman generator is studied for comparison purposes. As the 1064 nm pumping laser energy of 2.8 J is injected, the measured maximum output energy of a two-order Stokes laser is ~ 676 mJ for the E∥Ng condition; this is the highest Stokes energy output of the nanosecond solid-state Raman lasers to the best of our knowledge.

Extreme acoustic anisotropy in crystals visualized by diffraction tensor

Anisotropic acoustic wave propagation in single crystals is a fundamental phenomenon enabling operation of various acoustic, acousto-electronic and acousto-optic devices. It provides a variety of device performances and application fields, but its role in pre-estimation of achievable device characteristics and location of crystal orientations with desired properties is often underestimated. A geometrical image of acoustic anisotropy can be an important tool in design of devices based on wave propagation in single crystals or combinations of anisotropic materials. We propose a fast and robust method for survey and visualization of acoustic anisotropy based on calculation of the eigenvalues of bulk acoustic wave (BAW) diffraction tensor (curvature of the slowness surface). The stereographic projection of these eigenvalues clearly reveals singular directions of BAW propagation (conical acoustic axes) in anisotropic media and areas with large and small BAW beam divergence. The method is illustrated by application to three crystals of different symmetry used in different types of acoustic devices: paratellurite, lithium niobate and potassium gadolinium tungstate. The specific features of acoustic anisotropy are discussed for each crystal in terms of their potential application in devices. In addition, we demonstrate that visualization of acoustic anisotropy of lithium niobate helps to find orientations supporting propagation of high-velocity surface acoustic waves.

Integrating the second near-infrared fluorescence imaging with clinical techniques for multimodal cancer imaging by neodymiumdoped gadolinium tungstate nanoparticles

Second near-infrared (NIR-II) fluorescence imaging is a recently emerged technique and is highly useful for accurate diagnosis of cancer. Although a diverse array of fluorescent nanomaterials have been developed to enable NIR-II fluorescence in various situations, they normally fail to unify the clinical techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI). Therefore, exploiting multimodal agents to integrate the newly emerged NIR-II fluorescence and traditional clinical techniques would be of key significance. Here, we report a rational fabrication of neodymium (Nd)-doped gadolinium tungstate nanoparticles (NPs) that are subsequentially decorated with a hydrophilic layer and demonstrate that they can achieve the harmonious integration of NIR-II fluorescence imaging, CT, and MRI. The NIR-II fluorescence emission was activated by an incident light with discrete wavelength ranging from 250 to 810 nm. NIR-II fluorescence-CT-MRI associated trimodal imaging was subsequently demonstrated for breast cancer by an 808 nm laser, along with the estimation of NIR-II fluorescence imaging for cervical cancer. The integration of newly emerged and traditional clinical imaging techniques highlights the huge potential of rare-earth-doped NPs for multimodal imaging of different types of cancer.

High-power diode-pumped Nd:GdVO4/KGW Raman laser at 578 nm.

A diode-pumped neodymium-doped gadolinium vanadate (Nd:GdVO4) laser is developed as a compact efficient yellow light at 578 nm by means of intracavity stimulated Raman scattering (SRS) in a potassium gadolinium tungstate (KGW) crystal and the second-harmonic generation in a lithium triborate crystal. The SRS process with a shift of 768cm-1 is achieved by setting the polarization of the fundamental wave along the Ng axis of the KGW crystal. The self-Raman effect arising from the Nd:GdVO4 crystal is systematically explored by employing two kinds of coating specification for the output coupler. With a specific coating on the output coupler to suppress the self-Raman effect, the maximum output power at 578 nm can reach 3.1 W at a pump power of 32 W. Moreover, two different lengths for the Nd:GdVO4 crystal are individually used to verify the influence of the self-Raman effect on the lasing efficiency.

A theoretical insight into the microstructure and electronic properties of Ho3+-doped potassium gadolinium tungstate

We have systematically studied the structural evolutions of trivalent holmium ion (Ho3+) doped potassium gadolinium tungstate (KGd(WO4)2) crystals by means of the CALYPSO structure search method coupled with first-principles calculations. The unbiased global minimum structure search is successful in reproducing the standardized monoclinic structure with C2/c phase for KGd(WO4)2. For the first time, the lowest energy structure of Ho3+-doped KGd(WO4)2 system is identified, which possesses a significantly different monoclinic configuration with P2 space group. It is found that the impurity Ho3+ ions can substitute the sites of Gd3+ ions, forming the [HoO8]13− local units with C2 site symmetry. Our electronic calculations show that the energy band gap of Ho3+-doped KGd(WO4)2 is equal to 3.03 eV. The impurity of Ho3+ ion remains the insulating character of Ho:KGW system. These results could provide important information for understanding the structural evolution and electronic properties of other rare-earth-doped materials.