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The emerging demand for the fabrication of nonlinear optical materials with high limits of optical power is obvious in nonlinear optics due to their wide application in photonic devices. We report the linear and third-order nonlinear optical properties of Ag-doped CdWO 4 nanorods and their dependence on Ag-doping concentration. CdWO 4 nanorods with different Ag concentrations were synthesized by the chemical precipitation method and characterized by UV–Vis absorption, X-ray diffraction (XRD), Raman, Photoluminescence and its lifetime studies, X-ray Photoelectron spectroscopy and Transmission Electron Microscopy (TEM). The introduction of Ag ions has led to an increased redshift in the CdWO 4 absorption spectra extended into longer wavelength bands, thus enhancing optical absorption within the visible range. The XRD pattern showed that the nanorods crystallized in a monoclinic wolframite structure. The incorporation of Ag in CdWO 4 decreases the luminescence emission intensity due to surface quenching effect. Luminescence lifetime measurement reveals the longer decay lifetime for Ag-doped CdWO 4 nanorods due to the reduction of density of defects and deep trap state. The nonlinear optical behaviour of the nanorods was investigated by an Open aperture Z-scan technique at 532 nm using pulsed wave Nd: YAG laser. Experimental results showed that reverse saturable absorption is responsible for the observed nonlinearity in the nanorods. The addition of Ag can significantly improve the nonlinear absorption coefficient and optical limiting effects of CdWO 4 which can be used as a potential material in nonlinear optical devices. (a) Open aperture Z scan traces & (b) optical limiting curves of Cadmium Tungstate (CdWO 4) nanorods. [Display omitted] • CdWO 4 nanostructures with various concentrations of Ag were synthesized through the Chemical method. • Ag-doped CdWO 4 nanorods possess longer Luminescence lifetime due to the reduction of defects density. • The nonlinear optical behavior of the nanorods was investigated by an open aperture Z-scan technique at 532 nm using pulsed wave Nd: YAG laser. • Two photon absorption (2 PA) followed by reverse saturable absorption (RSA) is responsible for the observed nonlinearity. [ABSTRACT FROM AUTHOR]

Cadmium tungstate (CdWO4) nanorods and CdWO4-reduced graphene oxide (RGO) nanocomposites have been prepared by the hydrothermal method at 140, 160 and 180 oC reaction temperatures. The synthesized samples were characterized by X-ray powder diffraction, scanning electron microscopy (SEM), Fourier transform infrared, photoluminescence spectroscopy and Raman spectroscopy. SEM image showed the pure sample consist of nanorods with 50-100 nm diameter and ~1 µm length. The images of the nanocomposite samples clearly showed existence of CdWO4 nanorods and graphene sheets together. The photocatalytic activities of the as-prepared samples were investigated by degradation of methylene blue under the visible light irradiation. An enhancement in photocatalytic activity was observed with CdWO4-RGO nanocomposites in compare with the pure CdWO4. The effect of reaction temperature on the photocatalytic activity of the prepared nanocomposites was also investigated. The results showed that the CdWO4-RGO sample which prepared at 160 oC has more catalytic activity than the other samples.

Abstract The notable feature of cadmium tungstate (CWO) is quite long (∼ 14. 5 μ s) decay time of its brightest scintillation component. In this paper, the technique and results of high dynamic range measurements of CWO afterglow are discussed. Samples were irradiated by bremsstrahlung of a ∼ 0.5 MeV, 6 μ s electron beam. The afterglow tail of the scintillation curve was measured down to the relative amplitude <10−5. At such intensities, a parasitic fluorescence of a photomultiplier essentially contributes to the total signal. The CWO light emission dynamics is determined by known scintillation components to at least 10−5 level. Constraints on the existence of a possible slower fluorescence component are discussed. Highlights • High dynamic range measurements of CdWO 4 afterglow are presented. • Samples were irradiated by the bremsstrahlung of a ∼ 0.5 MeV, 6 μ s electron beam. • The exponential decay of CdWO 4 scintillation continues to at least to 10−5 level. • Observed afterglow tail attributed to the excitation of the photomultiplier elements. • Constraints for a possible long-living fluorescence component are discussed. [ABSTRACT FROM AUTHOR]

Purpose: Combined kV–MV cone‐beam tomography (CBCT) imaging has been proposed for two potentially important image‐guided radiotherapy applications: (a) scan time reduction (STR) and (b) metal artifact reduction (MAR). However, the feasibility of these techniques has been in question due to the low detective quantum efficiencies (DQEs) of commercially available electronic portal imagers (EPIDs). The goal of the work was to test whether a prototype high DQE MV detector can be used to generate acceptable quality pretreatment CBCT images at acceptable dose levels. Methods: 6MV and 100 kVp projection data were acquired on a Truebeam system (Varian, Palo Alto, CA). The MV data were acquired using a prototype EPID containing two scintillators (a) a standard copper‐gadolinium oxysulfide (Cu‐GOS) screen having a zero‐frequency DQE (DQE(0)) value of 1.4%, and (b) a prototype‐focused cadmium tungstate (CWO) pixelated "strip" with a DQE(0) = 22%. The kV data were acquired using the standard onboard imager (DQE(0) = 70%). The angular spacing of the MV projections was 0.81° and the source output was 0.03 MU/projection while the kV projections were acquired with an angular spacing of 0.4° at 0.3 mAs/projection. Image quality was evaluated using (a) an 18‐cm diameter electron density phantom (CIRS, Norfolk, VA) with nine contrast inserts and (b) the resolution section of the 20‐cm diameter Catphan phantom (The Phantom Laboratory, Greenwich, NY). For the MAR studies, two opposing CIRS phantom inserts were replaced by steel rods. The reconstruction methods were based on combining MV and kV data into one sinogram. The MAR reconstruction utilized mostly kV raw data with only those rays corrupted by metal requiring replacement with MV data (total absorbed dose = 0.7 cGy). For the STR study, projections from partially overlapping 105°kV and MV acquisitions were combined to create a complete dataset that could have been acquired in 18 sec (absorbed dose = 2.5 cGy). MV‐only (4.3 cGy) and kV‐only (0.3 cGy) images were also reconstructed. Results: The average signal‐to‐noise ratio (SNR) of the inserts in the MV‐only CWO and GOS CIRS phantom images were 0.62× and 0.12× the SNR of the inserts in kV‐only image, respectively. The limiting spatial resolutions in the MV‐only GOS, MV‐only CWO, and kV‐only Catphan images were 3, 6, and 8 lp/cm, respectively. In the combined kV/CWO STR reconstruction, all contrast inserts were visible while only two were detectable in the kV/Cu‐GOS image due to high levels of noise (average SNRs of kV/CWO and kV/GOS inserts were 0.97× and 0.18× the SNR of the kV‐only inserts, respectively). In the kV–MV MAR reconstructions, streaking artifacts were substantially reduced with all inserts becoming clearly visible in the kV/CWO image while only two were visible in the kV/Cu‐GOS image (average SNRs of the kV/CWO and kV/Cu‐GOS CIRS with metal inserts were 0.94× and 0.35× the SNRs of the kV‐only CIRS without metal inserts). Conclusions: We have demonstrated that a high‐DQE MV detector can be applied to generating high‐quality combined kV–MV images for SRT and MAR. Clinically acceptable doses were utilized. [ABSTRACT FROM AUTHOR]

The accurate determination of oxidative stress biomarker 3-nitro- l -tyrosine (3-NT) in biological medium is of high medical significance. Here, we report an electrochemical sensor for 3-NT using CdWO 4 nanodots decorated reduced graphene oxide nanocomposite (CdWO 4 ND@RGO) modified screen-printed electrode. The morphological and structural aspects of the composite were analyzed using transmission electron microscopy, Energy-dispersive X-ray spectroscopy, Raman, and X-ray diffraction techniques. The electrochemical and interfacial properties were tested via voltammetry and impedance measurements, respectively. The CdWO 4 ND@RGO was coated on a screen-printed electrode, and the resulting modified electrode displays excellent electrocatalytic ability to 3-NT. An amperometric sensor was fabricated which displayed good sensitivity in the linear range of 18.5 nM–1.84 mM. The detection limit was 3.24 nM (S/N = 3) which surpassed the limits of many existing methods Most of the previously reported 3-NT sensors depends on expensive analytical methods, whereas, the described method is a simple, low-cost, easy-to-make modified electrode that works well even in real samples such as human serum and urine. [ABSTRACT FROM AUTHOR]

For the first time Bi 2 WO 6 /CdWO 4 (BCW) hierarchical heterostructure of CdWO 4 microrods decorated with uniform Bi 2 WO 6 nanoplates was prepared. Using BCW as photocatalyst and O 2 as oxidant, we achieved satisfactory catalytic activity (benzene conversion 7.3% and selectivity of phenol > 99%) in the hydroxylation of benzene to phenol at room temperature. It was found that the unique hierarchical heterostructure is beneficial for the absorption of visible light and the separation of photoinduced charge carriers. Moreover, we confirm the pivotal role of hydroxyl radicals and propose a plausible mechanism for the hydroxylation reaction. [ABSTRACT FROM AUTHOR]

In this paper, an application of silicon drift detectors (SDDs) as photodetectors for large inorganic scintillators is presented. In particular, a $2.3\times 2.3\times 1.5$ cm3 CdWO4 crystal has been coupled to a $3\times 2$ matrix of $8\times 8$ mm2 SDDs both cooled at 125 K, obtaining a scintillation detector whose performances are tested by measuring the $\gamma $ rays emitted by a 228Th source. The SDDs, characterized by high quantum efficiency and low electronic noise, are suitable candidates as photodetectors for high-resolution gamma-ray spectroscopy detectors. On the other hand, CdWO4 is an interesting crystal for the study of rare nuclear decays, such as the possible neutrinoless double beta decay ( $0\nu \beta \beta $ ) of 116Cd. With this prototype, a full-width at half-maximum resolution of 3.09 ± 0.05% at 2615 keV has been measured. This result provides a first validation of the application of this technology to rare event searches. [ABSTRACT FROM AUTHOR]

An in situ detection method for beta-ray distribution was developed. The method uses the gamma-ray sensitivity difference between two scintillators: a cadmium–tungstate (CdWO4) scintillator and a plastic scintillator. The gamma-ray sensitivity ratios for several gamma-ray sources such as 137Cs, 60Co, 22Na, and 54Mn were experimentally characterized. The sensitivity ratio for 137Cs between the CdWO4 and plastic scintillators was 8 ± 0.32, while the sensitivity ratio for beta rays from 90Sr was 1.03 ± 0.006. The beta-ray contributions to the total counts can be evaluated using this characteristic. A combined beta-ray and gamma-ray source was prepared, and its beta-ray distribution was successfully obtained using the proposed method. [ABSTRACT FROM AUTHOR]

Abstract: We proposed a simple solution combustion strategy to fabricate CdWO4 nanoparticles for the first time in two different polymorphs: a stable monoclinic and metastable tetragonal phase. The selective synthesis of polymorphs has been achieved by optimizing oxidizer to fuel ratio. Influence of oxidizer to fuel ratio on the formation of CdWO4 polymorphs is of particular relevance to this study and the significant effects are discussed. A mechanistic comparison of properties between two phases has been carried out. Rietveld analyzes of powder X-ray diffraction patterns were performed using GSAS program. Transmission electron microscope images of as synthesized products show the particle sizes of t-CdWO4 (10-20 nm) are smaller than the particle size of m-CdWO4 (≈30 nm). The specific surface area was found to be 12 and 25 m²/g for tetragonal and monoclinic phases, respectively. Photocatalytic activities were investigated by the degradation of methylene blue solution under UV light irradiation. It was found that the photocatalytic activity of tetragonal phase was higher than monoclinic phase, this can be attributed to smaller particle size and active sites of the catalyst that rely sensitively on synthetic conditions. We also explored the photoluminescence (PL) properties of t-CdWO4 and compared with the PL results of m-CdWO4.Graphical abstract: [ABSTRACT FROM AUTHOR]

The crystal structures of Sr2[WO5] [Pna21, a = 7.2457(3) Å, b = 10.8867(5) Å, c = 5.5391(3) Å, Z = 4, Rint = 0.0671, R1 = 0.0495, wR2 = 0.0462] and Ba2[WO5] [Pnma, a = 7.3828(2) Å, b = 5.71420(10) Å, c = 11.4701(3) Å, Z = 4, Rint = 0.0294, R1 = 0.0146, wR2 = 0.0284] are revised, based on single-crystal XRD data. Furthermore spectroscopic data (infrared, Raman and UV/Vis) assisted by DFT calculations are discussed and first results on the luminescence properties of Sr2[WO5]:Eu3+ are presented. [ABSTRACT FROM AUTHOR]

The crystal structures of Sr2[WO5] [Pna21, a = 7.2457(3) Å, b = 10.8867(5) Å, c = 5.5391(3) Å, Z = 4, Rint = 0.0671, R1 = 0.0495, wR2 = 0.0462] and Ba2[WO5] [Pnma, a = 7.3828(2) Å, b = 5.71420(10) Å, c = 11.4701(3) Å, Z = 4, Rint = 0.0294, R1 = 0.0146, wR2 = 0.0284] are revised, based on single-crystal XRD data. Furthermore spectroscopic data (infrared, Raman and UV/Vis) assisted by DFT calculations are discussed and first results on the luminescence properties of Sr2[WO5]:Eu3+ are presented. [ABSTRACT FROM AUTHOR]

Herein, N doped graphene quantum dots-interspersed Cadmium tungstate (CdWO 4 ) nanorods (N-GQDs-CdWO 4 ) were synthesized via decorating the N-GQDs on the surface of CdWO 4 nanorods in three steps. The morphological and structural properties of the N-GQDs-CdWO 4 nanorods were thoroughly investigated by X-ray diffraction spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier Transform infrared spectroscopy, Raman spectroscopy, and ultraviolet–visible spectroscopy. Based on imaging techniques, it became clear that the N-GQDs decorated on the surface of CdWO 4 nanorods formed a heterostructure. This nanocomposite exhibits enhanced photoelectrochemical performances—more than four times those of bare CdWO 4 . In addition, the nanocomposite's photocatalytic activity under ultra-violet light irradiation was almost six fold that of bare CdWO 4 . We studied the mechanism governing its exceptional performance. It indicates that the existence of a heterostructure induces a synergistic effect between the N-GQDs and CdWO 4 nanorods that bolsters photoelectric performance. Our work provides a feasible method to synthesize 0D/3D nanocomposites with enhanced photoelectrochemical performances, and offers a solution to rectify current solar energy shortfalls. [ABSTRACT FROM AUTHOR]

A series of CdWO 4 doped with different concentrations of Sm 3+ have been successfully prepared by the combination of co-precipitation method with annealing of the precipitate formed. The prepared samples were characterized by XRD, TEM, FT-IR, SAED, EDS and PL. XRD studies exhibited monoclinic wolframite structure of the prepared samples and the crystallinity was increased with the increase of annealing temperature upto 900° C without any structural changes. FT-IR studies indicated vibrational bands of metal cations bonds like Cd-O, W-O and Cd-O-W for the CdWO 4 :Sm 3+ phosphors in the ranges from 400 to 900 cm −1 . Photoluminescence studies showed characteristic emission lines of Sm 3+ centers at 569, 608, 653 and 715 nm upon 279 nm UV light excitation. The observed most intense peak at 653 nm is due to the 4 G 5/2 - 6 H 9/2 transition. The optimum concentration of Sm 3+ was found at 1 at.%. The photoluminescence intensity was increased with the increase of annealing temperature. [ABSTRACT FROM AUTHOR]

In this investigation, a facile precipitation route has been developed for the preparation of cadmium tungstate (CdWO) nanoparticles by using cadmium nitrate hexahydrate and sodium tungstate dehydrate as cadmium and vanadate precursor, respectively. The effect of different capping agents such as glycine, valine, and alanine on the morphology and particle size of the products has been investigated. Facile preparation and separation are important features of this route. This work has provided a general, simple, and effective method to control the composition and morphology of cadmium tungstate in aqueous solution, which will be important for inorganic synthesis methodology. The morphology and particle size of products were investigated by scanning electron microscopy images, X-ray diffraction patterns, ultraviolet-visible and electron dispersive X-ray spectroscopy spectroscopy. The photocatalytic characteristics of as-obtained nanocrystalline cadmium tungstate were also examined by degradation of methyl orange dye as water contaminant. [ABSTRACT FROM AUTHOR]

In this research work, CdWO 4 /polymer composite films with different thicknesses were prepared using Poly-methyl acrylate polymer and synthesized CdWO 4 powder. The CdWO 4 powder was synthesized by a simple co-precipitation method in the laboratory. X-ray diffraction, photoluminescence, Fourier transformed infrared spectroscopy and energy-dispersive X-ray spectroscopy proved that the CdWO 4 powder was successfully prepared. Moreover, photoluminescence analysis showed that adding polymer does not change the emission peak of CdWO 4 . Also, the responses of all samples were measured using an 241 Am alpha source with 1860 Bq activity. Results showed that the sample having thickness of 177 mg/cm 2 has the best counting efficiency (over 2π geometry) among the others. The efficiency measurement was further evaluated using a 230 Th source whose activity is 190.7 Bq. It revealed that the counting efficiency of this sample for both 241 Am and 230 Th was nearly equal. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the electronic structure and optical properties of the single crystal and two-dimensional (2D) structure of cadmium tungstate (CdWO 4 ). This investigation includes calculation of the density of states (DOS), dielectric tensor elements and reflectivity. All the calculations have been done by full potential augmented plane waves plus local orbitals (FP-APW+lo) with Wien2k code. The calculated band gaps for the single crystal and 2D structure along [010] direction are 4.2 and 5.02 eV, respectively. The results show that in the 2D structure of CdWO 4 , the electron density of the surface oxygen atoms is much more than the electron density of the inside oxygen atoms. This difference in the density has the main role in the optical properties. The results of the dielectric tensor elements and reflectivity for the single crystal are in good agreement with the experimental values. The results of the dielectric tensor elements and reflectivity for the 2D structure in comparison with the single crystal have shown that the intensity and place of the calculated peaks reduced and shifted, respectively. These results can be related to the surface oxygen atoms and thickness of the 2D structure. [ABSTRACT FROM AUTHOR]

This work demonstrates the possibility of synthesis of cadmium tungstate at low temperatures using oxide precursors. Cadmium tungstate (CdWO4) scintillator was produced via microwave-assisted hydrothermal reaction using the precursors CdO and WO3. The methodology was based on microwave radiation for heating, which is remarkably faster than the solid-state route or conventional hydrothermal procedure. CdWO4 monoclinic (wolframite) structure was successfully obtained at 120°C for synthesis times as short as 20 min. This route does not require the use of templates or surfactants and yields self-assembled nanorods with size of around 24 ± 9 nm width and 260 ± 47 nm length. The growth mechanism for the formation of CdWO4 involves microwave-induced dissociation of the reagents and solvation of Cd2+ and WO42- ions, which are free to move and start the nucleation process. The luminescence properties of the produced nanoparticles were investigated, presenting a broad emission band at around 500 nm, which is comparable to that observed for samples produced using other chemical routes. This result highlights the great potential of the proposed method as a low-cost and time saving process to fabricate luminescent oxide nanoparticles. [ABSTRACT FROM AUTHOR]

To ensure high-speed analytical support to the technology of cadmium tungstate single crystal growth, we have developed an electrothermal atomic absorption spectrometry technique for analysis of high-purity cadmium and cadmium oxide for the technologically important impurities Ag, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Sn with detection limits from 2 × 10 to 6 × 10 wt %. [ABSTRACT FROM AUTHOR]

Thin CdWO 4 films were produced on various substrates by pulsed laser deposition. A method of producing transparent films of high structural and optical quality on MgO substrate was developed. It is based on deposition of an amorphous film from a non-stoichiometric CdWO 4 –CdO target and a consequent crystallization of the film in oxygen atmosphere at 750 °C. The quality of the films produced was verified by x-ray diffraction, electron probe microanalysis, scanning electron microscopy, Raman and optical spectroscopy. [ABSTRACT FROM AUTHOR]

In this paper, cadmium tungstate (CdWO) nanoparticles were synthesized via a precipitation method based on the reaction between cadmium nitrate hexahydrate and sodium tungstate dihydrate in water. Besides, three surfactant agents such as sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, and polyethylene glycol were used to investigate their effects on the morphology and particle size of CdWO nanoparticles. According to the vibrating sample magnetometer, cadmium tungstate (CdWO) nanoparticles indicated a ferromagnetic behavior at room temperature. To evaluate the catalytic properties of nanocrystalline cadmium tungstate, the photocatalytic degradations of methyl orange under ultraviolet light irradiation were carried out. The structural, morphological, magnetic, and optical properties of as-obtained products were characterized by techniques such as XRD, SEM, EDX, VSM, and UV-Vis spectroscopy. [ABSTRACT FROM AUTHOR]

Ultrafast pulsed laser ablation has been investigated as a technique to machine CdWO 4 single crystal scintillator and segment it into small blocks with the aim of fabricating a 2D high energy X-ray imaging array. Cadmium tungstate (CdWO 4 ) is a brittle transparent scintillator used for the detection of high energy X-rays and γ-rays. A 6 W Yb:KGW Pharos-SP pulsed laser of wavelength 1028 nm was used with a tuneable pulse duration of 10 ps to 190 fs, repetition rate of up to 600 kHz and pulse energies of up to 1 mJ was employed. The effect of varying the pulse duration, pulse energy, pulse overlap and scan pattern on the laser induced damage to the crystals was investigated. A pulse duration of ≥500 fs was found to induce substantial cracking in the material. The laser induced damage was minimised using the following operating parameters: a pulse duration of 190 fs, fluence of 15.3 J cm −2 and employing a serpentine scan pattern with a normalised pulse overlap of 0.8. The surface of the ablated surfaces was studied using scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Ablation products were found to contain cadmium tungstate together with different cadmium and tungsten oxides. These laser ablation products could be removed using an ammonium hydroxide treatment. [ABSTRACT FROM AUTHOR]

The CdWO 4 :Yb 3+ (0.1, 2, 3%) nanophosphors have been synthesized using microwave-hydrothermal treatment. The spectral and kinetic characteristics of their luminescence were studied with the aim to check the possibility of cooperative energy transfer from CdWO 4 self-trapped excitons to Yb 3+ pairs, which can provide down-conversion of UV photons absorbed by the CdWO 4 host into two lower-energy (IR) photons emitted by two Yb 3+ ions. The obtained results have shown the conversion of absorbed UV photons into Yb 3+ IR fluorescence. However, the obtained parameters of decay kinetics of both intrinsic luminescence of CdWO 4 and IR fluorescence of Yb 3+ did not confirm the existence of cooperative energy transfer from STE to two Yb 3+ ions in the studied CdWO 4 :Yb 3+ nanophosphors. The reason is supposed to be rather low concentrations of Yb 3+ obtained in the synthesized samples which prevents the creation of high enough concentration of Yb 3+ pairs with short distances between the ions. [ABSTRACT FROM AUTHOR]

A novel heterojunction photocatalyst CdWO 4 /BiOBr was fabricated combining nano-rod CdWO 4 with flake-like BiOBr through a hydrothermal and subsequently chemical precipitation method. The samples were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray detector (EDS), X-ray diffraction (XRD) and UV–vis spectrophotometer. Moreover the photocatalytic activities were evaluated by decomposing dye molecule RhB under visible light irradiation. The results showed that high photocatalytic performance can be achieved on the heterojunction photocatalysts with the 15% CdWO 4 /BiOBr composite displaying highest activity. The results of the study concluded that it was the introduction of BiOBr into the catalyst that mainly enhanced the activity of the photocatalyst by promoting the separation of electron–hole group on the interface of BiOBr and CdWO 4 . [ABSTRACT FROM AUTHOR]

Bi3+,Eu3+ doped CdWO4 phosphors have been synthesized using a co-precipitation method and regular micro-rods were obtained in Bi3+ or Eu3+ single-doped samples. X-ray diffraction, scanning electron microscopy, UV-vis spectrophotometry, and photoluminescence and decay time measurements were used to characterize the as-prepared samples. CdWO4:Bi3+ and CdWO4:Bi3+,Eu3+ can be excited ranging from 250 to 400 nm. The excitation at 350 nm was assigned to be the Bi3+ 1S0→3P1 transition according to the energy level rules of Bi3+ ions. The origin of O–W charge transfer transition has been analyzed using the calculated band structure and density of states of CdWO4 based on density functional theory. The approach to charge compensation was two impurity ions substituting for three Cd2+ sites. Energy transfer properties from the WO6 group to Bi3+ as well as from Bi3+ to Eu3+ were discussed. The mechanism of energy transfer from Bi3+ to Eu3+ was determined to be the quadrupole–quadrupole interaction and the critical distance of energy transfer from Bi3+ to Eu3+ was calculated to be 15.31 Å. The quantum efficiency, CIE chromaticity and thermal quenching properties have also been investigated. [ABSTRACT FROM AUTHOR]

Cadmium tungstate (CdWO) nanoparticles were synthesized via a sonochemical method based on the reaction between cadmium(II) nitrate hexahydrate and sodium tungstate dihydrate in an aqueous solution. To the best of authors' knowledge, it is the first time that cadmium tungstate was synthesized by ultrasonic method. The structural, morphological, and optical properties of as-obtained products were characterized by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray microanalysis (EDS), and ultraviolet-visible spectroscopy. The as-synthesized cadmium tungstate indicated a ferromagnetic behavior which evidenced by using vibrating sample magnetometer at room temperature. To evaluate the photocatalysts properties of nanocrystalline cadmium tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out. [ABSTRACT FROM AUTHOR]

CdWO 4 /g-C 3 N 4 composite photocatalysts have been successfully synthesized by a simple mixed-calcination method for the first time. X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and diffuse reflection spectroscopy (DRS) were carried out to analyze the crystal structure, morphology and optical property of the as-prepared samples. The photocatalytic experiments on rhodamine B (RhB) degradation showed that the 1:10 CdWO 4 /g-C 3 N 4 photocatalyst exhibited the highest efficiency for degradation of RhB under visible light ( λ > 420 nm), which was almost 1.6 and 54.6 times as high as those of the pure g-C 3 N 4 and CdWO 4 , respectively. This enhancement in visible-light photocatalytic activity of CdWO 4 /g-C 3 N 4 composite should be attributed to the matchable band structures and interfacial interaction between CdWO 4 and g-C 3 N 4 , resulting in the efficient separation and transfer of photogenerated charge carriers. It was corroborated by the photoluminescence spectroscopy (PL) and active species trapping experiments. [ABSTRACT FROM AUTHOR]

The films of photocatalysts have been widely used in decomposition in organic pollutants. In this study, ZnWO 4 and g-C 3 N 4 /ZnWO 4 photocatalysts were made into films. The samples were evidently investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS), field emission on scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photo-electron spectroscopy (XPS), thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) and electrochemical experiments. After modified by g-C 3 N 4 , the g-C 3 N 4 /ZnWO 4 films presented a significantly enhanced photocatalytic performance in degrading phenol under UV irradiation (about 2 times than pure ZnWO 4 ). In conclusion, it was g-C 3 N 4 increasing the separation efficiency of photogenerated electron–hole pairs that contribute to the enhancement of photocatalytic performances. This work is of great value for preparation of photocatalysts films. [ABSTRACT FROM AUTHOR]

The CdWO 4 powders were synthesized by using a high energy ball mill method, and microwave dielectric of (1−x)CdWO 4 –xTiO 2 (0 ≤ x ≤ 0.22) composite ceramics have been investigated. X-ray powder diffraction and SEM analysis revealed that CdWO 4 and TiO 2 coexisted as a mixture. With addition of nanometer TiO 2 , the sintered temperature of CdWO 4 ceramic was reduced from 1025 °C to 900 °C. With increase of x, the Q × f values of (1−x)CdWO 4 –xTiO 2 ceramics decreased and the ε r values increased. The τ f value depends on x as well as sintering temperatures. The ceramics of 0.79CdWO 4 –0.21TiO 2 sintered at 900 °C showed ε r = 13.7, Q × f = 15000 GHz, τ f = 0 ppm/°C and the chemical compatibility with Ag make it suitable as LTCC dielectric devices. [ABSTRACT FROM AUTHOR]

CdWO 4 :Tb 3+ nanofibers were synthesized by a simple electrospinning process and followed by the calcination. The XRD and FTIR results indicated that the as-prepared samples were amorphous and the calcined samples have the pure monoclinic phase. The SEM and TEM showed that nanofibers comprising of lots of small nanoparticles were obtained after the calcination. The excitation and emission spectra of CdWO 4 :Tb 3+ nanofibers suggested that the energy transfer from WO 4 2− to Tb 3+ occurred. Under the ultraviolet excitation, CdWO 4 :Tb 3+ nanofibers emitted green light centered at 545 nm. [ABSTRACT FROM AUTHOR]

The present paper reports synthesis and photoluminescence studies of cadmium tungstate (CdWO4) and cerium-doped cadmium tungstate. The samples were synthesised by low cost and low temperature hydrothermal method and characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence analysis. XRD pattern reveals that the CdWO4has monoclinic wolframite structure. The FTIR spectrum of cerium-doped CdWO4exhibits broadband below 700 cm−1which is due to the δ (Ce–O–C) mode. The TEM images show that size of particle is approximately 60–120 nm in both samples. A broad intense peak was observed at 474 nm when the samples were excited with 263 nm. A broad intense peak was observed at 475 nm when the samples were excited with 600 nm. The intensity of the 474 nm peak decreases with increase in cerium doping concentration. The observation of 475 nm peak when excited with 600 nm is upconversion luminescence. This upconversion emission is due to energy transfer upconversion process involving Cd2+ions and [WO6]6−ions. Ce3+ion is responsible for the peak shift of 6 nm. [ABSTRACT FROM AUTHOR]

Sb3+-activated CdWO4 phosphors were designed according to sp energy levels regularities of Sb3+ ion in some inorganic compounds. The sp energy levels regularities of Sb3+ in dozens of compounds were established with the aid of the dielectric theory of the chemical bond for complex crystals: EA = 6.2187−1.7584 he, EB = 7.019−1.957 he, EC = 7.259−1.964 he. Environmental factor h e of Cd site was calculated to be 1.6583 with the refined crystal structure and refractive index of CdWO4:Sb3+. Sb3+-doped CdWO4 was synthesized through a precipitation method and its structure was refined with the General Structure Analysis System. The transition energy of A band of Sb3+ in CdWO4 can be predicted to be 3.312 eV (374 nm), according to the relationship equation between EA and environmental factor he. By monitoring the 521 nm emission band, the excitation spectrum gives a weak excitation band peaking at 355 nm, which was assigned to the 1S0-3P1 transition of Sb3+ according to our prediction. Thus, Sb3+-doped CdWO4 phosphor was designed and synthesized successfully based on sp energy levels regularities of Sb3+ ion. This work is a great help to understand the spectroscopy of Sb3+ ion and will be useful for the design and development of Sb3+-doped phosphors for applications. [ABSTRACT FROM AUTHOR]

Eu 3+ :CdWO 4 single-phased phosphor for white-light-emitting diode (W-LED) was prepared by a hydrothermal method. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as photoluminescence (PL) spectra. The main luminescence center changed between WO 4 2 − groups and Eu 3+ ions at different pH values, which led to different light-emitting properties of the samples. Under the excitation of 296 nm UV light, stable and independent white emission could be achieved when the pH value of the precursor was 7. The CIE chromaticity coordinates of the Eu 3+ :CdWO 4 phosphor synthesized at pH=7 were x =0.323 and y =0.317, which were close to the values of standard chromaticity ( x =0.33 and y =0.33) for an NTSC system. The CIE chromaticity calculation demonstrated its potential application in white light emission devices based on UV chips. [ABSTRACT FROM AUTHOR]

A strategy for Cd1−xZnxWO4 (x ＜ 0.5) solid solution growth was successfully achieved by the Czochralski method. Polycrystalline samples and crystals of the Cd1−xZnxWO4 system were studied using X-ray diffraction. Furthermore, the scintillation properties of Cd1−xZnxWO4 (x ＜ 0.5) crystals were investigated. It was found that the diffraction peaks of the polycrystalline Cd1−xZnxWO4 (x = 0–1.0) system shift toward higher 2ϑ angles with increasing degree of Zn substitution. A linear relation between the zinc composition x and the lattice parameters of Cd1−xZnxWO4 crystals existed. With increasing zinc content x, the lattice parameters a, b, and c decrease, and the volume of the unit cell decreases. The shift of the lattice parameter presents a trend from CdWO4 to ZnWO4. Energy dispersive X-ray (EDAX) analysis was carried out in order to confirm the composition of Cd1−xZnxWO4 single crystals (x ＜ 0.5). Optical measurements revealed that the solid solution crystals had a high optical transmittance of about 65% in the range of 350–600 nm, and the absorption edges of Cd1−xZnxWO4 crystals exhibit increasing peaks from 317.4 nm to 321.5 nm. The emission peaks showed a red shift from 465.4 nm to 501.2 nm with the increasing content of zinc. Furthermore, it was observed that the light output (L.O.) decreases and the energy resolution (E.R.) increases with the increase in zinc content. [ABSTRACT FROM AUTHOR]

A facile composite-salt-mediated strategy is employed for the first time to synthesize CdWO 4 nanowire and nanoflower arrays on cadmium foil substrates. The photoelectrochemical (PEC) properties are measured on the electrodes made of the CdWO 4 nanowire and nanoflower arrays under the simulated sunlight illumination. Both electrodes display high sensitive response and photocurrent stability. The photocurrent density of the nanowire arrays electrode reach 0.35 mA/cm 2 , which is about 3 times as much as that of the nanoflower array electrode. To improve the visible light photocurrent response, CdS nanoparticles are deposited on the CdWO 4 nanowire arrays to form a CdS/CdWO 4 heterojunction. Remarkably enhanced photoresponse is observed on the CdS/CdWO 4 heterostructure and the photocurrent intensity is about twice as much as that of the electrode made of the pure CdWO 4 nanowire arrays. The photoelectric mechanism is also discussed by the crystal structure and morphology characterization, optical band gap and carrier mobility analysis. This work presents a new design of a photoelectrochemical device for possible applications in photoelectrolysis of water and solar cells or highly sensitive light detection. [ABSTRACT FROM AUTHOR]