Molybdate Crystals Research Articles

Synthesis and performance study of novel antibacterial and anticorrosive polyurethane IPN

Polyaniline has been extensively used for the corrosion protection of polymeric materials. However, there have been few studies on its combined antimicrobial activity when used in combination with silver molybdate. In this study, we synthesized silver molybdate (Ag2MoO4) crystals using a homogeneous precipitation method. Polyaniline-dodecylbenzenesulfonic acid/castor oil(PANI-DBSA/CO) mixtures were prepared in an encapsulated state by in situ polymerisation. Subsequently, PANI/Ag2MoO4-PU interpenetrating polymer network(IPN) composite coatings(P/A-PU) were produced by dispersing Ag2MoO4 and PANI-DBSA/CO in polyurethane using ultrasonic dispersion. The composite coatings were characterized using Fourier transform infrared spectroscopy(FTIR), X-ray diffraction analysis(XRD), and transmission electron microscopy(TEM). The study confirmed that composite coatings with uniformly dispersed nanoparticles of PANI and Ag2MoO4 encapsulated by CO and epoxy resin E-44 grease exhibit improved physico-mechanical characteristics. The research also evaluated the effect of nanoparticles on the corrosion behaviour of the coatings using electrochemical impedance spectroscopy and kinetic potential polarisation experiments. The study investigated the antimicrobial properties of P/A-PU composite coatings on Escherichia coli(E.coli) and Staphylococcus aureus(S.aureus) by conducting bacterial growth curves, protein leakage, and fluorescence staining experiments. The aim was to establish a causal connection between the coated surfaces and the observed antimicrobial properties. The study demonstrated that incorporating IPN of polyaniline polyurethane into the coating composites improved their anticorrosive properties. Furthermore, the addition of silver molybdate at a mass ratio of 0.3 % resulted in a remarkable 99 % antimicrobial activity against E.coli and S.aureus.

ANISOTROPY OF ACOUSTO OPTICAL PROPERTIES IN PbMoO4 CRYSTALS WITH NEODYMIUM ADMIXTURE

The anisotropy of the efficiency of Bragg diffraction of light by longitudinal acoustic waves propagating along the [100] and [001] directions in pure and neodymium-doped lead molybdate crystals has been studied. The Nd impurity concentration was approximately 0.2 mol%. The Dixon method was used to determine the effective photoelasticity constants (peff) and the corresponding acousto-optical quality factors (M2) for various directions of polarization of incident light. The velocity of acoustic waves was determined by measurement the angle of Bragg diffraction on these waves. It is shown that in pure and doped lead molybdate crystals there is a dependence of the peff and M2on the direction of propagation of the acoustic wave and the polarization of the incident light.

C(NH2)3]6Mo7O24: A Guanidinium Molybdate as a UV Nonlinear Optical Crystal with Large Birefringence.

The key to searching novel nonlinear optical (NLO) crystals was effectively combining the NLO-active units to obtain a noncentrosymmetric structure. Nevertheless, the present predicament lies in the growing challenge of discovering novel crystals within conventional inorganic frameworks that surpass the properties of the current NLO materials. In view of this, researchers expanded their research focus to the organic-inorganic hybridization system; it is foreseeable to concentrate the advantages from several kinds of NLO-active units to acquire novel NLO crystals with superior properties. We herein report an organic-inorganic hybrid molybdate crystal, namely, [C(NH2)3]6Mo7O24 (GMO). It was successfully obtained via combining inorganic NLO-active MoO6 octahedra and organic π-conjugated [C(NH2)3]+ groups. GMO demonstrates a moderate second-harmonic-generation response, specifically measuring about 1.3 times the value of KDP. Additionally, it exhibits a significant birefringence value of 0.203 at the wavelength of 550 nm and possesses a wide band gap of 3.31 eV. Theoretical calculations suggest that the optical properties of the GMO are primarily influenced by the synergy effect of [C(NH2)3]+ groups between MoO6 octahedra.

Anisotropic Raman spectral analysis and laser output based on large-sized scheelite bismuth molybdate tungstate mixed crystals

This work presented the near decimeter-sized single crystal growth of Bi2Mo2.6W0.4O12 and the systematic analysis of its Raman spectral characteristics.

Effect of lattice disorder on charge transfer in lead molybdate crystals

*e-mail: tbochkova@meta.uaElectrical properties of PbMoO4 crystals, grown from the stoichiometric charge and non-stoichiometric charge with an excess of MoO3, are studied and compared in this work. The crystals are grown by Czochralski method in the direction at an angle of 30° to [100] axis in (001) plane. The single crystals are free from gas bubbles, cracks and have a weak yellowish color. It is found that the addition ofMoO3 excess (0.5 mol.%) to the stoichiometric charge notably increases the crystal lattice disorder. It is assumed that the appearance of lead ion vacancies plays the main role in the structural disordering. An increase of conductivity in DC and AC field, changes of current-voltage characteristics and AC-conductivity spectra are interpreted based on the model of hopping conductivity in disordered systems.

Exploring of anisotropy of acousto-optic interaction in lead molybdate crystals

The dependence of the elastic and acousto-optic properties of lead molybdate crystals on the direction of the wave vector and the polarization of acoustic and optical waves has been studied. The effective photoelastic constants were determined by the Dixon method for various geometries of the Bragg light diffraction. The dependence of the acousto-optic quality factor on the direction of the wave vector of longitudinal acoustic waves in the symmetry plane has been studied in detail. It is shown that in this case the largest and smallest values of the acousto-optic quality factor are observed when light is diffracted by pure longitudinal waves in this plane. It is also shown that the values of the acousto-optic quality factor in lead molybdate crystals are practically the same as in paratellurite crystals.

The growth and spectroscopic properties of Yb:KNGM crystal: A promising ultrashort pulse laser material

Yb3+-doped mixed laser crystals are widely recognized as materials capable of generating ultrashort pulses and have garnered significant attention in recent times. In this study, we thoroughly examined the structure and spectroscopic properties of a novel mixed molybdate crystal, Yb:KNGM. Notably, we made detailed observations of an exceptionally broad absorption band with a full width at half maximum (FWHM) of 78 nm. The broad absorption band indicates that the commercially available InGaAs laser diode (LD) can be effectively utilized for high pumping efficiency purpose. The absorption and emission cross-section at 967 and 1014 nm were calculated to be 1.56 × 10−20 cm2 and 2.05 × 10−20 cm2, respectively. The FWHM of the emission band reaches a substantial range of 62 nm, making it highly conducive to the production of ultrashort pulse lasers. The bandgap (Eg) was fitted as 3.26 eV by Tauc formula. Positive gain cross-section can be achieved while the β is only higher than 0.2 and a large FWHM of 41 nm was discovered when β is 0.5. The aforementioned merits provide compelling evidence that Yb:KNGM crystal holds great promise as a laser crystal for the application of wild tunable and ultrashort pulse lasers pumped by LD.

Li2100deplMoO4 Scintillating Bolometers for Rare-Event Search Experiments

We report on the development of scintillating bolometers based on lithium molybdate crystals that contain molybdenum that has depleted into the double-β active isotope 100Mo (Li2100deplMoO4). We used two Li2100deplMoO4 cubic samples, each of which consisted of 45-millimeter sides and had a mass of 0.28 kg; these samples were produced following the purification and crystallization protocols developed for double-β search experiments with 100Mo-enriched Li2MoO4 crystals. Bolometric Ge detectors were utilized to register the scintillation photons that were emitted by the Li2100deplMoO4 crystal scintillators. The measurements were performed in the CROSS cryogenic set-up at the Canfranc Underground Laboratory (Spain). We observed that the Li2100deplMoO4 scintillating bolometers were characterized by an excellent spectrometric performance (∼3–6 keV of FWHM at 0.24–2.6 MeV γs), moderate scintillation signal (∼0.3–0.6 keV/MeV scintillation-to-heat energy ratio, depending on the light collection conditions), and high radiopurity (228Th and 226Ra activities are below a few µBq/kg), which is comparable with the best reported results of low-temperature detectors that are based on Li2MoO4 using natural or 100Mo-enriched molybdenum content. The prospects of Li2100deplMoO4 bolometers for use in rare-event search experiments are briefly discussed.

Deep-red laser operation of cleaved single-crystal plates of Eu:CsGd(MoO4)2 molybdate.

We report on the first deep-red laser operation of a heavily Eu3+-doped cesium gadolinium double molybdate crystal with a perfect cleavage. A 17 at. % Eu:CsGd(MoO4)2 laser based on cleaved single-crystal plates generated a maximum continuous-wave output power of 212 mW at 703.1 nm (5D0 → 7F4 transition) with a slope efficiency of 30.1%, a low laser threshold of 51 mW, linear polarization, and a beam quality factor M2 = 1.6-1.7. This monoclinic crystal is promising for deep-red microchip lasers.

First-principles study on optical spectra of lead vacancies in PbMoO4

A photochromic effect caused by lead vacancies presents in the yellowish lead molybdate crystals, which seriously affects the application of the crystals in optical instruments. So it is essential to understand the properties caused by intrinsic defects in lead molybdate crystals. In this work, the defect formation energy has been obtained by taking the finite-size (FNV) correction into consideration. The optical spectra also have been gotten under the consideration of electron-phonon coupling. The calculated results indicate that the spectra of the color centers (VFandVF−) in lead molybdate peaks of 2.43eV and 2.40 eV, respectively, which are in very good agreement with the experimental value of 2.14 eV (580 nm). The positions of the emission peak corresponding to the VFandVF− color centers are 1.97eV and 1.70eV are consistent with the experimental results (1.8eV and 2.1eV). The absorption band 580 nm coincides with the absorption band obtained from our calculation of the lead vacancy, so we predict that the 580 nm absorption band comes from the lead vacancy.

Анизотропия упругих и фотоупругих свойств кристаллов CaМоО4

The anisotropy of the elastic and photoelastic properties of calcium molybdate crystals has been studied for Bragg diffraction of light by longitudinal acoustic waves propagating in the (001) plane. It is shown that the efficiency of the acousto-optic interaction can be characterizedby the introduced acousto-optic efficiency coefficient, which is determined from the elasticand photoelastic constants of the crystal. A strong dependence of the coefficients of the acousto-optic quality and the acousto-optic efficiency on the direction of propagation of acousticwaves in the investigated plane is revealed.

AMoRE Neutrinoless Double Beta Decay Experiment

AMoRE is an international project searching for neutrinoless double beta decay (0νββ) of 100Mo. Highly purified molybdate crystals are utilized with heat-light detection based on magnetic micro-calorimeters operating at 10 mK. The high energy resolution is achieved with the heat sensors capable of efficient background rejection from the dual heat-light detection. The present AMoRE, composed of 18 crystal modules, has been operating at Yangyang underground laboratory with an exposure exceeding 9 kg·year, reaching the best limit for 100Mo 0νββ mode. Moreover, the collaboration builds a large-size detector for a total detector mass of about 180 kg in Yemilab, reaching the world-leading sensitivity for 0νββ search.

Dissolution of Molybdenum in Hydrogen Peroxide: A Thermodynamic, Kinetic and Microscopic Study of a Green Process for 99mTc Production.

99mTc-based radiopharmaceuticals are the most commonly used medical radioactive tracers in nuclear medicine for diagnostic imaging. Due to the expected global shortage of 99Mo, the parent radionuclide from which 99mTc is produced, new production methods should be developed. The SORGENTINA-RF (SRF) project aims at developing a prototypical medium-intensity D-T 14-MeV fusion neutron source specifically designed for production of medical radioisotopes with a focus on 99Mo. The scope of this work was to develop an efficient, cost-effective and green procedure for dissolution of solid molybdenum in hydrogen peroxide solutions compatible for 99mTc production via the SRF neutron source. The dissolution process was extensively studied for two different target geometries: pellets and powder. The first showed better characteristics and properties for the dissolution procedure, and up to 100 g of pellets were successfully dissolved in 250-280 min. The dissolution mechanism on the pellets was investigated by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy. After the procedure, sodium molybdate crystals were characterized via X-ray diffraction, Raman and infrared spectroscopy and the high purity of the compound was established by means of inductively coupled plasma mass spectroscopy. The study confirmed the feasibility of the procedure for production of 99mTc in SRF as it is very cost-effective, with minimal consumption of peroxide and controlled low temperature.

Influence of MnO and ZnO on molybdate crystallization in borosilicate glass

Molybdenum (Mo) is an abundant fission product that is present in high-level radioactive waste. The incorporation of Mo into borosilicate glasses developed for the immobilization of radioactive waste causes alkali and alkaline earth molybdates to crystallize because of their low solubility. This study investigated the effects of adding MnO and ZnO to a fabricated simplified nuclear waste glass on the crystallization of molybdates and structure of the glass. The natural cooling of nuclear waste glasses in canisters was simulated by cooling the molten glass slowly at a rate of 1 °C/min. X-ray diffraction and scanning electron microscopy were used to analyze the crystallization behavior, and X-ray absorption spectroscopy was used to identify the local structures of Mn, Zn, and Mo within the glass. The results confirmed that the addition of MnO and ZnO both increased the solubility of Mo in the nuclear waste glass and preferentially inhibited the formation of alkali molybdate crystals, which deteriorate the chemical durability of the glass. Moreover, the solubility of Mo was further improved by the addition of MnO into Nd2O3-bearing borosilicate glasses. Unlike Nd, the Mo-rich phase barely included Mn and Zn. Both Mn and Zn appeared in a tetrahedral structure that comprised a silicate network. On the basis of the bond valence model, it is suggested that MoO42− units can be directly connected to the Mn and Zn.

Optimization of cryogenic calorimetric detection with lithium molybdate crystals for AMoRE-II experiments

The AMoRE collaboration is preparing for the second phase of the experiment, AMoRE-II, which will exploit a 100 kg of 100Mo isotopes to search for neutrinoless double beta decay from the isotope. Most of the 100Mo isotopes will be contained in the lithium molybdate (Li2MoO4) crystals, which will act as absorbers of cryogenic calorimeters coupled to MMC (metallic magnetic calorimeter) sensors. The detector array will have a total mass of approximately 200 kg with hundreds of detector modules. Hence, considerable effort has been taken to optimize the lithium molybdate crystal detector in terms of the detector performance and preparation procedure to build many detector modules in a reasonable schedule without compromising the detector performance. We found some critical experimental conditions to improve the energy resolution in a series of test experiments. In this paper, we discuss the effect of surface treatment and thermal link connection in improving the energy resolution from 14–15 keV to below 7 keV at 2.615 MeV, 208Tl gamma line, which is near the Q-value of the decay of 100Mo, 3.034MeV. We also report the high discrimination power for the separation of alpha particles using the simultaneous scintillation light detection with a test performed in the cryogen-free dilution refrigerator.

Cosmogenic background study for a ^{100}Mo-based bolometric demonstration experiment at China JinPing underground Laboratory

We perform simulation study for a 10-kg ^{100}Mo-based bolometeric demonstration experiment for neutrinoless double-beta decay (0nu beta beta ) search at China JinPing underground Laboratory (CJPL). Cosmogenic production of radionuclides in ^{100}Mo-enriched lithium molybdate crystals and copper components of the detector system are studied using Geant4 toolkit based on the simulated cosmic ray data from the CRY library. Background energy spectra of the cosmogenic radionuclides including ^{56}Co, ^{82}Rb and ^{88}Y which are harmful for the ^{100}Mo-based 0nu beta beta experiment are investigated. We then evaluate the total cosmogenic background level in the ^{100}Mo 0nu beta beta search energy region of interest (ROI) for the demonstration experiment. After one year of cooling down underground, the residual background contribution is found to be 1.8 times 10^{-6} cts/kg/keV/yr and 3.3times 10^{-4} cts/kg/keV/yr from crystals and copper components, respectively. Furthermore, underground cosmogenic activation of copper and lithium molybdate crystal is calculated based on the simulation spectra of neutron and proton in CJPL. The underground cosmogenic background is found to be negligible in the ROI.

Crystallographic Insights into the Crystal Structure and Intrinsic Properties of Ca12Al14O33-Type Rb3LiZn2(MoO4)4 Single Crystals.

Molybdate oxide materials have attracted considerable academic interest owing to their multifunctional optoelectronic properties and applications. However, to date, studies on the intrinsic properties of multiple molybdates have rarely been implemented. Herein, a prospective triple molybdate crystal, Rb3LiZn2(MoO4)4, with high crystalline quality was successfully grown using top-seeded solution growth (TSSG) approaches. Intriguingly, it affords a cage-like structure with the I4̅3d space group, analogous to that of Ca12Al14O33 (C12A7). The Rb3LiZn2(MoO4)4 crystal exhibits excellent thermal stability up to 603 °C, accompanied by a congruent melting nature. Simultaneously, it preserves the optical merits of a large band gap of 4.10 eV and a wide transmission window of 0.29-5.4 μm, which are superior to those of most molybdate crystals. More importantly, Raman spectroscopic measurements demonstrated that the title compound possesses an intense Raman shift located at 925 cm-1 and narrow line width, facilitating a stimulated Raman laser. In addition, first-principles calculations were also implemented to elucidate the structure-property relationships of Rb3LiZn2(MoO4)4. These observations provide an empirical platform for intuitively comprehending the underlying properties of multiple molybdates and pave the way for exploiting Raman crystals.

An MMC-based cryogenic calorimeter with a massive sodium molybdate crystal absorber for neutrinoless double beta decay searches

Sodium molybdate crystals are excellent scintillating target material that can be used to investigate the neutrinoless double beta decay of 100Mo.Because this material contains Na nuclei, it could also be used to clarify the contribution of Na in the controversial claim of dark matter observation by the DAMA/LIBRA experiment.Recent developments have allowed the growth of sodium molybdate crystals of several hundred grams, which makes it possible to build large scale experiments.Therefore, a cryogenic calorimeter with a crystal of significant mass, which can exploit the excellent energy resolution from thermal signals and particle identification using the scintillation signals,is highly desired. We have developed a cryogenic calorimeter with a cylindrical sodium molybdatecrystal of 178 g with dimensions of 4 cm (height) × 4 cm (diameter) coupled to a metallic magnetic calorimeter (MMC).The detector was also equipped with a light detector with a thin Ge absorber to detect scintillation signals.The detector test measurements showed excellent energy resolution and particle discrimination using dual detection of heat and light signals,and thus demonstrate that the crystal is a promising tool for searching for rare phenomena events. Details of the detector development with the massive sodium molybdate crystal are discussed in this paper along with the performance results from test measurements.

Stimulated Raman Scattering in Pb(MoO4)1−x(WO4)x with x = 0, 0.5, 0.8 and 1.0 with Combined Frequency Shifts on High- and Low-Frequency Raman Modes under Synchronous Picosecond Laser Pumping

Comparative characteristics of spontaneous and stimulated Raman scattering in Pb(MoO4)1−x(WO4)x single crystals (x = 0, 0.5, 0.8, and 1.0) including both the high (ν1) and low (ν2) frequency internal anionic group vibrations have been investigated. It was found that among these crystals, Pb(MoO4)0.2(WO4)0.8 is the most suitable for multi-wavelength Raman laser in several Raman modes simultaneously. This is caused by the optimal relative Mo/W content corresponding to the most efficient coherent combination of the (MoO4)2− and (WO4)2− vibrations enhancing the output radiation characteristics of the synchronously pumped Pb(MoO4)0.2(WO4)0.8 Raman laser. Oscillation of up to twelve, closely spaced SRS components in a range of 1128–1360 nm and the strongest pulse shortening down to 1.16 ps in comparison with not only PbMoO4 and PbWO4 but also with all the earlier investigated nominally pure scheelite-like tungstate and molybdate crystals has been achieved.

Dynamic effect to gyromagnetic factors of the compressed tetragonal molybdenum (V) tetrahedral center in the light-irradiated lead molybdate crystal

The dynamic effect concerning small mixing of first-excited state to ground state due to the ligand vibration (which can bring about a twinkling tetrahedral change from compression to elongation) is introduced to calculate the gyromagnetic (g) factors of the second compressed tetragonal molybdenum (V) tetrahedral center in the light-irradiated lead molybdate crystal. The computed results agree well with the observed values, and the large deviation of the observed g // from ge (≈2.0023, the free electron g factor) is therefore interpreted. The outcomes (particularly, the percentage in time for the twinkling tetrahedral change from compression to elongation) are discussed.