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Abstract: Temperature-dependent vibrational (Raman and infrared) spectroscopy and X-ray diffraction studies have been performed on polycrystalline Na2WO4⋅2H2O and Na2MoO4⋅2H2O crystals. Raman data at low temperature 13–300K for sodium tungstate Na2WO4⋅2H2O was compared with the sodium molybdate Na2MoO4⋅2H2O. The infrared and the X-ray diffraction obtained in the 80–300K suggest that both crystals have undergone conformational changes connected with an increase in the Raman intensity of NaO6 modes and the libration modes of water molecules at about 100–120K. Additionally, Raman spectroscopy measurements of Na2WO4⋅2H2O under hydrostatic pressure (from 0 to 5GPa) were performed. The pressure-dependent studies indicate the starting orthorhombic structure is stable in the 0.0–3.2GPa pressure range, and undergoes a phase transition at about 3.9GPa, associated with rotation of units. [Copyright &y& Elsevier]

Abstract This study reports the antibacterial properties and modulation analysis of antibiotic activity by NaCe(MoO 4) 2 microcrystals as well as their structural and morphological characterization. Evaluation of the antibacterial and antibiotic-modulating activity was carried out using the broth microdilution method. The Minimum Inhibitory Concentrations (MICs) of the compounds were expressed as the geometric mean of the triplicate values obtained through the use of Resazurin. Compound concentrations in the plates ranged from 512 to 0.5 μg/mL. Regarding its direct antibacterial activity, NaCe(MoO 4) 2 had a MIC ≥ 1024 μg/mL against all studied strains. As for its modulatory effect, it presented synergism with the antibiotic Gentamicin against the S. aureus strain and with Norfloxacin against E. coli , causing a reduction of 75% and 60%, respectively, in the antibiotic quantity required to have the same effect on the strain in study. [ABSTRACT FROM AUTHOR]

Abstract In this study, we report the antibacterial activity and modulation of antibiotic activity by Fe 2 (MoO 4 ) 3 microstructures obtained by the hydrothermal route without use of surfactants or organic additives. This material was characterized by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) images. The XRD pattern showed that the Fe 2 (MoO 4 ) 3 crystallize in a monoclinic structure without secondary phases. Raman spectroscopy confirms the formation of Fe 2 (MoO 4 ) 3. SEM images show that the Fe 2 (MoO 4 ) 3 obtained have ball-of-yarn shaped morphology. In the antibacterial assays, strains of Escherichia coli , Pseudomonas aeruginosa and Staphylococcus aureus were assayed by microdilution method to evaluate the antibacterial and modulatory-antibiotic activity with antibiotics as gentamicin, norfloxacin and imipenem. Against all bacteria, the Minimum Inhibitory Concentration (MIC) was Fe 2 (MoO 4 ) 3 ≥ 1024 μg/mL. This high MIC result must be associated with the fact of the iron be an essential microelement to the bacterial growth. However, when the Fe 2 (MoO 4 ) 3 was assayed in association with the antibiotics was observed an antagonistic effect demonstrated by an enhance of the MIC. This fact is associated directly with the pro-oxidative properties of metallic oxides. These compounds enhance the production of free radicals, as H 2 O 2 and superoxide ions that can affect the cell structures as cell membrane and cell wall. Other effect is associated with the possible coordination of the metal, performing bonds with the chemical structure of the antibiotics, reducing their activity. Our results indicated that nanocompounds as Fe 2 (MoO 4 ) 3 can not be used as antimicrobial products for clinical usage, neither directly and neither in association with antibiotics. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Sodium-cerium molybdate - NaCe(MoO 4 ) 2 - crystals were synthesized by the conventional hydrothermal method at 150 °C without using organic additives or surfactants. This material was characterized by X-ray diffraction (XRD), Raman and Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), UV–vis diffuse reflectance and zeta potential. The XRD pattern showed that the NaCe(MoO 4 ) 2 crystallizes in a scheelite-type tetragonal structure without secondary phases, as well as Raman and FT-IR spectroscopy confirm the formation of the NaCe(MoO 4 ) 2 tetragonal. SEM images show that the obtained samples have a truncated octahedral morphology with an average side length of ∼1.2 μm and high uniformity. The removal and degradation of Remazol Brilliant Blue (RB) and Methylene Blue (MB) dyes under visible light irradiation were analyzed, showing that the NaCe(MoO 4 ) 2 microcrystals exhibit favorable performance for the removal and/or degradation of these dyes, especially in the MB case. [ABSTRACT FROM AUTHOR]

This study reports the antibacterial properties and modulation analysis of antibiotic activity by β-Ag 2 MoO 4 microcrystals as well as their structural and vibrational characterization. The silver molybdate was obtained by the conventional hydrothermal method, and the structural, vibrational and morphological properties of the sample were determined using X-ray diffraction, Raman spectroscopy and scanning electron microscopy images. β-Ag 2 MoO 4 microcrystals obtained show spinel-type cubic structure (Fd-3m) with irregular shapes. The evaluation of antibacterial and modulatory-antibiotic activity was performed using the microdilution method to determine the Minimum Inhibitory Concentration (MIC) of the β-Ag 2 MoO 4 and antibiotics alone and associated with the silver molybdate. The β-Ag 2 MoO 4 modulates the antibiotic activity against all bacteria assayed in a synergistic (as the norfloxacin and gentamicin against S. aureus and gentamicin against E. coli ) or an antagonistic form (as the norfloxacin against E.coli and P. aeruginosa ). The reversion of antibiotic resistance by combinations with Ag 2 MoO 4 could be a novel strategy to combat infections caused by multiple drug resistance (MDR) pathogens. Our results indicate that these silver molybdates present a clinically relevant antibacterial activity and enhanced the antibiotic activity of some antibiotics against MDR strain of S. aureus and E. coli , being an interesting alternative to combat antibiotic-resistant bacterial infectious agents. [ABSTRACT FROM AUTHOR]

This study reports on the effect of high hydrostatic pressure on the vibrational spectra of Fe 2 (MoO 4 ) 3 microcrystals using Raman scattering in combination with a membrane diamond-anvil cell. The ferric molybdate was obtained by the conventional hydrothermal method, and the structural and morphological properties of the sample were characterized using additionally X-ray diffraction, scanning electron microscopy, as well as energy dispersive spectroscopy. The X-ray diffraction measurements have shown that the crystals have a monoclinic structure. At pressures higher than 4.8 GPa, the disappearance of external modes was observed, suggesting that pressure has induced a breakdown in the translational symmetry of the crystal system. The high-pressure amorphous phase is reversible and attributed to an incomplete crystal-amorphous transformation. [ABSTRACT FROM AUTHOR]