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ACS Omega Jun 2024The long- and short-range structural chemistry of the C-type bixbyite compounds ThNdCeO, ThNdCeO, and ThNdCeO is systematically examined using synchrotron X-ray powder...
Probing the Long- and Short-Range Structural Chemistry in the C-Type Bixbyite Oxides ThNdCeO, ThNdCeO, and ThNdCeO via Synchrotron X-ray Diffraction and Absorption Spectroscopy.
The long- and short-range structural chemistry of the C-type bixbyite compounds ThNdCeO, ThNdCeO, and ThNdCeO is systematically examined using synchrotron X-ray powder diffraction (S-PXRD), high-energy resolution fluorescence detection X-ray absorption near edge (HERFD-XANES), and extended X-ray absorption fine structure spectroscopy (EXAFS) measurements supported by electronic structure calculations. S-PXRD measurements revealed that the title compounds all form classical C-type bixbyite structures in space group 3̅ that have disordered cationic crystallographic sites with further observation of characteristic superlattice reflections corresponding to oxygen vacancies. Despite the occurrence of oxygen vacancies, HERFD-XANES measurements on the Ce L-edge revealed that Ce incorporates as Ce into the structures but involves local distortion that resembles cluster behavior and loss of nearest-neighbors. In comparison, HERFD-XANES measurements on the Nd L-edge supported by electronic structure calculations reveal that Nd adopts a local coordination environment similar to the long-range C-type structure while providing charge balancing for the formation of oxygen defects. Th L-edge EXAFS analysis reveals shorter average Th-O distances in the title compounds in comparison to pristine ThO in addition to shorter Th-O and Th-Ce distances compared to Th-Th or Ce-Ce in the corresponding F-type binary oxides (ThO and CeO). These distances are further found to decrease with the increased Nd content of the structures despite simultaneous observation of the overall lattice structure progressively expanding. Linear combination calculations of the M-O bond lengths are used to help explain these observations, where the role of oxygen defects, via Nd incorporation, induces local bond contraction and enhanced Th cation valence, leading to the observed increased lattice expansion with progressive Nd incorporation. Overall, the investigation points to the significance of dissimilar cations exhibiting variable short-range chemical behavior and how it can affect the long-range structural chemistry of complex oxides.
PubMed: 38947849
DOI: 10.1021/acsomega.4c02200 -
Dalton Transactions (Cambridge, England... Jul 2024In this work, PbSbO-type oxides LaMTeO (M = Ga and Mn) were synthesized and structurally characterized by Rietveld refinements against high-resolution X-ray powder...
In this work, PbSbO-type oxides LaMTeO (M = Ga and Mn) were synthesized and structurally characterized by Rietveld refinements against high-resolution X-ray powder diffraction data. The Ga/Te partial ordering within the honeycomb-like two-dimensional [GaTeO] anionic layer leads to the loss of the inversion center between Ga and Te; however the inversion center on the 3̄-roto-inversion axis is preserved, thereby resulting in a 2-fold PbSbO-type superstructure by doubling the -axis associated with a structural symmetry descending from the original 3̄1 to 3̄1 symmetry. In contrast, LaMnTeO (2/) adopts a monoclinically distorted 4-fold superstructure with lattice dimensions of ≈ , ≈ √3, ≈ 2, where and represent the lattice parameters of trigonal PbSbO. The formation of this 2/-superstructure is attributed to the combination of complete Mn/Te ordering and the first-order Jahn-Teller distortion of Mn with the electronic configuration of . Such a monoclinic distortion can effectively lift the Mn spin moments arranged on the triangular sublattice, resulting in a sharp peak for antiferromagnetic transition, which is in stark contrast to subtle magnetic transitions for PbSbO-type tellurates AMn(VI)TeO (A = alkaline earth and Pb) and LnCrTeO (Ln = rare earth) with higher structural symmetry. Our findings highlight that the electronic configuration effects of M-cations play a critical role in controlling the structure symmetry of LaMTeO, providing a strategy to fine-tune the crystal structures and physical properties.
PubMed: 38946522
DOI: 10.1039/d4dt01486c -
Inorganic Chemistry Jul 2024The first fully inorganic Pt(IV) carbonato-complex -[Pt(CO)(OH)] with a {PtO} coordination sphere was isolated as the (MeN)[Pt(CO)(OH)] () salt. The compound was...
The first fully inorganic Pt(IV) carbonato-complex -[Pt(CO)(OH)] with a {PtO} coordination sphere was isolated as the (MeN)[Pt(CO)(OH)] () salt. The compound was characterized using single-crystal and powder X-ray diffraction, Raman spectroscopy, infrared spectroscopy (FTIR), electrospray ionization mass spectrometry (ESI-MS), nuclear magnetic resonance spectroscopy (NMR), and thermogravimetric analysis (TG). Density functional theory (DFT) calculations were also performed to analyze the spectral features of the complex. crystallizes in the triclinic system (P-1) with a Z of 1. The -[Pt(CO)(OH)] anion has axial hydroxo ligands and κ-CO ligands, which form an equatorial plane. This anionic complex exhibits notable stability in aqueous solutions, while the axial hydroxo ligand can be readily modified, as exemplified by the acylation of the -[Pt(CO)(OH)] into -[Pt(CO)(OAc)] anion. Furthermore, it has been shown that rigid and glittering platinum coatings can be electrochemically deposited from an aqueous solution of without the addition of surfactants.
PubMed: 38946343
DOI: 10.1021/acs.inorgchem.4c00909 -
Journal of Contaminant Hydrology Jun 2024Geological carbon sequestration is a promising technique to reduce atmospheric greenhouse gas emissions. The Washita-Fredericksburg formation in the southeastern United...
Geological carbon sequestration is a promising technique to reduce atmospheric greenhouse gas emissions. The Washita-Fredericksburg formation in the southeastern United States is being considered as a prospective storage formation. This requires understanding the geochemical impact of CO injection on the formation, which is the focus of this work. Here, sandstone samples from the Washita-Fredericksburg formation are analyzed to understand their overall mineralogical composition and the potential geochemical processes that might occur following CO injection. Powder X-ray diffraction (XRD) analysis, Scanning Electron Microscopy (SEM) imaging, and image analysis were used to identify mineral phases. SEM images were processed to create a segmented mineral map, which was then used to calculate mineral volume fractions and porosity. Results show that the sample has a porosity of 20% and is mainly composed of quartz, K-feldspar, muscovite, and clays. Accessory minerals such as titanite were also found. Reactive transport models were constructed to assess potential CO-brine-mineral interactions following CO injection. Simulation results suggest that the overall extent of mineral dissolution and precipitation reactions over 10,000 days is limited, with muscovite dissolution increasing porosity to 22%. Limited mineral reactions suggest more injected CO will exist in free and dissolved forms, which may require more extensive long-term monitoring.
PubMed: 38945075
DOI: 10.1016/j.jconhyd.2024.104393 -
Dental Materials : Official Publication... Jun 2024To assess the influence of calcination process on the properties of minimally processed recycled 3Y-TZP, and to compare it with its commercial counterpart.
OBJECTIVE
To assess the influence of calcination process on the properties of minimally processed recycled 3Y-TZP, and to compare it with its commercial counterpart.
METHODS
Non-milled 3Y-TZP waste was collected, fragmented and ball-milled to a granulometric < 5 µm. Half of the recycled powder was calcined at 900 °C. Recycled 3Y-TZP disks were uniaxially pressed and sintered to create two recycled groups: 1) Calcined and 2) Non-calcined to be compared with a commercial CAD/CAM milled 3Y-TZP. The microstructure of experimental groups was assessed through density (n = 6), scanning electron microscopy (n = 3) and energy-dispersive X-ray spectroscopy (n = 3); and the crystalline content was evaluated through X-ray diffraction (XRD) (n = 3). Optical and mechanical properties were investigated through reflectance tests (n = 10), and Vickers hardness, fracture toughness (n = 5), and biaxial flexural strength tests (n = 16), respectively. Fractographic analysis was performed to identify fracture origin and crack propagation. Statistical analyses were performed through ANOVA followed by Tukey´s test, and by Weibull statistics.
RESULTS
Particle size distribution of recycled powder revealed an average diameter of ∼1.60 µm. The relative density of all experimental groups was > 98.15 % and XRD analysis exhibited a predominance of tetragonal-phase in both recycled groups, which were similar to the crystallographic pattern of the control group. Cross-section micrographs presented flaws on the non-calcined group, and a more homogeneous microstructure for the calcined and commercial groups. Commercial samples showed lower contrast-ratio and higher translucency-parameter than the recycled groups, where non-calcined presented higher translucency-parameter and lower contrast-ratio than its calcined counterpart. The commercial group presented higher fracture toughness and characteristic strength than the recycled groups. Moreover, the calcined group exhibited higher hardness, characteristic strength, and probability of survival at higher loads than the non-calcined group. Fractographic analysis depicted the presence of microstructural flaws in the non-calcined group, which may have acted as stress-raisers and led to failures at lower flexural strengths values.
SIGNIFICANCE
The calcination process improved the microstructure, optical, and mechanical properties of the recycled 3Y-TZP.
PubMed: 38944559
DOI: 10.1016/j.dental.2024.06.026 -
Journal of Pharmaceutical Sciences Jun 2024The incorporation of leucine (Leu), a hydrophobic amino acid, into pharmaceutically relevant particles via spray-drying can improve the physicochemical and particulate...
The incorporation of leucine (Leu), a hydrophobic amino acid, into pharmaceutically relevant particles via spray-drying can improve the physicochemical and particulate properties, stability, and ultimately bioavailability of the final product. More specifically, Leu has been proposed to form a shell on the surface of spray-dried (SD) particles. The aim of this study was to explore the potential of Leu in the SD protein/trehalose (Tre) formulation to control the water uptake and moisture-induced recrystallization of amorphous Tre, using lysozyme (LZM) as a model protein. LZM/Tre (1:1, w/w) were dissolved in water with varied amounts of Leu (0 - 40%, w/w) and processed by spray-drying. The solid form, residual moisture content (RMC), hygroscopicity, and morphology of SD LZM/Tre/Leu powders were evaluated, before and after storage under 22°C/55% RH conditions for 90 and 180 days. The X-ray powder diffraction results showed that Leu was in crystalline form when the amount of Leu in the formulation was at least 20% (w/w). Thermo-gravimetric analysis and scanning electron microscopy results showed that 0%, 5%, and 10% Leu formulations led to comparable RMC and raisin-like round particles. In contrast, higher Leu contents resulted in a lower RMC and increased surface corrugation of the SD particles. Dynamic vapor sorption analysis showed that in the 0% Leu formulation, partial recrystallization of amorphous Tre to crystalline Tre·dihydrate occurred, and the addition of as little as 5% Leu could inhibit the recrystallization of amorphous Tre during the water sorption/desorption cycle. In addition, after storage, formulations with higher Leu contents resulted in less water uptake. Rather than recrystallization of amorphous Tre in 0%, 5%, and 10% Leu formulations, recrystallization of amorphous Leu was observed in both 5% and 10% Leu formulations after storage. In summary, our study demonstrated that the addition of Leu has the potential to reduce water uptake and inhibit moisture-induced recrystallization of amorphous Tre in the SD protein/Tre powder system.
PubMed: 38944343
DOI: 10.1016/j.xphs.2024.06.018 -
Journal of Hazardous Materials Jun 2024Serpentinite is a widespread rock type used worldwide as building material. Heavy metals like Ni in both the serpentinite products and serpentinite mining wastes pose...
Serpentinite is a widespread rock type used worldwide as building material. Heavy metals like Ni in both the serpentinite products and serpentinite mining wastes pose potential environmental and health issues. This work devises an analytical protocol to identify and quantify the Ni speciation in the mineralogical matrix, through: i) bulk Ni quantification; ii) quantitative mineralogical and chemical analysis of each Ni-rich mineral; iii) comparison of bulk analysis results with the sum of each contribution from the Ni-rich minerals. As case study, two commercial serpentinites "Verde Giada" (VG) and "Verde Vittoria" (VV) from Valmalenco (Northern Italy) were analysed by ICP-MS, XRPD, TGA-MSEGA, SEM, TEM, EPMA, and micro-Raman spectroscopy. The bulk Ni content is 1500-1750 mg/kg and 1390-1620 mg/kg for VG and VV, respectively. The major minerals from XRPD and EPMA (antigorite, olivine, pyroxene, magnetite, brucite) account for 1094 and 1291 mg/kg of Ni for VG and VV, respectively. SEM/TEM and EPMA highlighted the presence of minor chrysotile, pentlandite, heazlewoodite, awaruite, rising the computed Ni to 1924 and 1761 mg/kg for VG and VV, in good agreement with bulk ICP-MS. This protocol provides robust results and can thus enhance the exposure assessment of Ni and eventually other naturally occurring hazardous metals.
PubMed: 38943892
DOI: 10.1016/j.jhazmat.2024.134928 -
Spectrochimica Acta. Part A, Molecular... Jun 2024Copper oxide nanosheets (CuO NSs) have been successfully obtained by exploiting an effective one-step approach of sugar-blowing method followed by calcination. The...
Copper oxide nanosheets (CuO NSs) have been successfully obtained by exploiting an effective one-step approach of sugar-blowing method followed by calcination. The nanosheets were characterized by several techniques like X-ray powder diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Impressively, CuO NSs display haloperoxidase (HPO) like catalytic activity which catalyses the oxidation of chloride ions by HO giving rise to reactive chlorine species (RCS). A sensitive and selective colorimetric sensor was then demonstrated via the oxidation of chromogenic substrate 3,3',5,5'- tetramethylbenzidine (TMB) by the novel nanoenzyme CuO NSs through the generation of RCS for HO and glucose detection with limit of detection of 109 nM and 21 nM in the linear ranges of 4.6 µM to 769 µM and 0.22 µM to 19.57 µM respectively. Additionally, the methodology is validated for the analysis of glucose in real samples.
PubMed: 38943756
DOI: 10.1016/j.saa.2024.124720 -
Inorganic Chemistry Jun 2024We report on the detailed structural analysis of a series of 11 new quaternary rare earths containing thiosilicates, AkRESiS (Ak = Ca and Sr; RE = La, Ce, Pr, Nd, Sm,...
Crystal Growth of Quaternary AkRESiS (Ak = Ca and Sr; RE = La-Tb) Thiosilicates Using Flux-Assisted Boron Chalcogen Mixture Method: Exploring X-ray Scintillation, Luminescence, and Magnetic Properties.
We report on the detailed structural analysis of a series of 11 new quaternary rare earths containing thiosilicates, AkRESiS (Ak = Ca and Sr; RE = La, Ce, Pr, Nd, Sm, Gd, and Tb), synthesized using the flux-assisted boron chalcogen mixture method. High quality crystals were grown and used to determine their crystal structures by single crystal X-ray diffraction. All members of the AkRESiS series crystallize in the trigonal crystal system with space group 3̅ (space group no. 167). Polycrystalline powders were used for physical property measurements, including magnetic susceptibility, diffuse reflectance in the UV-visible range, and scintillation. Magnetic measurements indicated that CaRESiS (RE = Nd and Tb) exhibits paramagnetic behavior with a slightly negative Weiss constant. The band gaps of the materials were determined from diffuse reflectance data, and optical band gaps were estimated to be 2.5(1) and 2.9(1) eV for CaCeSiS and CaGdSiS, respectively. CaCeSiS, CaTbSiS, and SrCeSiS exhibited intense green luminescence upon irradiation with 375 nm ultraviolet light and, furthermore, scintillated when exposed to X-rays. Radioluminescence measurements of CaCeSiS powder revealed green emission with an intensity approximately 14% of that emitted by bismuth germanium oxide powder.
PubMed: 38943660
DOI: 10.1021/acs.inorgchem.4c01314 -
Analytical Sciences : the International... Jun 2024Nacre powder, often utilized to counterfeit medicinal pearl powder due to their similar chemical composition and appearance, poses a challenge in product authentication....
Utilizing X-ray diffraction in conjunction with competitive adaptive reweighted sampling (CARS) and principal component analysis for the discrimination of medicinal pearl powder and nacre powder.
Nacre powder, often utilized to counterfeit medicinal pearl powder due to their similar chemical composition and appearance, poses a challenge in product authentication. This study introduces a rapid and efficient method for distinguishing between medicinal pearl powder and nacre powder using X-ray diffraction in conjunction with principal component analysis (PCA). The X-ray diffraction pattern underwent preprocessing techniques including smoothing denoising (Savitzky-Golay filter, 5-point) and second-order derivative analysis. Subsequently, PCA was employed for dimensionality reduction modeling. The CARS method was applied to select optimal variables for model refinement, determining the data preprocessing approach and key modeling variables. This method demonstrates the capability to accurately differentiate between pearl powder, nacre powder, and even counterfeit samples containing up to 90% pearl powder. With a high accuracy rate, swift operational speed, and potential for automation, this approach shows promise for practical implementation in the realm of pearl powder quality control.
PubMed: 38942981
DOI: 10.1007/s44211-024-00624-5