XRPD Data Research Articles

In silico and in vitro investigation of bile salts as coformers for edaravone coamorphous dispersion- Part I

In the present study, we aimed to design the spray-dried coamorphous dispersion (COAM) of a neuroprotective agent-edaravone (EDR) with bile salts to improve oral bioavailability. After the initial screening of different bile salts, EDR-sodium taurocholate (NaTC) COAM showed 4-fold solubility than a pure drug in 1–7 pH range. In silico studies to select coformer for COAM revealed a narrow energy gap, easy charge transfer and high chemical reactivity between EDR and NaTC. The optimized EDR-NaTC COAM in a 1:1 molar ratio was characterized for solid state characterizations and in vitro release study. Hydrogen bond formation between the pyrazolone ring of EDR and the -OH group of the phenanthrene ring of NaTC was observed in the ATR-FTIR spectra of COAM. The DSC and XRPD data indicated the formation of an amorphous halo, whereas SEM photographs demonstrated porous, spherical particles of COAM. The pH-independent in vitro drug release of COAM was observed in 0.1 N HCl, pH 4.5 and 6.8 buffers which was 3-fold higher than EDR. The COAM was stable for 6 months at accelerated condition without showing a change in drug content or devitrification (Initial: 98.002 ± 0.942 %; Accelerated condition: 97.016 ± 1.110 %). Although coamorphous form and hydrogen bonding between EDR-NaTC dispersion were primarily responsible for improved dissolution, NaTC, an exceptional surfactant, has also contributed to it. Moreover, its exclusive structural characteristics could prevent the recrystallization of the drug in supersaturated conditions of the GIT and also minimize the effect of food on oral absorption of EDR which will be studied in animals in the second part of this work.

PCA Analysis of In Situ X-ray Powder Diffraction and Imaging Data Shedding New Light on Solid-State Transformations: The Crystallization of Low Temperature Eutectic Mixtures

Eutectic mixtures are usually studied by differential scanning calorimetry (DSC), able to identify the transition temperatures, possible hysteresis, and investigate the energetic features of transformations. However, DSC is not able to give compositional, structural, or morphological information. A new approach is proposed exploiting powder X-ray diffraction (XRPD) and imaging to overcome the issues posed to diffraction by the presence of an amorphous liquid phase. Principal component analysis (PCA) is applied blindly to in situ XRPD data from both solid and liquid phases in an approach called differential scanning diffraction (DSD), with PCA scores being the reaction coordinate of melting or crystallization steps. PCA was used in a similar way to analyze the imaging data in what was named differential scanning imaging (DSI). Exploiting this approach, the structural and morphological changes during phase transitions can be characterized by XRPD and imaging respectively, complementarily to the energetic effects probed by DSC. Melting and crystallization points can be identified together with the hysteresis between downward and upward temperature ramps, by the structural and morphological viewpoints. A three-component mixture (NaBr, KCl, and water), with wide industrial applications, was studied to describe the behavior around the eutectic composition and examine how small mixture changes can affect the transition temperature and the freezing/melting behaviors. The phase composition at the solid state was elucidated and a new phase of NaBr was identified and its lattice parameters were obtained by XRPD. DSD and DSI resulted complementary to traditional DSC data with many potential applications in solid state chemistry and materials science.

Fluid-rock interaction, skarn genesis, and hydrothermal alteration within an upper crustal fault zone (Island of Elba, Italy)

The Terranera magnetite-hematite-pyrite deposit of the Island of Elba (Italy) is an historical skarn deposit hosted by a fault zone of regional importance (Zuccale Fault) and by its hanging wall rocks.We combine field observations with petrographic data, electron probe microanalyses (EPMA), XRPD data, fluid inclusion microthermometry, and element imaging by Laser Ablation-Inductively Coupled Plasma-Time of Flight Mass Spectrometry (LA-ICP-TOFMS) to define the ore-forming process at Terranera. We show that in this location the fault is made of four levels of mineralized fault rocks having distinct mineral compositions. In these levels, a mineral association made of diopside, clinozoisite, and other Mg-rich minerals is replaced by magnetite, hematite, pyrite, Mg-hornblende, clinochlore, and other Mg-rich phyllosilicates. This paragenesis is overprinted by goethite and clay minerals. Chlorite-quartz geothermometry and fluid inclusion microthermometry show that ore precipitation occurred at 350–180 °C from fluids of distinct bulk salinities, but goethite and clay mineral overprinting progressed at lower T.We propose that Terranera is a magnesian Fe skarn formed due to the interaction between distinct hydrothermal fluids and a dolomitic protolith, which was preserved within the fault zone. These fluids mixed and cooled during protolith metasomatism, causing ore precipitation due to oxidation and desulfidation. A very similar process was described in a large deposit of Elba (Rio Marina). Argillic alteration was widespread within the fault but met permanently intermediate sulfidation conditions. Trace element composition of hematite shows that Terranera has features that overlap those of skarn and epithermal deposits. In particular, elements that are typical of epithermal deposits (Sb, Ga, Ge, As) occur at mass fractions (50–200 μg/g) that are either unreported or not typical of hematite from skarn deposits. These features identify Terranera as formed in an ore environment that was transitional between that of a skarn and of an epithermal deposit. These features are shared by other historical deposits located at Elba and in the massive pyritic ore district of south Tuscany (e.g., Gavorrano, Fenice Capanne). This indicates that a similar environment might have occurred during the Neogene beyond Elba, in a much larger ore district of south Tuscany.

Crystal Structure and Electrical Properties of Ruthenium-Substituted Calcium Copper Titanate.

This paper reports a detailed study of crystal structure and dielectric properties of ruthenium-substituted calcium-copper titanates (CaCu3Ti4-xRuxO12, CCTRO). A series of three samples with different stoichiometry was prepared: CaCu3Ti4-xRuxO12, x = 0, 1 and 4, abbreviated as CCTO, CCT3RO and CCRO, respectively. A detailed structural analysis of CCTRO samples was done by the Rietveld refinement of XRPD data. The results show that, regardless of whether Ti4+ or Ru4+ ions are placed in B crystallographic position in AA'3B4O12 (CaCu3Ti4-xRuxO12) unit cell, the crystal structure remains cubic with Im3¯ symmetry. Slight increases in the unit cell parameters, cell volume and interatomic distances indicate that Ru4+ ions with larger ionic radii (0.62 Å) than Ti4+ (0.605 Å) are incorporated in the CaCu3Ti4-xRuxO12 crystal lattice. The structural investigations were confirmed using TEM, HRTEM and ADF/STEM analyses, including EDXS elemental mapping. The effect of Ru atoms share in CaCu3Ti4-xRuxO12 samples on their electrical properties was determined by impedance and dielectric measurements. Results of dielectric measurements indicate that one atom of ruthenium per CaCu3Ti4-xRuxO12 unit cell transforms dielectric CCTO into conductive CCT3RO while preserving cubic crystal structure. Our findings about CCTO and CCT3RO ceramics promote them as ideal tandem to overcome the problem of stress on dielectric-electrode interfaces in capacitors.

Self-assembly of new cobalt complexes based on [Co (SCN)4], synthesis, empirical, antioxidant activity, and quantum theory investigations

The cobalt (II) complexes have been synthesized from the reaction of the cationic entities (3,4-dimethylaniline (1) and histamine (2)) with metallic salt CoCl2⋅6H2O and thiocyanate ion (SCN−) as a ligand in H2O/ethanolic solution and processing by the evaporation crystal growth method at room temperature to get crystals. The synthesized complex has been fully characterized by single-crystal X-ray diffraction. UV–Visible, FTIR spectroscopy, TGA analysis, and DFT circulations were also performed. The crystal structural analysis reveals that the solid (1) {[Co(SCN)4] (C8H12N)3}·Cl crystallizes in the monoclinic system with the space group P21/n and the solid (2) {[Co(SCN)4](C5H11N3)2}·2Cl crystallizes in the monoclinic space group P21/m. Metal cations are joined into corrugated chains parallel to the b-axis direction in (1) and (2) by four thiocyanate anions. The crystal structures of (1) and (2) were calculated using XRPD data, indicating that they are closely connected to the DRX mono-crystal results. Different interactions pack the system into a ring formed by N–H⋯Cl and N–H⋯S hydrogen bonds. C–H⋯π and the π⋯π stacking of anilinuim ring for (1) and N–H⋯S intermolecular interactions for (1) and (2) increase the crystals' robustness. Hirshfeld surface analysis cum 2D fingerprint plots visualize the main intermolecular interactions with their contributions in the solid-state phase. The molecular geometries of both complexes obtained from the crystal structure were used for quantum chemical calculation. Here, frontier orbital analysis and electrostatic potential illustrate the chemical reactivities of metal–organic complexes. QTAIM and NCI analysis reveal the strength of interactions at the electronic level.

Crystalline Assembly and Solvent‐induced Solid‐state Transformation of 1D Zigzag Chains Based on Sulfonylcalix[4]arene Trinuclear Co(II) and Zn(II) Clusters

AbstractThe reproducible formation, in mild conditions, of three new 1D zigzag coordination polymers using sulfonylcalix[4]arene (TCASO2), metal M2+ cations (M=Co or Zn) and rigid planar N‐shaped linkers (stilbene‐4,4′‐dicarboxylic acid (1‐2H) or azobenzene‐4,4′‐dicarboxylic acid (2‐2H)) is reported. The obtained coordination compounds (1‐TCASO2Zn3, 1‐TCASO2Co3 and 2‐TCASO2Zn3) are characterized in the crystalline phase using single crystal and powder X‐ray diffraction (XRD and XRPD), TGA and IR‐spectroscopy. The three compounds present the same coordination pattern and 1‐TCASO2Zn3 and 2‐TCASO2Zn3 reveal to be isostructural. Due to a high porosity and amount of accommodated solvent molecules hosted in the network, the generated rigid 1D chains are capable to undergo a reversible dynamic solid‐state transformation in terms of crystal packing, accompanied with release/uptake of DMSO molecules leading to compression/stretching of the unit cell along one of the crystallographic axis which was attested by Rietveld refinement on XRPD data.

Size-strain line-broadening analysis of anatase/brookite (TiO2)-based nanocomposites with carbon (C): XRPD and Raman spectroscopic analysis.

A size-strain line-broadening analysis of the XRPD patterns and Raman spectra for two anatase/brookite (TiO2)-based nanocomposites with carbon (C) was carried out and the results compared with those of a similar sample free of carbon. The crystal structures and microstructures of anatase and brookite, as well as their relative abundance ratio, have been refined from XRPD data by the Rietveld method (the low amount of carbon is neglected). The XRPD size-strain analysis resulted in reliable structure and microstructure results for both anatase and brookite. The experimental Raman spectra of all the samples in the region 100-200 cm-1 are dominated by a strong feature primarily composed of the most intense modes of anatase (Eg) and brookite (A1g). The anatase crystallite sizes of 14-17 nm, estimated by XRPD, suggest the application of the phonon confinement model (PCM) for the analysis of the anatase Eg mode, whereas the relatively large brookite crystallite size (27-29 nm) does not imply the use of the PCM for the brookite A1g mode. Superposition of the anatase Eg mode profile, calculated by the PCM, and the Lorentzian shape of the brookite A1g mode provide an appropriate simulation of the change in the dominant Raman feature in the spectra of TiO2-based nanocomposites with carbon. Raman spectra measured in the high-frequency range (1000-2000 cm-1) provide information on carbon in the investigated nanocomposite materials. The results from field-emission scanning electron microscope (SEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy and nitrogen physisorption measurements support the XRPD and Raman results.

Electrical transport properties of R1.9Cu9.2Sn2.8 compounds

Electrical transport properties of the R 1.9 Cu 9.2 Sn 2.8 (R = Y, Ce, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) compounds with the Dy 1.9 Cu 9.2 Sn 2.8 structure type (space group P 6 3 / mmc ) were studied. Polycrystalline samples were prepared by arc melting of the stoichiometric amounts of the constituent elements (nominal purities: rare earth metals − 99.9 wt. %, Cu − 99.99 wt. %, Sn − 99.999 wt. %) on a water-cooled copper hearth under a protective Ti-gettered argon atmosphere. Subsequently the buttons were annealed at 1 070 K for 720 h in evacuated silica tubes, followed by quenching in cold water. Quality of the prepared samples was tested by X-ray powder diffraction (diffractometer DRON-2.0M, Fe K α radiation) and Scanning Electron Microscopy (REMMA 102-02 electron microscope equipped with an energy-dispersive spectroscopy X-ray analyser). XRPD data were collected in the transmission mode on a STOE STADI P diffractometer (Cu K α 1 radiation). The temperature dependencies of electrical resistivity ( r ( T )) of R 1.9 Cu 9.2 Sn 2.8 stannides were measured employing two-probe method on millimeter-scale, well-shaped pieces cut by spark erosion from the polycrystalline samples in the temperature range 4.2-300 K (R = Ce, Gd, Tb, Dy, Ho, Er, Tm, Yb) and 11-300 K (R = Y, Sm, Lu). Electrical resistivity measurements showed that the resistivity values of the all studied compounds increase with temperature indicating metallic type of conductivity. For Y 1.9 Cu 9.2 Sn 2.8 and Lu 1.9 Cu 9.2 Sn 2.8 stannides, which contain nonmagnetic elements Y and Lu, the absence of transition on the r ( T ) dependences at low temperatures is consistent with the Pauli paramagnetism of compounds. The temperature dependence of the resistivity of Yb 1.9 Cu 9.2 Sn 2.8 compound is almost linear at high temperatures, at low temperature part there is a slight increase in resistivity, which is characteristic of Kondo systems. Change of the resistivity caused by magnetic ordering was not observed in the studied temperature interval for the R 1.9 Cu 9.2 Sn 2.8 compounds where R are Gd, Tb, Ho, Er. The slope change of the resistivity at low temperature part of r ( T ) dependencies for the R 1.9 Cu 9.2 Sn 2.8 compounds with R=Ce, Dy, Tm is associated with their magnetic ordering. Keywords : intermetallics, electrical resistivity, X-ray analysis, crystal structure.

Fabrication of ceramic monoliths from diatomaceous earth: effects of calcination temperature on silica phase transformation

The raw diatomaceous earth from the vicinity of Bitola (North Macedonia) showed low bulk density (0.61-0.69 g/cm3), high-water absorption (75-81%) and porosity (66- 72%). The chemical composition was determined with ICP-MS, revealing the following results for the diatomaceous earth: SiO2 (63.69 wt%), Al2O3 (11.79 wt%), Fe2O3 (5.95 wt%), MnO (0.15 wt%), TiO2 (0.65 wt%), CaO (1.51 wt%), MgO (2.24 wt%), P2O5 (0.13 wt%), K2O (1.64 wt%), Na2O (0.93 wt%), LOI (11.21 wt%). XRPD data of the examined sample of clayey diatomite mainly depicted crystalline behavior with a small presence of amorphous phase. The crystalline mineral phases mainly comprise: silica (quartz), feldspars (plagioclase), mica (muscovite), chlorites and dolomite. SEM and TEM results show cased presence of micro- and nanostructures with pores ranging from 250 to 600 nm. The clayey diatomite was sintered at three temperatures (900, 1000 and 1100?C) for a period of 1 h. XRPD of the sintered samples at 1100?C showed certain thermal stability and formation of new phases (mullite and tridymite) that makes the analyzed diatomaceous earth suitable for production of various types of ceramic, construction and thermal insulating materials.

Transition metal precursor impact on thiocyanate complexes crystallization: Isomorphous cobalt and nickel properties

A novel hybrid organic-inorganic isomorphs, 2-Amino Piridinium di(isothiocyanate) cobalt (1) and 2-Amino Piridinium tetra(isothiocyanate)Nickel (2), were prepared by evaporation crystal growth method at room temperature and characterized by X-ray crystal structure, spectroscopic, electric and optical studies. The crystal structural analysis reveals that the solid (1) crystallizes in the monoclinic space group P 21/c and the solid (2) crystallizes in the triclinic space group P1-.In (1) the metal cations are linked by pairs of μ-1,3-bridging thiocyanate anions into corrugated chains parallel to the b direction, whereas in (2) the [Ni(NCS)4]2− anions are arranged in pairs along the c-axis direction to form anionic layers parallel to the (a, c) plane. The crystal structure of (1) and (2) was determined from XRPD data, which shows that it is strongly related to the DRX mono-crystal obtained results. Intermolecular interactions were investigated by Hirshfeld surfaces and contact enrichment tools. Different interactions packed the system through NH…N, and NH…S hydrogen bonds forming a ring. The organic entities are grouped into dimers for (2) through weak interactions NH…N and NH…S. The robustness of the crystals is also enhanced by CH…π of the piridinium ring and NH…S intermolecular interactions. HOMO and LUMO energy gaps have been computed, where Gap energies revealed a semiconductor behavior. The vibrational absorption bands were identified by infrared spectroscopy. The solid-state UV–Visible absorption spectrum and the photoluminescence spectrum of the title compounds were obtained at room temperature in order to spotlight the optical properties. The di-electrical investigations on (1) and (2) shows an interesting electrical behavior. In the [20–400 °C] range, the thermal behaviors were investigated and showed the decomposition of the two complexes with metal complexes residues.

Preparation and Characterization of Stable Amorphous Glassy Solution of BCS II and IV Drugs.

The focus of the present investigation was to develop amorphous glassy solutions (AGSs) of BCS Class II and IV drugs using sucrose acetate isobutyrate (SAIB). The drugs studied were rifaximin (RFX), dasatinib (DST), aripiprazole (APZ), dolutegravir (DLT), cyclosporine (CYS), itraconazole (ITZ), tacrolimus (TAC), sirolimus (SRL), aprepitant (APT), and carbamazepine (CBZ). AGSs were prepared by dissolving known quantity of the drug in the SAIB at 120 (TAC and APZ), 140 (CYS) or 150 oC (RFX, DST, DLT, ITZ, SRL, APT, and CBZ). They were characterized visually and by NIR, NIR hyperspectroscopy (NIR-H), and XRPD. Stability were determined by exposing open vials to 40 oC/75% RH for a week. AGSs behave like a glassy solid at room temperature and liquified above 60 oC. The solubility of APT, DLT, SRL, APZ, RFX, CBZ, TAC and CYS in SAIB was 0.4±0.0, 1.7±0.4, 1.9±0.0, 21.6±2.6, 36.4±0.9, 76.5±4.0, 115.1±2.3, and 239.0±12.6 mg/g, respectively. NIR, NIR-H, and XRPD data indicated the amorphous nature of the AGSs. Furthermore, AGSs were stable against devitrification on exposure to high temperature and humidity. In summary, SAIB can be employed to develop stable AGSs of poorly soluble drugs to increase dissolution, and oral bioavailability with the addition of hydrophilic excipients.

Synthesis, Structure, and Properties of EuLnCuSe3 (Ln = Nd, Sm, Gd, Er)

EuLnCuSe3 (Ln = Nd, Sm, Gd, Er), due to their complex composition, should be considered new materials with the ability to purposefully change the properties. Samples of the EuLnCuSe3 were prepared using Cu, rare earth metal, Se (99.99%) by the ampoule method. The samples were obtained by the crystallization from a melt and annealed at temperatures 1073 and 1273 K. The EuErCuSe3 crystal structure was established using the single-crystal particle. EuErCuSe3 crystallizes in the orthorhombic system, space group Cmcm, KCuZrS3 structure type, with cell parameters a = 4.0555 (3), b = 13.3570 (9), and c = 10.4602 (7) Å, V = 566.62 (6) Å3. In structure EuErCuSe3, erbium ions are coordinated by selenium ions in the octahedral polyhedron, copper ions are in the tetrahedral coordination, europium ions are between copper and erbium polyhedra layers and are coordinated by selenium ions as two-cap trigonal prisms. The optical band gap is 1.79 eV. At 4.7 K, a transition from the ferrimagnetic state to the paramagnetic state was detected in EuErCuSe3. At 85 and 293 K, the compound is in a paramagnetic state. According to XRPD data, EuLnCuSe3 (Ln = Nd, Sm, Gd) compounds have a Pnma orthorhombic space group of the Eu2CuS3 structure type. For EuSmCuSe3, a = 10.75704 (15) Å, b = 4.11120 (5) Å, c = 13.37778 (22) Å. In the series of EuLnCuSe3 compounds, the optical band gap increases 1.58 eV (Nd), 1.58 eV (Sm), 1.72 eV (Gd), 1.79 eV (Er), the microhardness of the 205 (Nd), 210 (Sm), 225 (Gd) 235 ± 4 HV (Er) phases increases, and the thermal stability of the phases increases significantly. According to the measurement data of differential scanning calorimetry, the EuNdCuSe3 decomposes, according to the solid-phase reaction T = 1296 K, ΔH = 8.2 ± 0.8 kJ/mol. EuSmCuSe3 melts incongruently T = 1449 K, ΔH = 18.8 ± 1.9 kJ/mol. For the EuGdCuSe3, two (Tα↔β = 1494 K, ΔHα↔β = 14.8 kJ/mol, Tβ↔γ = 1530 K, ΔHβ↔γ = 4.8 kJ/mol) and for EuErCuSe3 three polymorphic transitions (Tα↔β = 1561 K, ΔHα↔β = 30.3 kJ/mol, Tβ↔γ = 1579 K, ΔHβ↔γ = 4.4 kJ/mol, and Tγ↔δ = 1600 K, ΔHγ↔δ = 10.1 kJ/mol). The compounds melt incongruently at the temperature of 1588 K, ΔHmelt = 17.9 ± 1.8 kJ/mol and 1664 K, ΔHmelt = 25.6 ± 2.5 kJ/mol, respectively. Incongruent melting of the phases proceeds with the formation of a solid solution of EuSe and a liquid phase.

Synthesis, crystal structure and luminescence property in Y2ZnGe4O12:Eu3+

Exploring an operative approach to design materials for phosphor-converted light-emitting diode (pc-LED) remains a tough challenge, in which host structure of phosphor plays a decisive role. In this paper, we report the synthesis, structure and property analysis of Y2ZnGe4O12:Eu3+. The blue emission (380–500 ​nm) from the host lattice intrinsic defect and the orange-red emission (500–800 ​nm) from Eu3+ under an ultraviolent excitation was observed in the solid solution. EDX analysis and Rietveld refinement on both XRPD and NPD data indicate the existence of host lattice intrinsic defect of Y2ZnGe4O12; Density Functional Theory (DFT) calculations suggest the oxygen and germanium vacancies induce the blue emission. The structural analysis implies the orange-red emission comes from the enhanced 5D0 – 7F4 transition of Eu3+ from an antiprism crystal-field. The exciton distribution mechanism was suggested to explain the light tuning and a mathematical description was given to demonstrate the manipulation of the blue and red lights. This work may inspire further work of new solid-state phosphor designing.

Mineralogy, Geochemistry and Provenance of Coastal Sands from Greece: New Insights on the REE Content of Black Coastal Sands from Aggelochori Area, N.-Greece

Beach sands from Aggelochori coast line are investigated for their geochemistry and REE content, mineralogy and their provenance. These fluvial sands bear heavy minerals enriched horizons (containing minerals such as magnetite, zircon, ilmenite, hematite, rutile and titanite) that can be distinguished due to their black color and are formed usually due to the action of sea waves that deposit the heavy minerals and remove the lighter ones. After a suitable processing (washing, sieving, drying and magnetic separation) of the samples, the mineral constituents and their presence (wt.%) were estimated by XRD. Among the samples, the one being simultaneously the more fine grained and the more zircon-enriched (as suggested by XRPD data and optical microscopy analysis) has been selected for further geochemical analyses. The major and trace elements contents were compared to previously studied REE enriched beach sands from Kavala and Sithonia. Beach sands from Aggelochori area appear to have relatively low REE contents. Considering the provenance of these sediments, we suggest that these sands, are a product of the erosion of multi-sources, including the near-by Monopigado granite, as well as metamorphic rocks, as indicated by the presence of rutile and both ilmenite and magnetite in some samples. Therefore, there are indications of a complex flow pattern that existed at the paleo-catchment area of the deposition.

Co-precipitates of lumefantrine-Eudragit E PO for dissolution improvement

Lumefantrine, an antimalarial drug, is having poor solubility and variable bioavailability. This work is aimed to prepare and evaluate co-precipitate of lumefantrine-Eudragit E PO to improve its dissolution by anti-solvent precipitation. The anti-solvent precipitation technique was used to prepare co-precipitate of lumefantrine-Eudragit E PO at different ratios and based on their solubility; the optimized ratio (1:0.5) was further evaluated for solid state characterization, dissolution and compared with lumefantrine and pure precipitated lumefantrine. The optimized ratio of co-precipitate (1:0.5) was further evaluated which showed a substantial rise in drug solubility of lumefantrine. SEM photographs indicated dispersion of drug in polymer matrix however, no interaction was observed in FTIR studies. Their DSC and XRPD data revealed the conversion of lumefantrine to its amorphous form. Further, a significant improvement in the rate of dissolution was demonstrated by co-precipitate as compare to pure drug or solely precipitated drug. This may be attributed to the partial conversion of lumefantrine in amorphous form and solubilizing capacity of Eudragit E PO. Thus, co-precipitate of lumefantrine-Eudragit E PO was found to be useful in dissolution improvement and can be further studied for stabilization of co-precipitates.

Solid-state synthesis and physico-chemical characterization of modified smectites using natural clays from Burkina Faso

Solid-state intercalation was applied to prepare organo-smectites using cationic surfactants and natural clays containing smectite at various surfactant/smectite ratios. The surfactants enter the interlayers of smectites causing a swelling of the clays. The used clays were collected in Siétougou and Diabari villages located in the eastern part of Burkina Faso. The solid-state intercalation was successful for all four surfactants applied, n-dodecyltrimethylammonium bromide, (n-C12H25(CH3)3NBr), n-tetradecyltrimethylammonium bromide, (n-C14H29(CH3)3NBr), n-hexadecyltrimethylammonium bromide (n-C16H33(CH3)3NBr) and di-n-dodecyldimethyl­ammonium bromide ((n-C12H25)2(CH3)2NBr) at different levels of the cation exchange capacity (CEC). The synthesized organo-smectites were characterized regarding relative density, structural and textural properties. XRPD data showed a systematic increase of the basal spacing of the unit cell of the smectite up to >38 Å at 2.0-CEC loading of the surfactant. This increase indicates that the surfactants penetrated into the smectite interlayers with the surfactants being arranged parallel to the layers at low concentrations and almost perpendicular at high ones. FTIR spectra of the organo-smectites showed a decrease in the intensities of the water bands at around 1630 cm-1 and 3400 cm-1, and new specific bands close to 2920 cm-1 and 2850 cm-1 were assigned to the asymmetric and symmetric stretching of CH2 groups of the surfactants, respectively.
 
 KEY WORDS: Smectite, Organo-smectite, Surfactant, Intercalation
 
 Bull. Chem. Soc. Ethiop. 2021, 35(1), 43-59.
 DOI: https://dx.doi.org/10.4314/bcse.v35i1.4

Automated Full-Pattern Summation of X-Ray Powder Diffraction Data for High-Throughput Quantification of Clay-Bearing Mixtures

AbstractX-ray powder diffraction (XRPD) is found consistently to be the most accurate analytical technique for quantitative analysis of clay-bearing mixtures based on results from round-robin competitions such as the Reynolds Cup (RC). A range of computationally intensive approaches can be used to quantify phase concentrations from XRPD data, of which the ‘full-pattern summation of prior measured standards’ (FPS) has proven accurate and parsimonious. Despite its proven utility, the approach often requires time-consuming selection of appropriate pure reference patterns to use for a given sample. As such, applying FPS to large and mineralogically diverse datasets is challenging. In the present work, the accuracy of an automated FPS algorithm implemented within the powdR package for the R Language and Environment for Statistical Computing was tested on a set of 27 samples from nine RC contests. The samples represent challenging and diverse clay-bearing mixtures with known concentrations, with the added advantage of allowing the accuracy of the algorithm to be compared with results submitted to previous contests. When supplied with a library of 201 reference patterns representing a comprehensive range of phases that may be encountered in natural clay-bearing mixtures, the algorithm selected appropriate phases and achieved a mean absolute bias of 0.57% for non-clay minerals (n = 275), 2.37% for clay minerals (n = 120), and 4.43% for amorphous phases (n = 14). This accuracy would be sufficient for top-3 placings in all nine RC contests held to date (RC1 = 2nd, RC2 = 2nd, RC3 = 1st; RC4 = 2nd; RC5 = 1st; RC6 = 3rd; RC7 = 3rd; RC8 = 1st; RC9 = 2nd). The comparatively low values of absolute bias in combination with the competitive placings in all RC contests tested is particularly promising for the future of automated quantitative phase analyses by XRPD.

Exploring impurity phases derived from the introduction of vanadium ions in yttrium gallium garnet

The associated impurity phases derived from the introduction of vanadium ions in yttrium gallium garnet (YGG) were investigated in detail. The XRPD data indicate that β-Ga2O3 is contained in all synthesized samples and YVO4 can be identified when the V-doped concentration above 0.5 at. %. The existence of β-Ga2O3 is related to the antisite defects usually contained in the garnet host, and the generation of YVO4 is mainly derived from its lower formation temperature in comparison to the garnet phase. The micro-area composition analysis further verifies the existence of impurity phases, and the X-ray computed tomography survey provides a more visualized spatial distribution of the YVO4 phase. Moreover, the fluorescence analysis manifests a more sensitive phase identification than the XRPD technique, and the YVO4 impurity phase can be detected even if the V-doped content is reduced to 0.2 at. %. Additionally, the evaluated V/(V + Y + Ga) ratios from structure refinement coincide well with the theoretical value in the low-doping section, and the slight deviation in the high doping part is mainly attributed to the volatilization of vanadium oxides. What discussed in this study offers a comprehensive analysis strategy for the detection of impurity phases originating from ion doping.

Tailoring surface morphology and magnetic property by precipitants concentrations dependent synthesis of Co3O4 nanoparticles

Cobaltic oxide (Co3O4) nanoparticles were synthesized by co-precipitation method using different concentrations of NaOH and NH4OH. Elemental analysis confirmed the presence of Co and O in the studied samples. The X-ray powder diffraction patterns (XRPD) demonstrated that the synthesized cubic Co3O4 nanoparticles were of good crystallinity and Fourier transform infrared (FT-TIR) data supported the results of XRPD data. Different magnifying field emission scanning electron microscopy (FESEM) images confirmed that the surface of the synthesized Co3O4 nanoparticles were highly dependent on the synthesis condition and used precipitants. The magnetic properties of the synthesized Co3O4 nanoparticles were investigated using vibrating sample magnetometer (VSM) where different precipitants and concentrations influenced the magnetic properties of Co3O4 nanoparticles.

Incorporation of minor constituents into Portland cement tricalcium silicate: Bond valence assessment of the alite M1 polymorph crystal structure using synchrotron XRPD data

Six industrial clinker samples, produced using petroleum coke as kiln fuel, were analysed using high resolution synchrotron XRPD data, one sample (HM) presenting predominantly M1 C3S polymorph. Refinement of data collected on this sample was used to revise the M1 structural model, improving the Rwp and RB of the original model (from Rwp = 9.25 and RB = 5.517 in the original model to Rwp = 8.07 and RB = 2.965). The revised model was validated through bond length and Bond Valence Sum (BVS) distribution. Using the BVS method, two preferential substitutional calcium sites were identified for Mg2+ and two silicon sites for Al3+, while two interstitial sites were identified for S6+ and Fe3+. Using the revised model for refinement of the six industrial clinker samples showed improvement in the Rwp and GoF indices. The amount of M1 and M3 polymorph present was found to be significantly different using the revised M1 C3S model.