X-ray Powder Diffraction Investigations Research Articles

Sol-gel synthesis of Cobalt-Bismuth substituted strontium hexaferrites and insight into structural refinement, Microstructural, dielectric and spectroscopic properties

Bi and Co-substituted strontium (SrFe12O19) hexaferrites were synthesized using the auto-combustion sol–gel method. The structural, Rietveld refinement, microstructural, spectroscopic, and dielectric characterizations were analyzed with X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and Dielectric analysis, respectively. The XRD investigation of Sr1-xBixFe12-yCoyO19 with (x = 0–0.5, y = 0–1.0) confirmed the single phase of M−type hexagonal ferrites. The change in the value of lattice constant ‘a’ in between 5.87 and 5.95 and ‘c’ 22.07 to 23.81 to be noted. The crystallite size of prepared specimens was determined in (20–29) nm range. The specific stretching vibrations in the FTIR results approves (Fe/Co-O and Bi-O) at three different positions 437.59, 549.94, and 587.53 cm−1. The existence of these band from 437 to 588 cm−1 confirmed the hexagonal structure of these ferrites. The force constants at octahedral sites increased from 1.75 to 2.02 (Dyne cm−1) x 105 and shows insignificant behavior at tetrahedral sites in between (3.33–3.54) Dyne cm−1 x 105 with Bi-Co substitution. The first band 582 cm−1 (ʋ1), is due to the maximum restoring force and vibrations at the tetrahedral site. The second band at a lower wavenumber of ∼ 402 cm−1 (ʋ 2) is due to the vibrations at the octahedral site. The microstructure of all synthesized samples of M−type hexagonal ferrites confirmed using the SEM analysis. The dielectric measurements in 0 to 3 GHZ frequency was done and effect of Bi-Co has been observed. The dielectric constant of all specimens shows the increasing trend from 1.5 GHz to 2.5 GHz with the frequency of the applied AC field. A slight increase was observed in the AC conductivity of these ferrites with the increasing concentration of Bi and Co ions.

Synthesis, crystal structure and thermal properties of the dinuclear complex bis-(μ-4-methylpyridine N-oxide-κ2O:O)bis-[(methanol-κO)(4-methylpyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II)

Reaction of Co(NCS)2 with 4-methyl-pyridine N-oxide in methanol leads to the formation of crystals of the title compound, [Co2(NCS)4(C6H7NO)4(CH4O)2] or Co2(NCS)4(4-methyl-pyridine N-oxide)4(methanol)2. The asymmetric unit consist of one CoII cation, two thio-cyanate anions, two 4-methyl-pyridine N-oxide coligands and one methanol mol-ecule in general positions. The H atoms of one of the methyl groups are disordered and were refined using a split model. The CoII cations octa-hedrally coordinate two terminal N-bonded thio-cyanate anions, three 4-methyl-pyridine N-oxide coligands and one methanol mol-ecule. Each two CoII cations are linked by pairs of μ-1,1(O,O)-bridging 4-methyl-pyridine N-oxide coligands into dinuclear units that are located on centers of inversion. Powder X-ray diffraction (PXRD) investigations prove that the title compound is contaminated with a small amount of Co(NCS)2(4-meth-yl-pyridine N-oxide)3. Thermogravimetric investigations reveal that the methanol mol-ecules are removed in the beginning, leading to a compound with the composition Co(NCS)2(4-methyl-pyridine N-oxide), which has been reported in the literature and which is of poor crystallinity.

Sonochemical synthesis of SnS and SnS2 quantum dots from aqueous solutions, and their photo- and sonocatalytic activity

Our study reports the ultrasound-assisted synthesis of SnS and SnS2 in the form of nanoparticles using aqueous solutions of respective tin chloride and thioacetamide varying sonication time. The presence of both compounds is confirmed by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, as well as Raman and FT-IR spectroscopic techniques. The existence of nanoparticles is proven by powder X-ray diffraction investigation and by high resolution transmission electron microscopy observations. The size of nanocrystallites are in the range of 3–8 nm and 30 50 nm for SnS, and 1.5–10 nm for SnS2. X-ray photoelectron spectroscopy measurements, used to investigate the chemical state of tin and sulphur atoms on the surface of nanoparticles, reveal that they are typically covered with tin on the same oxidation degree as respective bulk compound. Values of optical bandgaps of synthesized nanoparticles, according to the Tauc method, were 2.31, 1.47 and 1.05 eV for SnS (60, 90 and 120 min long synthesis, respectively), and 2.81, 2.78 and 2.70 eV for SnS2 (60, 90 and 120 min long synthesis, respectively). Obtained nanoparticles were utilized as photo- and sonocatalysts in the process of degradation of model azo-dye molecules by UV-C light or ultrasound. Quantum dots of SnS2 obtained under sonication lasting 120 min were the best photocatalyst (66.9 % color removal), while quantum dots of SnS obtained under similar sonication time were the best sonocatalyst (85.2 % color removal).

In situ studies of reversible solid-gas reactions of ethylene responsive silver pyrazolates.

Solid-gas reactions and in situ powder X-ray diffraction investigations of trinuclear silver complexes {[3,4,5-(CF3)3Pz]Ag}3 and {[4-Br-3,5-(CF3)2Pz]Ag}3 supported by highly fluorinated pyrazolates reveal that they undergo intricate ethylene-triggered structural transformations in the solid-state producing dinuclear silver-ethylene adducts. Despite the complexity, the chemistry is reversible producing precursor trimers with the loss of ethylene. Less reactive {[3,5-(CF3)2Pz]Ag}3 under ethylene pressure and low-temperature conditions stops at an unusual silver-ethylene complex in the trinuclear state, which could serve as a model for intermediates likely present in more common trimer-dimer reorganizations described above. Complete structural data of three novel silver-ethylene complexes are presented together with a thorough computational analysis of the mechanism.

Preparation and characterization of polymeric cross-linked hydrogel patch for topical delivery of gentamicin

Abstract This research aimed to prepare and characterize a new type of polymeric cross-linked topical hydrogel patches for the treatment of wound infections. The free radical polymerization method was used to prepare the topical hydrogel patches by utilizing natural polymers, i.e., agarose and gelatin. These natural polymers were chemically cross-linked with monomer (acrylic acid) using ammonium persulfate as an initiator via the cross-linker N,N methylene bisacrylamide. An antibiotic, i.e., gentamicin sulfate was loaded into a designed polymeric system. The polymeric cross-linked topical hydrogel patches were made in a spherical shape, which was revealed to be stable and elastic. Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and X-ray powder diffraction investigation were used to characterize the topical hydrogel patches. Polymeric cross-linked hydrogel patches were evaluated for their sol–gel analysis, swelling studies, in vitro drug release studies against pH 5.5, 6.5, and 7.4, ex vivo drug permeation, and the deposition study on the rabbit’s skin by using a Franz diffusion cell. In addition, the skin irritation study and wound healing performance of drug-loaded topical patches were also assessed and compared to commercially available formulations. The topical hydrogel patches were found to be non-irritating to the skin for up to 72 h as determined by a Draize patch test and when compared to marketed formulations, these topical patches resulted in faster wound healing. The prepared formulation showed promising potential for the treatment of skin wound infection.

Investigations of the L-ornithinium dipicrate nonlinear optical material with an emphasis on very efficient second-harmonic generation in electro-optical and optoelectronic devices

Superior optical fineness and high SHG efficacy LODP crystals were grown using the solution growth approach, which involved slow cooling and slow evaporation methods. The fully developed organic LODP sample crystallized into a monoclinic structure with the noncentrosymmetric space group P21. Along the (1 3 1) track, the seed specimen was cut into pieces for the standard solution growth technique. A single crystal of huge size was completely produced using solubility data and a slow cooling procedure. X-ray diffraction studies on a single crystal were used to determine the unit cell's properties. The produced crystals were characterized using a wide range of techniques, including UV–Vis, dielectric, laser damage threshold (LDT), hardness, and HRXRD experiments to examine their physical and optical properties. The grown LODP largeness crystal has better crystalline fineness and fewer flaws, as exposed by HRXRD and etching studies. The UV–Visible analysis reveals that the SCST-produced LODP crystal has better optical properties than the SEST-grown crystal. When comparing the laser damage thresholds (LDT) of LODP crystals made using SEST and SCST, the latter are shown to be better. Microhardness studies carried out at various temperatures show that crystals grown using the SCST method have more mechanical stability than crystals grown using the SEST method. In contrast to SEST-generated crystals, dielectric dispersion is higher in fully developed SCST-technique crystals. Piezoelectric nature and relative Second Harmonic Generation (for different particle sizes) were also performed. For LODP crystals, third-order non-linear optical properties were obtained through the SEST and SCST techniques using a 632.8 nm He–Ne laser. The powder X-ray diffraction investigation verifies the compound's crystalline form. The existence of LODP components was verified using energy dispersion spectrometry. Thermogravimetric and differential thermal measurements demonstrate the crystal's thermal stability.

The influence of Dy3+ ions doping and annealing temperature on structural, morphological, and spectroscopic properties of lanthanum orthovanadate (LaVO4) material

In the current work, we present the results of nanocrystalline lanthanum orthovanadate (LaVO4) doped with dysprosium ions, which was synthesized by a high-energy ball milling (HEBM) process. Lanthanum, vanadium, and dysprosium oxides were employed as starting reagents. These materials were turned into LaVO4:Dy3+ powder with two polymorphic phases after HEBM and subsequent heating that was carried out in the air in the temperature range from 800 °C to 1200 °C. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and DRS (UV–vis) spectroscopy were used to characterize the obtained Dy-doped LaVO4 powders. The excitation and photoluminescence (PL) emission spectra, and time decay (lifetime) curves of the dysprosium (III) ions in LaVO4 material were measured and analyzed. The influence of annealing temperature and the concentration of dysprosium (III) ions (1%, 2%, and 3% at.) on spectroscopic properties was discussed. The qualitative phase analysis of Dy-doped LaVO4 powders indicated the dominant presence of a monoclinic LaVO4 structure. The presence of the tetragonal solid-solution (La, Dy)VO4 phase was also revealed. The structural transformation consists of an increase of Zr type LaVO4:Dy3+ phase, resulting in a higher structure and site symmetry of t-LaVO4:Dy3+. With increasing Dy3+ content, the relative fraction of the tetragonal (La, Dy)VO4 phase was also increased in all samples. Furthermore, XRD investigations showed that Dy3+ ions were incorporated mainly into the t-(La, Dy)VO4 structure. The increase of the amount of tetragonal phase in polymorphic LaVO4:Dy3+ material results in higher emission intensity caused by more efficient energy transfer from VO43− vanadate group to Dy3+ ions. The average sizes of the m-LaVO4 crystallites, estimated using the Rietveld method, were in a narrow range from 53 to 77 nm. Two main intense emission peaks were observed in the blue (466–495 nm) and yellow (557–594 nm) wavelength ranges and can be ascribed to transitions involving 4F9/2 to the stark split sublevels of 6H15/2 and 6H13/2, respectively. The overall intensity of the emission strongly depends on the annealing temperature. The best results were achieved for powder heated at 1200 °C. The values of the calculated average decay lifetime τavg of the LaVO4 powders doped with 1%, 2%, and 3% at. Dy heated at 800 °C, 1000 °C and 1200 °C were very similar, but one can observe that with increasing heating temperature the average decay lifetime of LaVO4:Dy powders slightly decreased regardless of the Dy concentration.

Hydrothermal Fabrication of GO Decorated Dy2WO6-ZnO Ternary Nanocomposites: An Efficient Photocatalyst for the Degradation of Organic Dye

Environmental and human health are seriously threatened by organic dye pollution. Many efforts have been made to find effective and safe methods of eliminating these contaminants. To mitigate these effects, the hydrothermal method was used to effectively generate a ternary kind of Dy2WO6-ZnO embedded in graphene oxide (DWZG) nanocomposites, which were used to degrade the pollutant. Powder X-ray diffraction (XRD) investigation confirms the crystalline character of the as-prepared DWZG nanocomposite. The Dy2WO6-ZnO composition on the graphene oxide (GO) layer is shaped like a combination of algae (Dy2WO6) and clusters (ZnO), as shown by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) investigation revealed the composition of elements and oxidation state of C, Dy, O, W and Zn elements. Methylene blue (MB) was chosen as the organic dye target for photocatalytic degradation using the produced nanocomposites. MB is degraded with a photocatalytic efficiency of 98.2% in about 30 min using a DWZG catalyst. Based on the result of the research entitled “Reactive Oxidative Species,” the primary reactive species involved in the MB degradation are photo-generated •OH and O2•− radicals. The recycle test was also successful in evaluating the catalysts’ long-term viability as well as their reusability.

Thermodynamic analysis and in situ powder X-ray diffraction investigation of the formation and transformation of mineral phases during pressure oxidation of pyrite

Acid oxidative pressure leaching is a cost-effective way for recovering gold from refractory gold ores such as gold-bearing pyrite, yet our knowledge of the dissolution, crystallization, and phase transformation during pressure leaching is still controversial. This is partially due to the lack of thermodynamic data and in situ studies of the leaching process. Here, we combine thermodynamic modelling and in situ powder X-ray diffraction (PXRD) to investigate mineralogical phase changes during oxidation of pyrite. The polyhedron method has been utilised to estimate the standard Gibbs free energy of formation (∆Gfo) and enthalpy of formation (∆Hfo) of 31 sulphate minerals from 25 °C to 300 °C. The calculated thermodynamic data for the sulphate minerals agree well with the literature, with an average relative error of 0.23% for both ∆Gfo and ∆Hfo demonstrating the reliability of the polyhedron method. Some new thermodynamic data for the mineral phases at elevated temperature was calculated and used to construct the Eh-pH diagrams for the Fe-S-H2O system at 225 °C, which were used to predict phase transformations and chemical reactions during oxidation of pyrite. Based on the analysis of thermodynamic diagrams, the formation of basic ferric sulphate (BFS: Fe(OH)SO4) is favoured at stronger acidic and higher solution redox potential conditions, while hematite and FeSO4∙H2O occur at low solution redox potential conditions. These predictions agreed with the results from laboratory-based in situ PXRD experiments, in which the mineralogical phase transformations were studied during acid pressure treatment of pyrite in a capillary. The influence of initial concentration of ferric ions on the change of mineral phase was revealed. The results confirmed the formation of FeSO4∙H2O and Fe(OH)SO4 phases during the heating (24–225 °C) and annealing stages. These phases may passivate pyrite surface and hence slow down further pyrite oxidation but were re-dissolved during the annealing and/or cooling stages, depending on the initial concentration of ferric ions.

Synthesis of Green Cerium Oxide Nanoparticles Using Plant Waste from Colocasia esculenta for Seed Germination of Mung Bean (Vigna radiata)

Synthesis of cerium oxide (CeO2) nanoparticles (NPs) via biological approach has received a lot of interest to reduce the harmful effects of chemical synthesis. In the present study, Colocasia esculenta leaf extract facilitated the preparation of CeO2-NPs by using the sol-gel technique. The crystal structural of CeO2-NPs was proven by X-ray powder diffraction (XRD) investigation to be cubic with size of 2.94 nm according to Debye–Scherrer equation. As demonstrated in the transmission electron microscopy (TEM) image, CeO2-NPs have a spherical form with an average size of 2.04 nm which is almost consistent with a finding from XRD analysis. Energy dispersive X-ray (EDX) measurements exhibited high-intensity peaks attributed to Ce and oxygen and further proved the creation of CeO2-NPs. The Fourier transform infrared spectroscopy (FTIR) analysis revealed the presence of Ce-O stretching, indicating the formation of CeO2-NPs. Functional groups of O-H, C-O, and C=O peaks were found in a spectrum due to the phytochemical components that were responsible for reducing and stabilizing during the synthesis process of CeO2-NPs. The examined UV-visible spectra exhibited the absorbance peak at 213 nm. The synthesized NPs produced in this study were further investigated for mung bean seed germination, whereby the influence of grain germination and growth rate demonstrated the significant finding.

Synthesis, crystal structure and thermal decomposition pathway of bis-(iso-seleno-cyanato-κN)tetra-kis-(pyridine-κN)manganese(II).

The reaction of MnCl2·2H2O with KSeCN and pyridine in water leads to the formation of the title complex, [Mn(NCSe)2(C5H5N)4], which is isotypic to its Fe, Co, Ni, Zn and Cd analogues. In its crystal structure, discrete complexes are observed that are located on centres of inversion. The Mn cations are octa-hedrally coordinated by four pyridine coligands and two seleno-cyanate anions that coordinate via the N atom to the metal centres to generate trans-MnN(s)2N(p)4 octa-hedra (s= seleno-cyanate and p= pyridine). In the extended structure, weak C-H⋯Se contacts are observed. Powder X-ray diffraction (PXRD) investigations prove that a pure sample was obtained and in the IR and Raman spectra, the C-N stretching vibrations are observed at 2058 and 2060 cm-1, respectively, in agreement with the terminal coordination of the seleno-cyanate anions. Thermogravimetric investigations reveal that the pyridine coligands are removed in two separate steps. In the first mass loss, a compound with the composition Mn(NCSe)2(C5H5N)2 is formed, whereas in the second mass loss, the remaining pyridine ligands are removed, which is superimposed with the decomposition of Mn(NCSe)2 formed after ligand removal. In the inter-mediate compound Mn(NCSe)2(C5H5N)2, the CN stretching vibration is observed at 2090 cm-1 in the Raman and at 2099 cm-1 in the IR spectra, indicating that the Mn cations are linked by μ-1,3-bridging anionic ligands. PXRD measurements show that a compound has formed that is of poor crystallinity. A comparison of the powder pattern with that calculated for the previously reported Cd(NCSe)2(C5H5N)2 indicates that these compounds are isotypic, which was proven by a Pawley fit.

Synthesis, physico-chemical characterization and quantum chemical studies of 2, 3-dimethyl quinoxalinium-5-sulphosalicylate crystal

2,3-dimethylquinoxalinum-5-sulphosalicylate (MQSA) was synthesized and grown into single crystals by slowly evaporating the solvent in methanol at room temperature. According to the lattice parameters found by the SCXRD analysis method (a = 8.8031 (17) Å, b = 17.768(3) Å, c = 10.7979(16) and α = γ = 90°, β = 90.611 (7) °), the crystal belongs to monoclinic crystal system with the P21/n space group. Moreover, powder X-ray diffraction investigation supported the crystalline nature. The compound's UV–Vis spectra exhibited a CT-band with a wavelength maximum of 372 nm, as well as its NIR spectra revealed good optical transmittance in the visible region with a low cut-off wavelength of 376 nm and an optical band gap of 5.12 eV. Dual emission bands at 418 and 484 nm are observed in the PL emission spectra. The synthesized crystal was examined using FT-IR, FT-Raman, and NMR spectral methods. The crystal is thermally stable up to 274 °C, furthermore, TG-DTA and DSC methods were employed to study the degradation process. The second and third-order NLO efficiencies of the crystal was analyzed by Kurtz-Perry powder and Z-scan methods, respectively. The single crystal of MQSA is further studied through Hirshfeld surface analysis, fingerprint plots, and crystal voids analysis to understand the intermoleculiar interactions and individual atomic arrangements inside the crystal. The H…H and O…H/H…O interactions are greatly aided by crystal structure. Additionally, the quantum computational methods were used to assess several molecular level electronic properties, including molecular orbitals, molecular electrostatic potentials maps, linear polarizability and static third-order nonlinear optical (NLO) polarizability, which is a molecular-level NLO response property. The isotropic linear polarizability and NLO polarizability of MQSA are 29.99 × 10−24 esu and 28.45 × 10−36 esu, respectively, in the M06–2X/6–311G* method, which demonstrates the decent potential of the synthesized crystal for its use as NLO materials. Furthermore, the frontier molecular orbitals, molecular electrostatic potentials, and UV–Visible spectrum were calculated and discussed.

Electrochemical sensor of carboxymethyl cellulose and photocatalytic degradation of Navy Blue dye by sonochemically synthesized Titanium oxide nanoparticles

Nanocrystalline titanium oxide nanoparticles (TiO2 NPs) were synthesized by using a low-cost sonochemical method. TiO2 NPs exhibited anatase phase and an average crystallite size of 40.64 ​nm, according to a powder X-ray diffraction (PXRD) investigation. SEM and TEM images revealed spherical shape, with asymmetric geometries for TiO2 NPs. The micrographs thoroughly corroborated the plate-like structure for the NPs. In order to confirm the average energy gap of TiO2 NPs, diffused reflectance spectroscopy (DRS) via Kubelka-Monk function was applied (3.66 ​eV). Navy blue dye was used to study the photocatalytic properties of NPs and discovered to be triggered at 590.9 ​nm. The photodegradation rate of NB dye decolorized up to 74.04% after 120 ​min of UV light exposure. The first order kinetics was indicated by a linear relationship between log C/Co and k. The demonstrated rates of photodecoloration for NB under UV light in the presence of scavengers AgNO3, ethanol, and ethylenediamine tetraacetic acid (EDTA), were found to be 65.50%, 61.46%, and 57.33%, respectively. Using the carbon paste electrodes and cyclic voltammetry (CV) in 0.1 ​N HCl solution, the electrochemical characteristics of the obtained sample were studied. The carboxymethyl cellulose sensor made from TiO2 NPs demonstrated a remarkable sensitivity of 0.08 A. The results showed a high recovery for lead with low% of RSD values. The TiO2 electrode is a promising electrode material for sensing applications due to its outstanding electrochemical performance.

Rack-gear structures in columnar liquid crystal phases of trialkoxybenzyl pentafluorobenzoates and their influences on intercolumnar interdigitation and macroscopic morphologies

ABSTRACT In this study, 3,4,5-trialkoxybenzyl pentafluorbenzoates with alkyl chains of various lengths were synthesised, and the phase transition behaviours, liquid crystallinities, and molecular packing structures of their columnar phases were investigated. The results showed that discs comprising two half-discoid molecules stack up to form columns with rack-gear structures, generating columnar liquid crystal phases. From powder and single crystal X-ray diffraction investigation, the mechanism of the self-assembly of molecules into columns and their intercolumnar interdigitation was postulated. Furthermore, it was revealed that the combination of alkyl groups of the benzyl groups was closely related to the type of columnar liquid crystal phases generated and the macroscopic morphologies of the liquid crystal domains.

A multipurpose laboratory diffractometer for operando powder X-ray diffraction investigations of energy materials.

Laboratory X-ray diffractometers are among the most widespread instruments in research laboratories around the world and are commercially available in different configurations and setups from various manufacturers. Advances in detector technology and X-ray sources push the data quality of in-house diffractometers and enable the collection of time-resolved scattering data during operando experiments. Here, the design and installation of a custom-built multipurpose laboratory diffractometer for the crystallographic characterization of battery materials are reported. The instrument is based on a Huber six-circle diffractometer equipped with a molybdenum microfocus rotating anode with 2D collimated parallel-beam X-ray optics and an optional two-bounce crystal monochromator. Scattered X-rays are detected with a hybrid single-photon-counting area detector (PILATUS 300K-W). An overview of the different diffraction setups together with the main features of the beam characteristics is given. Example case studies illustrate the flexibility of the research instrument for time-resolved operando powder X-ray diffraction experiments as well as the possibility to collect higher-resolution data suitable for diffraction line-profile analysis.

A New Cu(II) Metal Complex Template with 4–tert–Butyl-Pyridinium Organic Cation: Synthesis, Structure, Hirshfeld Surface, Characterizations and Antibacterial Activity

In this paper, we report on the chemical preparation, crystal details, vibrational, optical, and thermal behavior, and antibacterial activity of a new non-centrosymmetric compound: 4-tert-butyl-pyridinium tetrachloridocuprate. X-ray diffraction analysis shows that the structure has a 3D network made up of C–H…Cl and N–H…Cl H-bonds, and [CuCl4]2− anions have a shape halfway between a tetrahedron and a square planar structure in this compound’s monoclinic system. Hirshfeld surface analysis was used to explain the nature and extent of intermolecular interactions, highlighting the importance of the H-bonds and the C–H⋯π interactions in the structure’s stabilization. Additionally, SEM/EDX experiments were conducted. The powder X-ray diffraction investigation at room temperature validated the material purity. Moreover, the different functional groups were identified using FT-IR spectroscopy. In addition, the optical properties were investigated using UV-Vis absorption. The thermal stability of (C9H14N)2[CuCl4] was performed by TGA-DTA. The bactericidal potency of the title compound was surveyed.

Hydrogen storage properties and reaction mechanisms of K2Mn(NH2)4–8LiH system

Hydrogen storage properties of K2Mn(NH2)4–8LiH were investigated by considering its de/re-hydrogenation properties and reaction mechanisms. Experimental results show that the dehydrogenated K2Mn(NH2)4–8LiH can be almost re-hydrogenated completely at 230 °C and 50 bar of H2 with a hydrogenation rate more than 1.0 wt%/min. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and FTIR investigations reveal that during ball milling K2Mn(NH2)4 reacts with LiH to form LiNH2 and K–Mn-species1 which is probably a K–Mn-containing hydride. The ball milled sample releases hydrogen in a multi-step reaction with the formation of K3MnH5 and K–Mn-species2 as intermediates and Li2NH, Mn3N2 and MnN as final products. The full hydrogenated products are LiH, LiNH2, and K–Mn-species2. The K–Mn-species2 may play a critical role for the fast hydrogeneration. This work indicates that transition metal contained amide-hydride composite holds potentials for hydrogen storage.

ZnO nanoparticles prepared via a green synthesis approach: Physical properties, photocatalytic and antibacterial activity

The aqueous extract of Phoenix roebelenii palm leaves has been utilized for the first time as an effective chelating/stabilizing agent used to synthesize zinc oxide nanoparticles (ZnO NPs) via a green chemistry approach. The physical properties of the nanoparticles were examined using X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), simultaneous thermogravimetric analysis (TGA) and differential thermal analysis (DTA), photoluminescence (PL) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Our XRD investigations revealed that the ZnO NPs have a single phase wurtzite structure with P63mc space group. The crystallite size and lattice strain were calculated using X-ray peak broadening analysis utilizing the Williamson-Hall (W-H) method and were found to be 15.6 nm and 2.1 × 10−3 respectively. The shape of the ZnO NPs was almost spherical, as revealed by TEM analysis. The DRS spectrum showed a direct band gap energy of 3.24 eV. DTA/TGA indicated that the required calcination temperature was 500°C in order to form stable ZnO NPs. PL spectroscopy revealed the presence of weak UV emission related to the free exciton and wide visible-light emission due to oxygen vacancies and other structural defects. The reaction between P. roebelenii palm leaves extract and the zinc precursor was monitored using FTIR spectroscopy at different reaction times. The potential mechanism for the formation of the ZnO NPs using P. roebelenii leaves extract as a natural chelating and stabilizing agent has been discussed. The bioinspired ZnO NPs achieved an outstanding degradation activity of 98% toward methylene blue (MB) dye after 105 min of UV illumination. In addition, the ZnO NPs exhibit a significant bactericidal effect towards gram-positive (Staphylococcus aureus and Streptococcus pneumoniae) and gram-negative (Escherichia coli and Salmonella typhi) pathogenic bacteria.

The ternary phase diagram Sb-Sn-Ti

The ternary intermetallic compound SbSnTi is known for a reversible uptake of Li at low potentials versus pure Li and is therefore a candidate as anode material for use in Li-ion batteries (LiBs). Up to now, no phase diagram data for the ternary Sb-Sn-Ti system have been reported in literature, which is, however, crucial for the understanding of the lithiation process. In this work isothermal sections of this system at 600 °C, 800 °C and 1000 °C were acquired for the first time. They are based on powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM/EDX) investigations of alloy samples. During our investigations two new ternary phases, SbxSn19-xTi15 and (SbxSn1-x)3-yTi5+y, were recognized from PXRD patterns; the crystal structures were subsequently determined by single-crystal X-ray diffraction. SbxSn19-xTi15 crystallizes with the cubic space group Pm-3 (No. 200), the lattice parameter is a = 8.8502 Å. (SbxSn1-x)3-yTi5+y shows tetragonal symmetry with the lattice parameters a = 10.553 Å and c = 5.3982 Å and the space group I4/mcm (No. 140). A further ternary compound, Sb4SnTi5, could be identified; its incommensurate crystal structure could not yet be fully described.

Structural Insights into the Vapochromic Behavior of Pt- and Pd-Based Compounds

Anionic complexes having vapochromic behavior are investigated: [K(H2O)][M(ppy)(CN)2], [K(H2O)][M(bzq)(CN)2], and [Li(H2O)n][Pt(bzq)(CN)2], where ppy = 2-phenylpyridinate, bzq = 7,8-benzoquinolate, and M = Pt(II) or Pd(II). These hydrated potassium/lithium salts exhibit a change in color upon being heated to 380 K, and they transform back into the original color upon absorption of water molecules from the environment. The challenging characterization of their structure in the vapochromic transition has been carried out by combining several experimental techniques, despite the availability of partially ordered and/or impure crystalline material. Room-temperature single-crystal and powder X-ray diffraction investigation revealed that [K(H2O)][Pt(ppy)(CN)2] crystallizes in the Pbca space group and is isostructural to [K(H2O)][Pd(ppy)(CN)2]. Variable-temperature powder X-ray diffraction allowed the color transition to be related to changes in the diffraction pattern and the decrease in sample crystallinity. Water loss, monitored by thermogravimetric analysis, occurs in two stages, well separated for potassium Pt compounds and strongly overlapped for potassium Pd compounds. The local structure of potassium compounds was monitored by in situ pair distribution function (PDF) measurements, which highlighted changes in the intermolecular distances due to a rearrangement of the crystal packing upon vapochromic transition. A reaction coordinate describing the structural changes was extracted for each compound by multivariate analysis applied to PDF data. It contributed to the study of the kinetics of the structural changes related to the vapochromic transition, revealing its dependence on the transition metal ion. Instead, the ligand influences the critical temperature, higher for ppy than for bzq, and the inclination of the molecular planes with respect to the unit cell planes, higher for bzq than for ppy. The first stage of water loss triggers a unit cell contraction, determined by the increase in the b axis length and the decrease in the a (for ppy) or c (for bzq) axis lengths. Consequent interplane distance variations and in-plane roto-translations weaken the π-stacking of the room-temperature structure and modify the distances and angles of Pt(II)/Pd(II) chains. The curve describing the intermolecular Pt(II)/Pd(II) distances as a function of temperature, validated by X-ray absorption spectroscopy, was found to reproduce the coordinate reaction determined by the model-free analysis.