The first synthesis of a graphite bis(oxalato)borate intercalation compound

A new graphite intercalation compound containing the bis(oxalato)borate anion, B[OC(O)C(O)O]₂⁻, is prepared for the first time by chemical oxidation of graphite with fluorine gas in the presence of a solution containing the intercalate anion in anhydrous hydrofluoric acid. The products of stage 1-3 compounds are characterized by powder X-ray diffraction, thermogravimetric analysis, and elemental analyses. X-ray diffraction data indicate a standing-up orientation for the borate anion, with long axis perpendicular to the graphene sheets. Elemental analyses provide x and δ for the nominal composition of C_xB[OC(O)C(O)O]₂·δF, where the chelate borate and fluoride are co-intercalates, and indicate a low borate, and high fluoride, intercalate content as compared to anion packing in other graphite intercalation compounds.     

A study on the effect of melt-intercalation of PEO in HNbWO6

Polyethylene oxide (PEO) has been introduced into HNbWO₆·1.5H₂O using melt-intercalation technique and its effect on the structure and properties of the host material studied using powder X-ray diffraction, FT-IR, impedance spectroscopy and TGA/DTA measurements. The intercalation reaction leads to loss of stacking coherence along the c-axis of the host layered material, as evidenced by the XRD data. FT-IR spectra of the nanocomposite show changes, indicative of complexing of the guest polymer with the host layered structure. TGA/DTA isothermal profiles exhibit marked changes upon prolonged periods of intercalation. The conductivity of the nanocomposite is found to be about 2×10⁻⁶ S/cm.     

Metatungstate and tungstoniobate-containing LDHs: Preparation, characterisation and activity in epoxidation of cyclooctene

Polyoxometalates (POMs) H₂W₁₂O₄₀⁶⁻ and W₄Nb₂O₁₉⁴⁻ have been intercalated between the brucite-like layers of Mg, Al and Zn, Al hydrotalcites by anion exchange, starting from the corresponding nitrate precursors. The solids have been characterised by Powder X-ray Diffraction (PXRD), Fourier Transform infrared (FT-IR) spectroscopy, N₂ adsorption-desorption at −196 °C and thermogravimetric (TG) and differential thermal analyses (DTA), and have been tested in the epoxidation of cyclooctene using H₂O₂ or t-BuOOH as oxidants. The results show that both anions are effectively located in the interlayer space maintaining their pristine structures without depolymerisation. Upon intercalation of such large anions microporosity is developed and subsequently an increase in the specific surface areas is also observed. In general, the prepared materials possess catalase and epoxidation activity, with ZnAl-intercalated H₂W₁₂O₄₀⁶⁻ giving the best results in terms of epoxide yield (17% at 24 h). Product selectivity is different for the intercalated and free POMs, the latter yielding 1,2-cyclooctanediol as the only product, whereas the former produces only the epoxide. The epoxidation reaction seems to be catalysed in homogeneous phase by the POM.     

Intercalation behavior of barium phenylphosphonate

The dependence of basal spacing and water content of BaC₆H₅PO₃·xH₂O on the relative humidity was studied. Intercalates of 1-alkylamines (C₂-C₁₀) and 1-alkanols (C₃-C₁₀) were prepared from barium phenylphosphonate dihydrate and also from anhydrous host and characterized by powder X-ray diffraction and thermogravimetric analysis. The intercalates of alkanols and alkylamines prepared from dihydrate are quite stable at ambient conditions and contain one guest molecule per formula unit. The guest molecules are probably arranged in monomolecular way and are perpendicular to the host layers in the case of amines or tilted to the host layers at an angle of about 80° in the case of alkanols. The intercalates prepared from anhydrous host are unstable and their basal spacings indicate parallel arrangement of the guests chains. Formation of mixed intercalates was not observed when barium phenylphosphonate dihydrate was contacted with a mixture of alkanols or amines.     

Intercalation of sulfonated melamine formaldehyde polycondensates into a hydrocalumite LDH structure

A series of sulfonated melamine formaldehyde (SMF) polycondensates possessing different anionic charge amounts and molecular weights was synthesized and incorporated into a hydrocalumite type layered double hydroxide structure using the rehydration method. For this purpose, tricalcium aluminate was dispersed in water and hydrated in the presence of these polymers. Defined inorganic–organic hybrid materials were obtained as reaction products. All SMF polymers tested intercalated readily into the hydrocalumite structure, independent of their different molecular weights (chain lengths) and anionic charge amounts. X-ray diffraction revealed typical patterns for weakly ordered, highly polymer loaded LDH materials which was confirmed via elemental analysis and thermogravimetry. IR spectroscopy suggests that the SMF polymers are interleaved between the [Ca₂Al(OH)₆]⁺ main sheets via electrostatic interaction, and that no chemical bond between the host matrix and the guest anion is formed. The SMF polymers well ensconced within the LDH structure exhibit significantly slower thermal degradation.     

Temperature effect on the sorption of cholate anions on calcined LDH

Layered Double Hydroxides are a class of materials that can be described as positively charged layers of divalent and trivalent cations in the centre of edge-sharing octahedra. Cholesterol derivatives such as cholic acid are substances that play an important role in the digestion of fat components by the organism. This work presents a study on the intercalation of cholate anions in calcined MgAl-CO₃-HDL. Isotherm experiments were performed at three different temperatures to evaluate the capacity of anion removal by sorption in the calcined LDH. The plateau was reached in all conditions. Increasing temperature results in decreasing cholate sorption. Characteristic peaks of LDH regenerated with OH⁻ anions were observed at lower cholate concentrations. A peak in 2θ equals to 7.5° and peaks between 15° and 20° are observed. Those peaks are the same as the ones observed in the pure sodium cholate PXRD. At higher cholate concentrations the sorbed solids present PXRD related to an additional layered phase, which is related to intercalation of cholate anions with basal spacing equal to 34.3 Å. Thus, the cholate anions are also intercalated with a bilayer molecular arrangement at equilibrium concentrations at the isotherms plateau.     

Two different synthetic routes involving the reaction of dodecylamine or nicotinamide with crystalline lamellar vanadylphosphate

The crystalline lamellar compound, VOPO₄·2H₂O, was employed as host to react with a long monoamine aliphatic chain, dodecylamine, and with an aromatic derivative, nicotinamide, using two distinct synthetic approaches: in the solid state and from aqueous solution. The resulting compounds were characterized by elemental analysis, infrared spectroscopy, X-ray diffractometry, thermogravimetry and SEM microscopy. From X-ray diffraction patterns, the calculated increase of the interlayer distance was 2.05 nm for the dodecylamine, containing product, which is in agreement with the intercalation process, and was observed with both reactions routes. On the contrary, the guest nicotinamide molecule was not inserted into the lamellar cavity. The reaction in the solid state caused a small modification of the phosphate microstructure, in comparison with the solution procedure. The aliphatic amine molecules are oriented in a bilayer inside the host cavity by forming an angle of 67° with the inorganic lamella. The thermal decomposition for both series of synthesized compounds did not demonstrate any difference in behavior.     

Crystal structure and cation distribution in the solid solution series 2(ZnX)-CuInX2 (X=S, Se, Te)

The solid solution series (2ZnX)_x (CuInX₂)_1−x (X=S, Se, Te) were studied by the combination of laboratory and synchrotron X-ray and by neutron powder diffraction. Within the homologous series the tetragonal distortion ¼-u increases in the sequence S→Se→Te whereas the tetragonal deformation η=c/2a decreases. Besides that, with increasing 2ZnX content in CuInX₂ the anion position parameter u increases as expected. The cation site occupancy in the chalcopyrite type phase of single phase tetragonal samples was obtained by Rietveld analysis of the neutron diffraction data. A non-statistic Zn distribution could be deduced for all three systems. The high temperature in situ diffraction experiments with synchrotron radiation on CuInX₂ powder samples revealed the Cu-In anti-site occupation as the driving force of the temperature dependent phase transition from the chalcopyrite to the zinc-blende type structure.     

Structural, sorption and thermodynamic correlations from a layered barium phenylarsonate/n-alkyldiamine system

The barium phenylarsonate compound, Ba(HO₃AsC₆H₅)₂·2H₂O, has the ability to intercalate n-alkyldiamine molecules, H₂N(CH₂)_nNH₂ (n=2-5). The amount intercalated (n_f) from a batchwise procedure and the variation of the original basal distance (d) of 1245 ppm determined through X-ray diffractions, gave linear correlations as a function of the number of carbon atoms in the aliphatic chain (n_c): n_f=(2.66±0.06)−(0.13±0.02)n_c and d=(2168±65)+(114±14)n_c. The intercalation process was calorimetrically followed to give exothermic enthalpy and negative Gibbs energy, reflecting spontaneous intercalation reactions at the solid/liquid interface. The displacement of solvent molecules bonded to amine and of those on the matrix during the intercalation increases the disorder to result in positive entropy, giving a favorable set of thermodynamic data for this system.     

Layered double hydroxide: Inorganic organic conjugate nanocarrier for methotrexate

Layered double hydroxide (LDH)-methotrexate (MTX) nanohybrids were successfully synthesized using ex situ and in situ processes. X-ray diffraction patterns of the synthesized nanopowders revealed that intercalated MTX molecules were stabilized in tilted longitudinal conformation into the hydroxide interlayer space. Two separate hydroxyl peaks were found in the FTIR spectra of LDH-MTX nanopowders suggesting successful intercalation of the MTX molecule into LDH matrix. The synthesized powders were further characterized using transmission electron microscopy (TEM) and selected area electron diffraction (SAED) pattern. HRTEM images showed an increase in interlayer spacing in hydrothermally crystallized LDH-MTX nanohybrids as compared to pristine LDH. The study showed that depending on the synthesis route used to synthesize LDH-MTX nanohybrid, its particle size as well as morphology can be varied at nano scale.     

Supramolecular structural control and characteristics of p-hydroxybenzoate intercalated hydrotalcite

p-Hydroxybenzoate pillared layered double hydroxides with different Zn/Al mole ratios have been prepared by three different methods: rehydration of calcined LDH precursor, coprecipitation and anion exchange. The products have been characterized by several experimental techniques: PXRD, FT-IR, TG-DTA and UV-vis. PXRD patterns show that the interlayer distance of p-hydroxybenzoic acid (PHBA)-Zn/Al-LDH varies with ratio Zn/Al, from 14.8 to 15.3 Å, indicating that altering Zn/Al ratios can change the arrangement of the intercalated PHBA anions. Not only do infrared spectra display the characteristic absorption of both the PHBA anion and the Zn/Al layer, but also provide further evidence of the interaction between these two parts. Thermal analysis confirms that the intercalation can make PHBA stable up to 434 °C, which is 213 °C higher than that for pure PHBA. By UV-vis it is found that such a product can control blocking of UV radiation in a wider range of wavelength.     

In situ energy dispersive X-ray diffraction study of iron disilicide thermoelectric materials

The dynamic phase transformation and structure of rapidly solidified Fe_1−xCo_xSi₂ (0.02?x?0.06) thermoelectric materials were in situ investigated under high temperatures and high pressures by energy dispersive X-ray diffraction using synchrotron radiation. The FeSi₂ alloys which solidified as α-Fe₂Si₅ and ε-FeSi eutectic structures, were transformed to the semiconducting β-FeSi₂ phase upon heating by the main reaction α+ε→β and the subsidiary reaction α→β+Si. The low heating rates and Co contents were found to be beneficial for the β phase formation. The decomposition temperature of β→α+ε was weakly dependent on heating rate, but significantly suppressed by the high pressures.     

Improving the visible light photocatalytic activity of mesoporous TiO2 via the synergetic effects of B doping and Ag loading

B-doped together with Ag-loaded mesoporous TiO₂ (Ag/B–TiO₂) was prepared by a two-step hydrothermal method in the presence of boric acid, triblock copolymer surfactant, and silver nitrate, followed by heat treatment. The obtained samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption. It was revealed that all samples consist of highly crystalline anatase with mesoporous structure. For Ag/B–TiO₂, B was doped into TiO₂ matrix in the form of both interstitial B and substitutional B while Ag was deposited on the surface of B–TiO₂ in the form of metallic silver. Compared with the single B-doped or Ag-loaded TiO₂ one, mesoporous Ag/B–TiO₂ exhibits much higher visible light photocatalytic activity for the degradation of Rhodamine 6G, which can be ascribed to the synergistic effects of B doping and Ag loading by narrowing the band gap of the photocatalyst and preventing the fast recombination of the photogenerated charge carriers, respectively.     

X-ray diffraction studies of intercalation compounds prepared from aniline salts and montmorillonite by a mechanochemical processing

Inorganic-organic intercalation compounds comprised of montmorillonite (MMT) and aniline salts with different counter anions were prepared by a mechanochemical processing. The intercalation process and the formed structure of intercalation compounds were investigated via X-ray diffraction analysis. The amounts of intercalated species were very likely dependent on the types of counter anions and increased with decreasing the size of counter anions during the mechanochemical processing. Very interestingly, much larger interlayer expansions of 1.51 nm was observed for aniline hydrofluoride AnF- and aniline hydrochloride AnCl-MMT systems in higher intercalates loading levels, suggesting that neutral guest molecules also introduce within the interlayer regions together with anilinium cations by van der Waals interactions. Judging from the larger interlayer expansions and the size of guest molecules, intercalated species are expected to prefer a tri-molecular layer arrangement with their aromatic rings perpendicular to the silicate sheets. In contrast, for aniline hydrobromide AnBr-MMT, the interlayer expansion was ca. 0.52 nm, which reveals that only anilinium cations are introduced by ion exchange and they probably adopt a vertical orientation in the interlayers. It is inferred that aniline hydroiodide AnI-MMT compounds have a heterogeneous structure containing both anilinium and sodium cations in the interlayers. Different intercalation behaviors during the mechanochemical processing strongly suggest the smaller the size of counter anions, the more guest molecules can be intercalated into the confined clay interlayers in highly ordered arrangements.     

Preparation of graphene encapsulated copper nanoparticles from CuCl2-GIC

Graphene encapsulated metallic copper nanoparticle composite was prepared by reduction of stage-2 CuCl₂-graphite intercalation compounds, using both metallic potassium and potassium borohydride/ethylenediamine matrix as reducing reagents. X-ray diffraction, high-resolution transmission electron microscopy and Raman spectroscopy were employed to characterize the reduction products. The results show that the copper nanoparticles in the graphite matrix are 30 to 70 nm in size. The copper concentration in the reduction product is experimental-condition dependant. A severe structure disorder of graphitic carbon occurs during the reduction procedure. The formation procedure of copper particles in the graphene sheets is discussed briefly.     

Determination of the crystal structure of U6Fe5Al8Si9 by electron crystallography

The crystal structure of U₆Fe₅Al₈Si₉ was re-determined by electron crystallography, using selected area electron diffraction (SAED) and high resolution (HRTEM) images, taken along the [0 0 1] direction. The obtained results are very similar to those found previously by X-ray powder diffraction. The differences between the atomic positions found by SAED and HRTEM images and those found by X-ray powder diffraction were 0.11 and 0.08 Å, respectively.     

Neutron and X-ray diffraction studies on the Tb2Ni3Si5 single crystal

Neutron and X-ray diffraction studies on the Tb₂Ni₃Si₅ single crystal have been done to investigate its crystal modulation and magnetic properties. The modulated single crystal is constructed by the TbNiSi₂ (CeNiSi₂-type Cmcm) and the Tb₂Ni₃Si₅ (U₂Co₃Si₅-type Ibam) lattices. The relationship between the two lattices is described as direction of the b₁₁₂-axis coincides with the a₂₃₅-axis. The crystal modulation gives significant effects on magnetism. Each of the two lattices takes complex antiferromagnetism with multiplex propagation vectors.     

Optical and thermoelectric characterizations of electroplated n-Bi2(Te0.9Se0.1)3

Bismuth selenotelluride (Bi₂(Te_0.9Se_0.1)₃) films were electrodeposited at constant current density from acidic aqueous solutions with Arabic gum in order to produce thin films for miniaturized thermoelectric devices. X-ray fluorescence spectroscopy determined film compositions. X-ray diffraction pattern shows that the films as deposited are polycrystalline, isostructural to Bi₂Te₃ and covered by crystallites. Mueller-matrix analysis reveals that the electroplated layers are optically like an isotropic medium. Their pseudo-dielectric functions were determined using mid-infrared spectroscopic ellipsometry. Tauc-Lorentz combined with Drude dispersion relations were successfully used. The energy band gap E_g was found to be about 0.15 eV. Moreover, the fundamental absorption edge was described by an indirect optical band-to-band transition. From Seebeck coefficient measurement, films exhibit n-type charge carrier and the value of thermoelectric power is about −40 μV/K.     

Intercalation of acrylate anions into the galleries of Zn–Al layered double hydroxide

Acrylate and methacrylate anions containing double bond and carboxylic groups, were intercalated in the interlayer region of a layered double hydroxide of formula: [Zn_0.66Al_0.34(OH)₂](NO₃)_0.34 0.62H₂O. The intercalation compounds obtained have been characterized for their chemical composition and with different instrumental techniques (X-ray powder diffraction, thermal analysis, FT-IR absorption spectroscopy, electron scanning microscopy). Furthermore, they have been used to carry out a preliminary study concerning the in situ polymerization of the intercalated acrylate and methacrylate ions to obtain new interstratified inorgano-organic hybrid materials.     

X-ray and AFM studies of polydisperse TiO2 (anatase) particles

Titanium dioxide (TiO₂) materials of a high chemical purity, as-prepared by the thermal hydrolysis, as well as subsequently modified by adsorption of different metal cations (Fe³⁺, Co²⁺, Cu²⁺), have been investigated by the X-ray diffraction, X-ray fluorescence and AFM microscopy methods. All TiO₂ powders have a fine-dispersated anatase structure and consist of grown together nanocrystallites of ∼8-17 nm. TiO₂ particles, usually ranging from 100 to 600 nm, show the ability to form large agglomerates, up to 2 μm in size. Contrary to the pure anatase, metal-modified TiO₂ particles possess a positive charge on their surface and can be lifted away by the AFM tip from the substrate surface during the scanning. This effect is mostly pronounced for the Fe-modified TiO₂ sample, where particles up to 250 nm are removed. The possible interaction mechanisms between different TiO₂ particles and the silicon tip are discussed. The electrostatic force has been found to play an essential role in the sample-tip interaction processes, and its value depends on the type of metal cation used.