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Four bimetallic phases of the thiophosphate family have been synthesized by the cationic exchange reaction using a freshly prepared K0.5Cd0.75PS3 precursor phase and methanolic solutions of nitrates of the divalent cations ZnII, NiII, CoII, and MnII. All the materials were characterized by FTIR, PXRD, SEM-EDXS and (in the case of the diamagnetic compounds) by solid state NMR. For the K0.5Cd0.75PS3 precursor, the X-ray powder diffraction data suggest a modification of the structure, while solid state NMR results confirm that this phase possesses an ordered arrangement of Cd vacancies. The cationic exchange reaction achieves a complete removal of potassium ions (no potassium detected by SEM-EDXS) and re-occupation of the vacancies by divalent cations. Therefore, the obtained compounds have an average composition of M0.25Cd0.75PS3 (M = ZnII, NiII, CoII, MnII) and possess an ordered distribution of the substituent cations. Even with the paramagnetic substitution level of 25%, antiferromagnetic behaviour is present in the phases with MnII, CoII and NiII, as evidenced by dc susceptibility and in the case of the MnII substituted phase by EPR. The cooperative magnetic interactions confirm the conclusion that the paramagnetic ions adopt an ordered arrangement. The analysis by broad band impedance spectroscopy allows to attribute the conductivity in these materials to charge movements in the layers due to the difference in electronegativity of the metal ions. Zn0.25Cd0.75PS3 is the phase that shows the highest conductivity values. Finally, the band gap energies of the bimetallic phases tend to be lower than those of the single-metal phases, probably due to an overlap of the band structures. [ABSTRACT FROM AUTHOR]

Glass structure and fluorine motion dynamics are investigated in lead-cadmium fluorgermanate glasses by means of differential scanning calorimetry, Raman scattering, x-ray absorption (EXAFS), electrical conductivity (EC), and 19F nuclear magnetic resonance (NMR) techniques. Glasses with composition 60PbGeO3-xPbF2-yCdF2 (in mol%), with x+y=40 and x=10, 20, 30, 40, are studied. Addition of metal fluorides to the base PbGeO3 glass leads to a decrease of the glass transition temperature (Tg) and to an enhancement of the ionic conductivity properties. Raman and EXAFS data analysis suggest that metagermanate chains form the basic structural feature of these glasses. The NMR study leads to the conclusion that the F-F distances are similar to those found in pure crystalline phases. Experimental results suggest the existence of a heterogeneous glass structure at the molecular scale, which can be described by fluorine rich regions permeating the metagermanate chains. The temperature dependence of the NMR line shapes and relaxation times exhibits the qualitative and quantitative features associated with the high fluorine mobility in these systems. [ABSTRACT FROM AUTHOR]

The present paper focuses on the results obtained from impedance spectros-copy, thermal analysis (DSC and DMA) and electron paramagnetic resonance (EPR) of membranes of DNA plasticized with glycerol and containing either poly(cthylene dioxylhiophcne) (PEDOT) or Prussian Blue (PB) and copper perehlorale (CuClO4). The ionic conductivity values for the DNA-PEDOT-CuClO4 and DNA-PB-CuClO4 of 4.8x10-4 S/cm and 2.2x10-4 S/cm at 30 °C, respectively, were obtained. The DSC analysis of the samples showed two glass transition temperatures at about -80 and 50 °C and DMA a permanent deformation above 50 °C ascribed to a transition between elastic and plastic states. The EPR spectra evidenced that Cu2+ ions are in tetragonally distorted octahedral sites and the quantitative analysis of the EPR spin Hamiltonian g|| and A|| parameters revealed copper ions complexed by nitrogen and oxygen atoms. All these results suggest that DNA-biomembrancs are interesting materials to be used in materials engineering science. [ABSTRACT FROM AUTHOR]

In this work the magnetic properties of bimetallic phases M′0.2Mn0.8PS3·0.25H2O (M′ = CoII, NiII, CuII or ZnII) have been explored and compared with those of the pristine phase MnPS3. Magnetic susceptibility, high field magnetization and electron paramagnetic resonance (EPR) studies reveal that the transition temperature between the antiferromagnetic and paramagnetic order for the pristine phase is shifted to lower values in the bimetallic phases. From magnetization measurements the critical field of the spin-flop transition is found to be dependent on the nature of the added secondary transition metal ion. EPR spectra of all compounds in the temperature range of 8–300 K present a single resonance line shape. Temperature dependence of the EPR parameters, like line width, g values and double integrated area (IDIN), are obtained from the spectra and present a scenario compatible with the magnetization results. The temperature dependence of the first derivative of the product (IDINT) shows two maxima for all samples, with exception of the CoII phase, indicating two critical temperatures, while these critical temperatures could not be clearly determined by dc susceptibility. [ABSTRACT FROM AUTHOR]

Measurements of 1 H and 13 C Nuclear Magnetic Resonance (NMR) for the nanocomposite materials formed by the intercalation of hexadecylamine (HAD) in metal oxides (TiO 2 , V 2 O 5 , CrO 3 and MoO 3 ), are reported. The 1 H NMR relaxation results reflects the complexity of the chain segments motions in these systems. The proton (and the carbon) mobility depends on the position in the HDA hydrocarbon chain to the restriction imposed by the anchoring of the head group. The nonexponential behavior of the proton magnetization is clearly a result of the anisotropic motion of the HDA chains. For most of the protons, the rate of motion is not fast enough to fulfill the condition for the nuclear spin-lattice relaxation (NSR) maximum in the laboratory frame but they fulfill the condition for the NSR in the rotating frame. The maximum at around 280 K reflects the relative lower mobility of the protons of the HDA chain inside the low-dimensional space of the metal oxide. The description of the segmental motion of long chains require the use of an asymmetric distribution of correlation times to describe relaxation in flexible polymer chains. [ABSTRACT FROM AUTHOR]

This work describes an Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) study of the vanadium pentoxide xerogel V 2 O 5 :nH 2 O with n ˜ 1.8 Experiments were performed in the temperature range 65 K–310 K. The EPR spectrum at high temperatures exhibits the typical liquid-like eight lines-hyperfine structure. At low temperatures the EPR spectrum change to a V 4+ anisotropic powder spectra. These two different regimes can be delimited by a transition temperature region centered at 280 K. Numerical simulations of the EPR spectra in the two temperature limits are in good agreement with the experimental data. Proton ( 1 H) NMR lineshapes, as functions of temperature were measured in the range 150–323 K and indicate that nuclear motional narrowing is effective at temperatures above 210 K, with an activation energy of 0.14 eV. The NMR spin-lattice relaxation recovery, associated to protons in the water molecules, was found to be non-exponential throughout the temperature range and described by two different relaxation processes. The slow relaxing component is temperature-independent and was attributed to water molecules located far from V 4+ ions. The temperature dependence of the fast relaxing component shows maximum at around 260 K, suggesting a relaxation process sensitive to the temperature induced dynamic structural changes in the vanadium oxide matrix. [ABSTRACT FROM AUTHOR]

Photocatalytic methods have been popular in energy production and environmental remediation. Designing high-efficiency photocatalysts is still challenging in converting solar energy into chemical fuels. Herein, a series of surfactant-assisted ZnIn2S4 (ZIS) photocatalysts were synthesized by utilizing the one-pot hydrothermal method. Photocatalytic methane production from an acetic acid solution was carried out under LED light (450 nm) irradiation, and the evolved gas was analyzed by the GC-FID system. Reaction factors (surfactant amount, catalyst dose, reaction temperature, substrate concentration, and reaction pH) were optimized for photocatalytic production. With the increase in cetyltrimethylammonium bromide (CTAB) amount, CH4 production gradually increased. The ZIS-3.75 photocatalyst exhibited the highest photocatalytic CH4 production rate (0.102 µmol g−1·h−1), which was approximately 1.8 times better than that of pure ZIS (0.058 µmol g−1·h−1). The presence of CTAB reduced the charge transfer resistance and improved photocurrent response efficiency. Structure and morphology were characterized by XRD, FTIR, SEM, TEM, and N2 adsorption–desorption isotherm analysis. Optical properties were investigated by UV-DRS and PL spectroscopic techniques. The electrochemical evaluation was measured through EIS, Mott–Schottky, and transient photocurrent response analysis. The CTAB-modified catalyst showed excellent stability and reusability, even after five irradiation cycles. Methane production was enhanced by lowering the photogenerated charge transfer resistance and boosting the dispersion of ZIS-3.75 under visible light (450 nm) irradiation. [ABSTRACT FROM AUTHOR]

Eu3+-doped glasses with composition 50ZnO.40B2O3.5WO3.5Nb2O5.xEu2O3 (x=0, 0·1, 0·5, 1, 2, 5 and 10) were prepared by the melt quenching method, and were studied by Raman, infrared, optical transmission and photoluminescence spectroscopies. Their physical properties (molar volume, oxygen molar volume, oxygen packing density, glass transitions and glass crystallisation temperature) were determined using the results of differential thermal analysis (DTA) and density measurements. Raman and infrared spectra revealed that the glass network consists of [WO4]2- and [NbO4]3- tetrahedral units, NbO6 octahedra, [BØ2O]- and [BØ4]- metaborate groups, and [B2O5]4- pyroborate dimers, varying in number with the Eu2O3 content. The physical parameters and the spectral data evidenced a highly crosslinked and connected network of the host glass 50ZnO.40B2O3.5WO3.5Nb2O5, that is very suitable for incorporating the active Eu3+ ions. The glass structure strengthens and becomes more distorted with Eu2O3 doping. A double glass transition effect observed in the DTA curves of glasses having x=5 and 10 is evidence of an increasing phase separation tendency with Eu2O3 addition. The obtained glasses have high transparency of 70-90%, and show strong red luminescence at 613 nm with excitation at 394 nm, indicating their potential for red emission applications. [ABSTRACT FROM AUTHOR]

High mechanical strength and ionic conductivity of solid-state electrolyte (SSE) are currently conflicting targets that are very difficult to achieve. Polyethylene oxide (PEO) is one of the most common polymers adopted for SSE because of its very high ionic conductivity, but its mechanical strength is very low. This work discusses the manufacturing and testing of PEO blends using polysulfone (PSf) and Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to assess the mechanical response under microtensile testing and the ionic conductivity with electrochemical impedance spectroscopy (EIS). Mechanical tests demonstrated a beneficial effect of LiTFSI with significant increase in maximum stress and ductility measured as strain at failure. The blending of PEO and PSf showed promising conductivity values at room temperature with the 90–10 PEO-PSf composition achieving the highest value (1.06 × 10−6 S/cm) and for the 70–30 composition achieving the highest maximum stress (3.5 MPa) with a conductivity of 3.12 × 10−7 S/cm. [ABSTRACT FROM AUTHOR]

In this study, the direct intercalation of gemini ionic liquids (ILs) with different alkyl chains into the bentonite (BT) interlayer as a high-performance lubricating additive for base oil 500SN was investigated. The purpose of modifying BT with an IL is to improve the dispersion stability and lubricity of BT in lubricating oil. The dispersibility and tribological properties of IL—BT as oil-based additives for 500SN depend on the increase in interlamellar space in BT and improve as the chain length is increased. More importantly, the IL—BT nanomaterial outperforms individual BT in improving wear resistance, owing to its sheet layers were deformed and sprawled in furrows along the metal surface, thereby resulting in low surface adhesion. Because of its excellent lubrication performance, IL-modified BT is a potential candidate for the main component of drilling fluid. It can be used as a lubricating additive in oil drilling and oil well construction to reduce equipment damage and ensure the normal operation of equipments. [ABSTRACT FROM AUTHOR]

In this work, manganese was suggested to improve the durability of 50P2O5-33·33K2O-(11·11-x/2) CaO-(5·56-x/2) MgO -xMnO glasses with 0≤x≤ 2 mol%. Indeed, its effect on the glass structure, thermal properties, physicochemical properties, and in particular, dissolution behaviours have been studied. The conventional melt-quenching technique was used to produce glasses at 1000°C and they were characterised by differential thermal analysis, density and molar volume measurements, x-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. Dissolution behaviours were tracked by measuring weight loss and pH. Molar volume measurements showed that phosphate glasses become more compact by incorporating MnO. Structural characterisation using Raman and infrared spectra proved that the glass network is composed mainly of metaphosphate chains. The dissolution results showed that incorporating manganese was an effective method to change the phosphate glasses' chemical durability due to their ionic crosslinking between the nonbridging oxygen atoms of the phosphate chains, corresponding to the change in thermal properties (Tg, Tc and Tf). [ABSTRACT FROM AUTHOR]

Design of prototype for a solid-state lithium battery with LiFePO4 cathode and nanocomposite polymer gel electrolyte is developed. The concept of an asymmetric solid-state electrolyte was used for better compatibility of the solid electrolyte/electrode interface. According to the concept, a silica-nanoparticle-based transition layer is used facing the lithium anode; a liquid electrolyte layer; facing the cathode. The composition of the liquid electrolyte is optimized. 1 M lithium bis-trifluoromethanesulfonyl imide solution in a dioxolane/dimethoxyethane mixture (2 : 1) is shown to be the best electrolyte for the forming of a transition ion-conducting layer between the nanocomposite polymer gel electrolyte and the LiFePO4 cathode; 1 M LiBF4 in gamma-butyrolactonee, for the synthesis of a cross-linked polymer gel electrolyte, as an inert liquid medium for the radical-polymerization reaction. Comparative tests of Li/LiFePO4 battery prototypes showed the maximal capacity of the LiFePO4 cathode to be as large as 170 mA h g–1 when using a nanocomposite polymer gel electrolyte based on polyethylene glycol diacrylate with 6 wt % SiO2 with asymmetric interface. [ABSTRACT FROM AUTHOR]

The desire to harness solar energy to address current global environmental problems led us to investigate two-dimensional (2D) core–shell hybrid photocatalysts in the form of a 2D-TiO2–surfactant, mainly composed of fatty acids. The bulk products, prepared by two slightly different methods, consist of stacked host–guest hybrid sheets held together by van der Waals forces between alkyl carboxylate moieties, favoring the synergistic conjugation of the photophysical properties of the core and the hydrophobicity of the self-assembled surfactant monolayer of the shell. X-ray diffraction and the vibrational characteristics of the products revealed the influence of synthesis strategies on two types of supramolecular aggregates that differ in the core chemical structure, guest conformers of alkyl surfactant tails and type, and the bilayer and monolayer of the structure of nanocomposites. The singular ability of the TiO2 core to anchor carboxylate leads to commensurate hybrids, in contrast to both layered clay and layered double-hydroxide-based ion exchangers which have been previously reported, making them potentially interesting for modeling the role of fatty acids and lipids in bio-systems. The optical properties and photocatalytic activity of the products, mainly in composites with smaller bandgap semiconductors, are qualitatively similar to those of nanostructured TiO2 but improve their photoresponse due to bandgap shifts and the extreme aspect-ratio characteristics of two-dimensional TiO2 confinement. These results could be seen as a proof-of-concept of the potential of these materials to create custom-designed 2D-TiO2–surfactant supramolecular photocatalysts. [ABSTRACT FROM AUTHOR]

The structure of glass with a chemical composition of 15AlPO4.40AlF3.35CaF2.10BaF2 was studied among various fluorophosphates glasses. Structural analyses of the glass were performed using Raman scattering spectroscopy, 27Al and 31P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy, total correlation function derived from x-ray diffraction measurements and classical molecular dynamics simulations. By optimising the parameters of the Born-Mayer potentials used in the simulations, a structural model, which reproduced the total correlation function and satisfied the structural information obtained using the Raman and NMR spectra, was obtained. The coordination number of Al atoms in the structural model was approximately six. One O atom and five F atoms were present in the average coordination polyhedron. Almost all O atoms were bonded to P atoms, and the tetrahedral PO4 units were bonded to three or four Al atoms. A P-O-Al oxide network and fluoride glass primarily composed of AlF3 were connected to an Al coordination polyhedron containing O and F atoms in the glass network structure. [ABSTRACT FROM AUTHOR]

Featured Application: A review of epoxide-based solid polymer electrolytes for use in all-solid-state batteries. Solid polymer electrolytes have been widely proposed for use in all solid-state lithium batteries. Advantages of polymer electrolytes over liquid and ceramic electrolytes include their flexibility, tunability and easy processability. An additional benefit of using some types of polymers for electrolytes is that they can be processed without the use of solvents. An example of polymers that are compatible with solvent-free processing is epoxide-containing precursors that can form films via the lithium salt-catalyzed epoxide ring opening polymerization reaction. Many polymers with epoxide functional groups are liquid under ambient conditions and can be used to directly dissolve lithium salts, allowing the reaction to be performed in a single reaction vessel under mild conditions. The existence of a variety of epoxide-containing polymers opens the possibility for significant customization of the resultant films. This review discusses several varieties of epoxide-based polymer electrolytes (polyethylene, silicone-based, amine and plasticizer-containing) and to compare them based on their thermal and electrochemical properties. [ABSTRACT FROM AUTHOR]

Potassium fluorogermanate glasses have been formed in the compositional range from zero to 30 mol% K2F2. The densities, molar volumes, refractive indices, thermal expansion coefficients, glass transformation temperatures, and d.c. electrical conductivities of these glasses are compared to those of the corresponding potassium germanate glasses. While the general property trends are similar for these two series of glasses, the magnitude of several properties are altered by the replacement of oxygen by fluorine, as are the compositions where the anomalies in the properties occur. The changes in properties are discussed in terms of possible changes in the glass structure due to replacement of oxygen by fluorine in the glass network. [ABSTRACT FROM AUTHOR]