Hexagonal-like Structure Research Articles

Effect of morphological and particle size, structure on the physical properties of Sr doped cobalt chromite for catalysis application

The structural, optical, morphological, and catalytic behavior of the spinel cobalt chromite nanoparticles (NPs), which were successfully synthesised using a simple co-precipitation method, are investigated in this work. First, the catalytic performance test was used to determine the ideal doping Sr and doping amounts. The as-prepared sample's face-centered cubic spinel structure is confirmed by the powder X-ray diffraction pattern, and the average crystallite size is determined to be 22–15 ​nm. The prepared material had a structure resembling nanoparticles, and the SEM analysis showed that the size attained was approximately 28–16 ​nm. TEM analysis revealed that the prepared material and sizes had a hexagonal-like structure. DRS and PL spectra were used to determine the optical absorption and photoluminescence emissions, respectively. Decolorization of 4-Nitrophenol's yellow color is another area of interest in the catalytic characteristics of CoCr2O4 crystals doped with Sr. The catalysts employed were discovered to be readily recyclable and effective catalysts for the oxidation of styrene, with benzaldehyde as the end product.

Photochromic performance of hydrogel based on deep eutectic solvent induced water soluble Cu-doped WO3 hybrids with antibacterial property

A novel fast photoresponse and self-fading photochromic hydrogel system was fabricated based on Cu-doped WO 3 , which prepared by employing DESs as co-solvent. The photochromic hydrogel displayed remarkable antibacterial ability and non-cytotoxicity, great potential in the applications of stimuli-responsive materials such as smart windows, repeatable erasing paper and photochromic sensors. • Deep eutectic solvents (DESs) as a green co-solvent was employed to prepare Cu-doped WO 3 photochromic materials with excellent water solubility. • The fabricated P(AM-HEA)-Cu-WO 3 -X photochromic hydrogels exhibit rapid photoresponse and enhanced self-fading rate. • The deep-blue colored P(AM-HEA)-Cu-WO 3 -25% hydrogel could come back to its original colorless state within 40 min. • The mechanism of photochromic and self-fading behaviors for P(AM-HEA)-Cu-WO 3 -X photochromic hydrogels was detailed analyzed. • The remarkable antibacterial performance and cell viability possessed in hydrogels also confirmed. A novel photochromic and self-bleaching hydrogel was prepared based on the Cu-doped tungsten oxide (WO 3 ) hybrid encapsulated in the co-polymer matrix polymerized using acrylamide (AM) and hydroxyethyl acrylate (HEA) as monomers. The Cu-WO 3 -25% hybrid was generated by introducing Cu species into the lattice of WO 3 with hexagonal-like prismatic structure and acted as light absorber. Given that WO 3 and Cu-doped WO 3 hybrids possess superior water solubility by using water and deep eutectic solvents (DESs, ChCl:EG) containing sufficient hydrogen bond as co-solvent, the high transparency of 90% of the hydrogels was achieved. As compared with P(AM-HEA)-WO 3 -based hydrogel, the P(AM-HEA)-Cu-WO 3 -X hydrogel exhibited the enhanced coloration degree under UV irradiation. The P(AM-HEA)-Cu-WO 3 -25% photochromic hydrogel changed from colorless to blue immediately once illuminated by UV light, and turns into dark-blue with the irradiation time going on. The self-bleaching process indicates it only takes 40 min for the P(AM-HEA)-Cu-WO 3 -25% hydrogel to return to the original colorless transparent state. Furthermore, the hydrogel systems exhibit efficient antibacterial activities against bacteria of both E. coli and S. aureus , accompanying with outstanding biocompatibility. As such, the fabricated hydrogel demonstrates rapid photoresponse, self-bleaching process, superior antibacterial performance, and cell viability, showing a great potential application as stimuli-responsive materials.

Assessment of Hepatic Lesions After non-Thermal Tumor Ablation by Irreversible Electroporation in a Pig Model.

Irreversible electroporation (IRE) is a non-thermal and minimal invasive modality to ablate pathologic lesions such as hepatic tumors. Histological analysis of the initial lesions after IRE can help predict ablation efficacy. We aimed to investigate the histological characteristics of early hepatic lesions after IRE application using animal models. IRE (1500 V/cm, a pulse length of 100 μs, 60 or 90 pulses) was applied to the liver of miniature pigs. H&E and TUNEL staining were performed and analyzed. Ablated zones of pig liver were discolored and separated from the normal zone after IRE. Histologic characteristics of ablation zones included preserved hepatic lobular architecture with a unique hexagonal-like structure. Apoptotic cells were detected, and sinusoidal dilatation and blood congestion were observed, but hepatic arteries and bile ducts were intact around the ablation zones. The early lesions obtained by delivering monophasic square wave pulses through needle electrodes reflected typical histological changes induced by IRE. Therefore, it was found that the histological assessment of the early hepatic lesion after IRE can be utilized to predict the IRE ablation effect.

Microwave absorption performance enhancement of NiFe2O4/GNs composite with hollow hexagonal-like structure

It is a major aspect in the field of absorbing materials to obtain composite absorbing materials with prominent absorbing properties through shape design. In this paper, a hollow hexagonal NiFe2O4/GNs composite absorbing material was prepared by a simple hydrothermal method. The test results show that the minimum reflection loss of the composite can reach −57.4 dB at the low frequency of 6.08 GHz, and the corresponding thickness is 2.9 mm; When the hydrothermal reaction temperature is 200 ℃, the maximum effective absorption bandwidth is 3.12 GHz, and the thickness is as thin as 1.1 mm. With the increase of hydrothermal reaction temperature, the morphology of nickel ferrite gradually changed from round rod to hollow hexagonal prism, and the microwave absorption characteristics of the composite also varied and adjusted. This paper provides the preparation process of NiFe2O4/GNs composites with controllable morphology, and possesses a certain reference for the study of the interaction mechanism of ferrite and graphite nanosheets composite microwave absorbing materials. In addition, the sample has excellent microwave absorption performance in the low-frequency band, while the current wave absorption band of ferrite composites is mainly in the high-frequency band, so the sample has great research and development potential in the field of low-frequency microwave absorbing materials.

Polymerized Laminin-521: A Feasible Substrate for Expanding Induced Pluripotent Stem Cells at a Low Protein Concentration.

Laminins (LNs) play a central role in the self-assembly and maintenance of basement membranes and are involved in critical interactions between cells and other extracellular matrix (ECM) proteins. Among the defined, xeno-free ECM culture matrices, LNs-namely LN521-have emerged as promising coating systems for the large-scale expansion of induced pluripotent stem cells (iPSCs). The biologic activity of LNs is enhanced by their acidification-induced self-polymerization into a cell-associated network called polylaminin (polyLN), which can recapitulate the native-like polymeric array in a cell-free system. Here, we show for the first time to our knowledge that polyLN521 displays a native-like hexagonal-like structure and that, at basal and low concentrations, it permits the large-scale expansion of human iPSCs. Human iPSCs expanded with polyLN521 maintained the pluripotent state and showed no impairment of karyotype stability or telomere length. These results suggest that low-concentration polyLN521 is a stable and cost-effective coating for large-scale iPSC expansion.

Tailoring the structural and magnetic traits of copper modified BaFe12O19 nanostructured hexaferrites for recording media application

Barium nanohexaferrites, with a chemical composition of Ba1-0.5xCu0.5xFe12O19 (x = 0.0, 0.1, 0.2, 0.3) have been successfully produced using the sol–gel auto-combustion approach for tuning its structural, morphological, optical and magnetic properties. The current work has been carried out to control the coercivity of synthesized specimens, with the modification of copper ions at the barium sites of BaFe12O19 hexaferrites. The XRD patterns of synthesized specimens’ shows the formational of hexagonal-like crystal structure with P63/mmc space geometry. In the XRD diffraction patterns, the characteristic peaks (110), (008), (107), (114), (108), (203), (205), (206), (1011), (300), (217), (2011), (220), (2014)along with some impurity phases of hematite (α-Fe2O3) were observed. The crystallite size “D” was estimated from the observed XRD patterns using the Debye-Scherrer formula in the range of 41.94–83.91 nm respectively. The FESEM studies of the BM2 and BM3 specimens reveal the presence of agglomerated grains with a hexagonal shape and an average size of ∼ 277 and ∼ 469 nm respectively. The energy dispersive X-ray spectra of synthesized nanohexaferrites shows only peaks of copper, iron, barium, and oxygen which clearly confirms the higher purity of pure and doped barium hexagonal nanoferrites. The transmission electron micrograph of BM1 nanohexaferrite illustrates the production of the nanoparticles that are agglomeratedand spherical, and have an average particle size of 53.32 nm. The Raman spectrum of undoped and copper doped BaFe12O19 hexagonal nanoferrites shows the formation of seven Raman active vibrational modes in the frequency range of 200–800 cm−1. At room temperature (300 K), the magnetic traits of the produced barium hexagonal nanoferrites were measured, and using these measurements, a variety of magnetic parameters (Ms, Hc, Mr, and Ha) were reported. The value of saturation magnetization (Ms) increases from 37.75 emu/g to 59.97 emu/g with increased low copper content up to x = 0.1. In contrast, with the increasing copper content up to x = 0.3, the value of Ms shows a decline to 28.31 emu/g. In this work, admirable values of Ms (28.31–59.97 emu/g) and Hc (684–2563 Oe) were obtained, making these nanohexaferrites as beneficial candidates for the recording media and EMI shielding applications.

A novel designed 3D multi-microhole plasma jet device driven by nanosecond pulse at atmospheric pressure

A novel designed three-dimensional (3D) multi-microhole helium plasma jet device excited by nanosecond pulse is developed in atmospheric air. Systematical investigations about the discharge characteristics are carried out to get insights into the formation mechanisms of 3D plasma jets. Results show that the 3D plasma jets originated from the branching of a single ionization wave to present a hexagonal-like structure including bottom jet (BJ) and side jets (SJ1 and SJ2). The BJ always keeps a stable performance while the SJ displays a remarkably turbulent mode. The dynamic evolution, and the propagation velocity and distance for BJ and SJ demonstrate significant differences, with a delay effect between BJ and SJ bullets propagation being observed. The optical emission spectra show that 3D jets possess a high yield of the spatial distribution of reactive species in jet plumes. The formation mechanism of 3D jets is determined by the hydrodynamic (He flow distribution) and electrical interactions (distribution of electric field force) in the discharge tube emerging from individual holes with different radial directions. The direct treatment of water using this developed underwater 3D plasma device results in the production of plasma activated water with a lower pH value, higher conductivity, and greater concentrations of reactive oxygen and nitrogen species, compared to the indirect treatment. Especially, the concentration of H2O2 can remarkably increase 141 folds from 1.43 to 202.12 μM within 5 min after the direct 3D plasma treatment. This novel-designed 3D jets-based technique is a promising platform for 3D application scenarios, especially in the case of underwater microbubble discharge, which is of great significance for water activation in emerging applications.

The influence of annealing temperature on the structure and optical properties of Gd2Zr2O7 nanostructures prepared by chemical bath deposition method

Gadolinium zirconate (Gd2Zr2O7) powders were prepared for the first time using chemical bath deposition (CBD) method. In this study, the chemical bath deposition (CBD) method was employed due to its simplicity, cheap, low temperature, versatile and it gives better homogeneity. The effect of annealing temperature (Ta) on the thermal, structural, morphological, and optical properties were investigated. Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA) showed that the material is thermally stable between 400 and 900 °C. The X-ray diffraction (XRD) results confirmed the cubic Gd2Zr2O7 phase with hexagonal ZnO secondary peaks. Scanning electron microscopy (SEM) results revealed the transformation of irregular particles to hexagonal-like structure shape with an increase in Ta. Energy dispersive x-ray spectroscopy (EDS) analysis confirmed the presence of the expected elements. Transmission electron microscopy (TEM) confirmed the nano-nature of the prepared powders. Ultraviolet-visible spectroscopy (UV-Vis) spectra showed a slightly red shift with an increase in Ta. The photoluminescence (PL) results revealed that the emission intensity and peak position in UV region highly depends on the Ta. It was also noted that both secondary peaks from hexagonal ZnO and Ta regulates the defects emission. The international illumination (CIE) color chromaticity showed that the color shifts from blue to yellow-greenish with an increase in Ta. The approach in the present study opened a new way to tune band gap and luminescence intensity of Gd2Zr2O7.

Charge storage in binder-free 2D-hexagonal CoMoO4 nanosheets as a redox active material for pseudocapacitors

Binder-free CoMoO4 hexagonal nanosheets have been directly grown on the surface of conductive carbon fabric cloth (CoMoO4@CFC) as a hybrid electrode material for pseudocapacitors (PCs) with outstanding electrochemical properties. The as-prepared CoMoO4@CFC sample was structurally and morphologically characterized using various techniques. Microstructure analysis reveals that the hexagonal like 2D structure possesses mesoporous characteristics with abundant electroactive sites as a charge storage host. The CoMoO4@CFC was evaluated as a positive electrode material for pseudocapacitors, which revealed a maximum specific capacitance of 1210 F/g at 2.5 A/g with exceptional rate capability and outstanding cycling stability of 91% after 10,000 charge/discharge cycles. The 2D mesoporous hexagonal-like structure provides improved electrolyte movement during charging/discharging process and additional active sites for redox reactions. In addition, the charge storage quantification of diffusion and capacitive charge mechanism was determined by employing Power's law, and accordingly, the CoMoO4@CFC electrode was attributed to a high capacitive charge value of (80% at rate 2.5 mV/s). Thus, this work specifies simple and cost-effective method to fabricate pseudocapacitors electrode materials with high energy density and improved cyclic life for energy storage devices.

Design of best performing hexagonal shaped Ag@CoS/rGO nanocomposite electrode material for electrochemical supercapacitor application

Abstract The mixed metal/metal sulphide (Ag@CoS) with reduced graphene oxide (rGO) nanocomposite (Ag@CoS/rGO) was synthesized for the possible electrode in supercapacitors. Ag@CoS was successfully deposited on the rGO nanosheets by hydrothermal method, implying the growth of 2D Ag and CoS-based hexagonal-like structure on the rGO framework. The synthesized nanocomposite was subjected to structural, morphological and electrochemical studies. The XRD results show that the prepared nanocomposite material exhibits a combination of hexagonal and cubic phase due to the presence of CoS and Ag phases together. The band appearing at nearly 470.33 cm−1 in FTIR spectra can be ascribed to the absorption of S–S bond in the Ag@CoS/rGO nanocomposite. The clear hexagonal structure was analysed by SEM and TEM with the grain sizes ranging from nanometer to micrometer. The electrode material exhibits excellent cyclic stability with a specific capacitance of 1580 F/g at a current density of 0.5 A/g without any loss of capacitive retention even after 1000 cycles. Based on the electrochemical performance, it can be inferred that the prepared novel nanocomposite material is very suitable for using as an electrode for electrochemical supercapacitor applications.

Microstructure evolution and mechanical properties of Ti–8Nb–2Fe-0.2O alloy with high elastic admissible strain for orthopedic implant applications

A Ti–8Nb–2Fe-0.2O (wt.%) alloy with high strength, high elastic admissible strain (δ) and low cost was designed using d-electron theory combined with electron-to-atom ratio (e/a‾) approach. Interstitial oxygen was introduced to strengthen the matrix of the alloy. The β-solution treated alloy was mainly composed of α″ martensite with internal {111}α″ type I nano-twins. The α″ martensite with hexagonal-like crystal structure caused by interstitial oxygen showed a high strength of 1.1 GPa but limited ductility. The alloy generated equiaxed fine-grained α phase embedded by β matrix via hot rolling and subsequent annealing in α + β phase field. The obtained alloy indicated a good combination of mechanical properties with ultimate tensile strength, Young’s modulus, ductility and δ value of 1029 MPa, 74 GPa, 21% tensile elongation and 1.32%, respectively. These findings demonstrate that interstitial oxygen and martensitic nano-twins can be used to strengthen the soft α″ martensite and high elastic admissible strain can be obtained by formation of equiaxed fine-grained α phase embedded by β matrix in this Ti–8Nb–2Fe-0.2O alloy for orthopedic implant.

High performance piezoresistive response of nanostructured ZnO/Ag thin films for pressure sensing applications

This work reports on the preparation and characterization of zigzag nanostructured silver (Ag) doped zinc oxide (ZnO) films in order to improve piezoresistive response for pressure sensor applications. ZnO/Ag thin films were prepared by Glancing Angle Deposition (GLAD) from a metallic zinc (Zn) target DC sputtered in Ar + O2 atmosphere. The target was customized with different amounts of Ag pellets, symmetrically distributed along the preferential erosion area.It is shown that increasing the Ag content from 0 to 36 at.% in the ZnO/Ag system leads to a decrease of the electrical resistivity from 2.95 Ω cm to 1.52 × 10−5 Ω cm. The structural characterization of the thin films shows an evolution of the preferential growth, changing from a polycrystalline ZnO hexagonal-like structure, confirmed by the presence of dominant ZnO (002) and ZnO (101) diffraction peaks, to a Ag cubic (fcc)-like structure, as evidenced by the Ag (111), (200) and (220) diffraction peaks. The values of the gauge factor show a strong contribution both from Ag as well as from the zigzag nanostructure to the piezoresistive sensitivity of the films, in particular for Ag concentrations lower than 30 at.%. The tunneling distance between pairs of Ag conductive nanoregions was calculated for the different samples and in three different deformation regions, in order to evaluate its influence on the piezoresistive sensitivity. The results show that a longer distance between Ag particles, which varies from 0.1 to 10 nm, enhances the gauge factor, which ranges from 8 ± 1 to 120 ± 3, respectively.

Removal of Pollutants in Mine Wastewater by a Non-Cytotoxic Polymeric Bioflocculant from Alcaligenes faecalis HCB2.

Bioflocculation is a physicochemical technique often employed to efficiently remove colloidal water pollutants. Consequently, in this study, a bioflocculant was produced, characterised and applied to remove pollutants in mine wastewater. The maximum flocculation activity of 92% was recorded at 30 °C, pH 9.0 when maltose and urea were used as energy sources and 72 h of fermentation at the inoculum size of 1% (v/v). K+ proved to be a favourable cation. The bioflocculant yield of 4 g/L was obtained. Scanning electron microscopy illustrated a hexagonal-like structure of the bioflocculant. It is composed of carbohydrates and proteins in mass proportion of 88.6 and 9.5%, respectively. The Fourier transform infrared spectrum revealed the presence of hydroxyl, amide and amino functional groups. More than 73% of the bioflocculant was obtained after exposure to 600 °C using the thermogravimetric analyser. Human embryonic kidney 293 (HEK 293) cells exhibited 95% viability after being treated with 200 µg/µL of the bioflocculant. The flocculation mechanisms were proposed to be as a result of a double layer compression by K+, chemical reactions and bridging mechanism. The removal efficiencies of 59, 72, and 75% on biological oxygen demand, chemical oxygen demand and sulphur, were obtained respectively. Thus, the bioflocculant have potential use in wastewater treatment.

High Conductivity and Excitation-Power Sensitivity of Upconversion Emission in Silica Decoration of Regular Hexagonal Yb and Er Codoped ZnO Core–Shell Particles

The structure of upconversion materials has an important influence on their photoelectric properties. Herein, we show that the quadrilateral-like structure of Yb/Er/ZnO micronanoparticles grew to regular hexagonal-like structure by increasing the reaction time from 6 to 24 h. Yb/Er/ZnO samples were prepared via a hydrothermal method with polyethylene glycol (PEG) as the dispersant. The structural evolution originated from the addition of PEG dispersant. The Yb/Er/ZnO particles with hexagonal-like structure had increased carrier concentration, carrier mobility rate, Hall coefficient, and resistivity. In addition, a silica shell coating on Yb/Er/ZnO micronanoparticles with hexagonal-like structure (Yb/Er/ZnO@SiO2) was achieved by the Stöber method and improved the electrical conductivity. The migration rate of Yb/Er/ZnO@SiO2 increased to 163.6 cm V s–1. The core–shell interactions decreased the band gap of Yb/Er/ZnO and the energy of defect transition in ZnO host, which significantly improved host sensitization. With increasing power density from 2.04 to 9.04 W/cm2, the intensity of the red upconversion emission was clearly enhanced. Power-dependent multicolor emission excitation was achieved, and the color changed from red to yellow and to green. Moreover, color-correlated temperature (CCT) values changed between the cool region and the warm CCT region, indicating that tricolor emission was controlled via adjusting the excitation power. The regular hexagonal-like structure of Yb/Er/ZnO@SiO2 can be potentially extended to optoelectronic device applications.

Study on the growth and optical properties of ZnO thin films fabricated by ultrasonic spray pyrolysis

In this paper, ZnO nanofilms are prepared on quartz substrate by ultrasonic spray pyrolysis (USP) technology. The effects of substrate temperature and deposition time on the micro-structural, morphological and optical properties of ZnO thin films are investigated in detail. Measurements indicate that the growth process of the film is as follows: Micro grains accumulation [Formula: see text] grains’ expansion [Formula: see text] grow into certain nanostructures under different temperature. Nanostructures of the film are as follows: Irregular broken hexagonal-like structure ([Formula: see text]C); coexisting of broken hexagonal- and sheet-like structure (450–500[Formula: see text]C); regular closed packed sheets-like structure ([Formula: see text]C). In addition, all results show that RMS roughness of the films is less than 20 nm. Moreover, the visible transmittance of these samples is higher than 90%. Which display that ZnO films with low roughness and excellent optical properties can be also fabricated by low-cost USP method.

Simultaneous co-substitution of Sr2+/Fe3+ in hydroxyapatite nanoparticles for potential biomedical applications

In human, strontium (Sr) follows the same physiological pathway as calcium and thus could be used for improving the bioactivity and osteoconductivity of hydroxyapatite (HAp) in bone tissues. Similarly, iron (Fe) can potentially play an important role in bone remodeling due to its magnetic properties. Therefore, the current study was aimed to simultaneously co-substitute Sr2+/Fe3+ in HAp nanoparticles for various potential biomedical applications. The Sr2+/Fe3+ co-substituted HAp nanoparticles were systematically synthesized through sonication-assisted aqueous precipitation method. The as-synthesized nanoparticles were evaluated for different physicochemical and biological properties. X-ray diffraction (XRD) patterns of Sr2+/Fe3+ co-substituted HAp nanoparticles confirmed their phase purity and showed hexagonal-like structure. Scanning electron microscope (SEM) micrographs showed an agglomerated rod-like morphology of HAp nanoparticles which contained pores consisted of small spheroids. The nanoparticles displayed magnetization (Ms) reliance on the loading level of mole % (X = Fe3+) and exhibited tunable porosity and microhardness (Hv) upon heat treatment. The nanoparticles showed less than 5% hemolysis demonstrating high blood compatibility with high in vitro bioactivity performance. The multifunctional properties of synthesized nanoparticles make them a potential candidate for various biomedical applications; including bone grafting and guided bone regeneration, targeted drug delivery, magnetic resonance imaging, and hyperthermia based cancer treatment.

Tuning electrical resistivity anisotropy of ZnO thin films for resistive sensor applications

This work reports on the preparation and characterization of Zinc Oxide (ZnO) thin films, exploring their anisotropic electrical resistivity behaviour evolution as a function of the different preparation conditions. Results show that by increasing the oxygen content in the work gas flow, the electrical resistivity increases from about 2.4 × 10−2 Ω·cm (common in fairly conductive-like materials) to values in order of MΩ·cm, which is typical of materials that vary from semiconducting to roughly insulating type. Regarding the thin films structural behaviour, a relatively clear evolution of the preferential growth becomes clear when preparing the films within the three different regimes. The X-ray diffraction (XRD) patterns revealed the development of a polycrystalline hexagonal-like structure, confirmed by the presence of dominant and very intense ZnO (002) and ZnO (101) diffraction peaks. A change in preferential growth was noticed with the change in the preparation conditions.By in-air annealing the samples from room temperature (RT) up to 200 °C and cooling down to RT again, the differences between the resistivity values along the xx and yy directions become significant, a clear sign of the anisotropic nature of the films. The anisotropy obtained during the annealing cycles of the films increased from 0.98 to 1.10 and, consequently, the Temperature Coefficient of Resistance, TCR, increased in both xx and yy directions, from TCRxx and yy ~9.0 × 10−4 to TCRxx = 6.82 × 10−3 and TCRyy = 5.97 × 10−3 °C−1. Important also to note is that the increase of the grain size of the films showed to have a significant effect in the effective anisotropy, revealing to be a major factor to take into account.

Preparation of silica nanoflakes with spherical mesopores using a dual-templating approach

A pair of chiral low-molecular-weight amphiphiles (LMWAs) was synthesized from phenylglycine, which forms a viscous solution in water. Mesoporous silica nanoflakes were prepared via a dual-templating approach using F127 block copolymer and the LMWAs. The morphologies and pore architectures of the silica nanoflakes were studied using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction, and N2 sorptions. The spherical mesopores opened onto the surfaces of the nanoflakes and were organized in a two-dimensional, hexagonal-like structure. We believe that the pore architectures and morphologies were controlled by the F127 block copolymer and the self-assembly of the LMWAs, respectively. This kind of material has potential for applications in separation and catalysis.

Liquid crystalline cellulosic elastomers: free standing anisotropic films under stretching

The structure and local ordering of 1,6-hexamethylenediisocyanate-(acetoxypropy1) cellulose (HDI-APC) liquid crystalline elastomer thin films are investigated by using X-ray diffraction and scattering techniques. Optical microscopy and mechanical essays are performed to complement the investigation. The study is performed in films subjected or not to an uniaxial stress. Our results indicate that the film is constituted by a bundle of helicoidal fiber-like structure, where the cellobiose block spins around the axis of the fiber, like a string-structure in a smectic-like packing, with the pitch defined by a smectic-like layer. The fibers are in average perpendicular to the smectic-like planes. Without the stretch, these bundles are warped, only with a residual orientation along the casting direction. The stretch orients the bundles along it, increasing the smectic-like and the nematic-like ordering of the fibers. Under stress, the network of molecules which connects the cellobiose blocs and forms the cellulosic matrix tends to organize their links in a hexagonal-like structure with lattice parameter commensurate to the smectic-like structure.

Effect of acidity and structure on the anhydrous proton conduction of acid-doped inorganic–organic hybrid membranes

Homogeneous acid-doped polysiloxane (PS) electrolyte membranes were prepared by the sol–gel reaction from 3-aminopropyltriethoxysilane (APTES) and different acids, such as sulfuric acid (SA), methanesulfonic acid (MSA), ethanesulfonic acid (ESA), and 1-propanesulfonic acid (PSA). The effect of the acidity as well as the structure on the proton transport has been investigated. The interaction between the acid and the basic nitrogen of PS made by APTES has been confirmed by FT-IR and ab initio calculation. The thermal stability depends on the stability of the doping acid. The structure of acid-doped PS was determined by X-ray diffraction pattern and changed with the kind of acid as well as the doping amount. The proton conductivity of annealed (1:1) PS/SA membrane having high acidity as well as the hexagonal-like structure reached 1.1 × 10 −3 S/cm at 120 °C under no (or low) humidity, which is more than one order of magnitude higher than those of PS/acid membranes without structure. The structural effect was studied by PS/ESA membrane having different structure with the amount of acid doping. The proton conductivity of (3:1) PS/ESA membrane showing hexagonal-like structure is 3.82 × 10 −4 S/cm, whereas it is 9.6 × 10 −6 S/cm at 120 °C for amorphous (1:1) PS/ESA membrane. This result implies that the main requirements for high proton transport of electrolyte membranes prepared by acid–base interaction under low humidity are the acidity and the proton transport structure. If the acidity is fixed, then the presence of the ionic channel structure is essential to design the electrolyte membrane having high proton conductivity.