Synthesis and properties of organic–inorganic hybrid liquid crystal gels

Organic–inorganic hybrid liquid crystal (LC) gels have been synthesised by the thiol-ene reaction of a multifunctional cyclic siloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TVMCTS) and alkane dithiols, 1,6-hexanedithiol (HDT) or 1,9-decanedithiol (DDT), in LC matrices, 4-cyano-4?-pentylbiphenyl (5CB) or 4′-n-octyl-4-cyano-biphenyl (8CB). The LC gels were prepared in an isotropic phase at 70°C or mesophases at 25°C using radical initiators. The phase transition temperatures from a mesophase to an isotropic phase of the resulting gels were lower than those of the original LCs. The gels containing 8CB (8CB gels) prepared at 25°C showed two phase transitions: smectic-to-nematic and nematic-to-isotropic transitions. By contrast, the 8CB gels synthesised in the isotropic phase showed only one phase transition from smectic phase directly to isotropic phase. Reaction conversions in the LC gels prepared at 70°C were higher than that in the gels prepared at 25°C. Scanning microscopic light scattering analysis of the LC gels cleared homogeneous small size mesh with a small amount of large defect. Polarisation micrographs of the LC gels showed framed optical textures derived from the LC molecules at room temperature. The LC gels containing more than 90 wt% of LC showed electro-optic response.     

Structure and fabry-pérot fringes of polymer-boehmite hybrid thin film by sol–gel dip-coating

Journal of Sol-Gel Science and Technology - Polyvinylpyrrolidone (PVPON)-boehmite hybrid thin film was deposited onto glass by sol–gel dip-coating method. The Fabry-Pérot fringe in...     

Comparison of performances of bioanodes modified with graphene oxide and graphene–platinum hybrid nanoparticles

The performances of graphene oxide (GO) and graphene–platinum hybrid nanoparticles (Gr-Pt hybrid NPs) were compared for biofuel cell (BFC) systems. This is the first study that constitutes these nanomaterials in BFC systems. For this purpose, fabricated bioanodes were combined with laccase modified biocathode in a single cell membraneless BFC. Power and current densities of these systems were calculated as 2.40 μW cm^− 2 and 211.90 μA cm^− 2 for GO based BFC and 4.88 μW cm^− 2 and 246.82 μA cm^− 2, for Gr-Pt hybrid NPs based BFC. As a result, a pioneer study which demonstrates the effective performances of combination of graphene with Pt was conducted.     

Polyurethane–imide–polyhedral oligomeric silsesquioxane hybrid nano-composites

Journal of Thermal Analysis and Calorimetry - In order to improve thermo-stability of polyurethane (PU), both imide group and polyhedral oligomeric silsesquioxane (POSS) were introduced into PU...     

Organic–inorganic hybrid melting gels

Melting gels are a class of organically modified silica gels that are rigid at room temperature, flow at temperature T1 and consolidate at temperature T2 (T2 > T1), when crosslinking is complete. The process of (a) softening, (b) becoming rigid and (c) re-softening can be repeated many times. Mixtures of mono-substituted alkoxysilanes and di-substituted alkoxysilanes have been studied in a systematic way to identify suitable melting gel compositions. The mixtures and the resulting melting gels have been characterized for their softening temperatures and consolidation temperatures. With an interest in using these materials for sealing microelectronics, their physical properties have been measured.     

Characterization and electrochemical study of hemoglobin–carbon nanoparticles–polyvinyl alcohol nanoporous hybrid film

A hybrid film is fabricated by casting hemoglobin (Hb)–carbon nanoparticles (CNPs)–polyvinyl alcohol (PVA) suspension on glassy carbon electrode (GCE). The resulting film shows a three-dimensional nanoporous structure. In the hybrid film, the ultraviolet visible (UV–Vis) absorption spectra of Hb keep almost unchanged. The organic–inorganic hybrid material can promote the direct electron transfer of Hb. A pair of well-defined and quasireversible peaks with a formal potential of −0.348 V (vs saturated calomel electrode) is obtained, which is caused by the electrochemical reaction of the Fe(III)/Fe(II) couple of Hb. The electron transfer rate constant (k _s) is estimated to be 3.9 s⁻¹. The immobilized Hb exhibits high stability and excellent electrochemical catalysis to the reduction of oxygen (O₂), hydrogen peroxide (H₂O₂), and nitrite (). The catalytic currents are linear to the concentrations of H₂O₂ and from 1.96 to 112 μM and from 0.2 to 1.8 mM, respectively. Therefore, the hybrid film may be a good matrix for protein immobilization and biosensor fabrication.     

Microstructure and performance of AZO thin films prepared by sol–gel processing

Al-doped zinc oxide (AZO) films were prepared by a wet-chemical coating technique, their microstructure and crystal growth were characterized as a function of the single layer thickness. When similar final thicknesses are attained by more multiple subsequent coating-firing cycles, film porosity is reduced from over 14 to 2 %. Simultaneously the AZO crystallite size is increased from approximately 23 to 60 nm, a preferential c-axis oriented growth is observed. Different substrates (soda-lime glass, soda-lime glass with a SiO₂ barrier coating, borosilicate glass and alkali-free display glass) were used and the resulting AZO films were compared. It is found that the substrate composition primarily affects grain growth and subsequently the electrical performance of the AZO films.     

Recent developments in polymer–block–polypeptide and protein–polymer bioconjugate hybrid materials

In the last few years, polymer bioconjugates have been shown to be useful in many emerging areas of materials science. Consequently, the synthesis of polymer bioconjugates has suddenly become a central topic in polymer chemistry. The versatility and robust nature of modern synthetic methods such as controlled radical polymerisation (CLRP),¹ ring-opening polymerisation (ROP), and ‘click’ chemistry make them excellent tools for the preparation of tailor-made polymer bioconjugates. CLRP in combination with other techniques has been shown to be a mature technology for building tailor-made block copolymers and protein–polymer conjugates with a wide range of applications, especially in biomedical domains. This review describes the recent advances and progress in the rapidly expanding field of bioconjugation, outlining the work performed up to 2012.     

Mechanical and sodium ion conductivity properties of graphene oxide–incorporated nanocomposite polymer electrolyte membranes

Journal of Solid State Electrochemistry - Graphene oxide (GO) nano-sheets incorporated PEO/PVA composite membranes complexed with NaIO4 salt at different concentrations were prepared using the...     

Controllable preparation of nanosized TiO_2 thin film and relationship between structure of film and its photocatalytic activity

~~Controllable preparation of nanosized TiO_2 thin film and relationship between structure of film and its photocatalytic activity@魏刚$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China @张元晶$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China @熊蓉春$College of Material Science and Engineering,Beijing University of Chemical Technology! Beijing 100029,China~…     

Thermo-hydraulic and entropy generation analysis of recharging microchannel using water-based graphene–silver hybrid nanofluid

Journal of Thermal Analysis and Calorimetry - This work numerically investigates thermo-hydraulic and entropy generation characteristics of water-based graphene–silver (Gr–Ag) hybrid...     

Evaluation of solubility and diffusion coefficients in polymer film–vapor systems by sorption experiments

Sorption experiments are commonly used to determine the equilibrium and kinetics of mass-transfer processes of vapors in polymeric materials. Electrogravimetry is recognized as a powerful technique. A discussion of the standard theoretical approach to determine solubility and diffusion coefficients is presented. The reduced mathematical expression commonly used for calculations of D values is discussed. A consistency test to check for common deviations caused by the experimental complexity is discussed and resolved.The sorption of hexanol and ethyl caproate into a metallocene polyethylene and an ionomer was measured by electrogravimetry. Transport was characterized through the solubility and the diffusion coefficients. The formalism presented was used in these experiments and is commented upon.     

Preparation and characterization of crack-free sol–gel based SiO2–TiO2 hybrid nanoparticle film

Owing to the diverse potential applications of hybrid silica–titania thin films, the synthesis and characterization of these films have been carried out with a special focus on application as a medium index layer for multilayered functional coatings. For synthesis, tetraethylorthosilicate and titanium tetraisopropoxide were chosen as precursors for the formation of silica-titania hybrid thin films/nano-composites through an in situ sol–gel process. These films were sequentially obtained on Cu substrate utilizing spin coating. The hybrids were characterized by field emission scanning electron microscope, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, atomic force microscopy and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscope morphology displayed a smooth, densified and crack- free layer of silica-titania hybrid nanoparticles in the range of 20–71 nm after calcinations at low temperature of 300ºC for 1 h. X-ray diffraction pattern confirms the phases of titania with higher crystallinity and phase transformation at low temperature. The prepared films were uniform with low 8.852 nm RMS value. The stoichiometry of films was confirmed by EDX results. The FTIR spectroscopy indicated the establishment of heterogeneous chemical bonding between the Ti and Si surfaces through oxygen.     

Selective soluble polymer–assisted electrochemical delamination of chemical vapor deposition graphene

Journal of Solid State Electrochemistry - We have explored an optimized electrochemical delamination technique to transfer large area graphene grown by chemical vapor deposition (CVD) technique. A...     

Study of precursor-solution purity for high-quality yttrium–barium–copper-oxide superconducting thin film

Trifluoroacetic acid-metal-organic deposition (TFA-MOD) is an effective method to prepare high-quality yttrium–barium–copper oxide (YBCO) superconducting thin films with a large area. Chemical reactions and purification are the keys to the preparation of the precursor solution in the TFA-MOD method. In this study, the process of preparing the precursor solution was examined by the infrared spectra systematically, and each infrared spectrum was determined by Fourier-transform-infrared spectroscopy (FTIR) to judge the possible side reactions. The results show that organic functional groups have no side effects at room temperature (20?±?2°C). And the purification process can remove excess water, acid, and so on. The purity of the precursor solution would increase with distillation. When the relative height ratio of CF^3? and the C?OH absorption peak in the spectra of solution 3, which has been purified three times, reaches 0.664, and the relative ratio of C?F and the C?OH absorption peak is 0.418, a YBCO thin film can be obtained with a perfectly uniform surface. Its transition-onset temperature is approximately 90.9?K, the value of critical current density (J_c) is 2.32?mA/cm² (77?K, 0?T), and the growth of the superconducting film is strongly oriented to the c-axis. In addition, it was found that distillation removes excess water, acetic acid, and other small molecules, and determines the quality of YBCO thin films. For this performance, a superconducting film has been successfully applied to filter the fabrication. Therefore, this method is essentially an effective method to study the content of impurities in the precursor solution in order to form a superconducting film with good quality.

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The picture above is a summary of the article charts, divided into four major steps. In this study, the process of preparing the precursor solution was examined by infrared spectra systematically, and each infrared spectrum was determined by Fourier transform infrared spectroscopy (FTIR) to judge possible side reactions. And the microstructure and superconductivity of thin film have been characterized by XRD, SEM, CRYO SCAN equipment and four-probe method. Finally, this performance of superconducting film haves been successfully applied to the filter fabrication through this research method.

     

Catalytic oxidation and determination of β-NADH using self-assembly hybrid of gold nanoparticles and graphene

A self-assembly hybrid of gold nanoparticles on graphene modified electrodes for low-potential NADH detection has been achieved. We used the natural polymer chitosan (Chit) to assist the stabilization of graphene in aqueous solution, and immobilize the electronegative Au nanoparticles (NPs) through electrostatic attraction. The synergy of Au NPs with graphene for catalytic oxidation of NADH made the overpotential ca. 220 mV less positive than that on the bare electrode, and remarkably increased the oxidation current. The amperometric sensors based on such modified electrodes for detection of NADH exhibited a good linearity from 1.5 to 320 μM, and showed high sensitivity with a low detection limit of 1.2 μM (S/N = 3). It could also exclude common interfering electroactive compounds like ascorbic acid and possessed good reproducibility and operational stability. Such eminent performance of the Au-RGO/Chit film together with the ability of graphene to significantly enhance the electron transfer between enzymes and the electrode suggested its promise for constructing novel graphene based dehydrogenase biosensors.     

Structural evolution of nanostructured barium titanate thin film sol–gel derived

Ferroelectric nanostructured barium titanate (BT) thin films derived by a modified sol–gel process were formed by a deep coating method on Si (100) substrate. In this work was investigated the influence of different types and amounts of water (free water directly added in process and crystalline water from barium precursors) and of different barium precursors (hydroxide and acetate) on the gel-structure evolution and the barium titanate thin film crystallization. The IR-spectroscopy and X-ray diffraction analysis were used for sample characterization. Experimental results show that crystalline water from barium hydroxide octahydrate stabilizes the cubic phase of barium titanate. Barium titanate crystallizes in the tetragonal form in thin films when sols were prepared with free water and Ba-acetate or Ba-hydroxide monohydrate as precursors. The type of Ba-precursor used in preparation of sols effects the rate of crystallization of the BT in thin films, making it slower in the case when as precursor was used Ba-acetate than Ba-hydroxides. The prepared BT-thin films demonstrated good adhesion towards substrate and were smooth and uniform.     

Viscoelastic properties of PS–POSS hybrid materials prepared by reactive processing

The viscoelastic properties of hybrid nanocomposites of polystyrene and polyhedral oligomeric silsesquioxane (PS–POSS) are determined in the molten state by small-amplitude oscillatory shear rheometry (SAOS) and in the solid state by dynamical-mechanical thermal analysis (DMA). PS–POSS samples synthesized to form various molecular structures and phase morphologies are investigated. Overall, both viscoelastic data sets correlate well with the POSS dispersion level and with the degree of grafting of the PS–POSS samples. From the SAOS data, enhanced POSS dispersion and degrees of grafting are characterized by deviations of the zero-frequency viscosity ratios of the Einstein and Einstein–Batchelor models and by linearity in the Han plots. PS–POSS samples with enhanced POSS dispersion and degrees of grafting are characterized as those with higher free-volume fractions and lower flow activation energies, as determined by storage modulus master curves that stem from applying the time-temperature superposition (TTS) principle to the DMA data.     

Sol–gel processed indium zinc oxide thin film and transparent thin-film transistors

Indium–zinc oxide (IZO) thin films were fabricated by spin coating using acetate- and nitrate-based precursors, and thin film transistors (TFTs) were further fabricated employing the IZO films as the active channel layer. The impact of the indium concentration on the properties of the solutions, the structure and optical transmittance properties of the IZO films and the IZO TFTs device properties were researched in this article. The IZO films with amorphous structure were obtained when the annealing temperature is 500 °C. The transmittance could reach ~90 % (including glass substrate) during the visible region of 400–760 nm. Higher indium concentration can improve the IZO TFTs’ filed effect mobility. A I_on–I_off of 6.0 × 10⁶ and a mobility of 0.13 cm²/Vs were obtained when the indium concentration is 60 %. IZO TFTs’ performance could deteriorate when the indium concentration more than 60 %.