Preparation and optical characterization of catalyst free SiO<Subscript>2</Subscript> sonogel hybrid materials

The synthesis of sol-gel materials induced by ultrasonic irradiation (sonolysis) is implemented as an alternative method for the fabrication of highly pure organic-inorganic composites with good monolithic, mechanical and optical properties. Ultrasonic irradiation, instead of commonly used basic- or acidic-catalyst was used to produce acoustical cavitation within the liquid H₂O/tetraethyl-ortosilicate (TEOS) reactants. This procedure forms a hydrolyzed-TEOS colloidal dispersion (sol) which produces, after drying, a highly pure SiO₂ network. The resulting SiO₂ glass exhibits high porosity and allows the inclusion of several organic compounds in the colloidal sol-state. Novel, optical active synthesized liquid crystalline (LC)-azo-compounds, bent shaped mesogens, cis- and trans-poly(1-ethynylpyrene)s, as well as fullerene (C₆₀) spheres and classical organic dyes were successfully incorporated as dopant agents within the novel catalyst free (CF) SiO₂-sonogel host matrix. Absorption and fluorescence spectroscopy studies were carried out in order to characterize the optical performance of both the CF-sonogel and several hybrid composites The pulsed laser photoacoustic technique (LPAT) was implemented to determine thermodynamic phase transitions of LC-based hybrids and laser induced damage (photo-degradation) in dye-based composites. Finally, comparative morphology studies between undoped reference samples and some doped composites were performed by Atomic Force Microscopy (AFM), where an optimal TEOS/dopant concentration ratio, to obtain good mechanical properties among the studied samples, has been found.     

Gas-phase cluster cations generated by direct laser ablation on AgBr/S mixture

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Multi-stage Ordered Mesoporous Carbon-graphene Aerogel-Ni3S2/Co4S3 for Supercapacitor Electrode

Transition metal sulfides have emerged as promising materials in supercapacitor. In this work, we firstly developed an interface-induced superassembly approach to fabricate NiS_x and CoS_x nanoparticles, which based on ordered mesoporous carbon-graphene aerogel composites for supercapacitor electrodes. The obtained multi-component superassembled nanoparticles-carbon matrix composites have controllable 3D porous structure of multi-stage composite. The two-dimensional graphene interlaced to form a 3D framework with large sponge-like pores, and then the graphene surface was loaded with mesoporous carbon with mesoporous pore size and vertical orientation. The composites display high specific capacitance of 958.1 F g⁻¹ at 0.1 A g⁻¹. The capacitance retains about 97.3 % after 3000 charging-discharging cycles at 2 A g⁻¹. These results indicate that the obtained OMC−GA−Ni₃S₂/Co₄S₃ is a promising material for electrochemical capacitors, which providing new technical methods and ideas for the research of new energy and analytical sensor materials in the fields of energy storage, photocatalysis, point-of-care testing devices and other fields.     

Microstructural characteristics of Ce conversion coatings on Cf/Al composite or Ni?P plated Cf/Al composite

The microstructural characteristics of Ce conversion coatings on carbon fiber reinforced Al matrix (Cf/Al) composites and Ce conversion coatings on Ni? P plated Cf/Al composites were studied by SEM, AFM, TEM and XPS. The Ce conversion coating on the Ni? P plated composite does not have obvious microcracks, which can be found easily in Ce conversion coatings. The Ce conversion coating on Ni? P plated composite has a lower surface roughness profile arithmetic mean deviation (R_a) than Ce conversion coating, as seen by AFM. Because of the inhomogeneity of the material surface and the different levels of deposition of Ce conversion coatings at the different sites, nonhomogeneous sites would promote microcrack formation of the Ce conversion coatings. The Cf/Al composite surface has lessuniformity than Ni? P plated composite, leading to more prominent microcracks. Selected area electron diffraction (SAED) patterns of Ce conversion coating could not be indexed nor matched closely to any of the oxides (Ce₂O₃, Ce₇O₁₂, Ce₆O₁₁) or hydroxides (Ce(OH)₃) that are listed in the Powder Diffraction File maintained by Diffraction Data, but for Ce conversion coating on the Ni? P plated composite the data matched closely with that of CeO₂ or Ce₆O₁₁. The XPS results showed that the Ce conversion coating mainly contained both Ce³⁺ and Ce⁴⁺ species, but Ce⁴⁺ species were the dominant oxidation state on Ni? P coating with Ce conversion deposition. Copyright © 2008 John Wiley & Sons, Ltd.     

A novel liquid crystals photoalignment layer-by-layer self-assembled film fabricated with long side-chain cinnamate polyelectrolyte

A novel photoalignment film for liquid crystals (LC) was prepared based on layer-by-layer self-assembly of photosensitive long side-chain cinnamate polyelectrolyte. A series of self-assembled films with different methylene spacer groups was prepared and used as alignment film. The film became anisotropic, and could induce uniform alignment of LC after irradiation by linearly polarised ultraviolet light (LPUVL). The effects of spacer chain lengths of the cinnamoyl polycations on the structure and photoalignment properties of the self-assembled film were studied. The polycation films with longer spacer chain obtained a larger dichroic ratio after LPUVL irradiation. The contrast ratio (T _max/T _min) of the LC cell increased with spacer chain length increase. However, it was found that the thermal stability of PSS/PACPYn films decreased with increasing chain length of polycation.     

Photocurrent Response of Surface‐Functionalized Metal Oxides with Well‐Matched Energy Levels: From Nothing to Something

In recent years, an enormous amount of research has been devoted to the study of photosensitive materials from both fundamental and practical viewpoints, due to their wide applications in photocatalytic 1 – 3 and optoelectronic devices, 4 , 5 ultraviolet (UV) photodetectors, 6 – 9 photoswitch microdevices, 10 , 11 light‐emitting diodes, 12 , 13 photovoltaic devices, 14 – 16 and photoelectrochemical cells. 17 Metal oxides, such as ZnO, TiO₂, SnO₂, and NiO have been the most investigated photosensitive materials. 3 , 6 – 8 , 18 – 21 To enhance and take full advantage of their photosensitivity, functionalizing their surface with a polymer that has a high light absorption ability has become one of the widely used methods. 1 – 12 , 22 – 24 For example, Z. L. Wang et al. reported that the UV photocurrent of a ZnO nanobelt‐based sensor was enhanced by close to five orders of magnitude after functionalizing its surface with polystyrene sulfate which has a high UV absorption ability. 25 T. Sasaki et al. reported the assembly of a TiO₂ nanoparticle film with poly(3,4‐ethylenedioxythiophene) and poly(4‐styrene sulfonate) (PEDOT‐PSS) through layer‐by‐layer fabrication in the nanometer scale. The electric conductivity of the TiO₂ composite films could be tuned by UV and visible (Vis) light. 22 Thus, sunlight or photon energy can be used and transformed to electrical energy by UV‐photosensitive metal oxides after their surfaces have been functionalized with a dye that has a high Vis absorption ability. To date, most of the dye‐sensitized solar cells are based on the surface functionalization of UV‐photosensitive metal oxides by dyes. 26 – 28 However, to the best of our knowledge, all of the reports on surface functionalization enhanced only the UV photosensitivity of the metal oxide. In other words, this method has been used exclusively to enhance the UV photocurrent in metal oxides that already have UV‐photosensitive properties, but not to induce UV photocurrent in metal oxides that have no UV‐photosensitive properties. In fact, to the best of our knowledge, there are no surface‐functionalizing reports on inducing UV or Vis photocurrent in metal oxides that have no UV‐ or Vis‐photosensitive properties.     

Metallopolymer–Peptide Hybrid Materials: Synthesis and Self‐Assembly of Functional,Polyferrocenylsilane–Tetrapeptide Conjugates

Conjugates of poly(ferrocenyldimethylsilane) (PFDMS) with Ac‐(GA)₂‐OH, Ac‐A₄‐OH, Ac‐G₄‐OH and Ac‐V₄‐OH have been prepared by reaction of the tetrapeptide units with the amino‐terminated metallopolymer. The number average degree of polymerisation (DP_n) of the PFDMS was approximately 20 and comparable materials with shorter (DP_n≈10) and/or amorphous chains have been prepared by the same procedure. Poly(ferrocenylethylmethylsilane) (PFEMS) was employed for the latter purpose. All conjugates were characterised by GPC, MALDI‐TOF MS, NMR and IR spectroscopy. With the exception of Ac‐V₄‐PFDMS₂₀, all materials exhibited some anti‐parallel β‐sheet structure in the solid state. The self‐assembly of the conjugates was studied in toluene by DLS. The vast majority of the materials, irrespective of peptide sequence or chain crystallinity, afforded fibres consisting of a peptidic core surrounded by a PFS corona. These fibres were found in the form of cross‐linked networks by TEM and AFM. The accessibility of the chemically reducing PFS corona has been demonstrated by the localised formation of silver nanoparticles on the surface of the fibres.     

Comparison of the photonic effects of Mn-CNT/TiO<Subscript>2</Subscript> composites modified by different oxidants

Manganese-carbon nanotubes (CNTs) on titania (TiO₂) composites modified by different oxidants (KMnO₄, (NH₄)₂S₂O₈ and m-chlorperbenzoic acid (MCPBA)) were prepared with a sol-gel method. These composites were comprehensively characterized by the Brunauer-Emett-Teller (BET) method, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy EDX, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. The photoactivity of these materials prepared under visible light irradiation was tested using methylene blue in aqueous solution. The result shown that among the three oxidants, the MCPBA was the best one for the surface functionalization of CNTs and the manganese treated CNT/TiO₂ composite can enhance the photocatalytic activity. The proposed mechanism of the photodegradation of methylene blue on Mn-CNT/TiO₂ composites was present.     

Preparation of nano-structured LiFePO4/graphene composites by co-precipitation method

Graphene materials with superior electrical conductivities and high surface area would be advantageous for application in energy storage. And LiFePO₄ has been a promising electrode material however its poor conductivity limits its practical application. To improve the electronic conductivity, we prepare LiFePO₄/graphene composites in a co-precipitation method, in which graphene nanosheets are used as additives. The composites were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), and their electrochemical properties were investigated by galvanostatic charge and discharge tests. The experimental results show that the capacity delivery and cycle performances of LiFePO₄ could be improved considerably by adding graphene. Therefore, LiFePO₄/graphene composites are a promising candidate for lithium secondary batteries.     

Solvothermal Synthesis of [Cr7S8(en)8Cl2]Cl3 ⋅ 2H2O with Magnetically Frustrated [Cr7S8]5+ Double-Cubes**

A novel transition metal chalcohalide [Cr₇S₈(en)₈Cl₂]Cl₃ ⋅ 2H₂O, with [Cr₇S₈]⁵⁺ dicubane cationic clusters, has been synthesized by a low temperature solvothermal method, using dimethyl sulfoxide (DMSO) and ethylenediamine (en) solvents. Ethylenediamine ligand exhibits bi- and monodentate coordination modes; in the latter case ethylenediamine coordinates to Cr atoms of adjacent clusters, giving rise to a 2D polymeric structure. Although magnetic susceptibility shows no magnetic ordering down to 1.8 K, a highly negative Weiss constant, θ=−224(2) K, obtained from Curie-Weiss fit of inverse susceptibility, suggests strong antiferromagnetic (AFM) interactions between S=3/2 Cr(III) centers. Due to the complexity of the system with (2S+1)⁷=16384 microstates from seven Cr³⁺ centers, a simplified model with only two exchange constants was used for simulations. Density-functional theory (DFT) calculations yielded the two exchange constants to be J₁=−21.4 cm⁻¹ and J₂=−30.2 cm⁻¹, confirming competing AFM coupling between the shared Cr³⁺ center and the peripheral Cr³⁺ ions of the dicubane cluster. The best simulation of the experimental data was obtained with J₁=−20.0 cm⁻¹ and J₂=−21.0 cm⁻¹, in agreement with the slightly stronger AFM exchange within the triangles of the peripheral Cr³⁺ ions as compared to the AFM exchange between the central and peripheral Cr³⁺ ions. This compound is proposed as a synthon towards magnetically frustrated systems assembled by linking dicubane transition metal-chalcogenide clusters into polymeric networks.     

Director configurations in nematic droplets with tilted surface anchoring

The polymer dispersed nematic liquid crystal (LC) with the tilted surface anchoring has been studied. The droplet orientational structures with two point surface defects – boojums and the surface ring defect – are formed within the films. The director tilt angle α = 40° ± 4° at the droplet interface and LC surface anchoring strength W_s ~ 10^–6 (J m^?2) have been estimated. The bipolar axes within the studied droplets of oblate ellipsoidal form can be randomly oriented are oriented randomly relatively to the ellipsoid axes as opposed to the droplets with homeotropic and tangential anchoring.     

Mechanical Analysis of Bio Nanocomposite Prepared from Luffa cylindrica

Luffa cylindrica (LC), a tropical vegetal product, consists of highly vascular system. It has been modified by calcium phosphate and calcium carbonate separately to produce composites of Ca-salts. The modified form of LC has been reinforced with novolac resin at 30 °C to provide cross linked polymer composites. The composites have been further sonicated at 40 °C for 1 h to produce bio nano composites. The final yield is more than 80% of the raw materials used. The physical and chemical analysis of the composites have been done. Incorporation of resin in to the inner fiber surface of LC which is rich in cellulose is confirmed from ultra-violet spectroscopy (UV), and Fourier transform infrared (FTIR) analysis. Thermal studies of the composites done in an inert atmosphere reveals that the composites decompose within a temperature range of 250 - 550 °C. The tensile parameters such as maximum stress, Young's modulus and yield strength were measured. The compressive and flexural strength of the LC fiber- reinforced composites were also studied by varying the weight of fiber in the resin.     

The compressive electrical field electrostrictive coefficient M33 of electroactive polymer composites and its saturation versus electrical field,polymer thickness,frequency, and fillers

Electroactive polymers are widely studied because of their large electrical‐field‐induced strain. Their flexibility and their ability to be deposited on large surfaces make them promising candidates as electroactive materials for actuators or energy‐harvesting devices. For actuation purposes, the material efficiency is directly related to the electrical‐field‐related electrostrictive coefficient M₃₃ through S₃₃ = M₃₃E², where S₃₃ is the electrical‐field‐induced strain and E is the applied electrical field. Numerous studies concern the increase of M₃₃, but very few have been devoted to its saturations versus electrical field. To this end, the present paper describes the variation of M₃₃ versus thickness, composition, frequency, and electrical field for polyurethane‐based composites. Based on the saturation of the electrical‐field‐induced polarization within the studied polymer composites, a model of the M₃₃ behavior was also proposed, and it was found to show a good agreement with the experimental data. In addition, this model predicts the dielectric constant and the saturation electrical field to be the key parameters ruling the M₃₃ saturation. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of sampling constants for selenium in biological reference materials by neutron activation

Summary A cyclic instrumental neutron activation analysis method has been used to calculate sampling constants and to evaluate homogeneity for Se in five biological reference and certified reference materials, namely NRC lobster hepatopancreas (RM TORT-1), IAEA horse kidney (RM-H8), and NIST bovine liver (SRM-1577a), oyster tissue (SRM-1566) and mixed diet (RM-8431). The between-weight-range heterogeneity has been observed to be no greater than the within-weight-range heterogeneity. The subsampling standard deviation (S _s) has been found to be less than the measurement standard deviation (S _m) for H-8 (>5 mg sample) and TORT-1 (>50 mg). For 1577a, S _s is almost equal to S _m; while S _s is 2–3 times higher than S _m for the other two materials. The sampling constants varied between 0.04 and 3.0 g for four materials while the mixed diet had a value of 31 g.     

Phototunable Liquid‐Crystalline Phases Made of Nanoparticles

The properties of liquid‐crystalline (LC) hybrid systems made of inorganic nanoparticles grafted with photosensitive azo compounds are presented. For materials with a large density of azo ligands at the surface, the LC structure can be reversibly melted by UV light, and the return to the LC state does not require the absorption of visible light. For systems with a lower density of azo ligands, UV light causes shortening of the distance between metal sublayers in the lamellar phase. Interestingly, the azo derivatives attached to the nanoparticle surface show very different kinetics of cis/trans conformational change as compared to the free molecules. The cis form of free ligands in solution is stable for days, whereas the isomerization of molecules attached to the nanoparticle surface to the trans form takes only a few minutes. Apparently, owing to the crowded environment, azo ligands immobilized at a metal surface behave as they would in the condensed state.     

Preparation Bi2S3-TiO2 heterojunction/polymer ?ber composites and its photocatalytic degradation of methylene blue under Xe lamp irradiation

This paper presented the preparation of Bi₂S₃-TiO₂ heterojunction/polymer ?ber composites and their performance of the degradation of methylene blue using Xe lamp irradiation. The polysulphone (PSU)/styrene-maleic anhydride copolymer (SMA) ?bers were prepared by electrospinning. Bismuth ions were introduced onto the surface of polymer ?ber by the coordinating of carboxyl of SMA, sul?de ions were incorporated to react with bismuth ions under hydrothermal condition. TiO₂ was deposited on the surface of the Bi₂S₃ by the reaction of titanium ions with urea also under hydrothermal condition. Scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM) images revealed that Bi₂S₃-TiO₂ heterojunction was uniformly distributed on the surface of PSU/SMA ?bers. The ultraviolet-visible absorption spectra (UV/VIS) showed that the Bi₂S₃-TiO₂ heterojunction/polymer ?ber composites possess good visible-light response ability. The degradation rate of methylene blue in Bi₂S₃-TiO₂ heterojunction/polymer ?ber composites system was considerably higher than that of Degussa P25 or Bi₂S₃-TiO₂ heterojunction system under Xe lamp irradiation.     

The effect of ethanol on the phase behaviour and micro-rheology of liquid crystals

The effect of ethanol on the phase behaviour and micro-rheology of lyotropic liquid crystals (LC) has been studied using a binary mixture of monoglyceride (MG) and aqueous ethanol. The phase behaviour study reveals the structural modulation of surfactant aggregates with increasing ethanol concentration, namely a bicontinuous cubic phase (Ia3d) transitions to the lamellar phase (L_α), at a fixed MG concentration. This behaviour is explained by considering the critical packing parameter (CPP) of the surfactant molecule. Because ethanol dehydrates the surfactant head group (a _s), the CPP values increase (decreasing a _s) and thus the formation of larger CPP aggregates is favoured (i.e., the Ia3d–L_α transition occurs). Cross-polarised images and X-ray scattering data support this conclusion. The structural modulation of the LC has further been investigated using a diffusing wave spectroscopy technique. The correlation and relaxation times, determined from the intersection point at short and long time scales of the mean square displacement (MSD), decrease with increasing concentrations of ethanol, indicating structural modulation of the LC. The micro-viscoelastic moduli (G′ and G′′) derived from the Laplace transformation of the MSD decrease with increasing ethanol concentrations, due to the LC modulation. The thermal effects on the micro-rheology of the LC have also been studied.     

Thin-film polymerization and characterization of Sumitomo's Sumikasuper®-type liquid crystalline polymers

Using the thin film polymerization approach, we have studied the texture evolution when synthesizing a novel liquid crystalline polymer (LCP) system based on Sumikasuper^® LCPs. The main monomers used were p-acetoxybenzoic acid (ABA), 4,4′-biphenol (BP), isophthalic acid (IA), phthalic acid (PA) and terephthalic acid (TA). Polarizing optical microscopy (POM), FTIR, X-ray diffraction (XRD) and atomic force microscopy (AFM) were employed to study the thin film polymerization process and characterize the products. The generation and evolution of liquid crystal phases were monitored; the results revealed that there exists a composition range for the monomers to react and form liquid crystal materials. The critical temperature for LC formation in ABA/BP/IA system decreased with increasing ABA content. FTIR results confirmed the formation of polymers. AFM investigation suggested a similar process of morphological change to that observed using POM. An increasing surface roughness of the thin films with the progress of polymerization was also obtained from AFM analysis. A nematic LC texture of the polymer system was suggested by XRD examination. Results obtained by replacing BP with acetylated BP, and by conducting polymerization using two-monomer systems, suggest that BP units are included in polymers obtained by the thin film polymerization method.     

Synthesis of 2, 5, 5-Trimethylhepta-2, 6-Dien-4-One (Artemisia Ketone): II. Using A Thioacetal Monoxide

The polymer-bound catalyst 3a-e inserted some spacer ([-NHCO(CH_{2 10- n}; n = 0,1,2,3,4) connecting the catalytic moiety [cyclo(-(S)-Phe-(S)-His)], [(S,S)-1] and 2% cross-linked Merrifield's polymer, have been prepared and their catalytic efficiency for the enantioselective hydrocyanation of 3-phenoxybenzaldehyde was studied.