Supercapacitor study of reduced graphene oxide/Zn nanoparticle/polycarbazole electrode active materials and equivalent circuit models

Journal of Solid State Electrochemistry - In this study, graphene oxide (GO) was chemically reacted with sodium borohydride (NaBH4) to form reduced graphene oxide (rGO). rGO and rGO/Zn...     

Synthesis and spectral properties of novel seco-porphyrazines with eight 4-biphenyl groups

Magnesium porphyrazinate substituted with eight 4-biphenyl groups on the periphery positions has been synthesized for the first time from cyclotetramerization of 1,2-bis(4-biphenyl)maleonitrile in the presence of magnesium butanolate. Its demetalation by treatment with trifluoroacetic acid, resulted in a partially oxidized product, namely, octakis(4-biphenyl)-2-seco-porphyrazine-2,3-dione. Further reaction of this product with copper(II) acetate, zinc(II) acetate and cobalt(II) acetate has led to the metallo derivatives, [octakis(4-biphenyl)-2-seco-2,3-dioxoporphyrazinato] M(II) (M = Cu, Zn, Co). These novel compounds have been characterized by elemental analysis, together with FT-IR, ¹H NMR, UV–Vis and mass spectral data.     

Photoconductive novel mesomorphic oxotitanium phthalocyanines

The synthesis and photoconductivity properties of the alkylthia and triethyleneoxysulfonyl substituted oxotitanium(IV) phthalocyanines (1a and 2a) are reported for the first time. The new compounds have been characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopy, electronic spectroscopy and mass spectroscopy. The mesogenic properties of these new materials were studied by differential scanning calorimetry and optical microscopy. The electrical dark conductivities (σ_d) and photoconductivities (σ_ph) of deposited films of 1a and 2a were investigated in various media with different concentrations of oxygen. Molecular oxygen increases photoconductivities (σ_ph) significantly. The photoconductivity mechanism and formation of Pc⁺ which is positive charge carrier under the light irradiation of the phthalocyanine molecules are demonstrated using the theoretical calculations. The geometries of the oxotitanium(IV) phthalocyanines (TiOPc) are optimized with PM3 semi-empirical method, and their visible absorption maxima are calculated with ZINDO/S method. The results agree well with the observed values. It was found that for the calculation of visible absorption of neutral and positively charged substituted TiOPc molecules using ZINDO/S method could rapidly yield excellent results. Dipole moment, HOMO, LUMO energies and atomic charges are also calculated for clarification of the oxygen effect on the photoconductivity using PM3 and ZINDO/S methods.     

Facile large-scale fabrication of proton conducting channels

A new approach to the facile large-scale fabrication of robust silicon membranes with artificial proton conducting channels is presented. Ordered two-dimensional macroporous silicon was rendered proton conducting by growing a thick uniform polyelectrolyte brush using surface-initiated atom transfer radical polymerization throughout the porous matrix. The fabricated silicon-poly(sulfopropyl methacrylate) hybrid membranes were evaluated for their proton conductivity, ion exchange capacity, and water uptake. With proton conductivities in the range of 10(-2) S/cm, these proof-of-concept experiments highlight a promising alternative for producing tailorable proton conducting membranes. This approach constitutes a benchmark for the preparation and study of model systems and, in addition, for the large-scale fabrication of membranes suitable for a wide range of technological applications.     

Influence of acrylate arm topology on phase diagrams of mixtures of multiarm acrylate photocurative monomers and nematic liquid crystals

Phase equilibria of binary mixtures of liquid crystal and multiarm star acrylate derivatives have been established as a function of the number of acrylate arms by means of cloud point determination. Equilibrium phase diagrams of liquid crystal/multiarm acrylate derivatives have been calculated self-consistently in the framework of combined Flory-Huggins free energy of liquid-liquid demixing and Maier-Saupe free energy of nematic ordering. It was found experimentally that the phase diagram of the branched/star molecule/solvent shifts to elevated temperatures with an increasing number of acrylate arms. This movement of the coexistence line is attributed to the architectural effect contributing to the athermal entropic part of the chi interaction parameter. The present self-consistent solution has been tested satisfactorily with the observed phase diagrams of liquid crystal/acrylate systems.     

Synthesis and characterization of liquid crystalline tetra- and octa-substituted novel phthalocyanines

Methylene-bridged tetra- and octa-(13,17-dioxa nonacosane-15 sulfanyl)-substituted metal free- and Ni(II) phthalocyanines were synthesized from the corresponding phthalonitrile (3, 4) derivatives in the presence of the anhydrous metal salt (NiCl₂) or a strong organic base. The new compounds were characterized by elemental analyses, UV/Vis, IR, NMR and mass spectra. The mesogenic properties of these materials were studied by differential scanning calorimetry (DSC), optical microscopy and X-ray diffraction investigations. X-ray diffraction patterns of the mesophase confirm that tetra- and octa-substituted compounds (3a–b, 4a–b) form hexagonal columnar mesophases (Col_h). We indicated that addition of the methylene-bridged phthalocyanine (Pc) core can either decrease the liquid crystal phase transition temperatures or extend the liquid crystal temperature range to include room temperature. Also, the Pc compounds (3a, 3b, 4a and 4b) are liquid crystals at room temperature. These properties of the Pc complexes provide some advantages such as easily obtaining an ordered film for sensor applications. Computational modelling work was combined with X-ray diffraction investigation to validate the diameter of the phthalocyanine molecule (3b).     

Charge transfer complex formation in in-situ maleic anhydride and N-vinyl caprolactam copolymer and copolymer/organo-montmorillonite nanoarchitectures

The binary copolymerization of maleic anhydride (MA) and N-vinyl caprolactam (VCL) or considered as acceptor (A)?donor (D) monomer systems were used (MA:VCL) 50:50 in BPO (0.5%) as an initiator at 70°C under nitrogen atmosphere. The functional copolymers, having a combination of rigid/flexible linkages and an ability of complex-formation with interlayered surface of organo-silicate, and their nanocomposites have been synthesized. Interlamellar in situ complex-radical copolymerization of intercalated monomer complexes of MA and VCL undergoes with stearyl amine surface modified montmorillonite (O-MMT) and monomer mixtures. Charge transfer complex formation was followed and identified by UV-Vis-NIR spectroscopy. Equilibrium constant (K_AD) molar absorption coefficient (?^AD)) of the complex were determined by the Benesi-Hildebrand, Scott and Ketaalar equations respectively. The results show that copolymerization of MA:VCL system was preceded via alternating copolymerization mechanism. Obtained functional alternating copolymer and copolymer/O-MMT nanostructures were characterized by XRD and TEM.     

Graphene and its nanocomposites used as an active materials for supercapacitors

This review article investigates the hot topics by presenting the latest advances on graphene-based nanostructures for supercapacitors. In literature, many scientists have studied the nanomaterials and combination of conducting polymers in supercapacitor (SC) devices. The main aim of this review article is to present the higher capacitance, and higher power and energy density performances of the SC devices, which includes the active materials of carbon-based materials, metal oxides, conducting polymers, nanocomposites, etc. Many conventional techniques have already been used such as photolithography, inkjet printing, etc. Each of these methods has specific advantages and some drawbacks, with some working better in different environments. Among various nanoscaled materials, nanocrystal oxides of transition metals play an important role in advanced materials development. In addition to design of active material, symmetric and asymmetric supercapacitor device fabrication is also directly effect to obtain a higher capacitance, energy and power density performances. Therefore, this review article focuses on supercapacitor technology in new developments, such as design of active materials, device fabrication, etc.