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Two-dimensional mesoporous hexagonal carbon sheets (MHCSs) have been prepared via a chemical vapor deposition method employing mesoporous Mg(OH)

Hybrid supercapacitors (SCs) made of carbon–metal oxide composites are devices which combine the advantages of electric double layer capacitors and pseudocapacitors viz high energy density, high power density and high cyclability. This is best achieved when the pseudocapacitive components are uniform in size and distribution on the conducting carbon support. Electrodes mats, fabricated from carbonized electrospun fibers generated from solutions of polyacrylonitrile (PAN) as the carbon source, cobalt (III) acetylacetonate as a metal oxide precursor, and polymethacrylic acid (PMAA) as a metal oxide precursor carrier were utilized in coin cell SCs. Fibers without the PMMA carrier were prepared for comparison. XRD and TGA showed conversion of the cobalt precursor to a mixture of cobalt and cobalt oxide (Co3O4). When the PMAA carrier was used, specific capacitance increased from 68 F g−1 in PAN-Co3O4 to 125 F g−1 in PAN-PMAA-Co3O4. The addition of PMAA to the system results in better uniformity, accessibility and dispersion of metal and metal oxide particles. Due to the relatively low surface area of carbonized samples, Co3O4 nanoparticles are the primary contributors to charge storage. The fabricated fibers show an energy density of 8.9 at 750 W kg−1, which is twice that of the fibers made without PMAA.

Lanthanum hydroxide nanorods were employed as both a template and catalyst for carbon synthesis by chemical vapor deposition. The resulting carbon possesses hollow nanorod shapes with graphitic walls. The hollow carbon nanorods were interconnected at some junctions forming a mazelike network, and the broken ends of the tubular carbon provide accessibility to the inner surface of the carbon, resulting in a surface area of 771 m2/g. The hollow carbon was tested as an electrode material for supercapacitors. A specific capacitance of 128 F/g, an energy density of 55 Wh/kg, and a power density of 1700 W/kg at 1 A/g were obtained using the ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, as the electrolyte.

An acrylonitrile based copolymer, poly(acrylonitrile-co-itaconic acid), P(AN-co-IA) was synthesized with different amounts of itaconic acid (IA) to study in situ porogen activity of IA to produce porous carbon nanofibers (CNFs) without any subsequent physical or chemical activation. The concept developed here avoids unnecessary and complex extra activation steps when fabricating CNFs which ultimately lead to lower char yields and uncontrollable pore sizes. The ability of COOH in P(AN-co-IA) to act as an in situ porogen by releasing CO2 during carbonization was verified by simultaneous thermogravimetric analysis-mass spectrometry compared to polyacrylonitrile (PAN). The specific surface area of PAN CNFs (27 m2 g-1) dramatically increases to 1427 m2 g-1 upon addition of ∼8 wt% IA without any ex situ activation. Furthermore, we confirmed that the porosity could be tuned by changing the IA content. The best electrochemical performance was obtained from the copolymer containing ∼8 wt% of IA, which gives a maximum specific capacitance of ∼93 F g-1 at a scan rate of 10 mV s-1 and energy density of ∼46 Wh kg-1 at 1 A g-1 without any subsequent physical or chemical activation.

Carbon nanofibers with high surface area have become promising electrode materials for supercapacitors because of their importance in increasing energy density. In this study, a high free volume polymer, 6FDA-DAM:DABA (6FDD) was blended with polybenzimidazole (PBI) in different ratios to obtain different compositions of PBI/6FDD immiscible polymer blends. Freestanding nanofiber mats were obtained via electrospinning using blend precursors dissolved in N,N-dimethylacetamide (DMAc). Subsequently, carbonization, followed by CO2 activation at 1000 °C was applied to convert the fiber mats into porous carbon nanofibers (CNFs). The addition of 6FDD shows significant effects on the microstructure and enhancement of the surface area of the CNFs. The obtained CNFs show specific surface area as high as 3010 m2 g−1 with pore sizes comparable to those of the electrolyte ions (PYR14TFSI). This provides good electrolyte accessibility to the pore of the carbon materials resulting in enhanced energy density compared to the CNFs obtained from pure PBI. Electrodes derived from PBI:6FDD (70 : 30) exhibited outstanding supercapacitor performance in coin cells with a specific capacitance of 142 F g−1 at the scan rate of 10 mV s−1 and energy density of 67.5 W h kg−1 at 1 A g−1 (58 W h kg−1 at 10 A g−1) thus demonstrating promising electrochemical performance for high performance energy storage system.

Thermally sensitive tetramethylammonium oxalate (TMAO) is incorporated as an in situ porogen into freestanding nonwoven nanofibers of polyacrylonitrile (PAN) produced by electrospinning. Supercapacitor electrode materials are prepared by a series of thermal treatments on these fibers, including stabilization followed by a single step carbonization and CO2 activation. The specific surface areas of the resultant carbon nanofibers (CNFs) are controlled by varying the amounts of TMAO in the precursor fibers. The electrochemical properties of the carbon nanofibers are characterized by cyclic voltammetry and galvanostatic charge–discharge tests. The highest surface area (2663 m2 g−1) and best electrochemical performance are obtained from PAN containing 0.1 wt% of TMAO (T10), which gives a maximum specific capacitance of 140 F g−1 at a scan rate of 10 mV s−1 in comparison to CNFs from PAN alone, which yielded only 90 F g−1. At a discharge current density of 1 A g−1, the obtained energy and power densities are 68 Wh kg−1 and 1.7 W kg−1, respectively, with capacitance retention of 80% after 1000 cycles.

Flexible, free standing and binder-free electrodes were fabricated by electrospinning from a series of lignin: polyvinyl alcohol (PVA) polymer blends, followed by heat treatment. PVA has the dual function of facilitating the electrospinning of lignin and acting as a sacrificial polymer. Upon stabilization, carbonization and CO2 activation, carbon nanofibers (ACNF) derived from the lignin:PVA 80:20 blend displayed a high surface area of 2170 m2 g-1 and a mesopore volume of 0.365 cm3 g-1. ACNFs derived from all the compositions show high degrees of graphitization based on Raman analysis. Pyr14TFSI ionic liquid (IL), modified by mixing with propylene carbonate and ethylene carbonate to reduce the viscosity and increase the ionic conductivity, was used as a high-performance electrolyte. The resulting IL mixture exhibited a four-fold increase in ionic conductivity compared to the neat IL Coin cell supercapacitors using electrodes derived from lignin:PVA 80:20 blends and this electrolyte displayed 87 F g-1 specific capacitance and 38 Wh kg-1 energy density which is the highest reported energy density for lignin:PVA blends to date.

Wrinkled mesoporous silica (WMS) has been shown to be a promising material for catalysis and drug delivery. The WMS possesses a unique wrinkled structure with conical shaped pores radiating from the center to the surface of each particle. Lanthanum oxide was supported on wrinkled mesoporous silica as a hard template for the synthesis of graphitic carbon. The resulting carbon material retains the unique wrinkled structure and has high surface area (∼879 m2/g) as well as graphitic walls which were observed by transmission electron microscopy. The amount of La loaded onto the silica support plays a key role in the formation of the mechanically and chemically stable carbon material.

For the first time, porous organic polymers (POPs) based on the smallest buckybowl, corannulene (BB-POPs) have been synthesized. Three POPs were synthesised via Sonogashira co-polymerization of 1,2,5,6-tetrabromocorannulene and alkyne linkers. BB-POP-3 exhibits the highest surface area (SABET = 560 m2 g−1) and CO2 adsorption of 11.7 wt%, while they retain the redox properties of corannulene.

Polymer blends yield carbon materials with superior performances for supercapacitor applications since blending can lead to controlled and fine pore architectures. In this study, a supercapacitor electrode material derived from an immiscible polymer blend comprising polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA) was investigated. PAN was used as the carbonizing polymer while PMMA was used as the sacrificial polymer. The polymer blend solutions in DMF were electrospun to obtain freestanding nanofiber mats. The resulting mat was carbonized and activated by CO2 at 1000 °C to obtain porous carbon nanofibers (CNFs), as PAN converts to carbon and the sacrificial polymer decomposes creating pores. We demonstrated that the pore sizes can be tuned by varying the amount of PMMA loading in the blend compositions. PAN : PMMA (95 : 5), was found to be the optimum blend composition, affording the highest surface area of 2419 m2 g−1, higher degree of graphitization, higher carbon yield and lower charge transfer resistance among the blend compositions studied. Furthermore, the PAN : PMMA (95 : 5) CNFs showed the highest capacitance of 140 F g−1 and energy densities of 67 W h kg−1 at 3.5 V and 101 W h kg−1 at 4 V in an ionic electrolyte (EMITFSI) and also showed good cycling stability with 85% capacitance retention after 1000 cycles.

The MIL-53 metal–organic framework (MOF) is known to change reversibly from an open-pore framework (MIL-53-ht) to a closed-pore framework (MIL-53-lt) depending on the temperature, pressure, or guest molecules absorbed. Three frameworks of the additive, MIL-53-as synthesized (MIL-53-as), MIL-53-ht, and MIL-53-lt, were prepared, characterized, and combined with Matrimid® to form mixed-matrix membranes (MMMs) for gas separations. The MIL-53-ht/Matrimid® MMMs exhibited higher values of permeability compared to Matrimid® as well as an increased CO 2 /CH 4 selectivity suggesting that the open-pore MIL-53 framework was maintained in the polymer matrix. In addition to higher permeability values, MIL-53-as/Matrimid® MMMs showed higher selectivity for gas pairs with kinetic diameters differing by ⩾0.5 A, including H 2 /O 2 , CO 2 /CH 4 , H 2 /CH 4 , and H 2 /N 2 , suggesting the presence of excess benzene dicarboxylic acid molecules within the pores that reduced its diameter enabling the material to discriminate between smaller and larger gases. MIL-53-lt did not retain its closed-pore form in the MMM. Rather, it irreversibly converted to the open-pore form (MIL-53-ht) due to the exchange of water present in the MIL-53 pores with chloroform solvent molecules during membrane casting and to pore penetration and confinement by Matrimid® polymer chains. This finding, that a polymer matrix stabilizes a MOF pore architecture within an MMM, is significant in that the desired selectivity of a MOF-MMM system may be achievable.

Lignin was blended with polyacrylonitrile (PAN) in different ratios and fabricated into carbon nanofiber electrodes by electrospinning followed by thermal stabilization, carbonization and subsequent activation by CO2 of the carbonized mats. These carbon fiber electrodes exhibit high surface area, high mesoporosity, high graphitic content and high electrical conductivity. Activated carbon nanofiber mats derived from PAN:Lignin 70:30 blends display a surface area of 2370 m2 g-1 with 0.635 cm3 g-1 mesopore volume. These results are due to the selective partial removal of carbonized lignin during the activation step. Coin cell supercapacitors employing these electrodes exhibit 128 Fg-1 specific capacitance, 59 Wh kg-1 energy density and a 15 kW kg-1 power density when operated at 3.5 V using an ionic liquid electrolyte. Since lignin is an inexpensive, abundant, and green polymer, incorporating it into carbon blends enhances the scalability of such materials in energy storage applications.

Electrochemical double layer capacitors (EDLCs) utilize electrodes with high surface area to achieve high-energy storage capability. In this study, flexible and freestanding carbon nanofibers derived from PIM-1, a microporous polymer with high free volume, were prepared by pyrolysis of the electrospun polymer. A BET surface area of 546 m2 g−1 was obtained upon carbonization of the electrospun PIM-1 fibers. After further heat treatments such as steam-activation and annealing, the surface area increased to 1162 m2 g−1. These carbon fibers were directly used as electrodes without the use of binders in a coin cell (CR2032) configuration and were characterized by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The activated and annealed fibers gave a specific capacitance of 120 F g−1 at a scan rate of 10 mV s−1 using 1,3-ethylmethylimidizaolium bis(trifluoromethanesulfonyl)imide as the ionic liquid electrolyte. From the galvanostatic charge–discharge test, the supercapacitor exhibited energy and power densities of 60 W h kg−1 (active material) and 1.7 kW kg−1, respectively, at a current density of 1 A g−1. High power application of this device was demonstrated by its 77% retention of the energy density (47 W h kg−1) at a higher discharge current density of 5 A g−1.

The demand for cost-efficient separations requires membranes with high gas flux and high selectivity which opens the path for further improvements. Mixed matrix membranes (MMMs) made from 33.3 wt % ZIF-8 in 6FDA-durene were tested at 35 °C and 3.5 atm. At 33.3 wt % loading of ZIF-8, H2, N2, O2, and CH4 gas permeabilities increased approximately 400%. Cross-linking the surface of this MMM, by reacting with ethylenediamine vapor, yielded a 10-fold increase in H2/CO2, H2/N2, and H2/CH4 selectivities with respect to 6FDA-durene, preserving 55% of the H2 permeability of 6FDA-durene. The permselective properties of the cross-linked skin of the MMM fall above the most recent permeability–selectivity trade-off lines (2008 Robeson upper bounds) for H2/CO2, H2/N2, and H2/CH4 separations. To the best of our knowledge, this is the first example of a cross-linked ZIF/polymer MMM for gas separation.

Porous carbon nanofibers were prepared by electrospinning blend solutions of polybenzimidazole/poly-L-lactic acid (PBI/PLLA) and carbonization. During thermal treatment, PLLA was decomposed, resulting in the creation of pores in the carbon nanofibers. From SEM images, it is shown that carbon nanofibers had diameters in the range of 100-200 nm. The conversion of PBI to carbon was confirmed by Raman spectroscopy, and the surface area and pore volume of carbon nanofibers were determined using nitrogen adsorption/desorption analyses. To investigate electrochemical performances, coin-type cells were assembled using free-standing carbon nanofiber electrodes and ionic liquid electrolyte. cyclic voltammetry studies show that the PBI/PLLA-derived porous carbon nanofiber electrodes have higher capacitance due to lower electrochemical impedance compared to carbon nanofiber electrode from PBI only. These porous carbon nanofibers were activated using ammonia for further porosity improvement and annealed to remove the surface functional groups to better match the polarity of electrode and electrolyte. Ragone plots, correlating energy density with power density calculated from galvanostatic charge-discharge curves, reveal that activation/annealing further improves energy and power densities.

Carbon nanofibers (CNFs) were fabricated by thermal treatment of electrospun nanofibers obtained from precursor blends of polybenzimidazole (PBI) and Matrimid®. The microcarbon structures of CNFs obtained from PBI, and the 50:50 and 75:25 blends were studied using XRD and Raman spectra. Nitrogen adsorption/desorption measurements revealed that surface area and porosity of CNFs increased with an increase in Matrimid® content. Electrochemical performance of these CNF electrodes was studied for their application in energy storage devices. The CNFs from the PBI/Matrimid® (75:25)-precursor blend showed the lowest electrochemical impedance, and highest specific capacitance (111 F/g) and energy and power densities of 24 and 6 kW/kg, respectively. Steam activation and annealing further enhanced the performance resulting in a specific capacitance of 126 F/g, and energy and power densities of 49 and 7 kW/kg, respectively.

In this study, we explore the effect of the dialkoxy and dithioalkoxy side chains on the benzo [1,2-b:4,5-b′]dithiophene (BDT) unit by comparing the O-BDT homopolymer (O-PBDT), S-BDT homopolymer (S-PBDT), and S-BDT-alt-O-BDT copolymer (SO-PBDT) by computational calculations and experimental results. The polymers were prepared by Pd-catalyzed Stille coupling. Additionally, hole mobility and film morphology were studied by fabricating organic field effect transistors (OFETs) and using TappingMode AFM, respectively. The photovoltaic properties of the polymers were measured from fabricated PSC devices. The replacement of the alkoxy (−OR) groups with thioalkoxy (−SR) groups lowered the HOMO energy level of the conjugated polymers from 5.31 to 5.41 eV, and consequently enhanced Voc, while still preserving the excellent properties offered by the BDT-based polymers. Especially, high Voc of 0.99 V was achieved from S-PBDT polymer based PSC with up to 4.0% of PCE, which is one of the highest efficiencies reported f...

Carbon nanofibers (CNFs) are promising electrode materials for electrochemical double layer capacitors due to their high porosity and electrical conductivity. CNFs were prepared by electrospinning and subsequent thermal treatment of a new precursor polymer, 6FDA-durene, without the addition of pore generating agents. The conversion of precursor nanofibers into CNFs was confirmed using Raman spectroscopy. CNFs were activated and annealed, and nitrogen adsorption/desorption measurements were conducted to determine surface area and porosity. These activated/annealed CNFs were used as binderless electrodes in coin cells with an ionic liquid electrolyte. The devices displayed a specific capacitance of 128 F g−1, an energy density of 63.4 Wh kg−1 (at 1 A g−1), and a power density of 11.0 KW kg−1 (at 7 A g−1).

Low efficiencies and costly electrode materials have limited harvesting of thermal energy as electrical energy using thermo- electrochemical cells (or "thermocells"). We demonstrate thermocells, in practical configurations (from coin cells to cells that can be wrapped around exhaust pipes), that harvest low-grade thermal energy using relatively inexpensive carbon multiwalled nanotube (MWNT) electrodes. These electrodes provide high electrochemically accessible surface areas and fast redox-mediated electron transfer, which significantly enhances thermocell current generation capacity and overall efficiency. Thermocell efficiency is further improved by directly synthesizing MWNTs as vertical forests that reduce electrical and thermal resistance at electrode/substrate junctions. The efficiency of thermocells with MWNT electrodes is shown to be as high as 1.4% of Carnot efficiency, which is 3-fold higher than for previously demonstrated thermocells. With the cost of MWNTs decreasing, MWNT-based thermocells may become commercially viable for harvesting low-grade thermal energy.

The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750 nm. Activated carbon fibers (ACFs) derived by stabilization, carbonization and steam activation at 700, 800, and 900 °C of the PAN/pitch electrospun fibers for 60 min were investigated as electrodes for supercapacitors. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877 m 2 g -1 and the specific capacitance from 75.5 to 143.5 Fg -1 , depending on the activation conditions. Electrodes from the electrospun web activated at 900 °C exhibited a particularly quick response showing a high frequency of 5.5 Hz at a phase angle of-45° of the impedance spectroscopy.

Novel polysilsesquioxane (R–Si–(O)1.5) PEMs with highly cross-linked Si–O backbones and pendant organic side chains comprising propylsulfonic or ethylphosphonic acid groups, were prepared via sol-gel polymerization. The inorganic component provides thermal/mechanical/chemical stability while the organic component gives flexibility and proton-conducting properties. The propylsulfonic acid membranes exhibited proton conductivities (σ) up to 10−2 S/cm at high relative humidities and temperatures, while the ethylphosphonic acid membranes showed lower proton conductivities but higher thermal stabilities. Preliminary results for the propylsulfonic acid membranes in direct methanol fuel cell (DMFC) performance are reported.

The polymerization to polyaniline nanofibers was carried out in an aqueous system using aniline, 1 M HCl. and ammonium peroxydisulfate (APS) with additional use of sodium hypochlorite solution as a co-oxidant. The addition of sodium hypochlorite solution was made either before or after the addition of APS. This new method always produces polyaniline nanofibers with long length. Additional advantages of this new method are discussed. The effect of aniline concentration, hypochlorite concentration, different acid use, reaction temperature, and both aniline and hypochlorite purity on morphology and electrical property of the nanofibers synthesized by this new method was investigated.

A carbon aerogel was prepared by carbonizing a resorcinol−formaldehyde polymer gel at 800 °C. Nitrogen adsorption shows the obtained carbon aerogel has both micropores (0.54 nm) and mesopores (2.14 nm). Matrimid mixed-matrix membranes containing the carbon aerogels were successfully prepared and evaluated for the permeation of H2, N2, O2, CH4, CO2, and gas mixtures. The ideal selectivity of H2/N2, CO2/CH4, and O2/N2 gas pairs increased from 79.6, 34.5, and 6.6 for pure Matrimid to 111, 47.8, and 9.1 at 20% loading, respectively. These results suggest that the polymer chains can penetrate the carbon mesopores to achieve good contact between the carbon aerogel and Matrimid, while the micropores may provide size and shape selectivity.

Mesoporous benzene silica (MBS) composites were synthesized and their physical properties were investigated. Three different MBS samples were prepared using octadecyltrimethylammonium chloride, vitamin E TPGS, and Pluronic 123 block copolymer as structure directing agents, respectively. The template extracted MBS samples were heat treated to 1000 °C under argon to carbonize the benzene rings in the pore walls to form a graphitic structure. These carbon/SiO 2 composites were treated with HF to dissolve the SiO 2 . The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. The MBS samples 1–3 had pore sizes of 2.73, 3.35, and 5.52 nm, respectively. The carbon materials CBS samples 1–3 prepared in this study were microporous ( 2 /g.

Electrospinning has been used to produce mesoporous metal oxide fibers with diameters in the nanometer to submicron range. The mesoporous metal oxide fibers include TiO 2 , Ta 2 O 5 , TaNbO 5 as well as the crystalline Nb 2 O 5 and VTiO 2 . The structure directing agents Pluronic P-123 [(EO) 20 –(PO) 70 –(EO) 20 ] and Brij 76 [C 18 H 37 (OCH 2 OCH 2 ) 10 OH], were used to generate the mesopores in the fibers. The fibers were characterized by XRD, scanning electron microscopy and surface area analysis. In the case of TiO 2 and Ta 2 O 5 the first examples of mesoporous molecular sieve papers were generated. The papers and fibers remain intact even after heating to 900 °C.

Mesoporous SBA-15/polyaniline composites were synthesized and their physical properties were investigated. The polyaniline was polymerized inside the pores of the mesoporous material by a post-synthesis process as well as an in one step process during the preparation of the molecular sieve. These materials were characterized by X-ray diffraction, scanning electron microscopy and nitrogen adsorption. The composite polyaniline/SBA-15 was electrically insulating (dc conductivity ∼10 −8 S/cm) and produced proton conductivities of up to 10 −2 S/cm when doped with HCl.

Tungstosilicate mesoporous materials (WMM) were synthesized using the ionic surfactant cetyltrimethylammonium bromide (C 16 H 33 N + (CH 3 ) 3 Br − , CTMABr) and non-ionic surfactants, including C 12 H 25 (OCH 2 CH 2 ) 10 OH (Brij 22, C 12 EO 10 OH), C 16 H 33 (OCH 2 CH 2 ) 10 OH (Brij 56, C 16 EO 10 OH), and C 18 H 37 (OCH 2 CH 2 ) 10 OH (Brij 76, C 18 EO 10 OH). Using CTMABr, the highest W/Si ratio achieved for the molecular sieve product was 0.03. The proton conductivity ranged from 0.5 to 2.2 × 10 −2 S/cm, where the highest conductivity was observed with the H 3 PO 4 based preparation. Non-ionic surfactants produced materials with a W/Si ratio as high as 0.05 without any dense WO 3 impurities. These samples showed thicker pore walls (39 A), higher thermal stability, and higher proton conductivity (4.0 × 10 −2 S/cm). The WMMs were also employed to make a composite membrane with linear polyethyleneimine (PEI)-3-glycidoxypropyl-trimethoxysilane (GLYMO)-bis(trifluoromethanesulfonyl)imide (HTFSI). At 100 °C and 100% relative humidity, the composite membrane with 30 wt.% calcined (at 500 °C) WMM showed the highest conductivity of 6.1 × 10 −2 S/cm. At 130 °C and 20% relative humidity, the highest conductivity of 6.4 × 10 −3 S/cm was obtained for the composite membrane with 30 wt.% as-synthesized WMM.

The electronic dopants, like tetrafluorocyanoquinodimethane (F 4 –TCNQ) molecules, used for p-doping of hole transport layers in organic light-emitting diodes (OLEDs) are found to quench the electroluminescence (EL) if they diffuse into the emissive layer. We observed EL quenching in OLED with F 4 -TCNQ doped N,N′-diphenyl-N′N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine hole transport layer at large dopant concentrations, >5%. To separate the effects of exciton–dopant quenching, from exciton–polaron quenching we have intentionally doped the emissive layer of (8-tris-hydroxyquinoline) with three acceptors (A) of different electron affinities: F 4 -TCNQ, TCNQ, and C 60 , and found that C 60 is the strongest EL-quencher, while F 4 -TCNQ is the weakest, contrary to intuitive expectations. The new effects of charge transfer and usually considered energy transfer from exciton to neutral (A) and charged acceptors (A − ) are compared as channels for non-radiative Ex–A decay. At high current loads the EL quenching is observed, which is due to decay of Ex on free charge carriers, hole polarons P + . We consider contributions to Ex–P + interaction by short-range charge transfer and describe the structure of microscopic charge transfer (CT)-processes responsible for it. The formation of metastable states of ‘charged excitons’ (predicted and studied by Agranovich et al. Chem. Phys. 272 (2001) 159) by electron transfer from a P to an Ex is pointed out, and ways to suppress non-radiative Ex–P decay are suggested.

There is growing interest in new ways to configure titanium dioxide (TiO 2 ) as new applications emerge such as in photovoltaics and catalysis. A method has been developed for the preparation of mesoporous TiO 2 fibers using electrostatic deposition. The mesoporous metal oxide fibers were prepared using Pluronic 123 as the template. The fibers contain anatase crystallized in the pore walls which transforms to rutile upon calcination above 800 °C. The electrospun fibers were evaluated for the photodecomposition of phenol and formic acid.

The process of electrospinning, which produces fibers in the nanometer to micron range under the influence of high voltages, has been widely studied to produce polymer and textile fibers. Mesoporous molecular sieve fibers have been produced in our lab, and this technique was extended to produce an interwoven mesh of polymer-molecular sieve composite fibers. The electroluminescent polymer MEH-PPV and molecular sieve SBA-15 were used to produce the composite fibers. An interesting aspect of these composites is that the fluorescence of MEH-PPV is blue shifted in the composites. The composites have been characterized by microscopy, vibrational spectroscopy, and fluorescence measurements.

Electrospun fibers comprising mesoporous molecular sieve materials are described. In an aspect of the invention, fibers are electrospun from a conducting solution to which a high voltage electric current is applied. The apparatus includes in one aspect one or more conducting solution introduction devices for providing a quantity of conducting solution, said conducting solution introduction devices being electrically charged thereby establishing an electric field between said conducting solution introduction devices and a target, and means for controlling the flow characteristics of conducting solution from said one or more conducting solution introduction devices.

Electrochromic devices composed of laminated polymer layers, as the working electrode, and vanadium pentoxide, as the counter electrode, were prepared and evaluated. Three different laminate systems were investigated using various combinations of poly(3,4-ethylenedioxythiophene), poly(N-methylpyrrole), and polyaniline as the active electrochromes. The color change of the laminate devices was measured using spectrocolorimetric techniques and analyzed using Commission Internationale de l'Eclairage 1931 (x, y)-chromaticity coordinates. The device's observed colors in their fully doped and dedoped states are found to be linearly dependent on the color coordinates of the two individual polymers that comprise the laminate.

In this study, we have explored the first use of the siliceous MCM-41 molecular sieve as an additive to enhance the gas permeability characteristics of a high-performance polysulfone. For all gases...

The template synthesis of copper(II) phthalocyanine by the condensation of dicyanobenzene within the supercages of Cu(II) exchanged X and Y type zeolites was studied using differential scanning calorimetry. The exotherms for intrazeolite and surface complexation have been resolved. These thermal events exhibit a dependence on the copper loading and hydration level which has been interpreted as a pressure effect.

The standard heterogeneous electron-transfer rate constants between substrate gold electrodes and either ferrocene or pentaaminepyridine ruthenium redox couples attached to the electrode surface by various lengths of an alkanethiol bridge as a constituent of a mixed self-assembled monolayer were measured as a function of temperature. The ferrocene was either directly attached to the alkanethiol bridge or attached through an ester (CO(2)) linkage. For long bridge lengths (containing more than 11 methylene groups) the rate constants were measured using either chronoamperometry or cyclic voltammetry; for the shorter bridges, the indirect laser induced temperature jump technique was employed to measure the rate constants. Analysis of the distance (bridge length) dependence of the preexponential factors obtained from an Arrhenius analysis of the rate constant versus temperature data demonstrates a clear limiting behavior at a surprisingly small value of this preexponential factor (much lower than would be expected on the basis of aqueous solvent dynamics). This limit is independent of both the identity of the redox couple and the nature of the linkage of the couple to the bridge, and it is definitely different (smaller) from the limit derived from an equivalent analysis of the rate constant (versus temperature) data for the interfacial electron-transfer reaction through oligophenylenevinylene bridges between gold electrodes and ferrocene. There are a number of possible explanations for this behavior including, for example, the possible effects of bridge conformational flexibility upon the electron-transfer kinetics. Nevertheless, conventional ideas regarding electronic coupling through alkane bridges and solvent dynamics are insufficient to explain the results reported here.

The electrospinnability of pitch was improved by blending in a solution of polyacrylonitrile (PAN) resulting in the reduction of the average fiber diameter from 2000 to 750 nm. The compositions showing good spinnability are proposed within the soluble concentrations in the ternary phase diagram of the PAN–pitch-solvent, which contains lower concentration of the pitch. Activated carbon fibers were derived by stabilization, carbonization and steam activation at 700, 800, 900 and 1000 °C of the PAN/pitch electrospun fibers. The Brunauer, Emmett, Teller (BET) specific surface area ranged from 732 to 1877 m 2 /g.

A new dialkylthio benzo[1,2-b:4,5-b']dithiophene (S-BDT) was designed and synthesized and the polymer S-PBDT was prepared by a Stille coupling reaction. A high open-circuit voltage (V(oc)) of up to 0.99 V was achieved in polymer solar cells with PCBM.

A linear polythiophene, poly[bis(5‘,2‘-bithiophene-2-yl)]dimethylsilane, which incorporates silyl bridges in the backbone was synthesized to tailor the electrochromic properties. Solid-state electrochromic devices comprised of this polymer as the active material were fabricated and were analyzed following CIE L*a*b* formalism. By limiting the effective conjugation in the polymer, its electrochromic properties were deliberately altered to produce a yellow to green color change from its neutral to oxidized state.

The synthesis of 2-phenylthieno[3,4-b]thiophene was carried out in two steps from 3,4-dibromothiophene and phenylacetylene. Electropolymerization of this monomer affords a novel low band gap (Egap) polymer that was characterized by cyclic voltammetry and electrochemistry. An Egap of ca. 0.85 eV was observed, which is among the lowest reported to date for any conductive polymer.

Using solution spinning, which involves an intermediate gel-state, we obtained exceptionally strong carbon nanotube fibers that are tougher than either spider silk or any fiber used for mechanical reinforcement. We use these fibers to make 100 micron diameter supercapacitors and electronic textiles. Per weight, the energy needed to break these fibers is about 4× higher than spider dragline silk and 20× higher than steel wire. This article describes this advance, comparisons with the prior art, potential applications, and present barriers for large volume applications.

Das cyclische Voltammogramm der Titelverbindung (I) zeigt Einelektronen-Reduktionsstufen bei 0.79 und 0.14 V (gegen die SCE).

The spectral dependence of the far-infrared photoconductivity of TTF-TCNQ at low temperatures shows an interband transition with an edge at approximately 22 meV. We associate this gap with the d.c. conductivity maximum near 70 K, and suggest that at least two distinct mean-field transition temperatures are important for the observed electrical and magnetic properties of the material.

Measurements are presented of electrical potential values on single crystals of TTF-TCNQ which show an extraordinary apparent conductivity maximum near 70 K. The observed voltages in these anisotropic crystals are shown to be unusually sensitive to the points at which electrical contact is made. Our anomalous apparent conductivities can be understood in terms of the strong temperature dependence of the electrical anisotropy which is found, through measurements on several samples, to peak near 70 K.

The phenoxachalcogenines have been studied as donors towards 7,7,8,8-tetracyanoquinodimethane. For the 1:1 complexes studied, the equilibrium constants, K, vary over the range 4–6; the enthalpy, ΔH0, is about −2.0 kcal/mol; the free energy, ΔG0, is −1.4 to −1.0 kcal/mol, and the entropy change, ΔS0, is −7.3 to −3.5 eu. The entropy change is greatest in the case of the dibenzo-1,4-dioxane – 7,7,8,8-tetracyanoquinodimethane charge-transfer complex. This is attributed to the planarity of the dibenzo-1,4-dioxane molecule. The extinction coefficient, εc, for the series studied varies from 115 to 230, and no regularity in the trend has been noted.The lack of any significant changes (with change in the chalcogen atom) in the thermodynamic values for the phenoxachalcogenine – 7,7,8,8-tetracyanoquinodimethane charge-transfer complexes is interpreted in terms of a similar π to π type interaction involving a delocalized π orbital of the phenoxachalcogenine rather than a localized n orbital of the hetero atom.The room temperature four-probe dc conductivities of single crystals of PSe–TCNQ and PS–TCNQ were found to be 4 × 10−8 and 3 × 10−7 ohm−1 cm−1, respectively.

The complex microwave conductivities of the organic salts TTF-TCNQ and ATTF-TCNQ show a metal-to-insulator transition near 60 K and distinguish these materials from the class of disordered one-dimensional conductors. The data show no evidence for the high-temperature superconducting fluctuations recently proposed by Heeger and co-workers.