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This article examines doctoral graduate education programs in chemistry at the University of Texas, Dallas. Authors point out that the programs offer a novel approach by focusing on problem-solving skills and real world experience in preparing students for industrial chemistry careers.

This research focused on the detailed analytical characterization of the poultry litter-derived biochar followed by its conversion into electrodes for supercapacitor application. Biochar was prepared from poultry waste by pyrolysis at 600 °C for 3hours and activated it by mixing with potassium hydroxide and re-pyrolyzed at the same temperature for 1hour. Both the biochar and activated biochar were analyzed using Scanning Electron Microscopy (SEM), Infrared spectroscopy (IR), Time of Flight – Secondary Ion Mass Spectroscopy (ToF-SIMS), and X-ray Photoelectron Spectroscopy (XPS), and Brunauer-Emmett- Teller (BET) analyses. SEM analyses suggested that the biochar’s surface became more porous and homogeneous after activation with potassium hydroxide. The specific surface area of biochar increased by more than 200 folds to 814 m2g-1after KOH-activation confirmed from BET analysis. IR indicated the activated biochar contained sulfur- and phosphorous-functional groups but few or no oxygen-functional groups. The decrease in oxides of nitrogen, sulfur, and phosphorous was also observed in ToF-SIMS analysis. In spite of the decrease of oxides, the surface oxygen concentration (At%) increased from 42.3% to 46.6% after activation and was assumed to be present as C-O corroborated by XPS. The specific capacitance of activated biochar calculated from galvanostatic charge-discharge is 152F/g attributed to its hierarchical porosity, heteroatoms presence, and hydrophilicity. This research is expected to contribute towards the sustainable management of agricultural wastes.

A novel symmetrical alkylsulfonyl-substituted poly(phenylenevinylene) derivative, poly [2,5-bis-(2′-ethylhexylsulfonyl)-1,4-phenylene)vinylene] (SO2EH-PPV), was synthesized via palladium-catalyzed Stille coupling, and its electronic and optical properties were investigated. The novel PPV derivative was characterized by NMR, UV–visible absorption, photoluminescence, gel permeation chromatography, infrared spectroscopy, and cyclic voltammetry (CV). The polymer with Mwof 27 800 and a polydispersity index of 2.6 is readily soluble in common organic solvents, such as THF, chloroform, and toluene. The fluorescence quantum yield of the polymer, determined against rhodamine 6G in dilute aqueous solutions, was 0.95. The HOMO and LUMO levels of SO2EH-PPV were calculated to be −6.0 and −3.61 eV, respectively. The results obtained by CV suggest that SO2EH-PPV is a strong electron acceptor polymer. Single layer stable polymer light-emitting diode devices with the configuration of (ITO/PEDOT:PSS/SO2EH-PPV polymer/Al) were fabricated exhibiting a green light emission.

Hierarchical porous carbons (HPCs) hold great promise in energy-related applications owing to their excellent chemical stability and well-developed porous structures. Attention has been drawn toward developing new synthetic strategies and precursor materials that permit greater control over composition, size, morphology, and pore structure. There is a growing trend of employing metal–organic frameworks (MOFs) as HPC precursors as their highly customizable characteristics favor new HPC syntheses. In this article, we report a biomimetically grown bacterial-templated MOF synthesis where the bacteria not only facilitate the formation of MOF nanocrystals but also provide morphology and porosity control. The resultant HPCs show improved electrochemical capacity behavior compared to pristine MOF-derived HPCs. Considering the broad availability of bacteria and ease of their production, in addition to significantly improved MOF growth efficiency on bacterial templates, we believe that the bacterial-templated MOF is a promising strategy to produce a new generation of HPCs.

For electrodes in electrochemical double-layer capacitors, carbon nanofibers (CNFs) were prepared by thermal treatment of precursor polymer nanofibers, fabricated by electrospinning. Poly(acrylonitrile-co-vinylimidazole) (PAV) was employed as a precursor polymer of carbon nanofibers due to the effective cyclization of PAV polymer chains during thermal treatment compared to a typical precursor, polyacrylonitrile (PAN). PAV solutions with different comonomer compositions were prepared and electrospun to produce precursor nanofibers. Surface images obtained from scanning electron microscopy showed that their nanofibrous structure was well preserved after carbonization. It was also confirmed that electrospun PAV nanofibers were successfully converted to carbon nanofibers after the carbonization step by Raman spectroscopy. Carbon nanofiber electrodes derived from PAV showed higher specific capacitances and energy/power densities than those from PAN, which was tested by coin-type cells. It was also shown that PAV with an acrylonitrile/vinylimidazole composition of 83:17 is most promising for the carbon nanofiber precursor exhibiting a specific capacitance of 114 F/g. Their energy and power density are 70.1 Wh/kg at 1 A/g and 9.5 W/kg at 6 A/g, respectively. In addition, pouch cells were assembled to load the higher amount of electrode materials in the cells, and a box-like cyclic voltammetry was obtained with high capacitances.

This study performs a comprehensive investigation to objectively analyze the effects of various carbon nanomaterials using as conductive additives (5 wt%) in activated carbon (AC) based electrodes for electrical double-layer capacitors (EDLCs). A variety of carbon nanomaterials including carbon black (CB), single-walled carbon nanotubes (SWCNT), graphene nanoplatelets (GNP), fullerenes (C60), and activated carbon nanofibers (ACNF) are considered in this work as they provide a diverse combination of intrinsic properties such as specific surface area, conductivity, micro-mesoporous structures, and geometry of nanomaterials. These additives are incorporated into freestanding carbon electrodes, and their EDLC performance in a neutral aqueous electrolyte is investigated by means of electrochemical measurements. The findings from this work provide useful insight into how the properties of various carbon nanomaterials influence EDLC performance in different aspects such as capacitive behavior, resistivity, performance at different current densities, charge propagation properties, and stability over long-term cycling. The results show that each carbon additive has its own strengths and limitations for different performance parameters considered. The unfavorable material properties of C60 cause a significant decrease in capacitance at high current density, leading to the lowest device performance incorporated with C60 as additives. While GNP and SWCNT show high crystallinity, low ID/IG ratios, the EDLCs still exhibit decreased specific capacitance and moderate energy densities due to their relatively limited specific surface area and high resistivity of the resultant composite electrodes compared to the pristine AC. The CB additives-based samples demonstrate the highest conductivity of dry electrodes and low equivalent series resistance (ESR) in EDLCs. On the other hand, a reduction in capacitance at high current densities and material degradation during long-term cycling are observed for CB samples, which could be attributed to the high dispersibility of CB causing limited interparticle voids and thus increasing diffusion resistance. In contrast, the use of ACNFs significantly reduces the diffusion resistance and improves the cyclic stability compared with CB based samples due to the advantages of larger specific surface area and superior micro-mesoporous structures of ACNFs. In particular, EDLCs with ACNFs demonstrate an increase in specific capacitance and energy density by 99 % and 76 %, respectively compared to CB based EDLCs at a current density of 20 A/g. This work elucidates the complex interplay between carbon nanomaterials using as additives and corresponding EDLC performance. These results provide important information to the community for future development of new energy conversion and storage devices.

Thermoacoustic performance of thin freestanding sheets of carbonized poly(acrylonitrile) and polybenzimidazole nanofibers are studied as promising candidates for thermophones. We analyze thermodynamic properties of sheets using transport parameters of single nanofibers and their aligned and randomly electrospun thin film assemblies. The electrical and thermal conductivities, thermal diffusivity, heat capacity, and infrared blackbody radiation are investigated to extract the heat exchange coefficient and enhance the energy conversion efficiency. Spectral and power dependencies of sound pressure in air are compared with carbon nanotube sheets and theoretical prediction. Despite lower thermoacoustic performance compared to that of CNT sheets, the mechanical strength and cost-effective production technology of thermophones make them very attractive for large-size sound projectors. The advantages of carbonized electrospun polymer nanofiber sheets are in the low frequency domain (<1000 Hz), where the large thermal diffusion length diminishes the thermal inertia of thick (∼200 nm) nonbundled fibers and the high intrinsic thermal conductivity of fibers enhances the heat exchange coefficient. Applications of thermoacoustic projectors for loudspeakers, high power SONAR arrays, and sound cancellation are discussed.

Vanadium oxide nanotubes have shown great promise as electrode materials for energy storage devices. In this study, we report the synthesis of V2O5nanotube (VNT) clusters, which form densely packed radial arrangements of VNTs on high-surface-area carbon fiber fabrics (CF). This was achieved by coating the CF with V2O5by pulsed laser deposition (PLD). Hydrothermal treatment of the PLD films in the presence of excess intercalated V2O5results in formation of well-adhered VNT clusters on the CF. The densely packed VNTs have inner and outer diameters and interlayer distances of ∼24, ∼70, and ∼2.4 nm, respectively. Coin cell type supercapacitors (CR2032) were assembled using VNT-CF as the anode material and electrochemical properties were evaluated.

An immiscible polymer blend comprised of high-performance copolyimide 6FDA-DAM:DABA(3:2) (6FDD) and polybenzimidazole (PBI) was compatibilized using 2-methylimidazole (2-MI), a commercially available small molecule. Membranes were fabricated from blends of 6FDD:PBI (50:50) with and without 2-MI for H2/CO2separations. The membranes demonstrated a matrix-droplet type microstructure as evident with scanning electron microscopy (SEM) imaging where 6FDD is the dispersed phase and PBI is the continuous phase. In addition, membranes with 2-MI demonstrated a uniform microstructure as observed by smaller and more uniformly dispersed 6FDD domains in contrast to 6FDD:PBI (50:50) blend membranes without 2-MI. This compatibilization effect of 2-MI was attributed to interfacial localization of 2-MI that lowers the interfacial energy similar to a surfactant. Upon the incorporation of 2-MI, the H2/CO2selectivity improved remarkably, compared to the pure blend, and surpassed the Robeson’s upper bound. To our knowledge, this is the first report of the use of a small molecule to compatibilize a high-performance immiscible polymer blend. This approach could afford a novel class of membranes in which immiscible polymer blends can be compatibilized in an economical and convenient fashion.

In this study MnO2nanorodes (MNR) were fabricated on reduced graphene oxide (rGO) sheets using a facile hydrothermal synthesis route. As prepared binder free MNR-rGO electrodes exhibited promising electrochemical performance. A similar approach was employed to prepare V2O5nanowire (VNW) on rGO electrodes as anodes for supercapacitor applications. The VNW-rGO anode and MNR-rGO cathode were combined to form a novel hybrid supercapacitor. The hybrid supercapacitor exhibited excellent electrochemical performance reflecting the synergistic effect of combining the MNR-rGO electrode and VNW-rGO electrode. This novel hybrid supercapacitor delivered an energy density of ~15Wh/kg with a specific capacitance of 36.9F/g. These results suggest that the binder free flexible MNR-rGO electrode is a promising cathode material for asymmetric supercapacitors and also for hybrid devices, which incorporate metal oxide anodes.

Poly(p-phenylenevinylene) (PPV) derivatives have long been studied because of their attractive opto- and electroluminescent properties and have potential applications for devices such as light-emitting diodes and photovoltaics. The ability to induce alignment of these PPV derivatives may lead to the enhancement of charge mobility and their efficiency. In this study, uniform nanofibers of poly[2,5-(2′-ethylhexyloxy)]-1,4-phenylenevinylene (BEH-PPV) have been fabricated through the method of electrospinning, and an induced alignment of the polymer fibers was observed through photoluminescence data. This study also focuses on the doping of these fibers with the fullerene derivative, 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)-C61(PCBM), to induce more incidence of donor/acceptor junctions. Composite fibers with up to a 1:2 weight ratio of PCBM/BEH-PPV have been fabricated and exhibited an ability to quench the photoluminescence of BEH-PPV, indicative of charge transfer.

Injecting high electronic charge densities can profoundly change the optical, electrical, and magnetic properties of materials. Such charge injection in bulk materials has traditionally involved either dopant intercalation or the maintained use of a contacting electrolyte. Tunable electrochemical charge injection and charge retention, in which neither volumetric intercalation of ions nor maintained electrolyte contact is needed, are demonstrated for carbon nanotube sheets in the absence of an applied field. The tunability of electrical conductivity and electron field emission in the subsequent material is presented. Application of this material to supercapacitors may extend their charge‐storage times because they can retain charge after the removal of the electrolyte.

No Abstract

Crystal structures for the electron donor DBTTF and its charge-transfer salts with the acceptors TCNQ and 2,5-TCNQF2 are reported. Crystal data for the three systems are as follows: (a) neutral DBTTF; monoclinic, space group P21/c, a=12.082(2) Å, b=3.955(1) Å, c=14.553(2) Å, β=114.36(1)0, V=633.6 Å3; (b) DBTTF-TCNQ; triclinic, space group P1, a=9.215(3) Å, b=10.644(4) Å, c=7.734(2) Å, α=113.32(3)0, β=122.28(2)0, γ=67.66(3)0, V=574.6 Å3; (c) DBTTF-2,5-TCNQF2; triclinic, space group P1, a=8.838(2) Å, b=9.276(2) Å, c=7.794(1) Å, α=101.29(2)0, β=100.89(1)0, γ =107.42(2)0, V=576.6 Å3. The crystal structure of the neutral DBTTF donor is dominated by columns of DBTTF molecules as found in the similar structure of the donor TTF. The crystalline motifs adopted by the TCNQ and 2,5-TCNQF2 salts of DBTTF are composed of columns in which the donor and acceptor molecules alternate. These … DADADA … stacked columns are tied into sheets through weaker donor-donor overlapping. While the structures of the TCNQ and 2,5-TCNQF2 salts are very similar, they differ in the way sheets of donor-coupled … DADADA … stacks are arranged relative to each other. Madelung energies for both salts have been computed from charge distributions obtained from LCAO-MO calculations. Degrees of charge transfer are evaluated from the molecular geometries of both the donor and acceptor molecules and from the cyano stretching frequencies of the acceptors.

The crystal structure of the asymmetric electron acceptor TCNQF has been determined by X-ray diffraction techniques. The crystals are monoclinic, space group P21/n, with the following primary crystallographic data: a = 7.596(3)A, b = 8.204(4)A, c = 8.428(2)A, β = 90.90(3)d`, V = 525.3(3)A3, Z = 2, Dmeasd = 1.42(2) g cm-3, Dcalcd = 1.405 g cm-3. The presence of two molecules per cell requires 1(C1) molecular symmetry, inconsistent with the molecular structure of TCNQF. A centrosymmetrical twin model has been developed and refined by the full-matrix least-squares method based on counter-collected intensities. The dominant intermolecular interaction in the crystal is the one-dimension coupling of TCNQF molecules through their electric dipole moments. An estimation from an LCAO-MO calculation yields a molecular dipole moment of 2.0 D for TCNQF.

A widely applicable electroabsorption technique to measure internal electric fields in organic light‐emitting diodes is presented. The technique exploits the change in the a.c. electroabsorption response in the presence of a d.c. electric field. The electroabsorption signal is modulated at the fundamental frequency of the a.c. test signal, in addition to the usual modulation at the second harmonic frequency, when a d.c. bias is present.

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, c, 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 norbital 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 × 10−8and 3 × 10−7 ohm−1 cm−1, respectively.

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 twinned crystal structure of the charge-transfer complex TTF-2,5-TCNQF2 has been determined by single-crystal X-ray diffraction techniques. From intensity measurement on one twin component, a full structural model has been developed. The model encompasses segregated stacks of TTF donors and 2,5-TCNQF2 acceptors, with each chain exhibiting significant dimerization. The alternate interplanar spacings in the TTF stack are 3.34A and 3.60A, while those in the 2,5-TCNQF2 stack are 3.23A and 3.55A. Nearly eclipsed molecular overlap patterns are found within each of the dimerized pairs. The Madelung energy of TTF-2,5-TCNQF2 has been calculated at - 2.65 eV per donor/acceptor pair for full charge transfer, utilizing partial atomic charges obtained from CNDO/INDO molecular orbital calculations. Full charge transfer is considered appropriate for this complex based primarily on the observed component molecular geometries. The dimerized structural motif observed at room temperature for the TTF-2,5-TCNQF2 system may reflect a phase transition at a higher temperature, owing to either an electronic-or a spin-Peierls instability. Diffraction data to temperatures on the order of 390 K do not indicate a solid-state phase transformation before crystal decomposition.

The crystal structure of the electron acceptor 2,5-difluoro-7,7,8,8-tetracyano-p-quinodimethane, 2,5-TCNQF2, has been determined by single-crystal X-ray diffraction methods. The layered crystal structure is dominated by the antiparallel coupling of cyano bond moments of symmetry-related molecules. The molecular and electronic structure (INDO approximation) of 2,5-TCNQF2 are extensively compared to that of its parent TCNQ and the perfluoro analog TCNQF4. Crystal data for 2,5-TCNQF2 are as follow: monoclinic, space group C2/m, a=10.208(4) Å, b=6.026(2) Å, c=8.836(3) Å,β=106.64(3)d`, V=520.8 Å3. The site symmetry (2/m;C2h) in the crystal is identical to that for the free 2,5-TCNQF2 molecule

Current theories on the origin of high electrical conductivity in TCNQ-based materials emphasize the need for incomplete charge transfer as well as segregated stacks of donor and acceptor molecules and uniform spacing within the stacks. The requirements for an “organic metal” are discussed in terms of partial charge transfer. An examination of 61 structurally related TTF–TCNQ, based complexes suggests that the combinations with the redox potential -0.02=E1(D)-E1(A)=0.34 V have a high possibility of being “organic metals.” A method to arrange the complex by the difference between the electrochemical half-wave potentials of the donor and the acceptor molecule is proposed to predict electrical properties of the complex.

Carbon molecular sieve membranes (CMSMs) commonly lose permeability over time due to the collapse of micropores. This decline in permeability, due to the densification of the membrane, is known as physical aging. CMSMs derived from polymers of intrinsic microporosity (PIM-1) are highly affected by physical aging, with declines in permeability greater than 60% over time. It is hypothesized that the densification of CMSMs derived from this high-free-volume polymer precursor is thermodynamically driven by the collapse of large unconnected graphene domains to reach a more stable conformation (i.e., graphite). This study describes a novel strategy to mitigate physical aging by pillaring the CMSM using copper nanoparticles. Highly soluble metal–organic polyhedra-18 (MOP-18) was introduced into PIM-1 with loadings up to 40 wt/wt to form a mixed-matrix membrane (MMM). Pyrolysis of the MMM at 550 °C resulted in the in situ formation of copper metal nanoparticles that acted as pillars for the graphene sheets within the CMSM, preventing the collapse of the micropores, thus minimizing the aging of the CMSM. Single gas permeation measurements of CO2and CH4were made on the pristine polymer-derived CMSM and the copper-pillared CMSM at 35 °C and 2 bar to confirm the membranes’ resistance to physical aging. The CH4permeability for the PIM-1 CMSM decreased by ∼60%, from 64 to 27 Barrers, over a period of 7 days, while the copper-pillared PIM-1 CMSM remarkably showed essentially no decline in CH4permeability. This research demonstrates a general approach to reducing physical aging in CMSMs.

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.

The development of the organic metallic state is traced from our original synthesis and study of TTF-TCNQ to the new conductor HMTSF-TCNQ, the first organic substance which remains metallic as T → 0.

A series of N-substituted-2-(5′-vinyl-2′-thienyl)-5-(2″-thienyl)pyrroles were synthesized and their electrochromic properties studied, Ia an attempt to tailor the observed color, copolymers of 5-vinylterthiophene and N-phenyl-2-(5′-vinyl-2′-thienyl)-5-(2″-thienyl) pyrrole were prepared using different stoichiometries. In another approach we synthesized copolymers of (i) N-vinylcarbazole and 5-vinylterthiophene and (ii) N-vinylcarbazole and N-phenyl-2-(5′-vinyl-2′-thienyl)-5-(2″-thienyl)pyrrole.