Gelatin hydrogel electrolytes and their application to electrochemical supercapacitors

Gelatin hydrogel electrolytes (GHEs) with varying NaCl concentrations have been prepared by cross-linking an aqueous solution of gelatin with aqueous glutaraldehyde and characterized by scanning electron microscopy, differential scanning calorimetry, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic chronopotentiometry. Glass transition temperatures for GHEs range between 339.6 and 376.9 K depending on the dopant concentration. Ionic conductivity behavior of GHEs was studied with varying concentrations of gelatin, glutaraldehyde, and NaCl, and found to vary between 10(-3) and 10(-1) S cm(-1). GHEs have a potential window of about 1 V. Undoped and 0.25 N NaCl-doped GHEs follow Arrhenius equations with activation energy values of 1.94 and 1.88 x 10(-4) eV, respectively. Electrochemical supercapacitors (ESs) employing these GHEs in conjunction with Black Pearl Carbon electrodes are assembled and studied. Optimal values for capacitance, phase angle, and relaxation time constant of 81 F g(-1), 75 degrees, and 0.03 s are obtained for 3 N NaCl-doped GHE, respectively. ES with pristine GHE exhibits a cycle life of 4.3 h vs 4.7 h for the ES with 3 N NaCl-doped GHE. (c) 2007 The Electrochemical Society.

Thiourea based novel chromogenic sensor for selective detection of fluoride and cyanide anions in organic and aqueous media

Novel chromogenic thiourea based sensors 4,4'-bis-[3-(4-nitrophenyl) thiourea] diphenyl ether 1 and 4,4'-bis-[3-(4-nitrophenyl) thiourea] diphenyl methane 2 having nitrophenyl group as signaling unit have been synthesized and characterized by spectroscopic techniques and X-ray crystallography. The both sensors show visual detection, UV-vis and NMR spectral changes in presence of fluoride and cyanide anions in organic solvent as well as in aqueous medium. The absorption spectra indicated the formation of complex between host and guest is in 1:2 stoichiometric ratios. (C) 2010 Elsevier B.V. All rights reserved.

Towards a green synthesis of isoquinoline: Beckmann rearrangement of E,-cinnamaldoxime over H-zeolites

Isoquinoline was prepared through the Beckmann rearrangement of cinnamaldoxime over different H-zeolites, K-10 montmorillonite clay, amorphous SiO2–Al2O3 and γ-alumina under well-optimized conditions of temperature, weight hourly space velocity and catalyst loading. Cinnamaldoxime under ambient reaction conditions over the catalysts underwent migration of the anti-styryl moiety to electron deficient nitrogen (Beckmann rearrangement) followed by an intramolecular cyclization to yield isoquinoline. Cinnamo-nitrile (dehydration product) and cinnamaldehyde were formed as by-products. Isoquinoline formation was high on zeolite catalysts (ca. >86.5%) and mordenite (ca. 92.3%) was the most efficient in the series. Catalysts were susceptible for deactivation and the decrease in the percentage conversion of oxime with time is associated with a corresponding increase in the acid hydrolysis producing salicylaldehyde at later stages of the reaction. However, these catalysts retain activity considerably and can be recycled without loss of activity and change of product distribution.

Mixed saturated-unsaturated alkyl-chain assemblies: Solid solutions of zinc stearate and zinc oleate

The linear saturated stearic acid and the bent mono-unsaturated oleic acid do not mix and form solid solutions. However, the zinc salts of these acids can. From X-ray diffraction and DSC measurements we show that the layered zinc stearate and zinc oleate salts form a homogeneous solid solution at all composition ratios. The solid solutions exhibit a single melting endotherm, with the melting temperature varying linearly with composition but with the enthalpy change showing a minimum. By monitoring features in the infrared spectra that are characteristic of the global conformation of the hydrocarbon chain, and hence can distinguish between stearate and oleate chains, it is shown that solid solution formation is realized by the introduction of gauche defects in a fraction of the stearate chains that are then no longer linear. This fraction increases with oleate concentration. It has also been possible from the spectroscopic measurements to establish a quantitative relation between molecular conformational order and the thermodynamic enthalpy of melting of the solid solutions.

Modified density matrix renormalization group algorithm for the zigzag spin-1/2 chain with frustrated antiferromagnetic exchange: Comparison with field theory at large J(2)/J(1)

A modified density matrix renormalization group (DMRG) algorithm is applied to the zigzag spin-1/2 chain with frustrated antiferromagnetic exchange J(1) and J(2) between first and second neighbors. The modified algorithm yields accurate results up to J(2)/J(1) approximate to 4 for the magnetic gap Delta to the lowest triplet state, the amplitude B of the bond order wave phase, the wavelength lambda of the spiral phase, and the spin correlation length xi. The J(2)/J(1) dependences of Delta, B, lambda, and xi provide multiple comparisons to field theories of the zigzag chain. The twist angle of the spiral phase and the spin structure factor yield additional comparisons between DMRG and field theory. Attention is given to the numerical accuracy required to obtain exponentially small gaps or exponentially long correlations near a quantum phase transition.

Synthesis and Characterization of a Class of Donor-Acceptor Conjugated Molecules: Experiments and Theoretical Calculations

A class of conjugated molecules containing donor (thiophene) and acceptor (malononitrile) is synthesized by Knoevenagel condensation reaction between 2-(2,6-dimethy1-4H-pyran-4-ylidene) malononitrile and thiophene carbaldehyde containing two and three thiophene units. The resulting molecules are characterized by H-1 and C-13 NMR. We have performed UV-vis absorption, fluorescence, and cyclic voltammetry measurements on these materials. The spectroscopic and electrochemical measurements proved beyond doubt that these materials possess lowexcitation gap and are suitable for being an active material in various electronic devices. We have also performed electronic structure calculations using density functional theory (DFT) and INDO/SCI methods to characterize the ground and excited states of this class of molecules. These donor-acceptor molecules show a strong charge transfercharacter that increases with the increase in the number of thiophene rings coupled to the malononitrile acceptor moiety. We have also calculated the pi-coherence length, Stoke's shift, and effect of solvents on excited states for this class of molecules, Our theoretical values agree well with experimental results.

Fluorescent resonant excitation energy transfer in linear polyenes

We have studied the dynamics of excitation transfer between two conjugated polyene molecules whose intermolecular separation is comparable to the molecular dimensions. We have employed a correlated electron model that includes both the charge-charge, charge-bond, and bond-bond intermolecular electron repulsion integrals. We have shown that the excitation transfer rate varies as inverse square of donor-acceptor separation R-2 rather than as R-6, suggested by the Foumlrster type of dipolar approximation. Our time-evolution study alsom shows that the orientational dependence on excitation transfer at a fixed short donor-acceptor separation cannot be explained by Foumlrster type of dipolar approximation beyond a certain orientational angle of rotation of an acceptor polyene with respect to the donor polyene. The actual excitation transfer rate beyond a certain orientational angle is faster than the Foumlrster type of dipolar approximation rate. We have also studied the excitation transfer process in a pair of push-pull polyenes for different push-pull strengths. We have seen that, depending on the push-pull strength, excitation transfer could occur to other dipole coupled states. Our study also allows for the excitation energy transfer to optically dark states which are excluded by Foumlrster theory since the one-photon transition intensity to these states (from the ground state) is zero.

1-[(2-Chloro-7-methyl-3-quinolyl)methyl]pyridin-2(1H)-one

In the title compound, C16H13ClN2O, the quinoline ring system is essentially planar, with a maximum deviation of 0.021 (2) angstrom. The pyridone ring is oriented at a dihedral angle of 85.93 (6)degrees with respect to the quinoline ring system. In the crystal structure, intermolecular C-H center dot center dot center dot O hydrogen bonds link the molecules along the b axis. Weak pi-pi stacking interactions [centroid-centroid distances = 3.7218 (9) and 3.6083 (9) angstrom] are also observed.

Ethyl 6-chloro-2-[(2-chloro-7,8-dimethylquinolin-3-yl)methoxy]-4-phenylquino line-3-carboxylate

In the title compound, C30H24Cl2N2O3, the two quinoline ring systems are almost planar [maximum deviations = 0.029 (2) and 0.018 (3) angstrom] and the dihedral angle between them is 4.17 (8)degrees. The dihedral angle between the phenyl ring and its attached quinoline ring is 69.06 (13)degrees. The packing is stabilized by C-H center dot center dot center dot O, C-H center dot center dot center dot N, weak pi-pi stacking [centroid-centroid distances = 3.7985 (16) and 3.7662(17) angstrom] and C-H center dot center dot center dot pi interactions.

1-[(2-Chloro-7,8-dimethylquinolin-3-yl)methyl]pyridin-2(1H)-one

In the title compound, C17H15ClN2O, the quinoline ring system is nearly planar, with a maximum deviation from the mean plane of 0.074 (2) angstrom, and makes a dihedral angle of 81.03 (7)degrees with the pyridone ring. The crystal packing is stabilized by pi-pi stacking interactions between the pyridone and benzene rings of the quinoline ring system [centroid-centroid distance = 3.6754 (10) angstrom]. Furthermore, weak intermolecular C-H center dot center dot center dot O hydrogen bonding links molecules into supramolecular chains along [001].

Resource recovery potential from secondary components of segregated municipal solid wastes

Fermentable components of municipal solid wastes (MSW) such as fruit and vegetable wastes (FVW), leaf litter, paddy straw, cane bagasse, cane trash and paper are generated in large quantities at various pockets of the city. These form potential feedstocks for decentralized biogas plants to be operated in the vicinity. We characterized the fermentation potential of six of the above MSW fractions for their suitability to be converted to biogas and anaerobic compost using the solid-state stratified bed (SSB) process in a laboratory study. FVW and leaf litter (papermulberry leaves) decomposed almost completely while paddy straw, sugarcane trash, sugarcane bagasse and photocopying paper decomposed to a lower extent. In the SSB process between 50-60% of the biological methane potential (BMP) could be realized. Observations revealed that the SSB process needs to be adapted differently for each of the feedstocks to obtain a higher gas recovery. Bagasse produced the largest fraction of anaerobic compost (fermentation residue) and has the potential for reuse in many ways.

Multiple conformational states in crystals and in solution in alpha gamma hybrid peptides. Fragility of the C-12 helix in short sequences

The conformational properties of foldamers generated from alpha gamma hybrid peptide sequences have been probed in the model sequence Boc-Aib-Gpn-Aib-Gpn-NHMe. The choice of alpha-aminoisobutyryl (Aib) and gabapentin (Gpn) residues greatly restricts sterically accessible coil formational space. This model sequence was anticipated to be a short segment of the alpha gamma C-12 helix, stabilized by three successive 4 -> 1 hydrogen bonds, corresponding to a backbone-expanded analogue of the alpha polypeptide 3(10)-helix. Unexpectedly, three distinct crystalline polymorphs were characterized in the solid state by X-ray diffraction. In one form, two successive C-12 hydrogen bonds were obtained at the N-terminus, while a novel C-17 hydrogen-bonded gamma alpha gamma turn was observed at the C-terminus. In the other two polymorphs, isolated C-9 and C-7 hydrogen-bonded turns were observed at Gpn (2) and Gpn (4). Isolated C-12 and C-9 turns were also crystallographically established in the peptides Boc-Aib-Gpn-Aib-OMe and Boc-Gpn-Aib-NHMe, respectively. Selective line broadening of NH resonances and the observation of medium range NH(i)<-> NH(i+2) NOEs established the presence of conformational heterogeneity for the tetrapeptide in CDCl3 solution. The NMR results are consistent with the limited population of the continuous C-12 helix conformation. Lengthening of the (alpha gamma)(n) sequences in the nonapeptides Boc-Aib-Gpn-Aib-Gpn-Aib-Gpn-Aib-Gpn-Xxx (Xxx = Aib, Leu) resulted in the observation of all of the sequential NOEs characteristic of an alpha gamma C-12 helix. These results establish that conformational fragility is manifested in short hybrid alpha gamma sequences despite the choice of conformationally constrained residues, while stable helices are formed on chain extension.

Adsorption of anionic dyes on chitosan grafted poly(alkyl methacrylate)s

Chitosan grafted poly(alkyl methacrylate)s (namely chitosan grafted poly(methyl methacrylate) (ChgPMMA), chitosan grafted poly(ethyl methacrylate)(ChgPEMA), chitosan grafted poly(butyl methacrylate) (ChgPBMA) and chitosan grafted poly(hexyl methacrylate) (ChgPHMA)) were synthesized and characterized by using FT-IR and C-13 NMR techniques. The adsorption batch experiments on these grafted copolymers were conducted by using an anionic sulfonated dye. Orange-G. A pseudo-second-order kinetic model was used to determine the kinetics of adsorption. The effect of grafting, effect of process variables and the effect of different sulfonated anionic dyes (Orange-C, Congo Red, Remazol Brill Blue R and Methyl Blue) on the adsorption kinetics was determined. The Langmuir and Freundlich models were used to fit the adsorption isotherms and from the values of correlation coefficients (R-2), it was observed that the experimental data fits very well to the Langmuir model. The values of the maximum adsorption capacity of the adsorbents follow the order: ChgPMMA > ChgPEMA > ChgPBMA > ChgPHMA > chitosan. (C) 2010 Elsevier B.V. All rights reserved.

Orientational melting and reorientational motion in a cubane molecular crystal: A molecular simulation study

Detailed molecular simulations are carried out to investigate the effect of temperature on orientational order in cubane molecular crystal. We report a transition from an orientationally ordered to an orientationally disordered plastic crystalline phase in the temperature range 425-450 K. This is similar to the experimentally reported transition at 395 K. The nature of this transition is first order and is associated with a 4.8% increase in unit Cell volume that is comparable to the experimentally reported unit cell volume change of 5.4% (Phys. Rev. Lett. 1997, 78, 4938). An orientational order parameter, eta(T), has been defined in terms of average angle of libration of a molecular 3-fold axis and the orientational melting has been characterized by using eta(T). The orientational melting is associated with an anomaly in specific heat at constant pressure (C-p) and compressibility (kappa). The enthalpy of transition and entropy of transition associated with this orientational melting are 20.8 J mol(-1) and 0.046 J mol(-1) K-1, respectively. The structure of crystalline as well as plastic crystalline phases is characterized by using various radial distribution functions and orientational distribution functions. The coefficient of thermal expansion of the plastic crystalline phase is more than twice that of the crystalline phase.

Ion Transport in a Polymer-Plastic Solid Soft Matter Electrolyte in the Light of Solvent Dynamics and Ion Association

Ion transport in a recently demonstrated promising soft matter solid plastic-polymer electrolyte is discussed here in the context of solvent dynamics and ion association. The plastic-polymer composite electrolytes display liquid-like ionic conductivity in the solid state,compliable mechanical strength (similar to 1 MPa), and wide electrochemical voltage stability (>= 5 V). Polyacrylonitrile (PAN) dispersed in lithium perchlorate (LiClO4)-succinonitrile (SN) was chosen as the model system for the study (abbreviated LiClO4-SN:PAN). Systematic observation of various mid-infrared isomer and ion association bands as a function of temperature and polyme concentration shows an effective increase in trans conformer concentration along with free Li+ ion concentration. This strongly supports the view that enhancement in LiClO4-SN:PAN ionic conductivity over the neat plastic electrolyte (LiClO4-SN) is due to both increase in charge mobility and concentration. The ionic conductivity and infrared spectroscopy studies are supported by Brillouin light scattering. For the LiClO4-SN:PAN composites, a peak at 17 GHz was observed in addition to the normal trans-gauche isomerism (as in neat SN) at 12 GHz. The fast process is attributed to increased dynamics of those SN molecules whose energy barrier of transition from gauche to trans has reduced under influences induced by the changes in temperature and polymer concentration. The observations from ionic conductivity, spectroscopy, and light scattering studies were further supplemented by temperature dependent nuclear magnetic resonance H-1 and Li-7 line width measurements.