Effect of Crystallization Modes in TIPS-Pentacene/Insulating Polymer Blends on the Gas Sensing Properties of Organic Field-Effect Transistors

Blending organic semiconductors with insulating polymers has been known to be an effective way to overcome the disadvantages of single-component organic semiconductors for high-performance organic field-effect transistors (OFETs). We show that when a solution processable organic semiconductor (6,13-bis(triisopropylsilylethynyl)pentacene, TIPS-pentacene) is blended with an insulating polymer (PS), morphological and structural characteristics of the blend films could be significantly influenced by the processing conditions like the spin coating time. Although vertical phase-separated structures (TIPS-pentacene-top/PS-bottom) were formed on the substrate regardless of the spin coating time, the spin time governed the growth mode of the TIPS-pentacene molecules that phase-separated and crystallized on the insulating polymer. Excess residual solvent in samples spun for a short duration induces a convective flow in the drying droplet, thereby leading to one-dimensional (1D) growth mode of TIPS-pentacene crystals. In contrast, after an appropriate spin-coating time, an optimum amount of the residual solvent in the film led to two-dimensional (2D) growth mode of TIPS-pentacene crystals. The 2D spherulites of TIPS-pentacene are extremely advantageous for improving the field-effect mobility of FETs compared to needle-like 1D structures, because of the high surface coverage of crystals with a unique continuous film structure. In addition, the porous structure observed in the 2D crystalline film allows gas molecules to easily penetrate into the channel region, thereby improving the gas sensing properties

Cloning of heat shock protein genes from the brown planthopper, Nilaparvata lugens, and the small brown planthopper, Laodelphax striatellus, and their expression in relation to thermal stress

Insect Science (2008) 15, 415-422, DOI 10.1111/j.1744-7917.2008 Introduction Organisms develop abilities to endure various stresses from unfavorable environmental conditions such as temperature extremes, desiccation, toxic substances and pathogens. At the molecular level, heat shock proteins (HSPs) play a significant role in generating tolerance to such stresses The HSP family is multigenic and divided into at least three groups based on their protein size and sequence similarity: small heat shock protein (sHSP) with molecular masses ranging 12-43 kDa, heat shock protein 70 (HSP70), approximately 70 kDa, and heat shock protein 90 (HSP90), a higher molecular mas

Excellent sulfur resistance of Pt/BaO/CeO(2) lean NO(x) trap catalysts

In this work, we investigated the NO(x) storage behavior of Pt/BaO/CeO(2) catalysts, especially in the presence of SO(2). High surface area CeO(2) (similar to 110 m(2)/g) with a rod like morphology was synthesized and used as a support. The Pt/BaO/CeO(2) sample demonstrated slightly higher NO(x) uptake in the entire temperature range studied compared with Pt/BaO/gamma-Al(2)O(3). More importantly, this ceria-based catalyst showed higher sulfur tolerance than the alumina-based one. The time of complete NO(x) uptake was maintained even after exposing the sample to similar to 3 g/L of SO(2). The same sulfur exposure, on the other hand, eliminated the complete NO(x) uptake time on the alumina-based NO(x) storage catalysts. TEM images show no evidence of either Pt sintering or BaS phase formation during reductive de-sulfation up to 600 degrees C on the ceria-based catalyst, while the same process over the alumina-based catalyst resulted in both a significant increase in the average Pt cluster size and the agglomeration of a newly formed BaS phase into large crystallites. XPS results revealed the presence of about five times more residual sulfur after reductive de-sulfation at 600 degrees C on the alumina-based catalysts in comparison with the ceria-based ones. All of these results strongly support that, besides their superior intrinsic NO(x) uptake properties, ceria-based catalysts have (a) much higher sulfur tolerance and (b) excellent resistance against Pt sintering when they are compared to the widely used alumina-based catalysts. (C) 2008 Elsevier B.V. All rights reservedclose353

Ferroelectric Polarization in Poly(vinylidene difluoride) by DFT calculation

Poly(vinylidene difluoride) (PVDF) polymer has been well used for binder materials in lithium-ion batteries (LIB). However, effects of crystalline phase of the PVDF on LIB were rarely demonstrated. Here, the electronic properties and lithium ion affinity of paraelectric ?? phase PVDF and ferroelectric ?? phase PVDF were investigated using density functional theory calculations. A strong polarization of the ferroelectric ?? phase PVDF leaded to surface metallization by shifting local bands in electronic density of states. More specifically, the polarization increased an amount of charge transfer significantly between each polymer layer and varied the work functions to a large extent (i.e. 8.3 eV for F-terminated surface and 1.6 eV for H-terminated surface), which was expected to play a crucial role in reducing charge transfer resistance. Furthermore, the ferroelectric polarization enhanced the binding affinity of lithium ion, which resulted in the promotion of lithium ions accessing toward the electrode surface. To this end, we found that ferroelectric polarization of PVDF is good to facilitate charge transfer and lithium ion diffusion in the vicinity of active electrodes

Hierarchical Alignment of Chitin Fiber as an Electrolyte Uptake Membrane for Li Metal based Oxygen battery

Here, we introduce regenerated fibers of chitin (Chiber), the second most abundant biopolymer after cellulose, and propose its utility as a nonwoven fiber separator for lithium metal batteries (LMBs) that exhibits an excellent electrolyte-uptaking capability and Li-dendritemitigating performance. Chiber is produced by a centrifugal jet-spinning technique, which allows a simple and fast production of Chibers consisting of hierarchically aligned self-assembled chitin nanofibers. Following the scrutinization on the Chiber−Li-ion interaction via computational methods, we demonstrate the potential of Chiber as a nonwoven mat-type separator by monitoring it in Li−O2 and Na−O2 cells

Chitin Fibers as A Nonwoven-Mat Separator for Lithium Metal Batteries: A Computational Study

The chitin, poly(??-(1,4)-N-acetyl-D-glucosamine), is the second most abundant biogenic macromolecule after cellulose. Herein, we propose the usage of chitin fiber as a nonwoven mat-type separator for lithium metal rechargeable batteries. By theoretical studies with the molecular dynamics simulations and density functional theory calculations, we found that the chitin fiber exhibited the inertness to the aprotic electrolytes and also showed the excellent electrolyte-uptaking capability as compared to the conventional battery separator. In particular, the strong physicochemical affinity to Li-ions with the binding reversibility, which was attributed to the unique coordination with functional groups, was observed. We demonstrated that this chitin-Li-ion interaction could play a critical role in increasing Li-ion movement and alleviating the inhomogeneous distribution of Li-ions at the interface of the electrolyte-absorbed chitin separator and the Li metal anode

Effect of barium loading on the desulfation of Pt-BaO/Al2O3 studied by H-2 TPRX, TEM, sulfur K-edge XANES, and in situ TR-XRD

Desulfation processes were investigated over sulfated Pt-BaO/Al2O3 with different barium loading (8 and 20 wt%) by using H-2 temperature programmed reaction (TPRX), transmission electron microscope (TEM) with energy dispersive spectroscopy (EDS), sulfur K-edge X-ray absorption near-edge spectroscopy (XANES), and in situ time-resolved X-ray diffraction (TR-XRD) techniques. Both sulfated samples (8 and 20 wt%) form sulfate species (primarily BaSO4) as evidenced by S K-edge XANES and in situ TR-XRD. However, the desulfation behavior is strongly dependent on the barium loading. Sulfated Pt-BaO(8)/Al2O3,consisting predominantly of surface BaO/BaCO3 species, displays more facile desulfation by H-2 at lower temperatures than sulfated Pt-BaO(20)/Al2O3, a material containing primarily bulk BaO/BaCO3 species. Therefore, after desulfation with H-2 up to 1073 K, the amount of the remaining sulfur species on the former, mostly as BaS, is much less than that on the latter. This suggests that the initial morphology differences between the two samples play a crucial role in determining the extent of desulfation and the temperature at which it occurs. It is concluded that the removal of sulfur is significantly easier at lower barium loading. This finding can potentially be important in developing more sulfur resistant LNT catalyst systemsclose272

Hierarchical Chitin Fibers with Aligned Nanofibrillar Architectures: A Nonwoven-Mat Separator for Lithium Metal Batteries

Here, we introduce regenerated fibers of chitin (Chiber), the second most abundant biopolymer after cellulose, and propose its utility as a nonwoven fiber separator for lithium metal batteries (LMBs) that exhibits an excellent electrolyte-uptaking capability and Li-dendrite-mitigating performance. Chiber is produced by a centrifugal jet-spinning technique, which allows a simple and fast production of Chibers consisting of hierarchically aligned self-assembled chitin nanofibers. Following the scrutinization on the Chiber-Li-ion interaction via computational methods, we demonstrate the potential of Chiber as a nonwoven mat-type separator by monitoring it in Li-O2 and Na-O2 cells.clos

Significance of ferroelectric polarization in poly (vinylidene difluoride) binder for high-rate Li-ion diffusion

An interesting and effective route for improving battery performance using ferroelectric poly(vinylidene difluoride) (PVDF) polymer as a binder material is demonstrated in this work. A ferroelectric PVDF phase developed under the appropriate thermal annealing process enables generation of suitable polarization on active materials during the discharge and charge process, giving rise to longer capacity with lower overpotential at a high current rate. Electrochemical analysis including in situ galvanostatic electrochemical impedance spectroscopy and a galvanostatic intermittent titration measurement revealed that the ferroelectric binder effectively reduced Li-ion diffusion resistance and supported fast migration in the vicinity of active electrodes. Computational results further support that the binding affinity of the ferroelectric PVDF surface is much higher than that of the paraelectric PVDF, confirmed by ideally formed ferroelectric and paraelectric PVDF conformations with Li-ions. Furthermore, we consistently achieved high Li-ion battery (LIB) performance in full cell architecture consisting of a LTO/separator/LFP with a ferroelectric PVDF binder in the anode and cathode materials, revealing that the polarization field is important for fabricating high-performance LIBs, potentially opening a new design concept for binder materials.clos

Promotional effects of H(2)O treatment on NO(x) storage over fresh and thermally aged Pt-BaO/Al(2)O(3) lean NO(x) trap catalysts

A simple liquid water treatment applied to fresh and thermally aged Pt(2 wt%)-BaO(20 wt%)/Al(2)O(3) lean NO(x) trap catalysts at room temperature induces morphological and structural changes in the barium species as followed by XRD and TEM analysis. During the water treatment, liquid water sufficient to fill the catalyst pore volume is brought into contact with the samples. It was found that irrespective of the original barium chemical state (highly dispersed BaO or crystalline BaAl(2)O(4)), exposing the sample to this liquid water treatment promotes the formation of BaCO(3) crystallites (about 15-25 nm of its size) without changing the Pt particle size. Such transformations of the barium species are found to significantly promote NO(x) uptake from 250 to 450 C. The increase in the NO(x) uptake for the water-treated samples can be attributed to an enhanced Pt-Ba interaction through the redistribution of barium species. These results provide useful information for the regeneration of aged lean NO(x) trap catalysts since water is plentiful in the exhaust of diesel or lean-burn enginesclose121