Chemphyschem最新文献

Organic field-effect transistors (OFETs) with good flexibility and low operating voltage, are of great meaning for the low power stretchable and wearable electronic devices. The operating voltage and flexibility are easily affected by the dielectric layers in the OFETs. Bilayer dielectrics comprising both high- and low-permittivity (k) insulating polymers, have been reported. The flexible bilayer dielectrics can combine the advantages of both insulating polymers, which are high charge carriers from low-k polymers and low operating voltage from high-k polymers. However, the effect of film thicknesses in the bilayer dielectrics on the OFET performance is seldom investigated. Here, bilayer dielectrics comprising high-k polyvinyl alcohol (PVA) and low-k polymethylmethacrylate (PMMA) were fabricated. And PVA/PMMA bilayers with three different PVA film thicknesses are carefully investigated. The 300 nm PVA/100 nm PMMA bilayer dielectric makes the pentacene OFETs show the highest hole mobility of 1.24 cm² V^-1s^-1 and the corresponding inverters give a high voltage gain of 40 and a noise margin of 2.3 V (77 % of 1/2 V_DD) at low operating voltage of 6 V. Both the pentacene transistors and the inverters still work properly under bending radium of 5.85 mm, proving the good prospects of the PVA/PMMA bilayer dielectric in practical applications.

Quantum chemistry plays a key role in exploring the chemical properties of highly reactive chlorine polyfluoride compounds (ClF_n). Here, we investigate the thermochemical properties of ClF_n species (n=2-6) by means of high-level thermochemical procedures approximating the CCSDT(Q) and CCSDTQ5 energies at the complete basis set limit. We consider total atomization energies (TAEs), Cl-F bond dissociation energies (BDEs), F₂ elimination energies (F₂ elim.), ionization potentials (IPs), and electron affinities (EAs). The TAEs have significant contributions from post-CCSD(T) correlation effects. The higher-order triple excitations, CCSDT-CCSD(T), are negative and amount to -0.338 (ClF₂), -0.727 (ClF₃), -0.903 (ClF₄), -1.335 (ClF₅), and -1.946 (ClF₆) kcal/mol. However, the contributions from quadruple (and, where available, also quintuple) excitations are much larger and positive and amount to +1.335 (ClF₂), +1.387 (ClF₃), +2.367 (ClF₄), +2.399 (ClF₅), and +3.432 (ClF₆) kcal/mol. Thus, the contributions from post-CCSD(T) excitations exceed the threshold of chemical accuracy in nearly all cases. Due to their increasing hyper-valency and multireference character, the ClF_n series provides an interesting and challenging test case for both density functional theory and low-level composite ab initio procedures. Here, we highlight the limitations in achieving overall chemical accuracy across all DFT and most composite ab initio procedures.

The triel bond (TrB) formed between Be(CH3)2/Mg(CH3)2 and TrX3 (Tr = B, Al, and Ga; X = H, F, Cl, Br, and I) is investigated via the MP2/aug-cc-pVTZ(PP) quantum chemical protocol. The C atoms of the methyl groups in M(CH3)2 are characterized by a negative electrostatic potential and act as an electron donor in a triel bond with the π-hole above the Tr atom of planar TrX3. The interaction energy spans a wide range between 2 and 69 kcal/mol. Mg(CH3)2 forms a stronger TrB than does Be(CH3)2, which comports with the more negative electrostatic potential on its methyl groups. Some of the complexes involving Mg display a high degree of transfer of the methyl group from Mg to Tr, which is accompanied by an inversion of the bridging methyl and a sizable pyramidalization of the TrX3 unit. The geometries of these complexes have the properties of the long sought pentacoordinate C which has eluded identification and characterization in the past.

Mixing different aliphatic polyamides provides opportunities to tune and optimize the properties of these semicrystalline polycondensates. Combining experiment and theory, we predict and explain the miscibility of aliphatic polyamide mixtures. Visual inspection and Raman spectroscopy of polyamide mixtures show that liquid/liquid phase demixing occurs in the melt due to limited miscibility. The large number of potential polyamide mixtures makes it challenging to test all miscibilities experimentally. Moreover, the dependence of miscibility on dispersity and the presence of water implies further challenges to a systematic experimental approach. Our theory predicts polyamide miscibility, while accounting for amide content, non-uniformity, and moisture content, using generalizations of Flory–Huggins theory. Predicted miscibilities align with experimental results obtained on tested mixed polyamides. The gained insights guide the optimization of functional polyamide blends.

This study evaluates the carbon dioxide (CO₂) capture capabilities of a novel aqueous blend of N,N-dimethyldipropylenetriamine (DMDPTA) and benzylamine (BA). The solvent properties such density, vapor- liquid equilibrium (VLE) of CO₂ in the solvent, CO₂ absorption enthalpy are evaluated experimentally for solvent composition of (5 mass % DMDPTA+25 mass % BA), (10 mass % DMDPTA+20 mass % BA), and (15 mass % DMDPTA+15 mass % BA). Solvent density were measured in the temperature range of 303 K-333 K and correlated using Redlich-Kister excess molar volume model, with a low average absolute relative deviation (AARD) of 0.014. VLE data was measured using a custom-made stirred VLE cell, within CO₂ partial pressure range of 2-200 kPa and at temperatures 313 K, 323 K and 333 K. Equilibrium CO₂ solubility data were correlated using a modified Kent-Eisenberg model, achieving an AARD of 1.5 %. Enthalpy of CO₂ absorption was measured at 313 K using a Meter Toledo reaction calorimeter. Results indicated that under similar process conditions and solvent composition, (DMDPTA+BA) blends exhibited significantly higher CO₂ loading and low absorption enthalpy compared to aqueous BA and monoethanolamine solvent alone indicating the potential of (DMDPTA+BA) blend as efficient CO₂ capture solvent.

Solid electrolyte composites between organic ionic plastic crystals (OIPCs) and polymers can potentially show enhanced mechanical properties and ion conduction. These properties can be determined by the formation of interfacial regions which affect the structure, thermal properties, and ion transport of the composite material. Here we studied the properties of composites between the OIPC hexamethylguanidinium bis(fluorosulfonyl)imide (HMGFSI) and acrylate polymer nanoparticles functionalised with lithium, using various techniques including solid-state NMR spectroscopy. An enhancement in ionic conductivity of three orders of magnitude as well as increased lithium and OIPC cation and anion dynamics were observed in the composite as prepared with 40 v% of polymer nanoparticles with respect to the pure OIPC at 50 °C. This was attributed to the increased overall structural disorder as a result of the formation of disordered interfacial regions, which were evidenced by solid-state NMR spectroscopy. In addition, the importance of the thermal history of these composites is highlighted, with differences in the conductivity and ion dynamics observed after melting and recrystallizing the OIPC component, leading to less disordered interfacial regions. This study enriches our fundamental understanding of the formation of interfacial regions in OIPC composites and their effect on the bulk properties of the electrolyte.

The development of large number of two-dimensional (2D) nanostructured materials that followed the success of graphene and the need for their handling and manipulation e. g., in inks, brought to the fore the study of solvents and substances that contribute to the stabilization of 2D nanomaterials in the liquid phase. The successful dispersion of 2D materials in solvents is combined with one of the most widespread preparation methods, that of liquid phase exfoliation. In this article, a review for the role of water in the preparation of different 2D nanostructures and their stable dispersions in the liquid phase is discussed. The use of water as a solvent or dispersant is instrumental in promoting materials with an ecological footprint, low cost, and sustainability.

The reaction of sulfur trioxide (SO₃) and thiobenzoic acid (C₆H₅COSH) is investigated in the gas phase under supersonic jet conditions. Rotational spectroscopy of the parent and several isotopically substituted derivatives, in conjunction with DFT calculations at the M06-2X/6-311++G(3df,3pd) level of theory, identify the product as thiobenzoic sulfuric anhydride, C₆H₅C(=S)OSO₂OH. Single point CCSD(T)/CBS(D-T)//M06-2X/6-311++G(3df,3pd) calculations place the electronic energy of the product anhydride 114 kJ/mol lower than that of SO₃+C₆H₅COSH at infinite separation. The calculations further indicate that the reaction proceeds through a cyclic transition state which lies 11.3 kJ/mol higher in energy than a C₆H₅COSH⋅SO₃ complex, but 83.3 kJ/mol lower in energy than that of the separated reactants. The reaction is rapid under the experimental conditions of this study: based on the duration of the collisional phase of the supersonic expansion, it is clear that the product is formed within tens of microseconds after mixing. While the analogous reaction of carboxylic acids with SO₃ has been demonstrated, the ability of a thiocarboxylic acid to undergo similar chemistry has not previously been established. Although rotational spectroscopy is best known for its precise interrogation of molecular and electronic structure, this work demonstrates its ability to study chemical transformations as well.

The necessity of new methods to substitute the Haber-Bosch process in the NH₃ synthesis, generating fewer greenhouse gases, and dispensing less energy, drove the investigation of the photoelectrocatalytic approach in the N₂ reduction reaction (N2RR). For that, this work presents the synthesis and characterization of the layered CZTSSe/CdS/TiO₂ photocathode decorated with Pt nanoparticles for application in NH₃ production using the photoelectrocatalysis technique. The CZTSSe/CdS/TiO₂-Pt characterization showed a well-designed and stable photocatalyst synthesized layer by layer with an important contribution of the Pt nanoparticles for the catalyst performance, improving the photocurrent density and the charge transfer. The N2RR in a two-compartment photochemical cell with 0.1 mol L^-1 Na₂SO₃ and 0.05 mol L^-1 H₂SO₄ in the cathodic and anodic chamber, respectively, using CZTSSe/CdS/TiO₂-Pt and under 1 sun of light incidence and applied potential of -0.4 V_Ag/AgCl reached 0.22 mmol L^-1 cm^-2 NH₃, a value 28 folds higher than using the catalyst without Pt modification. The superiority of N2RR under the photoelectrocatalysis technique was demonstrated compared to photocatalytic and electrocatalytic techniques, together with the investigation of the supporting electrolyte influence in the cathodic compartment. Additionally, that is the first time a kesterite-based photocathode has been applied to NH₃ photosynthesis, showing excellent photoconversion capability.

Amyloid fibril formation by some peptides leads to several neurogenetic disorders. This limits their biological activity and increases cytotoxicity. Human calcitonin (hCT), 32 residue containing peptide, known for regulating calcium and phosphate concentration in the blood tends to form amyloids in aqueous medium. Polyphenols are very effective in inhibiting fibril formation. As part of our research, we have taken Magnolol (Mag), which is extracted from the Chinese herb Magnolia officinalis. To evaluate its effectiveness as an inhibitor in preventing hCT aggregation, we conducted an all-atom classical molecular dynamics simulation with varying concentrations of Mag. In presence of Mag, hCT maintains its helical conformation in higher order. Magnolol primarily interacts with hCT via van der Waals interaction. Asp15 residue of hCT, resides in the amyloid region (D₁₅FNKF₁₉) forms strong hydrogen bonding interaction with Mag. Moreover, aromatic residues of hCT interact with Mag through π-π stacking interactions. Our work gives insights into the molecular mechanism of Magnolol in the inhibition of hCT fibril formation to use it as a potential candidate for medicinal purpose.