Chemphyschem最新文献

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 303.15K-333.15K 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 313.15K, 323.15K and 333.15K. 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 313.15 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 (MEA) 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 VAg/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.

The iron-based KxFe2-ySe2 superconductor displays phase separation, leading to the coexisting metallic phase embedded in an antiferromagnetic matrix. The metallic character of the system is believed to arise from a percolative granular network affecting normal as well as superconducting state properties. This network can be manipulated and controlled through thermal treatments. In this study, we have used scanning X-ray micro-fluorescence to visualize morphology of the phase separation and the percolation in KxFe2-ySe2, manipulated by distinct thermal treatments, i.e., fast quenching and slow cooling. We find a differing spatial correlation between Fe and K in differently treated samples, ascribed to different Fe vacancy ordering. We have identified an intermediate phase that acts as an interface between the two phases. The high temperature quenching produces oriented clustered microstructure in which the percolation threshold is lower and hence a more effective network for the transport pathways. Instead, the slow cooling results in larger interfaces around the percolation threshold affecting the superconducting properties of the system. The results provide a quantitative characterization of microstructural morphology of differently grown KxFe2-ySe2 showing potential for the design of electronic devices based on sub-micron scale chemical phase separation, thus opening avenues for further studies of complex heterogeneous structures.

Recent advancements in signal amplifiers, such as biofunctionalized gold nanoparticles (AuNPs) have improved the surface plasmon resonance (SPR) performance. However, the correlation between the sizes of DNA-Au conjugates and the SPR chips remains elusive. We investigated how the size of AuNPs functioned with DNA detection probes (D-AuNPs) affect SPR signals in sandwich DNA hybridization assays. The effects of three sizes (5, 13, and 29 nm) of D-AuNPs with an equal surface probe density were systematically compared to delineate the relationship between signal amplification and steric hindrance. Sporadically adsorbed target DNA on sparse capture probe-coated chips led to a growth of signal amplification with larger D-AuNPs. In contrast, on dense capture probe-coated SPR chips, when the target DNA concentration was above 1.5 nM, the medium-sized 13-nm AuNPs displayed 1.7- and 1.3-fold enhancement factors than 5-nm and 29-nm ones, respectively. Our results indicate the steric hindrance disturbs the capture of D-AuNPs on dense target DNA-modified chips, rendering the surface density of captured D-AuNPs a determining factor of the sensor response. Alternatively, the sensor sensitivity to D-AuNP surface density is crucial on chips with sparse target DNA. These insights should stimulate and guide future research on surface functionalization toward SPR sensors and AuNPs.

Molecular photoswitches have demonstrated potential for storing solar energy at the molecular level, with power densities comparable to commercial batteries and hydroelectric energy storage. However, development of efficient photoswitches is hindered by limitations in cyclability and optical properties of existing materials.  We here demonstrate that certain limitations in photoswitches based on electrocyclizations stem from the issue of controlling competition between Woodward-Hoffmann allowed and forbidden pathways.  Our approach moves beyond the traditional view of activation barriers and reveals that second-order saddle points are crucial in dictating the competition between disrotatory and conrotatory pathways. These insights suggest new opportunities to manipulate the competition between these pathways through geometric constraints, fundamentally altering the connectivity of the potential energy surface. Our study also emphasizes the necessity of multi-reference methods and the need to conduct higher-dimensional explorations for competing pathways beyond photoswitch design.