Polar Solutes Research Articles

Formation and Encapsulation of All-Inorganic Lead Halide Perovskites at Room Temperature in Metal-Organic Frameworks.

Improving the stability and tuning the optical properties of semiconducting perovskites are vital for their applications in advanced optoelectronic devices. We present a facile synthetic method for hybrid composites of perovskites and metal-organic frameworks (MOFs). A simple two-step solution-based method without organic surfactants was employed to make all-inorganic lead-halide perovskites (CsPbX3; X = Cl, Br, I, or mixed halide compositions) form directly in the pores of MIL-101 MOF. That is, a polar organic solution of lead halide (PbX2) was impregnated into the MOF pores to give PbX2@MIL-101, which was then subjected to a perovskite-formation reaction with cesium halide (CsX) dissolved in methanol. The compositions of the halogen anions in the perovskites can be modulated with various halide precursors, leading to CsPbX3@MIL-101 composites with X3 = Cl3, Cl2Br, Br2Cl, Br3, Br2I, I2Br, and I3 that exhibit gradual variation of band gap energies and tuned emission wavelengths from 417 to 698 nm.

Bioinspired nanocomposites film with highly-aligned silicon carbide nanowires and polyvinyl alcohol for mechanical and thermal anisotropy

This work reports a bioinspired anisotropic nanocomposite by polar solution assisted mechanical stretching method, consisting of polyvinyl alcohol (PVA) and silicon carbide nanowires (SiCNWs) with aligned morphology in one direction. Inspired by the structural mimicry of myofibers, in which the uniaxial mechanical property of materials can be improved evidently, highly-aligned SiCNWs and PVA chains that interact using intermolecular force can be obtained. Hysteresis is observed and reversible deformation occurs while tensile–relaxation cycles are applied to the 100% stretched SiCNWs/PVA nanocomposites. The nanocomposites exhibit excellent properties and the tensile strength of 100% stretched SiCNWs/PVA nanocomposites is 188.30 ± 4.2 MPa and elastic modulus is 6.95 GPa, which are increased by 421.90% and 581.37% compared with pure PVA. Finite element simulation of fracture mechanism shows good agreement with the experimental results. An improvement of thermal conductivity is also achieved in well-aligned SiCNWs/PVA. The work imitates the structure of mammal muscle and also has great potential for the macroscopic application of one-dimensional nanomaterials as super flexible heat dissipation materials.

CNT sponges with outstanding absorption capacity and electrical properties: Impact of the CVD parameters on the product structure

Abstract This work presents a detailed study of the influence of the synthesis parameters on the nanopowder-catalyzed CNT sponge production. Through electrochemical and absorption analyses, the sponges indicated a low resistivity (4.8x10−3 Ω m), capacitive behavior, very good cyclability and an elevated capacity of absorption of non-polar fluids (∼16 g/g). The polar character of the structure was easily modified by acid treatment allowing its further application in polar solutions. The produced sponge could be a practical tool for the recovery of water sources contaminated by non-polar substances. Additionally, it is a promising electrode in electrochemical processes with both polar and non-polar electrolytes.

On the reciprocating sliding wear of polypropylene against polyamide 6 in dry and aqueous environments

Polymer-polymer tribological components with sliding contacts usually are lighter, cheaper and more corrosion resistant in aqueous environment, presenting some advantages over the classic metal-polymer equivalents under certain conditions, such as in wear resistant external coatings for pipes in industry. Reciprocating sliding wear of polypropylene (PP) against polyamide 6 (PA6) in dry and aqueous environments (distilled water and synthetic sea water) was mapped as a function of contact pressure (2.4–7.2 MPa) and sliding speed (36–108 mm/s), aiming the identification of favorable operating conditions (low wear). Mild wear regime (k = 1.3–5.3 × 10−6 mm3/N m) was found for PP in all conditions, except for the highest sliding speed in dry environment, where there was a severe regime (k = 0.5–0.8 × 10−3 mm3/N m). Meanwhile, the PA6 counter-body always operated in the mild wear regime for all studied conditions. Wear mechanisms in the mild regime were: surface fatigue microcracks, film transfer and abrasion for both materials and, for PA6 only, also wear by roll formation. At higher speed, frictional heating (0.14 < μ < 0.25) and low thermal diffusivity of the materials resulted in high contact temperatures (up to 120 °C), which is enough to promote the removal of molten or softened material in the PP, typical of severe wear regime. The mild-to-severe wear regime transition observed for PP-PA6 tribopair occurs at a much lower sliding speed than in metal-polymer pairs, which may limit the applicability of these tribosystems. For PA6, the severity of surface damage as a function of the environment increased from dry to distilled water and sea water condition, as this material is susceptible to attack by polar solutions, which degrades its mechanical properties.

Synthesis, Characterization and Biological Evaluation of Some Azo and Azo-Schiff Compounds

This work involves the preparation of some new azo and azo-Schiff compounds derived from benzothiophene, dibenzothiophene, and diamines (1, 5-diaminonaphthalene, and thiocarbohydrazide). Azo compounds of benzothiophene and dibenzothiophene have been prepared using different solvents to enhance the miscibility of the polar aqueous solution of the diazonium salt and the slightly polar benzothiophene and dibenzothiophene. The Schiff’s bases have been synthesized by the condensation reaction of carbonyl compound with the diamines. FT-IR has been used to identify the prepared compounds, whereas 1H-NMR and 13C-NMR were used to identify some others. .

On polar actions invariant solutions of semi-linear equations on manifolds

In this paper we put together some tools from differential geometry and analysis to study second order semi-linear partial differential equations on a Riemannian manifold M. We look for solutions that are constants along orbits of a given group action. Using some results obtained by Helgason in [10] we are able to write a (reduced) second order semi-linear problem on a submanifold Σ. This submanifold is, in a sense, transversal to the orbits of the group actions and its existence is assumed. We describe precise conditions on the Riemannian Manifold M and the submanifold Σ in order to be able to write the reduced equation on Σ. These conditions are satisfied by several particular cases including some examples treated separately in the literature such as the sphere, surfaces of revolution and others. Our framework also includes the setup of polar actions or exponential coordinates. Using this procedure, we are left with a second order semi-linear equation posed on a submanifold. In particular, if the submanifold Σ is one-dimensional, we can use suitable tools from analysis to derive existence and properties of solutions.

Polar solutions with tensorial connection of the spinor equation

Dirac field equations are studied for spinor fields without any external interaction and when they are considered on a background having a tensorial connection with a specific non-vanishing structure some solution can be found in polar form displaying a square-integrable localized behaviour.

Rice Straw/Sewage Sludge-Based Composite Activated Carbon: Its Some Basic Properties and Adsorption Effect for Cr (VI)

In this study, the rice straw/sewage sludge-based composite activated carbon (RS-SCAC) was prepared from the mixture of sewage sludge and rice straw. Some basic properties of RS-SCAC, i.e., yield, iodine number, contents of heavy metals, surface functional groups, and leaching toxicity, were characterized. Furthermore, the adsorption performance of RS-SCAC for Cr (VI) was investigated. For RS-SCAC, the yield was moderate, and the iodine number was higher than that of the sewage sludge-based activated carbon (SBAC). RS-SCAC contained a variety of heavy metals, and Zn, Fe, and Cu had the relatively high content. The surface of RS-SCAC was rich in functional groups, especially for -OH, -COOH, and -COH, which was helpful for the adsorption of polar solute. For all heavy metals except Zn in RS-SCAC, the leaching concentrations were below the limits for identifying hazardous wastes, which indicated that RS-SCAC was relatively safe. Compared with SBAC, RS-SCAC had the better adsorption effect for Cr (VI). The results indicated that RS-SCAC can be used as a safety and efficient adsorbent for Cr (VI).

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

The active species of the Ishikawa´s reagent [N,N-diethyl-(1,1,2,3,3,3-hexafluoropropyl)amine] is a fluorinating hexafluoropropylamine used to convert alcohols into alkyl fluorides. On the other hand, it is also an example of model compound useful to probe conformational preferences using spectroscopic information from diastereotopic fluorines. Moreover, the possibility of experiencing both the generalized anomeric and gauche effects makes the Ishikawa´s reagent an ideal choice to study the governing stereoelectronic interactions of the conformational equilibrium of organofluorine compounds. The conformational equilibrium of the Ishikawa´s reagent was analyzed using NMR 3JH,F coupling constant data in different solvents, since the orientation of the diastereotopic fluorines relative to H-2 and F-2 changes with the medium. In nonpolar cyclohexane solvent, the preferred conformation experiences a weaker steric and electrostatic repulsion. The conformational behavior changes in the more polar pyridine solution, where the double fluorine gauche effect takes place, since F-2 is preferably gauche to both diastereotopic fluorines. An analysis of the rotation around the N–C(F2) bond indicates the manifestation of anomeric interactions (nN → σ*C–F), which can be demonstrated by means of 19F chemical shifts. The results were rationalized with the aid of theoretical calculations and natural bond orbital (NBO) analysis, allowing for the evaluation of competing steric, electrostatic and hyperconjugative interactions.

Enthalpy-Entropy Interplay in π-Stacking Interaction of Benzene Dimer in Water.

Aromatic groups can engage in an interesting class of noncovalent interactions termed π-π interactions, which play a pivotal role in stabilizing a variety of molecular architectures, including nucleic acids, proteins, and supramolecular assemblies. When the aromatic compounds interact with each other in an aqueous environment, their association is facilitated by the hydrophobic effect-the trend of nonpolar solutes to aggregate in a polar solution. To develop an in-depth understanding of hydrophobic association, we investigate in the present work π-π interactions in water, employing as a paradigm the benzene dimer. Using DFT-CES, a mean-field QM/MM method recently developed by our group, we describe the benzene solute at a quantum-mechanical level. Full consideration of detailed solute-electron density enables an optimal description of the solute-solvent interactions, leading to an accurate prediction of hydration free energies. In π-stacking of benzene, we find an entropic stabilization associated with the shrinkage of the solvent-excluded volume, which agrees with the theory of hydrophobic effect at subnanoscales. However, at the equilibrium binding distance of the benzene dimer, we find that the entropic stabilization nearly cancels out due to the enthalpic cost required for dewetting the internal space. Such an enthalpy-entropy compensation leads the association free energy to be predominantly dictated by the solute-solute interaction enthalpy. The present work offers new insight into the mechanistic role of water and the primary thermodynamic driving force of hydrophobic association.

Экстракция ионов из полярного раствора с использованием поверхностно-модифицированного мембранного интерфейса

The possibility of field extraction of ions from a polar solution was demonstrated using a polymer track membrane with a conductive coating as an interface. The time-of-flight spectrum of ions extracted from a KI solution in a water-glycerin mixture by a nanosecond electric field pulse was obtained. The use of a conductive coating made it possible to significantly lower the voltage of the extracting pulse and reduce the influence of secondary processes on the composition of ions generated in a pulsed membrane ion source.

Mass fraction assignment of Amino Acids in acidic aqueous solution (CCQM-K78.a)

The CCQM-K78.a comparison was coordinated by the BIPM on behalf of the CCQM Organic Analysis Working Group for NMIs and DIs which provide measurement services in organic analysis under the CIPM MRA. The key comparison forms part of the OAWG 10-year strategic plan of comparisons. CCQM-K78.a underpins the demonstration of capabilities for value assignment of high polarity calibration solutions. The model system selected was amino acids in aqueous solution.Participants were required to assign the mass fractions, expressed in μg/g, of phenylalanine (Phe), leucine (Leu), isoleucine (Ile) and proline (Pro) present in solution in 0.01 N hydrochloric acid. The content and analytical challenges of the selected analytes are representative of those for typical calibration solutions for polar organic analytes in aqueous solution.Participation in CCQM-K78, a benchmarked measurement capability for assigning the mass fraction content of polar organic compounds (pKow > -2) present at a mass fraction range between 50 μg/g and 500 μg/g in an aqueous solution. It also tested capabilities for the quantitative assignment of isomeric polar compounds of similar chromatographic retention time properties.A satisfactory level of agreement of the results was obtained between participants and with gravimetric values for amino acid content. In the cases where the agreement was not satisfactory, the participants were able to identify a technical cause for the inconsistency.The comparison demonstrated the trueness and precision of double IDMS-based methods as a primary measurement procedure for the quantification of polar analytes in aqueous solution when an isotopically labelled version of the analyte is available as the internal standard. It also demonstrated that amino acid quantification using pre- or post-column derivatization with UV or FLD detection can provide results with comparable levels of performance.In this case, where the purity of the primary calibrators had been assigned with a relative standard uncertainty below 0.2%, results consistent with the KCRV within a relative expanded uncertainty in the range 1% - 2% could be realized and levels of 2%-4% were routinely achieved.KEY WORDS FOR SEARCHAmino acid quantification, leucine, isoleucine, proline, phenylalanine, calibration solution, standard solution, IDMS, primary measurement procedure, polar solution, peptide quantificationMain textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Modeling of the Evolution of Cluster-Size Distribution Functions in Polar Fullerene C60 Solutions

We propose a method for calculating the evolution of the cluster-size distribution functions of fullerene C60 aggregates in polar solutions within the previously developed limited growth model. This method allows calculation of the distribution function f(r,t) at arbitrary moments of time for the given parameters of the system. As an example, we calculate the evolution of the mean cluster size, concentrations of monomers, and f(r,t) for a model polar solution of fullerenes. Small-angle neutron scattering curves at different times from the onset of C60 aggregation in the solution are obtained.

A Polar Liquid Zwitterion Does Not Critically Destroy Cytochrome c at High Concentration: An Initial Comparative Study with a Polar Ionic Liquid

A polar carboxylate-type zwitterion with a small volume of water can dissolve cytochrome c without significant disruption, compared with the case of a popular polar carboxylate-type ionic liquid, 1-ethyl-3-methylimidazolium acetate. A change in the Soret, Q, and 615nm bands was not observed in the 80 wt-% polar zwitterion solution, whereas a shift in the Soret band, diminishing Q band, and appearance of the 615nm band was found in the 80 wt-% polar ionic liquid solution. It suggests that concentrated polar ionic liquid solutions critically disrupt the structure of cytochrome c, and the polar zwitterion solution used in this study was better than a 1-ethyl-3-methylimidazolium acetate solution in a high concentration range.

Effect of Danhong Injection Combined with Magnesium Polarization Solution and Nitrate in Treating Coronary Heart Disease

AbstractObjective: To observe the effect of Danhong injection combined with magnesium polarized solution and nitrate on coronary heart disease.Methods: A total of 58 patients who had been diagnosed with coronary heart disease who participated in the voluntary study were selected and divided into observation group and control group. The number of patients in the two groups was 29, and the control group was mainly injected with nitroglycerin. The observation group was mainly treated with Danhong injection combined with magnesium polarized solution and nitrate ester. The main comparisons was the difference of clinical treatment effect, total cholesterol before and after treatment between the two groups of patients under different therapeutic drugs and the differences in endothelin were recorded.Results: The observation group was superior to the control group in terms of clinical treatment effect and total cholesterol and endothelin after treatment.Conclusion: Danhong injection combined with magnesium polarized solution and nitrate ester has a good effect in the treatment of coronary heart disease, which can be promoted and developed.

Hydration Thermodynamics of Non-Polar Aromatic Hydrocarbons: Comparison of Implicit and Explicit Solvation Models.

The precise description of solute-water interactions is essential to understand the chemo-physical nature in hydration processes. Such a hydration thermodynamics for various solutes has been explored by means of explicit or implicit solvation methods. Using the Poisson-Boltzmann solvation model, the implicit models are well designed to reasonably predict the hydration free energies of polar solutes. The implicit model, however, is known to have shortcomings in estimating those for non-polar aromatic compounds. To investigate a cause of error, we employed a novel systematic framework of quantum-mechanical/molecular-mechanical (QM/MM) coupling protocol in explicit solvation manner, termed DFT-CES, based on the grid-based mean-field treatment. With the aid of DFT-CES, we delved into multiple energy parts, thereby comparing DFT-CES and PB models component-by-component. By applying the modified PB model to estimate the hydration free energies of non-polar solutes, we find a possibility to improve the predictability of PB models. We expect that this study could shed light on providing an accurate route to study the hydration thermodynamics for various solute compounds.

Why Are Saccharides Dehydrated in the Presence of Electrolytes? Insights from Molecular Modeling and Thermodynamic Measurements.

The mechanisms governing the interactions of neutral polar solutes with ions in aqueous solutions are still poorly understood, despite the importance of this phenomenon in many fields (chemistry, physicochemistry, biology, food industries). In order to go further through the understanding of the molecular mechanisms governing the ions’ specific effects, this paper presents a generic method dealing with the characterization and understanding of interactions between saccharides and ions in aqueous systems. For that, an original approach combining a computational technique and experimental measurements (thermodynamic properties) is proposed to explain and rationalize the relationship between the solute hydration and the physical chemistry of the ions in solution (cation/anion, charge, size, and hydration). These relationships make it possible to evaluate the hydration state of a saccharide, a polar neutral molecule, according to the ionic composition, from the knowledge of the ions’ hydration properties. This work proposes new insight into molecular mechanisms governing the polar neutral solute/ion interactions and a new understanding of the hydration phenomenon in electrolytic solutions.

Unravelling the Improved Electronic and Structural Properties of Methylammonium Lead Iodide Deposited from Acetonitrile

Perovskite-based photovoltaics are an emerging solar technology with lab scale device efficiencies of over 22 %, and significant steps are being made toward their commercialization. Conventionally high efficiency perovskite solar cells are formed from high boiling point, polar aprotic solvent solutions. Methylammonium lead iodide (CH3NH3PbI3) films can be made from a range of solvents and blends; however, the role the solvent system plays in determining the properties of the resulting perovskite films is poorly understood. Acetonitrile (ACN), in the presence of methylamine (MA), is a viable nontoxic solvent for fabrication of CH3NH3PbI3 photovoltaic devices with efficiencies >18 %. Herein we examine films prepared from ACN/MA and dimethylformamide (DMF) and scrutinize their physical and electronic properties using spectroscopy, scanning probe imaging, and ion scattering. Significant differences are observed in the chemistry and electronic structure of CH3NH3PbI3 films made with each solvent, ACN/MA produc...

A Composite Model for the Transport of Hydrophilic and Lipophilic Compounds Across the Skin: Steady-State Behavior

A porous pathway feature has been added to an existing skin diffusion model to extend the range of applicability to highly polar solutes that do not readily diffuse across the stratum corneum (SC) lipid/corneocyte matrix. The porous pathway consists of 2 components: Pathway A is appendageal and is implemented as an array of aqueous shunts (the macropores), which themselves have microporous walls with transient aqueous pores (the micropores). Two varieties of shunts are discussed, one representing a terminal hair follicle and the other representing an eccrine sweat duct; however, the focus here is on the hair follicle. Pathway B is transcellular, with lipid-phase transport accomplished through defects or breaks in the bilayer lipid structure. The composite model admits polar solutes into the skin in a size-selective manner with an effective micropore radius of 1.6 nm. Steady-state permeabilities, desorption rates from isolated SC, and SC/water partition coefficients of both polar and lipophilic solutes are effectively explained.

Effects of Hydrogen Bonding on Diffusion of Aromatic Compounds in Acetone: An Experimental Investigation from 268.2 to 328.2 K.

Diffusion coefficients of pseudoplanar aromatic compounds at infinite dilution in acetone have been measured at different temperatures by the Taylor dispersion technique. The data of the polar solutes that can form hydrogen bonds with acetone are compared with those of the nonpolar ones incapable of hydrogen bonding to quantify the effects of hydrogen-bonded association on diffusion. The effects are further found to correlate strongly with the overall hydrogen-bonded acidity of the polar solutes containing proton-donating groups. For the nonpolar solutes in this study, the diffusivities at different temperatures can be expressed very well by the recently developed molecular-modified fractional Stokes-Einstein relation with only two constants. An innovative model for solute diffusion in liquid solutions, which is constructed by combining the molecular-hydrodynamic relation for nonpolar solutes with the overall hydrogen-bonded acidity scale for polar solutes, is introduced for representing the diffusivities of different types of disc-shaped molecules at various temperatures. An equation developed from this model is demonstrated to be capable of calculating a total of 191 diffusion data of both the hydrogen-bonded and the nonassociated aromatic solutes in acetone from 268.2 to 328.2 K to a standard deviation of 2.7%.