Solvent Species Research Articles

Semiconducting properties of p- and n-type organic nanofiber/poly(methyl methacrylate) composite films for film rectifier

We investigated the field-effect mobility of regioregular poly(3-hexylthiophene) (P3HT) and N,N′-ditridecyl-3,4,9,10-perylenetetracarboxyl diimide (PTCDI-C13) nanofibers composited in poly(methyl methacrylate) (PMMA) with varying P3HT/PMMA or PTCDI-C13/PMMA ratio, solvent species, and doping concentration by fabricating the field effect transistor (FET) of these composite films. Both composite films functioned as a p- or n-type semiconducting layer of FET, and the apparent field-effect mobility gradually increased with increasing P3HT or PTCDI-C13 ratio, and was estimated to be about 4.7×10−3cm2V−1s−1 (P3HT nanofiber/PMMA composite, P3HT weight ratio=10%) and 2.0×10−5cm2V−1s−1 (PTCDI-C13 nanofiber/PMMA composite, PTCDI-C13 weight ratio=20%). In addition, a pn junction between P3HT nanofiber/PMMA and PTCDI-C13 nanofiber/PMMA composite films was fabricated to examine the rectifying effect. The rectifying effect was obtained and an appropriate diode region was observed in the forward current with the ideal factor n of 2.30. The rectifying effect can be derived by a simple fabrication method, i.e., simply pasting n- and p-type flexible films together, which gives us a novel methodology for fabricating flexible semiconducting devices.

Effect of solvent species inside wet gel on fabrication of titania nanoparticle by supercritical carbon dioxide drying

Titania nanoparticles were fabricated by sol–gel reaction and supercritical carbon dioxide drying. The solvent inside wet gel obtained from sol–gel reaction was exchanged to organic solvents, acetone, 1-butanol and N-methylpyrrolidone before the supercritical drying. The wet gels exchanged by organic solvents were dried in supercritical carbon dioxide at 313K and 10.0 and 20.0MPa. It is found that the structures of the titania nanoparticles were like nano-needle. The minor-axis sizes of the nano-needle titania nanoparticles were measured by a scanning electron microscope observation. The wet gel exchanged by 1-butanol results in the smallest minor-axis of titania nanoparticles, 97nm in the supercritical drying at 313K and 20.0MPa. The drying of the wet gel exchanged with N-methylpyrrolidone exhibit the reduction of the minor-axis of titania nanoparticle larger than those with acetone and 1-butanol, 181 to 103nm by increase of pressure, 10.0 to 20.0MPa.

Self-organization of hydrophobic-capped triblock copolymers with a polyelectrolyte midblock: a coarse-grained molecular dynamics simulation study.

We present the results of a Langevin dynamics simulation study of micellar organization and hydrogel formation in the solutions of coarse-grained ABA copolymer chains. Polymer chains are modeled as bead-spring chains of Lennard-Jones particles by explicit treatment of ionic species in implicit solvent. The studied copolymer is composed of a polyelectrolyte midblock flanked by two hydrophobic endblocks. We explore the self-assembly of copolymer solutions at a fixed polymer concentration and temperature upon systematic variation of the midblock charge fraction, valency of neutralizing counterions, and the stiffness and length of hydrophobic endblocks. Minimization of the surface energy, conformational entropy of the midblock chains, electrostatic repulsion of midblock charges, and the translational entropy of counterions are found to play central roles in controlling the self-organization features of copolymer solutions. Flower-like micelles with A-blocks forming the core of spherical aggregates and B-blocks constituting the micelle corona are established for the neutral midblocks. Increasing the charge content of B chains lowers the fraction of loop conformations and yields a spanning hydrogel network with midblocks bridging the hydrophobic clusters. Counterion valence is shown to exert a strong effect on the micelle size and network structure. The increase in the rigidity of terminal A-blocks increases the fraction of bridging chains and results in the formation of a hydrogel network with bundle-like hydrophobic domains. Longer endblocks are shown to increase the hydrophobic cluster size and enhance the bridged midblock fraction. The qualitative agreement between the experimental and theoretical studies is also discussed. The comprehensive molecular picture provides a framework for the future studies of stimuli-responsive copolymer systems.

Long-term effects of multiply pulsed dielectric barrier discharges in air on thin water layers over tissue: stationary and random streamers

Tissue covered by thin liquid layers treated by atmospheric pressure plasmas for biomedical applications ultimately requires a reproducible protocol for human healthcare. The desired outcomes of wet tissue treatment by dielectric barrier discharges (DBDs) depend on the plasma dose which determines the integral fluence of radicals, ions, electric fields and UV/VUV photons incident onto the tissue. These fluences are controlled by power, frequency and treatment time. To first order, these parameters determine the energy deposition (J cm−2) onto the tissue. However, energy deposition may not be the only parameter that determines the fluences of reactants to the underlying tissue. In this paper, we report on a computational investigation of multipulse DBDs interacting with wet tissue. The DBDs were simulated for 100 pulses at different repetition rates and liquid thicknesses followed by 10 s or more of afterglow. Two schemes were investigated—stationary and random. In the stationary scheme, the DBD plasma streamer continues to strike at the same location on the liquid layer, whereas in the random scheme the plasma streamer strikes at random locations on the liquid layer. These differences in streamer locations strongly affect the spatial distribution of solvated species such as OHaq and H2O2aq (‘aq’ represents an aqueous species), which have high rates of solvation. The spatial distribution of species such as NOaq, which have low rates of solvation, are less affected by the location of the streamer due to the remediating effects of diffusion in the air. The end result is that fluences to the tissue are sensitive to the spatial location of the streamer due to the ensuing reactions in the liquid between species that have low and high rates of solvation. These reactions can be controlled not only through location of the streamer, but also by repetition rate and thickness of the liquid layer.

Solubility of C60 and PCBM in Organic Solvents.

The ability to correlate fullerene solubility with experimentally or computationally accessible parameters can significantly facilitate nanotechnology nowadays for a wide range of applications, while providing crucial insight into optimum design of future fullerene species. To date, there has been no single relationship that satisfactorily describes the existing data clearly manifesting the effects of solvent species, system temperature, and isomer. Using atomistic molecular dynamics simulations on two standard fullerene species, C60 and PCBM ([6,6]-phenyl-C61-butyric acid methyl ester), in a representative series of organic solvent media (i.e., chloroform, toluene, chlorobenzene, 1,3-dichlorobenzene, and 1,2-dichlorobenzene), we show that a single time constant characterizing the dynamic stability of a tiny (angstrom-sized) solvation shell encompassing the fullerene particle can be utilized to effectively capture the known trends of fullerene solubility as reported in the literature. The underlying physics differs substantially between the two fullerene species, however. Although C60 was previously shown to be dictated by a diffusion-limited aggregation mechanism, the side-chain-substituted PCBM is demonstrated herein to proceed with an analogous reaction-limited aggregation with the "reaction rate" set by the fullerene rotational diffusivity in the medium. The present results suggest that dynamic quantities-in contrast to the more often employed, static ones-may provide an excellent means to characterize the complex (entropic and enthalpic) interplay between fullerene species and the solvent medium, shed light on the factors determining the solvent quality of a nanoparticle solution, and, in particular, offer a practical pathway to foreseeing optimum fullerene design and fullerene-solvent interactions.

A homogeneous polysulfone nanofiltration membrane with excellent chlorine resistance for removal of Na2SO4 from brine in chloralkali process

A homogeneous polysulfone nanofiltration membrane with a dense structure was fabricated by solvent evaporation method. Two solvents, tetrahydrofuran (THF) and dimethylacetamide (DMAc), were utilized to prepare the membranes with tunable pores around 1.0nm. The pore size was affected by the solvent species, and it decreased when THF was replaced by DMAc. Correspondingly, the rejections to Na2SO4 of the membranes fabricated with DMAc (80–82%) were higher than those of the membranes fabricated with THF (65–67%). To further improve the performance, by applying a higher membrane formation temperature (110°C), the pore size became even smaller and the rejection to Na2SO4 was improved to 87%. The feasibility of removing sulfate ions from brine by the membrane was proved by rejection to Na2SO4 of 80% and rejection to NaCl of almost zero in the mixed salt solution. The structure of the membrane was independent of the thickness, and thus the flux could be gradually improved by reducing the thickness while maintaining a high rejection. Moreover, the membrane had high mechanical strength larger than 66MPa and excellent chlorine resistance. It kept good separation performance even after exposed to the 50,000ppm sodium hypochlorite solution for 24h.

A Generalized Mathematical model to understand the capacity fading in lithium ion batteries-Effects of solvent and lithium transport

A general mathematical model to study capacity fading in lithium ion batteries is developed. The model assumes that the formation of the Solid Electrolyte interphase(SEI) layer is the primary reason behind the capacity fading in lithium ion batteries. Previous models have assumed that either the solvent or the lithium plays a key role in the film formation reaction which drives the capacity fading in lithium ion batteries. The current model postulates that the solvent species and lithium ions could play a limiting role in the capacity fade in a lithium ion battery. The model studies the concentration profiles of the solvent species and lithium ions at the electrode/film interphase as a function of diffusion and migration parameters. Model predictions are found to fit experimental data very well.

Phase- and morphology-controlled synthesis of cobalt sulfide nanocrystals and comparison of their catalytic activities for hydrogen evolution

Colalt sulfide nanocrystals (NCs), including dandelion-like Co9S8 and sphere-like Co3S4, have been synthesized via a thermal decomposition approach using cobalt acetylacetonate as the cobalt source, 1-dodecanethiol as the sulfur source and oleic acid or oleylamine as the high boiling organic solvent. It is found that the molar ratio of the Co:S precursor and the species of solvent play an important role in the control of phase and morphology of cobalt sulfide nanostructures. The phase structure and morphology of the as-synthesized nickel sulfide NCs are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), energy dispersive spectrum (EDS) mapping, X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption. Then we further compare the electrocatalytic activity and stability of as-synthesized cobalt sulfide NCs for hydrogen evolution reaction (HER). The results show that sphere-like Co3S4 exhibits better electrocatalytic activity than the dandelion-like Co9S8 NCs for HER, which can be attributed to the difference of phase structure and morphology. The sphere-like Co3S4 NCs have large surface area and high electrical conductivity, both are beneficial to enhance the catalytic activity. This study indicates that the crystalline phase structure and morphology of cobalt sulfide NCs are important for designing HER electrocatalysts with high efficiency and good stability.

Solubility of Natural Gas Species in Ionic Liquids and Commercial Solvents: Experiments and Monte Carlo Simulations

A detailed comparison of the solubility of carbon dioxide (CO2) and methane (CH4) in ionic liquids (ILs) and in conventional solvents like Selexol, Purisol, propylene carbonate, and sulfolane is presented. The solubilities are compared on mole fraction, molality, and volume basis to demonstrate the effect caused by the high molecular weight of ILs. We found that conventional solvents are superior to existing ILs in terms of mass- or volume-based solubilities. Monte Carlo simulations have been used to quantitatively predict the solubility of CO2, CH4, and C2H6 in the solvents 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [hmim][Tf2N] and tetraethylene glycol dimethyl ether.

CLOUD POINT EXTRACTION, PRECONCENTRATION, SPECTROPHTOMETRIC, DETERMINATION OF MAGNESIUM (II) BY USING 2,4-DIMETHYL-PENTAN-3-ONE

The cloud point extraction (CPE) method has been applied to the extraction and pre-concentration of Mg 2+ ions. The extracted solvated species showed a maximum absorbance at λ max = 249 nm. The optimum conditions for extraction of solvated species to CPL are the presence of 0.5 M KNO 3 for 50 µg Mg 2+ ion in 10 ml aqueous solution with 1×10 -4 M of extractant, 2,4-dimethyl-pentan-3-one (2,4-DMP) and heating up to 90 °C for 15 minutes and addition of 0.5 mL of 1 % Triton X–100 as surfactant. The study showed that different extractant have different extraction efficiency, acetophenone showing higher extraction efficiency but ethyl methyl ketone has a lower efficiency. The effect of different salts and variable concentration of nitrate salts on the extraction efficienct has been studied. Determination of Mg 2+ in different samples has been studied with a RSD = 0.0074, DL = 1.84×10 -5 and Sandel’s sensitivity = 3.58 ×10 -9 μg cm -2 .

Two terphenyl-based diol hosts and corresponding solvent inclusions with dimethylformamide and acetonitrile.

Having reference to an elongated structural modification of 2,2'-bis(hydroxydiphenylmethyl)biphenyl, (I), the two 1,1':4',1''-terphenyl-based diol hosts 2,2''-bis(hydroxydiphenylmethyl)-1,1':4',1''-terphenyl, C44H34O2, (II), and 2,2''-bis[hydroxybis(4-methylphenyl)methyl]-1,1':4',1''-terphenyl, C48H42O2, (III), have been synthesized and studied with regard to their crystal structures involving different inclusions, i.e. (II) with dimethylformamide (DMF), C44H34O2·C2H6NO, denoted (IIa), (III) with DMF, C48H42O2·C2H6NO, denoted (IIIa), and (III) with acetonitrile, C48H42O2·CH3CN, denoted (IIIb). In the solvent-free crystals of (II) and (III), the hydroxy H atoms are involved in intramolecular O-H···π hydrogen bonding, with the central arene ring of the terphenyl unit acting as an acceptor. The corresponding crystal structures are stabilized by intermolecular C-H···π contacts. Due to the distinctive acceptor character of the included DMF solvent species in the crystal structures of (IIa) and (IIIa), the guest molecule is coordinated to the host via O-H···O=C hydrogen bonding. In both crystal structures, infinite strands composed of alternating host and guest molecules represent the basic supramolecular aggregates. Within a given strand, the O atom of the solvent molecule acts as a bifurcated acceptor. Similar to the solvent-free cases, the hydroxy H atoms in inclusion structure (IIIb) are involved in intramolecular hydrogen bonding, and there is thus a lack of host-guest interaction. As a result, the solvent molecules are accommodated as C-H···N hydrogen-bonded inversion-symmetric dimers in the channel-like voids of the host lattice.

Investigating the Mechanism of Copper(0)-Mediated Living Radical Polymerization in Organic Media

Single electron transfer living radical polymerization (SET-LRP) is a versatile polymerization tool that allows for the synthesis of functional materials for a range of potential applications. An interesting scientific debate has dominated the literature during the past few years regarding the mechanism of Cu(0)-mediated polymerizations in both aqueous and organic media. This article is the first part of a mechanistic study regarding the role of Cu(0) and CuBr in these systems with the aim of offering some increased level of understanding of the mechanism to aid application. In this current contribution, disproportionation and comproportionation studies reveal significant variations in the thermodynamic and kinetic equilibria depending on the solvent composition, the nature of the monomer and the ligand concentration. Interestingly, the sequence of reagent addition significantly affects the disproportionation equilibrium, which is attributed to competitive complexation reactions between monomer, solvent, ligand, and copper species. The Cu(0) generated via the in situ disproportionation of [Cu(Me6TREN)]Br in DMSO prior to addition of monomer and initiator were demonstrated to contribute in different extents over the rate and control of the polymerization, depending on the equivalents of ligand employed. It was found that an increase in the concentration of the Cu(0) particles result in slower polymerization rates while when conditions that stabilize CuBr were employed, faster polymerization rates were observed. On the contrary, 5 cm of copper wire showed faster polymerization rates when compared with 9.4 mM of CuBr, highlighting that copper wire is essential for the efficient polymerization of acrylates in organic solvents.

Examining the aggregation behavior of polymer grafted nanoparticles using molecular simulation and theory.

Grafting polymers to nanoparticles is one approach used to control and enhance the structure and properties of nanomaterials. However, predicting the aggregation behavior of tethered nanoparticles (TNPs) is a somewhat trial and error process as a result of the large number of possible polymer tethers, nanoparticles, and solvent species that can be studied. With the main goal of understanding how to control the dispersion and aggregation of TNP systems, molecular simulations and the hetero-statistical associating fluid theory for potentials of variable range have been used to calculate the fluid phase equilibrium of TNPs in both vacuum and in simple solvents under a wide range of conditions. The role of graft length, graft density, and solvent interactions is examined and trends established. Additionally, the fluid distribution ratio (k value) is used to study the solubility of TNPs in industrially relevant solvents including carbon dioxide, nitrogen, propane, and ethylene.

Universality of Viscosity Dependence of Translational Diffusion Coefficients of Carbon Monoxide, Diphenylacetylene, and Diphenylcyclopropenone in Ionic Liquids under Various Conditions.

Translational diffusion coefficients of diphenylcyclopropenone (DPCP), diphenylacetylene (DPA), and carbon monoxide (CO) in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIm][NTf2]) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIm][NTf2]) were determined by the transient grating (TG) spectroscopy under pressure from 0.1 to 200 MPa at 298 K and from 298 to 373 K under 0.1 MPa. Diffusion coefficients of these molecules at high temperatures in tributylmethylphosphonium bis(trifluoromethanesulfonyl)imide ([P4441][NTf2]), and tetraoctylphosphonium bis(trifluoromethanesulfonyl)imide ([P8888][NTf2]), and also in the mixtures of [BMIm][NTf2], N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ([Pp13][NTf2]), and trihexyltetradecylphosphonium bis(trifluoromethanesulfonyl)imide ([P66614][NTf2]) with ethanol or chloroform have been determined. Diffusion coefficients except in ILs of phosphonium cations were well scaled by the power law of T/η, i.e., (T/η)(P), where T and η are the absolute temperature and the viscosity, irrespective of the solvent species, pressure and temperature, and the compositions of mixtures. The values of the exponent P were smaller for the smaller size of the molecules. On the other hand, the diffusion coefficients in ILs of phosphonium cations with longer alkyl chains were larger than the values expected from the correlation obtained by other ILs and conventional liquids. The deviation becomes larger with increasing the number of carbon atoms of alkyl-chain of cation, and with decreasing the molecular size of diffusing molecules. The molecular size dependence of the diffusion coefficient was correlated by the ratio of the volume of the solute to that of the solvent as demonstrated by the preceding work (Kaintz et al., J. Phys. Chem. B 2013 , 117 , 11697 ). Diffusion coefficients have been well correlated with the power laws of both T/η and the relative volume of the solute to the solvent.

Influence of solvent polarity on surface-fluorination of cellulose nanofiber by ball milling

Ball mill-assisted surface-fluorination of cellulose nanofiber was studied for two solvents with different polarity as dispersion/reaction medium. Milling cellulose in neat toluene gave irregular-shaped decrystallized cellulose particles; addition of pentafluorobenzoyl chloride (PFBC) to the system gave partially fluorinated cellulose as thin flakes with smooth surfaces, which maintained original crystallinity. Milling in neat dimethyl formamide (DMF) caused partial dispersion of nanofibers without decrystallization; milling in PFBC/DMF gave more enhanced dispersion of surface-fluorinated nanofibers. Both fluorinated materials were hydrophobic, with water contact angles of 103°–113°. Bulk degree of esterification was 0.20 for toluene and 0.57 for DMF systems. These results show characteristic influences of solvent species in reactive ball milling of cellulose in terms of fibrillation and surface esterification of nanofibers.

Highly Concentrated Catholyte Based on Solvate Ionic Liquid for Flow Battery

Liquid based batteries, including a flow battery, have unique and significant benefits due to its simple structure and flexible handling of their liquid active materials as ‘electrochemical fuels’. In spite of this great ‘fueling’ capability, which may enable the rapid charging of electric vehicles, the energy density of the regular catholytes and anolytes is lower (<100 Wh/l) than that of the solid-state active materials used in regular batteries. A non-aqueous system is a simple and effective method of improving the discharging voltage more than 2 V, which is the limit of the aqueous system, coupling with highly negative anodes. The concentration of redox species in organic solvents is, however, generally lower than that in aqueous solutions and difficult to reach over 2 M with, at least, the same molar of supporting salt. It is important to note that stoichiometric couples of redox species and an appropriate salt is the minimum requirement for the liquid active materials because the valence of the redox species must be changed during discharging and charging and compensating ions must be present in the system. Moreover, the liquids should have a stable fluidic property without freezing or precipitation even in a low temperature range. In this study, we report an innovative strategy to prepare the liquid active materials in order to increase their energy density. Our technology focuses on the melting of pure redox compounds to maximize their concentration instead of dissolving them in solvents. This simple yet challenging approach has been successfully realized using supercooled liquid technology by the combination of a specific plasticizing salt and a low melting point redox active compound. Such a supercooled liquid can be obtained by mixing of 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-methoxy-TEMPO, MT) and Li bis(trifluoromethanesulfonyl) imide (LiTFSI, LT) and stabilizing the mixture further below their melting points. The redox-active supercooled liquid exists in a highly stable liquid state over a wide temperature range that extends to below its normal melting points. The special properties of this supercooled liquid are due to the scientifically unique and rare solvation state known as a ‘solvate ionic liquid’, which is typified by a liquefied ion-pair stabilized by a neutral third compound. As a catholyte, the addition of an appropriate amount of solvent such as water helps to enhance the electrochemical advantage while maintaining the liquid’s supercooled nature, and a battery with a Li+ conducting architecture exhibits 93% electrochemical activity and 99% coulombic efficiency in the 1st cycle with an average discharge voltage of 3.6 V (Fig. 1). The catholyte also performed an energy density of 200 Wh/l, which is one of the highest values for catholytes reported to date with an organic redox compound. Figure 1

Multiscale Modeling of a Proton Exchange Membrane Fuel Cell: Effect of Electric Double Layer Structure

Proton Exchange Membrane Fuel Cells (PEMFCs) are very promising to generate electric energy for transport and electronic devices because they produce minimal pollutant emissions and can operate at low temperature [1]⁠. Despite of enormous progresses made to date, this technology has to reach all technical requirements in order to be competitive.The presence of solvated cations as charge-transporting species has a direct influence on the potential profile at interfaces involved in PEMFCs. This leads to a shift in the electric potential acting on the reactants and modifies their activation energies. In this way, the rate of mass and charge transfer processes are determined by the electric double layer (EDL) morphology and structure. For instance, a simple modification in the medium permittivity close to the surface results in appreciable increase of the apparent reaction rate constant [2].The importance of EDL structure on transfer mechanisms has led to several researches based on mean field theories and molecular simulations [3-4]. However, an integration of EDL structure simulations with PEMFC reaction model is still lacking. This will contribute to understand and cuantify the effect of electrolyte and solvent compositions on the reaction kinetics.In order to simulate the EDL structure and its modifications with respect to applied potential and solution composition, it is required a proper molecular model that resembles the size, polar and chemical characteristics of reactants, electrolyte and solvent species involved in PEMFCs, which is proposed to carry out in this work by means of molecular dynamics (MD) simulations.The results achieved by molecular simulations would enable to evaluate the modification of reaction rates by the EDL structure, under an applied potential in PEMFC. In order to accomplish this, it is employed the Stillinger-Weber interaction potential of water and platinum [7], coupled with electrostatic interactions for the molecular simulations of EDL.

Ab Initio Approach for Prediction of Oxide Surface Structure, Stoichiometry, and Electrocatalytic Activity in Aqueous Solution.

The design of efficient, stable, and inexpensive catalysts for oxygen evolution and reduction is crucial for the development of electrochemical energy conversion devices such as fuel cells and metal-air batteries. Currently, such design is limited by challenges in atomic-scale experimental characterization and computational modeling of solid-liquid interfaces. Here, we begin to address these issues by developing a general-, first-principles-, and electrochemical-principles-based framework for prediction of catalyst surface structure, stoichiometry, and stability as a function of pH, electrode potential, and aqueous cation concentration. We demonstrate the approach by determining the surface phase diagram of LaMnO3, which has been studied for oxygen evolution and reduction and computing the reaction overpotentials on the relevant surface phases. Our results illustrate the critical role of solvated cation species in governing the catalyst surface structure and stoichiometry, and thereby catalytic activity, in aqueous solution.

Effect of Solvent on Surface Ordering of Poly(3-hexylthiophene) Thin Films.

Enhancement of charge transport in organic polymer semiconductors is a crucial step in developing optimized devices. A variety of sample preparation conditions, such as film fabrication method, solvent species, and annealing, were found to influence the hole mobility of organic polymers. Despite the fact that many factors can influence their performance, it is believed that polymer surface ordering plays a key role in determining organic polymer function. Here, sum frequency generation (SFG) vibrational spectroscopy was used to nondestructively map the surface/interfacial ordering of poly(3-hexylthiophene) (P3HT) films prepared using different solvents; we believe that solvent interactions determine the degree of surface/interfacial ordering. Both X-ray diffraction (XRD) spectroscopy and scanning electron microscopy (SEM) were used to supplement SFG to systematically study bulk crystallinity and surface morphology. We conclude that SFG is a powerful tool to elucidate the surface/interfacial structural information on polymer semiconducting films. We demonstrate that the solvent composition used to prepare P3HT thin films influences the resulting film surface morphology, surface/interfacial ordering, and bulk crystallinity.

Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Inorganic Nonaqueous Electrolytes

Multi-valent (MV) battery architectures based on pairing a Mg metal anode with a high-voltage ($\sim$ 3 V) intercalation cathode offer a realistic design pathway toward significantly surpassing the energy storage performance of traditional Li-ion based batteries, but there are currently only few electrolyte systems that support reversible Mg deposition. Using both static first-principles calculations and $ab\; initio$ molecular dynamics, we perform a comprehensive adsorption study of several salt and solvent species at the interface of Mg metal with an electrolyte of Mg$^{2+}$ and Cl$^-$ dissolved in liquid tetrahydrofuran (THF). Our findings not only provide a picture of the stable species at the interface, but also explain how this system can support reversible Mg deposition and as such we provide insights in how to design other electrolytes for Mg plating and stripping. The active depositing species are identified to be (MgCl)$^+$ monomers coordinated by THF, which exhibit preferential adsorption on Mg compared to possible passivating species (such as THF solvent or neutral MgCl$_2$ complexes). Upon deposition, the energy to desolvate these adsorbed complexes and facilitate charge-transfer is shown to be small ($\sim$ 61 $-$ 46.2 kJ mol$^{-1}$ to remove 3 THF from the strongest adsorbing complex), and the stable orientations of the adsorbed but desolvated (MgCl)$^+$ complexes appear favorable for charge-transfer. Finally, observations of Mg-Cl dissociation at the Mg surface at very low THF coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode may occur upon plating. In the stripping process, this is beneficial by further facilitating the Mg removal reaction.