Solvent Treatment Research Articles

Optimal Solvents for Interfacial Solution Engineering of Perovskite Solar Cells

Interfacial engineering is extensively used to reduce the interfacial loss caused by surface recombination, improve the crystallinity of the active absorption layer, and enhance the long‐term stability of perovskite solar cells (PSCs). Solution processing techniques, such as spin coating and dip coating, are commonly used to deposit the interfacial layer because of their cost‐effectiveness and simplicity. Although determining suitable solutes for use in these processes is important, selecting appropriate solvents is also crucial. Herein, commonly used solvents are investigated to determine optimal solvents for solution processing by categorizing them into nonpolar and polar groups. The results suggest that the efficiency of the PSCs can be increased by simple solvent treatment. In particular, the efficiencies of systems subjected to hexane (nonpolar) and ethanol (polar) treatment are significantly improved (17.31% and 17.44%, respectively) compared with that of a control device (16.24%). Herein, the effects of pure solvents on the SnO2–perovskite interface are confirmed and an important direction for investigations that adopt solution processing to improve the efficiency of PSCs, such as research on interlayers and self‐assembled monolayers, is suggested.

Effects of chemical solvents on coal pore structural and fractal characteristics: An experimental investigation

Chemical solvent treatment is one of the most effective means to improve pore structure of low-permeability coal and increase production of coalbed methane. Low-temperature liquid nitrogen adsorption method, X-ray diffraction (XRD) mineral analysis and fractal theory were adopted to study variations in coal pore structural parameters and fractal characteristics affected by hydrochloric acid (HCl), tetrahydrofuran (THF) and carbon disulfide (CS2). Liquid nitrogen adsorption results of coal samples were analyzed using density functional theory (DFT), Brunauer-Emmett-Teller (BET) equation and Barrett-Johner-Halenda (BJH) model. Meanwhile, changes in fractal dimensions of pore surface (D1) and pore structure (D2) were calculated based on Frenkel-Halsey-Hill (FHH) model. Relationship between pore volume, average pore diameter, specific surface area and two fractal dimensions were established. Results show that: (1) Hysteresis lines exist in all isothermal adsorption-desorption processes of coal. Pores of raw coal are mainly semi-open pores with poor connectivity. The types of pores do not change significantly after THF and CS2 treatment, while the number of pores rise. In contrast, affected by HCl treatment, ink-bottle pores and open pores increase and pore fracture network connectivity becomes better. (2) Pore sizes of treated coal mainly distribute in range of 0–10 nm. After HCl treatment, many closed pores are opened, with growth in proportion of micropores. Meanwhile, specific surface area (SSA) of pores increases by 55.21% and 31.36%, respectively. THF extraction results in an increase in pore volume and SSA. After CS2 extraction, dissolution of organic material increases pore size and further improve volume of transition pores and mesopores. (3) HCl treatment causes decrease in D1 value of pores. However, in organic-solvent-treatment cases, solvent residues retain on coal pores, resulting in growth in D1 value and pore surface becoming rougher. Proportion of total pore volume of transition pores and mesopores of acidized coal decreases and D2 value rises. Pore distribution is more uneven. Relevant results could provide theoretical references for revealing mechanism of chemical solvents effects on gas flow in coal.

Lightweight, High-Strength Wood Prepared by Deep Eutectic Solvent Treatment as a Green Structural Material

Lightweight, High-Strength Wood Prepared by Deep Eutectic Solvent Treatment as a Green Structural Material

Constructing Favorable Microstructures in Solid-State Organic Cathodes Via Mechanical Property Manipulation

Organic electrode materials, due to their low environment footprint and high material-level specific capacities, have become competitive alternatives to inorganic materials for solid-state batteries (SSB) in recent years. Additionally, the soft nature of organic compounds ensures consistent and intimate contact with solid sulfide electrolytes during cycling, which is beneficial for battery longevity. However, the low-modulus organic materials and high-modulus sulfide electrolytes, upon mixing and compression, would form unfavorable composite microstructure where sulfide particles are encapsulated by organics and cannot form an efficient ion conduction path. This mismatch in mechanical property prevents a high fraction of organic compounds to be used in a solid-state cathode, limiting the energy density of organic solid-state batteries.Here we report the formation of favorable microstructures of organic cathodes by “softening” the sulfide electrolytes. Solvent treatment of the sulfide electrolyte Li6PS5Cl more than halves its modulus from 28.6 ± 8.5 GPa to 16.0 ± 1.6 GPa. Thermal gravimetric analysis, Raman spectroscopy, and X-ray diffraction were used to elucidate the evolution of the sulfide electrolyte during the softening and recovering process. The organic cathode formed by mixing organic materials with this softened electrolyte shows a favorable microstructure where the electrolyte forms a percolated domain. As a result, the utilization of an organic material, pyrene-4,5,9,10-tetraone (PTO), is increased by 133.6% and 90.8% compared with cells with a re-hardened and the pristine Li6PS5Cl, respectively. The mass fraction of PTO can be improved from 20 to 40wt% while maintaining high utilization (85.7%). Our exploration of softened electrolyte builds the correlation among structure, mechanical property, microstructure engineering and battery performance, and the strategy is applicable to other active materials with low modulus.

Recent Advances in Nonfullerene Acceptor-Based Layer-by-Layer Organic Solar Cells Using a Solution Process.

Recently, sequential layer‐by‐layer (LbL) organic solar cells (OSCs) have attracted significant attention owing to their favorable p–i–n vertical phase separation, efficient charge transport/extraction, and potential for lab‐to‐fab large‐scale production, achieving high power conversion efficiencies (PCEs) of over 18%. This review first summarizes recent studies on various approaches to obtain ideal vertical D/A phase separation in nonfullerene acceptor (NFAs)‐based LbL OSCs by proper solvent selection, processing additives, protecting solvent treatment, ternary blends, etc. Additionally, the longer exciton diffusion length of NFAs compared with fullerene derivatives, which provides a new scope for further improvement in the performance of LbL OSCs, is been discussed. Large‐area device/module production by LbL techniques and device stability issues, including thermal and mechanical stability, are also reviewed. Finally, the current challenges and prospects for further progress toward their eventual commercialization are discussed.

Observation of strain relaxing in nanoscale WS2 monolayers grown on SiO2/Si by organic solvent treatment

We investigated the optical properties of nanoscale WS2 monolayers treated with organic solvents. The photoluminescence spectra changed significantly before and after methanol treatment. The sharp spectral peak of the neutral exciton in the methanol-treated sample was shifted to the higher energy side by 18 meV compared to the peak in untreated sample. This shift made the emission peak due to charged excitons clearly visible. Detailed fitting analysis revealed that the methanol treatment relaxed the tensile strain in the nano-sized WS2 monolayer grown on SiO2/Si substrate. In addition to the measurements in air, the results in vacuum and their temperature dependence also support this interpretation. Since this methanol treatment is simple, does not cause sample loss, and does not reduce luminescence efficiency, it may be an effective means to relax strain from nanoscale transition metal dichalcogenides monolayers.

Vertically Oriented Metallic Heterodimer Array Semiembedded in Flat Conductive Carbon Film for Electrochemical Application.

General synthesis of a highly oriented metallic heterodimer array based on a selective electrodeposition technique onto a metal nanoparticle-embedded carbon film is proposed, which enables the preparation of heterodimers with a wide variety of metal combinations. This method requires no surfactant, capping agent, organic solvent, or heat treatment. As a representative metal combination, a nickel (Ni)/palladium (Pd) heterodimer array was prepared by selective electrodeposition of Ni nanoparticles (Ni NPs) on top of partially exposed Pd NPs embedded in carbon film electrodes fabricated by a cosputtering technique. Such a selective electrodeposition becomes possible by utilizing the difference in electrodeposition overpotentials between carbon and Pd NP surfaces. X-ray photoelectron spectroscopy revealed a charge transfer from Ni NPs to Pd NPs, implying that the catalytic and optical properties can be expected to be controllable. The formed heterodimer array structure was mechanically stable against ultrasonication in ethanol for over 1 h because most parts of the Pd NPs were tightly embedded in the carbon film. After conversion from Ni to nickel hydroxide (Ni(OH)2), the electrode showed high electrocatalytic activity toward glucose oxidation, with a higher turnover rate and lower overpotential compared to Ni(OH)2 electrodeposited on pure carbon film electrodes.

Hole, Convex, and Silver Nanoparticle Patterning on Polystyrene Nanosheets by Colloidal Photolithography at Air-Water Interfaces.

Colloidal photolithography is a versatile advanced technique for fabricating periodic nanopatterned arrays, with patterns carved exclusively on photoresist films deposited on solid substrates in a typical photolithographic process. In this study, we apply colloidal photolithography to polystyrene (PS) films half-covered with poly(methyl methacrylate) (PMMA) colloids at the air–water interface and demonstrate that periodic hole structures can be carved in PS films by two processes: photodecomposing PS films with ultraviolet (UV) light and removing PMMA colloids with a fluorinated solvent. Nonspherical holes, such as C-shaped and chiral comma-shaped holes, are also fabricated by regulating the UV illumination conditions. Furthermore, in addition to holes, convex patterns on PS films are realized by combining weak UV illumination with solvent treatment. We also demonstrate that actively using the water surface as the UV illumination field enables periodic silver nanoparticle spots to be deposited on PS films simply by dissolving silver ions in the water phase.

Investigation of Solvent-Assisted In-Mold Bonding of Cyclic Olefin Copolymer (COC) Microfluidic Chips.

The bonding of microfluidic chips is an essential process to enclose microchannels or microchambers in a lab-on-a-chip. In order to improve the bonding quality while reducing the fabrication time, a solvent-assisted bonding strategy was proposed to seal the microchannels immediately after the cover sheet and substrate chip was injection molded in a single mold. Proper organic solvents were selected and the influences of solvent ratios on the surface roughness, microchannel morphology, and contact angle of microfluidic chips were investigated. When the solvent bonding was integrated in the mold, the influences of solvent volume fraction, solvent dosage, bonding pressure, and bonding time on the bonding quality were analyzed. Results show that the solvent cyclohexane needs to be mixed with isopropanol to reduce the dissolution effect. Solvent treatment is suggested to be performed on the cover sheet with a cyclohexane volume fraction of 70% and a dose of 1.5 mL, a bonding pressure of 2 MPa, and a bonding time of 240 s. The bonding strength reaches 913 kPa with the optimized parameters, while the microchannel deformation was controlled below 8%.

Current Status of Quantum Chemical Studies of Cyclodextrin Host-Guest Complexes.

This article aims to review the application of various quantum chemical methods (semi-empirical, density functional theory (DFT), second order Møller–Plesset perturbation theory (MP2)) in the studies of cyclodextrin host–guest complexes. The details of applied approaches such as functionals, basis sets, dispersion corrections or solvent treatment methods are analyzed, pointing to the best possible options for such theoretical studies. Apart from reviewing the ways that the computations are usually performed, the reasons for such studies are presented and discussed. The successful applications of theoretical calculations are not limited to the determination of stable conformations but also include the prediction of thermodynamic properties as well as UV–Vis, IR, and NMR spectra. It has been shown that quantum chemical calculations, when applied to the studies of CD complexes, can provide results unobtainable by any other methods, both experimental and computational.

Biomimetic Peptide Catalytic Bond-Forming Utilizing a Mild Brønsted Acid.

Since the global peptide drug market demand has been predicted to increase, highly efficient and inexpensive mass scale peptides are required. However, the production process raises questions about the cost of energy input, scale-up production, raw materials, and solvents treatment. This paper introduces 2 methods for the 2-4 mer oligopeptides bond formation for batch reaction utilizing 50-100 mol% of a mild Brønsted acid under the mild condition. One of the methods has been capably adapted to flow synthesis at room temperature using organic solvents with boiling points below 100 °C. The method applies the tert-butoxycarbonyl amino methoxy group, forming the desired dipeptide without solvent at mild temperatures. Furthermore, the conversion of the carboxylic acid leaving the group to phenyl ester promotes peptide bond formation, and the reaction were applied to di, tri, and tetrapeptide bond formation in excellent yield without notable racemization at ambient temperature (up to >99 % yield and 99 : 1 dr). Finally, this study proposes this new production method to overcome the limited scale-up production by reaction device scale: liquid phase biomimetic catalytic peptide flow synthesis utilizing a mild Brønsted acid.

Comparison of Electrochemical Polishing Treatments between Phosphoric Acid and a Deep Eutectic Solvent for High-Purity Copper

This study investigated and compared the acid-free electropolishing of copper with the state-of-the-art acidic electropolishing process. The acid-free medium used in this study is based on a deep eutectic solvent comprised of 2:1 ethylene glycol and choline chloride. The electrochemical study included voltammetry and chronoamperometry tests during the electropolishing process. The characterization techniques used were atomic force microscopy (AFM) and digital microscopy, and surface morphology comparisons summarized the electropolishing efficiency of phosphoric acid and acid-free deep eutectic solvent treatments for high-purity copper. Electropolishing copper with a deep eutectic solvent resulted in a mirror finish and a post-treatment surface that was 8× smoother than the original metal surface prior to electropolishing treatments with a smoothing efficiency of 91.1 ± 1.5%. This eco-friendly solution produced polished surfaces superior to those surfaces treated with industry standard acid electrochemistry treatments of 1 M H3PO4.

Construction of solvent-resistant interphase of CF/PEEK composites via introducing water-based crosslinkable polyaryl ether sizing agent

Carbon fiber (CF) reinforced polyether ether ketone (PEEK) occupied an important position in composites due to its excellent properties. However, the weak interfacial strength became a bottleneck restricting the further development. In this work, water-based crosslinkable polyarylether sizing agent with different concentrations were prepared. These sizing agents have good storage stability, with particle sizes ranging from 54.6 nm to 78.5 nm. The chemical bonds formed by self-crosslinking reaction of nitrile groups during the hot-pressing process endowed the sizing agent with outstanding solvent resistance. In addition, the glass transition temperature of the crosslinked sizing agent was increased to 285.5 °C. The maximum bending strength and interlaminar shear strength of CF1.5/PEEK composites were 43.1% and 42.7% higher than unsized CF composites. Furthermore, it retained excellent mechanical properties after solvent treatment, owing to the construction of the solvent-resistant interphase. This “thermoplastic processing, thermosetting application” polyarylether sizing agent is expected to further expand the application range of CF/PEEK composites.

Degumming of hemp fibers using combined microwave energy and deep eutectic solvent treatment

Hemp bast fibers were degummed using combined microwave energy (MWE) and deep eutectic solvent (DES) to generate pure hemp cellulose fibers for potential textile applications. The properties of the degummed fibers were investigated and compared with those of the alkali-treated fibers using several analytical techniques. Results revealed that hemp fiber surface underwent dramatic structural disruption during the pretreatment, due to the removal of “gummy” compounds (i.e., pectin, oil, wax, etc.), lignin, and amorphous cellulose. The treated fibers had much enhanced thermal stability due to the removal of the gummy materials. The reduced enthalpy (171.34 J/g) of MWE-DES treated fibers at 1:20 fiber-DES ratio as compared to that of raw hemp fibers (272.09 J/g) also confirmed the higher thermal stability of MWE-DES treated fibers. Chemical composition analysis showed that the holocellulose content in the treated fiber samples at 1:20 fiber-DES ratio increased to 98.63% which was comparable with the holocellulose content (98.87%) of the alkali-treated fibers. The Ultraviolet (UV) protection factor (UPF) of MWE-DES treated fibers at 1:10 and 1:20 fiber-DES ratio was, respectively, 118.11 and 114.19, meeting the requirement of UV resistant textile fibers. The study demonstrates a potentially effective, less time-consuming, and environmentally sustainable protocol for manufacturing purified hemp cellulose fibers using combined MWE-DES treatment.

Preliminary Characterization of Structural and Rheological Behavior of the Quinoa Hyperprotein-Defatted Flour

Protein functional properties are related to physical and chemical parameters that influence protein behavior in food systems during processing, storage and consumption. The structural and rheological properties of three quinoa hyperprotein flours (without defatting, WD, chemically defatted, CD, and mechanically defatted, MD) were evaluated. The values of the fluidity index (n) were significantly different (p < 0.05), which was associated with changes in protein or starch structures due to solvent treatments or heating of the flour during pressing. In addition, a strong dependence of the consistency index (k) on the shear rate was observed. For dispersions with a concentration of 12% (w/v), CD and WD had a significantly lower setback value than MD. The viscosity peak was affected by the presence of lipid molecules. Greater changes were evident in the β-sheet (1,610 and 1,625 cm−1) and β-spin (1,685 and 1,695 cm−1) structures. The changes identified in these structures were associated with the defatting treatment. Consequently, the intensity ratio 2,920/1,633 cm−1 was more sensitive to changes in the fat content of the flours. It was shown that defatting conditions increase the protein adsorption kinetics and that the viscoelastic properties of the protein increase when the flour has a lower fat content. Hyperprotein quinoa flour could be used to improve the protein content of products such as snacks, pastas, ice cream, bakery products, meat extenders, among others, due to its foaming, gelling or emulsifying capacity. The objective of this work was to study the effect of two types of defatting of hyperprotein quinoa flour on its structural and rheological properties.

Lignin-containing cellulose nanofibers made with microwave-aid green solvent treatment for magnetic fluid stabilization

Lignin-containing cellulose nanofibers (LCNFs), prepared from energy cane bagasse (ECB) using microwave-assisted natural deep eutectic solvent (MW-NADES) pretreatment combined with microfluidization, are utilized as stabilizing agents for magnetic particles (MNPs) in magnetorheological fluids (MRFs). The as-prepared LCNFs helped suspend negatively charged MNPs in MRFs effectively due to the presence of physically entangled network of LCNFs and the electrostatic repulsion between LCNFs and MNPs. Consequently, the presence of LCNFs increased the viscosity, yield stress and dynamic moduli of MRFs within the entire magnetic field range (0–1 T). Moreover, the as-developed LCNF-MRFs exhibited superior magnetorheological properties, i.e., widely controllable viscosity, yield stress and dynamic moduli, rapid magnetic response, good reversibility and outstanding cycling stability. This work demonstrates the sustainable, ultrafast production of LCNFs from cellulosic biomass using MW-NADES for MRF stabilization, paving the way for the development of high-performance, and eco-friendly MRFs.

Asymmetric charge carrier transfer and transport in planar lead halide perovskite solar cells

Understanding charge carrier extraction from the perovskite photoactive layer is critical to optimizing the design of perovskite solar cells. Herein, we demonstrate a simple time-resolved photoluminescence method to characterize the kinetics of charge transport across the bulk perovskite and charge transfer from the perovskite layer to the interlayers, elucidating the dependence of these dynamics on film thickness, grain boundaries (GBs), and interlayers. Using asymmetric laser excitation, we selectively probe charge transport by generating charges both close to and far from the heterojunction interface and correlate these results with device performance. We observe that both film thickness and GBs affect the asymmetry between electron and hole charge transport across the bulk perovskite and charge transfer from the bulk perovskite to the respective interlayers. • Time-resolved photoluminescence with spatially localized excitation • Asymmetries of charge carrier transfer and transport are quantified • Lateral grain boundaries result in unbalanced charge transport • Aerosol-assisted solvent treatment removes lateral grain boundaries effectively Xu et al. demonstrate a simple time-resolved photoluminescence method to selectively probe charge transfer and charge transport in perovskite films with interlayers. The results show both film thickness and grain boundaries affect the asymmetry between electron and hole charge transfer and charge transport.

Use of Camelina sativa and By-Products in Diets for Dairy Cows: A Review.

Simple SummaryCamelina sativa, also known as false flax, is an oilseed adaptable to wide agronomic conditions and is an environment-friendly crop utilized by human beings for decades. Camelina seed and its derivatives have a nutritional value comparable to other products fed to dairy cows. However, similar to other oil crops, it has anti-nutritional factors which have brought some regulations from authorities on the inclusion levels of camelina seed and oil-extracted products. Many studies have been conducted, and effects on feed intake, digestion, and metabolism are controversial at higher inclusion levels, Yet, there has still been no effect noticed on the metabolic hormones of dairy cows when included at an appropriate level (2 kg/animal/day seeds or 10% inclusion on a dry matter basis of oil extracted products). Although inclusion of the seed and expeller on milk fat suppression is prominent, milk fat produced by a diet including camelina seed and its by-products is rich in health-beneficial fatty acids. In addition, with processing, its anti-nutritional factors can be reduced, and solvent-extracted meals can be used in higher inclusions than current recommended levels, without affecting the digestion and metabolism of the animal.Camelina sativa, belonging to the Brassicaceae family, has been grown since 4000 B.C. as an oilseed crop that is more drought- and cold-resistant. Increased demand for its oil, meal, and other derivatives has increased researchers’ interest in this crop. Its anti-nutritional factors can be reduced by solvent, enzyme and heat treatments, and genetic engineering. Inclusion of camelina by-products increases branched-chain volatile fatty acids, decreases neutral detergent fiber digestibility, has no effect on acid detergent fiber digestibility, and lowers acetate levels in dairy cows. Feeding camelina meal reduces ruminal methane, an environmental benefit of using camelina by-products in ruminant diets. The addition of camelina to dairy cow diets decreases ruminal cellulolytic bacteria and bio-hydrogenation. This reduced bio-hydrogenation results in an increase in desirable fatty acids and a decrease in saturated fatty acids in milk obtained from cows fed diets with camelina seeds or its by-products. Studies suggest that by-products of C. sativa can be used safely in dairy cows at appropriate inclusion levels. However, suppression in fat milk percentage and an increase in trans fatty acid isomers should be considered when increasing the inclusion rate of camelina by-products, due to health concerns.

Scalable and Heavy Foam Functionalization by Electrode‐Inspired Sticky Jammed Fluids for Efficient Indoor Air‐Quality Management

Functionalization of polymer foams by surface coating is of great interest for advanced flow‐interactive materials working with well‐controlled 3D open channels. However, realizing heavy functional coating via a fast and recyclable way remains a big challenge. Here, inspired by the battery electrodes, we propose a scalable mechanic‐assisted heavy coating strategy based on the design of sticky jammed fluid (SJF) to conquer the above challenge. Similar to the electrode slurry, the SJF is dominated by a high concentration of active material (≥20 wt% of active carbon, for instance) uniformly dispersed in a protein binder solution. Due to the sticky and solid‐rich nature of the SJF, one can realize a high coating efficiency of 60 wt% gain per coating. The critical factors controlling the coating processing and quality are further identified and discussed. Furthermore, the functionalized foam is demonstrated as a high‐performance shape‐customizable toxic gas remover, which can absorb formaldehyde very efficiently at different circumstances, including static adsorption, flow‐based filtration, and source interception. Finally, the foam skeleton and the active materials are easily recycled by a facile solvent treatment. This study may inspire new scalable way for fast, heavy, and customizable functionalization of polymeric foams.

A route towards metal-free electrical cables via carbon nanotube wires

Carbon nanotubes (CNTs) have unique properties with promise to outperform the electrical characteristics of bulk copper, giving rise to its primary driver for use in electronic devices. The challenge still hindering their full exploitation stems from an inability to manufacture them to long lengths, resulting in a requirement to align and entwine them into a yarn or wire. There have been several methods presented in achieving this, however, the common disadvantage has been that they are only applicable to specific types and morphologies of CNTs. In the work reported here, using electrospinning as a universally applicable route for any CNT type, we re-engineer and optimise the various formulation, fabrication and processing steps required to manufacture CNT wires. Through a series of investigations using a materials agnostic approach, we experimentally probe the choice of solvent, surfactant and thermal treatment temperature of the CNT inks, demonstrating the CNT-type optimum using a range of commercially available single- double- and multiwalled CNTs. Finally, this allowed us to develop and probe an electrical conditioning process to further enhance the electrical performance, achieving the highest reported un-doped electrical conductivity of 36,000 S⋅ m − 1 for electrospun CNT wires, or a specific conductivity of 0.2 × 10 6 S · m − 1 / g · c m − 3 .