Solvent Soaking Research Articles

“Like dissolves like” enables the synergy of fluorinated additive and fluorous solvent soaking for high-performance organic solar cells

The pre-treatment and post-treatment of organic solar cells (OSCs) are two important device engineering processes that are closely associated with photovoltaic performance. Yet these two stages are independently developed to optimize the morphology and then improve the device performance, while their synergy is believed to be more productive. In this study, the fluorinated additive and fluorous solvent soaking (FSS) are simultaneously employed in OSCs, and the “like dissolves like” concept drives their synergetic role on the morphology optimization. The fluorinated additive 1,8-diiodoperfluorooctane (FDIO) could selectively enhance the packing order and crystallinity of the acceptor through forming the fluorine-induced interactions. Moreover, fluorous solvent could penetrate into the blend film and then remove the residue FDIO while further optimizing the morphology by enhancing molecular packing. By employing the synergy of FDIO additive and FSS treatment (40 °C for 30 s), a champion power conversion efficiency (PCE) of 18.64 % with the simultaneous improvements of photovoltaic parameters is achieved. This study provides a synergetic strategy by employing fluorinated additive and fluorous solvent to tune film morphology in the film-formation and post-treatment processes, respectively, consequently advancing the photovoltaic performance of OSCs.

Synthesis of Carboxyl-Functionalized COFs with Alternate Stable β-Ketoenamine and Benzimidazole Linkages: Unraveling Exceptional Solvent Effects for Efficient Uranium Separation.

The prevalent π-π interactions in 2D covalent organic frameworks (COFs) impart a certain flexibility to the structures, making the stacking of COF layers susceptible to external stimuli and introducing some structural disorder. Recent research indicates that the flexibility between COF layers and the associated disorder significantly influence their selective adsorption performance toward gas molecules. However, the adsorption process in a solution environment is more complex compared to gas-phase adsorption, involving interactions between adsorbents and adsorbates, as well as the solvation effects of flexible 2D COFs. Therefore, the inherent flexibility and disorder in 2D COFs under solution conditions and their impact on the adsorption performance of metal ions have not been observed yet. Herein, the synthesis of a novel carboxyl-functionalized COF featuring stable β-ketoenamine and benzimidazole linkages, named DMTP-COOH, is presented. DMTP-COOH exhibits excellent selective adsorption capability for uranium, with significantly different adsorption capacities observed after treatment with different solvents. This notable difference in adsorption capacity is observed under varying pH, concentration, time, and even in the presence of multiple competing ions. This work represents the first observation of the significant impact of solvent soaking treatment on the selective adsorption performance of COFs for uranium under liquid conditions.

Comparison of Electronic Resistance Measurement Methods and Influencing Parameters for LMFP and High-Nickel NCM Cathodes

The automotive industry aims for the highest possible driving range (highest energy density) in combination with a fast charge ability (highest power density) of electric vehicles. With both targets being intrinsically contradictory, it is important to understand and optimize resistances within lithium-ion battery (LIB) electrodes. In this study, the properties and magnitude of electronic resistance contributions in LiMn0.7Fe0.3PO4 (LMFP)- and LiNixCoyMnzO2 (NCM, x = 0.88~0.90, x + y + z = 1)-based electrodes are comprehensively investigated through the use of different measurement methods. Contact resistance properties are characterized via electrochemical impedance spectroscopy (EIS) on the example of LMFP cathodes. The EIS results are compared to a two-point probe as well as to the results obtained using a novel commercial 46-point probe system. The magnitude and ratio of contact resistance and compound electronic resistance for LMFP- and NCM-based cathodes are discussed on the basis of the 46-point probe measurement results. The results show that the 46-point probe yields significantly lower resistance values than those in EIS studies. Further results show that electronic resistance values in cathodes can vary over several orders of magnitude. Various influence parameters such as electrode porosity, type of current collector and the impact of solvent soaking on electronic resistance are investigated.

Enabling Highly Robust Full‐Color Ultralong Room‐Temperature Phosphorescence and Stable White Organic Afterglow from Polycyclic Aromatic Hydrocarbons

AbstractIn this work, full‐color and stable white organic afterglow materials with outstanding water, organic solvents, and temperature resistances have been developed for the first time by embedding the selected polycyclic aromatic hydrocarbons into melamine‐formaldehyde polymer via solution polymerization. The afterglow quantum yields and lifetimes of the resulting polymer films were up to 22.7 % and 4.83 s, respectively, under ambient conditions. For the coronene‐doped sample, its afterglow color could be linearly tuned between yellow and blue by adjusting the temperature, and it could still emit an intense blue afterglow with a lifetime of 0.68 s at 440 K. Moreover, the films showed a bright and stable white afterglow at 370 K with a lifetime of 2.80 s and maintained an excellent afterglow performance after soaking in water and organic solvents for more than 150 days. In addition, the application potential of the polymer films in information encryption and anti‐counterfeiting was also demonstrated.

Enabling Highly Robust Full-Color Ultralong Room-Temperature Phosphorescence and Stable White Organic Afterglow from Polycyclic Aromatic Hydrocarbons.

In this work, full-color and stable white organic afterglow materials with outstanding water, organic solvents, and temperature resistances have been developed for the first time by embedding the selected polycyclic aromatic hydrocarbons into melamine-formaldehyde polymer via solution polymerization. The afterglow quantum yields and lifetimes of the resulting polymer films were up to 22.7 % and 4.83 s, respectively, under ambient conditions. For the coronene-doped sample, its afterglow color could be linearly tuned between yellow and blue by adjusting the temperature, and it could still emit an intense blue afterglow with a lifetime of 0.68 s at 440 K. Moreover, the films showed a bright and stable white afterglow at 370 K with a lifetime of 2.80 s and maintained an excellent afterglow performance after soaking in water and organic solvents for more than 150 days. In addition, the application potential of the polymer films in information encryption and anti-counterfeiting was also demonstrated.

Efficient organic solar cells enabled by sustainable and synergetic device engineering

In order to accelerate the transfer of organic solar cells (OSCs) from lab to fab, this work develops a synergetic strategy by integrating low-cost material, green solvent, bio-based additive and low-temperature post-treatment to sustainably fabricate OSCs. The donor polymer PTQ10 composing of simple building blocks, accompanied by the acceptor L8-BO, is dissolved in the green solvent tetrahydrofuran, wherein a bio-based cinnamonitrile is firstly used as solvent additive. Moreover, fluorous solvent soaking (FSS) is employed as post-treatment to replace the high-temperature and time-consuming thermal annealing. Systematic investigations are performed to unravel the mechanism of the device engineering developed in this work. Differing from the one-way movement of additive, the fluorous solvent can penetrate into and come out the film in cycles. Meanwhile, some L8-BO is selectively dissolved and brought out by the fluorous solvent, so this partial L8-BO bears the function as solid additive to optimize the morphology. As a result, the device achieves a remarkable power conversion efficiency of 17.11%, among the best efficiencies of OSCs prepared by non-halogenated non-aromatic solvents. In addition, the excellent universality ensures this strategy is also effective in the thick-film OSCs.

Achieving efficient flexible and large-area organic solar cells via additive-assisted fluorous solvent soaking

Developing flexible and large-area organic solar cells (OSCs) is of vital importance for advancing the commercialization. However, using solvent additives during the film deposition is tricky and unpredictable for the large-area device. Furthermore, typical post-treatments like high-temperature thermal annealing might cause the undesired deformation of the flexible substrate, thus adversely affecting the photovoltaic performance. Herein, a new device engineering namely additive-assisted fluorous solvent soaking (AFSS), is developed as an alternative approach for OSCs fabrication. No solvent additive is used in the active layer deposition, providing more uniform films in large-area processing. The fresh-made film is subsequently soaked in a mixture of fluorous solvent and a tiny amount of solvent additive, wherein the cyclic movement of the fluorous solvent associated with the additive could facilitate the molecular reorganization at relatively low temperature (40 °C), and thus optimizing the morphology of the active layer. Compared with the traditional method, AFSS is more effective in various OSCs including the rigid or flexible substrates and the conventional or inverted device architectures. An ultra-flexible and large-area device fabricated by AFSS realizes a PCE of 12.63%. This work provides a robust and practical strategy to fabricate OSCs as well as other optoelectronic devices at low temperature.

Preparation and Properties of Polysaccharide‐Based Epoxy Vitrimers

AbstractTraditional chemically cross‐linked polymer materials may cause severe environmental pollution and economic losses due to the difficulty of recycling. Vitrimers containing reversible dynamic covalent bonds are processable, recyclable, and self‐healing. In this article, a bio‐based epoxy resin curing agent is synthesized by hydrolysis using cellulose as raw material. The results show that the epoxy vitrimers with the best ratio have a lower topological transition temperature and a fast relaxation time at 140 °C. After soaking in solvent for 90 days, the gel content of the material is greater than 81%. The glass transition temperature of the sample measured by differential scanning calorimetry （DSC) is 83 °C. It also has a high initial decomposition temperature (350 °C) with good flexibility and solvent resistance, showing its good performance as a coating paint.

Controlled Swelling of Monolithic Films as a Facile Approach to the Synthesis of UHMWPE Membranes

A new method of fabricating porous membranes based on ultra-high molecular weight polyethylene (UHMWPE) by controlled swelling of the dense film was proposed and successfully utilized. The principle of this method is based on the swelling of non-porous UHMWPE film in organic solvent at elevated temperatures, followed by its cooling and further extraction of organic solvent, resulting in the formation of the porous membrane. In this work, we used commercial UHMWPE film (thickness 155 μm) and o-xylene as a solvent. Either homogeneous mixtures of the polymer melt and solvent or thermoreversible gels with crystallites acting as crosslinks of the inter-macromolecular network (swollen semicrystalline polymer) can be obtained at different soaking times. It was shown that the porous structure and filtration performance of the membranes depended on the swelling degree of the polymer, which can be controlled by the time of polymer soaking in organic solvent at elevated temperature (106 °C was found to be the optimal temperature for UHMWPE). In the case of homogeneous mixtures, the resulting membranes possessed both large and small pores. They were characterized by quite high porosity (45-65% vol.), liquid permeance of 46-134 L m-2 h-1 bar-1, a mean flow pore size of 30-75 nm, and a very high crystallinity degree of 86-89% at a decent tensile strength of 3-9 MPa. For these membranes, rejection of blue dextran dye with a molecular weight of 70 kg/mol was 22-76%. In the case of thermoreversible gels, the resulting membranes had only small pores located in the interlamellar spaces. They were characterized by a lower crystallinity degree of 70-74%, a moderate porosity of 12-28%, liquid permeability of up to 12-26 L m-2 h-1 bar-1, a mean flow pore size of up to 12-17 nm, and a higher tensile strength of 11-20 MPa. These membranes demonstrated blue dextran retention of nearly 100%.

Aggregation induced emission and mechanofluorochromism of tetraphenylethene fused thiazolo[5,4‑d]thiazole derivatives

We designed and prepared novel MFC materials (TPE-B, TPE-T) with D-π-A scaffolds containing thiazolo[5,4-d]thiazole and TPE units. The results proved that TPE-B and TPE-T exhibited obvious AIE properties and reversible MFC behavior. The performance in solid state of TPE-B and TPE-T presented that the mechanical force led to 25–28 nm red-shift, and could recover to the original state by solvent soaking. The powder XRD reveal that the morphological change from crystalline to amorphous state could be responsible for mechanochromism. Moreover, TPE-B and TPE-T could be constructed the rewritable information storage systems. This research work provides valuable reference for the design of MCF materials.

Probing the origin and stability of bivalency in copper based porous coordination network and its application for H2S gas capture

A bivalent Cu(I,II) metal–organic framework (MOF) based on the 4,4′,4″-s-Triazine-2,4,6-triyl-tribenzoate linker was synthesized via a solvothermal method. The MOF possessed 43.8% of the Cu sites as Cu+ with a surface area of 1257 m2 g−1. The detailed spectroscopic analysis confirmed dimethylformamide (DMF) solvent as the reductant responsible for Cu+ sites in the synthesized MOF. The Cu+ sites were easily accessible and prone to oxidation in hot water or acidic gas environment. The MOF showed water-induced structural change, which could be partially recovered after soaking in DMF solvent. The synthesized MOF showed a high hydrogen sulfide (H2S) uptake capacity of 4.3 mmol g–1 at 298 K and an extremely low H2S pressure of 0.0005 bar. The adsorption capacity was the highest among Cu-based MOFs with PCN-6-M being regenerable, which made it useful for deep desulfurization applications. The adsorbed H2S was mineralized to sulfide, sulfur, and sulfates, mediated by the Cu+/Cu2+ redox cycle in the presence of adsorbed water and molecular oxygen. Thus, the study confirmed that DMF as a reductant is responsible for the origin of bivalency in PCN-6-M and possibly in other Cu-based MOFs reported in the literature. Also, the developed MOF could be a potential candidate for flue gas desulfurization and gas purification applications.

The role of solvent soaking and pretreatment temperature in microwave-assisted pyrolysis of waste tea powder: Analysis of products, synergy, pyrolysis index, and reaction mechanism

This study focuses on microwave-assisted pyrolysis (MAP) of fresh waste tea powder and torrefied waste tea powder as feedstocks. Solvents including benzene, acetone, and ethanol were used for soaking feedstocks. The feedstock torrefaction temperature (at 150 °C) and solvents soaking enhanced the yields of char (44.2–59.8 wt%) and the oil (39.8–45.3 wt%) in MAP. Co-pyrolysis synergy induced an increase in the yield of gaseous products (4.7–20.1 wt%). The average heating rate varied in the range of 5–25 °C/min. The energy consumption in MAP of torrefied feedstock (1386 KJ) significantly decreased compared to fresh (3114 KJ). The pyrolysis index dramatically varied with the solvent soaking in the following order: ethanol (26.7) > benzene (25.6) > no solvent (10) > acetone (6). It shows that solvent soaking plays an important role in the pyrolysis process. The obtained bio-oil was composed of mono-aromatics, poly-aromatics, and oxygenated compounds.

Liquid‐Free, Anti‐Freezing, Solvent‐Resistant, Cellulose‐Derived Ionic Conductive Elastomer for Stretchable Wearable Electronics and Triboelectric Nanogenerators

AbstractThe development of flexible conductive elastomers integrating renewable feedstock, splendid mechanical property, and excellent weather resistance is of major interest and challenge. Here, a novel strategy is reported to construct the liquid‐free cellulose‐derived ionic conductive elastomer that is successfully applied in the wearable sensor and triboelectric nanogenerators (TENG). In this strategy, the ionic conductive elastomer with physical and chemical dual‐crosslinking network is prepared via in situ polymerization of the polymerizable deep eutectic solvent. The construction of dual‐crosslinking network improves the mechanical strength and toughness more than 2 times, and the cellulose contributes to forming the dense hydrogen bond crosslinking network that can improve the recyclability, anti‐freezing, and solvent‐resistance performance. Benefiting from these features, the ionic conductive elastomer is successfully applied in the wearable sensors and TENG for monitoring human motion, and in harvesting mechanical energy to convert into stable electrical outputs to light the LEDs, charge the capacitor, and power the electronic watch. The ionic conductive elastomer maintains reliable sensing and energy harvesting performance even after recycling, soaking in organic solvent, or at low/high temperature. This study paves a promising strategy for fabricating sustainable and multifunction flexible electronics that are suitable for harsh environments.

A robust and transparent hydrogel coating for sustainable antifogging with excellent self-cleaning and self-healing ability

Films with antifogging properties can be used in a wide range of fields, from manufacturing to agriculture, such as screens, camera lenses, and greenhouse films. In this study, a scraping technique was utilized to coat antifogging films on polyethylene substrate by using a solution containing polyvinyl alcohol, sodium alginate, and glycerin with suspended titanium dioxide nanoparticles. The resulting hydrophilic coating has outstanding antifogging, self-healing, and anti-fouling qualities due to the polymer’s great hydration capacity. The coating also held up well during prolonged heat and ultraviolet exposure (40 °C for 17 days and 192 h of 1.27 mW/cm2 UV radiation). Furthermore, when exposed to 30 g sands impact from a height of 10 to 40 cm, 18 days outdoors and 1 h soaking in polar and non-polar solvents (absolute ethanol, isopropanol, n-hexane and n-hexadecane), the hydrophilicity and antifogging performance were well sustained. Different flexible/rigid substrates, such as PET, PC, PVC, and others, can be successfully coated with antifogging film by using such simple construction approach.

Self‐Lubricative Organic–Inorganic Hybrid Coating with Anti‐Icing and Anti‐Waxing Performances by Grafting Liquid‐Like Polydimethylsiloxane

AbstractPolydimethylsiloxane (PDMS) is one of the most popular materials to protect infrastructures from the complicated environment due to its chemical stability, nontoxicity, low cost, high durability, and chain flexibility. Herein, a series of organic–inorganic hybrid coatings are prepared by simply grafting loop‐like PDMS on a solid surface. Owning to the low surface energy and high mobility of PDMS chains, the special characteristics, including liquid repellency, anti‐fouling, self‐lubrication, anti‐ and delay‐ice, anti‐paraffin, etc., are presented. To confirm the liquid‐like slippery nature of PDMS surface, the controlled de‐icing and de‐waxing tests on rigid chain surfaces are conducted. The liquid‐like nature of PDMS allows ice or paraffin to have a low adhesion in a slip state, but a fractured state on alkylated and perfluorinated surface with a high adhesion strength. In addition, the flexible PDMS chains grafted on the inorganic silica layer by stable covalent bond endow the surface with excellent durability, including maintaining low ice adhesion during 50 icing‐deicing cycles, resistance to UV irradiation, washing or soaking in organic solvent, etc. This work provides a simple approach for constructing self‐lubricative low surface energy coating to realize de‐ice and de‐wax easily, which may have a broad prospect of application in equipment protection.

Assessment of the efficiency of different chemical treatments and ultrasonic cleaning for defatting of cancellous bone samples

Our study aimed to asses the defatting efficiency of different methods, which are commonly used and easily available in the laboratory in order to find a method that is effective, convenient, safe, and economical. Cylindrical cancellous bone specimens were obtained from fresh-frozen human cadaver femoral condyles, cut into multiple small specimens (Ø8 × 2 mm), and assigned to two groups that were treated with either chemical solvent soaking (Solvent group) or ultrasonic cleaning (Ultrasound group). Each group was divided into several subgroups based on different treatments. Digital photographs were taken of each specimen. The difference of material density (Δρb), apparent density (Δρapp), and porosity (ΔP) before and after treatment were used as evaluation indicators. For the solvent group, in Δρb, only the combination of 99% ethanol and detergent solution showed a significant difference before and after treatment (P = 0.00). There was no significant difference in ΔP among acetone, the mixture of 99% ethanol and acetone, and the combination of 99% ethanol and detergent solution (P = 0.93). For the ultrasound group, the median of all subgroups in Δρapp and ΔP were all lower than the solvent group. The combination of 99% ethanol and detergent solution (v/v = 1:20), as well as the mixture of 99% ethanol and acetone (v/v = 1:1), seem to be the optimal defatting methods for 2 mm thick cancellous bone slices due to their effectiveness, availability, low-cost and safety. Chemical soaking for 24 h is more effective than ultrasonic cleaning with 99% ethanol or acetone for 20 or 40 min.

Flexible and Robust Three-Dimensional Covalent Organic Framework Membranes for Precise Separations under Extreme Conditions.

Membranes based on covalent organic frameworks (COFs) have demonstrated huge potential to resolve the long-standing bottlenecks in separation fields due to their structural and functional attributes. Herein, a three-dimensional COF featuring interpenetrated apertures, 3D-OH-COF, is rationally synthesized on polyimide supports to generate flexible, robust membranes. The resultant 3D-OH-COF presents excellent crystallinity, prominent porosity, and exceptional solvent resistance, enabling the produced membrane a sharp and durable selectivity to small molecules in water and organic solvents. Impressively, the membrane also exhibits excellent flexibility and robustness as verified by the well-maintained performances after serious bending and solvent soaking under elevated temperatures. We further chemically convert 3D-OH-COF into the carboxyl-decorated 3D-COOH-COF by a postsynthetic strategy. The 3D-COOH-COF retains high crystallinity, and the converted membrane receives a remarkable capture ability for targeted multivalent ions over other competing ions. This study exploits a viable avenue to produce practical 3D COF membranes toward ultimate separations under extreme conditions.

Enhanced enzymatic saccharification of sorghum straw by effective delignification via combined pretreatment with alkali extraction and deep eutectic solvent soaking

Hydrogen bond donor (HBD) in ChCl-based deep eutectic solvent (DESs) had significant influence on the Sorghum straw (SS) pretreatment. Lactic acid (LAC) was chosen as the appropriate HBD for preparing ChCl-based DES to pretreat Sorghum straw (SS). Furthermore, sequential pretreatment with dilute sodium hydroxide (0.75 wt%) for 1 h at 121 °C and ChCl:LAC soaking at 140 °C for 40 min was applied to pretreat SS for removing lignin (78.4%) and xylan (67.6%). Hydrolysis for 72 h, the reducing sugar yield reached 94.9%. Moreover, relationships of delignification and xylan removal with saccharification were explored after pretreatment. Finally, the fermentability of SS-hydrolysates was verified by bioethanol fermentation by S. cerevissiae with the yield of 0.45 g ethanol/g glucose. No significant inhibition was observed on ethanol fermentation. Obviously, establishment of high-efficient combination pretreatment with alkali extraction and ChCl:LAC soaking was successfully demonstrated for enhancing enzymatic saccharification of SS.

Highly Stretchable, Strain‐Sensitive, and Antifreezing Macromolecular Microsphere Composite Starch‐Based Hydrogel

AbstractStarch‐based hydrogel is widely used as an excellent biocompatibility and biodegradability material. However, due to the disadvantages of poor mechanical properties, brittleness, and low stretchability attribute that remains a challenge to prepare multifunctional starch hydrogel integrating high stretchability, strength, and conducting capacity. In this study, macromolecular microspheres with various wettability are successfully incorporated into the hydrogel prepared using the carboxymethyl starch and polyacrylamide cross‐linked by Fe3+ and covalent cross‐linker, respectively. The obtained double‐network (DN) hydrogel performs good mechanical properties (the fracture stress 483 ± 38 kPa and the elongation at break 1615 ± 25%). Impressively, the obtained DN hydrogels by solvent soaking still maintain excellent mechanical strength and flexibility at −40 °C. Furthermore, it can be assembled to be a resistance‐type strain sensor to detect multiscale strain. Therefore, the strategy can shed light on the preparation of multifunctional starch‐based hydrogel for broad applications.

Effect of high pressure processing on migration characteristics of polypropylene used in food contact materials

ABSTRACT The migration of small molecular mass organic compounds from polypropylene (PP) copolymer films into food simulants during and after high pressure processing (HPP) was studied. An overlapping temperature profile was developed to isolate the pressure effect of HPP (700 MPa, 71°C, 5 min) from equivalent thermal processing (TP) at atmospheric pressure (0.1 MPa). Chloroform, toluene, methyl salicylate, and phenylcyclohexane were chosen as surrogate compounds, and were spiked into test polymer films at concentrations of 762–1152 mg kg–1 by a solvent soaking technique. Migration (w/w) of surrogate compounds from loaded PP films into Miglyol 812 (a medium-chain triglyceride mixture) and 10% ethanol was quantified by headspace GC/MS during HPP and TP, and subsequent storage at 25°C for up to 10 days. HPP significantly delayed migration of the surrogates from PP into both food simulants relative to TP. The average migrations into Miglyol after TP and HPP were 92.2–109% and 16–60.6%, respectively. Diffusion coefficients estimated by migration modelling showed a reduction of more than two orders of magnitude for all surrogate compounds under high pressure at 700 MPa ( = 8.0) relative to equivalent TP at 0.1 MPa ( = 13.1). The relative Tg increase of PP copolymer under compression at 700 MPa was estimated as Tg+94°C. For 10% ethanol, average migrations after TP and HPP were 9.3–50.9% and 8.6–22.8%, respectively. During extended storage, migration into both simulants from HPP-treated samples was initially slower than that from untreated or TP-treated films. However, after 8–24 hours of storage, the differences in percent migration of selected surrogates were not significant (p > .05) among the treated PP films. Therefore, the physical changes of PP films that occur during HPP appear to be reversible with a return to their original dimensions and diffusion properties after decompression.