Solvent Removal Research Articles

Film Formation Control for High Performance Dion–Jacobson 2D Perovskite Solar Cells

AbstractDion–Jacobson (DJ) 2D hybrid perovskite semiconductors offer improved environmental stability and higher structural diversity in comparison with their 3D analogous. However, lacking of controlled perovskite crystallization makes it a challenge to achieve high charge transport for photovoltaic devices. Here, a detailed understanding of effects on film formation during different solution‐casting processes for the DJ perovskite (PDMA)(MA)n−1PbnI3n+1 (<n> = 4, PDMA refers to 1,4‐phenylenedimethanammonium) in the final film structure and photovoltaic outcomes is presented. Faster removal of solvent from solution via hot‐casting or antisolvent dripping results in a more uniform thickness distribution of quantum wells. This eventually enhances carrier transport greatly along perpendicular direction and increases power conversion efficiencies. A high efficiency of 15.81% is achieved for the hot‐casting devices, which is also the highest for aromatic spacer‐based DJ perovskite solar cells. This work helps to better understand the control of film formation during solution‐casting for high performance solar cells.

Photocatalytic degradation of pharmaceutical pollutants using zinc oxide supported by mesoporous silica

The preparation of mesoporous silica supported zinc oxide photocatalyst (MS/ZnO) was carried out using the direct and indirect approaches (impregnation) in solvent media and grinding approach (mechanochemical) in a solvent-free media. This showed the dissemination of zinc oxide nanoparticles over mesoporous substrates that associated with the formation of a secondary phase of ZnO crystallites on the mesoporous materials. Consequently, a noticeable reduction of the total surface areas, pore volume and average pore size of mesoporous materials was affirmed due to a combination of ZnO nanoparticles, which entirely investigated via the N2 adsorption and desorption isotherms. In this respect, the efficiency of the photocatalysts was recognized using the photo-degradation reaction of Ibuprofen (IBP) as an assigned model of contaminant. Interestingly, the prepared photocatalysts using grinding approach (the mechanochemical approach, the focus of this research) sustained the best photocatalytic efficacy compared to the old-style wetness impregnation approach. This is also commensurate with a complete dispersion of ZnO on mesoporous material in a solvent-free media. Overall, the recent research has confirmed the merits and flexibility of the grinding approach in the preparation of MS/ZnO photocatalyst that incorporated with an efficient removal of solvent.

Application of superhydrophobic ZnO rod composites with environmentally-friendly and photodegradation properties in water environment treatment

The treatment of water pollution is faced with a severe postgraduate examination, which shows that pollutants of different properties, such as water-soluble and non-water-soluble pollutants, exist at the same time. In this paper, superhydrophobic S-ZnO/BiOBr cotton (SH cotton) is designed, which has the ability to degrade water-soluble pollutants through light response and the performance of selective removal of organic solvents. The water contact angle of droplets on the surface of the material reached 162°, on which toluene spread rapidly. When applied to an environment with water-soluble pollutants, the material showed an excellent cyclic degradation ability, and the degradation efficiency of 5 cycles’ was higher than 98.4%. Importantly, the 3 cycles of outdoor degradation efficiency was higher than 92.1% under the actual working conditions. The VB positions of the S-ZnO and BiOBr were calculated to be 2.89 eV and 2.96 eV, respectively. The CB positions of the S-ZnO and BiOBr were calculated to be −0.31 eV and 0.38 eV, respectively.

Phase-Dependent Reactivity and Host-Guest Behaviors of a Metallo-Macrocycle in Liquid and Solid-State Photosensitized Oxygenation Reactions.

The photochemical oxygenation reactions of a host-guest complex, pCp⊂[Ag2L0](SbF6)2 (pCp = [2.2]paracyclophane) have been investigated in solution and in the solid state, using the macrocyclic ligand L0 having four anthracene moieties in the framework. As a result, it was found that the reactivity and host-guest functions show remarkable phase dependence. In solution, the photosensitized oxygenation of all the anthracene moieties of L0 resulted in a fully oxygenated macrocycle [Ag2L4](SbF6)2 as the final product, while simultaneously the guest molecule was dissociated from the macrocyclic cavity. On the other hand, in an amorphous solid of pCp⊂[Ag2L0](SbF6)2 prepared by decomposing single crystals through the removal of the crystalline solvent, the oxygenated site of L0 was significantly controlled to provide a site-selectively oxygenated inclusion complex, pCp⊂[Ag2L1](SbF6)2, possessing a mono-oxygenated Cs-symmetrical macrocyclic skeleton.

Enhanced Skin Permeation of Estradiol by Dimethyl Sulfoxide Containing Transdermal Patches.

Dimethyl sulfoxide is a well-known and widely used dermal penetration enhancer. Its incorporation in transdermal patches would be highly desirable; however, due to its volatility this is extremely challenging. Here, we report on the feasibility of a dimethyl sulfoxide (DMSO) containing transdermal system containing estradiol as a model compound. Transdermal patches were prepared from duro-tak® 387-2510 containing various DMSO concentrations at different drying temperatures. The resulting patches were analyzed for DMSO content, estradiol and DMSO release, estradiol and DMSO permeation through excised porcine skin, and recrystallization during stability testing. Drying conditions in the range of 35° to 40° allowed a complete polymer solvents removal while retaining significant amounts of DMSO (≤10 mg/patch). Estradiol skin permeation increased 4-fold (Jss = 4.12 µg/cm−2·h−1) compared to DMSO-negative control (Jss = 1.1 ± 0.2 µg/cm−2·h−1). As additional benefit, estradiol recrystallization was inhibited by DMSO at even lowest solvent concentrations. Storage stability was limited to 6 months at 25 °C with a surprising discrepancy between DMSO content (significantly lower) and flux (not significantly different). Although the technical feasibility range is relatively narrow, such DMSO-containing matrix-type patches are able to significantly enhance drug permeation through the skin while ameliorating the product stability against recrystallization.

Reversible Solvatochromism of Polydiacetylenes Based on Extensively Hydrogen-Bonded Tubular Arrays

Since the pioneering discovery by Wagner, polydiacetylenes (PDAs) and their solvatochromic properties (typically blue-to-red or purple transitions) have been the subject of extensive research efforts. Without exception, PDAs have been found to undergo irreversible solvent-induced color changes, and no cases exist in which initial blue states of the PDAs are regenerated after solvent removal. Herein, we describe the first example of a reversibly solvatochromic PDA that is derived from a macrocyclic diacetylene (MCDA) containing four carboxylic acid moieties. Infrared spectroscopic studies confirmed the synergetic interplay of intra- and intermolecular hydrogen-bonding interactions to control the reversibility. The weak intramolecular hydrogen bonds allowed a solvent-induced distortion of the PDA backbone (purple state) by releasing unpolymerized monomers, while the strong and networked intermolecular hydrogen-bonding interactions ensured the rigidity of the tubular channels and served as the driving forces for the recovery of the initial conformation (blue state).

Aerogels as porous structures for food applications: Smart ingredients and novel packaging materials

• Aerogels are nanostructured materials with low bulk density and open porosity. • Food-grade aerogels are prepared from several bio-based materials. • Aerogels can be loaded to obtain delivery systems for food and packaging applications. • Aerogels can turn into oleogels by oil absorption within the pores. Aerogels are nanostructured materials with low density, high surface area (>150 m 2 /g) and open porosity (typically 95–99.99 %). They are obtained by solvent removal from gels while preserving network structure. Hydrogels, organogels and even tissues can be optimal sources of aerogels with limitless customization of format and texture. Aerogels might be used for a range of advanced food applications: from smart ingredients controlling nutrient release to delivery systems for active compounds; from fat substitutes to novel biodegradable and intelligent food packaging materials. This review article summarizes recent developments of aerogels in food applications, analyzing research challenges and prospecting future markets.

A Contribution to the Solid State Forms of Bis(demethoxy)curcumin: Co-Crystal Screening and Characterization.

Bis(demethoxy)curcumin (BDMC) is one of the main active components found in turmeric. Major drawbacks for its usage are its low aqueous solubility, and the challenging separation from other curcuminoids present in turmeric. Co-crystallization can be applied to alter the physicochemical properties of BDMC in a desired manner. A co-crystal screening of BDMC with four hydroxybenzenes was carried out using four different methods of co-crystal production: crystallization from solution by slow solvent evaporation (SSE), and rapid solvent removal (RSR), liquid-assisted grinding (LAG), and crystallization from the melt phase. Two co-crystal phases of BDMC were obtained with pyrogallol (PYR), and hydroxyquinol (HYQ). PYR-BDMC co-crystals can be obtained only from the melt, while HYQ-BDMC co-crystals could also be produced by LAG. Both co-crystals possess an equimolar composition and reveal an incongruent melting behavior. Infrared spectroscopy demonstrated the presence of BDMC in the diketo form in the PYR co-crystals, while it is in a more stable keto-enol form in the HYQ co-crystals. Solubility measurements in ethanol and an ethanol-water mixture revealed an increase of solubility in the latter, but a slightly negative effect on ethanol solubility. These results are useful for a prospective development of crystallization-based separation processes of chemical similar substances through co-crystallization.

Development of highly hydrophobic and superoleophilic fluoro organothiol-coated carbonized melamine sponge/rGO composite absorbent material for the efficient and selective absorption of oily substances from aqueous environments

The removal of various oils, petroleum products and organic solvents from water has a great importance for environmental protection. In this study, highly hydrophobic and superoleophilic fluoro organothiol-coated carbonized melamine sponge/rGO composite absorbent material (CMS/rGO/PFDT) material was prepared as a new absorbent for the cleanup of oil spills and selective separation of oil-water mixtures. The results of contact angle, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman measurements proved that the preparation of new absorbent material was successfully performed. CMS/rGO/PFDT displayed excellent hydrophobicity with a high-water contact angle of 143.2°. and superoleophilicity with an oil-contact angle of 0°. This absorbent was unsinkable in water and could absorb the hydrophobic organic contaminants up to 55 times of its own weight. CMS/rGO/PFDT could effectively and selectively absorb the oily substances from olive oil-water and gasoline-water emulsions and achieved the continuous oil-water separation with the assistance of a vacuum pump. The developed CMS/rGO/PFDT material may be a potential absorbent in the absorptive removal of oily substances and organic solvents from oily wastewater and in the separation of oil-water mixture.

Printing High-Efficiency Perovskite Solar Cells in High-Humidity Ambient Environment-An In Situ Guided Investigation.

Extensive studies are conducted on perovskite solar cells (PSCs) with significant performance advances (mainly spin coating techniques), which have encouraged recent efforts on scalable coating techniques for the manufacture of PSCs. However, devices fabricated by blade coating techniques are inferior to state‐of‐the‐art spin‐coated devices because the power conversion efficiency (PCE) is highly dependent on the morphology and crystallization kinetics in the controlled environment and the delicate solvent system engineering. In this study, based on the widely studied perovskite solution system dimethylformamide–dimethyl sulfoxide, air‐knife‐assisted ambient fabrication of PSCs at a high relative humidity of 55 ± 5% is reported. In‐depth time‐resolved UV–vis spectrometry is carried out to investigate the impact of solvent removal and crystallization rate, which are critical factors influencing the crystallization kinetics and morphology because of adventitious moisture. UV–vis spectrometry enables accurate determination of the thickness of the wet precursor film. Anti‐solvent‐free, high‐humidity ambient coatings of hysteresis‐free PSCs with PCEs of 21.1% and 18.0% are demonstrated for 0.06 and 1 cm2 devices, respectively. These PSCs exhibit comparable stability to those fabricated in a glovebox, thus demonstrating their high potential.

Imprinted membranes for sustainable separation processes

The rapid industrial growth and the necessity of recovering and recycling raw materials increased the interest in the production of highly selective and efficient separation tools. In this perspective, a relevant input was given by the membrane-based technology and the production of imprinted membranes, which possess specific recognition properties at molecular and ionic level, offers the possibility of developing sustainable and green processes. Furthermore, the integration of imprinted membranes with traditional or membrane-based approaches is a promising strategy in the logic of process intensification, which means the combination of different operations in a single apparatus. This work discusses the concept and separation mechanisms of imprinted membranes. Furthermore, it presents an overview of their application in organic solvent nanofiltration, for the removal of toxic agents and recovery solvent, as well as valuable compounds. The recent advances in water treatment, such as pesticide removal and recovery of metal ions, are also discussed. Finally, potential applications of imprinted membranes in hybrid processes are highlighted, and a look into the future of membrane separations for water treatment and recovery ofcritical raw materials is offered.

Electrospun Nanofibers Withstandable to High-Temperature Reactions: Synergistic Effect of Polymer Relaxation and Solvent Removal

Fiber breakage is found to be a ubiquitous phenomenon during the thermal treatments for electrospun nanofibers, because of the presence of solvent molecules and unrelaxed assembly of polymer chains. Here a strengthening strategy is designed by introducing a pre-heating stage for the as-spun nanofibers. At a temperature above the polymer’s glass transition temperature, the chains can get sufficiently relaxed by the aid of hot solvent, and at the same time, the solvent confined in the entangled chains can fully and steadily evaporate, but not erupt, off the nanofiber, when the temperature is just as high as the boiling point. Therefore, the nanofibers become more uniform in structure and can withstand the subsequent thermal reactions. For polyacrylonitrile-based electrospinning, such strategy can improve the final tensile strength from 42 to 112 MPa for the nanofiber films.

Preparation of hydrophobic macroinimer-based novel hybrid sorbents for efficient removal of organic liquids from wastewater.

Herein, the synthesis of hydrophobic macroinimer-based hybrid sorbents and their use in the removal of organic solvents from wastewater is explored. Polydimethylsiloxane (PDMS), 4,-4'-azobis-4-cyanopentanoyl chloride (ACPC), and methacryloyl chloride were reacted via bulk condensation polymerization to synthesize the macroinimer. The organogel systems were then prepared with macroinimer using different acrylic monomers of methyl acrylate, ethyl acrylate, and butyl acrylate without any additional crosslinker and initiator. The structural properties of the obtained final products were characterized by FT-IR, 1H-NMR, and TGA. The effect of alkyl chain length and macroinimer moieties in the organogel networks, as well as the swelling capacities of the prepared gels, was evaluated for different organic solvents and oils. The maximum solvent absorbencies of macroinimer-based organogels were determined as 85.3%, 100.9%, 1422.1%, 1660.0%, 3809.3%, and 5032.2% for diesel oil, gasoline, acetone, benzene, tetrahydrofuran (THF), and dichloromethane (DCM), respectively. Furthermore, adsorption-desorption kinetics, selective absorption from oil/water mixtures, temperature effect on the absorption capacity, and reusability tests were investigated. Obtained results showed that the prepared organogels possessed high swelling, efficient absorption capacity, and good oil separation performance in the removal of organic solvents from wastewater. The temperature-dependent absorption study shows no significant change in absorption capacity. Thus, the prepared macroinimer-based organogels in the present study demonstrate potential as prospective sorbents for organic pollutant cleanup from wastewater.

Evaporation-induced self-assembly of silver nanospheres and gold nanorods on a super-hydrophobic substrate for SERS applications

Surface-enhanced Raman scattering (SERS) has drawn attention for broad applications. We successfully fabricated highly effective SERS structures via evaporation-induced self-assembly of blend nanoparticles containing sliver nanospheres (Ag NSs) and gold nanorods (Au NRs) on a super-hydrophobic (SH) substrate. On the SH substrate, the droplets of the mixed aqueous solution of silver nanospheres (Ag NSs), gold nanorods (Au NRs), and probe molecules can preserve their spherical shape during the evaporation process, and the probe molecules (R6G) are confined into extremely small areas after solvent removal due to hydrophobicity-enhanced concentration effects. The Raman enhancement effect of the blend nanoparticles with 40 vol% Ag NSs is far higher than that of the other samples. The structure of the aggregated Ag NSs on the film-like Au NRs greatly enhances the SERS effect of Ag NSs, which is optimal for the blend system with 40 vol% Ag NSs. The SERS structure also displays excellent signal reproducibility (RSD < 10%) and low detection limits (0.5 nM). Thus, this work offers a simple and efficient strategy to fabricate a highly effective SERS structure with broad applications in environmental science, analytical chemistry, etc.

Far Infrared-assisted Sample Extraction and Solvent Removal for Capillary Electrophoretic Determination of the Bioactive Constituents in Citri Reticulatae Pericarpium

Background: Sample preparation is crucially important for the capillary electrophoretic measurement of the bioactive constituents in Citri Reticulatae Pericarpium because conventional solvent extraction is time-consuming and the solvent peaks seriously interfere with the measured capillary electropherograms. Objective: The objective of the present study is to establish far infrared-assisted sample preparation approaches for the analysis of Citri Reticulatae Pericarpium. Methods: Synephrine and hesperidin in Citri Reticulatae Pericarpium were determined by capillary electrophoresis in combination with far infrared-assisted sample extraction and solvent removal. Results: The effects of detection potentials, irradiation times and the voltages applied to the infrared generator were investigated to acquire the optimal assay conditions. Synephrine and hesperidin could be well separated within 6 min at a separation voltage of 9 kV in an alkaline borate solution. Satisfactory linearity was observed over the concentration range of 0.001 to 1 mM with the detection limits of 0.43 and 0.52 μM for synephrine and hesperidin, respectively. The results exhibited that far infrared irradiations could enhance the efficiencies of sample extraction and solvent removal during the sample preparation of Citri Reticulatae Pericarpium. The extraction time was significantly reduced to 6 min while the interference of the solvent peaks towards the electropherograms was eliminated. Conclusion: Far infrared-accelerated extraction and solvent removal were employed in the capillary electrophoretic determination of the bioactive constituents in Citri Reticulatae Pericarpium with satisfactory results. The ease, simplicity, efficiency and low cost of the novel sample preparation approaches indicate they may find a wide range of applications.

About solvents used in the preparation of oils for cosmetic products complying with the Cosmos standard

Solvents have a bad reputation in the cosmetics world, at least as regards the production of specialty vegetable oils used in this market. In order to do without these solvents, the cosmetics industry tends to use only mechanically produced oils. However, there is a range of seeds for which mechanical extraction is not satisfactory. This is the case with rare, expensive, and oil-poor seeds for which pressing does not give good yields, and results in high production costs. These are also hard seeds that cannot be pressed without causing the presses to become intensely hot, and this affects the quality of the oils. In recent years, our laboratory has worked on the development of extraction techniques with ethanol and the EcoXtract® solvent (2-methyloxolane) in order to provide professionals with production methods compatible with the COSMOS standard. Ethanol is not a good solvent for oils, especially in the presence of water and at low temperature. This drawback can be turned into an advantage to recover the oil (without distillation of the solvent) by cold decantation. The extraction is carried out on the hot components, and the oil is recovered by cooling the saturated miscella for the precipitation of the lipid phase. This process makes it possible to limit the energy consumption necessary for the recovery of the oil and the regeneration of the solvent. The great advantage for oils intended for the cosmetic market is that ethanol has a better solvent power for polar lipids compared to hexane and mechanical extraction. It is possible to split the lipid extract into neutral lipids and polar lipids by adjusting the precipitation temperature or by partial distillation. At the refining step, it is also possible to deacidify and remove contaminants from crude oil by liquid-liquid extraction with ethanol. We have recently obtained interesting results by reducing the phthalate concentration of walnut oils by 90%. The use of ethanol for oil neutralization is a process which generates less loss of neutral oil than the alkaline neutralization of a mixture with high acidity, and this is less harmful than physical refining during the production of 3-MCPD esters, esters of glycidol, and trans fatty acids. EcoXtract® is a solvent derived from the chemistry of pentoses in biomass. This solvent has very good oil solvation capacities and less biological toxicity than hexane. Its production has an acceptable carbon footprint and good sustainability characteristics. It is recognised by Ecocert as suitable for producing COSMOS ingredients. Compared to ethanol, its use requires fewer preparation steps (ethanol requires rigorous drying before extraction) and it requires less circulating solvent per kilo of oil extracted. The solvent removal from the meal requires less energy and allows the use of direct steam to aid in the removal of the solvent since the miscibility of water in this solvent is limited to 4.5 g/100g.

Spin transition triggered by desorption of crystal solvents for a two-dimensional cobalt(ii) complex with hydrogen bonding.

[Co(5tpybNOH)2](BPh4)2 (1; 5tpybNOH = 5,5''-bis(N-tert-butyl hydroxylamino)-2,2':6',2''-terpyridine) has a two-dimensional (2D) structure through a hydrogen bond between the NOH sites, as revealed by X-ray crystallography. The crystal solvents were desorbed above 300 K as shown by thermal analyses and powder X-ray crystallography. The removal of the crystal solvents allowed irreversible structural changes and a spin transition of the Co centre from S = 1/2 to 3/2.

Simple and Rapid (Extraction) Protocol for NMR Metabolomics-Direct Measurement of Hydrophilic and Hydrophobic Metabolites Using Slice Selection.

Investigating the metabolic profiles of solid sample materials with solution nuclear magnetic resonance (NMR) spectroscopy requires the extraction of these metabolites. This is commonly done by using two immiscible solvents such as water and chloroform for extraction. Subsequent solvent removal makes these extraction procedures very time-consuming. To shorten the preparation time of the NMR sample, the following protocol is proposed: the metabolites from a solid or liquid sample are extracted directly in the NMR tube, the NMR tube is centrifuged, and the metabolite profiles in the aqueous and organic phases are determined by using slice-selective proton NMR experiments. This protocol was tested with 11 black teas and 11 green teas, which can be easily distinguished by their metabolic profiles in the aqueous phase. As a test case for liquid samples, 29 milk samples were investigated. The geographical origin of the diaries where the milk was processed could not be determined unequivocally from the metabolic profiles of the hydrophilic metabolites; however, this was easily seen in the lipid profiles. As shown for the different test samples, the extraction protocol in combination with slice-selection NMR experiments is suitable for metabolic investigations. Because samples are rapidly processed, this approach can be used to explore different extraction strategies for metabolite isolation.

Enhanced coproduction and trade-off of the hydrogen and butanol in the coupled system of pervaporation and repeated-cycle fixed-bed fermentation

In the study, a coupled system of pervaporation and repeated-cycle fixed bed fermentation with the bagasse as the carrier material was developed. Three repeated cycles of fermentation lasting for 540 h was efficiently carried out to coproduce hydrogen and butanol with the strain Clostridium acetobutylicum. From 1st cycle to 3rd cycle, the average hydrogen productivity and butanol productivity were around 130 mLL−1 h−1 and 0.15 gL−1 h−1, respectively. Average hydrogen yield and butanol yield were around 0.17 Lg−1 and 0.19 gg−1. The hydrogen and butanol production per unit cell weight were 27 Lg−1 and 31 gg−1, which were more than two times of those in a conventional repeated-cycle fermentation. The trade-off and competition between the hydrogen and butanol production was studied and analyzed. Compared with the pervaporation-free fermentation, the hydrogen yield was decreased by 14 % and butanol yield was increased by 27 % in the coupled system. Instantaneous solvent removal from the broth by pervaporation changed probably the metabolic pathway to more butanol production over hydrogen. From 1st cycle to 3rd cycle, the respiration heat generated during each fermentation cycle could cover 45 %, 24 % and 37 % of the total energy requirement of the pervaporation achieving the best use of the energy.

Effects of the Glass-Forming Ability and Annealing Conditions on Cocrystallization Behaviors via Rapid Solvent Removal: A Case Study of Voriconazole.

The kinetic entrapment of molecules in an amorphous phase is a common obstacle to cocrystal screening using rapid solvent removal, especially for drugs with a moderate or high glass-forming ability (GFA). The aim of this study was to elucidate the effects of the coformer’s GFA and annealing conditions on the nature of amorphous phase transformation to the cocrystal counterpart. Attempts were made to cocrystallize voriconazole (VRC) with four structural analogues, namely fumaric acid (FUM), tartaric acid (TAR), malic acid (MAL), and maleic acid (MAE). The overall GFA of VRC binary systems increased with decreasing glass transition temperatures (Tgs) of these diacids, which appeared as a critical parameter for predicting the cocrystallization propensity such that a high-Tg coformer is more desirable. A new 1:1 VRC-TAR cocrystal was successfully produced via a supercooled-mediated re-cocrystallization process, and characterized by PXRD, DSC, and FTIR. The cocrystal purity against the annealing temperature displayed a bell-shaped curve, with a threshold at 40 °C. The isothermal phase purity improved with annealing and adhered to the Kolmogorov–Johnson–Mehl–Avrami kinetics. The superior dissolution behavior of the VRC-TAR cocrystal could minimize VRC precipitation upon gastric emptying. This study offers a simple but useful guide for efficient cocrystal screening based on the Tg of structurally similar coformers, annealing temperature, and time.