Simple Solvent Exchange Research Articles

Preparing a microemulsion-loaded hydrogel for cleaning wall paintings and coins

Removing unwanted materials, such as organic coatings and soil, from the cultural relic surface is a complex and significant task in the field of cultural heritage conservation. Microemulsion-loaded gel can effectively and safely remove those organic coatings and soil. Here, we employed a simple solvent exchange strategy to prepare a microemulsion-loaded polyvinyl alcohol/polyethyleneimine (PVA/PEI) hydrogel. First, PVA and PEI were dissolved into DMSO to form a gel. Then, the gel was immersed into a microemulsion composed of water, ethyl acetate, propylene carbonate, sodium dodecyl sulfate, and 1-pentanol to exchange DMSO. Microemulsion-loaded PVA/PEI hydrogel can be synthesized by completely substituting DMSO. To investigate the microstructure, rheological properties, and mechanical properties of the gel, scanning electron microscopy, a rheometer, and a universal testing machine were used, respectively. Fourier transform infrared (FT-IR) analysis was conducted to explore the synthesis mechanism and confirm the successful loading of microemulsion within the microemulsion-loaded PVA/PEI hydrogel. Furthermore, FT-IR, a depth-of-field microscope, and a glossmeter were utilized to evaluate the cleaning efficiency of the microemulsion-loaded PVA/PEI hydrogel for removing animal glue and soil from the surfaces of cultural relics. Moreover, an X-ray fluorescence spectrometer was used to analyze the element component of the ancient coin. The application results showed that the microemulsion-loaded PVA/PEI hydrogel can effectively remove animal glue from an ancient wall painting surface. Moreover, it is capable of removing soil from an ancient coin surface as well, which helped to confirm the age of the coin. This offers a novel method to prepare microemulsion-loaded hydrogel and demonstrates great potential in the cleaning for cultural heritage.

Low-salt organohydrogel electrolytes for wide-potential-window flexible all-solid-state supercapacitors

Flexible supercapacitors have received increasing attention due to their high power density, long cycle life and excellent safety, however, their limited energy density restrains their practical applications. Here, a designed organohydrogel electrolyte strategy boosted the electrochemical potential window (ESW) for flexible all-solid supercapacitor was demonstrated, by which a record-high ESW of 5 V is achieved, accompanied by improved cyclic stability and wider temperature adaptability. Hydrogen-bond of water to DMSO was found to be competitive with cationic hydration, and a wide ESW was achieved at lower salt and DMSO concentrations. DMSO-H2O/alginate/PAAm hydrogel electrolytes were prepared by simple solvent exchange, and it was found that the synergistic interactions between DMSO, water and hydrogel significantly reduced water activity in the hydrogel and realized the high ESW. Moreover, Dimethyl sulfoxide forms abundant hydrogen bonds with water and the hydrogel skeleton, which significantly improves the mechanical properties, freezing resistance, and temperature adaptability of the hydrogel electrolyte. The flexible all-solid-state supercapacitor assembled based on DMSO-H2O/alginate/PAAm hydrogel electrolyte and interdigital electrodes exhibits 2.4 V ESW, stability under different folding angles, adaptability to different temperatures ranging from −20 to 70 °C, and integration performance. The device demonstrates excellent cycling stability and retains 98.66% of capacitance after 10,000 cycles, suggesting that it has the potential to meet the requirements of flexible electronics.

Water-Triggered Segment Orientation of Long-Lasting Anti-Biofouling Polyurethane Coatings on Biomedical Catheters via Solvent Exchange Strategy.

The formation of biofilm and thrombus on medical catheters poses a significant life-threatening concern. Hydrophilic anti-biofouling coatings upon catheter surfaces with complex shapes and narrow lumens are demonstrated to have the potential in reducing complications. However, their effectiveness is constrained by poor mechanical stability and weak substrate adhesion. Herein, a novel zwitterionic polyurethane (SUPU) with strong mechanical stability and long-term anti-biofouling is developed by controlling the ratio of sulfobetaine-diol and ureido-pyrimidinone. Once immersed in water, as-synthesized zwitterionic coating (SUPU3 SE) would undergo a water-driven segment reorientation to obtain much higher durability than its direct drying one, even under various extreme treatments, including acidic solution, abrasion, ultrasonication, flushing, and shearing, in PBS at 37 °C for 14 days. Moreover, SUPU3 SE coating could achieve a 97.1% of exceptional reducing protein fouling, complete prevention of cell adhesion, and long-lasting anti-biofilm performance even after 30 days. Finally, the good anti-thrombogenic formations of SUPU3 SE coating with bacterial treatment are validated in blood circulation through an ex vivo rabbit arteriovenous shunt model. This work provides a facile approach to fabricating stable hydrophilic coating through a simple solvent exchange to reduce thrombosis and infection of biomedical catheters.

Enhancing the mechanical performance of lignin based hydrogel via lignin acetylation

Kraft lignin (KL) is an industrial byproduct of pulp preparation from woody biomass and is mainly burned for energy recovery. To explore value-added applications of KL, it was first acetylated, and acetylated lignin (AcL) was combined with poly(N,N-dimethylacrylamide) to prepare tough lignin hydrogels crosslinked by hydrophobic lignin domains via a simple solvent exchange method. The AcL hydrogels (AcLGs) with optimum mechanical properties have a high tensile strength of 1.7 MPa, large Young's modulus of 1 MPa, and super high fracture energy of ∼47600 J m−2. The Young's modulus and tensile strength of AcLG are 60 and 6 times higher than those of the pristine KL based hydrogel, respectively. AcLG had a weak inhibitory effect on Chinese hamster lung cell proliferation. Owing to its good mechanical properties and noncytotoxicity, AcLG has excellent potential as a biomedical material.

Solvent‐mediated single‐crystal‐to‐single‐crystal transformation of metal–organic cage self‐assembly

AbstractMetal–organic polyhedra (MOPs) are intrinsically porous cage‐like structures; however, they frequently display low porosity due to their agglomeration caused by solvent exchange and removal, which results in the blockage of pore windows. This study presents the unprecedented single‐crystal‐to‐single‐crystal transformation of a cuboctahedral MOP‐OH ([Cu24L24], H2L = 5‐hydroxybenzene‐1,3‐dicarboxylic acid) using a simple solvent exchange from coordinating N,N‐diethylformamide to weakly coordinating chloroform. Following the solvent exchange, the interaction between the cages in the resultant MOP self‐assembly is strengthened while the interaction between the cages and solvents is decreased. The N2 uptake and the surface areas of the MOPs are highly correlated with the cage arrangements: the tightly packed MOPs in chloroform are the most porous among the prepared samples, whereas the loosely packed MOPs are less porous. Scanning electron microscopy reveals that the tight packing of MOPs prevents the crystals from being deteriorating during solvent removal.

Adsorption Behavior of a Gd-Based Metal-Organic Framework toward the Quercetin Drug: Effect of the Activation Condition.

A carboxylate gadolinium-based metal-organic framework (Gd-MOF) is an exceptional candidate for magnetic resonance imaging agents, but its low drug adsorption capacity hinders this MOF from being used as a theragnostic agent. In this work, the Gd-MOF was synthesized by a simple solvothermal method. Then, different activation situations, including various solvents over different time periods, were applied to enhance the specific surface area of the synthesized MOF. Different characterization analyses such as X-ray diffraction and Brunauer-Emmett-Teller along with experimental quercetin adsorption tests were done to study the crystalline and physical properties of various activated MOFs. In the following, the MOF activated by ethanol for 3 days (3d-E) was chosen as the best activated MOF due to its crystallinity, highest specific surface area, and drug adsorption capacity. More explorations were done for the selected MOF, including the drug adsorption isotherm, thermodynamics, and pH effect of adsorption. The results show that the activation process substantially affects the crystallinity, morphology, specific surface area, and drug adsorption capacity of Gd-MOFs. An optimized activation condition is proposed in this work, which shows an impressive enhancement of the specific surface area of Gd-MOFs just by simple solvent exchange method employment.

Carbons derived from alcohol-treated bacterial cellulose with optimal porosity for Li–O2 batteries

Porous carbons are important cathode materials for metal-air batteries, but the most usual methods to prepare these porous structures are complex and of high cost. We have prepared porous carbons from bacterial cellulose (BC) hydrogels by a simple water-alcohol solvent exchange before carbonization. Alcohol treatment facilitates looser and more open structures than untreated BC, resulting in porous carbon structures with high surface area, appropriate for electrochemical applications. Used as cathodes in lithium-oxygen batteries, the carbon derived from 1-butanol treated BC has excellent discharge capacity (5.6 mA h cm−2) and good cycle life. This work presents a sustainable, straightforward and fast way to prepare porous carbon materials from BC.

Fully Solvated, Monomeric ReII Complexes: Insights into the Chemistry of [Re(NCCH3)6]2.

The oxidation of [Re(η6-C10H8)2]+ with AgI in acetonitrile yields [Re(NCCH3)6]2+. This fully solvated ReII compound was characterized by spectroscopic methods and X-ray structure analyses. We show that [Re(NCCH3)6]2+ acts as a precursor complex for a variety of substitution reactions. Treatment with monodentate triphenylphosphine (PPh3) and bidentate 1,2-bis(diphenylphosphino)ethane (dppe) yields the complexes [trans-Re(PPh3)2(NCCH3)4]2+ and [trans-Re(dppe)2(NCCH3)2]+, respectively. [trans-Re(dppe)2(NCCH3)2]+ is oxidized under mild conditions by AgI to its ReII analogue [trans-Re(dppe)2(NCCH3)2]2+. Reactions of [Re(NCCH3)6]2+ with a halide mixture consisting of NaX and AgX (X = Cl, I) result in the formation of the corresponding ReIII complexes [trans-ReX2(NCCH3)4]+. [trans-ReBr2(NCCH3)4]+ can be obtained directly from [Re(η6-C10H8)2]+ by oxidation with FeBr3 in acetonitrile. The title compound is thus a convenient starting material for ReII and ReIII complexes by simple solvent exchange, which are otherwise difficult to access.

Encapsulated Nanodroplets for Enhanced Fluorescence Detection by Nano-Extraction.

Enhancement of the detection signal of fluorescence microscopy in highly diluted solutions is of great importance in chemical analysis, sensing, and bioassay applications. Surface nanodroplets with atto- to femto-liter volumes are promising tools for sensitive online detection by integrating their extremely efficient nano-extraction and optical advantages. In this paper, the development of novel basic units of nanodroplets-in-a-microdroplet by simple solvent exchange is reported. The encapsulated nanodroplets are applied for ultrasensitive and online detection in fluorescence imaging. The biphasic nature of the droplet composite enables simultaneous extraction and enrichment of both hydrophobic and hydrophilic compounds. Furthermore, the desirable lensing effect of the curved surface of the nanodroplets enhances the collection of light emitted from the fluorophore extracted in the droplets by ≈60-fold, allowing sensitive and quantitative analysis of the fluorophore using fluorescence microscopy. The results highlight the potential of encapsulated nanodroplets as a simple and innovative method of signal enhancement in chemical analysis. By integrating selective concentration, extraction, and sensitive detection, the encapsulated nanodroplets reported here may have broad applications in many chemical and biologicalmatrices.

Aggregation-Induced Emission Properties of Glutathione and L-Cysteine Capped CdS Quantum Dots and their Application as Zn(II) Probe.

Targeting to obtain better water solubility and stability and less aggregation-caused quenching effects of quantum dots, two kinds of thiol molecules, glutathione and L-cysteine, were firstly united to offer stabilizing ligands for aqueous synthesized CdS quantum dots, which exhibited sensitive aggregation-induced emission properties. Fluorescent intensity of the CdS quantum dots was enhanced about 5 folds by simple solvent exchange from water to 90vol% PEG200. Restriction of intramolecular motions in an aggregate state was probably the main cause of the phenomenon. At the same time, fluorescent intensity of CdS quantum dots in the presence of zinc ions was able to be enhanced about 2.2 folds. Based on the researches, a handy metal enhanced fluorescent probe for detecting zinc ions was established. And the detection limit was 0.58μmol/L. Zinc ions as a bridge among CdS quantum dots to form aggregates limited motions of CdS quantum dots to a certain extent and simultaneously enhanced their fluorescence emission intensities. Meanwhile, activation of surface states of CdS quantum dots also led to emission enhancement. Both of the two factors together contributed to the fluorescence enhancement and ultimately to the sensitivity to zinc ion sample detection.

Z-scheme photocatalytic NO removal on a 2D/2D iodine doped BiOIO3/g-C3N4 under visible-light irradiation

We report an unique 2D/2D Iodine doped BiOIO3/g-C3N4 heterojunction was successfully prepared. The iodine doped BiOIO3 was prepared by a simple solvent exchange method and combined with g-C3N4 by solvothermal method. The prepared photocatalyst has potential application value in the future due to its excellent stable cycle property. BiOIO3 nanoplates and g-C3N4 nanosheets form a close interfacial contact directly, so the catalyst has higher charge transport efficiency and wide visible range due to the introduction of iodide ions. Synergistic heterojunction exhibits strong photocatalytic activity for degradation of NO at ppb-level under visible light, of which 30% Iodine doped BiOIO3/g-C3N4 can achieve a maximum removal rate of 57% for NO. According to the experimental results of ESR and other experiments, a more complex Z-scheme photocatalytic mechanism is proposed, which has stronger redox ability than the traditional mechanism.

Solvent exchange synthesis of C-doped ZnO bunches and their enhanced ethanol sensing properties

In this study, zinc complex bunches have been synthesized by a simple solvent exchange approach without any surfactant at room temperature. The zinc complex can be converted to C-doped ZnO bunches by a subsequent annealed process at 500∘C for 2[Formula: see text]h. The morphology and structure results show that the rectangle-shaped ZnO bunches are assembled by ZnO disks. The as-prepared C-doped ZnO bunches exhibit the highest sensitivity to 100[Formula: see text]ppm ethanol vapor at 240∘C. In addition the C-doped ZnO bunches also show excellent response-recover properties and stability, and good linearity in the range of 5–400[Formula: see text]ppm for potential applications.

Stabilizing Coacervate by Microfluidic Engulfment Induced by Controlled Interfacial Energy.

Low interfacial energy, an intrinsic property of complex coacervate, enables the complex coacervate to easily encapsulate desired cargo substances, making it widely used in encapsulation applications. Despite this advantage, the low interfacial energy of the complex coacervate makes it unstable against mechanical mixing, and changes in pH and salt concentration. Hence, a chemical cross-linker is usually added to enhance the stability of the complex coacervate at the expense of sacrificing all intrinsic properties of the coacervate, including phase transition of the coacervate from liquid to solid. In this study, we observed an abrupt increase in the interfacial energy of the coacervate phase in mineral oil. By controlling the interfacial energy of the coacervate phase using a microfluidic device, we successfully created double engulfed PEG-diacrylate (PEGDA) coacervate microparticles, named DEPOT, in which the coacervate is engulfed in a cross-linked PEGDA shell. The engulfed coacervate remained as a liquid phase, retained its original low interfacial energy property to encapsulate the desired cargo substances, and infiltrated into the target site by a simple solvent exchange from oil to water.

Hierarchical Morphology of Poly(ether ether ketone) Aerogels.

The phase diagram for the thermoreversible gelation of poly(ether ether ketone) (PEEK) in 4-chlorophenol (4CP) was constructed over broad temperature and concentration ranges, revealing that PEEK is capable of dissolving and forming gels in both 4CP and dichloroacetic acid (DCA) up to a concentration of 25 wt %. Highly porous aerogels of PEEK were prepared through simple solvent exchange followed by one of two drying methods of solvent removal from the wet gel: freeze-drying or supercritical CO2 fluid extraction (SC-drying). The field-emission scanning electron microscopy analysis showed that gelation of PEEK in 4CP, followed by SC-drying, produced aerogels with well-defined lamellar aggregates as compared to less ordered aggregates formed from DCA. Mechanical properties (in compression) were shown to improve with increasing density, resulting in equivalent compressive moduli at comparable density, regardless of the preparation method (gelation solvent selection, concentration variation, or drying method). Nitrogen adsorption-desorption isotherms indicate that PEEK aerogels are comprised of mesopores (2-50 nm diameter pores) formed from stacked crystalline lamella. PEEK aerogels prepared using SC-drying exhibit higher Brunauer-Emmett-Teller surface areas than freeze-dried aerogels of comparable density. The ultra-small-angle X-ray scattering/small-angle X-ray scattering (SAXS)/wide-angle X-ray scattering analysis revealed a hierarchical morphology of the PEEK aerogels with structural features from PEEK crystallites to agglomerates of stacked lamella that spanned a wide range of length scales. SANS contrast-matching confirmed that the morphological origin of the principle scattering feature in PEEK aerogels is stacked crystalline lamella. Nitrogen sorption measurements of porosity and the specific surface area of the PEEK aerogels were correlated with the SAXS analysis to reveal a remarkably high surface area attributed to the platelet-like, lamellar morphology. Contact angle and contact angle hysteresis (CAH) revealed that low-density PEEK aerogels (ρ < 0.15 g/cm3) have water contact angles above the superhydrophobicity cutoff angle (>150°) and a very low CAH near 1°.

The innovative fabrication and applications of carvacrol nanoemulsions, carboxymethyl chitosan microgels and their composite films.

Carvacrol (CA) was firstly made into physically stable nanoemulsions using an innovative spontaneous emulsification method with carvacrol itself as oil phase without introducing other carrier oils. Self-crosslinking carboxymethyl chitosan (CMC) microgels via intermolecular hydrogen bonds were then fabricated using a simple solvent exchange method with ethanol as poor solvent. The CMC microgels obtained were rapidly deposited on the surface of tin foil using an electrospray technique to produce the CMC films. The stability of the films in water was further intensified by using Ca2+ as cross-linking agent. Also, the carvacrol nanoemulsions (CA-NEs) were loaded into the CMC films by utilizing swelling property of CMC microgels in aqueous solution. The results showed that the CA-NEs@CMC composite films possess satisfactory antioxidant activity, good antibacterial activity against S. aureus and E. coli, and excellent ability to extend the shelf life of wheat bread. We believe that the present strategies to prepare CA-NEs, CMC microgels and their composite films also apply to other types of essential oils and polymers, and the CA-NEs@CMC composite film is an excellent candidate for the active packaging.

Water-Borne Perovskite Quantum Dot-Loaded, Polystyrene Latex Ink.

Highly lipophilic nanocrystals (NCs) of cesium lead halides were successfully embedded in polystyrene (PS) particles by deliberately controlling the swelling of the PS particles in the mixtures of good and bad organic solvents. The resulting composite particles were readily transferred into water via simple stepwise solvent exchange, which yielded water-borne perovskite NC-based inks with outstanding structural and chemical stability in aqueous media. Minimal change in the photoluminescence (PL) of the NCs loaded in the PS particles was visible after 1 month of incubation of the composite particles in water in a broad pH range from 1 to 14, which could otherwise be hardly realized. Loading into the PS particles also made the NCs highly stable against polar organic solvents, such as ethanol, intense light irradiation, and heat. The NC PL intensity slightly changed after the composite particles were heated at 75°C and under irradiation of strong blue light (@365 nm) for 1 h. Furthermore, the PS matrices could effectively inhibit the exchange of halide anions between two differently sized perovskite NCs loaded therein, thereby offering a considerable technical advantage in the application of multiple perovskite NCs for multicolor display in the future.

Tribological Properties of Double-Network Gels Substituted by Ionic Liquids

Since human body joints have a gel-like structure with low friction that persists for several decades, hydrogels have attracted much interest for developing low-friction materials. However, such advantages can hardly be realized in industrial usage because water in the gel evaporates easily and the gel deswells. The substitution of water with an ionic liquid (IL) is one of the effective ways to overcome this problem. In this study, we substituted water in a double network (DN) hydrogel with 3-ethyl-1-methyl-imidazolium ethylsulfate (EMI-EtSulf), a hydrophilic IL, via a simple solvent exchange method to obtain a DN ion gel. A compressive test and thermogravimetric analysis showed that the DN ion gel has a high compression fracture stress and improved thermal properties, with the difference in 10% loss of temperature being ΔT10 = 234 °C. A friction test conducted using a reciprocating tribometer showed that the friction of a glass ball/DN ion gel was relatively higher than that of a glass ball/DN hydrogel. Because the minimum coefficient of friction (COF) value increased after substitution, the increase in polymer adhesion caused by the electrostatic shielding of the surface moieties of glass and poly 2-acrylamidomethylpropanesulfonic acid (PAMPS) was considered the main contributor to the high friction. As the COF value decreased with increasing temperature, the DN ion gel can achieve low friction via the restriction of polymer adhesion at high temperatures, which is difficult in the DN hydrogel owing to drying.

High performance graphene oxide/epoxy nanocomposites fabricated through the solvent exchange method

In this study, a new simple solvent exchange method was employed to fabricate graphene oxide (GO)/epoxy nanocomposites. The structure and morphology of GO nanoplatelets and nanocomposites were extensively characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Examining the mechanical properties of nanocomposites indicates that the incorporation of only 0.05 phr GO into the epoxy resin increases the tensile modulus, tensile strength, and elongation at break by 7.2%, 10.1%, and 34.5%, respectively, as compared with the neat epoxy. Dynamic mechanical thermal analysis (DMTA) results indicate that the storage modulus (E') shows a similar trend to the tensile modulus and the glass transition temperature (Tg) of the epoxy significantly drops from 57.2° C to 47.9° C with the incorporation of 0.05 phr GO and then slightly increased with the further addition of GO. In addition, based on fracture toughness results, a remarkable improvement in the critical stress intensity factor (K1C) and critical strain energy release rate (G1C) was observed. Moreover, a detailed analysis of the toughening mechanism of the nanocomposites was carried out using SEM tests on the fracture surfaces. POLYM. COMPOS., 39:E2497–E2505, 2018. © 2018 Society of Plastics Engineers

One-pot solvent exchange preparation of non-swellable, thermoplastic, stretchable and adhesive supramolecular hydrogels based on dual synergistic physical crosslinking

With their unique properties of self-healing and viscoelasticity, physically crosslinked supramolecular hydrogels are promising materials for soft robotics, wearable electronics and biomedical applications. However, the weak mechanical properties of supramolecular hydrogels, especially those prepared with natural polymers, limit their wide-spread application, and swelling is one of the key factors that contributes to the weakening of hydrogels. Herein, we utilize a simple one-pot solvent exchange method to prepare non-swellable, thermoplastic and tough supramolecular gelatin hydrogels based on two synergistic physical crosslinkings, namely, the self-assembled tri-helix structure of gelatin and the hydrophobic aggregation of gelatin-grafted and free hydrophobic motifs. The obtained hydrogels possess a stable water content above 70% with extended incubation in water. These hydrogels are highly malleable upon heating but are extremely stretchable and tough after cooling to room temperature. Furthermore, the supramolecular gelatin hydrogels exhibit robust adhesion to various material surfaces and minimal cytotoxicity.

Injectable Macroporous Ferrogel Microbeads with a High Structural Stability for Magnetically Actuated Drug Delivery.

Macroporous hydrogels are an attractive material platform that can provide shortened interfacial diffusion pathways and high biomacromolecule loading. Recently, macroporous ferrogels have shown high potential for use in the on-demand delivery of bioactive molecules, resulting from their reversible and large volumetric deformation upon magnetic stimulation. However, these macroporous ferrogels require surgical placement in the body due to their large size; an injectable form of macroporous ferrogels has not yet been reported. In this study, injectable macroporous ferrogel microbeads loaded with iron oxide nanoparticles have been prepared on the basis of alginate microbeads for on-demand drug release. A simple solvent exchange and subsequent covalent cross-linking of the alginate chains in hydrogel microbeads induced a high polymer density on the hydrogel network and led to enhanced mechanical properties even after the generation of macropores in the microbeads. The macroporous ferrogel microbeads exhibited good mechanical stability and were stable during needle injection. The increased loading of large biomolecules due to the macroporosity of the microbeads and their large reversible volumetric deformation response to the external magnetic field enabled their potential for use in the on-demand delivery of drugs of assorted sizes by magnetic actuation. As a result of their structural stability, injectable size, and ability for on-demand drug delivery, ferrogel microbeads have promising potential for application in many biomedical fields.