Weak Solvent Research Articles

Influence of Self-Assembly and Solvent Polarity on Fluorescence Properties of Hydrophobic Organic Cations Based on Anthracene Skeleton

Fluorescence mode is influenced by the substituents, the polarity of the solvent, the steric factor and even the aggregation state of molecules in solvent under the testing environment. By comparing the fluorescent behavior of three anthracene derivatives, we observe that the hydrophobic interaction and steric effect in structures reduce fluorescence intensity, quantum yield and fluorescence lifetime. The emitting mode of two amphiphilic salts changes from aggregation emission in weak polar solvent to monomer emission in strong polar solvent and gives the similar variety in mixed solvent.

3D Graphene-Oil Absorbent Resin Hybrid Gel as High Efficiency Oil Absorbent Material

A new type of high oil absorbent resin (OAR) was synthesized by emulsion polymerization with lauryl methacrylate (LMA) and butyl methacrylate (BMA) as soft monomers, and methyl methacrylate (MMA) as hard monomer. A graphene-oil absorbent resin hybrid aerogel (G-OAR aerogel) was therefore prepared through the hydrothermal reduction of graphene oxide colloidal solution and the oil absorbent resin emulsion. The self-assembly characteristics of graphene oxide in hydrothermal treatment resulted in the formation of 3D porous structure for G-OAR aerogel. The component, morphology and hydrophobicity of G-OAR aerogel were characterized by FTIR, XRD, SEM and contact angle, and its absorption capacities to different kinds of organic solvents and oils were also been investigated. The results indicate that the absorption capacities of G-OAR aerogel reach up to 40-50 g/g for low density organic solvents, like acetone, anhydrous alcohol, cyclohexane, toluene, ethyl acetate and diesel. The absorption capacities are 80-90 g/g for high density and weak polarity organic solvents, like phenixin and castor oil. The good oil absorption property makes it show high potential in the application of wastewater treatment and oil leakage.

Scalable Synthesis of Positively Charged Sequence-Defined Functional Polymers.

Synthesizing and characterizing sequence-defined polymers with positively charged backbone are great challenges. By alternately processing Menschutkin reaction and Cu-catalyzed azide-alkyne cycloaddition reaction, we successfully synthesized series of scalable cationic sequence-defined polymers with quaternary ammonium backbone up to 12 repeating units and characterized their precise structures. Due to the dramatic polarity difference between weak polar feed molecules and strong polar target molecules, simple precipitation in weak polar solvents is enough to obtain pure sequence-defined polymers. Such a polar-inverse strategy (PIS), without protecting groups and solid support, offers extremely high yields up to 68% after 12 reaction steps (i.e., average yield >95% for each step), favoring cost-effective large-scale production. Because of the independent reactivity of selected functional groups, the cationic sequence-defined polymers are highly programmable, including backbone composition, sequence order, functional side groups, terminal groups and topological structure. Sequence information decoding is easily achieved according to Maldi-Tof mass spectrum without retrospecting its synthetic history, resulting in a great superiority in the field of information transmitting and reading. The resulting multifunctional sequence-defined polymers are water-soluble and positively charged, opening the avenue to bioapplications such as condensing DNA, gene transfection and drug delivery.

Solvent-Dependent Oxidizing Power of LiI Redox Couples for Li-O2 Batteries

Summary Li-O2 batteries offer higher gravimetric energy density than commercial Li-ion batteries. Despite this promise, catalyzing oxidation of discharge products, Li2O2 and LiOH, during charging remains an obstacle to improved cycle life and round-trip efficiency. In this work, reactions between LiI, a soluble redox mediator added to catalyze the charging process, and Li2O2 and LiOH are systematically investigated. We show that stronger solvation of Li+ and I− ions led to an increase in the oxidizing power of I3−, which allowed I3− to oxidize Li2O2 and LiOH in DMA, DMSO, and Me-Im, whereas in weaker solvents (G4, DME), the more oxidizing I2 was needed before a reaction could occur. We observed that Li2O2 was oxidized to O2, whereas LiOH reacts to form IO−, which could either disproportionate to LiIO3 or attack solvent molecules. This work clarifies significant misconceptions in these reactions and provides a thermodynamic and selectivity framework for understanding the role of LiI in Li-O2 batteries.

β-Cyclodextrin⁻Hyaluronic Acid Polymer Functionalized Magnetic Graphene Oxide Nanocomposites for Targeted Photo-Chemotherapy of Tumor Cells.

A multifunctional targeted drug delivery platform (CDHA–MGO) has been successfully constructed by grafting β-cyclodextrin–hyaluronic acid polymers (CDHA) to Fe3O4–graphene oxide (MGO). The obtained CDHA–MGO nanocomposite has good water-dispersibility, easy magnetic separation, high near-infrared (NIR) photothermal heating, and excellent biocompatibility. The β-cyclodextrin-hyaluronic acid polymers efficaciously enhance the doxorubicin (DOX) loading amount up to 485.43 mg·g−1. Meanwhile, the Fe3O4–graphene oxide provides a facile photothermal response mechanism to handle the NIR-triggered release of DOX in weak acidic solvent environments. Significantly, the DOX-loaded nanocomposite (DOX@CDHA–MGO) has displayed CD44 receptor-mediated active targeting recognition and chemo-photothermal synergistic therapy of hepatoma cells. These findings suggest that the as-prepared drug delivery platform would be of valuable potential for cancer-targeted photo-chemotherapy.

Controlled synthesis and photostability of blue emitting Cs3Bi2Br9 perovskite nanocrystals by employing weak polar solvents at room temperature

All inorganic Cs3Bi2Br9 perovskite NCs were synthesized at room temperature, demonstrating blue dual-emission peaks and high photoluminescence quantum yield.

Effect of Different Additives on Separation Performance of Flat Sheet PVDF Membrane Contactor

This paper investigates effects of different additives on morphology and subsequently, separation performance of asymmetric flat sheet Polyvinylidene fluoride (PVDF) membranes to separate CO2 using membrane contractor. Five different additives from different chemical families including Lithium chloride (salt), Polyethylene glycol 400 (polymer), glycerol (weak anti-solvents), methanol (alcohols) and acetic acid (weak secondary solvents) were used for controlling the morphology of the fabricated membranes. The fabricated PVDF membranes were applied to separate CO2 from a gas mixture of (20/80 wt/wt) CO2/N2 by contacting with (20/80 wt/wt) Monoethanolamine/H2O as absorbent. The investigations revealed that among the all considered additives, glycerol has the most promising effect on the performance of CO2 separation from the feed gas mixture. Effects of operational parameters such as flow rate and temperature of absorbents on the separation performance were also studied. Investigations showed that the lowest level of temperature (30 oC) and the highest level of the flow rate of absorbent (500 ) provide better separation performance. Additionally, the presence of glycerol increased absorption performance (η) from 0.63 to 0.78 (at the lowest level of flow rate) and from 0.79 to 0.91 (at the highest level of flow rate) compared to the bare PVDF membranes.

Fabrication of PVDF hollow fiber membranes via integrated phase separation for membrane distillation

Abstract In this study, polyvinylidene fluoride (PVDF) hollow fibers with interpenetrating network morphologies were fabricated via complex thermally induced phase separation (c-TIPS) by integration of non-solvent induced phase separation (NIPS) and thermally induced phase separation (TIPS) at 80 °C and then tested in membrane distillation (MD). The effects of solvents, additive and bore fluid on the membrane morphology, pore structure and MD performance were investigated. Direct-contact membrane distillation (DCMD) for desalination was carried out to evaluate membrane permeability and salt rejection. Using a weak solvent like triethylphosphate (TEP) and weak bore fluid like polyethylene glycol (PEG-200) in the c-TIPS favors the formation of an interpenetrating network morphology. In addition, PEG-200 increased the roughness and water contact angle of the inner skin. The hollow fibers fabricated via the c-TIPS at low temperature presented high permeability, mechanical strength and long-term stability. In desalination of formulated seawater, a distillate flux of 61.6 kg/m2h with NaCl rejection of 99.99% was achieved at feed temperature of 71 °C.

Preparation and analytical application of novel thiol-functionalized solid extraction matrices: From mesoporous silica to hybrid monolithic capillary column

A comprehensively comparative study of thiol-functionalized mesoporous silica and organic-inorganic hybrid monolithic column was reported, aiming at the separation and enrichment of inorganic arsenic. Thiol-functionalized mesoporous silica was synthesized based on the one-step co-condensation method. At the same time, a novel thiol-functionalized organic-inorganic hybrid monolithic column was synthesized using an unconventional ternary weak basic solvent system via one-step sol-gel process. The approach to prepare monolithic column through mild condition remarkably improved delamination phenomenon of thiol-functionalized hybrid monolithic column easily caused by conventional methods. As(III) can be selectively uptaken by the hybrid monolithic column and homemade syringe-based solid phase extraction device containing mesoporous silica through chelation in a wide range of pH, while As(V) cannot, and then the captured As(III) was eluted by 3% HNO3 (v/v) with 0.01 mol L−1 KIO3. Under the optimized conditions, the extraction recoveries were 91–102% and 93–103% for mesoporous silica and monolithic column, respectively. Although both two materials were ideal solid matrices for the removal and speciation analysis of As(III) in environmental waters, the monolith-based solid phase microextration protocol was more fast and reagent-saving than the other, which endued monolithic columns with more application prospects for trace elemental analysis and speciation. Even so, the exploration of mesoporous silica could efficiently pilot the synthesis of monolithic columns.

Nucleophilic Substitution in Solution: Activation Strain Analysis of Weak and Strong Solvent Effects.

We have quantum chemically studied the effect of various polar and apolar solvents on the shape of the potential energy surface (PES) of a diverse collection of archetypal nucleophilic substitution reactions at carbon, silicon, phosphorus, and arsenic by using density functional theory at the OLYP/TZ2P level. In the gas phase, all our model SN2 reactions have single‐well PESs, except for the nucleophilic substitution reaction at carbon (SN2@C), which has a double‐well energy profile. The presence of the solvent can have a significant effect on the shape of the PES and, thus, on the nature of the SN2 process. Solvation energies, charges on the nucleophile or leaving group, and structural features are compared for the various SN2 reactions in a spectrum of solvents. We demonstrate how solvation can change the shape of the PES, depending not only on the polarity of the solvent, but also on how the charge is distributed over the interacting molecular moieties during different stages of the reaction. In the case of a nucleophilic substitution at three‐coordinate phosphorus, the reaction can be made to proceed through a single‐well [no transition state (TS)], bimodal barrier (two TSs), and then through a unimodal transition state (one TS) simply by increasing the polarity of the solvent.

Morphology and performance of poly(vinylidene fluoride) flat sheet membranes: Thermodynamic and kinetic aspects

ABSTRACTIn this study, poly(vinylidene fluoride) (PVDF) membranes were prepared using two different solvents with various polymer concentrations to investigate the predominant kinetic or thermodynamic aspects of membrane preparation in a phase separation process. For this purpose, dimethyl sulfoxide (DMSO) as a weak solvent and N‐2‐methylpyrrolidone (NMP) as a strong solvent were used with polymer concentrations between 8 and 15 wt %. Scanning electron microscopy and water content, contact angle, and pore size measurements were used to assess the factors affecting the physicochemical properties of the prepared membranes. The results showed that in the case of NMP, the membrane structure is mainly controlled by thermodynamic parameters, while when using DMSO, kinetic parameters are predominant. According to the results, the prepared PVDF‐based membranes with DMSO exhibited a relatively denser top layer and less permeation compared to the NMP/PVDF membranes. The difference between the viscosities of the casting solutions with equal polymer concentrations in DMSO and NMP was considered to be the main effective factor in solvent/nonsolvent exchange, resulting in denser top layers in the DMSO/PVDF membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46419.

Mechanistic insights into the selective hydrogenation of resorcinol to 1,3-cyclohexanedione over Pd/rGO catalyst through DFT calculation

In our previous work, graphene-supported Pd catalyst (Pd/rGO) exhibited higher activity and selectivity for the liquid phase selective hydrogenation of resorcinol to 1,3-cyclohexanedione compared with other catalysts. In the present study, further experimental and theoretical investigations were conducted to reveal the reaction mechanism and the catalytic mechanism of Pd/rGO for resorcinol hydrogenation. The effects of graphene nanosheet and the solvent on the reaction were investigated, and the pathway for resorcinol hydrogenation was proposed supported by density functional theory (DFT) calculations. The results showed that the excellent selectivity of Pd/rGO to 1,3-cyclohexanedione was attributed to the strong π–π and p–π interactions between the graphene nanosheet and the benzene ring as well as hydroxyl in resorcinol molecule, which was in agreement with our previous speculation. In weak polar aprotic solvents, solvation free energy had less impact to the π–π and p–π interactions mentioned above. In strong polar aprotic solvents and polar protic solvents, however, the influence of solvation free energy was much greater, which led to the decrease in the conversion of resorcinol and the selectivity to 1,3-cyclohexanedione.

Coordinated Responsive Arrays of Surface-Linked Polymer Islands-CORALs.

The concept of co-ordinated responsive arrays of surface-linked islands (polymer CORALs) is introduced. This study targets a responsive system capable of revealing or covering the substrate surface in response to environmental changes in a reversible way. A convenient method of fabrication of polymer CORALs is proposed. It is based on microphase separation that occurs in thin films of supramolecular assemblies of block copolymers with reactive blocks. Such blocks form nanometer-size domains that may serve as anchors for surface-linked polymer islands. Two characteristics of the islands are critically important for the switching function: high grafting density within the islands and small lateral separation that allows interactions between polymer chains grafted to the neighboring islands. This combination permits complete coverage of the substrate surface upon exposure to a good solvent (relaxed state). In a weak solvent, the chains collapse within the islands, thus revealing the substrate (compact state). The morphology of the CORALs in both states and some details of the switching process were studied with atomic force microscopy, grazing incidence small-angle scattering, and coarse-grained molecular dynamic simulations.

Selenium and selenium species in feeds and muscle tissue of Atlantic salmon

Selenium (Se) is an essential element for animals, including fish. Due to changes in feed composition for Atlantic salmon (Salmo salar), it may be necessary to supplement feeds with Se. In the present work, the transfer of Se and Se species from feed to muscle of Atlantic salmon fed Se supplemented diets was studied. Salmon were fed basal fish feed (0.35 mg Se/kg and 0.89 mg Se/kg feed), or feed supplemented either with selenised yeast or sodium selenite, at low (1–2 mg Se/kg feed) and high (15 mg Se/kg feed) levels, for 12 weeks. For the extraction of Se species from fish muscle, enzymatic cleavage with protease type XIV was applied. The extraction methods for Se species from fish feed were optimised, and two separate extraction procedures were applied, 1) enzymatic cleavage for organic Se supplemented feeds and 2) weak alkaline solvent for inorganic Se supplemented feeds, respectively. For selenium speciation analysis in feed and muscle tissue anion-exchange HPLC-ICP-MS for analysis of inorganic Se species and cation-exchange HPLC-ICP-MS for analysis of organic Se species, were applied. In addition, reversed phase HPLC-ICP-MS was applied for analysis of selenocysteine (SeCys) in selected muscle samples. The results demonstrated that supplemented Se (organic and inorganic) accumulated in muscle of Atlantic salmon, and a higher retention of Se was seen in the muscle of salmon fed organic Se diets. Selenomethionine (SeMet) was the major Se species in salmon fed basal diets and diets supplemented with organic Se, accounting for 91–118% of the total Se. In contrast, for muscle of salmon fed high inorganic Se diet, SeMet accounted for 30% of the total Se peaks detected. Several unidentified Se peaks were detected, in the fish fed high inorganic diet, and analysis showed indicated SeCys is a minor Se species present in this fish muscle tissue.

Effects of Sodium Carbonate Additive on the Hydroliquefaction of a Sub-bituminous Coal with Fe-Based Catalyst under Mild Conditions

In this paper, the influence of Na2CO3 (NC) on the hydroliquefaction performances of Hongliulin (HLL) coal with an Fe-based catalyst, γ-FeOOH (FC), under mild conditions was investigated, and the properties of the resulting preasphaltene and asphaltene were examined. Results show that the addition of NC to FC-catalyzed liquefaction significantly promoted coal conversion and oil production and reduced water production under mild conditions, especially at high initial H2 pressure. The H2 consumption of mild liquefaction (0.53–1.93%) is much smaller than that of the traditional liquefaction processes, and the addition of NC to FC can enhance H2 consumption, especially the runs with weak hydrogen donor solvents. The addition order of NC and FC is an important factor which can affect the activity of FC and NC binary catalysts. There exists a prominent synergistic effect between NC and FC in HLL coal hydroliquefaction, and the synergistic effect could be ascribed to the combined promotion actions of NC for the ...

Retention Models on Core-Shell Columns.

A thin, active shell layer on core-shell columns provides high efficiency in HPLC at moderately high pressures. We revisited three models of mobile phase effects on retention for core-shell columns in mixed aqueous-organic mobile phases: linear solvent strength and Snyder-Soczewiński two-parameter models and a three-parameter model. For some compounds, two-parameter models show minor deviations from linearity due to neglect of possible minor retention in pure weak solvent, which is compensated for in the three-parameter model, which does not explicitly assume either the adsorption or the partition retention mechanism in normal- or reversed-phase systems. The model retention equation can be formulated as a function of solute retention factors of nonionic compounds in pure organic solvent and in pure water (or aqueous buffer) and of the volume fraction of an either aqueous or organic solvent component in a two-component mobile phase. With core-shell columns, the impervious solid core does not participate in the retention process. Hence, the thermodynamic retention factors, defined as the ratio of the mass of the analyte mass contained in the stationary phase to its mass in the mobile phase in the column, should not include the particle core volume. The values of the thermodynamic factors are lower than the retention factors determined using a convention including the inert core in the stationary phase. However, both conventions produce correct results if consistently used to predict the effects of changing mobile phase composition on retention. We compared three types of core-shell columns with C18-, phenyl-hexyl-, and biphenyl-bonded phases. The core-shell columns with phenyl-hexyl- and biphenyl-bonded ligands provided lower errors in two-parameter model predictions for alkylbenzenes, phenolic acids, and flavonoid compounds in comparison with C18-bonded ligands.

Active Solvent Modulation: A Valve-Based Approach To Improve Separation Compatibility in Two-Dimensional Liquid Chromatography.

Two-dimensional liquid chromatography (2D-LC) is increasingly being viewed as a viable tool for solving difficult separation problems, ranging from targeted separations of structurally similar molecules to untargeted separations of highly complex mixtures. In spite of this performance potential, though, many users find method development challenging and most frequently cite the "incompatibility" between the solvent systems used in the first and second dimensions as a major obstacle. This solvent strength related incompatibility can lead to severe peak distortion and loss of resolution and sensitivity in the second dimension. In this paper, we describe a novel approach to address the incompatibility problem, which we refer to as Active Solvent Modulation (ASM). This valve-based approach enables dilution of 1D effluent with weak solvent prior to transfer to the 2D column but without the need for additional instrument hardware. ASM is related to the concept we refer to as Fixed Solvent Modulation (FSM), with the important difference being that ASM allows toggling of the diluent stream during each 2D separation cycle. In this work, we show that ASM eliminates the major drawbacks of FSM including complex elution solvent profiles, baseline disturbances, and slow 2D re-equilibration and demonstrate improvements in 2D separation quality using both simple small molecule probes and degradants of heat-treated bovine insulin as case studies. We believe that ASM will significantly ease method development for 2D-LC, providing a path to practical methods that involve both highly complementary 1D and 2D separations and sensitive detection.

Synthesis, characterization, electrochemical behavior and electrocatalytical properties towards nitrate and iodate by alcohol solvated Keggin-type polyoxometalate: The effects of weak intermolecular interactions and solvent on electrocatalytical activity

An alcohol solvated polyoxometalate, [NH4]4[SiW12O40]·3C2H5OH (1), has been synthesized and characterized by infrared spectrum, single-crystal X-ray diffraction and elemental analysis. The X-ray crystallographic study of 1 showed that it was crystallized in trigonal space group R-3m and polyanions was associated with the NH4+ counterions by coulombic forces and supramolecular interactions. Complex 1 was further connected and formed a three-dimensional framework through alcohol (OH⋯OPOM) and other weak interactions (NH⋯OPOM and OH⋯NNH4+). From three types of NH4+, only N1 showed hydrogen bonding. The redox waves of W-O framework of 1 was pH-dependent. The tungsten-centered waves of this compound showed a classical potential shift as a function of acidity at pH=1.5–3.5. The electrocatalysis behaviors of this compound towards the reduction of nitrite and iodate ions have been studied in details. The electrocatalytic reduction of NO2− and IO3− by the modified carbon paste electrode (CPE) of 1 in various buffer solutions showed an electrocatalytic reduction activity of NO2−>IO3−.

A systematic investigation of sample diluents in modern supercritical fluid chromatography

This paper focuses on the possibility to inject large volumes (up to 10μL) in ultra-high performance supercritical fluid chromatography (UHPSFC) under generic gradient conditions. Several injection and method parameters have been individually evaluated (i.e. analyte concentration, injection volume, initial percentage of co-solvent in the gradient, nature of the weak needle wash solvent, nature of the sample diluent, nature of the column and of the analyte). The most critical parameters were further investigated using in a multivariate approach. The overall results suggested that several aprotic solvents including methyl tert-butyl ether (MTBE), dichloromethane, acetonitrile or cyclopentyl methyl ether (CPME) were well adapted for the injection of large volume in UHPSFC, while MeOH was generally the worst alternative. However, the nature of the stationary phase also had a strong impact and some of these diluents did not perform equally on each column. This was due to the existence of a competition in the adsorption of the analyte and the diluent on the stationary phase. This observation introduced the idea that the sample diluent should not only be chosen according to the analyte but also to the column chemistry to limit the interactions between the diluent and the ligands. Other important characteristics of the “ideal” SFC sample diluent were finally highlighted. Aprotic solvents with low viscosity are preferable to avoid strong solvent effects and viscous fingering, respectively. In the end, the authors suggest that the choice of the sample diluent should be part of the method development, as a function of the analyte and the selected stationary phase.

Controlling Morphology and Aggregation in Semiconducting Polymers: The Role of Solvents on Lasing Emission in Poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene

Systematic experiments were performed to investigate solvent-dependent morphology and aggregation of the semiconducting polymer film poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV), which was span-cast from nonaromatic strong polarity solvents tetrahydrofuran (THF), trichloromethane (TCM) and aromatic weak polarity solvents chlorobenzene (CB), toluene, and p-xylene. The results indicated that the conformation of the spin-cast MEH-PPV films with weak aggregation such as THF and TCM demonstrated excellent lasing emission performances because of inhibiting the fluorescence quenching induced by bi-molecule process. The Atomic Force Microscope (AFM) images confirmed the distinct morphologies of the spin-cast MEH-PPV films. The amplified spontaneous emission (ASE) was investigated in a simple asymmetric slab planar waveguide structure by methods of variable stripe length (VSL) and shifting excitation stripe (SES). The amplified spontaneous emission (ASE) experiments confirmed the distinct polymer chain conformation. The conformation, which preserved from the spin-cast process, indicated the distinct interactions between solvents and MEH-PPV polymer chains. The pure film spectra were performed to confirm the effect of distinct conformation on the material energy level. This work provides insights into the morphology and aggregation effect of the spin-cast polymer films on the performances of lasers.