Single Solvent System Research Articles

Low‐Viscosity γ‐Butyrolactone‐Based Concentrated Electrolyte Solutions for LiNi0.5Mn1.5O4 Positive Electrodes in Lithium‐Ion Batteries

AbstractHighly concentrated electrolyte solution with a low viscosity and high stability against oxidation was obtained by using a single solvent system of LiBF4/γ‐butyrolactone (GBL). Although up to 4.65 mol kg−1 LiBF4 could be dissolved in GBL at room temperature, 3.87 mol kg−1 LiBF4/GBL was a reasonable compromise to attain a low viscosity (52.1 mPa s) and a low GBL/Li molar ratio (3.00). Sodium carboxymethylcellulose and poly(acrylic acid) were used as binders for the spinel LiNi0.5Mn1.5O4 positive electrode and the graphite negative electrode, respectively, to suppress the swelling of conventional poly(vinylidene fluoride)‐based binder. The charge and discharge performances of the LiNi0.5Mn1.5O4 positive electrode and the graphite negative electrode were improved by using 3.87 mol kg−1 LiBF4/GBL, as compared with concentrated propylene carbonate‐based electrolyte solution.

Electrospun polyurethane nanofiber scaffolds with ciprofloxacin oligomer versus free ciprofloxacin: Effect on drug release and cell attachment

An electrospun degradable polycarbonate urethane (PCNU) nanofiber scaffold loaded with antibiotic was investigated in terms of antibacterial efficacy and cell compatibility for potential use in gingival tissue engineering. Antimicrobial oligomer (AO), a compound which consists of two molecules of ciprofloxacin (CF) covalently bound via hydrolysable linkages to triethylene glycol (TEG), was incorporated via a one-step blend electrospinning process using a single solvent system at 7 and 15% w/w equivalent CF with respect to the PCNU. The oligomeric form of the drug was used to overcome the challenge of drug aggregation and burst release when antibiotics are incorporated as free drug. Electrospinning parameters were optimized to obtain scaffolds with similar alignment and fiber diameter to non-drug loaded fibers. AO that diffused from the fibers was hydrolysed to release CF slowly and in a linear manner over the duration of the study, whereas scaffolds with CF at the same concentration but in free form showed a burst release within 1h with no further release throughout the study duration. Human gingival fibroblast (HGF) adhesion and spreading was dependent on the concentration and form the CF was loaded (AO vs. free CF), which was attributed in part to differences in scaffold surface chemistry. Surface segregation of AO was quantified using surface-resolved X-ray photoelectron spectroscopy (XPS). These findings are encouraging and support further investigation for the use of AO as a means of attenuating the rapid release of drug loaded into nanofibers. The study also demonstrates through quantitative measures that drug additives have the potential to surface-locate without phase separating from the fibers, leading to fast dissolution and differential fibroblast cell attachment.

Development of validated high-performance thin layer chromatography for quantification of aristolochic acid in different species of the Aristolochiaceae family

This study was undertaken to isolate and quantify aristolochic acid in Aristolochia indica stem and Apama siliquosa root. Aristolochic acid is an important biomarker component present in the Aristolochiaceae family. The isolation method involved simple solvent extraction, precipitation and further purification, using recrystallization. The structure of the compound was confirmed using infrared spectroscopy, mass spectrometry and nuclear magnetic resonance. A specific and rapid high-performance thin layer chromatography (HPTLC) method was developed for analysis of aristolochic acid. The method involved separation on the silica gel 60 F254 plates using the single solvent system of n-hexane: chloroform: methanol. The method showed good linear relationship in the range 0.4–2.0 μg/spot with r2 = 0.998. The limit of detection and limit of quantification were 62.841 ng/spot and 209.47 ng/spot, respectively. The proposed validated HPTLC method was found to be an easy to use, accurate and convenient method that could be successfully used for standardization and quality assessment of herbal material as well as formulations containing different species of the Aristolochiaceae family.

Comparative analysis of different bioactivities of Curcuma longa, Nigella sativa seeds, and Camellia sinensis extracted by four different methods: A green way to reduce oxidative stress.

Medicinal use of plants is as old as human history. Curcuma longa, Nigella sativa seeds, and Camellia sinensis have been widely used in various remedies since ages. In this study, the effect of extraction method on different bioactivities and phytochemical constituents of Curcuma longa, Nigella sativa seeds, and Camellia sinensis were evaluated and compared using single solvent system (50% ethanol). Plant extracts were prepared by percolation-assisted extraction, sonication-assisted extraction, microwave-assisted extraction, and polyphenol extraction. Following phytochemical screening, extracts were screened for antioxidant activity, antihemolytic activity, osmotic tolerance, and osmotic fragility. All plant extracts showed good phytochemical content irrespective of extraction method. However, activities in vitro antioxidant assays were dependent on plant as well as on extraction methods. Promising results were observed for antihemolytic activity against hydrogen peroxide-treated erythrocytes. Overall, Camellia sinensis exhibited the highest bioactivities followed by Curcuma longa and Nigella sativa seeds.

Electrospun preparation of polylactic acid nanoporous fiber membranes via thermal-nonsolvent induced phase separation

A novel polylactic acid (PLLA) fiber membrane with nanoporous structures has been successfully developed via thermal-nonsolvent induced a phase separation technique by electrospinning a single solvent system of PLLA/dichloromethane. A water bath receiver was necessary for preparing the nanoporous fiber membranes in this paper. The results showed that the nanoporous fiber membranes could be obtained within a wide range of humidity. Compared with non-porous PLLA fiber membranes, the nanoporous fiber membranes displayed significantly improved specific surface area (improved about 20%) and rejection ratio (about 3 times) toward methylene blue. Besides, the PLLA nanoporous fiber membranes showed a water flux up to 4836.6 L m−2 h−1, increased by 25% than that of the non-porous fiber membranes. In addition, the oil adsorption capacity of the PLLA nanoporous fiber membranes could reach 26.8 g g−1. The new developed PLLA nanoporous fiber membranes via thermal-nonsolvent induced phase separation technique would demonstrate an impressive prospect for oil adsorption and organic dye filtration.

Highly efficient chromium(VI) adsorption with nanofibrous filter paper prepared through electrospinning chitosan/polymethylmethacrylate composite

Chitosan/polymethylmethacrylate (PMMA) composite nanofibrous membrane was prepared by electrospinning technique with a single solvent system. Characterization with Fourier transformation infrared spectroscopy (FT-IR) indicated that there was weak interaction (such as hydrogen bonds) between PMMA and chitosan. Scanning electron microscopy (SEM) measurements illustrated that the average diameter of the composite nanofibers decreased as the chitosan content was increased, while the number of nano/micrometer sized beads increased in the membrane. The composite nanofibrous membrane with chitosan:PMMA ratio of 0.3:1.0 exhibited a maximum adsorption capacity (67.0mgg−1) of Cr(VI) in static adsorption, which was nearly three times higher than that of chitosan powder (22.9mgg−1). The adsorption capacity of Cr(VI) via filtration became even higher, where the maximum value was 92.5mgg−1 at pH 3.0. Notably, most of Cr(VI) has been removed after the first filtration at all pH values (2.0–6.0) investigated in this report. The adsorption capacity of the composite nanofibrous membrane decreased slightly (17.1%) after three filtration cycles even with the solution of pH 2.0, which shall be attributed to the enhanced mechanical strength and acid fastness of the composite membrane. X-ray photoelectron spectroscopy (XPS) analysis indicated that amino groups played an important role in the adsorption of Cr(VI).

Excellent low temperature performance electrolyte of spiro-(1,1′)-bipyrrolidinium tetrafluoroborate by tunable mixtures solvents for electric double layer capacitor

ABSTRACT This paper was addressed on studying the electrolyte for electrochemical double layer capacitors with relatively high ionic conductivity and high electrochemical stability for low temperature application. The data of systematical analysis of the electrochemical characteristics of EDLC have been presented using spiro-(1,1′)-bipyrrolidinium tetrafluoroborate (SBP-BF 4 ) with 1.5 mol L −1 (M) in a variety of solvent compositions including propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), while the mixture solvents are PC+DMC (1:1 in volume) and PC+DMC+EC (1:1:1 in volume). The physical properties and electrochemical performance of SBP-BF 4 in all solvent compositions are investigated. It is found that the binary solvent electrolyte systems exhibited better characteristics in electrochemical performance than single and ternary solvent system in low temperature. The capacitance of the binary solvent electrolyte systems could reach about 117.3 F g −1 at 20 °C and 92.3 F g −1 at −50 °C, which were higher than that of single and ternary solvent system. The energy density and power density of EDLCs based on binary solvents systems are can reach 29.6 Wh kg −1 and 12.5 kW kg −1 , respectively.

Numerous single‐layer graphene sheets prepared from natural graphite by non‐chemical liquid‐phase exfoliation

A simple method was used to produce a high concentration of single-layer graphene sheets in a single organic solvent system, without using any surfactants. In this experiment, the concentration of single-layer graphene sheets dispersed in solution increased as the sonication time increased, but damage occurred after performing sonication for 120 min. The concentration of single-layer graphene sheets was 0.915 mg/ml after sonication for 60 min. According to a transmission electron microscope image, the length of the single-layer graphene sheets was ∼2–3 μm, and the width was 0.5–1 μm. The perfect single-layer graphene sheets and the defective single-layer graphene sheets were distinguished using selected-area electron diffraction. X-ray diffraction determined that the two-theta angle of the numerous single-layer graphene sheets on a (002) plane was 25.57°, but the ‘one layer’ graphene sheets produced no peak along the (002) plane. According to the Raman spectra, the ratio of ID /IG was 0.3, which indicated that the graphene sheets contained few defects.

Extraction of Indigo dye from Couroupita guianensisand its application on cotton fabric

AbstractCouroupita guianensis (Cannon ball tree) flowers and fruits are known to contain indigotin and indirubin. In this study an attempt is made to optimize the period for effective extraction of indigo from Couroupita guianensis fruit and application of the crude extract on the cotton fabric. Fermentation of the Couroupita guianensis fruit pulp for 5 days gave intense bluer pigment and hence was selected as the optimum period for fermentation. Major colouring components from Couroupita guianensis fruit extract were separated by thin layer chromatography using single solvent system, chloroform; which gives three pigments, violet, blue and pink with the Rf values of 0.88, 0.57, and 0.25 respectively. The Rf values, the wavelength of maximum absorption from UV-Visible spectroscopy, Fourier Transform Infrared (FTIR) spectrum and 1H Nuclear magnetic resonance (1H NMR) spectrum of blue pigment matched with that of synthetic indigo standard and that of the pink pigment matched with reported values of indirubin which is an isomer of indigotin. The % purity of indigo dye was found to be 26.46%. Dyeing of cotton fabric was carried out with the crude dye powder which gave comparable fastness properties vis-a-vis synthetic indigo.

Endo vs Exo Bowl: Complexation of Xanthone by Pyrogallol[4]arenes

Cocrystal systems containing pyrogallol[4]arene, xanthone, and solvent molecules are examined and discussed. Three types of pyrogallol[4]arenes are cocrystallized with xanthone in isopropanol, acetonitrile, dimethyl sulfoxide, and a mixture of isopropanol and methanol. It is found that the solvent controls complexation of the xanthone molecule, whereas pyrogallol[4]arene tail length affects cocrystal packing. With a single-solvent system, the xanthone molecule is outside (exo) of the bowl of the pyrogallol[4]arene, but with a two-solvent system, the xanthone molecule is inside (endo) of the bowl of the pyrogallol[4]arene.

Comparison of ambient solvent extraction methods for the analysis of fatty acids in non-starch lipids of flour and starch

BACKGROUNDLipids are minor components of flours, but are major determinants of baking properties and end-product quality. To the best of our knowledge, there is no single solvent system currently known that efficiently extracts all non-starch lipids from all flours without the risk of chemical, mechanical or thermal damage. This paper compares nine ambient solvent systems (monophasic and biphasic) with varying polarities: Bligh and Dyer (BD); modified Bligh and Dyer using HCl (BDHCL); modified BD using NaCl (BDNaCl); methanol–chloroform–hexane (3:2:1, v/v); Hara and Radin (hexane–isopropanol, 3:2, v/v); water-saturated n-butanol; chloroform; methanol and hexane for their ability to extract total non-starch lipids (separated by lipid classes) from wheat flour (Triticum aestivum L.). Seven ambient extraction protocols were further compared for their ability to extract total non-starch lipids from three alternative samples: barley flour (Hordeum vulgare L.), maize starch (Zea mays L.) and tapioca starch (Manihot esculenta Crantz).RESULTSFor wheat flour the original BD method and those containing HCl or NaCl tended to extract the maximum lipid and a significant correlation between lipid extraction yield (especially the glycolipids and phospholipids) and the polarity of the solvent was observed. For the wider range of samples BD and BD HCl repeatedly offered the maximum extraction yield and using pooled standardized (by sample) data from all flours, total non-starch lipid extraction yield was positively correlated with solvent polarity (r = 0.5682, P < 0.05) and water ratio in the solvent mixture (r = 0.5299, P < 0.05).CONCLUSIONIn general, BD-based methods showed better extraction yields compared to methods without the addition of water and, most interestingly, there was much greater method dependence of lipid yields in the starches when compared to the flour samples, which is due to the differences in lipid profiles between the two sample types (flours and starches).

Fractionation and characterization of lignin from steam-exploded corn stalk by sequential dissolution in ethanol–water solvent

Due to the intricate process of traditional lignin fractionation by multi-organic solvent extraction, single solvent system consisted of ethanol and water was established in this work to fractionate and purify lignin from steam-exploded corn stalk. Three alkali-extracted lignin fractions (Fraction 1, 2 and 3) were obtained by sequential dissolution and subsequently characterized by the following analysis technologies: GPC, HPLC, UV, FTIR and 1H NMR spectra and thermogravimetric analysis. The GPC analysis showed the molecular weight of lignin fractions increased gradually from Fraction 1 to 3 and their polydispersity decreased dramatically compared with the unfractionated lignin. Besides, the purity of lignin Fraction 1 and 2 increased from 87.57% to 93.12% and 91.59% respectively due to the polysaccharide elimination effect of ethanol solutions. The subsequent characterization indicated that the content of phenolic acids decreased considerably from 3.379% to 0.095% with increasing molecular weight whereas the guaiacyl unit content and thermal stability increased. Meanwhile, the results of solubility determination revealed that the solubility of lignin enhanced when the molecular weight decreased and the water content of mixed solvent increased, which successfully elucidated the fractionation mechanism. Since ethanol is the only organic solvent used in the process, this study provides a relatively simple and efficient route to fractionate lignin from steam-exploded corn stalk for the subsequent utilization to produce stable and high-value lignin products.

State-of-the-art separation of ginsenosides from Korean white and red ginseng by countercurrent chromatography

Ginseng (Panax ginseng C. A. Meyer) has been one of the most popular herbs used for nutritional and medicinal purposes by the people of eastern Asia for thousands of years. Ginsenosides, the mostly widely studied chemical components of ginseng, are quite different depending on the processing method used. A number of studies demonstrate the countercurrent chromatography (CCC) separation of ginsenosides from several sources; however, there is no single report demonstrating a one-step separation of all of these ginsenosides from different sources. In the present study, we have successfully developed an efficient CCC separation methodology in which the flow-rate gradient technique was coupled with a new solvent gradient dilution strategy for the isolation of ginsenosides from Korean white (peeled off dried P. ginseng) and red ginseng (steam-treated P. ginseng). The crude samples were initially prepared by extraction with butanol and were further purified with CCC using solvent gradients composed of methylene chloride-methanol-isopropanol-water (different ratios, v/v). Gas chromatography coupled with flame ionization detector was used to analyze the components of the two-phase solvent mixture. Each phase solvent mixture was prepared without presaturation, which saves time and reduces the solvent consumption. Finally, 13 ginsenosides have been purified from red ginseng with the new technique, including Rg1, Re, Rf, Rg2, Rb1, Rb2, Rc, Rd, Rg3, Rk1, Rg5, Rg6, and F4. Meanwhile, eight ginsenosides have been purified from white ginseng, including Rg1, Re, Rf, Rh1, Rb1, Rb2, Rc, and Rd by using a single-solvent system. Thus, the present technique could be used for the purification of ginsenosides from all types' ginseng sources. To our knowledge, this is the first report involving the separation of ginsenoside Rg2 and Rg6 and the one-step separation of thirteen ginsenosides from red ginseng by CCC.

Hybrid nanofibrous mats with remarkable solvent and temperature resistance produced by electrospinning technique

A novel organic/inorganic hybrid copolymer poly[styrene-co-3-(trimethoxysilyl)propyl-methacrylate] [P(St-co-TMSPMA)] (denoted as PST) was successfully prepared from styrene and TMSPMA by free-radical polymerization. These composite fiber mats of PST were fabricated via a typical electrospinning process using a single solvent system. As shown in the SEM, the PST composite nanofibers have a smooth and uniform surface and the average diameter is about 0.2±0.04μm. After the methoxysilyl groups (SiOCH3) were hydrolyzed toward silanol groups (SiOH), the nanofibrous mats exhibited remarkable solvent and temperature resistance. On account of good chemical and thermal stability, this hybrid mats can provide a useful platform for developing functionalized mat systems.

Electrospinning PVDF/EC fibre from a binary solvent system

The influence of the composition of a binary component solvent on the surface morphology and diameter distribution of poly(vinylidene fluoride)/ethyl cellulose (PVDF/EC) fibres produced by electrospinning technology was investigated. Acetone (56°C) and N-methyl pyrrolidone (NMP) (203°C) binary solvent system was introduced and electrospinning was performed by changing the solution concentration, the applied voltage and the volume ratio of NMP/acetone. The results show that the morphology of PVDF/EC electrospun fibres is greatly influenced by the solution concentration and the volume ratio of NMP/acetone. PVDF/EC fibres prepared from NMP/acetone binary solvent system is much better than that prepared with a single component solvent system, and is very diverse with the volume ratios of the binary solvent system. The morphology of the fibres changed from beads (starting mass ratio of 12 wt% or pure NMP solvent) to full developed fibres as mass ratio increased to 16 wt% with the volume ratio of NMP/acetone (6/4, 5/5, 4/6, 3/7). Beadless fibres were normally obtained within the voltage applied and their average diameter decreased with increasing the applied voltage.

Preparation of polyamide-6/chitosan composite nanofibers by a single solvent system via electrospinning for biomedical applications

This work was focused on preparation and characterizations of chitosan blended polyamide-6 nanofibers by a new single solvent system via electrospinning process for human osteoblastic (HOB) cell culture applications. The morphological, structural and thermal properties of the polyamide-6/chitosan nanofibers were analyzed by using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, Raman spectroscopy, differential scanning calorimetry (DSC) and thermogravimetry (TGA). SEM images revealed that the nanofibers were well-oriented and had good incorporation of chitosan. FT-IR results indicated that the amino groups of chitosan existed in the blended nanofibers. TGA analysis revealed that the onset degradation temperature was decreased with increasing chitosan content in the blended nanofibers. The morphological features of the cells attached on nanofibers were confirmed by SEM. The adhesion, viability and proliferation properties of osteoblast cells on the polyamide-6/chitosan blended nanofibers were analyzed by in vitro cell compatibility test.

Simplified preparation of low polydispersity, low molecular weight poly(D,L‐lactic acid) by liquid/liquid phase separation for drug delivery systems with discussion of molecular weight characterization

AbstractPoly(D,L‐lactic acid) (PLA) has been widely used in pharmaceutics and medicine. Low molecular weight (LMW) PLA is especially useful for rapidly degrading biomaterials such as those used for short‐duration drug delivery systems. There is scant information available in the literature regarding the purification and analysis of LMW PLA. In this paper we report (1) a convenient and effective polymer purification/fractionation technique to produce LMW PLA with narrow molecular weight distribution (MWD) and (2) analyses that were used to characterize the molecular weight and MWD of these polymers. A novel, convenient and effective temperature‐induced solution‐phase separation method was developed to produce narrow MWD, LMW (600–2000 g mol−1) PLA. Molecular weights determined using gel permeation chromatography (GPC) with universal calibration, unlike those determined with the commonly used conventional calibration, showed good agreement with those obtained using several independent direct techniques. The phase separation induced by temperature reduction of a polymer in a single solvent system provided a simple and effective technique to produce narrow MWD, LMW PLA polymers. Additional advantages of this technique are: (1) only one solvent is required; (2) the risk of local complete solid polymer precipitation is eliminated; (3) it is reversible and not dependent on the rate of cooling; and (4) use of chlorinated solvents is avoided. This technology may open up a new opportunity for manufacturing LMW polymers with narrow MWD. We also found that GPC with universal calibration is a more accurate method than GPC with the commonly used conventional calibration for characterizing these polymers, and is straightforward to use especially now that on‐line viscosity detectors are widely available. Copyright © 2010 Society of Chemical Industry

Preparation and electrical characterization of polyamide-6/chitosan composite nanofibers via electrospinning

We report on the preparation and electrical characterization of polyamide-6/chitosan composite nanofibers. These composite nanofibers were prepared using a single solvent system via electrospinning process. The resultant nanofibers were well-oriented and had good incorporation of chitosan. Current–voltage (I–V) measurements revealed interesting linear curve, including enhanced conductivities with respect to chitosan content. The electrical conductivity of the polyamide-6/chitosan composite nanofibers increased with increasing content of chitosan which was attributed to the formation of ultrafine nanofibers. In addition, the sheet resistance of composite nanofibers was decreased with increasing chitosan concentration.

Effect of solvents on high aspect ratio polyamide-6 nanofibers via electrospinning

The effect of the solvent on the formation of high aspect ratio ultrafine fibers in polyamide-6 using an electrospinning technique was examined systematically. In this study, formic acid, dichloromethane, acetic acid, chlorophenol, hexafluoroisopropanol, and trifluoroacetic acid via single and mixed solvent system were used for the production of high aspect ratio nanofibers in polyamide-6. Formic acid and mixtures of formic acid/dichloromethane, formic acid/acetic acid, and formic acid/chlorophenol can lead to the very clear dissolution of polyamide-6, enabling their subsequent electrospinning to obtain high aspect ratio nanofibers. Formic acid was found to be the most suitable solvent system for obtaining high aspect ratio nanofibers in polyamide-6. The conductivity of polyamide-6 in formic acid was very high demonstrating an increasing level of free ions in solution. The average diameter of the high aspect ratio nanofibers was approximately one order of magnitude lower than that of main fibers. These findings suggest that the formation of high aspect ratio nanofibers relies strongly on the specific properties, such as the poly-electrolytic behavior of polyamide-6 in the solvent.

Novel method of synthesizing poly(ether sulfone) membranes containing two solvents and a lithium chloride additive and their performance

AbstractThe influence of a lithium chloride (LiCl) additive on poly(ether sulfone) (PES) membranes was investigated. A microwave technique was used to prepare membrane dope solutions, and two different types of solvent systems were used: single‐solvent (SS) and double‐solvent (DS) systems. In the SS system, PES was dissolved in N,N‐dimethylformamide (DMF), and In the DS system, PES was dissolved in DMF and acetone. In the DS system, the control ratio of DMF to acetone was kept at 3.47, and the concentration of LiCl in both solvent systems was varied from 1 to 4 wt %. We observed that the microwave technique was able to dissolve the polymer rapidly, in less than 1 h. The performance of the PES membrane was evaluated in terms of poly(ethylene glycol) separation and molecular weight cutoff (MWCO). The results reveal that the presence of LiCl improved both the flux and rejection rates, and its concentration was best kept at 3 wt % for the tested conditions. In addition, we found that the mean pore size of the membranes produced from the DS system was smaller and the MWCO was lower as compared to the SS system. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010