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    Optimal extraction solvents use for extraction of Thunbergia laurifolia Linn. Leaves and its mode of action on weed control
    (2018-12-01)
    Thinh, N. H.
    ;
    Laosinwattana, C.
    ;
    Wichittrakarn, P.
    Thunbergia laurifolia Lindl. leaves were extracted by various ratios (0, 25, 50, 75 and 100%) of ethanol in water as solvents for crude extraction. The highest crude extract yield was obtained by using 25% ethanol solvent with three time extractions. The inhibitory effect of each extract on seed germination and seedling growth of Amaranthus gracilis was investigated. The results indicated that the 100% ethanol extract expressed the best inhibitory effect. At concentration of 1250 ppm, the 100% ethanol extract completely inhibited seed germination of A. gracilis. The 100% ethanol extract also inhibited α-amylase activities in A. gracilis seed during seed germination. However, the extract does not show effect on seed imbibition. The inhibition of induction of α-amylase increased with increasing concentration of the 100% ethanol extract.
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    Influence of solvent species used in solvent exchange for preparation of mesoporous carbon xerogels from resorcinol and formaldehyde via subcritical drying
    (2011-02-01)
    Kraiwattanawong, Kriangsak
    ;
    Tamon, Hajime
    ;
    Praserthdam, Piyasan
    Carbon cryogels are dried by 3 days of freeze drying with 6 h of pre-freezing whereas the carbon xerogels are prepared by 1 day of subcritical drying in the selective range of synthesis condition, but the mesoporosity of carbon xerogels are not well controlled. This research is to study the influence of solvent species in the solvent exchange for the preparation of carbon xerogels cooperated by the evaporation drying and the vacuum drying. The good solvent for the high mesoporous properties of carbon xerogels is desirable in the wide range of synthesis condition. The carbon xerogels prepared from resorcinol and formaldehyde were characterized by the nitrogen adsorption apparatus and the field emission scanning electron microscope (FE-SEM). The results illustrate that the mesoporous carbon xerogels in the two subcritical dryings can be easily prepared by solvent exchange. Among the solvents, t-butanol allows the great results in the preparation of high mesoporous carbon xerogels and is well applied in the wide range of synthesis conditions. The FE-SEM images elucidate that the carbon xerogels dried by the vacuum drying contain the particles interconnection larger than the evaporation drying. © 2010 Elsevier Inc. All rights reserved.
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    Electrospun cellulose acetate fibers: Effect of solvent system on morphology and fiber diameter
    (2007-12-01)
    Tungprapa, Santi
    ;
    Puangparn, Tanarinthorn
    ;
    Weerasombut, Monchawan
    ;
    Jangchud, Ittipol
    ;
    Fakum, Porntiva
    This paper reports an investigation of the effects of solvent system, solution concentration, and applied electrostatic field strength (EFS) on the morphological appearance and/or size of as-spun cellulose acetate (CA) products. The single-solvent systems were acetone, chloroform, N, N-dimethylformamide (DMF), dichloromethane (DCM), methanol (MeOH), formic acid, and pyridine. The mixed-solvent systems were acetone-DMAc, chloroform-MeOH, and DCM-MeOH. Chloroform, DMF, DCM, MeOH, formic acid, and pyridine were able to dissolve CA, forming clear solutions (at 5% w/v), but electrospinning of these solutions produced mainly discrete beads. In contrast, electrospinning of the solution of CA in acetone produced short and beaded fibers. At the same solution concentration of 5% (w/v) electrospinning of the CA solutions was improved by addition of MeOH to either chloroform or DCM. For all the solvent systems investigated smooth fibers were obtained from 16% (w/v) CA solutions in 1:1, 2:1, and 3:1 (v/v) acetone-DMAc, 14-20% (w/v) CA solutions in 2:1 (v/v) acetone-DMAc, and 8-12% (w/v) CA solutions in 4:1 (v/v) DCM-MeOH. For the as-spun fibers from CA solutions in acetone-DMAc the average diameter ranged between 0.14 and 0.37 μm whereas for the fibers from solutions in DCM-MeOH it ranged between 0.48 and 1.58 μm. After submersion in distilled water for 24 h the as-spun CA fibers swelled appreciably (i.e. from 620 to 1110%) but the physical integrity of the fibrous structure remained intact. © Springer Science+Business Media, Inc. 2007.