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31.
Cellulose nanofibrils (CNF) from wood fibers are of increasing interest to industry because they are from renewable sources and are biodegradable. Owing to their high aspect ratio, they produce viscous suspensions and stiff gels that are strengthened by interfibrillar hydrogen bonds. In this study, the viscosity of aqueous CNF suspensions, at dilute concentrations ( \(nL^{3}<1\) ), was measured at various pH values by addition of HCl, and at various ionic strengths by addition of NaCl and \(\hbox {CaCl}_{2}\) . The results show that the primary electroviscous effect significantly increases the intrinsic viscosity. The intrinsic viscosity under conditions where the surface charge of nanofibrils is fully screened is in good agreement with the predictions of classical theory for dispersions of rodlike particles at low shear rates. Increasing the ionic strength up to \(\kappa d\approx 1\) decreases the intrinsic viscosity; at \(\kappa d>1\) , the intrinsic viscosity increases because of fibril aggregation and increase of the effective volume fraction. 相似文献
32.
Inside Back Cover: Controlled Electropolymerization of Ruthenium(II) Vinylbipyridyl Complexes in Mesoporous Nanoparticle Films of TiO (Angew. Chem. Int. Ed. 19/2014)
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33.
Complex Surface Chemistry of an Otherwise Inert Solvent Molecule: Tetrahydrofuran on Si(001)
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Dr. Gerson Mette Marcel Reutzel Dr. Ruben Bartholomäus Dr. Slimane Laref Dr. Ralf Tonner Prof. Dr. Michael Dürr Prof. Dr. Ulrich Koert Prof. Dr. Ulrich Höfer 《Chemphyschem》2014,15(17):3725-3728
The reaction of tetrahydrofuran (THF), an otherwise inert solvent molecule, on Si(001) was experimentally studied in ultra‐high vacuum. Using scanning tunneling microscopy (STM) and photoelectron spectroscopy at variable temperature, we could both isolate a datively bound intermediate state of THF on Si(001), as well as the final configuration that bridges two dimer rows of the Si(001) surface after ether cleavage. The latter configuration implies splitting of the O?C bond, which is typically kinetically suppressed. THF thus exhibits a hitherto unknown reactivity on Si(001). 相似文献
34.
4-Amino-1,2,4-triazolium nitrate (4-ATN) is an energetic and non-sensitive ionic liquid, which was introduced as a good candidate in previous works for the replacement of 2,4,6-trinitrotoluene (TNT) in melt-cast explosives. Since previous studies used pure nitric acid for nitration of 4-ATN, the effect of the use of low price industrial nitric acids (50 %, 70 % and 98 %) is investigated on the percent yields of 4-ATN. The thermogravimetric and differential scanning calorimetry (TGA/DSC) are done on the synthesized 4-ATN with impure nitric acid at a heating rate of 10 K · min–1 by the vacuum system. The obtained TGA/DSC curves confirm decomposition of 4-ATN involving melting and dissociation. Derivative thermogravimetric (DTG) curves of 4-ATN at various heating rates are applied to obtain activation energy of thermolysis by several model-free techniques. The calculated activation energies are in the range 78.7–87.7 kJ · mol–1, which are about 10 kJ · mol–1 more than the reported activation energy of industrial TNT (purity 98.2 %), i.e. 66–70 kJ · mol–1. Assessments of detonation performance of 4-ATN are also compared with TNT, which show higher detonation performance of 4-ATN. Thus, 4-ATN can be used with nitramine compounds as melt-cast explosives with higher thermal stability and detonation performance than corresponding nitramine compound/TNT explosives. 相似文献
35.
Leila Ghasempour Sakineh Asghari Mahmood Tajbakhsh Mojtaba Mohseni 《Journal of heterocyclic chemistry》2020,57(12):4136-4148
One-pot four-component reactions of phenacyl bromides, parabanic or thioparabanic acids, thiophenols, and triphenylphosphine in the presence of triethylamine afforded new derivatives of hydantoin or thiohydantoin in good to high yields (65%-90%). Their antibacterial activities were evaluated against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Among the synthesized compounds, the obtained products from 2-hydroxythiophenol exhibited higher antibacterial activity than those obtained from 2-aminothiophenol. Compound 9l including N,N′′-diphenyl thiohydantoin moiety showed the highest antibacterial activity (26.0 ± 01.4) against B subtilis, in comparison with other synthesized samples. The antioxidant activities of the synthesized hydantoins and thiohydantoins were investigated by DPPH radical-scavenging based on Blois method. The results showed that all the compounds have high DPPH inhibition potency (77.4%-83.9%) that it could be due to existence of heteroatoms with lone pair electrons and exchangeable protons on their NH2 and OH groups. 相似文献
36.
Rahnamafa Reyhaneh Moradi Leila Khoobi Mehdi 《Research on Chemical Intermediates》2020,46(4):2109-2116
Research on Chemical Intermediates - 4H-benzo[b]pyrans were obtained rapidly in high yields using triethanolamine as an efficient, eco-friendly and low-cost basic catalyst. One-pot three-component... 相似文献
37.
Leila Kharbouche María Dolores Gil García Ana Lozano Hadj Hamaizi María Martínez Galera 《Journal of separation science》2020,43(11):2142-2153
A silica‐based MCM‐41 mesoporous material functionalized with cyanopropyl groups has been synthesized by cocondensation, characterized and applied to preconcentrate six parabens and three UV filters in river and swimming‐pool waters. The analytes were quantified by ultra‐high performance liquid chromatography‐tandem mass spectrometry, according to the Directive 96/23/EC. Even though matrix effect was negligible, quantification in river water samples with the standard addition approach improved the recoveries obtained using solvent‐based and even with matrix‐matched calibration. The method quantification limits in river water samples were 0.05 ng/mL for 2,4‐dihydroxybenzophenone and 0.01 ng/mL for the rest. Recoveries, evaluated for a concentration level of 0.5 ng/L, were in the range 93.5‐107.6% for parabens and in the range 64.2‐85.8% for UV filters, with relative standard deviations intraday ≤10.2 and 10.8%, respectively. This parameter, evaluated for a concentration level of 0.1 ng/L, ranged between 98.3 and 110.4% for parabens and between 61.9 and 89.9% for UV filters, with relative standard deviation intraday ≤15.3 and 15.5%, respectively. The two UV filters with lower recoveries were the most affected by the addition of sodium chloride. River and swimming pool waters were analyzed and all the personal care products were found in the swimming pool water, whereas only methylparaben was detected in the river water. 相似文献
38.
2, 4-Bis-(4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane-2, 4-disulfide [Lawesson reagent (LR)] 1 reacts with p-quinone monoimine- 2a to give the novel benzo-1,3,2-oxathiaphosphol-5-(methanesulfonamido)-2-(4-methoxyphenyl)-2-sulfide 4 . On the other hand, the reaction of 2b and 3 with LR 1 leads to the formation of the benzo- and the naphtho-1,3,2-dithiaphosphol-5 -(benzenesulfonamido)- 2- (4-methoxyphenyl) -2-sulfide 5 , 6 . Thiation of 2a , 2b , and 3 with P4S10 yields phenoxathiin derivatives 8a , 8b , and 9 , respectively. The identity of the new products is established from analytical and spectroscopic evidence. 相似文献
39.
Ange Polidori Bernard Pucci Leila Zarif Jean G. Riess Andr A. Pavia 《Macromolecular rapid communications》1996,17(4):229-238
Sugar-derived surfactants bearing a polymerizable acryloyl moiety on one of the branches of the double-chain hydrophobic tail were prepared. The non–ionic hydrophilic head and the biantennary hydrophobic tail were built on, respectively, an aspartic acid and a tris(hydroxymethyl)aminomethane core. Ultraviolet irradiation of aqueous dispersions of these surfactants above their transition phase temperature (Tc) was achieved. The morphology of self-assemblies produced in such a way were investigated by transmission electron microscopy. TEM photographs revealed that irradiation leads to the formation of unilamellar vesicles. Neither fibers nor tubules were detected in contrast to what was observed before polymerization. 相似文献
40.
Leila Saedi Zahra Javanshir Salah Khanahmadzadeh Maryam Maskanati Milad Nouraliei 《Molecular physics》2020,118(7)
ABSTRACTDensity functional theory calculations were used to investigate the potential application of an AlN nanocluster in the detection of H2S, COS, CS2 and SO2 gases. In overall, the order of strength of interaction of these gases with the nanocluster is as follows: SO2 (Ead?=??17.6?kcal/mol)?>?H2S (Ead?=??14.0?kcal/mol)?>?COS (Ead?=??8.4?kcal/mol)?>?CS2 (Ead?=??4.5?kcal/mol). This indicates that by increasing the electric dipole moment, the adsorption energy becomes more negative. We found that the Al12N12 nanocluster may be a promising work function-type sensor for SO2 gas among the studied gases. Also, it is an electronic sensor for both SO2 and CS2 gases but selectively acts between them because of their different effects on the electrical conductivity. It is neither work function-type nor electronic sensor for H2S and COS gases. The AlN nanocluster benefits from a short recovery time about 7.7?s and 18.0?ms for desorption of SO2 and CS2 gases from its surface at room temperature, respectively. It is also concluded that this cluster can work at a humid environment. 相似文献