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101.
102.
Rheological behavior of an elongated micellar solution at low and high salt concentrations 总被引:2,自引:0,他引:2
The aim of this experimen-tal work is to investigate the mechanism responsible of the decrease of the zero shear viscosity
at high inorganic salt content. We report the linear and some nonlinear rheological properties of aqueous worm-like micellar
solutions of CTAB containing NaNO3 salt. The zero-shear viscosity η0 curve versus salt concentration exhibits a well-defined maximum. We choose two salt concentrations (low and high) having
the same zero-shear viscosity, and carefully explore the rheological characteristics and their evolutions in (and around)
these two situations. The experimental results presented here, without excluding the possibility of the connections, suggest
the possibility that the decreasing of η0 is a result of the reduction in size of the worm-like micelles.
Received: 16 February Accepted: 8 June 1998 相似文献
103.
A novel method for the rapid screening of clandestine tablets for drugs by MALDI-TOF mass spectrometry is described. In this method, cetrimonium bromide (CTAB), a surfactant, is added to the conventional α-cyano-4-hydroxycinnamic acid (CHCA) matrix solution used in preparing the MALDI samples. This procedure allows very clean mass spectra to be collected for amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), caffeine, ketamine and tramadol. The method was used successfully in the rapid drug-screening of some actual clandestine tablets, which had been seized from the illicit market, and can serve as a good complementary method to GC/MS for use in forensic analysis. 相似文献
104.
Hong‐Wen Gao 《中国化学会会志》2002,49(1):33-38
The microphase adsorption‐spectral correction (MPASC) technique was de scribed and applied to study the interaction of bromo‐pyrogallol red (BPR) with cetyl trimethylammonium bromide (CTAB). The synergism mechanism of micelles was analyzed and discussed. The large electrostatic micelle adsorbs the chromophore in only the monolayer, and the adsorption obeys the Langmuir adsorption. The formation of the (BPR2·CTAB)78 aggregate accelerates the Mo‐BPR complex reaction. Experimental results showed the adsorption constant of the adsorption aggregate 6.20 × 105 and its molar absorptivity ?r610nm = 1.40 × 106 lmol?1cm?1. For analysis of samples, the recovery of Mo was between 97.4 and 107% and the RSD was less than 4.39%. 相似文献
105.
Kuldvee R Lindén MV Wiedmer SK Riekkola ML 《Analytical and bioanalytical chemistry》2004,380(2):293-302
Large unilamellar vesicles of egg-phosphatidylcholine (eggPC), a naturally occurring phospholipid, were used in capillary electrophoresis (CE) for semi-permanent coating of fused silica capillaries. The stability of the phospholipid coating was tested at different cetyltrimethylammonium bromide (CTAB) concentrations with and without CaCl2 present in the coating solution. The effect of physical factors influencing the coating stability (e.g. duration of the coating time, storage temperature of the coating solution) were also studied. Standing overnight in background electrolyte (BGE) solution did not alter the eggPC phospholipid coating noticeably. The performance of the coating was tested with a mixture of basic proteins (lysozyme, ribonuclease A and -chymotrypsinogen A). Highest efficiencies (over 200,000 plates m–1) were achieved when the capillary was filled for 15 h with a liposome solution containing both CTAB and CaCl2.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
106.
近年来有序交替的层状纳米结构薄膜的制备吸引了研究者们的极大关注. 目前, 这类薄膜的制备方法研究得最多的是LB技术[1~3]、基于化学吸附的自组装成膜技术[4,5]和交替沉积组装技术[6~8]. 但这几种方法都有明显的缺陷[9,10], 其中,通过LB技术制备有序交替层状纳米复合薄膜需要昂贵的仪器, 而且由于层间是分子相互作用, 膜的稳定性较差; 基于化学吸附的自组装成膜技术由于需要高反应活性的分子和特殊的基底表面, 并且由于化学反应的产率很难达到100%, 因此通过这种方法制备结构有序的多层膜并不容易; 利用交替沉积的方法制备出具有实用厚度的纳米多层膜需要耗费大量的时间. 最近, 出现了一种称为蒸发诱导的超分子自组装方法, 由这种方法制备的纳米多层膜具有成膜速度快和膜有序度高等优点, 此外还可以通过改变成膜物质浓度和拉膜速度来控制薄膜的厚度, 但与LB膜相比其厚度无法在分子水平上控制. 利用这种方法制备多层膜目前的文献报道仅限于线形SiO2与有机物的组装[10~13]. 本文利用这种方法制备了TiO2/十六烷基三甲基溴化铵纳米复合薄膜并对其结构进行了表征, 结果表明所制备的薄膜具有TiO2/十六烷基三甲基溴化铵有序交替的层状结构. 相似文献
107.
The effect of cationic micelles of cetyltrimethylammonium bromide (CTAB) on the interaction of chromium dipeptide complex ([Cr(Ⅲ)-Gly-Gly]2 ) with ninhydrin under varying conditions has been investigated. The rates of the reaction were determined in both water and surfactant micelles in the absence and presence of various organic and inorganic salts at 70 ℃ and pH 5.0. The reaction followed first- and fractional-order kinetics with respect to [Cr(Ⅲ)- Gly-Gly2 ] and [ninhydrin]. Increase in the total concentration of CTAB from 0 to 40×10-3 mol·dm-3 resulted in an increase in the pseudo-first-order rate constant (kψ) by a factor of ca 3. Quantitative kinetic analysis of kψ-[CTAB] data was performed on the basis of the pseudo-phase model of the micelles. As added salts induce structural changes in micellar systems that may modify the substrate-surfactant interactions, the effect of some inorganic (NaBr, NaCl, Na2SO4) and organic (NaBenz, NaSal, NaTos) salts on the rate was also explored. It was found that the tightly bound counterions (derived from organic salts) were the most effective. 相似文献
108.
Shu-gang WANG 《高等学校化学研究》2008,24(4):459-463
The major aim of this work was to synthesize thio-stabilized CdTe nanoparticles(NPs) in an aqueous solution, which was then enwrapped with cetyltrimethylammonium bromide(CTAB), and finally transferred to the polyvinylpyrrolidone(PVP) matrix by electrospinning. The PVP nanofibers containing CdTe NPs were characterized by scanning electron microscopy(SEM) and transmission electron microscopy(TEM), to observe the morphology of the nanofibers and the distribution of CdTe NPs. The selective area electronic diffraction(SAED) pattern verified that CdTe NPs were cubic lattice. The photoluminescence(PL) spectrum indicated that CdTe NPs existed in an optical style in PVP nanofibers. Moreover, X-ray photoelectron spectra(XPS) revealed that thiol-stabilized CdTe NPs were enwrapped by CTAB, and PVP acted as a dispersant in the process of electrospinning. 相似文献
109.
Xiaoyi Yang Binbin Zhang Chaohua Guo Jianbo Li Quanhong Li 《Journal of Dispersion Science and Technology》2018,39(10):1485-1491
The N-dodecyl chitosan sulfate (NDCS) with a higher degree of substitution of dodecyl was synthesized. The surface tension and transmission electron microscopy showed that the product had a higher surface activity and could self-assemble into bigger spherical polymeric micelles. Besides, the characteristics of complexation of NDCS with cetyltrimetylammonium bromide (CTAB) were studied by static/dynamic surface tension, turbidity and transmission electron microscopy. The results revealed that the mixture of NDCS with CTAB had a higher surface activity, lower diffusing rate and higher turbidity. Furthermore, they also could self-assemble into agglomerate or dispersed spherical aggregates in some concentration domain of CTAB. 相似文献
110.
Mohamed Bechir Chebab Memia Benna Malika Trabelsi-Ayadi 《Journal of Dispersion Science and Technology》2013,34(1):67-76
In this work, we have tested various formulations in order to get emulsions containing pure water, Tunisian olive oil, Tunisian clays, and an ammonium salt. Two different types of clays: smectite and kaolinite and the cethyltrimethylamonium bromide (CTAB) were tested. CTAB is used as surfactant and a compound modifying the clays properties. The amount of CTAB being fixed at 0.66 w/w, the proportions of clays were varied from 0 to 9% for each of the following proportions of water: 10, 20, 30%. To the aqueous phase obtained by mixing two separate aqueous phases: water + CTAB and water + clay, the oil was added drop by drop, the agitation being maintained at 5000 rpm. The obtained mixtures were analyzed by Differential Scanning Calorimetry (DSC), optical microscopy and bottle tests. An optimized formulation containing water (30%), smectite clay (5.3%) and CTAB (0.66%) was found to give W/O emulsions which kinetic stability is greater than 75 days regarding coalescence and greater than 700 hours regarding sedimentation. 相似文献