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排序方式: 共有785条查询结果,搜索用时 15 毫秒
721.
New methylene blue (NMB) dye incorporated into AlMCM‐41 surfactant‐free and hybrid surfactant‐AlMCM‐41 mesophase. UV‐vis evidence shows that new methylene blue dye protonated in both cases of zeolites. New methylene blue is electroactive in zeolites and their electrochemical activity has been studied by cyclic voltammetry and compared to that of NMB in aqueous solutions. New methylene blue molecules are not released to the solution during CV measurements and are accessible to H3O+ ions. The presence of surfactant affects the kinetics of the redox process through proton ions diffusion. The midpoint potentials (Em) values show that new methylene blue dye incorporated into AlMCM‐41 can be reduced easily with respect to solution new methylene blue. New methylene blue interacting with surfactant polar heads and residual Br? ions as a results, it shows a couple of peaks in high potential with respect to new methylene blue solution. The electrode made with methylene blue‐AlMCM‐41 without surfactant was used for the mediated oxidation of ascorbic acid. The anodic peak current observed in cyclic voltammetry was linearly dependent on the ascorbic acid concentration. The calibration plot was linear over the ascorbic acid concentration range 1.0×10?5 to 5.0×10?4 M. The detection limit of the method is 1.0×10?5 M, low enough for trace ascorbic acid determination in various real samples. 相似文献
722.
Dae Hyan Cho 《Tetrahedron letters》2005,46(11):1799-1802
An efficient and mild method is developed for radical deoxygenation of alcohols and formation of carbon-carbon bonds in water without adding additives such as surfactants. The reaction was applied to synthesis of 2′,3′-didehydro-2′,3′-dideoxynucleosides that are potent anti-HIV agents. The reaction afforded environmentally benign reaction conditions. 相似文献
723.
P.?C.?GriffithsEmail author J.?A.?Roe A.?M.?Howe A.?R.?Pitt 《Colloid and polymer science》2004,282(10):1160-1164
The SDS unimer concentration in a series of mixed anionic/non-ionic surfactant solutions comprising sodium dodecylsulphate (SDS) and sugar-based dodecyl bis-N-methyl gluconamides (C12BNMG) have been studied using an anionic surfactant selective electrode, both in the presence and absence of the polyampholyte gelatin. The activity of the SDS has been calculated at the critical micelle concentration (CMC) in the gelatin-free studies and at CMC(1) in the gelatin studies. From the known solution composition, the activity coefficients can be calculated; these show deviations from unity around a solution mole fraction (SDS) of 0.95 SDS in both cases. The deviation is significantly greater in the presence of gelatin, to an extent that the SDS activity versus SDS curve exhibits a maximum and a minimum in the region SDS=0.8–1.0, consistent with the possibility of coexisting micelle types, in agreement with our earlier NMR study (Griffiths et al. (1998) J Chem Soc Chem Comm 1:53). 相似文献
724.
An alumina surface was modified by adsorption of an anionic surfactant, sodium dodecyl sulfate (SDS). Typical S‐shaped isotherm of surfactant on alumina was observed. The adsorption of Disperse Red‐11, Disperse Blue‐26 and Disperse Red‐156 on alumina and surfactant treated alumina has been investigated. The enhancement in adsorption of these disperse dyes on surfactant treated alumina is observed, which may be attributed to their solubilization in surfactant aggregates formed at the solid/liquid interface. The effect of pH on adsorption has been studied. The adsorption is greatly influenced by pH of the medium. The applicability of the Langmuir model and the Dual‐Mode sorption model (DSM) were tested for equilibrium data. 相似文献
725.
碳氢与碳氟表面活性剂混合水溶液的胶团与囊泡形成 总被引:2,自引:0,他引:2
碳氢与碳氟表面活性剂混合水溶液的胶团与囊泡形成丁慧君,戴群英,张兰辉,赵国玺(北京大学物理化学研究所,北京,100871)关键词囊泡,表面活性剂,胶团形成,负离子结合度,表面活性利用结构简单的表面活性剂代替生物膦脂形成人工囊泡的研究正受到普遍关注[1... 相似文献
726.
The reduced viscosity of polymer guar gum solutions containing a certain concentration of sodium dodecyl benzene sulfonate (SDBS) was measured. It has been found that the Huggins coefficient kH of polymer solutions is very sensitive to the concentration of the surfactant, CSDBS, in solutions. If CSDBS is lower than CMC, the critical micelle concentration of SDBS, kH increases rapidly with CSDBS. On the other hand, if CSDBS is larger than CMC, kH decreases rapidly with CSDBS. Comparatively, the intrinsic viscosity of polymer solution does not show a notable change with CSDBS. The experimental results indicate that the interchain association of polymer guar gum in solution is greatly associated with SDBS interacted with polymer chains through hydrogen bonds. However, the effect of SDBS upon the intrachain association of polymer guar gum solution is negligible, presumably due to the fact that guar gum is a slightly stiffened random-coil chain polymer. 相似文献
727.
728.
Effect of a nonionic surfactant on Trichoderma cellulase treatments of regenerated cellulose and cotton yarns 总被引:1,自引:0,他引:1
Chiyomi Mizutani Kandan Sethumadhavan Phyllis Howley Noelie Bertoniere 《Cellulose (London, England)》2002,9(1):83-89
It has been shown that some surfactants affect the hydrolysis of cellulose by cellulase. In this study, the effect of the surfactant Tween 20 on the hydrolysis of different cellulosic fibers was investigated and related to the cellulose fiber structure. It was found that this non-ionic surfactant enhanced the enzymatic saccharification of highly crystalline cellulosics such as Avicel, Tencel and cotton but not of cuprammonium rayon. The enhanced saccha-rification effected by the surfactant is attributed to inhibition of non-productive sorption of the endoglucanase of the cellulose surface which gives greater access to the cellulose chain ends by the exoglucanase. Although all three fibers lost tensile strength as a result of the enzymatic treatment, no further decrease was effected by the presence of the surfactant. 相似文献
729.
O. López M. Cócera L. Coderch J. L. Parra A. de la Maza 《Colloid and polymer science》2002,280(4):352-357
The lytic interactions of the nonionic surfactant dodecyl maltoside (DM) with liposomes formed by a mixture of lipids modeling
the stratum corneum (SC) lipid composition were investigated. To this end, the surfactant to lipid molar ratios (Re) and the
normalized bilayer/aqueous phase partition coefficients (K) were determined by monitoring the changes in the static light-scattering
(SLS) of the system during solubilization. The fact that the free surfactant concentration was always similar to its critical
micelle concentration indicates that the liposome solubilization was mainly ruled by formation of mixed micelles. In addition,
the linear dependence established between the level of SLS and Re indicates a progressive incorporation of DM in the liposomes
as well as the progressive formation of mixed micelles. DM showed in all cases lower bilayer activity (higher Re values) and
greater affinity with vesicles (higher K values) than those reported for its interaction with phosphatidylcholine (PC) liposomes.
Thus, whereas the SC lipid liposomes were more resistant to the action of this surfactant, its degree of partitioning into
SC bilayers was higher throughout the solubilization process than that exhibited in PC vesicles. Comparison of the present
Re values with those reported for the lytic interaction of dodecyl glucoside (DG) with SC liposomes reveals that in the case
of DM the bilayer activity was more than three times higher than that for DG in spite of the identical alkyl chain length.
Received: 19 July 2001 Accepted: 10 October 2001 相似文献
730.
《Electroanalysis》2004,16(8):674-683
The cobalt hexacyanoferrate film (CoHCF) was deposited on the surface of a glassy carbon (GC) electrode with a potential cycling procedure in the presence and absence of the cationic surfactant, cetyl trimethylammonium bromide (CTAB), to form CoHCF modified GC (CoHCF/GC) electrode. It was found that CTAB would affect the growth of the CoHCF film, the electrochemical behavior of the CoHCF film and the electrocatalytic activity of the CoHCF/GC electrode towards the electrochemical oxidation of dopamine (DA). The reasons of the electrochemical behavior of CoHCF/GC electrode influenced by CTAB were investigated using FTIR and scanning electron microscope (SEM) techniques. The apparent rate constant of electrocatalytic oxidation of DA catalyzed by CoHCF was determined using the rotating disk electrode measurements. 相似文献