| 1. |
- Tehrani, Ali, 1976, et al.
(författare)
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An Ouzo Emulsion of Toluene in Water Characterized by NMR Diffusometry and Static Multiple Light Scattering
- 2016
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 1873-4359 .- 0927-7757. ; 494, s. 81-86
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Tidskriftsartikel (refereegranskat)abstract
- An Ouzo emulsion is an emulsion that is formed spontaneously by adding water to a system comprising a hydrophobic substance (like anethole in the Ouzo beverage), a water-miscible solvent and (optionally) water. Formation of such an emulsion does not require the use of surfactants, dispersing agents, or mechanical agitation. In this work, Ouzo emulsions were prepared from the ternary mixture toluene-ethanol-water and the emulsion stability was studied by a combination of two techniques: static multiple light scattering and NMR diffusometry. A bimodal distribution of the droplets was found. The light scattering technique revealed the presence of large drops, several micrometer in size. NMR measurements confirmed the large drops but also showed the additional presence of droplets of the order of 100 nm in diameter. The distribution of toluene between the three environments (i) large drops, (ii) small droplets, and (iii) the continuous ethanol-water phase could also be assessed. It was found that addition of an anionic surfactant to the system yielded an improved dispersed system, i.e., more toluene was present as small droplets and less toluene was dissolved in the ethanol-water phase; however the presence of the amphiphile reduced the emulsion stability. (C) 2016 Elsevier B.V. All rights reserved.
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| 2. |
- Tehrani, Ali, 1976, et al.
(författare)
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Micelle growth of cationic gemini surfactants studied by NMR and by time-resoved fluorescence quenching
- 2013
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 405, s. 145-149
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Tidskriftsartikel (refereegranskat)abstract
- The micelle growth of a series of five cationic gemini surfactants has been investigated by time-resolved fluorescence quenching (TRFQ) and by two NMR techniques, line width analysis and diffusometry. The surfactant series was designed such that the effect of a number of variables could be assessed: length of the spacer unit, presence of ester bonds in the tails close to the head groups, and presence of a hydroxyl group in the spacer. For the gemini with long spacer, the micelles remained relatively small in size upon an increase of the concentration. The gemini surfactants with short spacer, on the other hand, showed a considerable micellar growth as the concentration was raised. It is of particular interest that the relatively simple line width analysis of one dimensional H-1 NMR spectra gave qualitatively the same results as the more sophisticated TRFQ and NMR diffusometry techniques.
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| 3. |
- He, Wenxiao, 1985, et al.
(författare)
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Mesoscopically Ordered Bone-Mimetic Nanocomposites
- 2015
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 27:13, s. 2260-2264
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Tidskriftsartikel (refereegranskat)abstract
- A sustainable approach that highly mimics bone-material deposition is reported to produce mechanically stable, degradable composites with nanostructures resembling that of natural bone. Molecular self-assembly combining intermolecular crosslinking leads to resilient matrices possessing long-range ordered aqueous domains, inside which moderately aligned poorly crystalline apatite is converted from the transient amorphous calcium phosphate phase.
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| 4. |
- Jain, Titoo, et al.
(författare)
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Additional Article Notification: Anisotropic growth of gold nanoparticles using cationic gemini surfactants: effects of structure variations in head and tail groups
- 2014
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Ingår i: Journal of Materials Chemistry C. - 2050-7534 .- 2050-7526. ; 2:17, s. 3476-3485
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A library of gemini surfactants is employed to study surfactant directed anisotropic growth of gold nanoparticles. The surfactants are modified with respect to the length and type of the tails, as well as of the spacer group. By analyzing the structure of the anisotropic nanoparticles, it is possible to extract information on how the structure of the surfactants influences the anisotropic gold nanocrystal growth. We find that the tail length of the surfactants has a greater influence on the resulting nanoparticle aspect ratio compared to the chemical nature of the spacer group. While clear trends between the aspect ratio and the tail as well as spacer length remain elusive, we observe that surfactants with a critical micelle concentration of similar to 1 mM produce particles with the highest aspect ratio. A crystallographic analysis of nanorods obtained using gemini surfactants reveals that they grow along 100 and are bound by {310} facets. This observation, which is specific for gemini surfactants, is explained by taking into account the preferential alignment of gemini surfactants with surface steps as suggested by electronic structure calculations.
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| 5. |
- Jain, T., et al.
(författare)
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Anisotropic growth of gold nanoparticles using cationic gemini surfactants: effects of structure variations in head and tail groups
- 2014
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Ingår i: Journal of Materials Chemistry C. - : Royal Society of Chemistry (RSC). - 2050-7526 .- 2050-7534. ; 2:6, s. 994-1003
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Tidskriftsartikel (refereegranskat)abstract
- A library of gemini surfactants is employed to study surfactant directed anisotropic growth of gold nanoparticles. The surfactants are modified with respect to the length and type of the tails, as well as of the spacer group. By analyzing the structure of the anisotropic nanoparticles, it is possible to extract information on how the structure of the surfactants influences the anisotropic gold nanocrystal growth. We find that the tail length of the surfactants has a greater influence on the resulting nanoparticle aspect ratio compared to the chemical nature of the spacer group. While clear trends between the aspect ratio and the tail as well as spacer length remain elusive, we observe that surfactants with a critical micelle concentration of similar to 1 mM produce particles with the highest aspect ratio. A crystallographic analysis of nanorods obtained using gemini surfactants reveals that they grow along and are bound by {310} facets. This observation, which is specific for gemini surfactants, is explained by taking into account the preferential alignment of gemini surfactants with surface steps as suggested by electronic structure calculations.
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| 6. |
- Javadian, S., et al.
(författare)
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Self-assembled nano structures of cationic ester-containing gemini surfactants: The surfactant structure and salt effects
- 2013
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Ingår i: Journal of Chemical Thermodynamics. - : Elsevier BV. - 0021-9614 .- 1096-3626. ; 62, s. 201-210
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation behavior of ester-containing cationic gemini surfactants, dodecyl esterquat and dodecyl betainate geminis was investigated using tensiometry, conductometry, viscometry, dynamic light scattering (DLS), transmission electron microscopy (TEM) and optical microscopy techniques in the absence and presence of NaBr electrolyte. The effect of chemical structure (i.e. the presence of ester bond in alkyl chain and the spacer length) on physicochemical properties and morphology of the surfactants was studied. The results showed that the ester-containing gemini surfactants formed spherical aggregates at dilute concentration (1.1 %wt). At higher concentration (∼3.7 %wt) the morphology is different depending on the position of ester bond in alkyl chain and the spacer length. Dodecyl betainate gemini with short spacer (s = 2) formed gel as a result of the formation of worm-like micelles in the aqueous solution. Dodecyl betainate gemini (s = 3) formed large vesicles enclosing smaller ones and dodecyl esterquat gemini (s = 3) formed both short cylindrical and spherical micelles. The salt addition induced the growth of micelles and in the case of dodecyl betainate (s = 2) gemini changed the morphology from worm-like micelles to lamellar phase.
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| 7. |
- Mahdavian, M., et al.
(författare)
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Comparison of a Cationic Gemini Surfactant and the Corresponding Monomeric Surfactant for Corrosion Protection of Mild Steel in Hydrochloric Acid
- 2011
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Ingår i: Journal of Surfactants and Detergents. - : Wiley. - 1558-9293 .- 1097-3958. ; 14:4, s. 605-613
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Tidskriftsartikel (refereegranskat)abstract
- A cationic gemini surfactant, N,N'-didodecyl-N,N,N',N'-tetramethyl-1,4-butanediammonium dibromide (12-4-12) and the corresponding monomeric surfactant dodecyltrimethylammonium bromide were compared with respect to corrosion inhibition efficiency in 1 M hydrochloric acid solution. Polarization and electrochemical impedance spectroscopy were used to evaluate corrosion inhibition. The 12-4-12 surfactant showed an extremely high corrosion inhibition efficiency at very low concentration. Surface tension measurements performed under the strongly acidic conditions revealed that the gemini surfactant is remarkably electrolyte tolerant, which is beneficial for adsorption at the steel surface.
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| 8. |
- Momenzadeh, H., et al.
(författare)
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Reactive dye removal from wastewater using a chitosan nanodispersion
- 2011
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Ingår i: Desalination. - : Elsevier BV. - 0011-9164. ; 271:0011-9164, s. 225-230
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption of an azo reactive dye, C.I. Reactive Red 120 (RR120), from aqueous solution on chitosan and on a chitosan nanodispersion has been studied. The nanodispersion was prepared using a mixture of chitosan and sodium tripolyphosphate. The results showed that the adsorption of RR120 on dissolved chitosan and on the chitosan nanodispersion was affected significantly by initial dye concentration, sorbent amount, temperature, pH and ionic strength of the solution. Maximum dye removal for both adsorbents was at a pH of 4-5 and the adsorption of the reactive dye on both dissolved chitosan and the nanodispersion gave good fit to the Langmuir isotherm model. The adsorption capacity of the nanodispersion was around 910mgg-1, much higher than of dissolved chitosan, which was 51mgg-1. The adsorption of the dye on the chitosan nanodispersion reached equilibrium much faster than on dissolved chitosan. The kinetics of the adsorption correlated well with the pseudo-second order model.
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| 9. |
- Motamedi, M., et al.
(författare)
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A comparative study on the electrochemical behavior of mild steel in sulfamic acid solution in the presence of monomeric and gemini surfactants
- 2011
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 58:1, s. 488-496
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical behavior of mild steel in sulfamic acid solution in the presence of a gemini cationic surfcatant, butanediyl-1,4- bis(dodecyldimethylammonium bromide (12-4-12), and its monomeric counterpart, dodecyltrimethylammonium bromide (DTAB), was investigated as a function of the surfactant concentration by means of electrochemical impedance spectroscopy (EIS). The critical micelle concentration (cmc) values of DTAB and 12-4-12 in 1 M sulfamic acid solution, measured by surface tension measurement, were found to be 1.2 and 0.02 mM, respectively. The EIS results revealed a higher charge transfer resistance in 12-4-12 solution compared to that in DTAB solution at the same concentration normalized by the cmc (c/cmc). The morphology of the steel samples after being exposed to the acidic test solutions was examined by atomic force microscopy (AFM). The AFM micrographs showed a reduction of surface roughness in the presence of the surfactant which is more evident at higher surfactant concentrations. The adsorption of both surfactants in the sulfamic acid solution was studied by Langmuir and Flory-Huggins adsorption isotherms at submicellar concentrations.
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| 10. |
- Motamedi, M., et al.
(författare)
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Effect of aging time on corrosion inhibition of cationic surfactant on mild steel in sulfamic acid cleaning solution
- 2013
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 70, s. 46-54
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Tidskriftsartikel (refereegranskat)abstract
- The stability of the 1 M sulfamic acid solutions containing a gemini cationic surfactant (12-4-12) or its monomeric counterpart (DTAB) during 23 days of storage were studied by electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) and surface tension measurements. The EIS studies indicated that in comparison to DTAB solution, 12-4-12 solution considerably retained the corrosion inhibition during the storage period. The surface tension of DTAB solution was increased around 10 mN/m during storage while the surface tension of 12-4-12 solution was almost unchanged. The higher stability of 12-4-12 acidic solution than that of DTAB was also depicted by XRD results.
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