Counterion lyotropy and micelle formation

Underwood, A. L.; Anacker, E. W.

doi:10.1016/0021-9797(87)90188-3

Cited by 56 publications

(35 citation statements)

References 23 publications

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“…It is important to note that the growth solution contains some Hofmeister anions from the beginning, such as bromide (from CTAB), nitride (from AgNO 3 . 45 The rest of the four salts did allow the synthesis of Au NRs and more importantly tuned the L-LSPR band either to longer or shorter wavelengths. NaNO 3 , NaCl and NaHSO 4 red-shifted the L-LSPR, with bigger changes coming from the addition of 50 mM NaNO 3 (∆ L-LSPR = 76 nm).…”

Section: Resultsmentioning

confidence: 99%

Fine-tuning of gold nanorod dimensions and plasmonic properties using the Hofmeister effects

et al. 2016

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Gold nanorods (Au NRs) present unique optical and electronic properties that depend on their morphology. Their applications in sensing and therapeutics require easy syntheses with a precise control over their dimensions. Here, we report a method for the synthesis of highly pure and monodisperse Au NRs with fine-tuneable dimensions and longitudinal localised surface plasmon resonance by addition of Hofmeister salts into the growth medium. The control of Au NR formation relies on the double interaction between the salt-gold and salt-surfactant (cetyl trimethylammonium bromide, CTAB). With the addition of Hofmeister salts (i.e. NaNO3, NaBr, NaCl and NaHSO4) we can fine-tune the aspect ratio of Au NRs in the range of 3.3 to 4.8 with a precision of 0.1 and the longitudinal adsorption band from 777 to 960 nm. In addition, we have studied the physical changes of the CTAB micelles induced by the salts using rheology, microscopy and lightscattering techniques. We report for the first time electron microscopy imaging of the micelles under Au NR growth conditions. With the comprehensive characterization of CTAB micelle in the growth solution, this study provides a deeper understanding of the anisotropic growth of metallic crystals. have low affinity for gold, like nitrate, bisulphate and chloride, their addition yields longer aspect ratio rods. However, anions with high affinity for gold, like bromide, reduce the gold deposition, producing shorter aspect ratio rods. Interestingly, CTAB micelles are mainly sphere-shaped in all solutions. The addition of salt increases the overall micelle size by increasing the non-spherical micelle population, although spherical shape is still the predominant one. Hence, these results provide not just a new strategy for the precise tuning of the optical properties and morphology of Au NRs, but also a deeper understanding of the anisotropic growth mechanism of the nanoparticles.

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Section: Resultsmentioning

confidence: 99%

Fine-tuning of gold nanorod dimensions and plasmonic properties using the Hofmeister effects

et al. 2016

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“…The behaviour of N-alkylpyridinium halides [28,29,30], and of 1-methyl-4-octylpyridinium halides [31,32] confirms the above described trend. Structural parameters of micelles, such as degree of counterion binding, β [27,33,34] and aggregation number, n [35] are also strongly dependent on the effective size of the hydrated counterion, both decreasing with the increasing radius of the bare ion [36,37].…”

Section: Discussionmentioning

confidence: 99%

Is the counterion responsible for the unusual thermodynamic behaviour of the aqueous solutions of gemini bispyridinium surfactants?

Fisicaro

Compari

Bacciottini

et al. 2014

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Apparent and partial molar enthalpies at 298 K of the aqueous solutions of cationic gemini surfactants 1,1′-didodecyl-2,2′-trimethylenebispyridinium dichloride (12-Py(2)-3-(2)Py-12 Cl); 1,1′-didodecyl-2,2′-tetramethylenebispyridinium dichloride (12-Py(2)-4-(2)Py-12 Cl); 1,1′-didodecyl-2,2′-octamethylenebispyridinium dichloride (12-Py(2)-8-(2)Py-12 Cl); 1,1′-didodecyl-2,2′-dodecamethylenebispyridinium dichloride (12-Py(2)-12-(2)Py-12 Cl) were measured as a function of concentration and are here reported for the first time. The curve of the compound with the four carbon atoms spacer lies between those of the compound with spacer of 2 and 3 carbon atoms, not below the latter, as expected. This behaviour, we have already found for the same compounds here studied, but having methanesulfonate as counterion, is interpreted as an evidence of a conformation change of the molecule determined by stacking interactions between the two pyridinium rings, appearing at an optimum length of the spacer. The curves of apparent and molar enthalpies vs. concentration and surface tension measurements, here reported, show that this behaviour is independent on the counterion. On the contrary, the group contribution additivity for the counterion is respected, independently on the spacer length.Keywords. Apparent and partial molar enthalpies; cationic gemini surfactants; 1,1′-didodecyl-2,2′-trimethylenebispyridinium dichloride; 1,1′-didodecyl-2,2′-tetramethylenebispyridinium dichloride; 1,1′-didodecyl-2,2′-octamethylenebispyridinium dichloride; 1,1′-didodecyl-2,2′-dodecamethylenebispyridinium dichloride; micellization enthalpy, group contribution.Briefs. Apparent and partial molar enthalpies at 298 K of the aqueous solutions of cationic gemini surfactants 1,1′-didodecyl-2,2′-trimethylenebispyridinium dichloride (12-Py(2)-3-(2)Py-12 Cl);1,1′-didodecyl-2,2′-tetramethylenebispyridinium dichloride (12-Py(2)-4-(2)Py-12 Cl); 1,1′-didodecyl-2,2′-octamethylenebispyridinium dichloride (12-Py(2)-8-(2)Py-12 Cl); 1,1′-didodecyl-2,2′-dodecamethylenebispyridinium dichloride (12-Py(2)-12-(2)Py-12 Cl) have been measured as a function of concentration, in order to confirm the lack of methylene group additivity with respect to the enthalpic properties of the solutions, when it is added in the spacer, already found in the case of methansulfonates. The data obtained support the hypothesis of a conformation change dependent on the spacer length, but independent on the counterion.

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“…It decreases due to their dispersion of the charge of the ionic head groups thus diminishing their repulsion in the micelle [99]. Underwood and Anacker [103] found CMC had good correlation with the hydration enthalpy and hydration size of the inorganic counterions. They suggested that the most effective anions in promoting micellization are those which interact the least with water.…”

Section: Effects On the Cmc And Cmc IImentioning

confidence: 99%

“…Second, the CMC is also affected by the hydrophilic group species. Stigter [102] examined the CMCs of five surfactants each having a different type of head group, and proposed that the CMC was higher when the ionic charge on the head group was closer to the α -carbon of the alkyl chain. Head groups with the same charge will generate electrical repulsion, which may be the reason that the CMCs of ionic surfactants are higher than those of nonionic surfactants [99].…”

Section: Drag Reduction In Surfactant Solutionsmentioning

confidence: 99%

Review on Drag Reduction and Its Heat Transfer by Additives

Wang

Zakin

et al. 2011

Advances in Mechanical Engineering

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Since its discovery more than 60 years ago, the drag reduction phenomenon has achieved many notable energy saving effects. These achievements have encouraged researchers to study drag reduction further and further so that it can be utilized better. But due to the complex characteristics of turbulent flow, recent theories cannot explain all the phenomena of drag reduction. To give an overview of drag reduction and corresponding heat transfer for further understanding, this paper summarizes the main advancements of drag reduction during these 60 years, including background, application, development, theory, and research methods of different drag reducers. Future directions of development are also discussed.

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Counterion lyotropy and micelle formation

Cited by 56 publications

References 23 publications

Fine-tuning of gold nanorod dimensions and plasmonic properties using the Hofmeister effects

Fine-tuning of gold nanorod dimensions and plasmonic properties using the Hofmeister effects

Is the counterion responsible for the unusual thermodynamic behaviour of the aqueous solutions of gemini bispyridinium surfactants?

Review on Drag Reduction and Its Heat Transfer by Additives

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