Surface Structure of Sodium Dodecyl Sulfate Surfactant and Oil at the Oil-in-Water Droplet Liquid/Liquid Interface: A Manifestation of a Nonequilibrium Surface State

Aguiar, Hilton B. de; Strader, Matthew L.; Beer, Alex G. F. de; Roke, Sylvie

doi:10.1021/jp200536k

Cited by 128 publications

(180 citation statements)

References 83 publications

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“…This ordering at the planar oil-water interface is consistent with lamellar structures formed at solid-liquid and air-liquid interfaces (42). Less alkyl ordering of AOT at both nanoemulsion droplet interfaces found here is consistent with VSFSS studies of SDS at the droplet interface for regular nanoemulsions (25).…”

Section: Hydrophobic Chain Ordering Of Aot At Planar and Curved Surfacessupporting

confidence: 87%

“…The peaks at 2,856 ± 2 cm −1 and 2,869 ± 2 cm −1 are assigned to the methylene symmetric stretch (CH 2 -SS) and methyl symmetric stretch (CH 3 -SS), respectively. The peaks at 2,908 ± 2 cm −1 and 2,932 ± 2 cm −1 correspond to the methine stretch (C-H) and the Fermi resonance splitting between the CH 3 -SS and bending overtone, respectively (25,33,39,40). The spectra are fit with a relatively broad CH 2 -SS peak, which is justified as the intensity arises from numerous CH 2 moieties on different parts of the AOT molecule (green sites in Fig.…”

Section: Hydrophobic Chain Ordering Of Aot At Planar and Curved Surfacesmentioning

confidence: 95%

“…The droplet spectroscopy, pioneered by the Roke group (22)(23)(24)(25)(26), is conducted in a scattering geometry [vibrational sumfrequency scattering spectroscopy (VSFSS)], and the comparative planar surface studies (VSFS) are conducted in a total internal reflection geometry (TIR) as in previous work from this laboratory (16,18,27,28).…”

Section: Experimental Approachmentioning

confidence: 99%

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Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Hensel

Carpenter

Ciszewski

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Nanoemulsions and microemulsions are environments where oil and water can be solubilized in one another to provide a unique platform for many different biological and industrial applications. Nanoemulsions, unlike microemulsions, have seen little work done to characterize molecular interactions at their surfaces. This study provides a detailed investigation of the near-surface molecular structure of regular (oil in water) and reverse (water in oil) nanoemulsions stabilized with the surfactant dioctyl sodium sulfosuccinate (AOT). Vibrational sum-frequency scattering spectroscopy (VSFSS) is used to measure the vibrational spectroscopy of these AOT stabilized regular and reverse nanoemulsions. Complementary studies of AOT adsorbed at the planar oil-water interface are conducted with vibrational sum-frequency spectroscopy (VSFS). Jointly, these give comparative insights into the orientation of interfacial water and the molecular characterization of the hydrophobic and hydrophilic regions of AOT at the different oil-water interfaces. Whereas the polar region of AOT and surrounding interfacial water molecules display nearly identical behavior at both the planar and droplet interface, there is a clear difference in hydrophobic chain ordering even when possible surface concentration differences are taken into account. This chain ordering is found to be invariant as the nanodroplets grow by Ostwald ripening and also with substitution of different counterions (Na:AOT, K:AOT, and Mg:AOT) that consequently also result in different sized nanoparticles. The results paint a compelling picture of surfactant assembly at these relatively large nanoemulsion surfaces and allow for an important comparison of AOT at smaller micellar (curved) and planar oil-water interfaces.nanoemulsions | oil-water interfaces | vibrational sum-frequency scattering spectroscopy | surface spectroscopy | surfactants W e are all familiar with the adage that "oil and water do not mix," but of course, it depends upon the definition of "mix." Emulsions are an important special case, where the oil is dispersed as tiny droplets in the aqueous phase, taxonomically called a regular emulsion, or where the water is dispersed as tiny droplets throughout the oil phase, called a reverse emulsion. Because both emulsions are thermodynamically unstable, overcoming this requires an emulsifying agent such as a surfactant. Recently, there has been interest in surfactant-stabilized emulsions with droplet diameters in the nanoscale range for unique applications in drug delivery (1, 2) and oil recovery (3, 4) and as nanoreactors to produce materials ranging from polymers to quantum dots (5). Regular or reverse emulsions with droplet diameters in the range of 10-1,000 nm are called nanoemulsions. Little is known about the processes or molecular structures that result in their stability via surfactants. Even less is known about the structure-function relationship, which is crucial to determine the best surfactant for a given nanoemulsion application. Their utility hinges on a ...

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Section: Hydrophobic Chain Ordering Of Aot At Planar and Curved Surfacessupporting

confidence: 87%

Section: Hydrophobic Chain Ordering Of Aot At Planar and Curved Surfacesmentioning

confidence: 95%

Section: Experimental Approachmentioning

confidence: 99%

See 1 more Smart Citation

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Hensel

Carpenter

Ciszewski

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…These inconsistencies were ascribed to the inadequacy of the standard electrokinetic theory to describe the high surface potentials of the droplets and the properties of the inner part of the diffuse double layer. However, recent evidence indicates that the interfacial area occupied by the surfactant in nanoemulsions could be one order of magnitude higher than the one expected from the equilibrium adsorption of the surfactant to macroscopic interfaces [115].…”

Section: Flocculation Of Oil Dropsmentioning

confidence: 89%

Nanoemulsion stability: Experimental evaluation of the flocculation rate from turbidity measurements

Rahn-Chique¹,

Puertas²,

Romero-Cano³

et al. 2012

Advances in Colloid and Interface Science

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The coalescence of liquid drops induces a higher level of complexity compared to the classical studies about the aggregation of solid spheres. Yet, it is commonly believed that most findings on solid dispersions are directly applicable to liquid mixtures. Here, the state of the art in the evaluation of the flocculation rate of these two systems is reviewed. Special emphasis is made on the differences between suspensions and emulsions. In the case of suspensions, the stability ratio is commonly evaluated from the initial slope of the absorbance as a function of time under diffusive and reactive conditions. Puertas and de las Nieves (1997) developed a theoretical approach that allows the determination of the flocculation rate from the variation of the turbidity of a sample as a function of time. Here, suitable modifications of the experimental procedure and the referred theoretical approach are implemented in order to calculate the values of the stability ratio and the flocculation rate corresponding to a dodecane-in-water nanoemulsion stabilized with sodium dodecyl sulfate. Four analytical expressions of the turbidity are tested, basically differing in the optical cross section of the aggregates formed. The first two models consider the processes of: a) aggregation (as described by Smoluchowski) and b) the instantaneous coalescence upon flocculation. The other two models account for the simultaneous occurrence of flocculation and coalescence. The latter reproduce the temporal variation of the turbidity in all cases studied (380 ≤ [NaCl] ≤ 600 mM), providing a method of appraisal of the flocculation rate in nanoemulsions.

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“…For centrosymmetric materials SH is generated at the surface of nano-particles, because symmetry is broken at that interface as Wang has demonstrated experimentally for the first time [2]. SHG has been applied to study the surface and buried micro-structure of colloidal nano-particles [3][4][5][6][7][8][9][10][11][12][13] or as probing technique in bio-physical experiments [14][15][16][17][18]. We have used SHG to determine the nonlinear susceptibility ( ) 2 χ of a thin layer of Malachite Green [19], to study the layer of oriented water near polystyrene particles [20] and the organization of polyelectrolyte chains, depending on the salt concentration of the solvent [21].…”

Section: Introductionmentioning

confidence: 99%

Plasmonic enhancement of second harmonic generation on metal coated nanoparticles

Wunderlich¹,

Peschel²

2013

Opt. Express

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Second Harmonic Generation (SHG) is a widely used tool to study surfaces. Here we investigate SHG from spherical nanoparticles consisting of a dielectric core (radius 100 nm) and a metallic shell of variable thickness. Plasmonic resonances occur that depend on the thickness of the nanoshells and boost the intensity of the Second Harmonic (SH) signal. The origin of the resonances is studied for the fundamental harmonic and the second harmonic frequencies. Mie resonances at the fundamental harmonic frequency dominate resonant effects of the SHsignal at low shell thickness. Resonances excited by a dipole emitting at SH frequency close to the surface explain the enhancement of the SHG-process at a larger shell thickness. All resonances are caused by surface plasmon polaritons, which run on the surface of the spherical particle and are in resonance with the circumference of the sphere. Because their wavelength critically depends on the properties of the metallic layer SHG resonances of core-shell nanoparticles can be easily tuned by varying the thickness of the shell. References and links1. Y. Shen, "Surface 2nd harmonic-generation -a new technique for surface studies," Annu. Rev. Mater. Sci. 16(1), 69-86 (1986). 2. H. Wang, E. C. Y. Yan, E. Borguet, and K. B. Eisenthal, "Second harmonic generation from the surface of centrosymmetric particles in bulk solution," Chem. Phys. Lett. 259(1-2), 15-20 (1996). 3. E. C. Y. Yan, Y. Liu, and K. B. Eisenthal, "New method for determination of surface potential of microscopic particles by second harmonic generation," J. Chem. Phys. B 102(33), 6331-6336 (1998 11-14 (2011). 14. J. Griffin, A. K. Singh, D. Senapati, E. Lee, K. Gaylor, J. Jones-Boone, and P. C. Ray, "Sequence-Specific HCV RNA Quantification Using the Size-Dependent Nonlinear Optical Properties of Gold Nanoparticles," Small 5 (

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Surface Structure of Sodium Dodecyl Sulfate Surfactant and Oil at the Oil-in-Water Droplet Liquid/Liquid Interface: A Manifestation of a Nonequilibrium Surface State

Cited by 128 publications

References 83 publications

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Nanoemulsion stability: Experimental evaluation of the flocculation rate from turbidity measurements

Plasmonic enhancement of second harmonic generation on metal coated nanoparticles

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