Carboxylic Acid- and Ester-Functionalized Siloxane Scaffolds on Glass Studied by Broadband Sum Frequency Generation

Voges, Andrea B.; Al‐Abadleh, Hind A.; Musorrafiti, Michael J.; Bertin, Paul; Nguyen, SonBinh T.; Geiger, Franz M.

doi:10.1021/jp046564x

Cited by 79 publications

(129 citation statements)

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“…2) that occupy different chemical environments and orientations. These spectral assignments are consistent with vibrational sum-frequency literature in the C-H region (19,32,40).…”

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

confidence: 89%

“…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%

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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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“…2) that occupy different chemical environments and orientations. These spectral assignments are consistent with vibrational sum-frequency literature in the C-H region (19,32,40).…”

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

confidence: 89%

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

confidence: 95%

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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“…Like the α-pinene SFG spectrum, the SFG response is dominated by one peak, which now occurs at 2950 cm −1 , while the SFG signal contribution at 2880 cm −1 is not shifted from that of unreacted α-pinene. In addition, the SFG spectrum of the α-pinene-derived secondary organic aerosol particles on the filter exhibits some signal contribution at 2920 cm −1 , which is characteristic of methylene asymmetric CH stretches in alkyl chains (Voges et al, 2004;Buchbinder et al, 2010b). Given the strong asymmetric CH stretching contributions observed for the α-pinenederived secondary organic aerosol particles, we conclude that the chemical composition of the particles is related to that of α-pinene in the sense that it contains rigidly arranged methyl groups.…”

Section: Vibrational Responses Of Model and Naturalmentioning

confidence: 73%

Contrasting organic aerosol particles from boreal and tropical forests during HUMPPA-COPEC-2010 and AMAZE-08 using coherent vibrational spectroscopy

et al. 2011

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Abstract. We present the vibrational sum frequency generation spectra of organic particles collected in a boreal forest in Finland and a tropical forest in Brazil. These spectra are compared to those of secondary organic material produced in the Harvard Environmental Chamber. By comparing coherent vibrational spectra of a variety of terpene and olefin reference compounds, along with the secondary organic material synthesized in the environmental chamber, we show that submicron aerosol particles sampled in Southern Finland during HUMPPA-COPEC-2010 are composed to a large degree of material similar in chemical composition to synthetic α-pinene-derived material. For material collected in Brazil as part of AMAZE-08, the organic component is found to be chemically complex in the coarse mode but highly uniform in the fine mode. When combined with histogram analyses of the isoprene and monoterpene abundance recorded during the HUMPPA-COPEC-2010 and AMAZE-08 campaigns, the findings presented here indicate that if air is rich in monoterpenes, submicron-sized secondary aerosol particles that form under normal OH and O 3 concentration levels can be described in terms of their hydrocarbon content as being similar to α-pinene-derived model secondary orCorrespondence to: F. M. Geiger (geigerf@chem.northwestern.edu) ganic aerosol particles. If the isoprene concentration dominates the chemical composition of organic compounds in forest air, then the hydrocarbon component of secondary organic material in the submicron size range is not simply wellrepresented by that of isoprene-derived model secondary organic aerosol particles but is more complex. Throughout the climate-relevant size range of the fine mode, however, we find that the chemical composition of the secondary organic particle material from such air is invariant with size, suggesting that the particle growth does not change the chemical composition of the hydrocarbon component of the particles in a significant way.

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“…the dynamics of rotation in the interfacial plane differ from the out-of-plane orientational motions. [15][16][17][18] Second harmonic generation (SHG) and sum frequency generation (SFG), [11][12][13][14][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] as second-order spectroscopies, are interface specific, including buried interfaces that are accessible to light. Second harmonic generation (SHG) depends primarily on the electronic properties of the interfacial molecules whereas SFG is sensitive to molecular vibrations when one of the incident beams is in the infrared.…”

Section: Introductionmentioning

confidence: 99%

Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation

et al. 2008

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The first time-resolved experiments in which interfacial molecules are pumped to excited electronic states and probed by vibrational sum frequency generation (SFG) are reported. This method was used to measure the out-of-plane rotation dynamics, i.e. time dependent changes in the polar angle, of a vibrational chromophore of an interfacial molecule. The chromophore is the carbonyl group, the rotation observed is that of the sCdO bond axis, with respect to the interfacial normal, and the interfacial molecule is coumarin 314 (C314) at the air/water interface. The orientational relaxation time was found to be 220 ( 20 ps, which is much faster than the orientational relaxation time of the permanent dipole moment axis of C314 at the same interface, as obtained from pump-second harmonic probe experiments. Possible effects on the rotation of the sCdO bond axis due to the carbonyl group hydrogen bonding with interfacial water are discussed. From the measured equilibrium orientation of the permanent dipole moment axis and the carbonyl axis, and knowledge of their relative orientation in the molecule, the absolute orientation of C314 at the air/water interface is obtained.

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Carboxylic Acid- and Ester-Functionalized Siloxane Scaffolds on Glass Studied by Broadband Sum Frequency Generation

Cited by 79 publications

References 50 publications

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Contrasting organic aerosol particles from boreal and tropical forests during HUMPPA-COPEC-2010 and AMAZE-08 using coherent vibrational spectroscopy

Orientational Motions of Vibrational Chromophores in Molecules at the Air/Water Interface with Time-Resolved Sum Frequency Generation

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