Interference Effects in Sum Frequency Spectra from Monolayers on Composite Dielectric/Metal Substrates

Lambert, Alex G.; Neivandt, David J.; Briggs, Adam M.; Usadi, E.; Davies, Paul B.

doi:10.1021/jp014240s

Cited by 54 publications

(107 citation statements)

References 48 publications

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“…Interestingly, the phase (observed as the peak polarity and shape) of the r − modes in the sps and ppp spectra exhibit a strong dependence on the Leu position, while the phases of the other modes are mostly unaffected. Pronounced phase variability of the r − modes versus the r þ modes has also been observed before in phase studies of methyl stretching modes in peptide spectra and polystyrene (55,56). The intensities of all observed modes vary significantly with the leucine positions.…”

Section: Methodssupporting

confidence: 77%

Sum frequency generation and solid-state NMR study of the structure, orientation, and dynamics of polystyrene-adsorbed peptides

Weidner

Breen

et al. 2010

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

134

221

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The power of combining sum frequency generation (SFG) vibrational spectroscopy and solid-state nuclear magnetic resonance (ssNMR) spectroscopy to quantify, with site specificity and atomic resolution, the orientation and dynamics of side chains in synthetic model peptides adsorbed onto polystyrene (PS) surfaces is demonstrated in this study. Although isotopic labeling has long been used in ssNMR studies to site-specifically probe the structure and dynamics of biomolecules, the potential of SFG to probe side chain orientation in isotopically labeled surface-adsorbed peptides and proteins remains largely unexplored. The 14 amino acid leucine-lysine peptide studied in this work is known to form an α-helical secondary structure at liquid-solid interfaces. Selective, individual deuteration of the isopropyl group in each leucine residue was used to probe the orientation and dynamics of each individual leucine side chain of LKα14 adsorbed onto PS. The selective isotopic labeling methods allowed SFG analysis to determine the orientations of individual side chains in adsorbed peptides. Side chain dynamics were obtained by fitting the deuterium ssNMR line shape to specific motional models. Through the combined use of SFG and ssNMR, the dynamic trends observed for individual side chains by ssNMR have been correlated with side chain orientation relative to the PS surface as determined by SFG. This combination provides a more complete and quantitative picture of the structure, orientation, and dynamics of these surface-adsorbed peptides than could be obtained if either technique were used separately.protein | surface | isotope labels | solid-liquid interface

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Section: Methodssupporting

confidence: 77%

Sum frequency generation and solid-state NMR study of the structure, orientation, and dynamics of polystyrene-adsorbed peptides

Weidner

Breen

et al. 2010

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

134

221

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“…12-iii of the preceding paper. In comparison with the modeling results proposed by Lambert et al, 18 the present simulation can either exactly predict the line shape of the peaks or give the relative intensity of each peak. As discussed in the preceding paper, when there are several contributions to the interference phenomenon it should be noted that periodic changes in the spectral features do not exist due to the complicated nature of the overall interference as shown above.…”

Section: -7mentioning

confidence: 61%

“…All these effects taken together determine the thicknessdependent interference effect for the ppp polarization combination. 18 …”

Section: -3mentioning

confidence: 99%

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Interference effects in the sum frequency generation spectra of thin organic films. II: Applications to different thin-film systems

Tong

Zhao

et al. 2010

The Journal of Chemical Physics

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In this paper, the results of the modeling calculations carried out for predicting the interference effects expected in the sum frequency generation ͑SFG͒ spectra of a specific thin-layer system, described in the accompanying paper, are tested by comparing them with the experimental spectra obtained for a real thin-layer film comprising an organic monolayer/variable thickness dielectric layer/gold substrate. In this system, two contributions to the SFG spectra arise, a resonant contribution from the organic film and a nonresonant contribution from the gold substrate. The modeling calculations are in excellent agreement with the experimental spectra over a wide range of thicknesses and for different polarization combinations. The introduction of another resonant monolayer adjacent to the gold substrate and with the molecules having a reverse orientation has a significant affect on the spectral shapes which is predicted. If a dielectric substrate such as CaF 2 is used instead of a gold substrate, only the spectral intensities vary with the film thickness but not the spectral shapes. The counterpropagating beam geometry will change both the thickness dependent spectral shapes and the intensity of different vibrational modes in comparison with a copropagating geometry. The influences of these experimental factors, i.e., the molecular orientational structure in the thin film, the nature of the substrate, and the selected incident beam geometry, on the experimental SFG spectra are quantitatively predicted by the calculations. The thickness effects on the signals from a SFG active monolayer contained in a thin liquid-layer cell of the type frequently used for in situ electrochemical measurements is also discussed. The modeling calculation is also valid for application to other thin-film systems comprising more than two resonant SFG active interfaces by appropriate choice of optical geometries and relevant optical properties.

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“…It has been shown that when a monolayer alkyl film is deposited on thin mica sheets supported on a gold substrate, i.e. analogous to the Synovene film separated from the steel surface by the ZDDP layer as investigated here, the spectrum arises from an interference effect between the metal substrate and the surfactant film as described above [20,21]. A more likely explanation then is that although the actual Synovene layer may be the same thickness as on the steel surface, the combined thickness of the Synovene layer and the ZDDP layer is greater than the Synovene layer alone giving rise to a different SFG response, i.e.…”

Section: Resultsmentioning

confidence: 80%

The Adsorption of Synovene on ZDDP Wear Tracks: A Sum Frequency Generation (SFG) Vibrational Spectroscopy Study

et al. 2016

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The adsorption of the lubricant additive Synovene on steel and on ZDDP/steel wear tracks from base oil has been investigated by sum frequency generation (SFG) vibrational spectroscopy, an interface specific technique. SFG spectra (resonances) were investigated in the C-H stretching region and arise from the aliphatic chains of the palm oil constituent of Synovene. The observation of SFG spectra means that Synovene is adsorbed at the oil/metal and at the oil/ZDDP/metal interfaces and that the aliphatic chains of Synovene have a net polarisation order with respect to the surface. The intense spectrum observed when the film is first formed decreases in intensity with increasing temperature. It is proposed that this is due to a decrease in film thickness as the film tends towards monolayer thickness. A dependence of the intensity and shape of SFG resonances on film thickness due to a thickness-dependent interference effect has been observed in other thin film systems, most notably lipid films on gold. Supporting evidence for the film thickness hypothesis comes from examining the spectra of different thickness films of palmitic acid on steel, one of the constituents of Synovene. The spectra on the wear track are less intense and less reproducible than on the bare metal. After periods of several days at room temperature the spectra on both surfaces gain in intensity implying a return to thicker layers of Synovene under cold conditions.

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Interference Effects in Sum Frequency Spectra from Monolayers on Composite Dielectric/Metal Substrates

Cited by 54 publications

References 48 publications

Sum frequency generation and solid-state NMR study of the structure, orientation, and dynamics of polystyrene-adsorbed peptides

Sum frequency generation and solid-state NMR study of the structure, orientation, and dynamics of polystyrene-adsorbed peptides

Interference effects in the sum frequency generation spectra of thin organic films. II: Applications to different thin-film systems

The Adsorption of Synovene on ZDDP Wear Tracks: A Sum Frequency Generation (SFG) Vibrational Spectroscopy Study

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