Improved assignment of vibrational modes in sum-frequency spectra in the C H stretch region for surface-bound C18 alkylsilanes

Quast, Arthur D.; Wilde, Nathan C.; Matthews, Sam S.; Maughan, Scott T.; Castle, Steven L.; Patterson, James E.

doi:10.1016/j.vibspec.2012.03.003

Cited by 16 publications

(19 citation statements)

References 51 publications

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“…Experiments at polyacrylic brushes 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 symmetric stretch at 2872 cm -1 , the asymmetric stretch at 2959 cm -1 and the Fermi resonance between the symmetric stretch and the overtone of the CH 3 bend at 2929 cm -1 . These frequencies are close to those found for C 18 siloxanes on fused silica or glass 34,35 . The approximate centre of inversion between the two CH 2 groups in an all-trans propyl chain prevents the generation of a sum frequency signal from these groups 26,36,37 .…”

Section: Resultssupporting

confidence: 85%

Stabilization of Insulin by Adsorption on a Hydrophobic Silane Self-Assembled Monolayer

et al. 2015

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The interaction between many proteins and hydrophobic functionalized surfaces is known to induce β-sheet and amyloid fibril formation. In particular, insulin has served as a model peptide to understand such fibrillation, but the early stages of insulin misfolding and the influence of the surface have not been followed in detail under the acidic conditions relevant to the synthesis and purification of insulin. Here we compare the adsorption of human insulin on a hydrophobic (-CH3-terminated) silane self-assembled monolayer to a hydrophilic (-NH3(+)-terminated) layer. We monitor the secondary structure of insulin with Fourier transform infrared attenuated total reflection and side-chain orientation with sum frequency spectroscopy. Adsorbed insulin retains a close-to-native secondary structure on both hydrophobic and hydrophilic surfaces for extended periods at room temperature and converts to a β-sheet-rich structure only at elevated temperature. We propose that the known acid stabilization of human insulin and the protection of the aggregation-prone hydrophobic domains on the insulin monomer by adsorption on the hydrophobic surface work together to inhibit fibril formation at room temperature.

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Section: Resultssupporting

confidence: 85%

Stabilization of Insulin by Adsorption on a Hydrophobic Silane Self-Assembled Monolayer

et al. 2015

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“…In Figure , the C4 Quat ssp spectrum (Figure (A)) contained a prominent methylene asymmetric stretch peak (CH 2 AS) at ∼2907 cm –1 . , The other CH stretches are less prominent (peak assignments and positions are reported in the SI). ,,, The methyl asymmetric stretch was not evident in the ssp spectrum compared to other vibrational modes, especially to the methylene groups that dominated the surface. In the C12 Quat ssp spectrum, sharp peaks of the terminal methyl symmetric (CH 3 SS) (∼2884 cm –1 ) and methyl symmetric stretch split by the Fermi resonance interaction with the methyl bending mode (CH 3 FR) (∼2945 cm –1 ) are observed. , In the C4 Quat ppp spectrum (Figure (B)), CH 3 SS, CH 2 AS, and methylene asymmetric stretch (CH 3 AS) vibrational modes are observed at ∼2880, ∼2917, and ∼2972 cm –1 , respectively. ,, In addition, the CH 3 AS present is more evident in the ppp spectrum while it is not evident in the ssp spectrum; the possible reason for this observation can be because most of the AS vibrational modes are not aligned along with the s-polarized lights of the visible and SF beams in the ssp polarization.…”

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confidence: 99%

“…As the polarization of both incident beams is parallel to the incident plane (p-polarized), AS stretches are probed by the p-polarized visible and IR beams while only p-polarized SFG signal is recorded. This could be because CH 3 AS vibrational modes lie parallel to the incident plane. , On the other hand, peaks of the CH 3 SS and CH 3 AS peaks are observed and prominent in the C12 Quat ppp spectrum. ,, Tables S3 and S4 summarize the peak positions from fittings and assignments, which are available in the SI.…”

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confidence: 99%

Direct Observation of Adsorption Morphologies of Cationic Surfactants at the Gold Metal–Liquid Interface

Khan

Singh

Sharma

et al. 2020

J. Phys. Chem. Lett.

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Understanding interfacial phenomena is important in processes like corrosion, catalysis, and electrochemical reactions. Specifically, in corrosion inhibition, the assembly of adsorbed surfactants at metal–water interfaces in well-packed, ordered layers is desired. We provide direct evidence of the role of alkyl tails of surfactants in the formation of ordered adsorbed layers at metal–water interfaces. We have employed surface-specific sum frequency generation (SFG) spectroscopy to probe the in situ adsorption and self-assembly of cationic surfactants, alkyldimethylbenzyl ammonium bromides of tail lengths n = 4 (C4) and 12 (C12), without any applied potential or stimulus, at the gold–water interface. Our SFG measurements show that C12 Quat adsorbs as an ordered monolayer, whereas C4 Quat adsorbs in a disordered monolayer. All-atom molecular dynamics (MD) simulations of these surfactants corroborate with SFG results. These findings provide new insights on how hydrophobic interactions between alkyl tails of surfactants affect their self-assembly at metal–water interfaces.

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“…The contact angles and the thickness increased with increasing the immersion times, and levelled off over 120 minutes. The asymmetric stretching vibration modes due to CH 2 (ν as CH 2 ) were appeared at around 2920-2930 cm -1 ; and the symmetric stretching vibration modes due to CH 2 (ν s CH 2 ) were appeared at around 2850-2860 cm -1 [3]. The wave number of the ν as CH 2 shifted to the red direction with increasing the immersion times, and the red shift levelled off over 120 minutes, as shown in Fig.…”

Section: Tuts-cam By the Standard Techniquementioning

confidence: 78%

Control of the molecular density in a chemically adsorbed thiophene system monolayer

Tanaka

Ohtake

Ogawa

2013

MATEC Web of Conferences

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Abstract. Chemically absorbed monolayers (CAM) of thienyl functionalized n-alkyltrichlorosilane 11-(3-thienyl) undecyltrichlorosilane (TUTS) have been prepared with two methods which are the standard technique (TUTS-STD) and the twice adsorption method (TUTS-TAM). The existence of TUTS-CAM was confirmed with water contact angle measurements, calculation of thickness with ellipsometry, fourier transform infrared reflection adsorption spectroscopy (FTIR-RAS). Here are described is the comparison of TUTS-STD and TUTS-TAM characterized by using Electron Spectroscopy for Chemical Analysis (ESCA) and ultraviolet visible (UV-vis) absorption spectroscopy. TUTS-TAM showed more densely packing than TUTS-STD by these measurements. Moreover, these TUTS-CAM polymerized by chemical oxidative polymerization and UV-Vis absorption spectra was measured to confirm the conjugated bond length of the polymerized thienyl groups. UV-vis spectra of the polymerized TUTS-CAM showed a new broad absorbance band at longer wavelength than 700nm.

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Improved assignment of vibrational modes in sum-frequency spectra in the C H stretch region for surface-bound C18 alkylsilanes

Cited by 16 publications

References 51 publications

Stabilization of Insulin by Adsorption on a Hydrophobic Silane Self-Assembled Monolayer

Stabilization of Insulin by Adsorption on a Hydrophobic Silane Self-Assembled Monolayer

Direct Observation of Adsorption Morphologies of Cationic Surfactants at the Gold Metal–Liquid Interface

Control of the molecular density in a chemically adsorbed thiophene system monolayer

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