Interfacial assembly of lipopeptide surfactants on octyltrimethoxysilane-modified silica surface

Jiqian Wang, Donghui Jia, Kai Tao, Chengdong Wang, Xiubo Zhao, Mohammed Yaseen, Hai Xu, Guohe Que, John R.P. Webster, Jian R. Lu

Research output: Contribution to journalArticle

Abstract

The adsorption of a series of cationic lipopeptide surfactants, C14Kn (where C-14 denotes the myristic acyl chain and K-n represents n number of lysine residues) at the hydrophobic solid/water interface has been studied using spectroscopic ellipsometry (SE) and neutron reflection (NR). The hydrophobic C-8 surface was prepared by grafting a monolayer of octyltrimethoxysilane on the silicon surface. SE was used to follow the dynamic adsorption from these lipopeptide surfactants and the amount was found to undergo a fast increase within the first 2-3 min, followed by a much slower process tending to equilibration in the subsequent 15-20 min. Lipopetide surfactants with n = 1-4 showed similar dynamic features, indicating that the interaction between the acyl chain and the C-8 surface is the main driving force for adsorption. The saturation adsorption amount of C14Kn at the C-8/water interface was found to be inversely related to the increasing number of Lys residues in the head group due to the increase of steric hindrance and electrostatic repulsion between the head groups. Solution concentration had a significant effect on the initial adsorption rate, similar to the feature observed from nonionic surfactants CmEn. The structure of the adsorbed layers was studied by NR in conjunction with isotopic contrasts. The layer formed by the head groups of C14K1 was 10 angstrom thick, and those formed by C14K2, C14K3 and C14K4 head groups were all about 13 angstrom thick. In contrast, the thicknesses of the layers formed by hydrophobic tails of C14K1, C14K2 C14K3, and C14K4 were found to be 17, 13, 10, and 10 angstrom, respectively, resulting in the steady increase of area per molecule at the interface from 29 +/- 2 angstrom(2) for C14K1 to 65 +/- 2 angstrom(2) for C14K4. Thus, with an increase in the head group length, the molecules in the adsorbed layer tended to lie down upon adsorption.
Original languageEnglish
Pages (from-to)9684-9691
Number of pages8
JournalSoft Matter
Volume9
Issue number40
DOIs
Publication statusPublished - 9 Aug 2013
Externally publishedYes

Cite this

Wang, Jiqian ; Jia, Donghui ; Tao, Kai ; Wang, Chengdong ; Zhao, Xiubo ; Yaseen, Mohammed ; Xu, Hai ; Que, Guohe ; Webster, John R.P. ; Lu, Jian R. / Interfacial assembly of lipopeptide surfactants on octyltrimethoxysilane-modified silica surface. In: Soft Matter. 2013 ; Vol. 9, No. 40. pp. 9684-9691.
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abstract = "The adsorption of a series of cationic lipopeptide surfactants, C14Kn (where C-14 denotes the myristic acyl chain and K-n represents n number of lysine residues) at the hydrophobic solid/water interface has been studied using spectroscopic ellipsometry (SE) and neutron reflection (NR). The hydrophobic C-8 surface was prepared by grafting a monolayer of octyltrimethoxysilane on the silicon surface. SE was used to follow the dynamic adsorption from these lipopeptide surfactants and the amount was found to undergo a fast increase within the first 2-3 min, followed by a much slower process tending to equilibration in the subsequent 15-20 min. Lipopetide surfactants with n = 1-4 showed similar dynamic features, indicating that the interaction between the acyl chain and the C-8 surface is the main driving force for adsorption. The saturation adsorption amount of C14Kn at the C-8/water interface was found to be inversely related to the increasing number of Lys residues in the head group due to the increase of steric hindrance and electrostatic repulsion between the head groups. Solution concentration had a significant effect on the initial adsorption rate, similar to the feature observed from nonionic surfactants CmEn. The structure of the adsorbed layers was studied by NR in conjunction with isotopic contrasts. The layer formed by the head groups of C14K1 was 10 angstrom thick, and those formed by C14K2, C14K3 and C14K4 head groups were all about 13 angstrom thick. In contrast, the thicknesses of the layers formed by hydrophobic tails of C14K1, C14K2 C14K3, and C14K4 were found to be 17, 13, 10, and 10 angstrom, respectively, resulting in the steady increase of area per molecule at the interface from 29 +/- 2 angstrom(2) for C14K1 to 65 +/- 2 angstrom(2) for C14K4. Thus, with an increase in the head group length, the molecules in the adsorbed layer tended to lie down upon adsorption.",
author = "Jiqian Wang and Donghui Jia and Kai Tao and Chengdong Wang and Xiubo Zhao and Mohammed Yaseen and Hai Xu and Guohe Que and Webster, {John R.P.} and Lu, {Jian R.}",
year = "2013",
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Wang, J, Jia, D, Tao, K, Wang, C, Zhao, X, Yaseen, M, Xu, H, Que, G, Webster, JRP & Lu, JR 2013, 'Interfacial assembly of lipopeptide surfactants on octyltrimethoxysilane-modified silica surface' Soft Matter, vol. 9, no. 40, pp. 9684-9691. https://doi.org/10.1039/c3sm51271a

Interfacial assembly of lipopeptide surfactants on octyltrimethoxysilane-modified silica surface. / Wang, Jiqian; Jia, Donghui; Tao, Kai; Wang, Chengdong; Zhao, Xiubo; Yaseen, Mohammed; Xu, Hai; Que, Guohe; Webster, John R.P.; Lu, Jian R.

In: Soft Matter, Vol. 9, No. 40, 09.08.2013, p. 9684-9691.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Interfacial assembly of lipopeptide surfactants on octyltrimethoxysilane-modified silica surface

AU - Wang, Jiqian

AU - Jia, Donghui

AU - Tao, Kai

AU - Wang, Chengdong

AU - Zhao, Xiubo

AU - Yaseen, Mohammed

AU - Xu, Hai

AU - Que, Guohe

AU - Webster, John R.P.

AU - Lu, Jian R.

PY - 2013/8/9

Y1 - 2013/8/9

N2 - The adsorption of a series of cationic lipopeptide surfactants, C14Kn (where C-14 denotes the myristic acyl chain and K-n represents n number of lysine residues) at the hydrophobic solid/water interface has been studied using spectroscopic ellipsometry (SE) and neutron reflection (NR). The hydrophobic C-8 surface was prepared by grafting a monolayer of octyltrimethoxysilane on the silicon surface. SE was used to follow the dynamic adsorption from these lipopeptide surfactants and the amount was found to undergo a fast increase within the first 2-3 min, followed by a much slower process tending to equilibration in the subsequent 15-20 min. Lipopetide surfactants with n = 1-4 showed similar dynamic features, indicating that the interaction between the acyl chain and the C-8 surface is the main driving force for adsorption. The saturation adsorption amount of C14Kn at the C-8/water interface was found to be inversely related to the increasing number of Lys residues in the head group due to the increase of steric hindrance and electrostatic repulsion between the head groups. Solution concentration had a significant effect on the initial adsorption rate, similar to the feature observed from nonionic surfactants CmEn. The structure of the adsorbed layers was studied by NR in conjunction with isotopic contrasts. The layer formed by the head groups of C14K1 was 10 angstrom thick, and those formed by C14K2, C14K3 and C14K4 head groups were all about 13 angstrom thick. In contrast, the thicknesses of the layers formed by hydrophobic tails of C14K1, C14K2 C14K3, and C14K4 were found to be 17, 13, 10, and 10 angstrom, respectively, resulting in the steady increase of area per molecule at the interface from 29 +/- 2 angstrom(2) for C14K1 to 65 +/- 2 angstrom(2) for C14K4. Thus, with an increase in the head group length, the molecules in the adsorbed layer tended to lie down upon adsorption.

AB - The adsorption of a series of cationic lipopeptide surfactants, C14Kn (where C-14 denotes the myristic acyl chain and K-n represents n number of lysine residues) at the hydrophobic solid/water interface has been studied using spectroscopic ellipsometry (SE) and neutron reflection (NR). The hydrophobic C-8 surface was prepared by grafting a monolayer of octyltrimethoxysilane on the silicon surface. SE was used to follow the dynamic adsorption from these lipopeptide surfactants and the amount was found to undergo a fast increase within the first 2-3 min, followed by a much slower process tending to equilibration in the subsequent 15-20 min. Lipopetide surfactants with n = 1-4 showed similar dynamic features, indicating that the interaction between the acyl chain and the C-8 surface is the main driving force for adsorption. The saturation adsorption amount of C14Kn at the C-8/water interface was found to be inversely related to the increasing number of Lys residues in the head group due to the increase of steric hindrance and electrostatic repulsion between the head groups. Solution concentration had a significant effect on the initial adsorption rate, similar to the feature observed from nonionic surfactants CmEn. The structure of the adsorbed layers was studied by NR in conjunction with isotopic contrasts. The layer formed by the head groups of C14K1 was 10 angstrom thick, and those formed by C14K2, C14K3 and C14K4 head groups were all about 13 angstrom thick. In contrast, the thicknesses of the layers formed by hydrophobic tails of C14K1, C14K2 C14K3, and C14K4 were found to be 17, 13, 10, and 10 angstrom, respectively, resulting in the steady increase of area per molecule at the interface from 29 +/- 2 angstrom(2) for C14K1 to 65 +/- 2 angstrom(2) for C14K4. Thus, with an increase in the head group length, the molecules in the adsorbed layer tended to lie down upon adsorption.

U2 - 10.1039/c3sm51271a

DO - 10.1039/c3sm51271a

M3 - Article

VL - 9

SP - 9684

EP - 9691

JO - Soft Matter

JF - Soft Matter

SN - 1744-6848

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