Adsorption of Alkanethiols on Gold Surfaces: PM-IRRAS Study of the Influence of Terminal Functionality on Alkyl Chain Orientation
2013
Elzein, Tamara | Fahs, Ahmad | Brogly, Maurice | Elhiri, Amina | Lepoittevin, Bénédicte | Roger, Philippe | Planchot, Veronique, V. | Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA)) | Laboratoire de Photochimie et d'ingénierie macromoléculaires - LPIM - UR4567 (LPIM) ; Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Matériaux et Nanosciences Grand-Est (MNGE) ; Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS) | Université Paris-Sud - Paris 11 (UP11) | Unité de recherche sur les Biopolymères, Interactions Assemblages (BIA) ; Institut National de la Recherche Agronomique (INRA) | 3M; French Research Agency ANR [ACI NR183 BIOSYAMI]
International audience
Mostrar más [+] Menos [-]Inglés. The present paper focuses on a simplified method to study the orientation and the anisotropy of two different alkanethiols self-assembled monolayers on gold surfaces. The alkanethiols of interest vary only by their terminal functionalities (COOH and COOCH3), thus allowing one to highlight the influence of these ending chemical groups on the final orientation of the adsorbed molecules. 11-Mercaptoundecanoic acid [HS-(CH2)10-COOH] and the methyl-11-mercaptoundecanoate [HS-(CH2)10-COOCH3] were grafted under adequate conditions to obtain a high grafting density on gold substrates. These latter, before and after the alkanethiol adsorption, were analyzed mainly by the polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) technique to access orientation angles, and by atomic force microscopy (AFM) to check the homogeneity of the grafted layer. By applying an original PM-IRRAS simplified method, the results showed an orientation closer to the normal of the surface plane in the case of the acid thiol compared with the ester one, which is probably because of the lateral hydrogen bonds established between the adjacent COOH functions. This method offers a direct and simple way to quantify the orientation angles in the alkanethiol nanofilms.
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