Self-assembled Monolayers of Alkylphosphonic Acids on Aluminum Oxide Surfaces - A Theoretical Study

• Published in: ZAAC - Journal of Inorganic and General Chemistry Vol. 636; no. 8; pp. 1506 - 1512
• Main Authors: Luschtinetz, Regina, Oliveira, Augusto F., Duarte, Hélio A., Seifert, Gotthard
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.08.2010; WILEY‐VCH Verlag; Wiley-VCH Verlag
• Subjects: Adsorption; Alkylphosphonic acids; Aluminium; Density functional calculations; Self-assembled monolayers; Physical Sciences
• ISSN: 0044-2313; 1521-3749
• DOI: 10.1002/zaac.201000016

Density‐functional based calculations were used to investigate self‐assembled monolayers of different alkylphosphonic acids on corundum α‐Al2O3 (0001), bayerite β‐Al(OH)3 (001) and boehmite γ‐AlOOH (010) surface models. Mono‐, bi‐, and tridentate adsorption modes were considered. In addition, the organization of single adsorbed molecules was compared to the organization at full surface coverage. The height (thickness) of the self‐assembled monolayers is always shorter than the length of the phosphonic acid molecules due to tilting of the alkyl chains. Tilt angles at full surface coverage are very similar to the tilt angle of a single adsorbed molecule, which indicates that the density of the self‐assembled monolayers is limited by the density of adsorption sites. The lateral interactions between alkyl chains are evidenced by small torsions of the adsorbed molecules, which may serve to minimize the repulsion forces between interchain hydrogen atoms. Similar tilt angles were obtained for mono‐, bi‐, and tridentate adsorptions. Hence, the coordination mode cannot be characterized by the molecule tilting.