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Self‐assembled Monolayers of Alkylphosphonic Acids on Aluminum Oxide Surfaces – A Theoretical Study
Author(s) -
Luschtinetz Regina,
Oliveira Augusto F.,
Duarte Hélio A.,
Seifert Gotthard
Publication year - 2010
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201000016
Subject(s) - monolayer , alkyl , adsorption , molecule , chemistry , tilt (camera) , self assembled monolayer , crystallography , density functional theory , boehmite , computational chemistry , aluminium , organic chemistry , geometry , biochemistry , mathematics
Density‐functional based calculations were used to investigate self‐assembled monolayers of different alkylphosphonic acids on corundum α ‐Al 2 O 3 (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.