Self-assembled monolayers of alkylphosphonic acids on aluminum oxide surfaces – A theoretical study

Regina Luschtinetz (1) , Augusto Faria Oliveira (1) , Hélio Anderson Duarte (2) , Gotthard Seifert (1)

1 Physikalische Chemie
2 ICEx - Departamento de Física

Density-functional based calculations have been 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 have been considered. In addition, the organization of single adsorbed molecules has been 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, indicating 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 have been obtained for mono-, bi-, and tridentate adsorptions. Hence, the coordination mode cannot be characterized by the molecule tilting.

Mots clés: Physical Sciences

Regina Luschtinetz, Augusto Faria Oliveira, Hélio Anderson Duarte, Gotthard Seifert. Self-assembled monolayers of alkylphosphonic acids on aluminum oxide surfaces – A theoretical study. Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, 2010, 636 (8), pp.1506. ⟨10.1002/zaac.201000016⟩. ⟨hal-00552441⟩