Self-assembly of aminosilane layers: Determination of surface density of the amine group through a reversible chemical reaction

Abstract

The surface of a fused silica and oxidized silicon wafer (SiO2/Si(100)) was treated with (3-aminopropyl)triethoxysilane in solution. The silane coupling agent (SCA) produces multilayers with variable thickness (6-100 Angstrom) depending upon the dipping time. The aminosilane layers were allowed to react with 4-nitrobenzaldehyde, and formation of che corresponding imine was confirmed by UV-vis spectroscopy. In aqueous medium the imine was easily hydrolyzed to regenerate the amine group and the aldehyde. Surface density of the amine was calculated from the amount of produced 4-nitrobenzaldehyde. Tilt angles of the chromophore, the imine, obtained from the surface density and A(surf), absorbance of the derviatized substrate, are 23-32 degrees.