Sum frequency generation and second harmonic generation observation of orientation of 3-Aminopropyltriethoxysilane on the SiO₂ substrates for biosensor

Abstract

The orientation and density of 3-Aminopropyltriethoxysilane (APTES) on the substrate is very important in adsorption efficient, stability and density of biomolecules. This orientation definition is difficult to be done by other methods such as AFM observation and IR spectroscopy. In this research, I have investigated the layers and orientation of APTES molecules on the Si02 substrates by observing second order nonlinear generation spectroscopy and microscopy. Sum frequency generation and second harmonic generation are very sensitive to monolayer of adsorbates on the surfaces and interfaces. The incident polarization dependence and incident angle dependence of sum frequency generation and second harmonic generation will be combined with microscope. With this system, the distribution of APTES on large area surface will be seen.