Infrared spectroscopic studies of self-assembled monolayers (SAMs) on gold: Structural characterization and water adsorption measurements

PAC Gym

Self-assembled monolayers (SAMs) have numerous applications in fields such as nanotechnology and the materials sciences. SAMs are used to alter surface properties for drug delivery devices, molecular recognition, gas adsorption, and wetting experiments. Research in our group is focused on characterizing gas adsorption on SAMs using infrared spectroscopy. SAMs were grown on gold-coated slides by immersing the slides in solutions of various thiols. Humidified nitrogen gas was delivered to SAMs of various terminal groups. Experiments with relative humidity effects on SAMs show a water layer binds to the terminal groups of the hydrophilic monolayers while SAMs with a hydrophobic terminal group did not show a hydration layer being formed. The structural order of the adsorbed molecule is an important characteristic of the SAM itself. Polarization-Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) was used to characterize the structural order and molecular packing of the SAM. Optical tensiometry was used to observe water contact angles and characterize hydrophobic/hydrophilic properties of the SAMs.