MOLECULAR-INTERACTIONS BETWEEN ORGANIZED, SURFACE-CONFINED MONOLAYERS AND VAPOR-PHASE PROBE MOLECULES .6. IN-SITU FTIR EXTERNAL REFLECTANCE SPECTROSCOPY OF MONOLAYER ADSORPTION AND REACTION CHEMISTRY

A new in-situ application of FTIR external reflectance spectroscopy (FTIR-ESR), which is useful for real-time evaluation of monolayer and multilayer adsorption and reaction chemistry at the vapor/solid interface at pressures near 1 atm, is described. The utility and versatility of the method is illustrated by two proof-of-concept experiments. The first experiment involves adsorption of H2N(CH2)9CH3 onto a naked Au substrate from the vapor phase. In-situ FTIR-ERS indicates that the amine forms a stable, ordered monolayer on the Au surface; that is, H2N(CH2)9CH3 self-assembles onto the Au surface from the vapor phase. The second experiment involves vapor-phase adsorption of a HS(C6H5)OH monolayer onto a naked Au surface, followed by an in-situ coupling reaction with [CH3(CH2)7](CH3)2SiCl. Real-time FTIR-ERS characterization of the organic bilayer is consistent with previously reported ex-situ FTIR-ERS results; however, kinetic data can be abstracted from the new in-situ data. The rate constant for the surface silane coupling reaction is estimated to be 0.30 min-1.