Compact Titanium Oxycarbide: A New Substrate for Quantitative Analysis of Molecular Films by Means of Infrared Reflection Absorption Spectroscopy

Abstract

Titanium oxide–titanium carbide (TiOxCy) hybrid materials have tunable electronic properties ranging from semiconductive to semimetallic. They can therefore be employed in solar energy conversion applications and as potential substitute for carbon based electrocatalyst supports for use in fuel cells. Understanding of the optical properties of semimetallic TiOxCy is of great importance. In this paper we report on the optical properties of compact TiOxCy in the mid-IR spectral region. TiOxCy reflects the IR light similarly to metals and is therefore suitable as a new substrate for molecular adsorption studies with infrared reflection absorption spectroscopy. For the first time polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) is applied to study quantitatively at the submolecular level the structure and orientation of fatty acid molecules in monolayers adsorbed on the TiOxCy surface. The analysis of the IR band intensities provides information on the structure, packing, and orientation of the fatty acid molecules in the monolayer. The PM IRRA spectra provide evidence of an interaction between surface atoms and the carboxylic group leading to dissociation of the polar headgroup and bidentate canted coordination of the carboxylate at the TiOxCy surface.