ORGANOFUNCTIONALIZATION OF TIO2(110) - (3,3,3-TRIFLUOROPROPYL)TRIMETHOXYSILANE ADSORPTION

The interaction of (3,3,3-trifluoropropyl)trimethoxysilane (FPTS), or CF3CH2CH2Si(OCH3)(3), with TiO2(110) has been studied using temperatur e-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and static secondary ion spectrometry (SSIMS). The FPTS dissociativel y adsorbed on the TiO2(110), forming adsorbed CF3CH2CH2SiOCH3 and -OCH 3 groups. An isotopically (O-18) enriched surface was used to show tha t the CF3CH2CH2SiOCH3 species was bound to the surface via two Si-O(su rface) bonds, by using SSIMS to identify (SiO)-O-18 bond formation. Th e two -OCH3 groups eliminated from the FPTS were bound to surface Ti4 sites. When no surface hydroxyls were present, the -OCH3 ligands, whe ther bound to Ti4+ or Si, decomposed at similar to 550-600 K to form m ethane, formaldehyde, and methanol gases. In the presence of water, th e -OCH3 bound to Ti4+ sites combined with the surface hydroxyls and de sorbed as methanol at similar to 300K. The CF3CH2CH2-ligand decomposed at similar to 620 K via two elimination pathways. Either the H was el iminated from the beta-carbon to form CF3CH=CH2 gas or the CF3 group w as eliminated to release CH2-CH2 gas. This methoxysilane was more reac tive with TiO2(110) than several ethoxysilanes previously studied.