Self-assembled silanes and the thiol functionalization of surfaces

The relative thickness and coverage of the silanes, mercaptopropyltrimethoxysilane and 1-(trifluoroacetato-)-11-trichlorosilyl-undecane subsequent to reaction on silicon surfaces has been assessed by X-ray photoelectron spectroscopic analysis. Use of the probe, N-pentafluorophenyl-N′-iodoacetyl hydrazide, allows an estimation of the availability of thiol groups on the substrate surface following reaction in air and in O2-free conditions. Although the trimethoxysilane generates multilayer structures, it is only capable of attaching 3.5 times less probe than the fluorine-containing silane. The results of these experiments confirm that 1-(trifluoroacetato-)-11-trichlorosilyl-undecane is a much more effective linking agent for the immobilization of biomolecules to substrate surfaces.