Molecular grafting to silicon surfaces in air using organic triazenes as stable diazonium sources and HF as a constant hydride-passivation source

Aryl molecules were covalently grafted to hydride-passivated Si(100) surfaces (Si-H) by the in situ conversion of aryldiethyltriazenes into aryldiazonium salts using 2% HF, followed by sponiancous surface grafting of the aryl species to the silicon surface. Major advances are as follows: first, reactive diazonium species need not be isolated, and second, by using aqueous HF as the triazene-to-diazonium conversion promoter, the entire process can be carried out in air since any Si-oxide is continuously converted to the Si-H species. Molecular layers from a monolayer to 200 nm thick could be formed depending on the reaction conditions used. In one case where the molecule bore an alpha-triazene and pi-aniline (6), after grafting of the molecular layer onto Si-H via the triazene, the remaining aniline moiety was converted into a diazonium salt in situ with NOBF4 and then permitted to react with functionalized single-walled carbon nanotubes (SWNTs), thereby covalently attaching nanotubes to the silicon surface using, the aryl molecular layer as a tethering unit.