Molecular Grafting to Silicon Surfaces in Air Using Organic Triazenes as Stable Diazonium Sources and HF as a Constant Hydride-Passivation Source

Abstract

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 spontaneous 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 R-triazene and ω-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 NOBF 4 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.

Highly Luminescent Covalently Linked Silicon Nanocrystal/Polystyrene Hybrid Functional Materials: Synthesis, Properties, and Processability

“…For example: Tour and co-workers designed an effi cient surface grafting approach on hydride-terminated silicon fi lm surface using diazonium sources that leads to the formation of mono-and multilayers (i.e., oligomers and polymers). [50][51][52] Xu et al investigated surface initiated atom transfer radical polymerization (ARTP) on Si surfaces derived from mono layer modifi cation of hydride and halogen terminated silicon and effectively induced the formation of polymer brushes grafted surface. [ 53,54 ] Similarly, Zhang et al reported a rapid grafting method to grow thick and dense polymer brushes on silicon using a multiple-step functionalization including UV-induced hydrosilylation followed by rare metal catalyzed polymerization.…”

Functional Covalent Chemistry of Carbon Nanotube Surfaces

“…[144] The use of either triazene (converted into diazonium in situ in the presence of HF) [145] or oligo(phenylene ethynylene) aryldiazonium salts [146] has also facilitated the covalent anchoring of functionalized SWNTs onto silicon surfaces, producing durable Si-SWNT nonmetallic molecular junctions useful for developing molecular electronic devices that do not possess metal electrodes in direct contact with molecular species and which may therefore obviate the need for metallic filaments. [147] Moreover, the Tour group also devised an environmentally friendly methodology [148] for exfoliating and uniformly functionalizing SWNTs as individual tubes by grinding them for minutes at room temperature with aryldiazonium salts in the presence of ionic liquids and K 2 CO 3 (Fig. 10).…”

Graphite‐Grafted Silicon Nanocomposite as a Negative Electrode for Lithium‐Ion Batteries

“…[22] In another related study, aryldiazonium salts, generated from aryltriazenes, were used to link carbon nanotubes to a silicon substrate. [23] In these two cases, a flat substrate was used instead of a powder to graft the initial aminophenyl layer. The materials prepared in this work were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electron-probe microanalysis (EPMA).…”