Solution-based alkyne-azide coupling on functionalized Si(001) prepared under UHV conditions

TL;DR

This study demonstrates a method for creating organic bi-layers on silicon surfaces by combining UHV surface functionalization with solution-based click chemistry, enabling precise layer assembly without ambient exposure.

Contribution

It introduces a novel approach integrating UHV surface preparation with solution-phase click chemistry for silicon surface modification.

Findings

Successful functionalization of Si(001) with high surface perfection.

Efficient copper-catalyzed alkyne-azide click reaction on silicon surfaces.

Achieved 50-60% reaction efficiency of surface-bound molecules.

Abstract

Synthesis of organic bi-layers on silicon was realized by a combination of surface functionalization under ultra-high vacuum (UHV) conditions and solution-based click chemistry. The silicon (001) surface was prepared with a high degree of perfection in UHV and functionalized via chemoselective adsorption of ethinyl cyclopropyl cyclooctyne from the gas phase. A second organic layer was then coupled in acetonitrile via the copper-catalyzed alkyne azide click reaction. The samples were directly transferred from UHV via the vapour phase of the solvent into the solution of reactants and back to UHV without contact to ambient conditions. Each reaction step was monitored by means of X-ray photoelectron spectroscopy in UHV; the N 1s spectra clearly indicated the click reaction of the azide group in the two test molecules employed, i.e., methyl-subsituted benzylazide and azide substituted pyrene. In both cases, up to 50 - 60 % of the ethinyl cyclopropyl cyclooctyne molecules on the surface were reacted.