Redox-active Si(100) surfaces covalently functionalised with [60]fullerene conjugates: new hybrid materials for molecular-based devices

Abstract

Herein, we report the covalent immobilisation, through Si–C bonds, of various [60]fullerene derivatives on flat silicon surfaces following three different preparative protocols. Each synthetic strategy comprises a two-step approach that includes a pre-modification step of the Si(100) surface with an organic monolayer bearing a terminal functionality that undergoes a bond-forming reaction with a [60]fullerene synthon as characterized by X-ray photoelectron spectroscopy (XPS) measurements. Water contact angle measurements clearly showed a characteristic change of the surface hydrophobicity upon covalent immobilisation of the carbon functions. The hybrid [4b-Si(100)] surfaces, containing [60]fullerene-ferrocene fragments, were also investigated by means of cyclic voltammetry (CV), and were revealed to be exceptionally robust towards repeated reduction–oxidation cycles. Moreover, several surface-confined redox couples were observed in CH₃CN solution. The surface coverage was measured to be ca. 2.5 × 10⁻¹¹ mol cm⁻².