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 CH(3)CN solution. The surface coverage was measured to be ca. 2.5 x 10(-11) mol cm(-2)

Designing Cascades of Electron Transfer Processes in Multicomponent Graphene Conjugates

“…In the Fe 2p photoemission region a major peak evolves at 708.0 eV next to a low‐intensity feature at 711.1 eV and a satellite line at higher energies. In agreement with literature reports, [48] the Fe 2p main peak is assigned to Fe II , while the other two components originate from Fe III . The co‐existence of Fe III and Fe II is likely to be due to interactions of the ferrocene valence orbitals with the conjugated network of π‐orbitals in graphene.…”

Functionalization of Carbon Spheres with a Porphyrin−Ferrocene Dyad

“…In fact, in some previous literature reports by some of us on redox‐active Si (100) covalently functionalized surfaces with [60] fullerene conjugates, the XPS spectra from Fe 2p revealed the presence of Fe(III) and Fe(II) states in a different ratio with respect to substituted ferrocene moieties directly bound to the same Si surface via an anchoring C=C or C≡C arm. This result was taken as an evidence of the electron‐withdrawing effect of fullerene compared to Si.…”

Immobilization of [60]fullerene on silicon surfaces through a calix[8]arene layer

“…17,18 Some noticeable examples are the wettability modulation of porous silicon 19 and the modification of electronic properties of semiconductors thanks to the electronaccepting characteristics of the fullerene sphere. [20][21][22][23] In the mentioned cases, the fullerene cage was functionalized with appropriate grafting groups for the bonding to the surface. Fullerene-based supramolecular systems, 24 on the other hand, do not require the functionalization of the carbon allotrope guest, which fully retains its electronic properties and, at least in principle, is less prone to aggregation.…”