Towards Molecular Electronic Devices Based On 'All-Carbon' Wires

Nascent molecular electronic devices based on linear 'all- carbon' wires attached to gold electrodes through robust and reliable C-Au contacts are prepared via efficient in situ sequential cleavage of trimethylsilyl end groups from an oligoyne, Me3Si-(C C)(4)-SiMe3 (1). In the first stage of the fabrication process, removal of one trimethylsilyl (TMS) group in the presence of a gold substrate, which ultimately serves as the bottom electrode, using a stoichiometric fluoride-driven process gives a highly-ordered monolayer, Au vertical bar C CC CC CC CSiMe3 (Au vertical bar C8SiMe3). In the second stage, treatment of Au vertical bar C8SiMe3 with excess fluoride results in removal of the remaining TMS protecting group to give a modified monolayer Au vertical bar C CC CC CC CH (Au vertical bar C8H). The reactive terminal C C-H moiety in Au vertical bar C8H can be modified by 'click' reactions with (azidomethyl) ferrocene (N(3)CH(2)Fc) to introduce a redox probe, to give Au vertical bar C(6)C(2)N(3)HCH(2)Fc. Alternatively, incubation of the modified gold substrate supported monolayer Au vertical bar C8H in a solution of gold nanoparticles (GNPs), results in covalent attachment of GNPs on top of the film via a second alkynyl carbon-Au sigma-bond, to give structures Au vertical bar C-8 vertical bar GNP in which the monolayer of linear, 'allcarbon' C-8 chains is sandwiched between two macroscopic gold contacts. The covalent carbon-surface bond as well as the covalent attachment of the metal particles to the monolayer by cleavage of the alkyne C-H bond is confirmed by surface-enhanced Raman scattering (SERS). The integrity of the carbon chain in both Au vertical bar C(6)C(2)N(3)HCH(2)Fc systems and after formation of the gold top-contact electrode in Au vertical bar C-8 vertical bar GNP is demonstrated through electrochemical methods. The electrical properties of these nascent metal-monolayer-metal devices Au vertical bar C-8 vertical bar GNP featuring 'all-carbon' molecular wires were characterised by sigmoidal I-V curves, indicative of well-behaved junctions free of short circuits.