Towards molecular electronic devices based on 'all-carbon' wires

Andrea Moneo; Alejandro González-Orive; Sören Bock; Marta Fenero; I Lucía Herrer; David C Milan; Matteo Lorenzoni; Richard J Nichols; Pilar Cea; Francesc Perez-Murano; Paul J Low; Santiago Martin

doi:10.1039/c8nr02347f

Towards molecular electronic devices based on 'all-carbon' wires

Nanoscale. 2018 Aug 7;10(29):14128-14138. doi: 10.1039/c8nr02347f. Epub 2018 Jul 12.

Authors

Affiliations

¹ Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009, Spain. agorive@mail.upb.de pilarce@unizar.es smartins@unizar.es.
² Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009, Spain. agorive@mail.upb.de pilarce@unizar.es smartins@unizar.es and Instituto de Nanociencia de Aragón (INA) and Laboratorio de Microscopías Avanzadas (LMA), edificio i+d Campus Rio Ebro, Universidad de Zaragoza, C/Mariano Esquillor, s/n, 50018 Zaragoza, Spain.
³ School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
⁴ Department of Chemistry, University of Liverpool, Liverpool, L69 7ZD, UK.
⁵ Instituto de Microelectrónica de Barcelona (IMB-CNM, CSIC), Campus UAB, 08193 Bellaterra, Spain.
⁶ Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009, Spain. agorive@mail.upb.de pilarce@unizar.es smartins@unizar.es and Instituto de Ciencias de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain.

PMID: 29999063
DOI: 10.1039/c8nr02347f

Abstract

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[triple bond, length as m-dash]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|C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CSiMe₃ (Au|C₈SiMe₃). In the second stage, treatment of Au|C₈SiMe₃ with excess fluoride results in removal of the remaining TMS protecting group to give a modified monolayer Au|C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH (Au|C₈H). The reactive terminal C[triple bond, length as m-dash]C-H moiety in Au|C₈H can be modified by 'click' reactions with (azidomethyl)ferrocene (N₃CH₂Fc) to introduce a redox probe, to give Au|C₆C₂N₃HCH₂Fc. Alternatively, incubation of the modified gold substrate supported monolayer Au|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 σ-bond, to give structures Au|C₈|GNP in which the monolayer of linear, 'all-carbon' C₈ 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|C₆C₂N₃HCH₂Fc systems and after formation of the gold top-contact electrode in Au|C₈|GNP is demonstrated through electrochemical methods. The electrical properties of these nascent metal-monolayer-metal devices Au|C₈|GNP featuring 'all-carbon' molecular wires were characterised by sigmoidal I-V curves, indicative of well-behaved junctions free of short circuits.