Formation of ω-Thiol Protected α,ω-Alkanedithiol Coated Gold Nanoparticles and Usage in Molecular Charge Transport Junctions
(English)Manuscript (preprint) (Other academic)
Gold nanoparticles (AuNPs) coated with stabilizing molecular monolayers are applied in a range of different areas. The stabilizing molecules are often anchored to the AuNPs through thiol groups. Herein, we present a novel one-pot and one-phase (THF) synthetic route that for the first time allows preparation of stable, monodisperse AuNPs (~6 nm diameter, SEM) that are coated with α,ω-alkanedithiols and where the outer w-thiol group is protected by a triphenylmethyl (trityl) group which allows this thiol group to be exploited in later functionalizations. The ω-thiol group is activated (deprotected) under acidic conditions, and it can be deprotected first when the AuNP has been placed properly for a certain application. Using dielectrophoresis we trap 20 - 30 of the ω-thiol protected α,ω-alkanedithiol coated AuNPs in a 20 nm gold electrode nanogap. Subsequent deprotection leads to a three-orders of magnitude increase in the conductance, indicating that we fuse the isolated coated AuNPs into a network with covalent AuNP-molecule-AuNP as well as electrode-molecule-AuNP bonds. Furthermore, we were able to carry out a complete NMR spectroscopic characterization of the AuNP surface bonded alkanedithiols using a series of one- and two-dimensional NMR techniques. We can in particular deduce that there are no H-atoms bonded to the sulfurs of the Au-S-R linkages of our molecule coated AuNPs. Using the Stokes-Einstein equation and the translational diffusion coefficients derived by NMR we determined the AuNP diameters to be 5.6 nm, which agrees well with the value obtained from SEM.
IdentifiersURN: urn:nbn:se:uu:diva-122938OAI: oai:DiVA.org:uu-122938DiVA: diva2:311422