We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK


97% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Self-assembly of amino-thiols via gold-nitrogen...
View graph of relations

« Back

Self-assembly of amino-thiols via gold-nitrogen links and consequence for in situ elongation of molecular wires on surface-modified electrodes

Research output: Contribution to journalJournal article


  • Geoff Ashwell
  • Aled T. Williams
  • Susan A. Barnes
  • Sarah Chappell
  • Laurie J. Phillips
  • Benjamin Robinson
  • Barbara Urasinska-Wojcik
  • Piotr Wierzchowiec
  • Ian R. Gentlee
  • B. Wood
<mark>Journal publication date</mark>17/03/2011
<mark>Journal</mark>The Journal of Physical Chemistry C
Number of pages9
<mark>Original language</mark>English


The stepwise synthesis of molecular wires on goldnanoparticles and gold electrodes has been performed using amino-terminated and aldehyde-terminated thiols as anchoring groups to provide surface-active sites for imino coupling. X-ray photoelectron spectroscopy provides evidence that 4-mercaptoaniline (1) binds via either substituent, Au−S−C6H4−NH2 (N 1s, 400.1 eV) or Au−N(H2)−C6H4−SH (N 1s, 399.1 eV), therefore depleting the number of reactive amine sites at the surface. In contrast, 4-[(4-mercaptophenylimino)methyl]benzaldehyde (2) binds exclusively via a thiolate link (Au−S−wire−CHO) and, in relation to the former, highlights the significance of the second substituent. Amines compete with thiols for self-assembly on gold and may even bond via deprotonated nitrogen. For instance, 4-{(E)-1,3-dihydro-2H-benzimidazol-2-thione-5-yl)imino]methyl}benzaldehyde (3) binds via a nitrogen of the imidazole ring and the self-assembled monolayer (SAM) exhibits a 2.2 eV shift of the N 1s binding energy (SAM, 398.3 eV; solid sample, 400.5 eV) compared with a 1.0 eV shift for 1. Its in situ formed molecular wires with one to five bridged anthraquinone units exhibit symmetrical current−voltage characteristics, but the behavior alters to rectifying when the electron-accepting sequence is terminated by a 4-(dimethylamino)-1-naphthalene donor. Forward bias corresponds to electron flow from cathode to acceptor and from donor to anode, but the electrical asymmetry is dependent upon the number of bridging units. Molecules with two anthraquinones exhibit an optimum rectification ratio of 55 at ±1 V.