Fabrication of Thiol-Terminated Surfaces Using Aromatic Self-Assembled Monolayers

Abstract

Self-assembled monolayers (SAMs) formed from [1,1‘-biphenyl]-4,4‘-dimethanethiol (BPDMT) and [1,1‘;4‘,1‘ ‘-terphenyl]-4,4‘ ‘-dimethanethiol (TPDMT) on Au were characterized by X-ray photoelectron spectroscopy (XPS), high-resolution XPS, infrared reflection absorption spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and water contact angle measurements. The results of all experimental techniques suggest the formation of densely packed and highly oriented SAMs for both BPDMT and TPDMT, with a slightly higher packing density and a smaller molecular inclination in TPDMT/Au. All molecules were found to be bound to the substrate via the thiolate link, i.e., by one of the thiol groups, whereas the second thiol group is located at the SAM−ambient interface. This suggests that aromatic dithiols are well-suited for the fabrication of thiol-terminated SAMs. Such films are of particular importance for molecular electronics, since the thiol group has a high affinity to metals and can be used as a chemical link between a metal nanowire and the molecule.

Electrochemical and Photophysical Properties of Ruthenium(II) Bipyridyl Complexes with Pendant Alkanethiol Chains in Solution and Anchored to Metal Surfaces

“…At first sight, these results are perhaps surprising since the complexes with two alkyl thiolate chains are expected to possess a better geometry and a stronger chelating effect leading to the formation of more stable adsorbed layers. However, such chelating effect is only observed in the complexes with shorter anchoring chains (comparing the surface coverage of bpy 2 RubpyC 4 SH with bpy 2 Rubpy (C 4 SH) 2 ) and not in the two complexes with the longer chains. Also, longer anchoring chains only seem to facilitate higher surface coverage in complexes with only one anchoring group, as evidenced by comparing the surface coverage data of bpy 2 RubpyC 7 SH and bpy 2 RubpyC 4 SH.…”

“…Also, longer anchoring chains only seem to facilitate higher surface coverage in complexes with only one anchoring group, as evidenced by comparing the surface coverage data of bpy 2 RubpyC 7 SH and bpy 2 RubpyC 4 SH. As on platinum surfaces, bpy 2 Rubpy(C 4 SH) 2 showed the highest coverage on ITO, 11% (based on an estimated area of 100 Å 2 /molecule), while for the other complexes, only around 1.5-3% of the surface was covered by the adsorbate. These results, combined with the surface coverage on platinum, showed that the optimum number of carbon atoms spacing the ruthenium centre from the sulfur atom or the optimum number of tails are parameters which are difficult to tune.…”

“…In order to prepare ruthenium complexes, the bipyridine derivatives were complexed with [Ru(bpy) 2 Cl 2 ] in deaerated DMF. The bromo function(s) were transformed into thioacetate function(s) using an "Amberlyte ® " resin grafted with thioacetate ( Fig.…”

“…For these methods no precise positioning of the components is attainable. In order to move from disordered solid samples to organized monolayers, it is necessary to assemble the molecules, via covalent [1,2,3,4] or non-covalent interactions [5][6][7][8][9][10][11][12] on a substrate and to study their properties at this interface. Amongst the responsive molecules, those addressable with light and able to give a strong emission signal are very appealing since any type of surface can be used and no wiring is required for their activation [13,14].…”

Electrochemical and Photophysical Properties of Ruthenium(II) Bipyridyl Complexes with Pendant Alkanethiol Chains in Solution and Anchored to Metal Surfaces

“…For these methods no precise positioning of the components is attainable. In order to move from disordered solid samples to organized monolayers, it is necessary to assemble the molecules, via covalent [1,2,3,4] or non-covalent interactions [5][6][7][8][9][10][11][12] on a substrate and to study their properties at this interface. Amongst the responsive molecules, those addressable with light and able to give a strong emission signal are very appealing since any type of surface can be used and no wiring is required for their activation [13,14].…”