Extended monolayer of cyano-ended oligo(para-phenylenes) at the air/HOPG interface investigated by high-resolution AFM

Abstract

The formation of functional networks on surfaces is one of the main challenges in the field of nanotechnologies. In this paper, we shall propose a very simple process which can be used to achieve the formation of extended monolayer of functional oligo(para-phenylenes) molecules at the air/graphite interface. By developing a convergent strategy, we successfully achieved the synthesis of oligo(para-phenylenes) molecules with a tuneable length. The photophysical properties of these new oligomers were characterized by UV-vis absorption and fluorescence spectroscopy. Deposition of these molecules by a simple spin-coating process on a highly oriented pyrolytic graphite (HOPG) surface leads to the formation of extended monolayered 2D networks. These networks were characterized by atomic force microscopy experiments under ambient conditions with submolecular resolution thus providing the adsorption model of these molecules on an HOPG surface.

Quasi-one-dimensional cyano-phenylene aggregates: Uniform molecule alignment contrasts varying electrostatic surface potential

“…[20][21][22] Cyano-functionalization is of special interest due to the strong electron withdrawing effect, resulting in an asymmetric charge distribution, and due to the capability of the CN group to form hydrogen bonds. [23][24][25][26][27] It has thus the potential to impact molecular packing, the electronic structure of crystallite facets, thin film formation, and self-assembly, 28 and hence can convert a p-type organic semiconductor into an n-type one. 29,30 Consequently, optical properties such as the fluorescence quantum yield might be enhanced as well.…”

Self-assembled viologens on HOPG: solid-state NMR and AFM unravel the location of the anions

“…Atomic force microscopy (AFM) is a commonly used method to investigate the self-organization of molecules on surfaces under ambient conditions at the sub-molecular level. 7,8 However, for organic salts like viologens, the position of the organic cations is well determined whereas the position of corresponding anions has been investigated less, mainly because these anions are often smaller than the organic cations. 9,10 The position of the anions has been studied using scanning tunneling microscopy.…”

“…Alkoxy chains are well known to promote molecule-surface interactions on an HOPG surface and molecule-molecule interactions due to interdigitation of adjacent chains. 8,16,17 Compounds ArV-C8 and ArV-C12 are N-arylviologens that differ by the length of their alkoxy chains. MV-C18 is an N-methylviologen functionalized at the 3,3′-positions with C18 alkoxy chains that were chosen to compensate for the dihedral angle of the 3,3′-substituted pyridinium rings.…”

“…Alkoxy chains are well known to promote molecule–surface interactions on an HOPG surface and molecule–molecule interactions due to interdigitation of adjacent chains. 8,16,17…”