Probing the mechanism for graphene nanoribbon formation on gold surfaces through X-ray spectroscopy

Abstract

We studied the formation of graphene nanoribbons (GNRs) via the self-assembly of 10,10'-dibromo-9,9'-bianthryl precursor molecules on gold surfaces with different synchrotron spectroscopies. Through X-ray photoemission spectroscopy core-level shifts, we followed each step of the synthetic process, and could show that the Br-C bonds of the precursors cleave at temperatures as low as 100 degrees C on both Au(111) and Au(110). We established that the resulting radicals bind to Au, forming Au-C and Au-Br bonds. We show that the polymerization of the precursors follows Br desorption from Au, suggesting that the presence of halogens is the limiting factor in this step. Finally, with angle-resolved ultraviolet photoemission spectroscopy and density functional theory we show that the GNR/Au interaction results in an upshift of the Shockley surface state of Au(111) by similar to 0.14 eV, together with an increased electron effective mass

Imaging on-surface hierarchical assembly of chiral supramolecular networks

“…Moreover, on Cu(111), at surface temperatures above 240 K, debromination spontaneously occurs, 36 generating biradical active species. While on Au(111) covalent coupling is readily triggered after the radical generation, 44,45 for the case of similar molecules on Cu(111), metal adatoms have been shown to bind to the active C atoms, giving rise to C-Cu-C coordination (see Fig. 1), [46][47][48] recently identified as possible intermediates of the Ullmann coupling reaction.…”

Layer-by-Layer Self-Assembled Graphene Multilayer Films via Covalent Bonds for Supercapacitor Electrodes

“…Layer-by-layer (LBL) self-assembly, as one of most efficient techniques that could construct well-ordered lamellar nano-architectures, has attracted great attention [16][17][18][19]. Most self-assembly processes were based on electrostatic interaction, hydrogen bonds, electrochemistry, and so on [20,21].…”

Modification of electronic surface states by graphene islands on Cu(111)

“…15,36 However, m * was either found to be unchanged within the experimental resolution 15,22 , or in the case of graphene nanoribbons on Au(111), increased. 36 In fact, the combination of a shift in the band edge toward E F and a decrease in m * observed for the gr/Cu(111) system here runs counter to the typical trend observed.…”

“…15,36 However, m * was either found to be unchanged within the experimental resolution 15,22 , or in the case of graphene nanoribbons on Au(111), increased. 36 In fact, the combination of a shift in the band edge toward E F and a decrease in m * observed for the gr/Cu(111) system here runs counter to the typical trend observed. For dielectric overlayers, 7 noble gases, 37 self-assembled molecular monolayers, 12 Ag on Au(111), 10 and monolayer BN 38 an upward shift in the Shockley band edge is accompanied by an increased m * .…”