Large-scale solution synthesis of narrow graphene nanoribbons

Abstract

According to theoretical studies, narrow graphene nanoribbons with atomically precise armchair edges and widths of o2 nm have a bandgap comparable to that in silicon (1.1 eV), which makes them potentially promising for logic applications. Different top-down fabrication approaches typically yield ribbons with width 410 nm and have limited control over their edge structure. Here we demonstrate a novel bottom-up approach that yields gram quantities of high-aspect-ratio graphene nanoribbons, which are only B1 nm wide and have atomically smooth armchair edges. These ribbons are shown to have a large electronic bandgap of B1.3 eV, which is significantly higher than any value reported so far in experimental studies of graphene nanoribbons prepared by top-down approaches. These synthetic ribbons could have lengths of 4100 nm and self-assemble in highly ordered few-micrometer-long 'nanobelts' that can be visualized by conventional microscopy techniques, and potentially used for the fabrication of electronic devices.

Bulk properties of solution-synthesized chevron-like graphene nanoribbons

“…2e) gives an optical band gap of $1.6 eV, which is very close to the theoretical band gap value of 1.57 eV that was previously calculated using the density functional theory (DFT) method. 9,19 The electrical measurements were performed on pressed GNR pellets using the home-built setup shown in Fig. 3a.…”

“…Several recent studies have focused on the synthesis of GNRs by the bottom-up approaches that rely on building GNRs from smaller molecular species. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] The resulting GNRs are very narrow (typically with widths, w < 2 nm) and have atomically precise edges, which is very important for potential applications. [3][4][5][6]21,22 One type of synthetic GNRs that has received considerable theoretical [23][24][25] and experimental attention 9,16,19,20,26 is the chevron-like GNR that has a very distinct periodic structure (Fig.…”

Sublattice-induced symmetry breaking and band-gap formation in graphene

“…There are various widely publicized approaches to engineering a band gap in graphene, such as strain engineering, 1-4 spatial restriction, for example via graphene nanoribbon fabrication, [5][6][7][8][9][10][11][12][13][14][15][16] controlling the density of electrons as in adsorbate hybridization, [17][18][19][20][21] and symmetry breaking, [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] typically as a result of substrate interactions. All have major aws when the goal is retention of the unique properties of graphene while opening a band gap.…”

Exciton-dominated optical response of ultra-narrow graphene nanoribbons

“…This opens a way to tailor precise structural arrangements in the regime of ultranarrow GNRs and to realize specific edge terminations. Furthermore, recent studies showed that the bottom-up fabrication of GNRs can also be achieved in solution 17,18 where, although aggregation issues need to be addressed, the process can be easily scaled up. Similar as for their electronic properties, GNRs are expected to exhibit optical properties that are significantly different from the parent material graphene: Whereas graphene, owing to its linear band dispersion, reveals a wavelength-independent light absorbance of 2.3% 19 in the visible range, GNRs are expected to exhibit characteristic absorption bands related to band gap openings as well as to pronounced excitonic effects [8][9][10][11] that become dominant for quasi onedimensional (1D) systems 20 .…”