Graphite vaporization provides an uncontrolled yet efficient means of producing fullerene molecules. However, some fullerene derivatives or unusual fullerene species might only be accessible through rational and controlled synthesis methods. Recently, such an approach has been used to produce isolable amounts of the fullerene C(60) from commercially available starting materials. But the overall process required 11 steps to generate a suitable polycyclic aromatic precursor molecule, which was then dehydrogenated in the gas phase with a yield of only about one per cent. Here we report the formation of C(60) and the triazafullerene C(57)N(3) from aromatic precursors using a highly efficient surface-catalysed cyclodehydrogenation process. We find that after deposition onto a platinum (111) surface and heating to 750 K, the precursors are transformed into the corresponding fullerene and triazafullerene molecules with about 100 per cent yield. We expect that this approach will allow the production of a range of other fullerenes and heterofullerenes, once suitable precursors are available. Also, if the process is carried out in an atmosphere containing guest species, it might even allow the encapsulation of atoms or small molecules to form endohedral fullerenes.
STM images of multidomain epitaxial graphene on Pt(111) have been combined with a geometrical model to investigate the origin of the coincidence Moiré superstructures. We show that there is a relation between the appearance of a particular Moiré periodicity and the minimization of the absolute value of the strain between the graphene and the substrate for the different orientations between both atomic lattices. This model predicts all the stable epitaxial graphene structures that can be grown on transition metal surfaces, and we have made use of it for reproducing previously published data from different authors. Its validity suggests that minimization of the strain within the coincident graphene unit-cell due to a strong local interaction is the driving force in the formation of Moiré superstructures.
We have studied large areas of (√3×√3)R30° graphene commensurate with a Pt(111) substrate. A combination of experimental techniques with ab initio density functional theory indicates that this structure is related to a reconstruction at the Pt surface, consisting of an ordered vacancy network formed in the outermost Pt layer and a graphene layer covalently bound to the Pt substrate. The formation of this reconstruction is enhanced if low temperatures and polycyclic aromatic hydrocarbons are used as molecular precursors for epitaxial growth of the graphene layers.
Deposition of 3,4,9,10‐perylene‐tetracarboxylic‐dianhydride on iron island arrays on Au(111) results in the formation of new nanostructures. By controlling the amount of iron deposited on the gold surface, two kinds of aggregates are obtained: molecular chains and organic nanodots (see figure). These nanostructures possess a different density of states from the two‐dimensional self‐assembled molecular layer.
We
have studied the deposition of perylene-tetracarboxylic-diimide,
PTCDI, on the rutile (1 × 1)-TiO2(110) surface. At
variance with other polyaromatic hydrocarbons, like acenes, PTCDI
displays a significant interaction with this dielectric substrate.
At moderate substrate temperature (∼400 K), first layer molecules
aggregate into two-dimensional islands corresponding to a (1 ×
5) commensurate phase. According to our surface diffraction, STM,
and NEXAFS studies, the substrate accommodates one PTCDI molecule
per unit cell, atop each oxygen row. Because of steric repulsion,
molecules lie on their long edge, tilted by ∼35° with
respect to the surface. This constraint determines a strong π–π
coupling between adjacent molecules, resulting into a geometry similar
to that reported for acenes on (1 × 1)-TiO2(110),
but quite uncommon for perylenes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.