Supramolecular assemblies formed on an epitaxial graphene superstructure

Article abstract of DOI:10.1002/anie.200905503

Quite comparable: A graphene monolayer is used as a substrate for the growth of two-dimensional hydrogen-bonded supramolecular structures (see STM image). The formation of these extended structures arises from a commensurability between their dimensions and a moire pattern formed by the graphene. (Figure Presented)

Full text of DOI:10.1002/anie.200905503

Communications
DOI: 10.1002/anie.200905503
Molecular Assemblies
Supramolecular Assemblies Formed on an Epitaxial Graphene
Superstructure**
Andrew J. Pollard, Edward W. Perkins, Nicholas A. Smith, Alex Saywell, Gudrun Goretzki,
Anna G. Phillips, Stephen P. Argent, Hermann Sachdev, Frank Mꢀller, Stefan Hꢀfner,
Stefan Gsell, Martin Fischer, Matthias Schreck, Jꢀrg Osterwalder, Thomas Greber, Simon Berner,
Neil R. Champness,* and Peter H. Beton*
The seminal work of Novoselov et al.[1] has stimulated great
interest in the controllable growth of epitaxial graphene
monolayers.[2–12] While initial research was focussed on the
use of SiC wafers,[3] the promise of transition metals as
substrates has also been demonstrated[4–12] and both
approaches are scalable to large-area production.[4,5,8,12] The
growth of graphene on transition metals such as Ru, Rh and Ir
leads to a moirꢀ-like superstructure,[6,7,9,10,12,13] similar to that
observed for BN monolayers.[14,15] Here we show that such a
superstructure can be used to control the organization of
extended supramolecular nanostructures. The formation of
two-dimensional supramolecular arrays has received increas-
ing attention over recent years primarily due to potential
applications in nanostructure fabrication as well as funda-
mental interest in self-assembly processes.[16–18] Such studies
can be highly dependent on the nature of the substrate used,
and the interplay between surface and adsorbed supramolec-
ular structure is a topic of significant conjecture. Until now
metallic surfaces[17] or highly oriented pyrolytic graphite
(HOPG)[18] have typically been the surfaces of choice for
such studies. Our results demonstrate that graphene is
compatible with, and can strongly influence molecular self-
assembly.
We have studied the adsorption of perylene tetracarbox-
ylic diimide (PTCDI) and related derivatives on a graphene
monolayer grown on a Rh(111) heteroepitaxial thin film
(Figure 1). In particular, we show that a near-commensur-
[*] A. J. Pollard, Dr. E. W. Perkins, N. A. Smith, A. Saywell,
Prof. P. H. Beton
School of Physics & Astronomy, University of Nottingham
Nottingham, NG7 2RD (UK)
E-mail: peter.beton@nottingham.ac.uk
Dr. G. Goretzki, A. G. Phillips, Dr. S. P. Argent,
Prof. N. R. Champness
School of Chemistry, University of Nottingham
Nottingham, NG7 2RD (UK)
E-mail: Neil.Champness@nottingham.ac.uk
Figure 1. a) STM image of graphene monolayer on Rh(111)/YSZ/
Si(111) substrate (sample voltage 1.0 V, tunnel current 200 pA). The
periodic features (period 2.95 nm) arise from a moirꢀ pattern because
of the mismatch between the graphite and Rh lattice constants.
b) Diagram of honeycomb mesh (dark blue) representing graphene
overlaid on an array of gray circles representing Rh atoms. The
superstructure formed by 12ꢁ12 unit cells of graphene overlaid on
11ꢁ11 unit cells of Rh gives rise to a long range periodic pattern (unit
cell highlighted in light blue) with lattice vectors marked by arrows—
these are also identified in the zoomed image shown in the inset to
(a). c–e) Structure of the three molecules under investigation:
c) PTCDI, d) DP-PTCDI, e) DB-CTCDI.
Priv.-Doz. H. Sachdev, Dr. F. Mꢂller
Anorganische und Allgemeine Chemie
Universitꢃt des Saarlandes, Saarbrꢂcken (Germany)
Dr. F. Mꢂller, Prof. S. Hꢂfner
Institut fꢂr Experimentalphysik
Universitꢃt des Saarlandes, Saarbrꢂcken (Germany)
Dr. S. Gsell, M. Fischer, Dr. M. Schreck
Institut fꢂr Physik, Universitꢃt Augsburg (Germany)
Prof. J. Osterwalder, Prof. T. Greber, Dr. S. Berner
Physik-Institut, Universitꢃt Zꢂrich (Switzerland)
[**] We are grateful to the financial support under grant EP/D048761/1
from the UK Engineering and Physical Sciences Research Council.
The initial collaboration resulted from financial support from EU
grant NMP4-CT-2004-013817 “Nanomesh”. We are grateful to Luis
Perdigao for discussions related to density functional calculations.
ability between the PTCDI molecular dimensions and a
moirꢀ-like superstructure leads to the stabilization of
extended one-dimensional supramolecular assemblies. The
stabilization is due to NH···O intermolecular hydrogen bonds
between imide groups on neighboring molecules.[19,20] This
interaction may be systematically modified by the attachment
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.200905503.
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of alkane chains to the “bay” area of the fused aromatic core
resulting in a stabilization of a triangular, rather than linear,
molecular junction. Specifically we investigate 1,7-dipro-
pylthio-perylene-3,4:9,10-tetracarboxydiimide (DP-PTCDI)
(Figure 1d)[21] and 1,7-di(butyl)-coronene-3,4:9,10-tetracar-
boxylic acid bisimide (DB-CTCDI; Figure 1e; see Ref. [22]
and Supporting Information for synthetic details).
Our experiments were performed under ultra-high
vacuum (UHV) conditions using scanning tunnelling micros-
copy (STM; operated at room temperature) as the primary
experimental technique. The preparative procedures for the
Rh(111) substrate are described in detail elsewhere[12] (see
also Ref. [23]). In summary, a heteroepitaxial yttria-stabilized
zirconia (YSZ) buffer layer is first grown on a Si(111) wafer.
A Rh thin film (150 nm) is then grown on the YSZ buffer
layer. A piece of the wafer (area ca. 1 cm2) is cleaned in UHV
using a cycle of Ar ion sputtering followed by annealing in a
partial pressure of oxygen (see Supporting Information). To
form a graphene monolayer we first extract the sample from
UHV, then immerse it in an organic solvent (acetone or
paraldehyde (C6H12O3)) for 10–15 seconds and then return it
to the UHV system. After gradually annealing up to ca.
5008C over 24 h the sample is heated to 8008C for 30 min
resulting in the formation of a graphene monolayer. This
method of graphene production has provided insights into the
mechanism of formation of epitaxial graphene. Investigations
using low energy electron diffraction, photoelectron spec-
troscopy and STM support a model in which the precursor
molecules undergo a decomposition process with dicarbon
species (C2 radicals) as intermediates, which then finally
combine to form a graphene monolayer.[12] An STM image
acquired following this procedure shows clearly the super-
structure arising from the moirꢀ pattern associated with the
graphene monolayer (see STM image and diagram in
Figure 1a and b). The superstructure arises from 12 ꢁ 12
graphene unit cells overlaid on 11 ꢁ 11 Rh(111) unit cells and
has an overall period, am = 2.95 nm.[12]
Figure 2 a shows an STM image acquired (see Supporting
Information for experimental details) after deposition of
PTCDI in which rows with a width corresponding to one
molecule and lengths up to 25 nm are clearly resolved running
parallel to the principal directions of the surface. There are
many examples of pairs of extended rows which are adsorbed
on neighboring sites of the moirꢀ superstructure with a
pffiffi
spacing of 3am=2, although this appears to be the minimum
spacing for neighboring rows. The molecular arrangement on
the graphene superstructure differs significantly from that
observed for a graphite substrate, on which three-dimensional
islands are formed and the PTCDI/substrate interface is
buried, precluding a direct comparison with the ordering
observed here.[24] Single-molecule rows of PTCDI have been
observed on Ag passivated silicon, but these rows are short
and unstable and are rapidly converted to two-dimensional
islands.[19] The PTCDI morphology also differs significantly
from that reported for C60 and other organic molecules on a
SiC/graphene “nanomesh”, where close-packed two-dimen-
sional islands are observed.[25]
Figure 2. a) STM image acquired following deposition of PTCDI on a
graphene monolayer formed on Rh(111)/YSZ/Si(111); inset: structure
of deposited molecule. b) PTCDI–PTCDI dimer with a center–center
separation of d stabilized by two hydrogen bonds. c) Small area scan
showing intramolecular double lobe contrast of PTCDI molecules on
graphene. d) Placement of PTCDI rows on graphene superstructure as
depicted in Figure 1b. e) STM image of PTCDI on a BN nanomesh
formed on Rh(111)/YSZ/Si(111) in which isolated molecules are
trapped in nanomesh “pores” in contrast to the rows formed on
graphene. f) Placement of molecules on BN nanomesh. g) Higher
coverage of PTCDI (0.11 moleculesnmꢀ2) showing prevalence of
molecular rows spaced regularly on graphene. Imaging parameters
are: a) ꢀ1 V, tunnel current 200 pA; d) ꢀ1 V, 150 pA; e) ꢀ1.7 V, 30 pA;
f) ꢀ1 V, 200 pA.
Previous experimental estimates of the spacing of mole-
cules within PTCDI rows range from 1.41–1.46 nm.[19] Noting
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the near match between this spacing and am/2 (1.47 ꢁ 0.05 nm)
of the graphene superstructure, we propose below a structural
model for commensurate PTCDI rows (Figure 2b–d). Fig-
ure 2c shows an STM image of PTCDI in which intra-
molecular features are resolved in the form of two bright
lobes which run parallel to the long axis of symmetry of the
molecule. These lobes have previously been shown to
correspond to the highest occupied molecular orbital
(HOMO)[19] of PTCDI and allow us to confirm that the
orientation of the molecule and its placement on the graphene
superstructure is in agreement with the proposed model in
Figure 2d.
The importance of a commensurate match between
molecular dimensions and the moirꢀ periodicity is highlighted
by a comparison (see Figure 2e) with adsorption of PTCDI on
a boron nitride “nanomesh” monolayer[14] also formed on the
Rh(111)/YSZ/Si(111) surface (see Supporting Information).
This monolayer is isoelectronic with graphene, and also
displays a moirꢀ pattern but with a slightly larger periodicity
of 3.2 nm which does not have a simple commensurability
with the molecular dimensions. On this surface we observe
individual isolated PTCDI molecules (Figure 2 f) trapped in
energy minima associated with the moirꢀ pattern very similar
to that reported previously for napthalocyanine on the same
surface.[15] We attribute the absence of extended PTCDI
structures on this surface to the lack of commensurability
between the rows and the BN superstructure. Consequently,
molecules cannot be adsorbed in positions where they
minimize, independently, their energies of interaction with
both the surface and their neighboring molecules. The double
lobe intramolecular structure is also resolved for molecules
adsorbed on the BN nanomesh, from which we deduce that
there is no preferred in-plane orientation. In contrast, on
graphene, we do not observe isolated PTCDI and the
molecular orientation is non-random. The commensurability
on the graphene surface leads to the formation of continuous
rows, and the stabilization of the molecule in an orientation
directed at a neighboring occupied site.
The deposition of DP-PTCDI (Figure 3a) also leads to the
formation of commensurate rows, but, as compared with
PTCDI, there are fewer examples of pairs of parallel rows and
there are many more junctions where three molecules meet
(the ratio of dimer:trimer junctions is 75:25; for PTCDI less
than 1% of junctions are trimers). For DB-CTCDI the
formation of analogous junctions between three molecules
dominates (we are not able to identify unambiguously any
Figure 3. STM images acquired following deposition of a) DP-PTCDI,
b) DB-CTCDI on a graphene monolayer formed on Rh(111)/YSZ/
Si(111). c,d) Diagram of junctions between DP-PTCDI dimers (c) and
=
trimers (d) stabilized, respectively, by two and three C O···NH hydro-
gen bonds between neighboring molecules with dimer center–center
spacing of d and trimer vertex to molecule center spacing r. e) Place-
ment of DP-PTCDI trimers and dimers. f) DB-CTCDI trimer junction
analogous to (d) with vertex to molecule center spacing r and
placement of DB-CTCDI trimer on the graphene superstructure.
g,h) STM images of DB-CTCDI showing chirality of junctions and
intramolecular detail of molecules. The hexagons in (h) highlight the
chirality of the molecular arrangement. Imaging parameters: a) ꢀ1.0 V,
100 pA; b) 1.0 V, 100 pA; g) 1.5 V, 50 pA; h) ꢀ1.5 V, 50 pA.
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linear dimers) the observed molecular arrangements (Fig-
ure 3b). The array of trimers results in a honeycomb arrange-
ment of molecules which is aligned with the graphene
monolayer superstructure and encloses the areas of bright
contrast arising from the moirꢀ pattern.
0.1 nm) than their expected separation in an extended array,
pffiffiffi
am= 3 (1.70 ꢁ 0.06 nm). Thus, we expect these junctions to be
strained in an extended honeycomb array, leading to a
reduced binding energy, and propose that this accounts for
the stability of rows for the two molecules PTCDI and DP-
PTCDI, whereas only the molecule with the strongest
predicted trimer junction, DB-CTCDI forms a honeycomb
array.
The presence of alkyl side-chains is known from previous
studies of DP-PTCDI to enhance the stability of a chiral
molecular trimer vertex (illustrated in Figure 3d) as com-
pared with the linear hydrogen-bonded PTCDI-PTCDI
junctions.[22] A comparison of Figures 2a and 3a,b indicates
a progressively enhanced stabilization of a trimer vertex as
the alkyl chain length increases from zero length (PTCDI)
through to the longest chain (DB-CTCDI). This leads to a
change in morphology from the rows, for PTCDI, through to
the honeycomb DB-CTCDI, with the DP-PTCDI being
considered as an intermediate case where linear segments
co-exist with junctions of three molecules. The enhanced
stability of the trimer vertex for molecules with longer alkane
chains is supported by density functional theory (DFT)
calculations (performed in the gas-phase in the absence of
the substrate; see Supporting Information) as summarized in
Table 1 which shows the greatest difference between trimer
The images in Figures 2 and 3 show clearly that the
adsorbed molecules experience a local potential due to the
graphene superstructure which is sufficiently strong to inhibit
the formation of two-dimensional islands. The origin of this
potential has recently been discussed by Brugger et al.[13] who
showed that for both graphene and boron nitride monolayers
on Ru(0001) (closely related to Rh(111)) variations in local
work function lead to a periodic potential. However, the
topography of the resulting potentials which arise for
graphene and BN show significant differences. In particular,
for graphene on Ru(0001) the high symmetry points (equiv-
alent to the centers of the light blue hexagon in Figure 1b)
were shown to be energy maxima, while the energy minima
were shown to form a honeycomb network corresponding to a
connected region following, approximately, the edges of the
light blue hexagon in Figure 1b). In contrast, molecular
adsorption on BN occurs preferentially approximately mid-
way between the center and edge of the unit cell of the moirꢀ
superstructure as previously discussed by Dil et al.[26] The
placement of molecules which we observe is in excellent
agreement with the different potential landscapes arising
from the homoatomic character of graphene and the heter-
oatomic character of BN, respectively, as discussed by
Brugger et al.[13]
There are parallels with other systems where molecules or
clusters are adsorbed at sites on an ordered array of local
potential wells arising from self-organization due to, for
example, surface reconstruction or dislocation arrays,[27–29]
including those adsorbed on boron nitride[15] and graphene
monolayers.[6] However a distinguishing feature of our work is
the observation that the trapping potential is sufficiently
compliant to allow the molecules to relax and adopt a local
configuration which is controlled by interactions with mole-
cules trapped in neighboring energy minima so that extended,
connected structures may be formed. This represents an
example of a system which exhibits hierarchies of order,[30]
since the formation of the molecular rows is determined by
intermolecular interactions but the placement and separation
of the rows is guided by the underlying level of organization
due to the moirꢀ pattern. The control of row separation is
shown in Figure 2a and more clearly for a higher molecular
coverage in Figure 2g.
Table 1: Calculated binding energies, intermolecular separations d and
vertex separations 2r.[a]
EdHB [eV] d [nm] EtHB [eV] 2r [nm] EtHBꢀEdHB [eV]
(DFT)
PTCDI
DP-PTCDI 0.46
DB-CTCDI 0.45
0.46
1.44
1.45
1.44
0.52
0.57
0.57
1.61
1.63
1.60
0.06
0.11
0.12
[a] EdHB: energy per molecule in a row of dimers; EtHB: energy per
molecule in an extended honeycomb array of trimers. The values are
calculated as described in the Supporting Information. The relative
stability of the trimers over the dimers shows a trend of increasing
stability from PTCDI to DB-CTCDI, which is consistent with our
experimental observations. Also tabulated are the calculated intermo-
lecular separations for the dimer, d, and the vertex separation, 2r, for the
trimer (see Figures 2 and 3 for definition of distances).
and dimer binding energies is predicted for DB-CTCDI.
These data also indicate that, in the gas phase, the trimer is
more stable for DP-PTCDI and even for PTCDI. An
additional contribution to the stabilization energy arises due
to the van der Waals interactions of the alkyl chains, but is not
captured in the DFT calculations. This is estimated, using
classical force fields (see Supporting Information) applied to
the optimized geometries calculated using DFT. We find that,
for DP-PTCDI and DB-CTCDI, the difference in energies
between trimers and dimers is increased by ca. 0.2 eV due to
the presence of the alkyl chains.
Also tabulated in Table 1 are the calculated separations of
the intermolecular junctions. For dimers formed from all of
the molecules investigated, the calculated equilibrium sepa-
ration is very close (within 0.03 nm) to am/2 (the observed
spacing of molecules in the commensurate rows is 1.47 ꢁ
0.05 nm). However, the predicted separation for intermolec-
ular trimer junctions (Table 1) is significantly lower (by up to
The attachment of alkane chains to DP-PTCDI and DB-
CTCDI leads to a surface-induced chirality[31] for these
molecules. Furthermore, the trimer junction is intrinsically
chiral. Images of the DB-CTCDI network shown in Fig-
ures 3g and h confirm that the molecules are in a chiral
arrangement (both chiralities have been observed with
domain sizes of up to 30 nm). Specifically in Figure 3h the
bright intramolecular features form a hexagon with an axis of
symmetry rotated with respect to the principal axes of the
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[12] F. Mꢄller, H. Sachdev, S. Hꢄfner, A. J. Pollard, E. W. Perkins,
J. C. Russell, P. H. Beton, S. Gsell, M. Fischer, M. Schreck, B.
Strizker, Small 2009, 5, 2291 – 2296.
[13] T. Brugger, S. Gꢄnther, B. Wang, J. H. Dil, M.-L. Bocquet, J.
Osterwalder, J. Wintterlin, T. Greber, Phys. Rev. B 2009, 79,
045407.
molecular network (which are parallel to those of the
graphene superstructure). Note also that there are clear
gaps between some of the trimers in Figures 3g and h—
further evidence of strain arising from a small mismatch
between molecular and superstructure dimensions for the
trimer array.
[14] M. Corso, W. Auwarter, M. Muntwiler, A. Tamai, T. Greber, J.
Osterwalder, Science 2004, 303, 217 – 220.
Our results show that graphene superstructures offer a
suitable substrate for the formation of extended, hierarchical
self-assembled nanostructures. In addition to the intrinsic
interest in self-assembly processes our work also raises
interesting questions in relation to graphene electronics.
Recent papers have demonstrated that molecules can act as
molecular dopants[32] and also that the superstructure result-
ing from a moirꢀ pattern of graphene grown on Ir(111) gives
rise to the formation of a band-gap[33] raising interesting
connections with the self-assembled molecular structures we
report here. The interplay between the characteristic dimen-
sions resulting from graphene growth and molecular ordering
offer many possible routes for further investigation related to
both the electronic properties of graphene as well as the
formation of complex self-assembled structures.
[15] S. Berner, M. Corso, R. Widmer, O. Groening, R. Laskowski, P.
Blaha, K. Schwarz, A. Goriachko, H. Over, S. Gsell, M. Schreck,
H. Sachdev, T. Greber, J. Osterwalder, Angew. Chem. 2007, 119,
5207 – 5211; Angew. Chem. Int. Ed. 2007, 46, 5115 – 5119.
[16] a) J. V. Barth, G. Costantini, K. Kern, Nature 2005, 437, 671 –
679; b) T. Kudernac, S. Lei, J. A. A. W. Elemans, S. De Feyter,
Chem. Soc. Rev. 2009, 38, 402 – 421; c) J. Sakamoto, J. van Heijst,
O. Lukin, A. D. Schlꢄter, Angew. Chem. 2009, 121, 1048 – 1089;
Angew. Chem. Int. Ed. 2009, 48, 1030 – 1069.
[17] a) J. A. Theobald, N. S. Oxtoby, M. A. Phillips, N. R. Champness,
P. H. Beton, Nature 2003, 424, 1029 – 1031; b) A. Llanes-Pallas,
M. Matena, T. Jung, M. Prato, M. Stꢃhr, D. Bonifazi, Angew.
Chem. 2008, 120, 7840 – 7844; Angew. Chem. Int. Ed. 2008, 47,
7726 – 7730; c) M. E. Caꢅas-Ventura, W. Xiao, D. Wasserfallen,
K. Mꢄllen, H. Brune, J. V. Barth, R. Fasel, Angew. Chem. 2007,
119, 1846 – 1850; Angew. Chem. Int. Ed. 2007, 46, 1814 – 1818;
d) L. M. A. Perdig¼o, N. R. Champness, P. H. Beton, Chem.
Commun. 2006, 538 – 540; e) P. A. Staniec, L. M. A. Perdig¼o, A.
Saywell, N. R. Champness, P. H. Beton, ChemPhysChem 2007, 8,
2177 – 2181.
Received: October 1, 2009
Revised: November 23, 2009
Published online: February 4, 2010
[18] a) M. O. Blunt, J. Russell, M. C. Gimꢀnez-Lꢆpez, J. P. Garrahan,
X. Lin, M. Schrꢃder, N. R. Champness, P. H. Beton, Science
2008, 322, 1077 – 1081; b) M. Blunt, X. Lin, M. C. Gimenez-
Lopez, M. Schrꢃder, N. R. Champness, P. H. Beton, Chem.
Commun. 2008, 2304 – 2306; c) V. Stepanenko, F. Wꢄrthner,
Small 2008, 4, 2158 – 2161; d) M. Li, S.-B. Lei, Y.-L. Yang, T.-S.
Wang, Y.-T. Shen, C.-R. Wang, Q.-D. Zeng, C. Wang, Angew.
Chem. 2008, 120, 6819 – 6823; Angew. Chem. Int. Ed. 2008, 47,
6717 – 6721; e) C. Meier, K. Landfester, D. Kꢄnzel, T. Markert,
A. Groß, U. Ziener, Angew. Chem. 2008, 120, 3881 – 3885;
Angew. Chem. Int. Ed. 2008, 47, 3821 – 3825; f) S. Lei, K. Tahara,
F. C. De Schryver, M. Van der Auweraer, Y. Tobe, S. De Feyter,
Angew. Chem. 2008, 120, 3006 – 3010; Angew. Chem. Int. Ed.
2008, 47, 2964 – 2968.
[19] J. C. Swarbrick, J. Ma, J. A. Theobald, N. S. Oxtoby, J. N. OꢂShea,
N. R. Champness, P. H. Beton, J. Phys. Chem. B 2005, 109,
12167 – 12174; D. L. Keeling, N. S. Oxtoby, C. Wilson, M. J.
Humphry, N. R. Champness, P. H. Beton, Nano Lett. 2003, 3, 9 –
12.
[20] C. Ludwig, B. Gompf, J. Petersen, R. Strohmaier, W. Eisen-
menger, Z. Phys. B 1994, 93, 365 – 373.
[21] L. M. A. Perdig¼o, A. Saywell, G. N. Fontes, P. A. Staniec, G.
Goretzki, N. R. Champness, P. H. Beton, Chem. Eur. J. 2008, 14,
7600 – 7607.
[22] F. Nolde, W. Pisula, S. Mꢄller, C. Kohl, K. Mꢄllen, Chem. Mater.
2006, 18, 3715 – 3725.
[23] S. Gsell, M. Fischer, M. Schreck, B. Stritzker, J. Cryst. Growth
2009, 311, 3731 – 3736.
[24] N. Berdunov, A. J. Pollard, P. H. Beton, Appl. Phys. Lett. 2009,
94, 043110.
[25] W. Chen, H. L. Zhang, H. Xu, E. S. Tok, K. P. Loh, A. T. S. Wee,
J. Phys. Chem. B 2006, 110, 21873 – 21881; Q. H. Wang, M. C.
Hersam, Nat. Chem. 2009, 1, 206 – 211.
[26] H. Dil, J. Lobo-Checa, R. Laskowski, P. Blaha, S. Berner, J.
Osterwalder, T. Greber, Science 2008, 319, 1824 – 1826.
[27] W. Xiao, P. Ruffieux, K. Aꢇt-Mansour, O. Grꢃning, K. Palotas,
W. A. Hofer, P. Grꢃning, R. Fasel, J. Phys. Chem. B 2006, 110,
21394 – 21398.
Keywords: graphene · hydrogen-bonding ·
molecular recognition · supramolecular assembly
.
[1] a) K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y.
Zhang, S. V. Dubonos, I. V. Grigorieva, A. A. Firsov, Science
2004, 306, 666 – 669; b) A. K. Geim, Science 2009, 324, 1530 –
1534.
[2] C. N. R. Rao, A. K. Sood, K. S. Subrahmanyam, A. Govindaraj,
Angew. Chem. 2009, 121, 7890 – 7916; Angew. Chem. Int. Ed.
2009, 48, 7752 – 7777.
[3] C. Berger, Z. Song, T. Li, X. Li, A. Y. Ogbazghi, R. Feng, Z. Dai,
A. N. Marchenkov, E. H. Conrad, P. N. First, W. A. de Heer, J.
Phys. Chem. B 2004, 108, 19912 – 19916.
[4] K. S. Kim, Y. Zhao, H. Jang, S. Y. Lee, J. M. Kim, K. S. Kim, J.-H.
Ahn, P. Kim, J.-Y. Choi, B. H. Hong, Nature 2009, 457, 706 – 710.
[5] A. Reina, X. Jia, J. Ho, D. Nezich, H. Son, V. Bulovic, M. S.
Dresselhaus, J. Kong, Nano Lett. 2009, 9, 30 – 35.
[6] J. Coraux, A. T. NꢂDiaye, C. Busse, T. Michely, Nano Lett. 2008,
8, 565 – 570.
[7] P. W. Sutter, J.-I. Flege, E. A. Sutter, Nat. Mater. 2008, 7, 406 –
411.
[8] Q. Yu, J. Lian, S. Siriponglert, H. Li, Y. P. Chen, S.-S. Pei, Appl.
Phys. Lett. 2008, 93, 113103; A. J. Pollard, R. R. Nair, S. N. Sabki,
C. R. Staddon, L. M. A. Perdigao, C. H. Hsu, J. M. Garfitt, S.
Gangopadhyay, H. F. Gleeson, A. K. Geim, P. H. Beton, J. Phys.
Chem. C 2009, 113, 16565 – 16567.
[9] A. T. NꢂDiaye, J. Coraux, T. N. Plasa, C. Busse, T. Michely, New
J. Phys. 2008, 10, 043033.
[10] D. Martoccia, P. R. Willmott, T. Brugger, M. Bjꢃrck, S. Gꢄnther,
C. M. Schlepꢄtz, A. Cervellino, S. A. Pauli, B. D. Patterson, S.
Marchini, J. Wintterlin, W. Moritz, T. Greber, Phys. Rev. Lett.
2008, 101, 126102.
[11] D. Usachov, A. M. Dobrotvorskii, A. Varykhalov, O. Rader, W.
Gudat, A. M. Shikin, V. K. Adamchuk, Phys. Rev. B 2008, 78,
085403.
1798
www.angewandte.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2010, 49, 1794 –1799

Angewandte
Chemie
[28] N. Weiss, T. Cren, M. Epple, S. Rusponi, G. Baudot, S. Rohart, A.
Tejeda, V. Repain, S. Rousset, P. Ohresser, F. Scheurer, P.
Bencok, H. Brune, Phys. Rev. Lett. 2005, 95, 157204; H. Brune,
M. Giovannini, K. Broman, K. Kern, Nature 1998, 394, 451 – 453.
[29] B. Lu, T. Iimori, K. Sakamoto, K. Nakatsuji, F. Rosei, F. Komori,
J. Phys. Chem. C 2008, 112, 10187 – 10192.
[31] Q. Chen, D. J. Frankel, N. V. Richardson, Surf. Sci. 2002, 497, 37 –
46.
[32] W. Chen, S. Chen, D. C. Qi, X. Y. Gao, A. T. S. Wee, J. Am.
Chem. Soc. 2007, 129, 10418 – 10422.
´
[33] I. Pletikosic, M. Kralj, P. Pervan, R. Brako, J. Coraux, A. T.
NꢂDiaye, C. Busse, T. Michely, Phys. Rev. Lett. 2009, 102, 056808.
[30] V. Palermo, P. Samori, Angew. Chem. 2007, 119, 4510 – 4514;
Angew. Chem. Int. Ed. 2007, 46, 4428 – 4432.
Angew. Chem. Int. Ed. 2010, 49, 1794 –1799
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
1799