PERSPECTIVE
PUBLISHED ONLINE: 23 MAY 2011 | DOI: 10.1038/NCHEM.1043
Blueprinting macromolecular electronics
Carlos-Andres Palma† and Paolo Samorì*
Recently, by mastering either top-down or bottom-up approaches, tailor-made macromolecular nano-objects with
semiconducting properties have been fabricated. These engineered nanostructures for organic electronics are based on
conjugated systems predominantly made up of sp2-hybridized carbon, such as graphene nanoribbons. Here, we describe
developments in a selection of these nanofabrication techniques, which include graphene carving, stimulus-induced synthesis
of conjugated polymers and surface-assisted synthesis. We also assess their potential to reproduce chemically and spatially
precise molecular arrangements, that is, molecular blueprints. In a broad context, the engineering of a molecular blueprint
represents the fabrication of an integrated all-organic macromolecular electronic circuit. In this Perspective, we suggest
chemical routes, as well as convergent on-surface synthesis and microfabrication approaches, for the ultimate goal of bringing
the field closer to technology.
F
rom a windmill to a circuit board, behind the crafting of every tool
there is a strict layout of its constituent elements; its structural
blueprint determines the very position of each component.
The principle of creating a (macro- or supra-) molecule from a
complex blueprint, that is, a diagram defining the arrangement of
all atoms in space, is at the very heart of modern retro-synthetic
chemistry1, transition-state-designed catalysis2 and supramolecular
scaffolding3. Creating nanomaterials should be no exception to such
blueprinting, but the crafting of them for electronics applications
has been greatly limited by the lack of methods that enable the
accurate positioning of elements (molecules) in space4–6.
In this Perspective we highlight top-down and bottom-up
approaches that are converging towards the engineering of singlemacromolecular devices for organic (nano)electronics. In particular,
we explore both approaches and their limitations to accurately
reproducing the desired atomic layout or ‘molecular blueprint’
needed for the efficient production and integration of molecular
circuitry. The top-down approach cannot reproduce a molecular
blueprint with chemical accuracy, whereas the bottom-up surface
syntheses approaches still lack full thermodynamic and kinetic
control over the desired blueprint product (Fig. 1). We discuss how to
overcome these limitations with the ultimate goal of manufacturing
fully integrated all-organic (nano)devices.
Graphene nanoribbons as electronic components
Despite promises of inexpensive logic applications with chemically
tunable ‘plastic’ materials, active components of organic electronics
such as molecules7, polymers8 and carbon nanotubes9, are not yet
competitive with existing silicon technology. In miniaturization,
organic materials are confronted with two major challenges: the
inherent fabrication of a macromolecular blueprint and its interfacing
with metal electrodes4. In this regard, graphene holds great promise
as an organic component capable of replacing silicon technology10 in
the Moore paradigm11 because it is a large two-dimensional crystal
suitable for carving, with low contact resistance12. Although not a
semiconductor13, graphene can be cut up into smaller objects such
as graphene nanoribbons (GNRs), which opens up a bandgap14–16.
Figure 2a shows how the theoretical bandgap in GNRs was found to
depend critically on their atomic blueprint. The data is from refs 15
and 16, in which different levels of density functional theory were
employed (namely the local spin density approximation and its GW
correction16 and the generalized gradient approximation through the
PBE (Perdew-Burke-Enzerhof) functional and the screened exchange
hybrid density functional15). The inset depicts the corresponding
atomic structure of a D2h symmetric armchair GNR, showing that the
architecture’s width can be modulated approximately by multiples of
the lattice constant of graphene, a = 2.47 Å (red arrows in Fig. 2a).
Although an experimental bandgap in such sub-3-nm wide ribbons
is yet to be measured, interesting semiconducting properties were
already detected in larger GNRs. In 2008, preliminary devices based
on GNRs17–19 showed transistor properties with on/off rations of
1 × 107 and single molecular transistor behaviour, already surpassing
properties of previous organic20,21 and silicon nanowire22 devices.
However, the lack of reproducibility and practical integration of
graphene nanoribbons into devices is still a limiting factor. This can
be exemplified in the number of theoretical versus experimental
reports on graphene nanoribbons during the past five years, where
experimental works are outnumbered by a factor of four (out of
299 records matching the topic ‘graphene nanoribbons’ in ISI Web
of Science updated 21/8/2010, 239 were found not to contain the
patterns litho, etch, pattern, synthe in the title or abstract). In fact,
Fig. 2a also serves as a bright example on how the ultimate goal
of sp2-carbon electronics is to achieve atomic precision, not only
for tuning the device properties but also for reproducibility of the
electronic characteristics. More importantly, the design beyond
complementary metal-oxide semiconductor technologies, such
as valley valves23 and single-electron transistors19, relies on the
possibility of atomic control over graphene. The question arises of
how carbon electronics with precise molecular structures can be
embedded into the device configuration of choice. More generally,
how hundreds of moieties can be stitched together into a precise
million kilodalton macromolecule or how small can a material
be precisely cut into a well-defined macromolecule? To this end,
we present recent works that have shed light on the cutting and
stitching of organic molecules to reproduce graphene nanoribbon
molecular blueprints for (nano)electronics.
Blueprinting from the top
The most straightforward manner to follow a blueprint in order to
craft a single block of organic circuitry is through lithography or
Nanochemistry Laboratory, ISIS – CNRS 7006, Université de Strasbourg, 8 allée Gaspard Monge, 67000 Strasbourg, France. †Present address: Max-Planck
Institute for Polymer Research, 55128, Mainz, Germany. *e-mail: samori@unistra.fr
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© 2011 Macmillan Publishers Limited. All rights reserved
431
PERSPECTIVE
NATURE CHEMISTRY DOI: 10.1038/NCHEM.1043
a
b
4 nm
2 nm
m
(i) - Pattern mask
(ii) - Etch
(iii) - Remove mask
X
X
X
X
~20 nm
+X
Substrate
X
X
n
X
Cyclodehydrogenation
X
2 nm
X
Side products
Side products
l
Side products
Figure 1 | Ideal and reality. Generation of a simple element of circuitry reflecting an exact molecular blueprint (images with blue background). a, A topdown strategy through the etching or carving63 of a single graphene sheet with a resolution of ~20 nm, which could be subsequently reduced to ~5nm
(ref. 28). The uncertainty between the exact formation of the product and the desired molecular blueprint depends on the precise etching of single carbon
atoms. Top-right, AFM image taken from ref. 28. b, A bottom-up approach through pre-programmed synthesis42. The uncertainty (due to entropy) between
the products and the molecular blueprint in this case depends upon the (physico-)chemical level of pre-programming for reducing undesired isomers
and side products. Top-right, STM image from ref. 42; scale bar, 3 nm. Note that in both cases a strict blueprint should also comprise the position and
orientation of a substrate and other elements, if any. The X substituents represent labile atoms such as halogens. All carbons shown are sp2 hybridized.
engraving methods, which can be accomplished at the nanoscale
with the help of electromagnetic radiation and/or high-throughput
sharp probes. In graphene, lithographic methods include masking
and chemical etching19,24 or the thermal–electrochemical reduction
of graphene or graphene oxide with sharp probes25–27. However,
such methodologies have only produced uncertain macromolecular
structures with widths not smaller than ~20 nm, and bandgaps (Eg)
close to kT (~26 meV at 298 K)24. Scuseria et al.15 predicted in 2006
that for GNRs to be technologically competitive semiconductors,
their width should be effectively controlled down to ~3 nm, or
Eg = 0.5 – 0.3 eV. Just recently, chemical etching techniques have
been developed in which patterning of graphene can be achieved
with ~5 nm resolution. By using a gas mixture of ammonia
and oxygen on pre-etched patterns, Dai and Wang28 could etch
carbon nanoribbons with ~1-nm-per-minute control. As a result
~5-nm-wide GNRs could be produced with transistor properties
showing on/off ratios as high as 1 × 104, the record among
lithographically fabricated GNR devices. Likewise, Zhang and
co-workers29 reported the production of ~8-nm-wide nanoribbons
through the use of H2-plasma as an etching agent (Fig. 2b). They
showed that the etching is anisotropic, working preferentially along
the armchair edge, allowing the generation of zig-zag nanoribbons
along the [21̄10] direction. Carving 2D materials is not the only
route to accomplishing this goal — nanoscopic 3D materials have
also been cut down to create elements of graphene circuitry30,31.
Such top-down strategies may be ultimately applied to reproduce
an exact molecular blueprint (Fig. 1a). Chemical etching has come
near this goal because the H2-plasma technique allows the etching of single carbon atoms, that is, etching rates corresponding to
2.7 ± 0.5 Å min–1 (ref. 32). However, the mean edge roughness of
the GNR in the H2-plasma approach amounts to 2 nm (ref. 29), and
introduces random topological factors. It is worth pointing out that,
so far, the maximum resolution of chemically precise patterning has
been obtained by scanning tunnelling tip-induced reactions, showing ~2-nm-resolution patterning of organic self-assembled monolayers into nanowires33 (Fig. 2c). Nonetheless, scanning tunnelling
tip-induced reactions have only been demonstrated on particular
diacetylene self-assembled monolayer systems, in which the polymerization occurs perpendicular to the molecular axis34,35. In contrast,
organic thin films of semiconducting polymers can be patterned
freely with record resolutions below 28 nm (ref. 36). Unfortunately,
also in this case the as-written blueprint is not molecularly precise.
432
Because of the factors outlined above, a molecular blueprint
is still not ready to be reproduced solely through top-down
approaches, although the development of new high-resolution
etching agents, such as nanoparticles37, and the design of new
ordered monolayers may one day allow the direct top-down
patterning of defined macromolecules.
Blueprinting through synthetic programming
The need for such a high degree of atomic (thus bandgap and
energy level) precision in the crafting of molecular devices can be
accomplished by engineering protocols relying on the covalent
or non-covalent38 tethering of small units to form the designed
molecular blueprints. By mastering principles of heterogeneous
reactions and catalysis39–41, on-surface macromolecular synthesis
seems feasible. In this light, it is natural to identify the critical
steps for developing chemistry compatible with different surfaces.
In addition to catalysis and reaction design, surface-supported
chemistry allows the reduction of the six degrees of rotational and
translational freedom to (ideally) only one. This can be effectively
thought of as a reduction of the absolute translational and rotational
entropy, thus immediately constituting one level of thermodynamic
programming. Combined with computer-simulated mechanistic
studies, de novo design of the precursors yielding highly defined
macromolecular adducts may become reality, thus molecular
engineering of accurate organic electronic blueprints may also
become a reasonable target.
In the next section, we put forward evidence to show how early
computer simulations and empirical observations have identified
preliminary rules for the synthesis of extended architectures at
surfaces. Although still far from predicting precise protocols for
the synthesis of electronic circuitry, the examples demonstrate how
graphene materials are just the tip of the iceberg with respect to
new materials for electronics. In particular for the early examples
of radical additions42–47, two strategies may already be put forward
for the synthesis of extended macromolecular architectures: those
in which the reaction rate is diffusion-limited and those where the
rate is limited by the reaction probability.
Diffusion-limited on-surface synthesis
In diffusion-limited radical reactions, the macromolecular rate of
growth is dominated by the passive transport of the elements to the
reaction centre of the molecular blueprint, each with a hopping rate
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PERSPECTIVE
NATURE CHEMISTRY DOI: 10.1038/NCHEM.1043
a
5
1
Theoretical bandgap (eV)
4
2
3
Width in lattice constants (a)
4
5
6
Ref. 16 (LSDA)
Ref. 16 (GW)
Ref. 15 (PBE)
Ref. 15 (HSE)
7
8
9
a
10
c
2 nm
11
a ~ 2.47 Å
1.65 nm
3
M
n; n>>M
2
b
1.8 eV
0.8 eV 0.8 eV
Ag (111)
0.3 eV
2.2 eV
0
0
1
2
3
4
5
6
7
8
b
2.0 eV
1 nm
Cu (111)
9
Width in repeat units (M)
2.3 eV
HH
c
0.2 eV
0.1 eV 0.9 eV
0.2 eV
1
0.7 eV
1.7 eV
HH
H
H
H
H
H
H
H
H
H
H
H
H
+
~8 nm
~8 nm
HH
Diffusion
~12 nm
~22 nm
m
m
6n
6n
250 nm
500 nm
Figure 2 | Cutting a macromolecule into functional electronic elements.
a, The theoretical bandgap for the D2h symmetry armchair nanoribbon,
Dh-AGNR (inset); hydrogens are implicit. Red arrows depict the lattice
constant. M represents the number of lattice constants in the (01̄10)
direction, starting at a minimum of 2, and the ribbon is assumed to be
much larger in the perpendicular direction n (data from refs 15,16). b,
Cutting graphene into ~8–22-nm-long ribbons. Image reproduced with
permission from ref. 29, © 2010 Wiley. c, Stitching top-down strategy using
a tunnelling microscopy tip to regio-polymerize one row of di-acetylene
monolayers into a molecular wire (left) and an adjacent row (right)33.
~exp(–Ediff/kT); where for small molecules the energy of diffusion,
Ediff, is nearly 20% of the adsorption energy48. Such a dependence
of the diffusion rate on the adsorption energy was first reported
qualitatively by Hecht, Grill and co-workers49. By growing 2D
clusters of tetrakis-bromophenyl porphyrins on Au(111), they
found that if the porphyrin precursors (radicals) were formed
before the deposition on Au, the size of the formed clusters was
smaller (Fig. 3a), probably due to stronger chemisorption of the
tetra-radical porphyrins. This demonstrated that hindering random
nucleation is crucial to allow ordered growth, and relies on the
fact that small clusters or islands adsorb more strongly and will
not diffuse nor fuse to form single-crystalline structures. On the
other hand, when engineering of small macromolecular clusters is
sought, then nucleation should be promoted over growth50. In either
case, kinetic and thermodynamic control over the plethora of subproducts that may also be formed is key for synthesis of the desired
material blueprint with nanoscale precision.
A quantitative illustration for promoting ordered growth over
random nucleation has been recently put forward by Bieri, Fasel
and co-workers51. By using a 2D porous-graphene precursor45,
a hexaido cyclohexa-m-phenylene, they showed that crystalline
domains are formed preferentially on Ag(111) and Au(111) whereas
only random networks are observed on Cu(111) — on annealing
H
H
H
H
HH
Reaction
4 nm
Figure 3 | Stitching molecules together into macromolecular
architectures. a, A small organic nanostructure made from eight covalently
bound porphyrins at the Au interface49. b, Potential energy landscape
of two reacting cyclohexa-m-phenylene radicals on Ag (top) and Cu
(bottom) interfaces. The combination of smaller diffusion barriers with
high reactions barriers in Ag results in the formation of crystalline domains
(top right) whereas the opposite results in the formation of amorphous
networks (bottom right). c, Epitaxial synthesis of EDOT trimer along one
commensurate crystallographic direction on Cu(110). Insets: DFT atomic
structure (top; blue bar indicates 1.65-nm scale bar shown in main image)
and a ~12 unit oligomer (bottom). Images in b and c reproduced with
permission from: b, (top) ref. 45, © 2009 RSC; b (bottom) ref. 51, © 2010
ACS; c, ref. 43, © 2010, NAS, USA.
above 525, 575 and 475 K, respectively, for each metal surface
(Fig. 3b). By using Monte-Carlo simulations, the authors were able
to reproduce the exact experimental observations. Assigning high
reaction probabilities causes the simulations to match the Cu porous
graphene-grown structures, whereas lower probabilities match the
more crystalline Ag and Au structures. Further, they compared the
reaction probabilities with DFT transition-state studies: at closing
reaction geometries molecules have a 2.2 eV diffusion barrier on
Cu(111) whereas they have a 0.8 eV barrier on Ag(111). Precursors
on copper readily react after the diffusive process (Fig. 3b, bottom)
but they present an additional 1.8 eV barrier on silver substrates
(Fig. 3b, top). The previous barriers are translated into diffusionlimited rates on copper and reaction-limited rates on silver.
It can be generalized that diffusion-limited polymerizations
may lead to formation of short 1D polymer chains and disordered
networks. One strategy to avoid the problem of random coupling on
account of small diffusion coefficients is to have molecules undergoing
chemisorption onto specific binding sites and subsequently reacting
with adjacent molecules. This condition is reminiscent of epitaxial
growth52. The strategy, however, requires both engineering of the
reaction and the substrate, increasing the programming level of
complexity; Rosei, Perepichka and co-workers demonstrated the
successful polymerization of 3,4-ethylenedioxythiophene (EDOT)
monomers forming uniaxially aligned polymers (PEDOT)43, the
doped form of the latter being among the most employed organic
conductive materials. The polymerization reaction occurred on
heating the EDOT-coated Cu(110) surface at 500 K, leading to
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PERSPECTIVE
NATURE CHEMISTRY DOI: 10.1038/NCHEM.1043
a
b
2 nm
c
20 nm
2 nm
d
3 nm
Figure 4 | Programming surface reactions into extended macromolecular
architectures. a, A ~100-nm-long surface-synthetized polyfluorene chain.
Arrows indicate the covalent bonds on the chain with respect to the
chemical structure. b, A large-area 2D surface covalent polygonal network.
Inset: higher magnification image; 56 × 56 nm2. c, Atomically precise
graphene nanoribbons from small molecule precursors42. d, A covalent
sp2-carbon macromolecule representing the versatility of a programmed
synthetic approach42. Images in a and b reproduced with permission from:
a, ref 47, © 2009 AAAS; b, ref. 54, © 2010 RSC.
PEDOT polymer sizes of up to ~6 nm in length, depending on
the surface coverage. Figure 3c depicts EDOT oligomers perfectly
aligned commensurably with the substrate43. The growth takes
place through the adsorption of the radical precursor, which was
theoretically estimated to amount to an energy of 5.92 eV. Such
high adsorption energy may be responsible for negligible molecular
diffusion at a temperature of about 500 K, thus such reactions may
also be regarded as diffusion-limited, depending only on the rate of
surface coverage.
Reaction-limited on-surface synthesis
From the previous section, it seems that most reactions on surfaces
are diffusion-limited to some extent, given diffusion barriers will
always be present. Besides the magisterial example of Bieri and
Fasel51 in tuning the molecule–substrate interactions to minimize
reactivity, inherent molecular design can be also programmed to
allow fast mobilities. Towards this goal, in a subsequent experiment47,
Hecht, Grill and co-workers designed a laterally methylated fluorene
building block for the synthesis of polyfluorene. The methyl groups
prevent the molecule from adsorbing flat onto the surface, thus
the fast mobility of the molecules allowed the formation of long
polyfluorene chains, greater than 100 nm in length, on polymerization
at 520 K on Au(111) (Fig. 4a). The strategy of achieving high surfacediffusion rates through a non-planar precursor can be also used in
the formation of 2D networks. Introduced by Gutzler, Lackinger and
co-workers53, radical homolysis and subsequent polymerization of
tris(4-bromophenyl)benzene molecules was found to yield small
2D polygonal domains on Cu(111). Blunt, Beton and co-workers54
showed that larger domains may be formed on Au(111), which may
also accommodate fullerenes (Fig. 4b).
One higher level of chemical programming has been recently
demonstrated specifically for the synthesis of long well-defined
graphene nanoribbons. Fasel, Müllen and co-workers42 employed
surface-activated synthesis of molecular building blocks to create
armchair nanoribbons with lengths up to ~40 nm (Fig. 4c).
By changing the chemical structure of the reactant, that is, the
starting molecular building block, they could tailor the structure
434
of the nanoribbons. For instance, a bisanthracene halide building
block yields the straight ribbon depicted in Fig. 4c, whereas using
an asymmetric hexaphenylbenzene halide results in a chevrontype ribbon. Moreover, multiprecursors were successfully used to
finally reproduce a molecular blueprint (Fig. 1b) yielding a complex
macromolecular component of electronic importance (Fig. 4d). In
light of such a proof of principle, new avenues of exploration can
be undertaken for extending the rules governing reactions in a
variety of elements and substrates, that is, a grammar of synthesis
on surfaces. The reaction is also a bright example of a programmed
reaction for fast diffusion rates: this is because the starting
molecular building blocks have a 3D conformation and as such
their clusters may polymerize swiftly at 500 K on Au(111) through
radical formation. Once the final macromolecule length is reached,
a cyclodehydrogenation55 reaction is induced with 700 K heating of
the sample, thus increasing the adsorption energy and consolidating
the graphene nanoribbons.
The biggest challenge after reaction programming and surface
diffusion optimization, as described in the above examples, will
be the reduction of isothermal entropy. Every possible degree of
freedom that can be populated at the reacting temperature may
give a macromolecular product, and only one among the various
populated states may correspond to the desired molecular blueprint
(Fig. 1b). Furthermore, there are a few disadvantages limiting the
practical syntheses of prototype electronic devices from molecular
blueprints made by using surface synthesis protocols. The most
important is the use of the conducting substrates Au(111) and
Cu(111) as 2D supports of the macromolecular device. Secondly,
the Ullmann-like coupling35,44,56,57 mechanism characteristic of the
previous radical additions, has also the drawback of contaminating
the surface with the halogen side-products43,45, unless sufficiently
high temperatures are employed42. In general, until a quantitative
tool for engineering covalent synthesis is established, reaction
products may have to be mechanically processed for their immediate
technological application.
Supermolecule resists or nanoreactors?
Having pointed out the state-of-the-art in atomically cutting and
stitching new materials, solutions for leveraging the fundamental
science presented above to a real technology of complex
macromolecular blueprints are required. Such solutions should
consist of large-area and atomically precise patterns of active electronic
components and interconnect paths wired to the outside world.
At the beginning of this Perspective, we pointed out how
cutting a 2D polymer such as graphene with atomic precision may
be used to reproduce chemically precise blueprints. Indeed it is not
too daunting to foresee inorganic nanowires acting as nanoprobes
for chemically cutting groups of carbon atoms precisely. However,
for efficient circuitry patterning to be possible in the future, more
challenging strategies should be considered. One possibility
relies on the development of highly ordered organic (mono)
layers for polymerization using local external stimuli such as
thermal gradients, high-energy photons or low-energy electrons.
To polymerize or crosslink individual molecules into a precise
macromolecule, the incident high-resolution reaction stimulus
should only affect one molecule at a time. Given that directwriting nanofabrication methods have demonstrated spatial
precision in the 10–30 nm length scale, the size of the single
molecular building block to be successively crosslinked should be
~10 nm, thus allowing the precise formation of a macromolecule
on radiative or thermal reaction. The previous strategy translates
into the synthesis of monomers containing less than 1,500 atoms
or consisting of giant macrocycles, with a defined polymerization
chemistry and hence the term ‘supermolecule resists’. The ultimate
achievement would be to crosslink supermolecule resists through
stimulated topological reactions58.
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PERSPECTIVE
NATURE CHEMISTRY DOI: 10.1038/NCHEM.1043
An approach expected to be developed in the immediate
future involves template control over the on-surface reactions
described previously. This time, the circuit’s source and drain
electrodes can be pre-patterned alongside metallic interconnects
on insulated surfaces. When such electrodes are made of catalytic
materials for surface-assisted chemistry they may be regarded as
2D nanoreactors. In such a scenario, the prior engineering of the
geometry of the nanoreactors will make it possible to polymerize
in situ macromolecules that extend over insulated areas and bridge
the nanoelectrodes, forming a macromolecular transistor channel.
An early example of how on-surface-synthesized molecular
components extend over non-catalytic dielectric areas was reported
by Grill, Hecht and co-workers59, who showed that the polyfluorene
synthesis also occurs in the presence of NaCl clusters. This time,
the on-surface-synthesized polyfluorene chains indeed extend
randomly over insulating NaCl islands.
Essentially, the suggestions we put forward critically depend on
advancements in two fields, reaction engineering, and preparation
of (single crystal) catalytic nanostructures. Reaction engineering
requires fast development of computational chemistry, for example
quantum chemistry and molecular dynamics, both of which depend
on contemporary computational limits. On the other hand, patterning
single crystals and geometries is subject to advances in the rich field
of inorganic epitaxial nanofabrication. Addressing the previous
issues alongside expanding empirical contributions to the fields is
fundamental for the translation of macromolecules into technology.
Summary
The engineering of structurally well-defined individual
electroactive macromolecules can be accomplished by mastering
and combining the top-down and the bottom-up approaches. The
endless combinations of chemistry60 will, in the years to come, offer
an exciting and versatile — yet winding — avenue to molecular
electronics. Indeed bottom-up chemistry already yields GNRs61
and 2D (nano)materials62. Although structurally well-defined
electronic elements can now be accurately reproduced — like long,
monodisperse synthetic nanoribbons — cumbersome stamping
or transferring techniques would be required to manufacture
devices; techniques that can’t be envisaged as strategies for
nanofabrication. We may foresee that one day a single well-defined
covalent macro- or mega-molecule will become, in itself, a logical
computing element. Such a view may only become reality when
experimental and theoretical efforts give access to a library of
surface-programmed reactions, rendering synthetic chemistry at
surfaces a predictive science. Reaction engineering may converge
and blur the horizons of top-down and bottom-up methods into
those of integrated circuitry based, for example, on supermolecule
resists or nanoreactor patterning. In this fascinating view, we see
a joint future effort of experimental and theoretical chemists and
physicists to a priori design sp2-carbon (graphene-like) molecular
blueprints. Here, theory will not only offer the design and modelling
of molecular blueprints but will help actively in the programming
of the chemistry and thermodynamics of reactions at surfaces. In
1965, G. E. Moore described quite accurately that “The future of
integrated electronics is the future of electronics itself ”. Extending
this analogy, the future of macro- or mega-molecular blueprinting
is the future of molecular electronics itself.
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Acknowledgements
We thank Matthias Treier and Veronica Barone for sharing helpful data and
for useful discussions. This work was financially supported by the EC MarieCurie RTNs PRAIRIES (MRTN-CT-2006-035810) and THREADMILL
(MRTN-CT-2006-036040) as well as the ITNs SUPERIOR (PITN-GA-2009-238177)
and GENIUS (PITN-GA-2010-264694), the EC FP7 ONE-P large-scale project no.
212311, the NanoSci-E+ project SENSORS and the International Center for Frontier
Research in Chemistry (FRC, Strasbourg).
Additional information
The authors declare no competing financial interests.
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