Nanoscale
COMMUNICATION
Cite this: Nanoscale, 2015, 7, 13393
Received 26th May 2015,
Accepted 5th July 2015
DOI: 10.1039/c5nr03475b
www.rsc.org/nanoscale
Hybrid van der Waals heterostructures of zero-
dimensional and two-dimensional materials†
Zhikun Zheng,*
a,b
Xianghui Zhang,
a
Christof Neumann,
a
Daniel Emmrich,
a
Andreas Winter,
c
Henning Vieker,‡
a
Wei Liu,
d
Marga Lensen,
e
Armin Gölzhäuser
a
and
Andrey Turchanin*
c
van der Waals heterostructures meet other low-dimensional
materials. Stacking of about 1 nm thick nanosheets with out-of-
plane anchor groups functionalized with fullerenes integrates this
zero-dimensional material into layered heterostructures with a well-
defined chemical composition and without degrading the mecha-
nical properties. The developed modular and highly applicable
approach enables the incorporation of other low-dimensional
materials, e.g. nanoparticles or nanotubes, into heterostructures
significantly extending the possible building blocks.
Molecular assembly of materials with precise control over their
chemical composition, thickness and structure has been in
the focus of physical, chemical and materials science research
already for many years.
1–9
This interest is motivated by engi-
neering materials with controlled functionalities on demand.
To this end, various techniques have been developed. Typical
examples are Langmuir–Blodgett (LB) technique, layer-by-layer
(LbL) assembly, and self-assembled monolayers (SAMs). They
have been widely used to assemble zero- and one-dimensional
(0D and 1D) materials such as small molecules, nanoparticles,
biomolecules, polyelectrolytes and nanotubes/-wires.
1–8
With
the demonstration of free-standing atomically or single-mole-
cularly thick sheets,
10–12
stacking them vertically in a chosen
way serves as a new technique to create designed artificial
materials, the so-called van der Waals (vdW) heterostruc-
tures.
9,13,14
Combination of these 2D sheets including gra-
phene, hexagonal boron nitride or metal chalcogenides has
led to mechanically stable heterostructures with high potential
for applications in sensors and flexible electronics.
9,15
Recent
research efforts have also been focused on the development of
various covalent and non-covalent functionalization
approaches to combine 2D sheets with 0D and 1D
materials.
16–20
However, it remains a major challenge to
assemble stable stacks of 0D/1D materials with 2D sheets
without degrading the mechanical properties of the pristine
sheets. Non-covalent interactions, such as van der Waals inter-
actions and π–πstacking, are not strong enough to stably
immobilize 0D/1D materials on 2D sheets. Thus the adhered
materials can be easily removed by solvent rinsing or even with
time and by environmental moisture.
16,19,20
On the other
hand, strong covalent interactions require a change in the inte-
gral structure of 2D sheets, which degrade their initial mecha-
nical properties.
In this work, we present a modular and broadly applicable
route to create hybrid vdW heterostructures made of individual
∼1 nm thick single molecular sheets, Janus nanomembranes
(JNMs),
13,21
which have well-defined anchor groups on their
opposite sides, see Fig. 1, and other low-dimensional
materials. JNMs are generated via electron irradiation of 4′-
nitro-1,1′-biphenyl-4-thiol (NBPT) SAMs resulting in their
crosslinking via formation of lateral covalent bonds and simul-
taneous conversion of the terminal nitro groups into amino
groups
22
and the subsequent release from the original sub-
strates via the poly(methyl methacrylate) (PMMA) assisted
transfer process.
23,24
The upper side of the JNM has amino
groups (N-side) and the lower side has sulfur species (S-side),
see Fig. 1c; both sides can be independently and chemically
functionalized.
21
Using chemical functionalization of JNMs
with the desired building blocks on their one or both faces
and subsequent stacking, hybrid vdW heterostructures can be
assembled. In our proof-of-concept experiments, we utilize 0D
carbon –fullerene C
60
–as a functional nanomaterial and co-
valently bind to the amino groups of JNMs; we also demonstrate
functionalization of the S-side with Au nanoparticles (NPs), see
Fig. 1d. We fabricate heterostructure stacks of the C
60
–JNM
hybrid and characterize their structural, chemical and mecha-
nical properties by optical microscopy, helium ion microscopy
†Electronic supplementary information (ESI) available. See DOI: 10.1039/
c5nr03475b
‡Current address: CNM Technologies, 33602 Bielefeld, Germany.
a
Faculty of Physics, University of Bielefeld, 33615 Bielefeld, Germany
b
Department of Chemistry and Food Chemistry, TU Dresden, 01069 Dresden,
c
Institute of Physical Chemistry, Friedrich Schiller University Jena, 07743 Jena,
d
Physical Chemistry and Center for Advancing Electronics Dresden, TU Dresden,
01069 Dresden, Germany
e
Institute of Chemistry, Technische Universität Berlin, 10623 Berlin, Germany
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(HIM), X-ray photoelectron spectroscopy (XPS) and mechanical
bulging tests. To make the S-side of JNMs accessible for post-
modification under various experimental conditions, a univer-
sal flip-over procedure for JNMs was developed.
To assemble C
60
–JNM heterostructures, we synthesized
JNMs on gold substrates (JNM/Au), immobilized C
60
onto the
N-side of the JNMs, and stacked the C
60
–JNM hybrids on top
of each other (see ESI†for details). The successful immobili-
zation of C
60
onto JNM/Au was confirmed by XPS. Fig. 2a shows
the XP spectra of a JNM/Au. The C1s signal consists of several
peaks with binding energies (BEs) at 284.2 eV and 285.3 eV,
which are due to the aromatic carbon and the C–S/C–Nbonds,
respectively; and the aromatic shake-up satellites at 287–290
eV.
24
The N1s signal at 399.3 eV is characteristic for amino
groups. The S2p signal shows the presence of two sulfur species
with the S2p
3/2
BEs at 162.0 and 163.2 eV, which are due to thio-
lates and sulfides/disulfides formed upon irradiation,
25
respect-
ively. The effective thickness of a JNM calculated from the
attenuation of the Au4f
7/2
signal is about 1.1 nm.
26
In Fig. 2b,
the XP spectra of a JNM with C
60
grafted to the amino groups
are presented.
27
The successful grafting is confirmed by the
corresponding changes of the respective XP signals. The total
intensity of the C1s signal increases by ∼30% and a new N1s
peak at ∼400.3 eV appears due to the formation of C–N
bonds.
27–29
The intensity ratio between this peak and the total
N1s intensity is ∼30%, which indicates the percentage of amino
groups on forming chemical bonds with C
60
. Intensity of the
S2p signal decreases showing an increase of the hybrid thick-
ness (see Table S1†for thickness change).
To demonstrate that C
60
–JNMs can be released from their
original substrate and further used for fabrication of the
heterostructures, we tested their transfer onto 285 nm SiO
2
/Si
substrates by the PMMA assisted process.
24
These substrates
were chosen as they enable the observation of JNMs by optical
interference (see Fig. S1a†).
14
Fig. 2c shows XP spectra of the
transferred C
60
–JNM. The characteristics of the XP signals are
similar to those of the pristine C
60
–JNM/Au. A slight increase
of the C1s peak at ∼288.3 eV is observed, which is most likely
due to the presence of some PMMA residuals after the trans-
fer.
30
The S2p
3/2
signal at 162.0 eV disappears and the inten-
Fig. 1 Schematic representation of the heterostructure assembly. (a) Formation of a NBPT SAM on a gold substrate. (b) Electron irradiation induced
crosslinking and reduction of the terminal nitro groups into amino groups. (c) Formation of a free-standing JNM with the terminal N- and S-faces.
(d) Functionalization of the N- and S-faces with C
60
and AuNP, respectively. (e) Assembly of a (C
60
–JNM)
n
(here n= 3) hybrid heterostructure by
mechanical stacking. Color code for atoms: black –carbon, grey –hydrogen, blue –nitrogen, green –sulfur, and red –oxygen.
Fig. 2 XPS characterization. (a) JNM on the original gold substrate. (b)
C
60
–JNM on the original gold substrate. C
60
–JNM monolayer/multilayer
after transfer onto 285 nm SiO
2
/Si (monolayer (c), bilayer (d) and trilayer
(e)). Intensities of the S2p and N1s spectra were multiplied by 7.
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sity of the S2p
3/2
signal at 163.2 eV increases significantly due
to the transformation of thiolates into sulfides/disulfides or
into unbound thiols during the transfer process.
21
Anew
doublet appears with S2p
3/2
at 167.2 eV caused by the oxi-
dation of thiolates/sulfides/disulfides into the sulfonic
group.
31
Note that the sulfonic group is negatively charged in
water, which can be used for the functionalization of the
S-side of JNMs by electrostatic interactions.
For the fabrication of cm
2
-sized patterned C
60
–JNM hetero-
structures on 285 nm SiO
2
/Si, a simple method was applied.
C
60
–JNM sheets on Au/mica substrates were cut with scissors
into rectangular stripes of ∼0.5 cm width and then the sheets
were transferred onto the Si-wafer by putting them on top of
each other in different orientations. This procedure leads to
the formation of regions with either no, one, two or three
sheets (Fig. S1a†). Note that the uniform contrast within the
areas with varying numbers of C
60
–JNM sheets reflects their
homogeneous thickness.
As only the electron irradiated areas of NBPT SAMs are con-
verted into JNMs and there is no lateral crosslinking between
molecules in the non-irradiated areas, it is possible by selective
electron irradiation to pattern JNMs, functionalize them with
C
60
and then transfer the patterned C
60
–JNM onto a new sub-
strate (Fig. S1b†). Such a procedure makes it possible to
produce the JNM-based hybrids in any shape without
additional resist materials either by using electron irradiation
through stencil masks, as in this experiment, or by standard
electron beam lithography.
The assembled heterostructure stacks were characterized by
XPS. We found no significant changes in the shapes of C1s,
S2p and N1s signals for the bi-layer and the tri-layer of C
60
–
JNM (Fig. 2d and e), which indicates that each layer has a
similar chemical composition. The obtained effective thick-
ness of the bi-layer and tri-layer stacks is ∼3.7 nm and
∼5.4 nm, respectively, which confirms further homogeneous
contributions of each layer to the total structure. This hom-
ogeneity benefits from the high reproducibility by functionali-
zation of mechanically stable JNMs, which is difficult to
achieve employing the layer-by-layer growth on conventional
SAMs.
32–34
To quantitatively characterize the mechanical properties of
individual C
60
–JNMs and their heterostructures, they were
studied by mechanical bulge tests. To this end, the sheets were
transferred onto a silicon substrate with an array of square
shaped orifices. Fig. 3a shows a helium ion microscopy (HIM)
image of a C
60
–JNM hybrid. An orifice with the spanned C
60
–
JNM is observed (marked “freestanding”), which indicates that
the hybrid can support its own weight and preserve its mecha-
nical integrity. Apart from the large homogeneous area, some
wrinkles or ruptures (Fig. 3b and c) are observed, which are
typical for mechanically robust nanosheets.
10
Fig. 3d shows a
homogeneous freestanding JNM/(C
60
–JNM)
3
heterostructure
spanning over an orifice with dimensions of 40 × 44 μm
2
. The
heterostructure in Fig. 3e shows some wrinkles, which increase
the imaging contrast and help to identify the freestanding
membrane by HIM. Note that only the homogeneous struc-
tures as in Fig. 3d were employed for bulge tests with an
atomic force microscope (AFM). To ensure that the interaction
between a (C
60
–JNM)
n
and an AFM tip is the same as that for
an individual JNM, a JNM was placed on top of the respective
heterostructures forming the JNM/(C
60
–JNM)
n
stacks. The
testing was performed by adjusting an AFM tip to the nano-
Fig. 3 Helium ion microscopy (HIM) imaging of C
60
–JNM heterostructures and their mechanical properties. (a) HIM image of a C
60
–JNM on a Si
substrate with orifices. An orifice with dimensions 40 × 44 μm
2
is marked here as “free-standing”. (b) Magnified HIM image of the C
60
–JNM bound-
ary; the corresponding place is marked in (a) with an arrow. (c) Magnified HIM image of the central part of the C
60
–JNM; the corresponding place is
marked in (a) with an arrow. In (d) and (e) HIM images of an JNM–(C
60
–JNM)
3
heterostructure spanning a Si window are shown. In (d) the nano-
membrane is homogeneous whereas in (e) a fold can be recognized. (f) A schematic diagram of the bulge test set-up. (g) Typical pressure-deflection
curves for a JNM–(C
60
–JNM)
2
heterostructure. (h) Young’s moduli of JNM, C
60
–JNM and JNM–(C
60
–JNM)
n
(n= 1, 2, and 3).
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membrane center,
35,36
as schematically shown in Fig. 3f.
Different N
2
pressures are applied beneath the membrane, and
its corresponding deflection is then recorded by AFM. Fig. 3g
shows a typical pressure-deflection curve for a JNM/(C
60
–JNM)
2
heterostructure (see Fig. S2†for JNM, C
60
–JNM and JNM/(C
60
–
JNM)
n
,n= 1 and 3). By fitting multiple curves to a pressure-
deflection equation for rectangular/square membranes,
35,36
Young’s modulus (E
Young
) can be extracted (Fig. 3h and
Table S1†). First, we compare the mechanical properties of
pristine JNM with C
60
–JNM. To this end, the in-plane elastic
modulus (E
2d
) has to be considered.
37–39
It is equal to E
Young
multiplied by the thickness of the sheet. The obtained E
2d
values for JNM (9.9 ± 1.7 N m
−1
)andC
60
–JNM(11.6±1.7Nm
−1
)
are of the same magnitude, which shows that the mechanical
robustness of a JNM is not diminished upon its covalent
functionalization. Next, we compare the mechanical properties
of multilayered stacks considering the respective E
Young
values.
37
E
Young
for JNM/(C
60
–JNM)
1
, JNM/(C
60
–JNM)
2
and
JNM/(C
60
–JNM)
3
are 7.5 ± 1.8 GPa, 7.2 ± 1.3 GPa and 8.7 ± 1.5
GPa, respectively (Fig. 3h). It can be clearly seen that within
the measurement accuracy the Young’s moduli of the JNM/
(C
60
–JNM)
n
(n= 1, 2 and 3) heterostructures have similar
values demonstrating that the mechanical properties are not
degraded upon the assembly of the hybrid JNMs into stacks.
To show that for the assembly of hybrid heterostructures
the S-side of JNMs can also be employed, we studied its
functionalization with Au NPs (Fig. 1c and Fig. 4). Negatively
charged Au NPs with sizes of ∼55 and 16 nm were used to this
end. As the S-side of a JNM due to the presence of sulfonic
groups is also negatively charged, a positively charged adhesive
polyelectrolyte layer of poly(diallyldimethylammonium chlor-
ide) was added to immobilize the negatively charged Au NPs.
We employed scanning transmission ion microscopy (STIM) to
image the hybrid nanomembranes suspending hexagonal
grids (∼25 µm) with the functionalized S-side oriented
upwards. From statistical analysis we estimate the average
coverage of the 55 and 16 nm-sized Au NPs on JNMs to be
∼15% and ∼50%, respectively, showing that the coverage corre-
lates with the NP size. As a wide variety of materials can be
immobilized by electrostatic interactions,
2
this strategy pro-
vides a flexible route to incorporate different materials into
JNM-based hybrids. The modification of the S-side of JNMs
with the above-described method needs PMMA as a protection
layer, which restricts the modification to conditions
compatible with this layer. In case such a layer cannot be
employed, the JNM can also be flipped over and transferred
onto a new solid substrate where the originally bottom S-side
becomes the terminal one (Fig. S3–5†).
Conclusions
In summary, we have presented a modular and highly appli-
cable approach for the assembly of cm
2
-sized vdW hybrid het-
erostructures. This approach is based on the utilization of
∼1 nm thick bifacial and mechanically stable JNMs, their
chemical functionalization and subsequent stacking into
layered heterostructures. In the present study the heterostruc-
tures of JNMs with C
60
and gold nanoparticles were investi-
gated. The possibility of bifacial chemical functionalization of
Fig. 4 JNMs functionalized with Au nanoparticles on the S-face. Helium ion microscope images acquired in the secondary electron (SE) mode and
scanning transmission ion mode (STIM). (a) SE image of JNMs functionalized with 55 nm Au nanoparticles and transferred onto a grid. (b) and (c)
STIM images show that the nanoparticles are uniformly distributed with an average coverage of ∼15%. (d) SE image of JNMs functionalized with
16 nm Au nanoparticles and transferred onto a grid. (e) and (f) STIM images showing that the nanoparticles are uniformly distributed with a coverage
of ∼50%. Dark areas (see the arrow in (e)) are residues from sample preparation.
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JNMs paves the way to hybrid vdW heterostructures with a
variety of other 0D and 1D materials.
Acknowledgements
This work was supported by the Deutsche Forschungsge-
meinschaft (SPP “Graphene”and Heisenberg Programme), the
Volkswagenstiftung and the Alexander von Humboldt Foun-
dation (Sofja Kovalevskaja Award to MCL). Z. Z. and
X. Z. contributed equally to this work. We thank Prof. Xinliang
Feng (TU Dresden) for fruitful discussions.
Notes and references
1 K. B. Blodgett, J. Am. Chem. Soc., 1934, 56, 495.
2 G. Decher, Science, 1997, 277, 1232.
3 K. Ariga, J. P. Hill and Q. Ji, Phys. Chem. Chem. Phys., 2007,
9, 2319.
4 S. Srivastava and N. A. Kotov, Acc. Chem. Res., 2008, 41,
1831.
5 Z. Tang, Y. L. Wang, P. Podsiadlo and N. A. Kotov, Adv.
Mater., 2006, 18, 3203.
6 J. Sagiv, J. Am. Chem. Soc., 1980, 102, 92.
7 J. C. Love, L. A. Estroff, J. K. Kriebel, R. G. Nuzzo and
G. M. Whitesides, Chem. Rev., 2005, 105, 1103.
8 A. Ulman, Introduction to Ultrathin Organic Films, Academic,
San Diego, CA, 1991.
9 A. K. Geim and I. V. Grigorieva, Nature, 2013, 499, 419.
10 K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth,
V. V. Khotkevich, S. V. Morozov and A. K. Geim, Proc. Natl.
Acad. Sci. U. S. A., 2005, 102, 10451.
11 J. Sakamoto, J. van Heijst, O. Lukin and A. D. Schluter,
Angew. Chem., Int. Ed., 2009, 48, 1030.
12 W. Eck, A. Küller, M. Grunze, B. Völkel and A. Gölzhäuser,
Adv. Mater., 2005, 17, 2583.
13 (a) M. Woszczyna, A. Winter, M. Grothe, A. Willunat,
S. Wundrack, R. Stosch, T. Weimann, F. Ahlers and
A. Turchanin, Adv. Mater., 2014, 26, 4831;
(b) C. T. Nottbohm, A. Turchanin, A. Beyer, R. Stosch and
A. Gölzhäuser, Small, 2011, 7, 874.
14 (a) H. Yin, S. Zhao, K. Zhao, A. Muqsit, H. Tang, L. Chang,
H. Zhao, Y. Gao and Z. Tang, Nat. Commun., 2015, 6, 6430;
(b) H. Tang, J. Wang, H. Yin, H. Zhao, D. Wang and
Z. Tang, Adv. Mater., 2015, 27, 1117; (c) H. Yin, S. Zhao,
J. Wan, H. Tang, L. Chang, L. He, H. Zhao, Y. Gao and
Z. Tang, Adv. Mater., 2013, 25, 6270.
15 T. Georgiou, R. Jalil, B. D. Belle, L. Britnell,
R. V. Gorbachev, S. V. Morozov, Y.-J. Kim, A. Gholinia,
S. J. Haigh, O. Makarovsky, L. Eaves, L. A. Ponomarenko,
A. K. Geim, K. S. Novoselov and A. Mishchenko, Nat. Nano-
technol., 2013, 8, 100.
16 V. Georgakilas, M. Otyepka, A. B. Bourlinos, V. Chandra,
N. Kim, K. C. Kemp, P. Hobza, R. Zboril and K. S. Kim,
Chem. Rev., 2012, 112, 6156.
17 D. Voiry, A. Goswami, R. Kappera, C. C. C. Silva, D. Kaplan,
T. Fujita, M. Chen, T. Asefa and M. Chhowalla, Nat. Chem.,
2015, 7, 45.
18 S. Jiang, S. Butler, E. Bianco, O. D. Restrepo, W. Windl and
J. E. Goldberger, Nat. Commun., 2014, 5,1.
19 H. Y. Mao, Y. H. Lu, J. D. Lin, S. Zhong, A. T. S. Wee and
W. Chen, Prog. Surf. Sci., 2013, 88, 132.
20 J. Du, S. Pei, L. Ma and H.-M. Cheng, Adv. Mater., 2014, 26,
1958.
21 Z. Zheng, C. T. Nottbohm, A. Turchanin, H. Muzik,
A. Beyer, M. Heilemann, M. Sauer and A. Gölzhäuser,
Angew. Chem., Int. Ed., 2010, 49, 8493.
22 W. Eck, V. Stadler, W. Geyer, M. Zharnikov, A. Gölzhäuser
and M. Grunze, Adv. Mater., 2000, 12, 805.
23 A. Turchanin and A. Gölzhäuser, Prog. Surf. Sci., 2012, 87,
108.
24 A. Turchanin, A. Beyer, C. T. Nottbohm, X. Zhang,
R. Stosch, A. S. Sologubenko, J. Mayer, P. Hinze,
T. Weimann and A. Gölzhäuser, Adv. Mater., 2009, 21, 1233.
25 A. Turchanin, D. Käfer, M. El-Desawy, C. Wöll, G. Witte and
A. Gölzhäuser, Langmuir, 2009, 25, 7342.
26 M. Schnietz, A. Turchanin, C. T. Nottbohm, A. Beyer,
H. H. Solak, P. Hinze, T. Weimann and A. Gölzhäuser,
Small, 2009, 5, 2651.
27 P. J. Moriarty, Surf. Sci. Rep., 2010, 65, 175.
28 K. M. Chen, W. B. Caldwell and C. A. Mirkin, J. Am. Chem.
Soc., 1993, 115, 1193.
29 W. B. Caldwell, K. Chen, C. A. Mirkin and S. J. Babinec,
Langmuir, 1993, 9, 1945.
30 A. Pirkle, J. Chan, A. Venugopal, D. Hinojos,
C. W. Magnuson, S. McDonnell, L. Colombo, E. M. Vogel,
R. S. Ruoffand R. M. Wallace, Appl. Phys. Lett., 2011, 99,
122108.
31 A. P. Terzyk, Colloids Surf., A, 2001, 177, 23.
32 S. Heid, F. Effenberger, K. Bierbaum and M. Grunze, Lang-
muir, 1996, 12, 2118.
33 N. Tillman, A. Ulman and T. L. Penner, Langmuir, 1989, 5,
101.
34 H. Sugimura, H. Yonezawa, S. Asai, Q. W. Sun, T. Ichii,
K. H. Lee, K. Murase, K. Noda and K. Matsushige, Colloids
Surf., A, 2008, 321, 249.
35 X. H. Zhang, A. Beyer and A. Gölzhäuser, Beilstein
J. Nanotechnol., 2011, 2, 826.
36 X. H. Zhang, C. Neumann, P. Angelova, A. Beyer and
A. Gölzhäuser, Langmuir, 2014, 30, 8221.
37 C. Lee, X. Wie, J. W. Kysar and J. Hone, Science, 2008, 521,
385.
38 Z. Zheng, C. S. Ruiz-Vargas, T. Bauer, A. Rossi, P. Payamyar,
F. Schiffmann, J. VandeVondele, A. Stemmer, J. Sakamoto
and A. D. Schlüter, Macromol. Rapid Commun., 2013, 34,
1670.
39 Z. Zheng, L. Opilik, F. Schiffmann, W. Liu, G. Bergamini,
P. Ceroni, L. Lee, A. Schütz, J. Sakamoto, R. Zenobi,
J. VandeVondele and A. D. Schlüter, J. Am. Chem. Soc.,
2014, 136, 6103.
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