Controlled fabrication of fullerene C60 into microspheres of nanoplates through porphyrin-polymer-assisted self-assembly

Article abstract of DOI:10.1002/anie.200904985

Holey balls! Novel microspheres made up of nanoplates have been fabricated by porphyrin-polymer-assisted supramolecular self-assembly of C₆₀. The obtained C₆₀ microspheres are single-crystalline and exhibit pure fee structure. This i

Full text of DOI:10.1002/anie.200904985

Communications
DOI: 10.1002/anie.200904985
Fullerene Nanostructures
Controlled Fabrication of Fullerene C60 into
Microspheres of Nanoplates through Porphyrin-Poly-
mer-Assisted Self-Assembly**
Xuan Zhang and Masayuki Takeuchi*
Angewandte
Chemie
9646
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2009, 48, 9646 –9651

Angewandte
Chemie
Fullerene (C60) has drawn much attention in materials science
because of its excellent electronic and mechanical proper-
ties.[1] C60 has many potential applications in various devices,
such as photovoltaic cells,[2] organic transistors,[3] organic
light-emitting diodes (OLEDs),[4] and sensors.[5] Recently, it
has been recognized that the device performance, for
example, the power conversion efficiency in a bulk hetero-
junction solar cell, strongly depends on the morphology of the
photoactive C60 layer.[6] As a consequence, much effort has
been devoted to the controlled construction of well-defined
C60 nano- and microstructures. One-dimensional (1D) C60
rods,[7] wires,[8] whiskers,[9] tubes,[10] two-dimensional (2D)
sheets,[11] and three-dimensional (3D) spheres[12] have been
synthesized through the direct evaporation of solutions of
pure C60 on substrates as well as by the template method,[10a]
a
solid–vapor process,[11c] a liquid–liquid interfacial precipita-
tion method,[9c] and a reprecipitation method.[7d] These
approaches, however, are usually accompanied by drawbacks
on the limited modulation of shape and dimensionality, and
particularly the fabrication of complex superstructures.
Self-assembly has proved to be an efficient approach to
create hierarchical supramolecular architectures with con-
trolled dimensionality and complex superstructures.[13]
Recently, this technique has been applied successfully to the
fabrication of supramolecular architectures of amphiphilic C60
derivatives,[14,15] wherein 1D fibers, 2D sheets, 3D spheres, and
flowerlike objects were obtained in a controlled fashion from
C
60 derivatives bearing multiple alkyl chains.[15] Although the
Scheme 1. Molecular structures of porphyrin polymer (Por) and related
self-assembly of amphiphilic C60 derivatives has led to the
fabrication of complex superstructures of novel shape, it is
necessary to covalently attach multiple functional groups on
the surface of C60 by chemical modification. Alternatively, the
noncovalent functionalization of unmodified C60 by making a
supramolecular composite would control the morphology and
yet retain the intact C60 molecule. Whiskers and spheres have
been obtained recently from a blend of C60 with poly(p-
phenylene) derivatives;[16] however, the crystal structure of
these objects was dominated by polymer packing. The
controlled fabrication of architectures of unmodified C60
with complex superstructures is still a challenging task.
Herein we report that a porphyrin polymer[17] (Por,
Scheme 1) was employed to control the assembly of C60
utilizing supramolecular interactions.[18] Unprecedentedly,
well-defined 1D rods, 2D sheets, and complex 3D structures
were successfully obtained from Por/C60 solutions under
different experimental conditions. In particular, C60 micro-
spheres comprising nanoplate structures with a face-centered
monomers (M1 and M2). The number-average molecule mass (Mn) of
Por is estimated as Mn =35000 by comparison with a polystyrene
standard.
cubic (fcc) structure and single-crystalline in nature were
fabricated in a controllable fashion. Based on our analysis of
captured intermediates, we propose a mechanism for the
formation of C60 microspheres that resembles a bio-inspired
mechanism of mineralization.
Self-organized objects of supramolecular composites
between Por and C60 were prepared by slow evaporation of
a toluene solution of Por and C60 on a Si wafer under toluene
atmosphere (see the Experimental Section). Figure 1 shows
field emission scanning electron microscopy (FE-SEM)
images of the objects obtained. Diverse micrometer-sized
morphologies such as 1D rods and 2D sheets as well as 3D
complex superstructures were obtained under different
experimental conditions (see Figure 1 and Figure S1 in the
Supporting Information). Evaporation of separate toluene
solutions of pure C60 and Por provided rods and fibrous
objects, respectively, whereas irregular-shaped aggregates
formed from the solutions of C60 with the monomers M1,
M2, or a mixture of M1 and M2 (Figure S2 in the Supporting
Information). These results indicate that both C60 and the
polymeric structure of Por contribute to the formation of
these unique morphologies, which can be finely modulated by
simply changing experimental conditions such as the weight
ratio and the concentrations of Por and C60.
[*] Dr. X. Zhang, Dr. M. Takeuchi
Macromolecules Group, Organic Nanomaterials Center
National Institute for Materials Science
Tsukuba 305-0047 (Japan)
Fax: (+81)29-859-2101
E-mail: takeuchi.masayuki@nims.go.jp
[**] We thank Dr. K. Sugiyasu and Dr. T. Nakanishi for valuable
comments. This study was supported partially by KAKENHI (area
2107, 21108010 to M.T.) from the Ministry of Education, Culture,
Science, Sports, and Technology (Japan).
When the weight ratio of Por to C60 (0.5 mgmLÀ1, [C60] =
0.69 mm) was fixed at 1:2 ([Por]unit/[C60] = 1:6; [Por]unit
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.200904985.
Angew. Chem. Int. Ed. 2009, 48, 9646 –9651
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 9647

Communications
enables us to transfer the resultant objects to any substrate
such as a TEM grid (vide infra). These results indicate that the
formation of microspheres is substrate-independent, and the
objects can be prepared on different substrates for various
applications. In addition, neither light nor the water content
of the toluene solvent affected the resultant morphology;
similar microspheres composed of nanoplates were obtained
in the dark and also from water-saturated toluene solution. In
contrast, the drying speed, temperature, and solvent for the
Por/C60 blend strongly influence the resultant morphologies.
The microsphere morphology dominated only when the
drying process continued over 10 hours under a saturated
toluene atmosphere (see Figure S8 in the Supporting Infor-
mation). Without sufficient toluene vapor, disklike objects
were mainly formed, suggesting that these objects are
intermediates. Meanwhile, the microsphere objects were
obtained in the temperature range of 15–268C; at either
lower (108C) or higher (308C) temperatures, or with other
solvents such as benzene and p-xylene, we did not observe
microspheres on the Si surface.
Figure 1. SEM images of diverse objects of Por–C60 blend obtained
under different experimental conditions. Concentrations of C60 and Por
(in mgmLÀ1): a) 0.5, 0.05, b) 0.05, 0.05, c) 0.025, 0.25, d) 0.25, 0.25,
e) 0.5, 0. 25, f) 0.75, 0.25, respectively.
denotes the concentration of a repeating unit of Por in the
polymer shown in Scheme 1), highly monodisperse and
uniform microspheres (average size ca. 5 mm) comprising
nanoplates structures were predominantly obtained on the Si
wafer (Figure 2), accompanied by disklike objects (Figure S3
To obtain further insight into how C60 and Por organize in
the microspheres, we conducted Raman spectroscopy, X-ray
diffraction (XRD), and transmission electron microscopy
(TEM). Figure 3a shows Raman spectra recorded for micro-
spheres on a Si wafer. The corresponding spectra of C60 rods
Figure 2. SEM images of C60 microspheres of nanoplates. Concentra-
tions of C60 and Por (in mgmLÀ1): 0.5 and 0.25, respectively.
in the Supporting Information). Energy-dispersive X-ray
(EDX) spectroscopy analysis and element mapping revealed
that carbon is the main component of the microspheres, as
indicated by the prominent C peak; additional weak peaks
reveal the presence of O and Zn in the objects, indicating the
concomitance of Por in these microspheres (Figure S4 in the
Supporting Information and vide infra). As shown in Figure 2,
the microspheres range from 4–7 mm in diameter, and the
platelike building units were revealed to be 200–300 nm thick
from SEM images. Moreover, the size of the microspheres can
be fine-tuned by changing the concentration of C60. When the
C60 concentration was increased from 0.25 to 0.5, 1.0, and
2.0 mgmLÀ1, the average particle size increased from 3 to 5, 7,
and 10 mm, respectively, while the weight ratio between Por
and C60 was maintained at 1:2 (Figure S5 in the Supporting
Information). When we diluted the C60 solution to
0.1 mgmLÀ1, rodlike objects were mainly obtained.
Microspheres analogous to those obtained on the Si wafer
were also found on other substrates such as glass, indium tin
oxide coated glass, mica, and Al foil (Figure S6 in the
Supporting Information). Remarkably, both disk and micro-
sphere morphologies were also obtained from the slow
evaporation of a Por/C60 solution in toluene at the air–water
interface (Figure S7 in the Supporting Information), which
Figure 3. Raman spectra (a) and XRD patterns (b) of C60 powder, rods,
and microspheres.
obtained without Por under the same conditions and
untreated C60 powder are also shown for comparison. The
characteristic band for the Ag(2) pentagonal pinch mode in
the Raman spectra around 1460 cmÀ1 was observed for all of
microspheres, C60 rods, and untreated C60 (Figure 3a). This
indicates that only monomeric C60 molecules are involved in
these objects because the Ag(2) line shifts to lower frequency
in polymerized C60.[19] It should be noted, however, that the
Ag(2) band showed a substantial 3 cmÀ1 shift for microspheres
(1466 cmÀ1) relative to those observed for C60 rods and
untreated C60 (both at 1463 cmÀ1). This shift may be attributed
to supramolecular interactions between the porphyrin poly-
mer and C60. X-ray diffraction (XRD) patterns for micro-
spheres recorded on a Si substrate are shown in Figure 3b.
The well-defined XRD patterns of the microspheres match
very well with those of C60 rods and untreated C60. Thus these
patterns were readily assigned as a classic fcc structure: four
strong peaks are indexed as (111), (220), (311), and (222) from
the fcc lattices, indicating that the microspheres have pure fcc
crystal structure. In contrast, previously obtained C60 crystals
9648 www.angewandte.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2009, 48, 9646 –9651

Angewandte
Chemie
usually have a mixed phase of the
fcc and hexagonal structure-
s.[9,10a,11a,b]
As the obtained microspheres
are too large to observe by TEM,
disklike intermediates were char-
acterized by this method. TEM
samples were prepared by direct
evaporation of toluene solutions of
Por/C60 on a carbon-coated Cu grid
(Figure 4 and Figure S9 in the Sup-
porting Information) or by trans-
ferring objects formed at the air–
water interface to a grid (Fig-
ure S10 in the Supporting Informa-
tion). Figure 4 shows TEM and
high-resolution TEM (HR-TEM)
images of disklike objects. The
selected area electron diffraction
(SAED) patterns show regular hex-
agonal diffraction spots, and we
confirm that these objects are
single-crystalline in nature (inset
Figure 5. Studies on the plausible mechanism for the formation of C60 microspheres. SEM (a) and
AFM (b) images of particles obtained after fast drying within 1 min in air. SEM (c) and AFM (d)
images of disks obtained under less toluene vapor and dried within 6 h. SEM (e,g) and TEM (f)
images of disklike intermediate objects. h) SEM images of ball-shaped microspheres. (i) Plausible
mechanism for the formation of C60 microspheres from multilayer disks of nanoparticle aggregates.
inantly observed accompanied by disk- or incomplete ball-
like objects (Figure 5g, h and Figures S3 and S8 in the
Supporting Information). Based on these results, we propose
a process for microsphere growth (Figure 5i). During the slow
evaporation of the homogeneous composite solution, the
initially formed nanoparticle aggregates assemble to form a
micrometer-sized multilayer disk. This intermediate structure
provides a platform for the formation of another disk
composed of freshly formed nanoparticle aggregates perpen-
dicular to the initial platform; finally a complex microsphere
of nanoplates is constructed by an oriented-attachment
growth mechanism.[20] The oriented-attachment process
involves the spontaneous self-organization of adjacent par-
ticles to share a common crystallographic orientation, and
subsequent fusion of these particles at a planar interface.[20]
We infer that Por plays multiple roles in the present
system, such as interacting with C60 to preorganize C60
molecules around polymer chain by molecular recognition
and then assisting in the self-assembly of C60 molecules to
disklike objects and microspheres.[21] It is noteworthy to
mention that EDX analysis (Figure S4 in the Supporting
Information) clearly indicates that the microspheres contain
only minor amounts of Por (the Zn/C atomic ratio is 1:1357,
corresponding ca. [Por]unit/[C60] = 1:20). This could be tenta-
tively explained by the exclusion of Por during the formation
of crystals C60. This step resembles stages in bio-inspired
mineralization,[22] where polymer additives exert a powerful
influence on crystal growth and the self-assembly of super-
structures but are predominantly excluded from the crystal-
line phase.[22,23] This approach has been used extensively for
the synthesis of inorganic crystals having complex shapes and
was also recently extended to the synthesis and crystallization
of organic dyes.[24]
Figure 4. TEM (a) and HR-TEM (b) images of C60 disks. The inset in
(a) shows the SAED pattern.
in Figure 4a). The HR-TEM image recorded near the edge of
the disk indicates well-defined lattice fringes with an inter-
planar spacing of 0.81 nm (Figure 4b), which matches well
with the XRD result (Figure 3b) and corresponds to the
diameter of C60.
The capture of intermediate objects enabled us to under-
stand the assembly procedure. The drying process was
controlled by the amount of toluene vapor in order to capture
intermediate structures. We noticed that small particle
aggregates 20–200 nm in height and 200–500 nm in diameter
(according to AFM measurements) were mainly obtained
when a toluene solution of Por/C60 (1:2 weight ratio) was
dried within 1 min in air without toluene vapor or by spin-
coating on a Si substrate (Figure 5a, b, and Figure S11 in the
Supporting Information).
When the Por/C60 solution was dried within 6 hours under
less toluene vapor (200 mL), micrometer-sized multilayer
disks with a thickness of 40–200 nm and a diameter of
2.5 mm were predominantly obtained (Figure 5c–f and Fig-
ure S12 in the Supporting Information). Moreover, with an
excess of toluene vapor (500 mL), the Por/C60 solution dried
completely over 10 hours and microspheres were predom-
In conclusion, novel C60 microspheres composed of nano-
plates have been fabricated by porphyrin-polymer-assisted
Angew. Chem. Int. Ed. 2009, 48, 9646 –9651
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 9649

Communications
Zandler, N. K. Subbaiyan, K. Ohkubo, S. Fukuzumi, J. Am.
Chem. Soc. 2008, 130, 16959 – 16967.
supramolecular self-assembly. We have shown that the
obtained C60 microspheres are single-crystalline and exhibit
pure fcc structure; this is a rare example of a hierarchical
supramolecular architecture with a complex superstructure
fabricated from the self-assembly of unmodified C60. The
possible formation mechanism was also described based on
the analysis of captured intermediates. Namely, the oriented
attachment of initially formed nanoparticles leads to the
growth of micrometer-sized disks, providing a platform for
further disk growth and final transformation into micro-
spheres. The porphyrin polymer Por was speculated to play
multiple roles such as preorganizing and assisting the self-
assembly of C60 molecules in a “programmed” fashion to form
microspheres; it is then excluded from the crystalline phase.
The approach we have presented in this study paves the way
to the fabrication of new complex supramolecular architec-
tures of fullerenes as well as other organic molecules by
employing various functional polymers.
[5] For sensors: a) G. Yu, J. Wang, J. McElvain, A. J. Heeger, Adv.
Mater. 1998, 10, 1431 – 1434; b) R. N. Goyal, V. K. Gupta, N.
Bachheti, Anal. Chim. Acta 2007, 597, 82 – 89; c) S. Nagl, C.
Baleizao, S. M. Borisov, M. Schꢁferling, M. N. Berberan-Santos,
O. S. Wolfbeis, Angew. Chem. 2007, 119, 2368 – 2371; Angew.
Chem. Int. Ed. 2007, 46, 2317 – 2319.
[6] a) M. Campoy-Quiles, T. Ferenczi, T. Agostinelli, P. G. Etch-
egoin, Y. Kim, T. D. Anthopoulos, P. N. Stavrinou, D. D. C.
Bradley, J. Nelson, Nat. Mater. 2008, 7, 158 – 164; b) H. Hoppe,
N. S. Sariciftci, J. Mater. Chem. 2006, 16, 45 – 61; c) J. Peet, M. L.
Senatore, A. J. Heeger, G. C. Bazan, Adv. Mater. 2009, 21, 1521 –
1527.
[7] For C60 rods: a) L. Wang, B. Liu, D. Liu, M. Yao, Y. Hou, S. Yu, T.
Cui, D. Li, G. Zou, A. Iwasiewicz, B. Sundqvist, Adv. Mater.
2006, 18, 1883 – 1886; b) H.-X. Ji, J.-S. Hu, L.-J. Wan, Q.-X. Tang,
W.-P. Hua, J. Mater. Chem. 2008, 18, 328 – 332; c) Y. Jin, R. J.
Curry, J. Sloan, R. A. Hatton, L. C. Chong, N. Blanchard, V.
Stolojan, H. W. Krotob, S. R. P. Silva, J. Mater. Chem. 2006, 16,
3715 – 3720; d) Z. Tan, A. Masuhara, H. Kasai, H. Nakanishi, H.
Oikawa, Jpn. J. Appl. Phys. 2008, 47, 1426 – 1428.
[8] For C60 wires: a) J. Geng, W. Zhou, P. Skelton, W. Yue, I. A.
Kinloch, A. H. Windle, B. F. G. Johnson, J. Am. Chem. Soc. 2008,
130, 2527 – 2534; b) Y.-G. Guo, C.-J. Li, L.-J. Wan, D.-M. Chen,
C.-R. Wang, C.-L. Bai, Y.-G. Wang, Adv. Funct. Mater. 2003, 13,
626 – 630; c) R. Bai, M. Ouyang, Z.-Z. Li, L.-G. Yang, M.-M. Shi,
G. Wu, M. Wang, H.-Z. Chen, J. Mater. Chem. 2008, 18, 4318 –
4323.
[9] For C60 whiskers: a) M. Sathish, K. Miyazawa, T. Sasaki, Chem.
Mater. 2007, 19, 2398 – 2400; b) J. Minato, K. Miyazawa, Carbon
2005, 43, 2837 – 2841; c) K. Miyazawa, Y. Kuwasaki, A. Obaya-
shi, K. Kuwabara, J. Mater. Res. 2002, 17, 83 – 88.
[10] For C60 tubes: a) H. B. Liu, Y. L. Li, L. Jiang, H. Y. Luo, S. Q.
Xiao, H. J. Fang, H. M. Li, D. B. Zhu, D. P. Yu, J. Xu, B. Xiang, J.
Am. Chem. Soc. 2002, 124, 13370 – 13371; b) K. Miyazawa, J.
Minato, T. Yoshii, M. Fujino, T. Suga, J. Mater. Res. 2005, 20,
688 – 695.
Experimental Section
C60 (purity 99%) and toluene (anhydrous) were purchased from
Aldrich and Wako and used as received. The detailed synthesis of the
porphyrin polymer is described in the Supporting Information.
The typical procedure for the synthesis of C60 microspheres is
briefly described as follows: 20 mL C60 stock solution (1 mgmLÀ1 in
toluene) was mixed with 10 mL Por stock solution (1 mgmLÀ1 in
toluene) and diluted with 10 mL toluene in a 1 mL vial; 20 mL of this
blend solution was transferred to a Si wafer (10 mm ꢀ 10 mm) and
slowly evaporated in a glass petri dish (diameter 95, height 20 mm)
under 500 mL toluene; the Si wafer had been simply rinsed with
acetone and dried in air before use.
Received: September 5, 2009
Published online: October 28, 2009
[11] For C60 sheets: a) M. Sathish, K. Miyazawa, J. Am. Chem. Soc.
2007, 129, 13816 – 13817; b) M. Sathish, K. Miyazawa, J. P. Hill,
K. Ariga, J. Am. Chem. Soc. 2009, 131, 6372 – 6373; c) H. S. Shin,
S. M. Yoon, Q. Tang, B. Chon, T. Joo, H. C. Choi, Angew. Chem.
2008, 120, 705 – 708; Angew. Chem. Int. Ed. 2008, 47, 693 – 696.
[12] For C60 spheres: A. Masuhara, Z. Tan, H. Kasai, H. Nakanishi,
H. Oikawa, Jpn. J. Appl. Phys. 2009, 48, 050206 – 050208.
[13] a) J.-M. Lehn, Science 2002, 295, 2400 – 2403; b) J. A. A. W.
Elemans, A. E. Rowan, R. J. M. Nolte, J. Mater. Chem. 2003, 13,
2661 – 2670; c) F. J. M. Hoeben, P. Jonkheijm, E. W. Meijer,
A. P. H. J. Schenning, Chem. Rev. 2005, 105, 1491 – 1546; d) K.
Sada, M. Takeuchi, N. Fujita, M. Numata, S. Shinkai, Chem. Soc.
Rev. 2007, 36, 415 – 435; e) K. Ariga, J. P. Hill , M. V. Lee, A.
Vinu, R. Charvet, S. Acharya, Sci. Technol. Adv. Mater. 2008, 9,
014109.
[14] a) S. Zhou, C. Burger, B. Chu, M. Sawamura, N. Nagahama, M.
Toganoh, U. E. Hackler, H. Isobe, E. Nakamura, Science 2001,
291, 1944 – 1947; b) N. Nakashima, T. Ishii, M. Shirakusa, T.
Nakanishi, H. Murakami, T. Sagara, Chem. Eur. J. 2001, 7, 1766 –
1772; c) V. Georgakilas, F. Pellarini, M. Prato, D. M. Guldi, M.
Melle-Franco, F. Zerbetto, Proc. Natl. Acad. Sci. USA 2002, 99,
5075 – 5080; d) N. Fujita, T. Yamashita, M. Asai, S. Shinkai,
Angew. Chem. 2005, 117, 1283 – 1287; Angew. Chem. Int. Ed.
2005, 44, 1257 – 1261; e) R. Charvet, D.-L. Jiang, T. Aida, Chem.
Commun. 2004, 2664 – 2665; f) D. M. Guldi, F. Zerbetto, V.
Georgakilas, M. Prato, Acc. Chem. Res. 2005, 38, 38 – 43; g) R.
Tsunashima, S. Noro, T. Akutagawa, T. Nakamura, H. Kawa-
kami, K. Toma, Chem. Eur. J. 2008, 14, 8169 – 8176.
Keywords: fullerenes · nanostructures · polymers ·
self-assembly · supramolecular chemistry
.
[1] a) H. W. Kroto, J. R. Heath, S. C. O’Brien, R. F. Curl, R. E.
Smalley, Nature 1985, 318, 162 – 163; b) A. Cravino, N. S.
Sariciftci, J. Mater. Chem. 2002, 12, 1931 – 1943; c) D. M. Guldi,
B. M. Illescas, C. M. Atienza, M. Wielopolski, N. Martin, Chem.
Soc. Rev. 2009, 38, 1587 – 1597.
[2] For solar cells: a) G. Yu, J. Gao, J. C. Hummelen, F. Wudl, A. J.
Heeger, Science 1995, 270, 1789 – 1791; b) J. Y. Kim, K. Lee,
N. E. Coates, D. Moses, T.-Q. Nguyen, M. Dante, A. J. Heeger,
Science 2007, 317, 222 – 225; c) G. Li, V. Shrotriya, J. Huang, Y.
Yao, T. Moriarty, K. Emery, Y. Yang, Nat. Mater. 2005, 4, 864 –
868; d) B. C. Thompson, J. M. J. Frechet, Angew. Chem. 2008,
120, 62 – 82; Angew. Chem. Int. Ed. 2008, 47, 58 – 77.
[3] For transistors: a) C. D. Dimitrakopoulos, P. R. Malenfant, Adv.
Mater. 2002, 14, 99 – 117; b) K. Itaka, M. Yamashiro, J. Yama-
guchi, M. Haemori, S. Yaginuma, Y. Matsumoto, M. Kondo, H.
Koinuma, Adv. Mater. 2006, 18, 1713 – 1716; c) A. L. Briseno,
S. C. B. Mannsfeld, M. M. Ling, S. Liu, R. J. Tseng, C. Reese,
M. E. Roberts, Y. Yang, F. Wudl, Z. Bao, Nature 2006, 444, 913 –
917; d) C. Yang, S. Cho, A. J. Heeger, F. Wudl, Angew. Chem.
2009, 121, 1620 – 1623; Angew. Chem. Int. Ed. 2009, 48, 1592 –
1595.
[4] For OLEDs: a) Y. Y. Yuan, S. Han, D. Grozea, Z. H. Lu, Appl.
Phys. Lett. 2006, 88, 093503; b) F. D’Souza, E. Maligaspe, M. E.
9650 www.angewandte.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2009, 48, 9646 –9651

Angewandte
Chemie
[15] a) T. Nakanishi, W. Schmitt, T. Michinobu, D. Kurth, K. Ariga,
Chem. Commun. 2005, 5982 – 5984; b) T. Nakanishi, K. Ariga, T.
Michinobu, K. Yoshida, H. Takahashi, T. Teranishi, H. Mohwald,
D. G. Kurth, Small 2007, 3, 2019 – 2023; c) T. Nakanishi, T.
Michinobu, K. Yoshida, N. Shirahata, K. Ariga, H. Moehwald,
D. G. Kurth, Adv. Mater. 2008, 20, 443 – 446; d) Y. Shen, J. Wang,
U. Kuhlmann, P. Hildebrandt, K. Ariga, H. Mꢂhwald, D. G.
Kurth, T. Nakanishi, Chem. Eur. J. 2009, 15, 2763 – 2767; e) J.
Wang, Y. Shen, S. Kessel, P. Ferandes, K. Yoshida, S. Yagai, D. G.
Kurth, H. Mꢂhwald, T. Nakanishi, Angew. Chem. 2009, 121,
2200 – 2204; Angew. Chem. Int. Ed. 2009, 48, 2166 – 2170; f) T.
Nakanishi, N. Miyashita, T. Michinobu, Y. Wakayama, T.
Tsuruoka, K. Ariga, D. Kurth, J. Am. Chem. Soc. 2006, 128,
6328 – 6329.
[16] a) M. H. Nurmawati, P. K. Ajikumar, R. Renu, C. H. Sow, S.
Valiyaveettil, ACS Nano 2008, 2, 1429 – 1436; b) M. H. Nurma-
wati, P. K. Ajikumar, L. A. Heng, H. R. Li, S. Valiyaveettil,
Chem. Commun. 2008, 4945 – 4947.
[17] M. Takeuchi, C. Fujikoshi, Y. Kubo, K. Kaneko, S. Shinkai,
Angew. Chem. 2006, 118, 5620 – 5625; Angew. Chem. Int. Ed.
2006, 45, 5494 – 5499.
D. M. Guldi, A. Palkar, L. Echegoyen, J. P. C. Tomꢃ, M. A.
Fazio, D. I. Schuster, Chem. Eur. J. 2005, 11, 3375 – 3388.
[19] H. Kuzmany, R. Pfeiffer, M. Hulman, C. Kramberger, Philos.
Trans. R. Soc. London Ser. A 2004, 362, 2375 – 2406.
[20] a) R. L. Penn, J. F. Banfield, Science 1998, 281, 969 – 971; b) R. L.
Penn, J. F. Banfield, Geochim. Cosmochim. Acta 1999, 63, 1549 –
1557; c) J. F. Banfield, S. A. Welch, H. Zhang, T. T. Ebert, R. L.
Penn, Science 2000, 289, 751 – 754; d) M. Niederberger, H.
Cꢂlfen, Phys. Chem. Chem. Phys. 2006, 8, 3271 – 3287.
[21] To confirm the supramolecular interactions between the por-
phyrin polymer and C60, we investigated the photophysical
change of the Por–C60 blend in toluene. Upon addition of C60,
small red-shift of the Soret band (up to 2 nm) in the absorption
spectra of porphyrin was observed, while the porphyrin fluores-
cence was significantly quenched (Figure S13 in the Supporting
Information). These photophysical changes resemble those
generally observed in porphyrin–fullerene host–guest systems,
supporting the existence of intermolecular interactions, most
likely p–p and van der Waals interactions, and efficient electron
transfer between the porphyrin-polymer donor and the C60
acceptor.[18c]
[18] a) M. Ayabe, A. Ikeda, Y. Kubo, M. Takeuchi, S. Shinkai, Angew.
Chem. 2002, 114, 2914 – 2916; Angew. Chem. Int. Ed. 2002, 41,
2790 – 2792; b) H. Nobukuni, Y. Shimazaki, F. Tani, Y. Naruta,
Angew. Chem. 2007, 119, 9133 – 9136; Angew. Chem. Int. Ed.
2007, 46, 8975 – 8978; c) P. D. W. Boyd, C. A. Reed, Acc. Chem.
Res. 2005, 38, 235 – 242; d) K. Tashiro, T. Aida, Chem. Soc. Rev.
2007, 36, 189 – 197; For porphyrin/C60-based devices: e) T.
Hasobe, H. Imahori, P. V. Kamat, T. K. Ahn, S. K. Kim, D.
Kim, A. Fujimoto, T. Hirakawa, S. Fukuzumi, J. Am. Chem. Soc.
2005, 127, 1216 – 1228; f) H. Imahori, T. Umeyama, J. Phys.
Chem. C 2009, 113, 9029 – 9039; g) S. A. Vail, P. J. Krawczuk,
[22] a) S. Mann, D. D. Archibald, J. M. Didymus, T. Douglas, B. R.
Heywood, F. C. Meldrum, N. J. Reeves, Science 1993, 261, 1286 –
1292; b) A.-W. Xu, Y. Ma, H. Cꢂlfen, J. Mater. Chem. 2007, 17,
415 – 449.
[23] Another explanantion for the minor amount of Por in the
microspheres is the partial use of Por in making composites with
C60. Most likely, Por suppresses the crystal growth of a certain
axis of C60, although the detailed role of Por is still not clear for
us at this stage.
[24] Y. Ma, G. M. Mehltretter, C. Plug, N. Rademacher, M. U.
Schmidt, H. Cꢂlfen, Adv. Funct. Mater. 2009, 19, 2095 – 2101.
Angew. Chem. Int. Ed. 2009, 48, 9646 –9651
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
9651