From bola-amphiphiles to supra-amphiphiles: The transformation from two-dimensional nanosheets into one-dimensional nanofibers with tunable-packing fashion of n-type chromophores

Article abstract of DOI:10.1002/chem.201200898

With a rational design of the supra-amphiphiles, we have successfully demonstrated that not only the dimension of the self-assembled nanostructures, but also the packing fashion of the functional naphthalene diimide (a typical n-type chromophore), can be tuned in a noncovalent way in aqueous solution. Naphthalene diimide is incorporated into a bola-amphiphile as the rigid core, whereas viologen derivatives are used as the hydrophilic head. The bola-amphiphile self-assembles into two-dimensional nanosheets, in which naphthalene diimide adopts a "J-type" aggregation. Water-soluble supramolecular complexation between viologen derivatives and the 8-hydroxypyrene-1, 3, 6-trisulfonic acid trisodium salt is used as a driving force for the formation of the supra-amphiphiles. Upon formation of the supra-amphiphiles, the nanosheets transform into ultralong nanofibers with a close packing of naphthalene diimide. Notably, just by mixing the two building blocks of the supra-amphiphiles in aqueous solution, a dimension-controlled evolution of the nanostructures is formed that leads to a different packing fashion of the n-type functional chromophores, which is facile and environmental friendly. Copyright

Full text of DOI:10.1002/chem.201200898

DOI: 10.1002/chem.201200898
From Bola-amphiphiles to Supra-amphiphiles: The Transformation from
Two-Dimensional Nanosheets into One-Dimensional Nanofibers with
Tunable-Packing Fashion of n-Type Chromophores
[
a]
[a]
[a]
[b]
[b]
[a]
Kai Liu, Yuxing Yao, Chao Wang, Yu Liu, Zhibo Li, and Xi Zhang*
8622
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Chem. Eur. J. 2012, 18, 8622 – 8628

FULL PAPER
Abstract: With a rational design of the
supra-amphiphiles, we have successful-
ly demonstrated that not only the di-
mension of the self-assembled nano-
structures, but also the packing fashion
two-dimensional nanosheets, in which
naphthalene diimide adopts a “J-type”
tion of the supra-amphiphiles. Upon
formation of the supra-amphiphiles,
the nanosheets transform into ultralong
nanofibers with a close packing of
AHCTUNGTRENNUNG
aggregation. Water-soluble supramolec-
ular complexation between viologen
derivatives and the 8-hydroxypyrene-1,
3, 6-trisulfonic acid trisodium salt is
used as a driving force for the forma-
naphthalene di ACHUTNGRENNUGi mide. Notably, just by
of the functional naphthalene di
a typical n-type chromophore), can be
tuned in a noncovalent way in aqueous
solution. Naphthalene diimide is incor-
A
H
U
G
R
N
U
G
mixing the two building blocks of the
supra-amphiphiles in aqueous solution,
a dimension-controlled evolution of the
nanostructures is formed that leads to
a different packing fashion of the n-
type functional chromophores, which is
facile and environmental friendly.
(
AHCTUNGTRENNUNG
Keywords: charge-transfer interac-
tion · nanostructures · n-type chro-
porated into a bola-amphiphile as the
rigid core, whereas viologen derivatives
are used as the hydrophilic head. The
bola-amphiphile self-assembles into
mophores
· supra-amphiphiles ·
supramolecular chemistry
Introduction
the time-consuming chemical syntheses can be avoided to
some extent. In addition, with elaborate tuning the chemical
structures of the building blocks, supra-amphiphiles can be
The rational design and fabrication of dimension-controlled
nanostructures containing organic functional p chromo-
phores is very important for future nanoelectronics. On
one hand, the most fascinating features of p-conjugated ma-
terials are their variable optical and electronic properties
[7]
engineered to fabricate well-defined nanostructures. More-
over, stimuli-responsive functional moieties can be easily in-
corporated into supra-amphiphiles, thus leading to the con-
[
1]
[8]
trolled self-assemblies and disassemblies. The formation of
supra-amphiphiles can be regarded as a first-order self-as-
sembly, and by further second-order self-assembly, supra-
amphiphiles can be utilized as building blocks for the con-
struction of highly-ordered assemblies. The advance of
supra-amphiphiles will not only enrich the family of conven-
tional amphiphiles that are formed on the basis of covalent
bonds, but will also provide a new avenue between the col-
loidal and supramolecular sciences.
[2]
when forming aggregates in organic or aqueous solution.
A different packing fashion of aromatic molecules may lead
[3]
to completely different functions. On the other hand, the
dimension of nanostructures containing functional chromo-
phores is very crucial for the dimension-controlled transpor-
tation of energies or charge carriers, which is significant for
[4]
the microminiaturization of optoelectronic devices. Vari-
ous nanostructures containing functional chromophores
have been fabricated in organic media, but rarely in aqueous
solution. In addition, the studies on the organization be-
haviors of n-type organic chromophores largely lag behind
its p-type counterparts. Thus, it still remains a challenge for
rational control over the dimension of the nanostructures
with a tunable-packing fashion of the organic semiconduc-
tors, especially the n-type ones, in water.
Herein, with a rational design of the supra-amphiphiles,
we have realized a simultaneous control over the packing
[5]
fashion of naphthalene di
sembled architectures in water. The nanosheets, in which
naphthalene diimide is “J-aggregated”, transform into ultra-
long nanofibers with a close packing of naphthalene diimide
ACHTUNGTRNENUNGi mide and the dimension of self-as-
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
upon the formation of supra-amphiphiles. It should be noted
that, just by mixing the two building blocks of the supra-am-
phiphile in water has led to a big change in the nanostruc-
tures as well as the packing fashion of n-type organic chro-
mophores, which is facile and environmental friendly. We
believe such strategy is promising for the design of function-
al materials with different optical and electronic properties,
thus enriching the supramolecular engineering of functional
nanomaterials.
Supra-amphiphiles refer to amphiphiles that are formed
on the basis of noncovalent interactions, which may include
p–p interactions, hydrogen bonding, charge-transfer interac-
[6]
tions, and electrostatic interactions.
Supra-amphiphiles
with various architectures can be fabricated by either small
organic molecules or polymers. One advantage of supra-am-
phiphiles is their noncovalent-synthesized nature, by which
[
a] K. Liu, Y. Yao, C. Wang, Prof. X. Zhang
Key Lab of Organic Optoelectronics & Molecular Engineering
Department of Chemistry, Tsinghua University
Beijing 100084 (P.R. China)
Results and Discussion
Fax : (+86)10-6277-1149
E-mail: xi@mail.tsinghua.edu.cn
Naphthalene di
porated into
ACHTUNGTRENNUNG
a
[
b] Y. Liu, Prof. Z. Li
Scheme 1) as the rigid core, whereas viologen derivatives
are used as hydrophilic head. Water-soluble supramolecular
complexation between viologen derivatives and the 8-hy-
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201200898.
[9]
droxypyrene-1, 3, 6-trisulfonic acid trisodium salt (PYR) is
Chem. Eur. J. 2012, 18, 8622 – 8628
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8623

X. Zhang et al.
ure 1b) and AFM (Figure 1c).
The section analysis of Fig-
ure 1c indicates that the thick-
ness of the nanosheets is about
3
.6 nm. XRD experiments also
indicate that there exist layered
structures with a thickness of
about 3.9 nm (Figure 1d). It
should be noted that the ex-
tended length of the molecule
is about 4.9 nm (estimated by
Chem3D). The fact that the
thickness of the nanosheets is
shorter than the extended mo-
lecular length suggests that the
BNDIV may adopt a tilted con-
formation in the nanosheets.
To gain further insight into
the packing fashion of naphtha-
lene di ACHTUNGRNENUGi mide in the nanosheets,
Scheme 1. Schematic representation of the formation of the supra-amphiphiles and the controlled evolution of
the nanostructures as well as the packing fashion of the naphthalene diimide.
AHCTUNGTRENNUNG
we have employed UV/Vis and
fluorescence spectroscopy to
used as a driving force for the formation of the supra-am-
phiphiles. It has been reported by our group that the cooper-
ativity of Coulombic attractions, charge-transfer interactions,
and the hydrophobic effect are responsible for the formation
of the “viologen derivative–PYR” supramolecular com-
plex. It is anticipated that the formation of the supra-am-
phiphiles will not only lead to an dimension-controlled evo-
lution of nanostructures, but also lead to a change of the
provide more information. In methanol, the BNDIV shows
a typical monomer absorption and fluorescence emission
[10]
(Figure 2), indicating a monomeric state.
from methanol to water, the main absorption band of naph-
thalene diimide are redshifted by 8 nm with a decrease of
the intensity (Figure 2a). This is characteristic of “J-type”
aggregation of naphthalene diimide chromophores in solu-
tion, in which the naphthalene diimide may adopt a tilted
and slipped “head-to-tail” conformation with respect to
When going
[8a]
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
packing fashion of naphthalene di
A
H
U
G
R
N
U
G
ACHTUNGTRENNUNG
supramolecular engineering of functional nanomaterials.
As a typical bola-amphiphile, BNDIV itself self-assembles
in water to form two-dimensional nanosheets, as revealed by
TEM (Figure 1a), which was confirmed by cryo-TEM (Fig-
[10]
each other. Moreover, upon assembly, the fluorescence in-
tensity of BNDIV is strongly increased (Figure 2b), as
a result of the high fluorescence quantum yield upon form-
ing the “J-aggregates” of naphthalene di
blies.
ACHTUNGTRENNUNiG mide in the assem-
To confirm that viologen moieties in BNDIV molecules
can form a charge-transfer complex with PYR, different
[7–9,11]
characterization methods were employed.
BNDIV and
PYR were mixed in pH 9 buffer at a 1:2 molar ratio. Firstly,
as shown in Figure 3a, the resulting solution exhibits
a green color, which is characteristic for the charge-transfer
complex of viologen derivative with PYR. Secondly, it can
be imagined that, the 1:2 complexation of BNDIV and PYR
will turn the overall charge of the assemblies from positive
to negative. In zeta potential measurement, BNDIV assem-
blies exhibit a potential of 16 mV, which should be attribut-
ed to the positively charged viologen derivative head-group.
In contrast, upon complexation with PYR, the zeta potential
of the assemblies changed to ꢀ31 mV, thus confirming the
formation of the supra-amphiphiles. Thirdly, a new and
broad charge-transfer band appears between 540 and
7
00 nm after complexation, confirming the formation of
charge-transfer complex (Figure 3b). Fourth, the fluores-
cence of PYR is strongly quenched upon complexation with
BNDIV (Figure 3c), which is caused by the charge-transfer
interaction. Moreover, the complex formed by BNDIV and
Figure 1. a) TEM, b) cryo-TEM, c) tapping mode AFM images (inset:
height profile along the blue line) and d) XRD scan of the BNDIV as-
semblies in buffer solution (pH 9).
8624
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Tunable-Packing Fashion of n-Type Chromophores
FULL PAPER
4
+
6ꢀ
charge-transfer complex of BNDIV
/
A
H
U
G
E
N
N
(PYR)
(see the
2
Supporting Information, Figure S1). All these data indicate
that BNDIV and PYR can form supramolecular complex
with a 1:2 stoichiometry because of the charge-transfer inter-
action between viologen derivatives with PYR, which is re-
sponsible for the formation of the supra-amphiphiles.
Interestingly, upon formation of the supra-amphiphiles,
the two-dimensional nanosheets transform into one-dimen-
sional nanofibers, as indicated by TEM (Figure 4a) and con-
firmed by cryo-TEM (Figure 4b). There is no clear contrast
between the edge and the central part, thus indicating that
the one-dimensional structures are solid nanofibers. It
should be noted that the nanofibers have a high length/di-
ameter ratio. As shown in Figure 4c, the nanofibers are
quite uniform with a diameter of 4.7 nm. Moreover, their
length reaches several micrometers. The formation of nano-
fibers is also supported by AFM images (see the Supporting
Information, Figure S2), and the diameter of the nanofibers
is about 4.2 nm as indicated by Figure S2b in the Supporting
Information. It should be pointed out that the diameter of
the nanofibers measured by AFM is lower than that ob-
tained in cryo-TEM, which should be attributed to compres-
sion effect by the AFM tip. The angular dependent scatter-
ing intensities were obtained using static light-scattering
Figure 2. a) UV/Vis absorption and b) fluorescence spectra of BNDIV in
methanol and water. The concentration of BNDIV is fixed at 5.0ꢁ10 m.
ꢀ
4
(
SLS) measurements, as shown in Figure 4d, which allowed
us to characterize the nanostructures in situ. Typically, for
cylindrical one-dimensional nanostructures, the scattering in-
ꢀ
1
tensity, I, follows a q power law, in which q represents the
[12]
scattering vectors, q=4psinq/l.
As shown in Figure 4d,
the napierian logarithm of I shows a linear dependence on
2
Figure 3. a) Photographs of the BNDIV, PYR, and BNDIV/ ACHTGNUTRNEUN(G PYR) com-
plex solutions showing their colours. b) UV/Vis absorption and c) fluores-
cence emission. d) Time-resolved fluorescence spectra of the BNDIV,
PYR, and BNDIV/
2
ACHTUNGTRENNUNG( PYR) complex solutions (BNDIV: black, PYR: red,
ꢀ
4
complex: blue). The concentration of BNDIV is 5.0ꢁ10 and PYR is
ꢀ
3
1
.0ꢁ10 m, respectively.
PYR was studied by time-resolved fluorescence analysis. As
shown in Figure 3d, the lifetime of the PYR emission is
shortened after the complexation with BNDIV. It should be
noted that the exciplex of charge-transfer complex is non-
ACHTUNGTRENNUNGe missive, since no new emission peak has been observed in
the BNDIV–PYR complex compared with that of PYR.
Thus, the decreased emission lifetime should be ascribed to
charge-transfer process. This result confirms the formation
of charge-transfer complex of BNDIV and PYR. In addi-
tion, mass spectroscopy supports the formation of charge-
transfer complex between BNDIV and PYR. A strong peak
at m/z=898.49 is observed, which should correspond to the
Figure 4. a) TEM and b) cryo-TEM images of the BNDIV/
blies in buffer solution (pH 9). c) Statistical analysis of the width of the
BNDIV/(PYR) nanofibers. d) The vector-dependent scattering intensi-
ties of the BNDIV/(PYR) assemblies. The concentration of PYR is 1.0ꢁ
10 and 5.0ꢁ10 m for BNDIV.
2
ACHTUNGTNERNUNG( PYR) assem-
A
H
U
G
R
N
U
G
2
A
H
U
G
R
N
U
G
2
ꢀ
3
ꢀ4
Chem. Eur. J. 2012, 18, 8622 – 8628
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X. Zhang et al.
the napierian logarithm of q. The slope was measured to be
1.01, which is consistent with the value predicted for one-
lene di AHCTUNGTRENNUNiG mide is decreased after the formation of the supra-
ꢀ
amphiphiles. Hypochromism, that is, the decrease in the ex-
tinction coefficient of chromophores, can be widely ob-
served in dye aggregates. It has been well studied that hypo-
chromism of chromophores is strongly dependent on r, the
dimensional nanostructures (ꢀ1.0). Generally, the fabrica-
tion of one-dimensional nanostructures relies on highly di-
[13]
rectional intermolecular interactions. Thus, the strong and
highly directional charge-transfer interactions between the
viologen head of BNDIV and PYR (Scheme 1) is attributed
as the main driving force to transform the two-dimensional
nanosheets into one-dimensional nanofibers.
3
distance between chromophores by a function of 1/r : the
[15–16]
shorter of the distance, the more of the hypochromism.
The hypochromism of naphthalene diimide indicates
imide in the nano-
AHCTUNGTRENNUNG
a closed packing state of naphthalene di
fibers.
ACHTUNGTRENNUNG
As PYR is pH-responsive, we wondered if the nanofibers
formed by the supra-amphiphiles have the same responsive-
ness. It is interesting to find that, the straight nanofibers in
pH 9 buffer as shown in Figure 4a become curled in pH 8
buffer (see the Supporting Information, Figure S3). Howev-
er, the diameter and length of the nanofibers at pH 8 are
the same with that in pH 9, indicating the molecular ar-
rangement in the nanofibers remain unchanged. The “non-
covalent-synthesized” nature of the supra-amphiphiles is ad-
vantageous in that the pH-responsive functional moiety,
PYR, can be incorporated into the supra-amphiphiles just
by simply mixing with the other building block in water,
thus avoiding the time-consuming covalent organic synthe-
ses. It is a facile and efficient way to fabricate pH-responsive
one-dimensional nanofibers.
With all these data in mind, the transformation mecha-
nism is proposed as follows: the BNDIV molecules self-as-
semble into “J-aggregates”, in which the naphthalene di-
AHCTUNGTRENNUNGi mide may adopt a tilted and slipped conformation with re-
spect to each other, as shown in Scheme 1. However, the
strong and highly directional charge-transfer interaction of
viologen derivatives with PYR in the head-group of the
supra-amphiphiles facilitates the growth of the assembly
along one dimension, finally leading to the formation of
nanofibers, in which the naphthalene di ACHUTNGRNENGUi mide group in the
middle part of the supra-amphiphiles may adopt a rotated
and close-packing fashion. In addition, the increase of pH
value of the solution can lead to an increased ionization
extent of the hydroxy group on PYR. As a result, the
charge-repulsion force on the surface of the nanofibers in-
creases accordingly, leading to the transformation of curled
nanofibers into straight ones.
We envisage that the dramatic changes of the nanostruc-
tures upon the formation of the supra-amphiphile will lead
to a different packing fashion of naphthalene di ACHUTNRGNENUGi mide in the
assemblies. Different characterization methods were used to
provide evidence. First, as shown in Figure 5a, the circular
dichroism (CD) is quite different after the formation of the
supra-amphiphiles, indicating a different packing arrange-
Conclusion
[14]
ment of naphthalene di
state of naphthalene diimide is suggested by the UV/Vis ab-
sorption, as shown in Figure 5b. The absorbance of naphtha-
A
H
U
G
R
N
N
imide.
Second, the close-packing
We have demonstrated the feasibility of using supra-amphi-
philes to fabricate dimension-controlled well-defined nano-
structures with a tunable-packing-fashioned naphthalene di-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
nanofibers formed by the supra-amphiphile exhibit a tunable
straightness upon the change of the pH value: the increase
of pH value of the solution can lead to an increased ioniza-
tion extent of the hydroxy group on PYR, leading to the
transformation of curled nanofibers into straight ones. The
close packing and one-dimensional arrangement of the n-
type semiconducting naphthalene di ACHUTNGRNENUGi mide in the nanofibers
is crucial for organic optoelectronic materials. Notably, just
by mixing the two building blocks of the supra-amphiphiles
in aqueous solution can lead to a dimension-controlled evo-
lution of the nanostructures as well as the packing fashion
of the functional chromophores, which is facile and environ-
mental friendly. We hope such a strategy can be extended to
the design of other functional materials with different opti-
cal and electronic properties.
Figure 5. a) CD and b) UV/Vis spectra of BNDIV and BNDIV/
A
H
U
G
R
N
N
2
ꢀ
3
ꢀ
4
1
0 m, respectively.
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Tunable-Packing Fashion of n-Type Chromophores
FULL PAPER
[
2] a) S. J. George, A. Ajayaghosh, Chem. Eur. J. 2005, 11, 3217–3227;
b) S. S. Babu, K. K. Kartha, A. Ajayaghosh, J. Phys. Chem. Lett.
2010, 1, 3413–3424; c) A. Ajayaghosh, S. J. George, J. Am. Chem.
Soc. 2001, 123, 5148–5149.
3] a) A. Ajayaghosh, C. Vijayakumar, R. Varghese, S. J. George,
Angew. Chem. 2006, 118, 470–474; Angew. Chem. Int. Ed. 2006, 45,
Experimental Section
1
General procedures: H NMR spectra were obtained by using a JOEL
JNM-ECA300 apparatus; ESI MS spectra were recorded using a PE
Sciex API 3000 apparatus. UV/Vis spectra were measured using a HITA-
CHI U-3010 spectrophotometer (path length is 10.0 mm for Figure 2b,
whereas 1.0 mm for Figure 4b); fluorescence spectra were measured
using a HITACHI F-7000 apparatus; CD spectra were obtained by using
Applied Photophysics-Pistar p-180 spectrophotometer.
[
4
56–460; b) C. Vijayakumar, V. K. Praveen, A. Ajayaghosh, Adv.
Mater. 2009, 21, 2059–2063; c) F. J. M. Hoeben, P. Jonkheijm, E. W.
Meijer, A. P. H. J. Schenning, Chem. Rev. 2005, 105, 1491–1546;
d) Z. J. Chen, A. Lohr, C. R. Saha-Moller, F. Wꢂrthner, Chem. Soc.
Rev. 2009, 38, 564–584; e) M. D. Watson, A. Fechtenkçtter, K.
Mꢂllen, Chem. Rev. 2001, 101, 1267–1300; f) B. Song, Z. Q. Wang,
S. L. Chen, X. Zhang, Y. Fu, M. Smet, W. Dehaen, Angew. Chem.
SLS measurements were carried out on a commercial LS spectrometer
ALV5000) equipped with a single avalanche photo diode detector and
(
a cylindrical 22 mW UNIPHASE He-Ne laser (l =632.8 nm). The LS
0
cell was held in a thermostat refractive index matching vat filled with pu-
rified and dust-free toluene.
2
005, 117, 4809–4813; Angew. Chem. Int. Ed. 2005, 44, 4731–4735;
g) R. Bhosale, J. Misek, N. Sakai, S. Matile, Chem. Soc. Rev. 2010,
9, 138–149; h) S. V. Bhosale, C. H. Jani, S. J. Langford, Chem. Soc.
TEM measurements were carried out on a JEMO 2010 electron micro-
scope operating at an acceleration voltage of 120 kV. The samples were
prepared by drop-casting the aqueous solution on the carbon-coated
copper grid and were then negatively stained with a phosphotungstic acid
solution. Cryo-TEM samples were prepared in a controlled environment
vitrification system (CEVS) at 288C. The vitrified samples were stored in
liquid nitrogen until they were transferred to a cryogenic sample holder
3
Rev. 2008, 37, 331–342; i) Y. W. Huang, Y. Yan, B. M. Smarsly, Z. X.
Wei, C. F. J. Faul, J. Mater. Chem. 2009, 19, 2356–2362; j) Y. Sagara,
T. Kato, Angew. Chem. 2008, 120, 5253–5256; Angew. Chem. Int.
Ed. 2008, 47, 5175–5178; k) Y. Kou, Y. H. Xu, Z. Q. Guo, D. L.
Jiang, Angew. Chem. 2011, 123, 8912–8916; Angew. Chem. Int. Ed.
2
011, 50, 8753–8757; l) M. Q. Xue, Y. Zhang, Y. L. Yang, T. B. Cao,
(
ꢀ
Gatan 626) and examined by a JEM2200FS TEM (200 kV) at about
1748C.
Adv. Mater. 2008, 20, 2145–2150.
[
4] a) E. W. Meijer, A. P. H. J. Schenning, Nature 2002, 419, 353–354;
b) S. Yagai, Y. Nakano, S. Seki, A. Asano, T. Okubo, T. Isoshima, T.
Karatsu, A. Kitamura, Y. Kikkawa, Angew. Chem. 2010, 122,
AFM was performed using tapping-mode in air on a commercial multi-
mode Nanoscope IVAFM. For sample preparation, a few drops of the so-
lution were placed on a mica surface and were incubated for 10 min
under moist conditions; excess solution was removed by absorption onto
filter paper, then the substrate was washed slightly with water and air-
dried.
1
0186–10190; Angew. Chem. Int. Ed. 2010, 49, 9990–9994; c) Y. H.
Xu, L. Chen, Z. Q. Guo, A. Nagai, D. L. Jiang, J. Am. Chem. Soc.
011, 133, 17622–17625; d) V. K. Praveen, S. J. George, R. Varghese,
C. Vijayakumar, A. Ajayaghosh, J. Am. Chem. Soc. 2006, 128, 7542–
550; e) S. S. Babu, V. K. Praveen, S. Prasanthkumar, A. Ajaya-
2
XRD measurements: For sample preparation, a few drops of the solution
were placed on a glass surface, and then the solvent was evaporated at
room temperature. The sample was then directly used for XRD measure-
ments. The Bragg peak q was extracted from the XRD data and the
layer thickness d could be obtained according to the Bragg equation
d ¼ l=2 sin q, in which l=0.15405 nm.
7
ghosh, Chem. Eur. J. 2008, 14, 9577–9584.
5] a) L. Zang, Y. Che, J. S. Moore, Acc. Chem. Res. 2008, 41, 1596–
[
1
608; b) W. Zhang, W. Jin, T. Fukushima, A. Saeki, S. Seki, T. Aida,
Science 2011, 334, 340–343; c) F. Wꢂrthner, T. E. Kaiser, C. R.
Saha-Mçller, Angew. Chem. 2011, 123, 3436–3473; Angew. Chem.
Int. Ed. 2011, 50, 3376–3410 and references therein; d) A. Ustinov,
H. Weissman, E. Shirman, I. Pinkas, X. B. Zuo, B. Rybtchinski, J.
Am. Chem. Soc. 2011, 133, 16201–16211; e) B. Rybtchinski, ACS
Nano 2011, 5, 6791–6818; f) E. Krieg, E. Shirman, H. Weissman, E.
Shimoni, S. G. Wolf, I. Pinkas, B. Rybtchinski, J. Am. Chem. Soc.
Zeta potential measurements were measured on Malvern ZS 90 Zetasizer
instrument.
Time-resolved fluorescence measurements were performed on a single-
photon-counting spectrofluorimeter from Edinburgh Analytical Instru-
ments (FLSP 920).
2
009, 131, 14365–14373; g) A. Ajayaghosh, P. Chithra, R. Varghese,
Angew. Chem. 2007, 119, 234–237; Angew. Chem. Int. Ed. 2007, 46,
30–233.
2
[
6] a) X. Zhang, C. Wang, Chem. Soc. Rev. 2011, 40, 94–101; b) C.
Wang, Z. Q. Wang, X. Zhang, Small 2011, 7, 1379–1383; c) C.
Wang, Z. Q. Wang, X. Zhang, Acc. Chem. Res. 2012, 45, 608–618.
7] a) C. Wang, S. C. Yin, S. L. Chen, H. P. Xu, Z. Q. Wang, X. Zhang,
Angew. Chem. 2008, 120, 9189–9192; Angew. Chem. Int. Ed. 2008,
Acknowledgements
This work was financially supported by the National Basic Research Pro-
gram (2007CB808000, 2011CB808200), the NSFC (50973051, 20974059),
NSFC-DFG joint grant (TRR 61), and the Program of Co-Construction
with the Beijing Municipal Commission of Education, as well as by the
[
4
7, 9049–9052; b) C. Wang, Y. S. Guo, Y. P. Wang, H. P. Xu, X.
Zhang, Chem. Commun. 2009, 5380–5382; c) K. Liu, C. Wang, Z.
Li, X. Zhang, Angew. Chem. 2011, 123, 5054–5058; Angew. Chem.
Int. Ed. 2011, 50, 4952–4956; d) K. V. Rao, K. Jayaramulu, T. Kumar
Maji, S. J. George, Angew. Chem. 2010, 122, 4314–4318; Angew.
Chem. Int. Ed. 2010, 49, 4218–4222.
Tsinghua
University
Initiative
Scientific
Research
Program
(
2009THZ02230). Thanks to Dr. Huaping Xu for his helpful discussion
and Dongdong Zhang and Dr. Juan Qiao for their help with the time-re-
soled fluorescence spectra measurement.
[
8] a) C. Wang, Y. S. Guo, Y. P. Wang, H. P. Xu, X. Zhang, Angew.
Chem. 2009, 121, 9124–9127; Angew. Chem. Int. Ed. 2009, 48, 8962–
[
1] a) S. S. Babu, S. Prasanthkumar, A. Ajayaghosh, Angew. Chem.
012, 124, 1800–1810; Angew. Chem. Int. Ed. 2012, 51, 1766–1776;
b) A. Ajayaghosh, V. K. Praveen, C. Vijayakumar, Chem. Soc. Rev.
008, 37, 109–122; c) A. Ajayaghosh, V. K. Praveen, Acc. Chem.
Res. 2007, 40, 644–656; d) P. Terech, R. G. Weiss, Chem. Rev. 1997,
8
965; b) C. Wang, Q. S. Chen, H. P. Xu, Z. Q. Wang, X. Zhang, Adv.
2
Mater. 2010, 22, 2553–2555; c) C. Wang, Q. S. Chen, Z. Q. Wang, X.
Zhang, Angew. Chem. 2010, 122, 8794–8797; Angew. Chem. Int. Ed.
2
2
010, 49, 8612–8615; d) C. Wang, G. Wang, Z. Q. Wang, X. Zhang,
9
7, 3133–3159; e) G. O. Lloyd, J. W. Steed, Nat. Chem. 2009, 1, 437–
Chem. Eur. J. 2011, 17, 3322–3325.
4
42; f) S. Prasanthkumar, A. Gopal, A. Ajayaghosh, J. Am. Chem.
[9] a) E. B. De Borba, C. L. C. Amaral, M. J. Politi, R. Villalobos, M. S.
Baptista, Langmuir 2000, 16, 5900–5907; b) P. P. Neelakandan, M.
Hariharan, D. Ramaiah, J. Am. Chem. Soc. 2006, 128, 11334–11335;
c) S. Gamsey, A. Miller, M. M. Olmstead, C. Beavers, L. C. Hiraya-
ma, S. Pradhan, R. A. Wessling, B. Singaram, J. Am. Chem. Soc.
2007, 129, 1278–1286.
Soc. 2010, 132, 13206–13207; g) A. Dawn, T. Shiraki, S. Haraguchi,
S.-i. Tamaru, S. Shinkai, Chem. Asian J. 2010, 5, 266–282; h) A. W.
Hains, Z. Liang, M. A. Woodhouse, B. A. Gregg, Chem. Rev. 2010,
1
10, 6689–6735; i) A. P. H. J. Schenning, E. W. Meijer, Chem.
Commun. 2005, 3245–3258.
Chem. Eur. J. 2012, 18, 8622 – 8628
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8627

X. Zhang et al.
[
10] a) H. Shao, J. Seifert, N. C. Romano, M. Gao, J. J. Helmus, C. P. Jar-
[12] B. Lonetti, A. Tsigkri, P. R. Lang, J. Stellbrink, L. Willner, J. Kohl-
brecher, M. P. Lettinga, Macromolecules 2011, 44, 3583–3593.
[13] a) L. Brunsveld, B. J. B. Folmer, E. W. Meijer, R. P. Sijbesma, Chem.
Rev. 2001, 101, 4071–4097; b) A. Jain, K. V. Rao, U. Mogera, A. A.
Sagade, S. J. George, Chem. Eur. J. 2011, 17, 12355–12361.
[14] J. Gawronski, M. Brzostowska, K. Kacprzak, H. Kołbon, P. Skowro-
nek, Chirality 2000, 12, 263–268.
[15] R. S. Lokey, B. L. Iverson, Nature 1995, 375, 303–305.
[16] R. C. Cantor, P. R. Schimmel, Biophysical Chemistry Part II, Free-
man, New York, 1980, pp. 390–408.
oniec, D. A. Modarelli, J. R. Parquette, Angew. Chem. 2010, 122,
7
854–7857; Angew. Chem. Int. Ed. 2010, 49, 7688–7691; b) M.
Kumar, S. J. George, Chem. Eur. J. 2011, 17, 11102–11106; c) B. A.
Jones, A. Facchetti, M. R. Wasielewski, T. J. Marks, Adv. Funct.
Mater. 2008, 18, 1329–1339; d) H. Shao, M. Gao, S. H. Kim, C. P.
Jaroniec, J. R. Parquette, Chem. Eur. J. 2011, 17, 12882–12885; e) H.
Shao, T. Nguyen, N. C. Romano, D. A. Modarelli, J. R. Parquette, J.
Am. Chem. Soc. 2009, 131, 16374–16376; f) J. Baram, E. Shirman,
N. Ben-Shitrit, A. Ustinov, H. Weissman, I. Pinkas, S. G. Wolf, B.
Rybtchinski, J. Am. Chem. Soc. 2008, 130, 14966–14967.
[
11] Y. L. Liu, Y. Yu, J. Gao, Z. Q. Wang, X. Zhang, Angew. Chem. 2010,
Received: March 16, 2012
1
22, 6726–6729; Angew. Chem. Int. Ed. 2010, 49, 6576–6579.
Published online: June 20, 2012
8628
www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 8622 – 8628