Helical silica nanotubes: Nanofabrication architecture, transfer of helix and chirality to silica nanotubes

Article abstract of DOI:10.2478/s11696-011-0083-5

A series of neutral gelators and cationic amphiphiles derived from 1,2 diphenylethylenediamine (I ) and 1,2-cyclohexanediamine (II ) was synthesised. Helical silica nanotubes were prepared utilising these organic gelators through sol-gel polycondensation of tetraethoxy silane, (TEOS-silica source). Right- and left-handed helical nanotubes respectively were obtained from a 1 : 1 mass mixture of optically active, (1S,2S)-III-(1S,2S)-V neutral gelator and (1S,2S)-IV-(1S,2S)-VI cationic amphiphile and a 1 : 1 mass mixture of optically active, (1R,2R)-III-(1R,2R)-V neutral gelator and (1R,2R)- IV-(1R,2R)-VI cationic amphiphile, indicating that the handedness of the helical nanotubes varied with the change in the neutral gelator precursors used. The nanotubes were characterised by SEM images.

Full text of DOI:10.2478/s11696-011-0083-5

Chemical Papers 65 (6) 863–872 (2011)
DOI: 10.2478/s11696-011-0083-5
ORIGINAL PAPER
Helical silica nanotubes: Nanofabrication architecture,
transfer of helix and chirality to silica nanotubes
a
a,bTae Kyu Kim, Euh Duck Jeong, a,bChae Young Oh, a,bMin Seob Shin,
b
b
aJong-Pil Kim, Ok-Sang Jung, Hongsuk Suh, a,cFazlur Rahman Nawaz Khan*,
bMyung Ho Hyun*, Jong Sung Jin*
a
aDivision of High Technology Materials Research, Busan Centre, Korea Basic Science Institute (KBSI),
Busan 618-230, Republic of Korea
bDepartment of Chemistry and Chemistry Institute for Functional Materials, Pusan National University,
Busan 609-735, Republic of Korea
cOrganic Chemistry Division, School of Advanced Sciences, VIT-University, Vellore 632 014, Tamil Nadu, India
Received 21 May 2011; Revised 12 July 2011; Accepted 16 July 2011
A series of neutral gelators and cationic amphiphiles derived from 1,2 diphenylethylenediamine (I )
and 1,2-cyclohexanediamine (II ) was synthesised. Helical silica nanotubes were prepared utilising
these organic gelators through sol–gel polycondensation of tetraethoxy silane, (TEOS–silica source).
Right- and left-handed helical nanotubes respectively were obtained from a 1 : 1 mass mixture of op-
tically active, (1S,2S)-III–(1S,2S)-V neutral gelator and (1S,2S)-IV–(1S,2S)-VI cationic amphiphile
and a 1 : 1 mass mixture of optically active, (1R,2R)-III–(1R,2R)-V neutral gelator and (1R,2R)-
IV–(1R,2R)-VI cationic amphiphile, indicating that the handedness of the helical nanotubes varied
with the change in the neutral gelator precursors used. The nanotubes were characterised by SEM
images.
c
ꢀ 2011 Institute of Chemistry, Slovak Academy of Sciences
Keywords: organogels, silica nanomaterials, chirality, handedness, crossover experiments
Introduction
sibility of the delivery of proteins into living cells
and their functions within the cell. These nanotube–
protein drug delivery systems have led to significant
advances in different fields of medicine (Cho et al.,
2010).
Chiral organic–inorganic hybrid 4,4-biphenylene–
silica nanotubes were prepared using a pair of chi-
ral anionic enantiomers (Wang et al., 2010). Silica
nanotubes have been prepared by using hard tem-
plates, such as anodic alumina membranes, polycar-
bonate membranes (Bian et al., 2009; Yang et al.,
2003; Liang & Susha, 2004), and soft organic tem-
plates such as surfactants (Yu et al., 2008; Kleitz
et al., 2001;. Delclos et al., 2008; Kim et al., 1998;
Yang et al., 1997; Asefa et al., 1995; Huo et al.,
Silica nanostructure materials have received much
attraction recently due to their potential applica-
tions in many fields such as catalysis or chiral catal-
ysis in organic synthesis (Sayari, 1996), chiral ad-
sorbent in chromatographic separation (Bruzzoniti
et al., 2000), and in the controlled release of drugs
(Zhu et al., 2005). Silica–titania nanorods–nanotubes
composite membranes with multi-functional proper-
ties such as photo-catalysis and membrane property
have been innovative in water purification, i.e. removal
of sodium dodecylbenzene sulphonate (SDBS) from
water (Zhang et al., 2006). Using silica–titania nan-
otubes, researchers have also demonstrated the pos-
*Corresponding author, e-mail: nawaz f@yahoo.co.in, mhhyun@pusan.ac.kr, jsjin@kbsi.re.kr

864
T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
1994; Stupp & Braun, 1997; Tanev & Pinnavaia, 1996;
Tanev et al., 1997), polymers (Mecerreyes et al., 2001;
Zhao et al., 1998), sugar-related (Yoza et al., 1999)
and amine-based (Jung et al., 2000b) gelators, etc.
It is well known that the chirality transfer can be
made from high-molecular mass compounds to low-
molecular mass compounds through non-covalent in-
teractions and that single-handed helical silica nan-
otubes have been prepared by using the self-assemblies
of optically active organic gelators or surfactants as
templates including sugar-integrated gelators (Yoza
et al., 1999), cholesterol-based gelators (Jung et al.,
2003, 2001; Piepenbrock et al., 2010; Qiao et al., 2009),
chiral surfactants, amino acid-based gelators (Yang et
al., 2006; Paik et al., 2010), or amino acid-based sur-
factants (Che et al., 2004; Qiu et al., 2008) derived
from optically active chiral compounds readily avail-
able from nature.
Chiral trans-1,2-cyclohexanediamine-derived gela-
tors have also been used for the preparation of
single-handed helical silica nanotubes (Jung et al.,
2000a, 2000b). Optically active amide or ureide deriva-
tives of trans-1,2-cyclohexanediamine were reported to
self-assemble into left-handed or right-handed helical
organogels and were transcribed into left- or right-
handed helical silica nanotubes through the sol–gel
polycondensation of tetraethoxy silane (TEOS). In
transcribing the organogel structure into the silica
structure, it was noted that the cationic charge in
the gelators was indispensable in the sol–gel poly-
condensation of TEOS as a silica source, but that
the cationic gelators tended to lose the high gela-
tion ability. Consequently, a mixture of neutral and
cationic gelators of identical stereochemistry prepared
from trans-1,2-cyclohexanediamine was used to form
stable organogels. However, it was not clear how the
neutral and cationic gelators were integrated into the
organogels and their role in sol–gel polycondensation,
even though it was known that cationic charge was
necessary for the sol–gel transcription in order to ad-
sorb anionic silica particles onto the organogels.
We recently demonstrated that the neutral gela-
tor (with the shorter alkyl side-chain) determined the
shape of the organogel, and the cationic amphiphile
influenced the polymerisation of TEOS after cover-
ing the surface of the organogel originating from the
neutral gelator (Hyun et al., 2009). Continuing our
research interest in nanomaterials (Kim et al., 2011;
Roopan et al., 2010; Roopan & Nawaz Khan, 2010a,
2010b, 2011), this paper is concerned with nanofabri-
cation architecture, the transfer of helix and chirality
to silica nanotubes.
H
N
O
N
H
O
a
(1S,2S)-III, (1R,2R)-III, and ( )-III
NH2
b
NH2
H
N
O
O
N(CH3)3Br
N(CH3)3Br
(1S,2S)-(−)-I,
(1R,2R)-(+)-I, or
( )-I
N
H
(1S,2S)-IV, (1R,2R)-IV, and ( )-IV
O
H
N
N
a
O
H
NH2
NH2
(1S,2S)-V and (1R,2R)-V
b
H
O
N
N(CH3)3Br
N(CH3)3Br
(1S,2S)-(−)-II, or
(1R,2R)-(+)-II
N
H
O
(1S,2S)-VI and (1R,2R)-VI
Fig. 1. Synthesis of neutral organic gelators and cationic amphiphiles: a) lauroyl chloride, Et3N, CH2Cl2, r.t.; b) (i) 11-
bromoundecanoic acid, 2-ethoxy-1-ethoxycarbonyl-1,2-dihidroquinoline (EEDQ), trimethyl amine, r.t., (ii) trimethyl amine,
THF–ethanol (ϕr = 2 : 1), r.t., 4 days.

T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
Table 1. Characterisation data of prepared compounds
865
wi(calc.)/%
wi(found)/%
Yield
%
M.p.
◦C
Compound
Formula
Mr
C
H
N
(1S,2S)-III
C38H60N2O2
576.9
79.11
79.32
61.19
61.27
61.16
61.24
10.48
10.56
7.70
7.59
8.80
8.76
4.86
4.96
3.96
3.83
6.79
6.85
65.0 137.0–137.7
70.0 146.8–147.5
60.0 116.8–117.4
Bromine intermediate C36H54Br2N2O2 706.63
(1S,2S)-IV C42H72Br2N4O2 824.85
Table 2. Spectral data of prepared compounds
Compound
Spectral data
IR, ν˜/cm−1: 3316, 3062, 3032, 2920, 2850, 1642, 1535, 1455, 701
(1S,2S)-III
1H NMR (CDCl3), δ: 0.87 (t, J = 6.6 Hz, 6H), 1.24 (m, 32H), 1.59 (m, 4H), 2.18 (t, J = 7.2 Hz, 4H), 5.24
(dd, J = 4.8 Hz, J = 2.4 Hz, 2H), 6.81 (s, 2H), 7.09–7.20 (m, 10H)
13C NMR (CDCl3), δ: 14.26, 22.88, 26.01, 29.51, 29.54, 29.59, 29.73, 29.85, 32.12, 36.75, 59.72, 125.40,
127.70, 128.01, 128.77, 138.87, 174.81
Bromine
intermediate
IR, ν˜/cm−1: 3433, 3306, 3059, 2925, 2851, 1642, 1543, 1458, 1381, 1252, 701
1H NMR (CDCl3), δ: 1.26 (m, 20H), 1.41 (m, 4H), 1.58 (m, 4H), 1.89 (m, 4H), 2.17 (t, J = 7.2 Hz, 4H),
3.40 (t, J = 6.9 Hz, 4H), 5.24 (dd, J = 4.8 Hz, J = 2.4 Hz, 2H), 6.64 (s, 2H), 7.09–7.19 (m, 10H)
13C NMR (CDCl3), δ: 25.90, 28.40, 28.89, 29.10, 29.51, 29.55, 29.60, 29.61, 33.05, 34.27, 37.07, 59.59, 127.74,
128.00, 128.81, 139.10, 174.09
(1S,2S)-IV
IR, ν˜/cm−1: 3419, 3299, 3030, 2924, 2853, 2074, 1641, 1541, 1490, 701
1H NMR (CD3CN), δ: 1.08–1.43 (m, 28H), 1.71 (m, 4H), 2.21 (t, J = 6.3 Hz, 4H), 3.04 (s, 18H), 3.24–3.30
(m, 4H), 5.37 (d, J = 8.7 Hz, 2H), 7.22 (t, J = 5.1 Hz, 2H), 7.31 (t, J = 5.4 Hz, 4H), 7.54 (d, J = 7.2 Hz,
2H), 8.98 (d, J = 10.2 Hz, 2H)
13C NMR (CD3CN), δ: 23.93, 27.04, 27.35, 30.14, 30.19, 30.37, 30.41, 30.43, 37.22, 53.52, 53.57, 59.06, 67.87,
128.39, 128.58, 129.27, 140,80, 175.91
Experimental
reached. Then the reaction mixture was diluted with
dichloromethane, washed first with 1 M HCl solu-
tion to remove un-reacted amine (triethylamine) im-
purity, then by using 1 M NaOH solution to remove
any excess acid impurity. The organic layer was then
washed thoroughly with water and dried using anhy-
drous sodium sulphate. Next, the solvent was removed
by distillation to yield the crude neutral gelator. The
pure neutral gelator was obtained as a white solid by
re-crystallisation from the mixture of dichloromethane
and hexane.
The silica nanomaterials were characterised using
the conventional X-ray diffractometer (XRD, Rigaku
D-2400, Rigaku, Japan). The scanning electron mi-
croscope (SEM) images of samples were recorded on
a Hitachi S-4200 (Hitachi, Japan), a field emission
SEM. The transmission electron microscope (TEM)
images were collected using a Jeol JEM 2010 micro-
scope (Jeol, Japan) at 200 kV.
The neutral organic gelators and cationic am-
phiphile required in the present studies were synthe-
sised as per the scheme depicted below (Fig. 1) and
were characterised by different analytical techniques
(Tables 1 and 2).
The other neutral gelators required in the inves-
tigations, namely (1R,2R)-III and ( )-III were pre-
pared following the same procedure and were charac-
terised by NMR, IR, and elemental analysis.
Neutral gelator, (1S,2S)-III: to a mixture of (1S,
2S)-(–)-diphenylethylenediamine (0.20 g, 0.94 mmol),
dichloromethane (5 mL) and triethylamine (0.53 mL,
3.80 mmol) stirred in a 50 mL round bottom flask,
dodecanoyl chloride (lauroyl chloride) (0.49 mL, 2.07
mmol) was slowly added through a dropping fun-
nel and continued to be stirred at room tempera-
ture until the completion of the reaction, which was
monitored by thin layer chromatography (TLC), was
Cationic amphiphile, (1S,2S)-IV: to a mixture of
11-bromoundecanoic acid (3.0 g, 11.32 mmol) and
2-ethoxy-1-ethoxycarbonyl-1,2-dihidroquinoline,
(EEDQ) (3.1 g, 12.54 mmol) stirred in a 250 mL round
bottom flask, (1S,2S)-(–)-diphenylethylenediamine
(1.0 g, 4.71 mmol) was slowly added through a drop-
ping funnel and continued to be stirred at room tem-
perature until the completion of the reaction, which
was monitored by thin layer chromatography (TLC),

866
T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
Fig. 2. Synthesis of right- and left-handed helical silica nanotubes.
was reached. Then the reaction mixture was diluted
with dichloromethane, washed first with 1 M HCl solu-
tion to remove un-reacted amine impurity, then by us-
ing 1 M NaOH solution to remove any excess acid im-
purity. The organic layer was washed thoroughly with
water, dried using anhydrous sodium sulphate, and
the solvent removed by distillation to yield the crude
halide intermediate. The pure intermediate was then
re-crystallised from the mixture of dichloromethane
and hexane as a pale yellow solid.
A
B
To the mixture of the halide intermediate (1.0 g,
1.42 mmol) in THF–ethanol (ϕr = 2 : 1) (24 mL) in a
50 mL round bottom flask, trimethyl amine (12 mL,
129.12 mmol) was added and the mixture stirred at
room temperature for 4 days. The completion of the
reaction was monitored by thin layer chromatography
(TLC). The organic solvent was removed under re-
duced pressure to yield the crude cationic amphiphile.
The pure cationic amphiphile was then re-crystallised
from the mixture of methanol and diethyl ether as a
white solid.
C
The other cationic amphiphiles required in the
investigations, namely, (1R,2R)-IV and ( )-IV were
prepared following the same procedure and were
characterised by NMR, IR, and elemental analy-
sis. The other neutral gelators (1S,2S)-V, (1R,2R)-
V and cationic amphiphiles (1S,2S)-IV and (1R,2R)-
IV based on 1,2-cyclohexanediamine, required in the
present study, were prepared following the reported
procedure (Jung et al., 2000a, 2000b).
The sol–gel polycondensation of tetraethoxy silane,
(TEOS), in the presence of benzyl amine and water
under the influence of the organogel template, was
adopted for the synthesis of helical silica nanotubes
as depicted in the figure below (Fig. 2). A mixture of
1 : 1 neutral and cationic amphiphile (2 mg each) was
added to ethanol (100 µL) in a 2 mL vial and heated
until dissolved and allowed to form an organogel at
room temperature. To the organogel, TEOS (16 µL),
benzyl amine (10 µL), and water (10 µL) were added
and heated until a transparent solution was obtained
and then allowed to rest for seven days. Then, the mix-
ture was heated under argon atmosphere initially up
Fig. 3. SEM images of the organogels obtained in ethanol from
(1S,2S)-III (A), (1S,2S)-IV (B), and mixture (1 : 1) of
(1S,2S)-III and (1S,2S)-IV (C).
to 200◦C within 3 h at a heating rate of 1◦C min−1
,
maintained at 200◦C for 2 h, then further increased
to 500◦C at a heating rate of 1.7◦C min−1 within 3 h
and maintained at 500◦C for 3 h. Finally, the reac-
tion mixture was cooled to 25◦C and then reheated
under aerobic conditions initially up to 200◦C, main-
tained at that temperature for 2 h and then increased
to 500◦C and maintained at 500◦C for 3 h to yield the
silica nanotubes. The formation processes of the silica
nanotubes were elucidated by monitoring the shape
and size of the structures with scanning electron mi-
croscopy (SEM) and transmission electron microscopy
(TEM). The SEM and TEM images were recorded
before calcinations and after calcinations; the images
were found to be similar.

T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
867
Results and discussion
The gel formations of the neutral gelators and
cationic amphiphiles (Fig. 3) were investigated using
various organic solvents. The morphology of different
gels was also investigated using crossover experiments
and by recording the SEM and TEM images. The neu-
tral or cationic gelators (2 mg each) or 1 : 1 mixture of
neutral gelators and cationic amphiphiles (2 mg each)
were added to 100 µL of each of ethanol, acetoni-
trile, and butan-1-ol solvents; however, they were all
only soluble upon heating. It was observed that when
the neutral gelator solution was left at room tempera-
ture for 10 min the gelation was completed. However,
the cationic amphiphiles failed to form the organogel,
whereas the 1 : 1 mass mixture of neutral gelators and
cationic amphiphiles formed the organogel. In order
to understand the morphology of the gels, SEM im-
ages of the gels were recorded, i.e. a piece of organogel
was placed on a carbon-coated copper grid and re-
moved after 1 min, leaving some small patches of the
Fig. 4. SEM image of a helical silica product before calcination.
gel on the grid. Then they were dried under vacuum
and analysed by SEM. For example, the SEM images
A
B
Fig. 5. SEM (A) and TEM (B) images of the right-handed helical silica nanotubes obtained from the 1 : 1 mass mixture of
(1S,2S)-III and (1S,2S)-IV (after calcination).
B
A
100 nm
Fig. 6. SEM (A) and TEM (B) images of the left-handed helical silica nanotubes obtained from the 1 : 1 mass mixture of (1S,2S)-III
and (1S,2S)-IV (after calcination).

868
T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
A
B
200 nm
Fig. 7. SEM (A) and TEM (B) images of the non-helical silica tubes obtained from the 1 : 1 mass mixture of ( )-III and ( )-IV
(after calcination).
A
B
C
Fig. 8. SEM images of right-handed helical silica nanotubes obtained from the 1 : 1 mixture of (1S,2S)-III and (1S,2S)-IV (A),
(1R,2R)-IV (B), or ( )-IV (C) (after calcination).
of the organogels formed from (1S,2S)-III, (1S,2S)-IV
and the 1 : 1 mass mixture of (1S,2S)-III and (1S,2S)-
IV in ethanol were investigated. The neutral gelator,
(1S,2S)-III, produced slightly helical-type organogel,
but the cationic amphiphile, (1S,2S)-IV, formed a vis-
cous fluid, with no regular morphology. By contrast,
the 1 : 1 mass mixture of (1S,2S)-III and (1S,2S)-IV
produced right-handed helical organogel with a diam-
eter of few nanometers, (Fig. 3).
The chiral silica nanotubes were obtained by

T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
869
A
B
C
Fig. 9. SEM images of left-handed helical silica nanotubes obtained from the 1 : 1 mixture of (1R,2R)-III and (1R,2R)-IV (A),
(1S,2S)-IV (B), or ( )-IV (C) (after calcination).
the sol–gel polycondensation of tetraethoxy silane,
(TEOS), in the presence of benzyl amine and water
under the influence of organogel templates, by heating
the whole mixture and then cooling it to room temper-
ature for seven days. The SEM images of the resulting
silica materials were recorded to explore the chirality
and thickness of the helical silica materials (Fig. 4).
The helical silica materials obtained were calcinated to
prepare helical silica nanotubes. The SEM and TEM
images of the silica nanotubes obtained after the cal-
cinations (Figs. 5–7) were examined for their chiral
structure. Interestingly, it was observed that when a 1
: 1 mixture of neutral gelator (1S,2S)-III and cationic
amphiphile (1S,2S)-IV was used, right-handed helical
silica nanotubes were obtained (see Fig. 5). Similarly,
a 1 : 1 mixture of (1R,2R)-III and (1R,2R)-IV resulted
in left-handed helical silica nanotubes (Fig. 6); how-
ever, a 1 : 1 mixture of ( )-III and ( )-IV resulted in
non-helical silica tubes (Fig. 7) and the calibre of the
tube was generally larger (from 600 nm to 2 µm) than
the helical silica nanotubes (50–70 nm).
In order to understand and establish the optimum
conditions for the synthesis of chiral nanotubes, a
crossover experiment to explain the role of neutral or-
ganic gelators and cation amphiphiles was performed.
At the start of the crossover experiment, the neu-
tral gelator (1S,2S)-III was constant the cationic am-
phiphiles varied from (1S,2S)-IV, (1R,2R)-IV, and
( )-IV and the silica nanotubes were obtained from 1
: 1 mixture of neutral gelator and cationic amphiphile.
The handedness of the helical silica nanotubes ob-
tained is presented in the figures; when (1S,2S)-III was
used as a neutral gelator, in every case the morphol-
ogy of the silica nanotubes was a right-handed helical
structure (Fig. 8). Similarly, when the neutral gelator
(1R,2R)-III was constant and the cationic amphiphiles
varied, the resulting silica nanotubes were of a left-
handed helical structure, (Fig. 9). However, when the
racemic neutral gelator ( )-III was used instead, the
resulting silica tubes were non-helical (Fig. 10). From

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T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
A
B
C
Fig. 10. SEM images of non-helical silica nanotubes obtained from the 1 : 1 mixture of ( )-III and (1S,2S)-IV (A), (1R,2R)-IV
(B), or ( )-IV (C) (after calcination).
these observations it may be assumed that it was not
the cationic amphiphile but the absolute configura-
tion of the neutral gelator that played a major role in
determining the chirality of the silica nanotube. Sim-
ilar observations, identical to the earlier report, were
made in the crossover experiments performed using a
1 : 1 mixture of neutral V and cationic VI gelators de-
rived from 1,2-cyclohexanediamine (Fig. 11) i.e. the
right-handed helical silica nanotubes were obtained
using organogel formed from the mixture of (1S,2S)-
V and (1S,2S)-VI whereas the left-handed helical sil-
ica nanotubes were formed from the 1 : 1 mixture of
(1R,2R)-V and (1R,2R)-VI. However, a comparison
of the SEM images of silica nanotubes obtained using
gelators derived from 1,2-cyclohexanediamine and 1,2-
diphenylethylenediamine revealed that a higher pu-
rity and yield of helical silica nanotubes were only
obtained in the case of gelators derived from 1,2-
diphenylethylenediamine, due to the inter-molecular
interactions between the two phenyl groups which re-
sulted in the effective hydrophobic interaction essen-
tial to the self-assembly gelation process. It was also
established that the 1 : 1 mixture of neutral gelator
and cationic amphiphile played an essential role in the
handedness of helical silica nanotubes. We may con-
clude from these results that the handedness of helical
silica nanotubes is controlled solely by the stereochem-
istry of the neutral gelator and is independent of the
stereochemistry of the cationic amphiphile.
Conclusion
Silica nanotubes were prepared through the sol-
gel polycondensation of TEOS, using organogels as
templates. When 1 : 1 mass mixtures of optically
active or racemic neutral gelator and cationic am-
phiphile prepared from 1,2-diphenylethylenediamine
or 1,2-diaminocyclohexane were used as templates, the
resulting silica nanotubes were found to show single-
handed helicity or non-helicity according to the stere-
ochemistry of the neutral gelators used, irrespective of
the stereochemistry of the cationic amphiphiles. From

T. K. Kim et al./Chemical Papers 65 (6) 863–872 (2011)
871
A
B
D
C
Fig. 11. SEM images of the right- and left-handed helical silica nanotubes obtained from the 1 : 1 mixture of (1S,2S)-V and
(1S,2S)-VI (A) or (1R,2R)-VI (B) and from the 1 : 1 mixture of (1R,2R)-V and (1S,2S)-VI (C) or (1R,2R)-VI (D) (after
calcination).
these results, it may be concluded that the neutral
gelators play an important role in determining the
handedness of helical silica nanotubes according to
their stereochemistry.
ing lipidic self-assemblies. Nano Letters, 8, 1929–1935. DOI:
10.1021/nl080664n.
Huo, Q., Margolese, D. I., Ciesla, U., Feng, P., Gier, T.
E., Sieger, P., Leon, R., Petroff, P. M., Schu¨th, F., &
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Hyun, M.-H., Shin, M.-S., Kim, T.-K., Jung, O.-S., Kim, J.-P.,
Jeong, E.-D., & Jin, J. S. (2009). The role of the neutral and
cationic gelators from (1S,2S)-(–)-diphenylethylenediamine
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Acknowledgements. Support for this work came from the
fund from the Korea Basic Science Institute (KBSI) (No.
K3108A) for Dr. J. S. Jin and Dr. J. P. Kim and in part from
the fund from the NCRC programme of NRF/MEST, Korea
(grant number: 2011-0006-254) for Prof. M. H. Hyun.
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