Optical properties of nematic liquid crystals doped with gold nanorods
Composites consisting of nematic liquid crystal (5-CB) and gold nanorods have been elaborated and investigated with a polarizing microscope. It was detected that the nanorods form inside the oriented liquid crystal matrix their own self-assembling well-ordered structures. Nanorods ordered structu...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2010
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| Назва видання: | Semiconductor Physics Quantum Electronics & Optoelectronics |
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| Цитувати: | Optical properties of nematic liquid crystals doped with gold nanorods / S. Torgova, E. Pozhidaev, A. Lobanov, M. Minchenko, B. Khlebtsov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 2. — С. 158-160. — Бібліогр.: 9 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
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irk-123456789-1182152017-05-30T03:04:03Z Optical properties of nematic liquid crystals doped with gold nanorods Torgova, S. Pozhidaev, E. Lobanov, A. Minchenko, M. Khlebtsov, B. Composites consisting of nematic liquid crystal (5-CB) and gold nanorods have been elaborated and investigated with a polarizing microscope. It was detected that the nanorods form inside the oriented liquid crystal matrix their own self-assembling well-ordered structures. Nanorods ordered structures appear as a result of aligning layers action and provides defects corresponding to the spatial distortion of the nematic liquid crystal director field. 2010 Article Optical properties of nematic liquid crystals doped with gold nanorods / S. Torgova, E. Pozhidaev, A. Lobanov, M. Minchenko, B. Khlebtsov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 2. — С. 158-160. — Бібліогр.: 9 назв. — англ. 1560-8034 PACS 61.30.Jf, 61.46.Km, 78.67.Bf, 89.75.Fb http://dspace.nbuv.gov.ua/handle/123456789/118215 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
| description |
Composites consisting of nematic liquid crystal (5-CB) and gold nanorods
have been elaborated and investigated with a polarizing microscope. It was detected that
the nanorods form inside the oriented liquid crystal matrix their own self-assembling
well-ordered structures. Nanorods ordered structures appear as a result of aligning layers
action and provides defects corresponding to the spatial distortion of the nematic liquid
crystal director field. |
| format |
Article |
| author |
Torgova, S. Pozhidaev, E. Lobanov, A. Minchenko, M. Khlebtsov, B. |
| spellingShingle |
Torgova, S. Pozhidaev, E. Lobanov, A. Minchenko, M. Khlebtsov, B. Optical properties of nematic liquid crystals doped with gold nanorods Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Torgova, S. Pozhidaev, E. Lobanov, A. Minchenko, M. Khlebtsov, B. |
| author_sort |
Torgova, S. |
| title |
Optical properties of nematic liquid crystals doped with gold nanorods |
| title_short |
Optical properties of nematic liquid crystals doped with gold nanorods |
| title_full |
Optical properties of nematic liquid crystals doped with gold nanorods |
| title_fullStr |
Optical properties of nematic liquid crystals doped with gold nanorods |
| title_full_unstemmed |
Optical properties of nematic liquid crystals doped with gold nanorods |
| title_sort |
optical properties of nematic liquid crystals doped with gold nanorods |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2010 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/118215 |
| citation_txt |
Optical properties of nematic liquid crystals doped
with gold nanorods / S. Torgova, E. Pozhidaev, A. Lobanov, M. Minchenko, B. Khlebtsov // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2010. — Т. 13, № 2. — С. 158-160. — Бібліогр.: 9 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
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2025-07-08T13:34:14Z |
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| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 158-160.
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
158
PACS 61.30.Jf, 61.46.Km, 78.67.Bf, 89.75.Fb
Optical properties of nematic liquid crystals doped
with gold nanorods
S. Torgova1, E. Pozhidaev1, A. Lobanov1, M. Minchenko1 and B. Khlebtsov2
1P.N. Lebedev Physical Institute, Russian Academy of Sciences,
Leninskii prospect, 53, Moscow 119991, Russia;
2Institute of Biochemistry and Physiology of Plants and Microorganisms,
Russian Academy of Sciences, prospect Entuziastov, 13, Saratov 410049, Russia;
Phone: +7 (499) 13264591, +7 (499) 13261161;
E-mail: sofia.torgova@mail.ru1; epozhidaev@mail.ru1; lobanov@sci.lebedev.ru1; mminchenko@mail.ru1;
khlebtsov@ibppm.sgu.ru2
Abstract. Composites consisting of nematic liquid crystal (5-CB) and gold nanorods
have been elaborated and investigated with a polarizing microscope. It was detected that
the nanorods form inside the oriented liquid crystal matrix their own self-assembling
well-ordered structures. Nanorods ordered structures appear as a result of aligning layers
action and provides defects corresponding to the spatial distortion of the nematic liquid
crystal director field.
Keywords: liquid crystal, gold nanorod, self-assembling structures.
Manuscript received 18.12.09; accepted for publication 25.03.10; published online 30.04.10.
1. Introduction
A new direction in studying the nanoparticles is related
with their insertion to a liquid crystal matrix as a new
non-synthetic method for modification of properties
inherent to existing liquid crystals. Today it is a top of
scientific interest, and a huge amount of papers are
aimed at this subject. Here, we mention just some of
them, where investigated nanoparticles are carbon
nanotubes, metallic spheres and ferroelectric
nanoparticles [1-7]. In this paper, new results concerning
the introduction of gold nanorods into nematic liquid-
crystal matrixes are reported.
2. Experiment
In our experiments, we used hydrosols of gold nanorods
that were synthesized according to the methods
presented in [8, 9]. The nanorods possess the shape of
hemispherical ended cylinders. Average nanoparticle
sizes were as follows: length about 70-100 nm and
thickness about 15-20 nm. The concentration of particles
in hydrosols was not less than 1011 ml-1. There were used
nanorods with surfactant CTAB (Cetyl trimethyl
ammonium bromide) dispersed in water.
The gold nanorods were inserted into liquid-crystal
(LC) matrixes in very small amount (0.02 vol.%).
In order to obtain the composites based on gold
nanorods and nematic LC, the latter was dissolved in
ethanol, after this, water suspension of nanoparticles
covered by surfactant was added, and then the solvents
were removed in vacuum. The obtained nanocomposites
(NC) were treated by ultrasound before the insertion into
the cell. The optical properties of NC were observed by
a polarization microscope. The results obtained are
shown in Figs 1 to 3.
3. Results and discussion
We investigated an influence of the insertion of very
small percentage of gold nanorods into LC matrix. We
observed that gold nanorods form inside the ordered
structure of liquid crystal different self-assembling well-
ordered structures (defects) corresponding to spatial
distortion of the LC director field. The size of these
defects is much larger than that of the particles
themselves and varies from few to hundred micrometers.
It is necessary to underline that the size, shape,
orientation and ordering of the defects depend on many
reasons, namely: the technology of cell surface
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 158-160.
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
159
treatment, the thickness of NC layer, the cell filling
conditions, the nature of LC matrix. The most interesting
result is presented in Fig. 1. It has been shown that
orientation of the LC principal optical axis (LC director)
and long axis of the self-assembling ordered nanorod
structures are matched together. On the other hand, the
LC director and the principal optical axis of defects
never match together, which can be explained by the
difference between surface tensions of LC and of gold
nanorods covered by surfactant: the surfactant surface
tension is considerably less than that of liquid crystals.
The appearance of some defects caused by insertion of
nanoparticles into LC matrix under permanent electric
field was mentioned in [6].
The most ordered defects were observed in the cells
treated for planar alignment, where the LC layer
thickness is 1.8 μm. Asymmetric boundary conditions
were used for manufacturing the cells. In this approach,
only one indium tin oxide (ITO) surface of LC cells was
covered with the polyimide (PMDA-ODA) possessing
the structure of repeated pyromellitic dianhydriden
(PMDA) and 4,4'-oxidianiline (ODA) units, while
another one was simply washed in N, N-dimethyl
formamide (DMF) and covered with 1.8 m calibrated
spacers.
The concentration of nanorods in nanocomposite is
0.02 %, and insertion of NC in the cell was done at the
temperature higher than transition of LC from the
nematic to isotropic phase. Under these conditions, the
defects have elongated stick-like shape, forming well-
ordered regular planar structures, which are
perpendicular to the LC director (see Fig. 1).
It is possible to understand the importance of the
boundary conditions influence on formation of defects
and their ordering by comparison of Figs 1, 2 and 3.
There is no any preferable direction of the principal
optical axis of planar defects in a cell without any
aligning layers (Fig. 2), while the liquid crystal itself is
aligned homeotropically.
Fig. 1. Microphoto of the NC layer in the cell with the
thickness 1.8 µm treated for planar alignment of the liquid
crystal. The cell was filled using the capillary method at the
temperature higher than the clearing point. The photo was done
between crossed polarizers at room temperature. The size is
500×400 µm.
Fig. 2. Microphoto of the NC droplet squeezed between two
glasses without any aligning layers, made with crossed
polarizers at room temperature. The size is 500×400 µm.
The same NC inserted into the homeotropically
aligned cell under the same conditions shows a
completely different result – homeotropic alignment of
both LC and defects (see Fig. 3).
The possible explanation of the defects formation is
as follows: filling the cell by using the capillary method
leads to planar orientation of nanorods and the main part
of NLC matrix. Surfactant of the nanorod anchors with
the aligning layer of the cell. This surfactant locally
orients the NLC matrix perpendicular to the surface of
nanorod during the transition from isotropic liquid to
nematic phase. This local orientation is schematically
shown in Fig. 4. This hypothesis is in a good agreement
with the experimental data.
The clearing point of the defects in NC is at least 2-
3 degrees higher than the clearing point of 5-CB itself
(35 °C). In Fig. 5, we present the photos of the cooling
process from the isotropic phase.
Fig. 3. Microphoto of NC, LC in the cell with the liquid crystal
layer thickness 1.8 µm treated for homeotropic alignment by
chromolane. The cell was filled using the capillary method at
the temperature higher than the clearing point. Photo was done
between crossed polarizers at room temperature.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2010. V. 13, N 2. P. 158-160.
© 2010, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
160
Fig. 4. Schematic explanation of the defect formation.
Fig. 5. Microphoto of NC cooling from the isotropic phase.
As seen from Fig. 5, appearance of the defects
precedes to the formation of the matrix nematic phase.
The position and size of defects in NC do not
change, after the heating till the clearing point of 5-CB
and cooling run from the isotropic phase. We succeeded
to “cancel” the self-assembling clusters only at
temperatures higher than 75 °C. Probably, it
demonstrates that the anchoring of the nanorod
surfactant with the aligning layer of the cell is
sufficiently more strong that the liquid crystal
themselves, but it needs further investigations.
4. Conclusions
In this work, nanocomposites consisting of nematic
liquid crystals (NLC) and gold nanorods have been
obtained. We observed that gold nanorods form inside
the oriented liquid crystal matrix different self-
assembling well-ordered structures (defects) correspond-
ding to spatial distortion of the NLC director field.
The size, shape, alignment and ordering of the
defects depend on many reasons and are very sensitive
to any change of the experimental conditions.
The NLC director alignment (coincident with the
main optical axis) and the long axis of self-assembling
well-ordered structures never match together (in the
main cases there are perpendicular to each other), which
can be explained due to the difference between the
surface tension of LC and of the gold nanorods covered
by surfactant, if taking into account the long-range order
interaction inside this system.
Acknowledgements
The work was supported by Russian Foundation of Basic
Researches, grant N 08-02-01074a.
References
1. Y. Shiraishi, K. Maeda, H. Yoshikawa, J. Xu,
N. Toshima and S. Kobayashi // Appl. Phys. Lett.
1(15), p. 2845 (2002).
2. Y. Reznikov, O. Buchnev, O. Tereshchenko,
V. Reshetnyak, A. Glushchenko and J. West //
Appl. Phys. Lett. 82(12), p. 1917 (2003).
3. S. Kobayashi, T. Miyama, N. Nishida, Y. Sakai,
H. Shiraki, Y. Shiraishi and N. Toshima // J. Disp.
Technol. 2, p. 121 (2006).
4. S. Kundu, M. Akimoto, I. Hirayama, M. Jnoue,
S. Kobayashi and K. Takatoh // Jpn. J. Appl. Phys.
47, p. 4751 (2008).
5. L. Scolari, S. Gauza, H. Xianyu, L. Zhai,
L. Eskildsen, T.T. Alkeskjold, S.T. Wu and
A. Bjarklev // Opt. Express 17, p. 3754 (2009).
6. S.I. Trashkeev, G.N. Grachev and G.A. Posdnjakov
// Zhurnal Tekhnich. Fiziki 77(9), p. 85 (2007), in
Russian.
7. H. Qi, B. Kinkead and T. Hegmann // Adv. Funct.
Mater. 18(2), p. 212-221 (2008).
8. H. Liao and J.H. Hafner // Chem. Mater. 17,
p. 4636 (2005).
9. B. Nikoobakht and M.A. E1-Stayed // Chem.
Mater. 15, p. 1957 (2003).
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