Nematic to smectic texture transformation in MBBA by in situ synthesis of silver nanoparticles

Article abstract of DOI:10.1039/b909428h

The present study describes the texture changes in 'nematic' N-(4-methoxybenzylidene)-4-butylaniline (MBBA) by in situ synthesis of silver nanoparticles in the system without any external reducing or stabilizing agents. Optical polarizing microscopy (OPM), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and scanning and transmission electron microscopy (SEM and TEM) were utilized to understand the mechanistic details of the texture transformation in MBBA. The experimental results collectively suggest that the silver nanoparticles are generated through the reduction of silver ions by MBBA upon heat treatment, followed by a clear texture transformation from 'nematic' to 'smectic'. The 'smectic' MBBA - Ag NP conjugate forms a stable luminescent glassy phase on rapid cooling, with an emission maximum of 500 nm upon photo-excitation at the silver plasmon absorption. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010.

Full text of DOI:10.1039/b909428h

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/njc | New Journal of Chemistry
Nematic to smectic texture transformation in MBBA by in situ synthesis
of silver nanoparticlesw
P. K. Sudhadevi Antharjanam* and Edamana Prasad*
Received (in Gainesville, FL, USA) 13th May 2009, Accepted 2nd December 2009
First published as an Advance Article on the web 29th January 2010
DOI: 10.1039/b909428h
The present study describes the texture changes in ‘nematic’ N-(4-methoxybenzylidene)-
4
-butylaniline (MBBA) by in situ synthesis of silver nanoparticles in the system without any
external reducing or stabilizing agents. Optical polarizing microscopy (OPM), differential scanning
calorimetry (DSC), nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared
(
FT-IR) spectroscopy, and scanning and transmission electron microscopy (SEM and TEM) were
utilized to understand the mechanistic details of the texture transformation in MBBA. The
experimental results collectively suggest that the silver nanoparticles are generated through
the reduction of silver ions by MBBA upon heat treatment, followed by a clear texture
transformation from ‘nematic’ to ‘smectic’. The ‘smectic’ MBBA–Ag NP conjugate forms
a stable luminescent glassy phase on rapid cooling, with an emission maximum of 500 nm
upon photo-excitation at the silver plasmon absorption.
Introduction
and stabilization of silver nanoparticles in thermotropic meso-
1
5
phases have been rarely reported. Barmatov and co-workers
describe the in situ synthesis of silver nanoparticles in a
polymer matrix and its effect on the clearing temperature, as
The formation of nanoparticles in a liquid crystal (LC) medium
has been recognized as a promising arsenal for materials chemists
1–8
to tune the properties of matter at the nano dimension.
16a
well as the mesophase temperature interval. It has been recently
reported that some of the mesogenic silver nanocomposites
Since liquid crystals possess order at the molecular (nano) level,
and the properties of nanoparticles are extremely dependant on
the perseverance of their uniform size/shape, generating and
incorporating nanoparticles into LC phases provides great
opportunities to design functional materials that have direct
applications in display systems, ferroelectric materials, and
16b
exhibit interesting conductivity properties.
Liquid crystal-
line capped silver–palladium bimetallic nanoparticles were
prepared and their electro-optical properties were studied by
16c
Toshima and co-workers. While in situ synthesis of silver
nanoparticles in the LC state results in many useful material
properties, to the best of our knowledge, texture transformation
in mesogenic systems induced by silver nanoparticles has not
been reported.
9,10
photonics.
Recent reports of the preparation of polymeric
nanostructures of fluorinated acrylates in a condensed smectic
phase and leaf-like gold nanostructures from imidazolium
lamellar LCs containing dicyanoaurate counter ions suggest that
nanoparticle formation in LC phases is a highly feasible
Herein, we describe, for the first time, the observation of
in situ nanoparticle-induced ‘nematic’ to ‘smectic’ texture trans-
formation in a room temperature liquid crystal, N-(4-methoxy-
benzylidene)-4-butylaniline (MBBA). The silver nanoparticles
were generated through the reduction of silver ions by MBBA
upon heat treatment, which induced a texture change for the
mesogenic material. Interestingly, the smectic phase of the
MBBA–Ag NP conjugate can be preserved in a glassy state
upon rapid cooling of the system from higher temperatures.
Most excitingly, photoluminescence was observed from
MBBA–Ag NP conjugate in the green region of the visible
spectrum upon excitation at 420 nm in the glassy phase.
The intensity of the emission was found to be proportional to
the amount of nanoparticle precursor used, suggesting that the
emission originated from the silver nanoparticles generated in
the LC phase.
11,12
process.
The elegant works of Lattermann and co-workers
have shown that copper nanoparticles with 3 nm diameter can be
synthesized by reducing copper(II) complexes in hexagonal
13
columnar poly(propyleneimine) dendrimer-based LCs. In situ
formation of gold nanoparticles embedded in glassy liquid
crystals of amine-containing cholesterols has also been
1
0
reported. The impact of nanoscale particles and carbon nano-
tubes in liquid crystal display systems has been recently high-
14
lighted by Qi and Hegmann.
While the use of lyotropic LC materials in the preparation
of silver nanoparticles has been extensively studied, the formation
Department of Chemistry, Indian Institute of Technology Madras
(IITM), Chennai, India 600 036.
E-mail: santharjanam@rediffmail.com, pre@iitm.ac.in;
Fax: +91 44-2257-4202; Tel: +91 44-2257-4232
w Electronic supplementary information (ESI) available: UV-Vis
spectra, SEM and TEM images, OPM pictures, and fluorescence
Results and discussions
3
spectra of MBBA–Ag NP conjugate at different mol% AgNO ,
Amines such as 4-aminophenol, 2-methyl aniline and oleyl
amine are known to reduce silver and gold ions in solution to
FT-IR spectra of MBBA–Ag NP conjugate, fluorescence spectra for
the control experiments described in the text. See DOI: 10.1039/
b909428h.
17
the corresponding nanoparticles. Amine-containing dendrimers,
4
20 | New J. Chem., 2010, 34, 420–425
This journal is ꢀc The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

View Article Online
such as poly(amidoamine) {PAMAM}, are also capable of
generating silver nanoparticles by the reduction of silver ions
through single electron transfer reduction from the large
1
8
number of amines present in the dendritic systems. Since
the reduction of silver ions by amines to nano-silver is
exothermic, heat treatment or UV irradiation of the reaction
mixture is generally required. Since MBBA contains an imine
nitrogen capable of donating electrons, we explored its ability
to reduce silver ions, forming silver nanoparticles in situ,
hoping that the LC arrangement will stabilize the generated
nanoparticles. For that, a homogeneous solution of MBBA
Fig. 2 SEM and TEM images of the MBBA–Ag NP conjugate (a and b,
3
respectively) prepared using 80 mol% AgNO . Scale bar for SEM and
(
0.15 mmol) and silver nitrate (1, 3, 5 and 80 mol%) in 5 mL
TEM are 500 mm and 500 nm, respectively.
methanol was drop-cast onto a glass slide and the solvent was
allowed to evaporate. After drying, the plate was heated to
isotropic temperature and kept at this point for 2 min. On
heating, the initially colorless film turned to light brown,
indicating the reduction of silver nitrate. Fig. 1 contains the
thin film absorption spectra of MBBA and the MBBA–
deposited on a glass substrate. It shows the diffraction peaks
at 2y = 38.1, 44.3, 64.5 and 77.41, corresponding to the
reflections of [111], [200], [220] and [113] planes for the cubic
˚
Ag phase. The lattice constant for the cubic cell was 4.08 A,
AgNO
3
mixture prepared using 5 mol% silver nitrate after
which is in good agreement with the reported data for pure
1
9
heat treatment. The UV-Vis absorption spectrum shows a
broad peak between 400–470 nm, corresponding to the silver
plasmon absorption.
silver. Crystallite sizes were calculated from the silver (111)
diffraction line using Scherrer’s equation: L = Kl/b cosy,
where L is the mean dimension of the crystallite, b is the full
width at half maximum intensity of the diffraction peak, y is
the diffraction angle, l is the wavelength of the Cu-Ka
radiation (0.1540 nm) and the K value is taken as 0.89. The
value obtained was 23 nm, which is lower than that of
the average size obtained from TEM images (50 nm). The
increased size obtained in TEM images could be due to
the presence of the capping organic moieties coordinated to
the nanoparticles (vide infra).
The silver plasmon absorption peak undergoes a slight
bathochromic shift upon increasing the concentration of
AgNO . The absorption spectra with different molar ratios
3
of MBBA and AgNO3 exhibited similar features, and the
spectra retained their shape for several days, indicating that
silver nanoparticles are not aggregating in the mesophase. The
formation of silver nanoparticles (Ag NPs) in MBBA host
systems was further confirmed by scanning electron micro-
scopy (SEM) and transmission electron microscopy (TEM).
The SEM image of the MBBA–Ag NP conjugate prepared
To understand the effect of the silver nanoparticles on the
LC behavior of MBBA, we studied the phase transitions of
MBBA–Ag NP conjugate films using an optical polarizing
microscope (OPM) and differential scanning calorimetry
(DSC). The mixtures containing 1, 3 and 5 mol% AgNO3
showed identical texture properties under OPM. While the
mesogen MBBA shows room temperature nematic texture,
with a clearing temperature of 35 1C, the texture was lost in
3
using 80 mol% AgNO is shown in Fig. 2a. The TEM image of
the corresponding system shows the presence of silver nano-
particles and nanorods with lower aspect ratio (Fig. 2b).
The size of the Ag nanoparticles in the TEM image was in
the range of 20–95 nm. SEM and TEM images for MBBA–Ag
NP conjugates prepared using various molar ratios of AgNO3
are given in the ESI (Fig. S3–S5).w
the presence of 1, 3 and 5 mol% AgNO . Fig. 4 shows charac-
3
Fig. 3 shows the X-ray diffraction (XRD) pattern of the
teristic optical polarizing microscopic pictures of an MBBA–
Ag NP conjugate prepared using 5 mol% AgNO3.
3
MBBA–Ag NP conjugate (MBBA + 80 mol% AgNO )
Fig. 1 UV-Visible thin film absorption spectra of (a) MBBA alone,
and (b) the MBBA–AgNO mixture prepared using 5 mol% AgNO
after heating to isotropic temperature and cooling.
3
3
,
Fig. 3 XRD pattern for silver nanoparticles generated in the MBBA
3
liquid crystalline domain. 80 mol% AgNO was used in this case.
This journal is ꢀc The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
New J. Chem., 2010, 34, 420–425 | 421

View Article Online
Fig. 4 Optical polarizing microscopic pictures (magnification 20Â) of an MBBA–Ag NP conjugate prepared using 5 mol% AgNO
3
: (a) before
heating at room temperature, (b) isotropic mixture at 70 1C, and (c) on cooling to room temperature. The nematic texture of MBBA is lost and the
final defect texture is retained in the film.
The phase separation is clearly visible before heating (a in
Fig. 4). Upon heating, the mixture isotropizes (b in Fig. 4) and
silver nanoparticles were generated. On cooling, no nematic
texture was observed for mixtures containing 1–5 mol%
3
AgNO . On the other hand, rectangular blocks were visible,
which were aligned in a random fashion (c in Fig. 4). On
re-heating, these rectangular blocks cleared to the isotropic
phase and re-appeared on cooling. This unique defect texture
was stable for several weeks. Interestingly, the LC property of
the MBBA–Ag NP conjugate prepared using 80 mol% silver
nitrate is entirely different from that of the other mixtures
(Fig. 5). On heating to isotropic temperatures and cooling,
baˆ tonnets structures were formed (Fig. 5c), which were then
converted to focal conic smectic A texture (Fig. 5d). On rapid
cooling, this mixture forms a stable glassy phase (Fig. 5e).
DSC studies were carried out to determine the phase
transition temperatures in the above cases. Fig. 6 shows
DSC thermograms obtained for MBBA and an MBBA–Ag
3
NP conjugate prepared using 5 and 80 mol% AgNO . The
MBBA–Ag NP conjugate showed higher transition temperatures
compared to MBBA alone. Higher melting temperatures
indicate the stabilization of the LC phase due to the presence
of nanoparticles. The enthalpy change (DH) involving at the
isotropization temperature also increases largely as the
Fig. 5 Optical polarizing microscopic pictures (magnification 20Â)
‘
nematic’ (less ordered) texture is changed to ‘smectic’ (highly
À1
of an MBBA–Ag NP conjugate prepared using 80 mol% AgNO :
3
ordered) [DH value for MBBA alone was 1.303 J g and
that for the MBBA–Ag NP conjugate (80 mol% AgNO ) was
(
a) before heating the mixture at room temperature, (b) isotropic phase
3
À1
of the mixture at 75 1C (c) Sm A batonnets structure at 73 1C in the
ˆ
3
2.32 J g ].
Since conventional reducing agents are not utilized for
cooling cycle, (d) focal conic Sm A texture at 70 1C in the cooling cycle
and (e) glassy phase.
reduction in the above systems, it is reasonable to assume that
MBBA itself acts as the reducing agent. Nuclear magnetic
resonance (NMR) experiments were performed for the MBBA–
Ag NP conjugate in CDCl3 to understand the structural
changes in MBBA in association with the reduction of silver
ions at different molar ratios. Fig. 7 shows the NMR spectra of
an MBBA–Ag NP conjugate prepared using 5 and 80 mol%
changed to 1 : 1 upon increasing the mole percentage of
3
AgNO to 80 mol% (Fig. 7b). Also, the ratio of the integration
values for the alkyl protons of 4-butylaniline and MBBA
increases in an identical manner. This clearly suggests that
the dissociation of MBBA is closely associated with the
AgNO
-methoxybenzaldehyde and 4-butylaniline, which are the
3
. The NMR spectra show the peaks correspond to
reduction of AgNO
3
.
4
Imine-based reduction of silver ions has recently been
2
0
hydrolyzed products of MBBA, in addition to the peaks of
un-dissociated MBBA. It was also noted that the percentage of
both 4-methoxybenzaldehyde and 4-butylaniline was found to
reported in the literature. It has also been reported that
MBBA can be hydrolyzed to 4-methoxybenzaldehyde and
4-butylaniline in the presence of moisture, and the vertical
alignment of 4-butylaniline results in lowering of the phase
3
increase as the amount of the nanoparticle precursor (AgNO )
2
1
was increased. For example, the integration values of the
benzaldehyde (–CHO) peak (d 9.9) and the MBBA imine
transition temperature of MBBA. In the present case, com-
plex formation of MBBA–Ag ions followed by reduction of
silver ions by the imine moieties present in MBBA would be
the initial steps, prior to the nucleophilic addition of water to
(
NP conjugate prepared using 5 mol% AgNO . The ratio was
CH–N) peak (d 8.4) exhibit a ratio of 1 : 5 for MBBA–Ag
3
4
22 | New J. Chem., 2010, 34, 420–425
This journal is ꢀc The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

View Article Online
conjugate (please see Fig. S11 and S12 in the ESIw). The
hydrolyzed products of MBBA were also strongly coordinated
in the MBBA–Ag NP conjugate, as indicated by the FT-IR
experimental results.
The MBBA–Ag NP conjugate can be obtained as a green
powder at room temperature which is highly stable for several
weeks. After two weeks, the green powder was examined under
OPM and the images are given in Fig. 8.
The MBBA–Ag NP conjugate exhibits interesting emission
properties upon photo-excitation at the silver plasmon absorp-
tion peak (420 nm) in the thin film. Fig. 9 contains the
excitation and luminescence spectra of MBBA–Ag NP con-
3
jugate prepared using 80 mol% AgNO . The spectrum was
taken after mixing and heat treating MBBA and AgNO in
3
required proportions. OPM analysis of these films was carried
out and the formation of the glassy state was confirmed prior
to the luminescence study. The emission maximum from the
system with various molar ratios of silver ion precursor was at
500 nm.
Fig. 6 DSC thermograms of (a) MBBA; MBBA–Ag NP conjugate
prepared using (b) 5 mol%, and (c) 80 mol% AgNO on heating cycle.
3
the imine bond which leads to the hydrolysis. The in situ
formed silver nanoparticles catalyze the hydrolysis, which is
evident from the fact that the extent of hydrolysis increases as
the concentration of silver nanoparticle precursor increases.
The mixture, which contains MBBA and its hydrolyzed
products associated with the Ag nanoparticles, exhibit a layer
ordered arrangement leading to the smectic texture. The
important role of silver nanoparticles in the texture trans-
formations is confirmed through control experiments, where
equivalent amounts of MBBA, 4-methoxybenzaldehyde
and 4-butylaniline were mixed and examined by OPM. The
characteristic nematic texture of MBBA was found to be lost
and no new texture formation was observed. The minimum
amount of nanoparticle precursor required to transform the
texture was found to be 40 mol% with respect to MBBA
concentration. Further control experiments utilizing mixtures
In order to verify whether scattering from the metal nano-
particles has contributed to the luminescence signal in the
present study, the excitation spectrum of the sample was taken
and compared with that of the absorption spectrum. The
remarkable similarity between the absorption and excitation
maxima of the MBBA–Ag NP conjugate suggests that the
contribution from scattering towards the signal intensity is
negligible in the present case. The maximum intensity observed
in the excitation spectrum was corresponding to the silver
plasmon absorption, confirming that LC-embedded silver
nanoparticles are responsible for the emission. Emission from
silver nanoparticles stabilized in a polymer matrix has been
reported previously and has been attributed to electronic
transitions between the upper d band and the conducting sp
2
2
band. Emission from silver nanoparticles which are embedded
in dendrimers and of size less than 3 nm was also reported in
of 4-butylaniline and AgNO , as well as 4-methoxybenzaldehyde
3
2
3
and AgNO , were examined through OPM, and no charac-
3
the literature. A close examination of the HR-TEM images
of the MBBA–Ag NP conjugate at higher molar ratios of
AgNO shows the uniform nanocasting of silver nanoparticles
teristic texture formation was observed. FT-IR studies showed
a considerable shift in the stretching frequency of –CQN in
MBBA (from 1625 to 1600 cm ), indicating significant
coordination of MBBA molecules in the MBBA–Ag NP
3
À1
in the LC domain, which could be responsible for the emission
in the system (Fig. 9, right). This is further substantiated by
1
Fig. 7 H NMR spectra of MBBA–Ag NP conjugate prepared using (a) 5 mol% AgNO
3
3
and (b) 80 mol% AgNO after heat treatment. The
signal intensity of the proton of 4-methoxybenzaldehyde increases as the AgNO
3
concentration increases.
This journal is ꢀc The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
New J. Chem., 2010, 34, 420–425 | 423

View Article Online
Fig. 8 Optical polarizing microscopic pictures (magnification 20Â) of an MBBA–Ag NP conjugate prepared using 80 mol% AgNO
3
(a) green
powder obtained directly from the thin film, (b) isotropic phase of the mixture and (c) Sm A granular texture on cooling.
Fig. 9 Left: excitation (a) and emission (b) spectra of an MBBA–Ag NP conjugate in a thin film. For the emission spectrum, the excitation
wavelength was 420 nm. For the excitation spectrum, emission was collected at 500 nm. 80 mol% AgNO was used in this case. Right: HR-TEM
image of MBBA–Ag NP conjugate powder showing the nanocasting (fcc packing) of silver. Scale: 5 nm.
3
the quenching of the luminescence intensity upon dissolution
of the mixture in solvents, where the LC arrangement is not
preserved.
luminescent properties in the LC state upon exciting the silver
plasmon absorption peak. The results from the present study
suggest that nano-scale molecular re-arrangements in liquid
crystals can be utilized to generate distinct texture and optical
properties for the host mesogen.
Control experiments were also performed with (i) MBBA
alone, (ii) a mixture of MBBA, 4-butylaniline and 4-methoxy-
benzaldehyde (1 : 1 molar ratio), and (iii) a mixture of 4-butyl-
aniline and AgNO in thin films (ESI, Fig. S9 and S10w). All of
3
Experimental
the control experiments resulted in the absence of lumines-
cence at 500 nm upon excitation at 420 nm, indicating that the
emission observed from the MBBA–Ag NP conjugate is
unique and originated from the embedded silver nanoparticles
in the LC domain. The luminescent, glassy, smectic MBBA–
Ag NP conjugate was found to be highly stable, especially
when prepared in polyvinyl alcohol-coated glass plates.
Material
The nematic liquid crystal N-(4-methoxybenzylidene)-4-butyl-
aniline (MBBA) was purchased from Aldrich. Dry methanol
was prepared according to standard procedures.
Preparation of silver nanoparticles
Homogeneous solutions of MBBA (0.15 mmol) and silver nitrate
(0.0015 mmol, 0.0045 mmol, 0.0075 mmol and 0.12 mmol) in
Conclusions
5
mL methanol were drop-cast onto a glass slide and the solvent
In the present study, we have investigated the silver nano-
particle-induced texture transformations in nematic MBBA
through in situ formation of the metal nanoparticles in the LC
domain. Based on the SEM, TEM, NMR and OPM results,
we proposed that MBBA reduces silver ions to silver nano-
particles and the resulting MBBA–Ag NP conjugate exhibits
a clear smectic texture. The formation of Ag nanoparticles
in the mesogen leads to hydrolysis of a fraction of MBBA
to 4-methoxybenzaldehyde and 4-butylaniline, followed by
the ordered arrangement of MBBA and its hydrolyzed
products on the nanoparticles. The material exhibits interesting
was allowed to evaporate. The film thus formed was heated to
isotropic temperature and kept at this temperature for 2 min.
The sample was then cooled to room temperature. The NMR
spectra of the MBBA–Ag NP conjugate were recorded on a
Varian 500 MHz spectrometer using CDCl
as solvent.
3
Characterization of the LC
The phase transitions were observed under a polarizing optical
microscope (Nikon Eclipse LV 100 POL) equipped with a
locally made heating and cooling stage. DSC studies were
carried out with a NETZSCH DSC 204 instrument operated
4
24 | New J. Chem., 2010, 34, 420–425
This journal is ꢀc The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

View Article Online
À1
at a scanning rate of 10 1C min under nitrogen atmosphere.
Department of Metallurgical and Materials Engineering, IIT
Madras for HR-SEM images and XRD analysis.
For DSC studies, a homogeneous solution of the mesogen and
silver nitrate in methanol, with different molar ratios, was
drop-cast onto a glass plate, and the solvent was evaporated.
The film thus formed was heated to isotropic temperatures to
generate silver nanoparticles. The material was transferred to
the DSC pan for measurements.
References
1
2
K. Robbie, D. J. Broer and M. J. Brett, Nature, 1999, 399, 764.
H. Qi and T. Hegmann, J. Mater. Chem., 2006, 16, 4197;
T. Hegmann, H. Qi and V. M. Marx, J. Inorg. Organomet. Polym.
Mater., 2007, 17, 483, and references therein.
3
4
L. Cseh and G. H. Mehl, J. Am. Chem. Soc., 2006, 128, 13376.
M. Mitov, C. Portet, C. Bourgerette, E. Snoeck and M. Verelst,
Nat. Mater., 2002, 1, 229.
Characterization of silver nanoparticles
UV-Vis spectra of the silver nanoparticles formed in films were
recorded on a Perkin-Elmer Lambda 25 UV-Visible Spectro-
photometer. The films containing silver nanoparticles in LC
matrix were directly inserted into the UV-Vis spectro-
photometer and the spectrum was recorded while keeping a plain
glass plate as reference. The powder X-ray diffraction study was
carried out for MBBA–Ag NP conjugate (80 mol% AgNO3)
powder on a Bruker AXS-D8 diffractometer (Cu cathode)
equipped with a Lynx detector. Transmission electron micro-
scopy (TEM) images were recorded by using JEM 3010 JEOL,
operated at 200 kV. A homogeneous solution of mesogen and
silver nitrate in methanol was drop-cast onto a Cu grid. The
solvent was allowed to evaporate. After drying the grid, the
sample was heated on a heating stage to obtain isotropic
temperature. The grid was allowed to cool and examined under
an electron microscope. SEM studies were carried out using an
FEI: QUANTA scanning electron microscope, utilizing a silicon
wafer for casting the sample.
5
6
7
8
B. V. Barmatov, D. A. Pebalk and M. V. Bamatova, Langmuir,
004, 20, 10868.
C. Da Cruz, O. Sandre and V. Cabuil, J. Phys. Chem. B, 2005, 109,
14292.
M. Yamada, Z. Shen and M. Miyake, Chem. Commun., 2006,
2569.
C. Da Cruz, O. Sandre and V. Cabuil, J. Phys. Chem. B, 2005, 109,
14292.
2
9 Y.-H. Chen and W. Lee, Appl. Phys. Lett., 2006, 88, 222105.
0 V. A. Mallia, P. K. Vemula, G. John, A. Kumar and P. M. Ajayan,
Angew. Chem., Int. Ed., 2007, 46, 3269.
1 D. T. McCormick, R. Chavers and C. A. Guymon, Macromole-
cules, 2001, 34, 6929.
2 W. Dobbs, J.-M. Suisse, L. Douce and R. Welter, Angew. Chem.,
Int. Ed., 2006, 45, 4179.
3 N. E. Domracheva, A. Mirea, M. Schwoerer, L. L. Torre and
G. Lattermann, ChemPhysChem, 2006, 7, 2567.
14 H. Qi and T. Hegmann, J. Mater. Chem., 2008, 18, 3288.
1
1
1
1
1
1
1
5 L. Huang, H. Wang, Z. Wang, A. Mitra, K. N. Bozhilov and
Y. Yan, Adv. Mater., 2002, 14, 61; R. Patakfalvi and I. Dekany,
´
´
Colloid Polym. Sci., 2002, 280, 461; F. Bouchama,
M. B. Thathagar, G. Rothenberg, D. H. Turkenburg and
E. Eiser, Langmuir, 2004, 20, 477; M. Andersson, V. Alfredsson,
P. Kjellin and A. E. C. Palmqvist, Nano Lett., 2002, 2, 1403.
6 (a) E. B. Barmatov, D. A. Pebalk and M. V. Barmatova, Langmuir,
Fluorescence study
2
004, 20, 10868; (b) N. A. Nikonorova, E. B. Barmatocv,
The luminescence properties (excitation and emission spectra) of
s
the MBBA–Ag NP conjugate were studied in a Fluoromax -4
D. A. Pebalk, M. B. Barmatova, G. Dominguez-Espinosa,
R. Diaz-Calleja and P. Pissis, J. Phys. Chem. C, 2007, 111, 8451;
(c) N. Nishida, Y. Shiraishi, S. Kobayashi and N. Toshima,
J. Phys. Chem. C, 2008, 112, 20284.
(Horiba Jobin Yvon, USA) spectrofluorimeter. The MBBA–Ag
NP conjugate film with various molar ratios of AgNO was
3
7 J. D. S. Newman and G. J. Blanchard, Langmuir, 2006, 22, 5882;
M. Chen, Y.-G. Feng, X. Wang, T.-C. Li, J.-Y. Zhang and
D.-J. Qian, Langmuir, 2007, 23, 5296.
inserted into the fluorimeter and the emission was collected at an
angle of 60 1C, using the solid-state luminescence measurement
set up in Fluoromax -4.
s
18 S. Ke
¨ ¨
ki, J. Torok, G. Deak, L. Daroczi and M. Zsuga, J. Colloid
´ ´ ´
Interface Sci., 2000, 229, 550.
9 L. Huang, H. Wang, Z. Wang, A. Mitra, K. N. Bozhilov and
Y. Yan, Adv. Mater., 2002, 14, 61.
1
Acknowledgements
20 The in situ reduction of silver ions by mesoporous materials
containing grafted imines has recently been reported: Y. Xie,
S. Quinlivan and T. Asefa, J. Phys. Chem. C, 2008, 112, 9996.
21 Liquid Crystals: Applications and Uses, ed. B. Bahadur, World
Scientific Pub. Co. Inc., New Jersey, USA, 1990.
P. K. S. Antharjanam thanks the Department of Science and
Technology (DST) for the financial support through FAST
TRACK scheme (No.SR/FTP/CS-127/2006). The authors
thank Professor T. Pradeep, IIT Madras for HR-TEM images,
Dr K. V. Rama, SAIF, IIT Madras for DSC analysis, and the
2
2 J. Gao, J. Fu, C. Lin, Y. Han, X. Yu and C. Pan, Langmuir, 2004,
0, 9775, and references therein.
23 J. Zheng and R. M. Dikson, J. Am. Chem. Soc., 2002, 124, 13982.
2
This journal is ꢀc The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010
New J. Chem., 2010, 34, 420–425 | 425