Optically active polyurethane@indium tin oxide nanocomposite: Preparation, characterization and study of infrared emissivity

Article abstract of DOI:10.1016/j.materresbull.2012.05.045

Optically active polyurethane@indium tin oxide and racemic polyurethane@indium tin oxide nanocomposites (LPU@ITO and RPU@ITO) were prepared by grafting the organics onto the surfaces of modified ITO nanoparticles. LPU@ITO and RPU@ITO composites based on t

Full text of DOI:10.1016/j.materresbull.2012.05.045

Materials Research Bulletin 47 (2012) 2264–2269
Contents lists available at SciVerse ScienceDirect
Materials Research Bulletin
journal homepage: www.elsevier.com/locate/matresbu
Optically active polyurethane@indium tin oxide nanocomposite: Preparation,
characterization and study of infrared emissivity
a
a,
a
b
Yong Yang , Yuming Zhou *, Jianhua Ge , Xiaoming Yang
a
School of Chemistry and Chemical Engineering, Southeast University, Jiangsu Optoelectronic Functional Materials and Engineering Laboratory, Nanjing 211189, PR China
Suzhou Sidike New Material Technology Co., Ltd., Suzhou 215400, PR China
b
A R T I C L E I N F O
A B S T R A C T
Article history:
Optically active polyurethane@indium tin oxide and racemic polyurethane@indium tin oxide
nanocomposites (LPU@ITO and RPU@ITO) were prepared by grafting the organics onto the surfaces of
modified ITO nanoparticles. LPU@ITO and RPU@ITO composites based on the chiral and racemic tyrosine
were characterized by FT-IR, UV–vis spectroscopy, X-ray diffraction (XRD), SEM, TEM, and thermo-
Received 5 September 2011
Received in revised form 16 April 2012
Accepted 23 May 2012
Available online 1 June 2012
gravimetric analysis (TGA), and the infrared emissivity values (8–14
mm) were investigated in addition.
The results indicated that the polyurethanes had been successfully grafted onto the surfaces of ITO
without destroying the crystalline structure. Both composites possessed the lower infrared emissivity
values than the bare ITO nanoparticles, which indicated that the interfacial interaction had great effect on
the infrared emissivity. Furthermore, LPU@ITO based on the optically active polyurethane had the virtue
of regular secondary structure and more interfacial synergistic actions between organics and inorganics,
thus it exhibited lower infrared emissivity value than RPU@ITO based on the racemic polyurethane.
ß 2012 Elsevier Ltd. All rights reserved.
Keywords:
A. Composites
A. Polymers
A. Semiconductors
D. Optical properties
1
. Introduction
In the last decades, an intense attention has been arisen to
reflectivity for infrared, favorable chemical stability and so forth. It is
widely used in photoelectric material, display technique, construction
engineer, etc. [13–17]. However, to the best of our knowledge, ITO is
mainly applied with the thin-film form and few reports have related to
the pulverous ITO grafted with optically active polymers.
investigations dealing with optically active macromolecules for their
unique characteristics, such as orderly secondary structure, adjust-
able chiral parameter, and abundant inter-chain interaction [1,2].
Opticallyactivepolymersderivedfromaminoacidsareofinterestdue
to their inherent biological compatibility and degradability, which
make them ideal candidates for a variety of biomaterial applications
Controlling the temperature and infrared emissivity of the object
arebothofthecommonmethodsininfraredcamouflage[18,19]. The
decrease of infrared emissivity becomes especially important on the
occasion of that the temperature could not be reduced [20]. Among
most of the Infrared low-emissive materials, organic/inorganic
composites especially have the potential for applications by means
of combining the structure tunability of organics and the robustness
and chemical inertness of inorganics. In the present study, optically
active polyurethane@indium tin oxide (LPU@ITO) and racemic
polyurethane@indium tin oxide (RPU@ITO) nanocomposites based
on tyrosine were prepared after the surface modification of ITO
nanoparticles. On the basis of microstructure analysis of the
nanocomposites, the effect of macromolecular conformations and
the interfacial interactions between organics and inorganics on the
properties of infrared emissivity were discussed.
[
3,4]. Moreover, amino acid-based chiral polymers could have
induced crystallinity with the ability to form higher ordered
structures that exhibit enhanced properties. The polymethionine
membraneand itsoxidizedmembraneshow highoxygen permeabil-
ity [5]. Poly(c-alkyl a-glutamic acid)s are used as surface treatment
reagents of artificial leathers, and examined as liquid crystalline
materials, piezoelectric materials, and LB films [6,7]. Peptides
consisting of L-leucine, L-alanine, and L-lysine show an artificial
enzymatic behavior in the decarboxylation of oxaloacetate [8].
Recently, special interest has focused on the functionalized metal
oxide nanoparticles in terms of their potential applications to
biomedical, catalytic, and optical materials [9–12]. Indium tin oxide
(ITO)isadopeddegeneratesemiconductormaterialwiththeproperties
2. Experimental
of high conductivity and transparency under visible light, intense
2.1. Materials
*
Corresponding author. Tel.: +86 25 52090617; fax: +86 25 52090617.
Metal indium (ꢀ99%) was obtained from Shanghai Long Jin
E-mail address: ymzhou@seu.edu.cn (Y. Zhou).
Metal Material Limited Company. SnCl
ꢁ5H
2
O (analytical reagent)
4
0025-5408/$ – see front matter ß 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.materresbull.2012.05.045

Y. Yang et al. / Materials Research Bulletin 47 (2012) 2264–2269
2265
1
was produced by Shanghai No. 4 Reagent & H.V. Chemical Limited
Company. -Tyrosine, DL-tyrosine, triethylamine, hydrochloric acid
analytical reagent), and ammonia water (25%) were all purchased
methanol). H NMR (300 MHz, DMSO-d
6
):
d
0.82–0.8 (t, J = 6.48 Hz,
L
3H, –CH
2.89–3.10 (m, 2H, –PhCH
6
4.10–4.14 (t, J = 6.99 Hz, 1H, CH–), 6.68–7.01 (m, 4H, –C H
3
), 1.20–1.25 (m, 6H, –CH
2
–), 1.43–1.47 (m, 2H, –CH
2
2
4
–),
–),
–),
(
2
–), 4.00–4.05 (t, J = 6.42 Hz, 2H, –OCH
from Shanghai Chemical Reagent Company and used as received
+
ꢂ
ꢂ1
without further purification. Methyltrioctylammonium chloride
8.55 (s, 3H, –N H
H), 2953, 2869, 1738 (C 55 O), 1516, 1230, 843.
DL-Tyrosine hexyl ester hydrochloride was prepared in the
3
Cl ), 9.41 (s, 1H, –OH). FT-IR (
n
/cm ): 3297 (O–
1
(
Aliquat 336) was produced by Acros Organics. Triphosgene and
g
-aminopropyltriethoxysilane (KH550) were obtained from
Aldrich. Thionyl chloride, 1-hexanol and other solvents were all
obtained from Shanghai Chemical Reagent Company and distilled
by the standard methods. Deionized water was used for all
experiments.
similar way using DL-tyrosine instead of
L
-tyrosine. White solid.
2
5
ꢅ
Yield: 14.3 g (95%). Mp: 176–179 8C.
½a
ꢄ
¼ 0 (C = 1 g/dL,
D
1
methanol). Its H NMR, IR data are similar to
ester hydrochloride and thus omitted.
L-tyrosine hexyl
2.2. Analysis and characterization
2.4.2. Isocyanate–phenols
Phosgene was obtained by decomposition of triphosgene with
1
Melting point (mp) was determined by using an X-4 micro-
Aliquat 336 according to the literature [22]. The phosgene that
melting point apparatus. The optical rotations were measured
on a WZZ-2S (2SS) digital automatic polarimeter at room
temperature and the wavelength of sodium lamp was
developed during the reaction was collected in CH
preserved below 0 8C. 1.51 g -tyrosine hexyl ester hydrochloride
was added to the stirred solution of phosgene (5–10 g, 0.05–
0.1 mol) in 50 mL CH Cl
saturated aqueous sodium bicarbonate was dropped slowly within
10 min. The resultant mixture was stirred at 0–5 8C for an hour and
then bubbled with nitrogen in order to remove the residual
phosgene. The organic layer was collected, and the aqueous layer
2 2
Cl and
L
5
2
89.44 nm. FT-IR spectra were recorded on a Bruker Tensor
2
2
which was kept at ꢂ5 8C. Then 50 mL of
1
7 FT-IR spectrometer at room temperature using KBr pellets. H
1
3
and C NMR spectra measurements were recorded on a Bruker
AVANCE 300 MHz NMR spectrometer. Chemical shifts were
reported in ppm. UV–vis spectra were recorded with a Shimadzu
UV 3600 spectrometer using a 10 mm quartz cell at room
temperature. X-ray diffraction (XRD) measurements were
carried out on a Rigaku D/MAX-R with a copper target at
was extracted with three 5-mL portions of CH
organic layers were dried (MgSO ), vacuum filtered, and concen-
trated to 20 mL to afford the colorless isocyanate of -tyrosine
2 2
Cl . The combined
4
L
4
0 kV and 30 mA. The powder samples were spread on a sample
hexyl ester solution. The solution was used in the polymerization
without further isolation. The isocyanate of DL-tyrosine hexyl ester
was prepared in the similar way using DL-tyrosine hexyl ester
holder, and the diffractograms were collected from 58 to 808 at
the speed of 58/min. Thermal analysis experiments were
performed using a TGA apparatus operated in the conventional
TGA mode (TA Q-600, TA Instruments) at the heating rate of
hydrochloride instead of
L-tyrosine hexyl ester hydrochloride.
The spectroscopic data of isocyanate–phenol are as follows
1
1
0 K/min in a nitrogen atmosphere, and the sample size was
about 50 mg. TEM micrographs were obtained using a Hitachi H-
00 microscope operating at 120 kV. Samples were prepared by
(take isocyanate of
(300 MHz, CDCl ):
6H, –CH –), 1.58–1.60 (m, 2H, –CH
), 4.09–4.13 (t, J = 6.54 Hz, 2H, –OCH
L
-tyrosine hexyl ester for example). H NMR
0.84–0.88 (t, J = 6.15 Hz, 3H, –CH ), 1.27 (m,
–), 2.91–2.93 (m, 2H, –PhCH
–), 4.38 (m, 1H, CH–), 6.67–
–). C NMR (75 MHz, CDCl ): 13.9, 22.5, 25.4,
3
d
3
6
2
2
2
–
placing the particle suspensions on a Cu grid (200 mesh; placed
onto filter paper to remove excess solvent) and allowing the
solvent to evaporate at room temperature. SEM images were
obtained on the LEO-1530VP microscope. Infrared emissivity
values of the samples were investigated on the IRE-I Infrared
Emissometer of Shanghai Institute of Technology and Physics,
China.
2
1
3
6.96 (m, 4H, –C
6
H
4
3
d
28.4, 31.3, 39.1, 58.8, 66.7, 115.5, 127.5 (N 55 C 55 O), 130.6, 154.9 (C–
ꢂ1
OH), 170.8 (C 55 O). FT-IR (
n
/cm ): 3419 (O–H), 2957, 2932, 2259 (–
N 55 C 55 O), 1738 (C 55 O), 1516, 1004, 834.
2.5. Preparation of LPU@ITO and RPU@ITO composites
2.3. Preparation of ITO and A-ITO
The prepolymerization of isocyanate of
L-tyrosine hexyl ester
was carried out in the CH Cl solution with magnetic stirring under
2
2
ITO nanoparticles with the In:Sn atomic ratio as 90:10 were
prepared by chemical co-precipitation process and calcinated at
00 according to the literature [21]. 2 g of ITO nanoparticles were
dispersed into 50 mL anhydrous ethanol with ultra-sonic to obtain
the suspension, 0.5 mL of KH550 was then added. The mixture was
exposed to high-intensity ultrasound irradiation for 1 h at 25 8C
and refluxed for 4 h. The resulting KH550-modified ITO nanopar-
ticles were separated by centrifuge and washed with ethanol and
deionized water to obtain A-ITO.
nitrogen at room temperature for 8 h by addition of triethylamine
(3 mol%) as the catalyst. Then A-ITO was dispersed into reactor and
refluxed for 10 h. After cooling to room temperature, the mixture
was centrifuged, thoroughly washed with diethyl ether and dried
in vacuum to obtain LPU@ITO composite. Fig. 1 shows the scheme
of the process of preparation and the RPU@ITO composite was
prepared in a similar way.
6
3. Results and discussion
2.4. Monomer synthesis
3.1. FT-IR and UV–vis spectra analysis
2
.4.1. HC1 salts
Fig. 2 shows the FT-IR spectra of ITO, A-ITO, LPU@ITO, and
RPU@ITO composites. For the bare ITO, three peaks at 498, 568, and
L-Tyrosine hexyl ester hydrochloride was prepared as follows:
ꢂ1
to 1-hexanol (75 mL) at ꢂ5 8C, thionyl chloride (6.55 g, 0.055 mol)
603 cm are assigned to the phonon vibrations of In–O bonds and
ꢂ1
was dropped slowly in order to maintain the temperature under
2 3
are characteristic of cubic In O [23]. Except the band at 3405 cm
0
8C. Then
L
-tyrosine (9.05 g, 0.05 mol) was added. The resulting
belonging to hydroxyl groups on the surface of ITO, there is no
absorption between 750 and 3500 cm because of the intense
ꢂ1
mixture was stirred at 95 8C for 12 h. As the mixture cooled, the
product was precipitated by the addition of diethyl ether (200 mL).
The precipitate was collected, washed with ether (2ꢃ 50 mL) and
reflection effect of ITO against infrared. After the surface
modification of ITO under ultrasonic radiation, the peaks of
methyl, methylene, and N–H group of KH550 are found at
dried to give the white powdery
L
-tyrosine hexyl ester hydrochlo-
2
5
ꢅ
ꢂ1 ꢂ1 ꢂ1
ride. Yield: 13.4 g (89%). Mp: 162–164 8C. ½
aꢄ
¼ þ7:6 (C = 1 g/dL,
2850 cm , 2935 cm , and 3415 cm , respectively. As it can
D

2
266
Y. Yang et al. / Materials Research Bulletin 47 (2012) 2264–2269
Fig. 1. Scheme of preparation of LPU@ITO composite.
be seen in Fig. 2c and d, the characteristic absorptions correspond-
formation of organic–inorganic composite. As shown in Fig. 4, the
characteristic peaks at 2 = 21.5, 30.5, 35.4, 51.0, and 60.78
correspond to the primary diffractions of (2 1 1), (2 2 2), (4 0 0),
(4 4 0), and (6 2 2) crystalline planes in cubic bixbyite structure of
ing to the C 55 O groups of hexyl ester and carbamate have appeared
u
ꢂ1
ꢂ1
at 1736 cm and 1711 cm after the grafting by LPU and RPU.
The UV–vis spectra of ITO before and after being grafted by
polyurethanes are displayed in Fig. 3. No absorption is observed for
the pure nanoparticles because of the strong scattering process
from ITO. As shown in the spectra of RPU@ITO and LPU@ITO
the In
compounds were detected indicating that the tin atoms were
doped substitutionally in the In lattice [24,25]. For the
2 3
O . No phases corresponding to tin or to other tin
2 3
O
composites, the bands corresponding to the
p
–
p
* transition of the
composites, besides the crystalline peaks of ITO, the diffractograms
display partially crystalline areas at about 218 which could be
assigned to the presence of hard segment in the polyurethane such
as benzene rings. The diffraction patterns of ITO in the composites
are coincident with the bare ITO nanoparticles, which suggest that
no change of crystal parameters occurred during the process of
grafting and the reactions just take place on the surface of ITO.
aromatic rings and n– * transition of carbonyl groups, in the
p
macromolecular chain, have appeared around 235 nm and 265 nm,
respectively. Both of the spectroscopic analyses indicate that the
grafting reactions have taken place as expected.
3.2. XRD analysis
The crystalline structure analyses of ITO, RPU@ITO, and
3.3. Morphological analysis
LPU@ITO composites are also carried out in order to verify the
SEM images of ITO, RPU@ITO, and LPU@ITO composites are
shown in Fig. 5. As can be seen in Fig. 5a, the ITO nanoparticles
Fig. 2. FT-IR spectra of: (a) ITO, (b) A-ITO, (c) RPU@ITO, and (d) LPU@ITO composites.
Fig. 3. UV–vis spectra of ITO, RPU@ITO and LPU@ITO composites.

Y. Yang et al. / Materials Research Bulletin 47 (2012) 2264–2269
2267
Fig. 6 shows the TEM photographs of ITO before and after being
grafted by polyurethanes. As shown in Fig. 6a, ITO exhibits globular
structure and some of them assemble into larger aggregates. The
sectional area electron diffraction pattern (Fig. 6a, inset) shows a
typical polycrystalline composition of ITO with no preferred
orientation that corresponds to the XRD analysis. After the
organification with polyurethanes, RPU@ITO and LPU@ITO nano-
composites (Fig. 6b and c) show a distinct layer of amorphous
surroundings with the thickness about 10 nm. It is noteworthy that
the dispersion degree of ITO has been maintained in the main for
LPU@ITO compared with the nanoparticles prior to grafting. The
extent of aggregation becomes more serious for RPU@ITO though
the ultrasonic dispersion is adopted during both of the reactions.
This demonstrates that optically active polyurethane with orderly
secondary structure possesses the advantage of less steric
hindrance which contributes to the uniform wrapping. On the
contrary, racemic polymer with the random coiled molecular chain
assembles the nanoparticles and leads to the package involving a
number of ITO nanoparticles. In addition, we could conclude that
organic polymers have been successfully grafted onto the surfaces
of ITO.
Fig. 4. XRD patterns of: (a) ITO, (b) RPU@ITO, and (c) LPU@ITO composites.
3.4. Thermal stability analysis
show spherical shape with
a narrow range of grain size
distribution, and the average diameter of them is 60 nm or so. It
can be clearly observed that the nanoparticles have some
agglomerations. As expected, in Fig. 5b and c, the spheres
universally present some increase in size and shape, which
indicate that the ITO is thoroughly wrapped by organics.
Furthermore, it should be noted that, the RPU@ITO presents larger
aggregates than LPU@ITO due to the grafting over more ITO
nanoparticles.
The thermogravimetric analysis (TGA) was employed for
determining the amount of organics grafted onto ITO. The weight
loss curves of ITO, RPU@ITO, and LPU@ITO composites are
presented in Fig. 7. The slight weight loss in Fig. 7a is assigned
to the release of moisture adsorbed and structure water for the
bare ITO. In curves b and c, the main weight losses starting at about
200 8C are assigned to the thermal decomposition of polymers. The
amounts of polyurethanes grafted onto the ITO are about 0.26 g/g
Fig. 5. SEM micrographs of: (a) ITO, (b) RPU@ITO, and (c) LPU@ITO composites.

2
268
Y. Yang et al. / Materials Research Bulletin 47 (2012) 2264–2269
Fig. 6. TEM micrographs of: (a) ITO, (b) RPU@ITO, and (c) LPU@ITO composites.
and 0.32 g/g inorganics for RPU@ITO and LPU@ITO, respectively. It
is worth noting that the weight loss of LPU@ITO derived from chiral
tyrosine is larger than that of RPU@ITO derived from racemic
tyrosine, and this may result from the different chain conforma-
tions. Optically active LPU with regular macromolecular structure
facilitates the dispersion and grafting of ITO, which correspond to
the morphological analyses above.
infrared emissivity values of the samples at wavelength of
8–14 m are investigated and listed in Table 1. The pure ITO
m
nanoparticles have relative higher infrared emissivity value of
0.701. After being grafted with polymers, the infrared emissivity
values of RPU@ITO and LPU@ITO composites are reduced to
0.596 and 0.512, respectively. This suggests that the synergistic
effect between the grafted polyurethanes and ITO nanoparticles
plays an important role in the decreasing of infrared emissivity.
The interfacial interactions reinforced by the coupling agent
alter the vibration mode of molecules, atoms or pendant groups
on the interface between organic and inorganic components,
which had direct influence on infrared emissivity [28,29].
Moreover, LPU@ITO composite based on the optically active
polyurethane exhibits lower infrared emissivity value than
RPU@ITO which base on the racemic polyurethane. On one hand,
LPU@ITO with the wrapping of optically active polyurethane
possesses the larger grafting amount of organics. This implies
more interfacial layers and interfacial interactions. On the other
hand, it is well known that organic polymers have high infrared
emissivity values due to their high unsaturated groups in the
structure. The orderly secondary structure of macromolecular
chain could lead to the formation of massive intermolecular
interactions easily, which reduce the index of hydrogen
deficiency and the unsaturated degree [30]. Therefore, the
3.5. The infrared emissivity analysis
Several of inorganic materials especially semiconductive
nanoparticles have been used in reducing infrared emissivity of
the object, and ITO is of great value among them [26,27]. The
Table 1
Infrared emissivity values of samples.
Samples
Infrared emissivity (eTIR at 8–14 mm)
ITO
0.701
0.596
0.512
RPU@ITO
LPU@ITO
Fig. 7. TGA curves of: (a) ITO, (b) RPU@ITO, and (c) LPU@ITO composites.

Y. Yang et al. / Materials Research Bulletin 47 (2012) 2264–2269
2269
References
infrared emissivity value of LPU@ITO is lower than that of
RPU@ITO.
[1] E. Yashima, K. Maeda, H. Iida, Y. Furusho, K. Nagai, Chem. Rev. 109 (2009) 6102–6211.
2] R. Nomura, J. Tabei, T. Masuda, J. Am. Chem. Soc. 123 (2001) 8430–8431.
[
4
. Conclusions
[3] M. Okada, Prog. Polym. Sci. 27 (2002) 87–133.
[4] R. Katsarava, V. Beridze, N. Arabuli, D. Kharadze, C.C. Chu, C.Y. Won, J. Polym. Sci.
Polym. Chem. 37 (1999) 391–407.
LPU@ITO and RPU@ITO nanocomposites were prepared after
[5] S.I. Aiba, N. Minoura, Y. Fujiwara, J. Appl. Polym. Sci. 27 (1982) 1409–1411.
the surface modification of ITO nanoparticles by silane coupling
agent, and the infrared emissivity values at wavelength of 8–
14 mm were investigated. LPU@ITO and RPU@ITO showed lower
[6] Y. Matsuoka, R. Kishi, M. Sisido, Polym. J. 25 (1993) 919–927.
[
[
[
7] F. Sanda, T. Endo, Macromol. Chem. Phys. 200 (1999) 2651–2661.
8] K. Johnsson, R.K. Allemann, H. Widmer, S.A. Benner, Nature 365 (1993) 530–532.
9] S.C. McBain, H.H.P. Yiu, A. El Haj, J. Dobson, J. Mater. Chem. 17 (2007) 2561–2565.
infrared emissivity values than bare ITO nanoparticles by virtue
of the interfacial synergistic actions between organics and
inorganics. LPU@ITO composite based on the optically active
polyurethane possessed stronger interfacial interactions than
RPU@ITO by means of the less steric hindrance and more
interfacial layers. In addition, the orderly secondary structure of
organics would easily lead to the formation of intermolecular
interactions. Both of them resulted in the decrease of infrared
emissivity. Consequently, LPU@ITO exhibited an infrared emis-
sivity value down to 0.512 that is lower than RPU@ITO.
[10] M.Z. Kassaee, H. Masrouri, F. Movahedi, Appl. Catal. A: Gen. 395 (2011) 28–33.
[11] M.A. Neouze ans, U. Schubert, Monatsh. Chem. 139 (2008) 183–195.
[12] D. Bhattacharya, M. Das, D. Mishra, I. Banerjee, S.K. Sahu, T.K. Maiti, P. Pramanik,
Nanoscale 3 (2011) 1653–1662.
[13] M.J. Alam, D.C. Cameron, Thin Solid Films 377 (2000) 455–459.
[14] T.K. Yong, S.S. Yap, G. Safran, T.Y. Tou, Appl. Surf. Sci. 253 (2007) 4955–4959.
[
[
[
15] G. Grolig, K.H. Kochem, Adv. Mater. 4 (1992) 179–188.
16] N.G. Patel, P.D. Patel, V.S. Vaishnav, Sens. Actuators B: Chem. 96 (2003) 180–189.
17] H.N. Chen, L.Q. Zhu, W.P. Li, H.C. Liu, Mater. Lett. 64 (2010) 781–784.
[18] S.P. Mahulikar, H.R. Sonawane, G.A. Rao, Prog. Aerosp. Sci. 43 (2007) 218–245.
[19] S.P. Mahulikar, G.A. Rao, P.S. Kolhe, J. Aircraft 43 (2006) 226–232.
[20] B.V. Bergeron, K.C. White, J.L. Boehme, A.H. Gelb, P.B. Joshi, J. Phys. Chem. C 112
(2008) 832–838.
[
[
21] Y.X. Zhao, B.L. He, S.W. Qiang, C. Peng, Chin. J. Inorg. Chem. 6 (2006) 1033–1037.
22] L. Pasquato, G. Modena, L. Cotarca, P. Delogu, S. Mantovani, J. Org. Chem. 65 (2000)
Acknowledgments
8224–8228.
[23] S.K. Poznyak, A.I. Kulak, Electrochim. Acta 45 (2000) 1595–1605.
The authors are grateful to the National Nature Science
Foundation of China (51077013, 50873026), Special Funds for
Jiangsu Province Scientific and Technological Achievements
Projects of China (BA2011086), Program for Training of 333
High-Level Talent, Jiangsu Province of China (BRA2010033), the
Key Program for the Scientific Research Guiding Found of Basic
Scientific Research Operation Expenditure, Southeast University
[24] P.K. Biswas, A. De, L.K. Dua, L. Chkoda, Appl. Surf. Sci. 253 (2006) 1953–1959.
[25] T. Suzuki, M. Suzuki, Y. Sawada, J. Matsushita, Thermochim. Acta 352 (2000) 87–90.
[
[
26] F.L. Du, N. Wang, D.M. Zhang, Y.Z. Shen, J. Rare Earth 28 (2010) 391–395.
27] W.J. Zhang, T.M. Wang, L.Z. Zhong, X.W. Wu, M. Cui, Acta Phys. Sin. 54 (2005)
4439–4444.
[28] S.K. Andersson, O. Staaf, P.O. Olsson, A. Malmport, C.G. Ribbing, Opt. Mater. 10
1998) 85–93.
(
[
[
29] B.P. Lin, H.J. Liu, S.X. Zhang, C.W. Yuan, J. Solid State Chem. 177 (2004) 3849–3852.
30] Z.Q. Wang, Y.M. Zhou, Y.Q. Sun, Q.Z. Yao, Macromolecules 42 (2009) 4972–
4976.
(3207041102) for financial support.