Synthesis of mesoporous silica nanosphere using different templates

Article abstract of DOI:10.1016/j.ssc.2007.06.017

Synthesis of mesoporous silica nanosphere were carried out using polyvinyl pyrrolidine and different templates with surfactant property, namely cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, n-octylamine, tetrapropylammonium bromide (TPABr) and these amines give good yield except TPABr. Attempts with other amines without surfactant properties, such as n-propylamine, diethylamine, triethylamine, triethanolamine templates did not give any precipitate in the present reaction scheme. The above synthesis followed by sonication did not change the trend. However addition of dodeycl sodium sulfate surfactant before sonication gave precipitate in all amines, which shows particle growth is induced by surfactant.

Full text of DOI:10.1016/j.ssc.2007.06.017

Solid State Communications 143 (2007) 493–497
www.elsevier.com/locate/ssc
Synthesis of mesoporous silica nanosphere using different templates
∗
N. Venkatathri
Composite Materials Center, Korea Institute of Ceramic Engineering and Technology, 233-5, Gasan-Dong, Guemcheon-Gu, Seoul 153-801, South Korea
Received 25 May 2007; received in revised form 11 June 2007; accepted 12 June 2007 by E.V. Sampathkumaran
Available online 22 June 2007
Abstract
Synthesis of mesoporous silica nanosphere were carried out using polyvinyl pyrrolidine and different templates with surfactant property,
namely cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, n-octylamine, tetrapropylammonium bromide (TPABr) and these
amines give good yield except TPABr. Attempts with other amines without surfactant properties, such as n-propylamine, diethylamine,
triethylamine, triethanolamine templates did not give any precipitate in the present reaction scheme. The above synthesis followed by sonication
did not change the trend. However addition of dodeycl sodium sulfate surfactant before sonication gave precipitate in all amines, which shows
particle growth is induced by surfactant.
ꢀ
c 2007 Elsevier Ltd. All rights reserved.
PACS: 00: General
Keywords: A. Silica; A. Nanomaterials; A. Mesoporous; B. Synthesis
1
. Introduction
and polyvinyl pyrrolidine under base conditions at room
temperature.
There are several works in the literature on formation of
spherical nanosilica materials [1–18] and many of them are
mesoporous spheres [7–18]. These are widely used as small
containers in drug delivery and catalysis [19,20]. Effort has
been made to invent chemical routes for the synthesis of meso-
porous nano spheres [7–18]. The method of using a ‘hard
template’ to control the inner hollow core, also called the core
shell technique, is probably the most effective method for this
purpose [7,8]. Conventionally there are many templates, such
as organic amines and quarternary ammonium salts, available
in literature. Among them, cetyltrimethylammonium bromide,
cetyltrimethylammonium chloride and n-octylamine are used
for mesoporous materials synthesis. Other templates such as
tetrapropylammonium bromide, n-propylamine, diethylamine,
triethylamine and triethanolamine are not attempted. Besides,
polyvinyl pyrrolidine has been used to form hollow struc-
tures [21,22]. But it is not used for mesoporous material syn-
thesis. Further, use of ultrasonication gives hollow nanosphere.
In this paper, we report for the first time, synthesis of
mesoporous silica spheres using different organic templates
2
. Experimental
2.1. Method 1
In a typical synthesis procedure 1.0 g polyvinyl pyrrolidine
(
Aldrich, USA) and 0.46 g NaOH (99%, Hayashi pure
chemical Ind. Co. Ltd., Japan) were dissolved into 120 ml
H2O with stirring. After the solution becomes clear, 1.40 g
cetyltrimethylammonium bromide (99%, Aldrich, USA) was
dissolved completely, 5.6 ml TEOS (98%, Acros organics,
USA) was poured into the above solution under vigorous
stirring. Stirring was continued for 24 h, then sealed in Teflon-
◦
lined autoclaves and heated at 80 C for 48 h.
2.2. Method 2
The synthesis by ultrasonication is as follows. Initially
CTABr was dissolved in a NaOH solution and the resulting
solution was irradiated with a high intensity ultrasound. The
sonication was performed under ambient air conditions with the
temperature at 25–35 C. After 5 min of sonication, TEOS was
added to the solution (0.12 CTAB:0.35 NaOH:1.0 TEOS:922
◦
∗
Corresponding address: Department of Chemistry, Anna University,
Chennai 600 025, Tamil Nadu, India. Tel.: +91 9486565702.
E-mail address: venkatathrin@yahoo.com.
2
H O) using a syringe and the sonication was further continued
0
038-1098/$ - see front matter ꢀc 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ssc.2007.06.017

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N. Venkatathri / Solid State Communications 143 (2007) 493–497
Table 1
Influence of template on synthesis of Mesoporous silica nanosphere by
Methods 1 and 2
S. no. Synthesis
Yield (%) Loss of weight on
calcination (%)
1
2
3
4
5
Cetyl trimethyl ammonium bromide
100
93
2
50
100
54
40
25
18
50
Cetyl trimethyl ammonium chloride
Tetra propylammonium bromide
n-octylamine
Cetyltrimethylammonium bromide
(
ultrasonic)
Cetyltrimethylammonium chloride
ultrasonic)
n-octylamine (ultrasonic)
6
7
95
29
38
20
(
Fig. 1. Low angle X-ray diffraction of samples synthesized by Method 1 using
templates of cetyl trimethylammonium bromide.
Table 2
Influence of template on synthesis of silica hollow sphere by Method 3
SM-300 scanning electron microscope. The copper disc was
pasted with carbon tape and the sample was dispersed over
the tape. The disc was coated with gold in an ionization
chamber. Transmission electron microscopic (TEM) studies
were performed on a JEOL JSM-2000 EX electron microscope
operated at 200 kV. The TEM sample was prepared by dipping
a Cu grid coated with carbon films in sample suspension with
water as solvent (solution was sonicated for 20 min).
S. no.
Template
Yield (%)
1
2
3
4
5
6
7
Cetyltrimethylammonium bromide
Cetyl trimethyl ammonium chloride
n-octylamine
Tetrapropylammonium bromide
n-propylamine
85
100
78
48
72
Di-ethylamine
Triethylamine
21
16
3. Results and discussion
for 1 h. A portion of the above solution was sealed inside a
Teflon lined autoclave and kept at 200 C for 48 h.
The results of various templates on hydrothermal crystalliza-
◦
tion by Method 1 & 2 were given in Table 1. In Method 1, cetyl
trimethylammonium bromide, cetyl trimethyl ammonium chlo-
ride, tetrapropyl ammonium bromide and n-octylamine gave
solid precipitate. However other amines such as n-propylamine,
diethylamine, triethylamine and triethanolamine did not give
any solid product. Calcination of these four products gave a
huge loss (55%) for cetyltrimethylammonium bromide prod-
ucts. N-octylamine gave less loss (18%). Method 2, gave a simi-
lar trend except tetrapropylammonium bromide did not give any
residue. It has to be noted that in Method 3 we got precipitate
when we used all the above templates (Table 2). This reveals
the importance of surfactants in aqueous phase reaction. Long
chain amines have hydrophilic and hydrophobic ends (surfac-
tant). The synthesis involves two phases namely aqueous and
organic phase (TEOS). They are not miscible with each other.
To carry out the reaction in such a condition, the surfactant
will facilitate one end in aqueous phase and another in organic
phase. As tetrapropylammonium bromide is a weak surfactant,
it gave little yield.
2
.3. Method 3
Initially 3 ml sodium dodecyl sulphonate (SDS) solution
(
aqueous, 1%) was introduced into a centrifugal tube and
irradiated in an ultrasound water bath sonicator for 5 min.
The sonication was performed under ambient air conditions
during the whole process. Then 0.05 g tetrapropylammonium
bromide (TPABr) was dissolved into the above solution
and the sonication was further continued for 5 min. Next
0
.5 ml tetraethylorthosilicate (TEOS) was added to the cationic
solution and sonicated for another 2 min. The final molar
ratio was 0.046SDS:0.084TPABr:1.0TEOS:74H2O. Then this
reaction mixture was transferred into 100 ml Teflon lined
stainless autoclave. Heat treatment on the autoclave was
◦
conducted at 180 C in an oven for 24 h.
The solid product was recovered by filtration, then washed
with distilled water and dried under vacuum at room
temperature. A portion of the as-synthesized product was
◦
calcined in air at 550 C for 10 h to remove the templates.
The low angle X-ray diffraction pattern (Fig. 1) shows a high
◦
The other templates used in all the above synthesis
were cetyltrimethylammonium chloride, tetrapropylammonium
bromide, n-octylamine (99%, Aldrich, USA), n-propylamine,
diethylamine (Osaka Hayashi Pure Chemical Industries Ltd.,
Japan), triethylamine and triethanolamine. The results are given
in Tables 1 and 2.
intensity peak around 2.5 for the samples synthesized using
cetyltrimethylammonium bromide, cetyltrimethylammonium
chloride and n-octylamine by Method 1. So they are found
to be mesoporous. Other samples synthesized with different
templates did not show such a peak.
SEM analysis (Fig. 2) reveals the sample synthesized by
Method 1 from CTABr has particle size 500 nm–2 µm with
spherical shape, CTACl also having spherical shape with
100–300 nm size and the sample synthesized with n-octylamine
has spherical platelets with 200–400 nm size. TEM analysis
(Fig. 3) shows that the samples synthesized by Method 1
X-ray diffraction analysis was carried out using a Mac
Science Co. Ltd., MO3XHF22 instrument in the range
◦ ◦
1
.5 –10 . BET surface area analysis was carried out using
a Micromeritics Tristar surface area and porosity analyzer.
The particle size and shape were analyzed by a Topcon,

N. Venkatathri / Solid State Communications 143 (2007) 493–497
495
Fig. 2. SEM photograph of as-synthesized form of sample from (a) cetyl trimethylammonium bromide, (b) cetyl trimethyl ammonium chloride and (c) n-octylamine
by Method 1.
Fig. 3. TEM photograph of calcined form of sample from (a) cetyl trimethyl ammonium bromide, (b) cetyl trimethyl ammonium chloride and (c) n-octylamine by
Method 1.

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N. Venkatathri / Solid State Communications 143 (2007) 493–497
Fig. 4. FT-IR spectrum of sample synthesized by Method 1 using cetyl
trimethyl ammonium bromide.
using CTABr and CTACl are of spherical hollow type with
2
0–50 nm size and the sample synthesized from n-octylamine
has spherical hollow type sizes with size 300 nm with 25 nm
wall size.
The FT-IR spectrum of as-synthesized mesoporous nano-
sphere samples from Method 1 shows a pattern simillar
−
1
to Fig. 4, which reveals peaks around 1700 cm
3
and
−
1
Fig. 5. N adsorption and desorption isotherm of sample synthesized by
2
Method 1 using cetyltrimethylammonium bromide template.
430 cm , corresponding to the carboxyl and hydroxyl
groups [23], respectively. The carboxyl peak appeared from
atmospheric carbon dioxide. The adsorption peak belonging to
the Si–O stretching vibration of the Si–OH bond appears at
irrespective of its nature. So, it was found that the
surfactant property of the template or surfactant is essential
for precipitation. Calcination followed by TEM analysis
gives hollowspheres with mesoporous properties in CTABr,
CTACl and n-octylamine containing products. However these
properties change depend on the template.
− −1
1
9
60 cm [24]. The weak peaks at 2855 and 2920 cm belong
to the stretching vibrations of C–H bonds, which show that a
few organic groups are adsorbed on the spheres. The strong
peaks near 1100, 802 and 467 cm agree with a Si–O–Si bond,
which implies the condensation of silicon alkoxide [25].
Nitrogen adsorption–desorption isotherms of the samples
synthesized using CTABr, CTACl and n-octylamine by Method
−
1
Acknowledgement
1
show a curve simillar to the pattern given in Fig. 5. They show
a type IV hysteresis characteristic of mesoporous materials. The
The author thanks the Brain Pool Program, South Korea, for
a fellowship.
BET surface area of the sample was found to be 900, 850 and
2
6
30 m /g and the average pore diameter was found to be 40, 32
˚
and 26 A.
It is found that polyvinylpyrrolidine (PVP) has a key
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