Materials Chemistry and Physics 100 (2006) 507–512
Facile synthesis and characterization of novel nanocomposites
of titanate nanotubes and rutile nanocrystals
Jiaguo Yu
∗
, Huogen Yu
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
Received 23 July 2005; received in revised form 20 January 2006; accepted 4 February 2006
Abstract
The nanocomposites of one-dimensional (1D) titanate nanotubes and 0D rutile nanocrystals were fabricated by hydrothermal treatment of bulky
rutile TiO
2
powders in a 10 M NaOH solution without using any templates and catalysts. The as-prepared samples were characterized with transmis-
sion electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller
(BET) surface area, Fourier transform infrared spectroscopy (FTIR), UV–visible spectrophotometry (UV–vis), Raman spectroscopy and X-ray
photoelectron spectroscopy (XPS). It was found that many small rutile nanocrystal particles of about 5 nm could uniformly attach to the outer
surface and in the inner of the titanate nanotubes, forming an interesting and novel nanocomposite structure. Adjusting reaction time could control
the amount of rutile nanoparticles in the nanocomposites. With increasing reaction time, the specific surface areas, porosity, pore volume, UV
absorption and band gap energies of the nanocomposites gradually increased due to the fact that rutile particles were steadily turned into the tubular
nanocomposites, finally completely formed titanate nanotubes.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Nanocomposites; Nanotubes; Nanocrystals; Fabrication; Hydrothermal reaction
1. Introduction
The controlled synthesis of inorganic materials with specific
size and morphology is an important aspect in the development
of new materials in many fields such as advanced materials,
catalysis, medicine, electronics, ceramics, pigments, cosmet-
ics, etc. [1,2]. Since the discovery of carbon nanotubes in 1991
[3], one-dimensional (1D) nanostructured materials (nanotubes,
nanobelts, nanowires and nanorods) have attracted consider-
able attention due to their distinctive geometries, novel physical

2
(such as nanotubes [19–21], nanobelts
[22,23] and nanowires [24,25]), including sol–gel, templates
and hydrothermal synthesis, these methods have mainly been
concentrated on monomorphic 1D nanostructures, such as nan-
otubes, nanobelts and nanowires, etc. However, the synthesis
of the nanocomposites of 1D nanostructures and 0D nanocrys-
talline remains a challenge to materials scientists [26,27].
Herein, we report that the nanocomposites of titanate nan-
otubes and rutile nanocrystals can be easily obtained by a simple
hydrothermal treatment of bulky rutile TiO
2
particles in a 10 M
NaOH solution without using any templates and catalysts.
2. Experimental
In a typical synthesis, titania powders (0.5 g, about 50–300 nm in size, pre-
pared by calcining P25 at 900
◦
C for 2 h) and an aqueous solution of NaOH
(10 M, 150 ml) were placed into a 200 ml Teflon-lined autoclave. The mixture
0254-0584/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.matchemphys.2006.02.002
508 J. Yu, H. Yu / Materials Chemistry and Physics 100 (2006) 507–512
was stirred for 10 minto form a milk-like suspension, sealed and hydrothermally
treated at 140
◦
C for 24, 48, 96 and 144 h, respectively. The white precipitate was
collected and washed with distilled water until a pH value near 6 was reached.
The precipitate was then ground in alcohol followed by ultrasonic-assisted dis-
persion. After a second filtration and alcohol washing step, the sample was

) and pore size distribution were determined using a
Micromeritics ASAP 2010 nitrogen adsorption apparatus. All the samples mea-
sured were degassed at 100
◦
C before the actual measurements.
3. Results and discussion
Fig. 1 shows the TEM, HRTEM images and SAED pattern of
the starting material (rutile) and the products. The particle size
of the starting material is from several tens to several hundreds
of nanometers (Fig. 1a). Fig. 1b and c show the TEM images
of the products obtained by a hydrothermal reaction at 140
◦
C
for 48 and 96 h, respectively. The parent long titanate nanotubes
were formed by a hydrothermal reaction of rutile TiO
2
ina10M
NaOH solution. Many rutile nanocrystals of 5–10 nm attached
to the outer surface of the titanate nanotubes and some rutile
nanocrystals of about 5 nm also existed in the inner of the nan-
otubes, forming an interesting composite structurethat possesses
both the surface properties of rutile nanocrystals and most mor-
phology and mechanical properties of titanate nanotubes. The
phase structures of the nanocomposites were confirmed by the
XRD patterns of the samples. The diffraction peaks from both
rutile and the parent titanate could be observed in the reaction
products (Fig. 2b and c). To the best of our knowledge, this is the
first time to observe this novel morphological structure of the
nanocomposites of rutile nanocrystals and titanate nanotubes.
Fig. 2. XRD patterns of the starting material (a) and the products prepared by

nanotubes is shown in Fig. 2f. Unlike that reported by Kasuga et
al. [17,18], we found that the electron diffraction patterns cannot
be assigned to rutile or anatse TiO
2
, but be assigned to titanate
(H
2
Ti
3
O
7
). Fig. 1e shows HRTEM images of the sample (d).
The HRTEM images clearly show that (1) the tubular structures
are well crystalline tubes with multiple shells, with an inner shell
diameter of about 8.0 nm, a shell spacing of about 0.75 nm and
an average tube diameter of about 12.0 nm; (2) the structures of
different shells are well correlated; (3) the tubes are open ended.
Further investigations showed that adjusting hydrothermal
reaction time could control the amount of rutile nanocrystals in
the nanocomposites. Fig. 2 shows the XRD patterns of the start-
ing material and the products. It can be seen that when reaction
time reaches 48 h, the diffraction peaks of titanate nanotubes
appear [20,26,27]. With increasing reaction time, the peaks of
rutile disappeared steadily and the intensity of the diffraction
peak of titanate enhanced. At 144 h, all rutile phases were com-
pletely turned into titanate nanotubes. Fig. 2d is an XRD profile
taken from the products obtained at 140
◦
C for 144 h, showing
that the phase structure of the nanotubes agreed with neither

nanotubes instead of
TiO
2
, and we expected that the oxygen composition deviation
from TiO
2
might play an important role in the formation of our
nanotubes. The similar results were also obtained for the nan-
otubes obtained at 140
◦
C for 48 and 144 h. Energy-dispersive
X-ray (EDX) analysis also showed that there was no sodium in
the resulting product (as shown in Fig. 4). The yield and purity
of the nanocomposites or nanotubes are estimated to be higher
than 95 and 90%, respectively, based on the TEM, XRD, XPS
and EDX results.
The tube-like structures of the products were further exam-
ined using BET analysis, FTIR, UV–vis and Laser Raman spec-
tra. Table 1 shows effect of reaction time on BET specific surface
areas and pore parameters of the products. It could be seen that
with increasing reaction time, the specific surface areas, porosity
and pore volume of the tubular materials gradually increased,
which was ascribed to the fact that rutile particles in size of
50–300 nm were steadily turned into the tubular nanocompos-
ites, finally completely formed titanate nanotubes. The pore size
of the samples was about 8–10 nm and almost kept the same
due to the diameter of the tubular materials having no obvious
change.
Fig. 5 shows the FTIR spectra of the starting material and
the product prepared at different reaction time. There is a large

Pore size
d
(nm)
0 2.9 1.8 0.005 6.6
24 29.9 22.1 0.061 7.9
48 81.4 42.1 0.196 9.6
96 154.0 59.7 0.400 10.4
144 244.5 66.7 0.542 8.9
a
BET surface area calculated from the linear part of the BET plot
(P/P
0
= 0.05 − 0.3).
b
The porosity is estimated from the pore volume determined using the adsorp-
tion branch of the N
2
isotherm curve at the P/P
0
= 0.995 single point.
c
Total pore volume, taken from the volume of N
2
adsorbed at P/P
0
= 0.995.
d
Average pore diameter,estimated using the adsorption branch of the isotherm
and the Barrett–Joyner–Halenda (BJH) formula.
at 3400 cm

directed. Since the raw materials used in our synthesis are oxides
and NaOH, it is possible that the nanocomposite structures
are formed by a simple reaction-crystallization process (RC)
[5], in which bulky TiO
2
particles gradually react with NaOH
to form water soluble Na
2
Ti
3
O
7
in solution under hydrother-
mal treatment. Na
2
Ti
3
O
7
is then turned into H
2
Ti
3
O
7
via acid
treatment. The unreacted TiO
2
particles serve as the sites for
the heterogeneous nucleation of the titanate nanotubes, which

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