10.1007_s11082-015-0120-7

1 23
Optical and Quantum Electronics
ISSN 0306-8919
Opt Quant Electron
DOI 10.1007/s11082-015-0120-7
Optical and structural properties of
nanocrystalline anatase powders doped by
Zr, Si and Cu at high temperature
Nasrollah Najibi Ilkhechi, Ali Ahmadi &
Behzad Koozegar Kaleji

1 23
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Opt Quant Electron
DOI 10.1007/s11082-015-0120-7
Optical and structural properties of nanocrystalline
anatase powders doped by Zr, Si and Cu at high
temperature
Nasrollah Najibi Ilkhechi · Ali Ahmadi ·
Behzad Koozegar Kaleji
Received: 10 July 2014 / Accepted: 14 January 2015
© Springer Science+Business Media New York 2015
Abstract In this study, preparation of 20mol% Si, 15mol% Zr and 5mol% Cu doped TiO2
nanopowders via sol–gel process have been investigated. The effects of Si, Zr and Cu doping
and calcinations temperature (500–1,000◦C) on the structural, and photocatalytic properties
of titania nanopowders studied by X-ray diffraction (XRD), scanning electron microscope
(SEM-EDX), transmission electron microscope and UV–Vis absorption spectroscope. XRD
patterns showed peak of the cristobalite phase at temperature 900 and 1,000◦C. Also, XRD
results suggest that adding dopants has a signiﬁcant effect on anatase phase stability, crys-
tallinity, and particle size of TiO2. Titania rutile phase formation in system (Ti–Si–Zr–Cu) was
inhibited by Zr+4 and Si+4 at temperature 500–700◦C and promoted by Cu+2 doped TiO2 in
high temperatures (800–1,000◦C), so that 41 and 15% anatase composition is retained even
after calcination at 800, 900◦C respectively. The photocatalytic activity was evaluated by
photocatalytic degradation kinetics of aqueous methyl orange (MO) under visible radiation.
The degradation efﬁciency of MO reaches 85% of the doped samples after 40min of visible
light irradiation at temperature 700 ◦C.
Keywords Optical materials · Sol–gel growth · X-ray diffraction · Optical properties
1 Introduction
Titania (TiO2) crystallizes in three phases: Brookite (rhombohedral, a=5.43Å; b=9.16Å;
c=5.13Å), Anatase (tetragonal, a=b=3.78Å; c=9.50Å), and Rutile (tetragonal
N. N. Ilkhechi (B) · B. K. Kaleji
Department of Materials Engineering, Faculty of Engineering, Malayer University,
P.O. Box 65719-95863, Malayer, Iran
e-mail: nasernajibi@gmail.com
B. K. Kaleji
e-mail: b.kaleji@malayeru.ac.ir
A. Ahmadi
Materials Research School, P.O. Box 31485-498, Isfahan, Iran
123
Author's personal copy

N. N. Ilkhechi et al.
a=b=4.58Å; c=2.95Å). The Brookite and Anatase crystalline phases, which are stable
at low temperatures, transform into Rutile by calcination at higher temperatures. However,
Brookite and Anatase can be stabilized at high temperatures in presence of dopants during
synthesis which inhibits their transformation into Rutile (Gopal et al. 1997; Mark et al. 1983;
Weast 1984; Kostov 1973).
The titanium dioxide has been widely used in the field of pollutant degradation and envi-
ronment protection since photocatalytic function of titania was discovered in 1972 (Fujishima
and Honda 1972). The titanium dioxide has the advantage of not only high photocatalytic
activity, but also good acid resistance, low cost, and no toxicity, which makes the titanium
dioxide become one of the best photocatalytic agents (Wang et al. 1997; Palmer and Eggins
2002). TiO2 can catalytically decompose a large number of organic and inorganic pollutants
under illumination of visible light (Hoffmann et al. 1995; Ohko et al. 1998; Hermann 1999).
However, depending on the structural form, the photocatalytic activity of TiO2 has been
found to vary. As known, anatase or the mixture phase of anatase and rutile show the highest
photocatalytic activity Nakamura et al. (2005). Anatase with large surface area, high crys-
tallinity and nanoscaled crystallite size exhibits a high photocatalytic activity. Many studies
have focused on doping metal oxides such as Fe2O3, SiO2, SnO2, Nb2O5, ZrO2CuO and
other oxides (Feng et al. 2004; Ismail 2005; Yu et al. 2002; Guan 2005; Ying and Chang
2006; Hong et al. 2003; Awate et al. 2005; Jung and Park 2004; Wu et al. 2005; Navio et al.
2001; Subramanian et al. 2001; Rajeshwar et al. 2001).
ZrO2 and ZrO2–TiO2 binary oxides catalysts have been investigated for their catalytic
properties with organic compounds, especially for degradation reactions in environmental
remediation (Vishwanathan et al. 2004; Chary et al. 2005; Fu et al. 1996). however, more
information on the mechanisms behind the reactions, especially their photocatalytic proper-
ties, are necessary to improve efficiency. ZrO2 has been used not only as a support for TiO2
but also with TiO2 as a binary oxide catalyst since ZrO2 itself can act as a photocatalyst. It has
been reported that the addition of small amounts of ZrO2 into TiO2 prevent transformation
of anatase to rutile (Cao et al. 2009; Kim et al. 2001; Yang and Ferreira 1998).
It has been found that Si-doping into TiO2 could obviously enhance thermal stability
anatase at high temperature, enlarge surface area and enhance visible light photoactivity of
TiO2 (Ismail and Matsunaga 2007; Xie et al. 2004; Li et al. 2005a,b; Xie et al. 2006; Okada
et al. 2001; Kim et al. 2001; Zhang and Reller 2002; Akhtar et al. 1992). Sikong et al. (2008)
reported that the addition of SiO2 seems to exhibit a higher photocatalytic activity than pure
TiO2, because of a large surface area effect.
Sensitization of Cu doped TiO2 with eosin improved the photocatalytic activity under
visible light irradiation and also promoted the transformation of anatase to rutile (Jin et al.
2007; You et al. 2009; Shannon and Pask 1965; Iida and Ozaki 1961). Hussain et al. (2012)
reported that copper loaded Si–TiO2 photocatalyst showed high specific area, small crystallite
size, narrow band gap which contribute to their high photocatalytic activity.
But, few papers are dedicated to the investigation of Si/Zr doped titania nanopowders
as photocatalysts (Reddya et al. 2001; Wellbrock et al. 1992; Mountjoy et al. 2003). In our
previous research, we studied the effect of doping Si (up to 20mol%) and Zr (up to 20mol%)
on photocatalytic behavior of titania based nanopowders at high temperature. We found
that 20% of Si and 15mol% Zr shows the most significant improvement on photocatalytic
behavior of TiO2 under visible irradiation and also, we could stability of anatase phase up to
1,000◦C (Najibi Ilkhechi and Koozegar-Kaleji 2014).
Although there are some researches on doping titania with copper, triple doping of titania
is a novel approach. Also, we tried higher temperatures near 1,000◦C which is not reported
before.
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Optical and structural properties of nanocrystalline anatase powders
Inthispaper,TiO2 nanopowders,dopedbySi,ZrandCu,werepreparedbysol–gelmethod.
The effect of the dopant cations on the stability of anatase phase and optical properties in high
temperature was studied. The efficiency of these samples as photocatalysts for degradation
of methyl orange (MO), as organic compound model, under visible light was investigated.
2 Experimental procedures
2.1 Preparation of the nanopowders
The preparation of precursor solution for Zr, Si and Cu doped TiO2 nanopowder is described
as follows: TiO2, ZrO2, SiO2 and CuO sols were prepared, separately. titanium (IV) butoxide
(TBT = Ti(OC4H9)4, Aldrich) was selected as titanium source. 10 ml of ethanol (EtOH,
Merck) and 4ml of ethyl acetoacetate, which is as a sol stabilizer, were mixed, and then 4 ml
of TBT was added by the rate of 1 ml/min to the mixture at the ambient temperature (25 ◦C).
The solution was continuously stirred for 1 h, followed by dropping of HNO3 as catalyst to
the solution. Deionized water was added to the solution slowly to initiate hydrolysis process.
Solution was aged for 24 h in order to complete all reactions. The chemical composition of
the alkoxide solution was TBT:H2O:HNO3:EAcAc:EtOH = 1:8:3:0.05:5 in volume ratio. In
order to prepare ZrO2 sol, SiO2 and CuO sol, zirconyl nitrate hydrate (ZrO(NO3) · 2H2O,
Aldrich), tetraethoxysilane (Si(OC2H5)4, Aldrich) and (Cu(NO3)2 · 3H2O, Merck) were
dissolved in EtOH with volume ratio of ZrO(NO3) · 2H2O:EtOH = 1:20, Si(OC2H5)4:EtOH
= 2:13 and Cu(NO3)2 ·3H2O:EtOH= 1:6 at ambient temperature with continuous stirring. Si
was doped 10 min after Zr doping under continuous stirring at room temperature for 30min
and followed by slow dropping of CuO sol. The formed gel was dried at 100 ◦C for 60 min.
Finally, the prepared samples were calcined at desired temperatures (500, 600,700, 800, 900,
1,000◦C) for 2 h.
2.2 Characterization methods
Samples were recorded using X-ray diffraction analysis (Philips, MPD-XPERT, λ : Cu Kα =
0.154 nm). The samples were scanned in the 2θ ranging of 20◦–70◦. The average crystallite
size of nanopowders (d) was determined from the XRD patterns, according to the Scherrer
equation (Najibi Ilkhechi and Koozegar-Kaleji 2014)
d = kλ/β cos θ (1)
where k is a constant (shape factor, about 0.9), λ the X-ray wavelength (0.154 nm), β the full
width at half maximum (FWHM) of the diffraction peak, and θ is the diffraction angle. The
values of β and θ of anatase and rutile phases were taken from anatase (1 0 1) and rutile (1 1 0)
planes diffraction lines, respectively. The amount of rutile in the samples was calculated using
the following equation (Najibi Ilkhechi and Koozegar-Kaleji 2014)
XR = (1 + 0.8 (IA/IR))−1
(2)
where XR is the mass fraction of rutile in the samples, and IA and IR are the X-ray integrated
intensities of (1 0 1) reflection of the anatase and (1 1 0) reflection of rutile, respectively. The
diffraction peaks of crystal planes (101), (200), and (105) of anatase phase in XRD patterns
were selected to determine the lattice parameters of the TiO2 and doped TiO2 nanopowders.
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The lattice parameters were obtained by using the Eq. 3 (Najibi Ilkhechi and Koozegar-Kaleji
2014)
(Bragg s law) : 2d(h kl) sin θ = λ
(1/dh k l)2
= (h/a)2
+ (k/b)2
+ (l/c)2
(3)
where d(hkl) is the distance between the crystal planes of (h k l); λ is the wavelength of X-ray
used in the experiment; θ is the diffraction angle of the crystal plane (h k l); h k l is the crystal
plane index; and a, b, and c are lattice parameters (in anatase form, a = b = c).
Morphology of the nanopowder was observed using scanning electron microscope (SEM,
XL30 Series) with an accelerating voltage of 10–30 kV. TEM imaging was carried out using
Zeiss-EM10C-80 kV instrument.
Nitrogen adsorption isotherms were measured at 77 K using a N2 adsorption analyzer
(Micromeritics, ASAP 2020). The Brunauer, Emmett, and Teller (BET) model was used to
estimate the surface area of the samples according to the N2 adsorption data.
2.3 Photocatalytic activity measurement
The photocatalytic activity was evaluated by monitoring the degradation of MO solution
under visible illumination. In each experiment, 0.08 g standard sample calcined at different
temperatures was dispersed in 50 mL of MO solutions with concentration of 5 × 10−6 M. A
150W lamp was used as the light source. Before the test, all powders containing MO solutions
were magnetically stirred in dark for 1 h to establish the adsorption–desorption equilibrium.
Then, the solutions were irradiated under visible light with constant stirring rate of 450 rpm.
After 40 min of irradiation, 5 ml of supernatants were taken from the suspension by a syringe
ﬁlter unit to scan the UV–Vis absorption spectrum. The UV–Vis absorption spectra of samples
were measured between 200 and 700 nm UV–Vis spectrophotometer. The extent of the MO
decomposition was determined by measuring the value of the absorbance value at 478 nm
(max absorption of methyl orange) using a UV–Vis spectrometer. The degradation rate [η
(%)] of MO was calculated by the following formula:
η(%) = (A0 − At) /A0 × 100 (4)
where A0 and At represent the initial equilibrium concentration and reaction concentration
of reactant at 478 nm, respectively (Najibi Ilkhechi and Koozegar-Kaleji 2014).
3 Results and discussion
3.1 X-ray diffraction studies of the nanopowders
Figure 1 shows the XRD patterns of TiO2 (T), T–20%Si–15%Zr (TSZ) and T–20%Si–
15%Zr–5%Cu (TSZC) samples calcined at 500 ◦C for 2 h. According to the XRD patterns,
the pure (T) and doped TiO2 were crystallized in anatase phase and there are no other
characterization peaks of impurities in samples within the detection of X-ray diffractometery.
By comparing the relative intensity of the diffraction peaks, it can be seen that the intensity of
(101) plane decreased and the peak position (2θ) is decreased after doping which indicates
that dopant cations are successfully doped into TiO2 crystal lattice. In general, the ionic
radius and calcining temperature are two of the most important variables, which can strongly
inﬂuence the ability of the dopant to enter into TiO2 crystal lattice and form stable solid
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Fig. 1 XRD spectra of the pure
and doping TiO2 nanopowders at
500 ◦C. a T, b TSZ, c TSZC
Table 1 Characterization of pure and doped TiO2 (TSZ, TSZC) at temperature 500 ◦C
Sample A (%) R (%) Crystallite
size (nm)
a=b (Å) c (Å) Cell volume
(Å)3
BET
m2/g
dA dR
TiO2 100 – 9.47 – 3.798 8.944 126.357 183.2
T–20%Si–15%Zr 100 – 5.63 – 3.734 11.180 155.880 308.1
T–20%Si–15%Zr–5%Cu 100 – 7.45 – 3.821 10.163 141.380 206.5
solutions. If the ionic radius of the dopant is much bigger or smaller than that of Ti4+, the
dopant substituting with Ti in TiO2 crystal lattice ions results into crystal lattice distortion
(CLD). Thus, certain amount of energies can be accumulated and led the substitution process
to be suppressed. The calculated crystallite size and lattice parameter of anatase, calculated
by scherrer formula, are reported in Table 1. Based on the Table 1, average crystallite size
and lattice parameters are related to different cation dopants. It clearly shows that the average
crystallite size is decreased from 9.47 to 7.45 nm by the addition of Si, Zr and Cu dopant,
where as makeable decrease is observed from 9.47 to 5.63 nm by adding Si and Zr co dopants.
The decrease in crystallite size can be attributed to the presence of Si–O–Ti, Zr–O–Ti, and
Cu–O–Ti in the Si, Zr and Cu doped TiO2 nanopowders which inhibits the growth of crystal
grains (Mountjoy et al. 2003; Maria Suzana et al. 2002). The Zr4+ radius (0.72 Å, CN: 6)
is slightly bigger than Ti4+ radius (0.6 Å, CN: 6) but Si+4 radius (0.4 Å, CN: 6) and Cu+2
(0.57 Å, CN: 4) radius are smaller than Ti+4 and both factors could led to slight induced
stress in TiO2 lattice (Shannon 1976). Thus, the c lattice parameters increase relative to that
of TiO2. Based on the data in Table 1, surface area of the Si and Zr co-doped nanopowders is
higher than Si, Zr and Cu doped TiO2. The surface area of pure and doped TiO2 were found
to be 183.2, 206.5 and 308.1 m2/g for the T, TSZC and TSZ samples, respectively.
The XRD patterns of 20%Si, 15%Zr and 5%Cu doped TiO2 nanopowders calcined at
different temperatures are shown in Fig. 2. The intensity of crystalline peaks increases with
123

Fig. 2 XRD spectra of the
T–20%Si–15%Zr–5% Cu
(TSZC) nanopowders calcined at
different temperatures. a 600 ◦C,
b 700 ◦C, c 800 ◦C, d 900 ◦C,
e 1,000◦C
the increase in temperature indicating the improvement in the crystallinity of samples. Simul-
taneously, the peaks became narrower as the temperature was increased showing the increase
in crystallite size. No other impurity peak was observed in the XRD patterns which indicates
the single phase formation of anatase nanoparticles up to 700 ◦C, which transforms to rutile
phase at 800–1,000◦C. At 800 and 900 ◦C the percent of rutile phase was 59 and 85%,
respectively. The sample heated at 1,000◦C showed only rutile phase. Result show that,the
cristoballite phase in nanocompisite at higher calcinations temperature (900–1,000◦C) but
for Zr–Si co-doped TiO2, there were no obvious XRD peaks of cristoballite (Najibi Ilkhechi
and Koozegar-Kaleji 2014). The existence of cristoballite in XRD patterns is clearly proven
from the presence of the (1 1 1) peak at 2θ = 21.98◦. It can be seen that the characteristic
peaks of cristoballite became stronger and more intense with increasing calcination temper-
ature. The results showed that the addition of Cu into T–20%Si–15%Zr has a promoting
effect on anatase to rutile crystalline phase transformation at temperature of 700 ◦C (Najibi
Ilkhechi and Koozegar-Kaleji 2014; Mountjoy et al. 2003; Maria Suzana et al. 2002). Crystal-
lite size, lattice parameters and cell volume at different heating temperatures are mentioned
in Table 2. It is clear that the crystallite size was increased but the lattice parameters, cell vol-
ume, and surface area has decreased with increase the calcination temperatures for anatase
(600, 700◦C) and rutile (800–1,000◦C) nanoparticles. The crystallite size of the anatase
increased from 7.45 to 12.90 nm when the temperature was raised to 600 ◦C. As the temper-
ature increased from 500–900◦C, the crystallite size of the powder greatly increased up to
∼44.37nm. Table 2 shows that after calcination of the T–20%Si–15%Zr–5%Cu (TSZC)
sample at 600–1,000◦C, a minimum surface area of 41.7 m2/g was measured. It is com-
mon that the surface area decreases at elevating temperatures. With increasing temperature,
the particles are simply growing to reduce their free energy (i.e. maximizing the volume to
surface ratio). They may also shift from being more amorphous to more crystalline in the
process. Due to above reason, leading to a decrease in surface area.
3.2 UV–Vis absorbtion
To indicate the photocatalytic activities of the pure and doped TiO2 nanoparticles for the
degradation of the organic pollutants, the photocatalytic degradation of MO solution were
123

Table 2 Characterization of doped TiO2 (TSZC) at different temperature
Calcination
temperature
A (%) R (%) Crystallite
size (nm)
a=b (Å) c (Å) Cell volume
(Å)3
BET
m2/g
dA dR
500 ◦C 100 – 7.45 – 3.821 10.163 141.380 206.5
600 ◦C 100 – 12.90 – 3.877 8.915 134.002 119.2
700 ◦C 100 – 21.20 – 3.822 8.873 129.613 72.5
800 ◦C 41 59 23.37 22.99 4.463 2.981 64.013 63.8
900 ◦C 15 85 44.37 23.38 4.615 2.969 63.127 61.3
1,000◦C 0 100 – 33.95 4.318 3.083 57.482 41.7
Fig. 3 The absorption spectra of
TiO2 (T), T–20%Si–
15%Zr (TSZ)
and T–20%Si–15%Zr–5%Cu
(TSZC) nanopowders calcined at
500 ◦C
carried out. Figure 3 shows that the absorption spectra of the T, TSZ and TSZC calcined at
500 ◦C. According to Fig. 3, the absorbtion edge extended towards larger wavelengths, and
the photocatalytic activity was enhanced by doping under visible light.
TiO2 presented poor activity for the degradation of MO under visible light irradiation,
which the degradation ratio was less than 26% (Fig. 4). Approximately 70% of MO is
degraded after 40 min irradiation in the presence of T–20%Si–15%Zr, while 75% of MO
is degraded by 20%Si,15%Zr and 5%Cu doped TiO2 at 500 ◦C (Fig. 4).
The Si, Zr and Cu doped TiO2 has shown considerable shift in the absorption peak towards
the larger wavelengths .The extension of adsorption edge to longer wavelengths for doped
TiO2 indicates promotes the photocatalytic activity of catalysts.
Figure 5 shows the absorption spectra in the wavelength range of 280–800nm of doped
TiO2 (TSZC) nanopowders calcined at different temperatures for 2 h. It can be seen that
the enhancement in optical absorption was indicated after the calcinations at 700 ◦C. The
increase in photocatalytic activity is due to the formation of anatase and the crystallization
improvement of anatase phase. At higher calcination temperatures the photocatalytic activity
decreased, that is due to the following factors. First, according to XRD results, the phase
transformation of anatase to rutile occurred at about 800 ◦C and the sample is mainly com-
posed of rutile. Second, the sintering and growth of TiO2 crystallites result in the signiﬁcant
decrease of surface area of the TiO2 nanopowders.
Also, the phase transformation from anatase to rutile further accelerates the growth of
crystallites by providing the heat of phase transformation. These causes may result in the
123

Fig. 4 Photocatalytic degradation of MO determined by pure and doped TiO2 nanopowders after 40min
visible irradiation
Fig. 5 The absorption spectra of
T–20%Si–15%Zr–5%Cu
(TCSZ) nanopowders calcined at
different temperatures
rapid decrease in photocatalytic activity. Results show that photocatalytic activity of TSZC is
higher than that of TSZ at even higher calcination temperature (Najibi Ilkhechi and Koozegar-
Kaleji 2014).
In general a key factor in titania’s photocatalytic ability is its high surface area, the same
property that contributes to its optical properties. A high surface area leads to a higher density
of localized states, which involve electrons with energies between the conduction band and
valence band. Despite the larger experimental band gap of 3.2 eV for anatase, compared with
3.0 eV for rutile, the photocatalytic performance of anatase is generally considered superior
to that of the more stable rutile. This is attributed to a higher density of localised states and
consequent surface-adsorbed hydroxyl radicals and slower charge carrier recombination in
anatase relative to rutile (Mountjoy et al. 2003). All these factors contribute to enhancing the
photocatalytic activity.
123

Fig. 6 SEM-EDX images of pure and doped TiO2 (TSZC) nanopowders prepared by sol–gel process via
calcinations at 500 ◦C. a Pure TiO2, b doped TiO2 and c EDX spectra of TSZC nanopowders
3.3 SEM-EDX and TEM analysis of pure and doped TiO2 nanopowders
The surface morphological study of the TiO2 photocatalyst was carried out using SEM
images. Figure 6 shows the SEM images of pure and doped TiO2 nanoparticles. It can be
seen that the aggregated packing of doped TiO2 nanoparticles was formed at 500 ◦C. It can
be seen from Fig. 6b that the doped TiO2 calcined at 500 ◦C have slightly lower particles size
than pure TiO2 (Fig. 6a). Also, this image shows the uniform particles which are agglomerated
together. It can be clearly seen that the microstructures of the powders are strongly affected
by doping and calcination temperatures which is due to aggregation of particle size (Najibi
Ilkhechi and Koozegar-Kaleji 2014). The EDX data of doped TiO2 in Fig. 6c shows two
peaks around 4.5 keV. The intense peaks are assigned to the bulk TiO2 and the less intense
one to the surface TiO2. The peaks of Si, Zr and Cu are distinct in Fig. 6 at 0–2keV. The less
intense peak is assigned to dopant in the TiO2 lattices. These results conﬁrmed the existence
of cations in of the solid catalysts.
Figure 7 shows the TEM micrographs of pure and doped TiO2 particles calcined at 500 and
700 ◦C, respectively. As see the pure TiO2 particles appeared as uniform and agglomerated
123

Fig. 7 TEM micrograph of T and TSZC calcined at 500 and 700 ◦C. a T—500 ◦C, b TSZC—500 ◦C,
c TSZC—700 ◦C
shapes but doped TiO2 shows sphere shaped structure with the average particle size of about
≤80 and ≤140 nm for calcined samples at 500 and 700 ◦C, respectively. This indicates that
doping could inhibit the increase of TiO2 particle size.
In Fig. 7 the Selected Area Electron Diffraction (SAED) pattern of pure and doped TiO2
calcined at 500 and 700 ◦C is shown. The SAED pattern (Fig. 7a) shows spotted sharp and
continuous rings typically exhibited by polycrystalline grains. Five rings were indexed as
[101], [200], [004], [105], [204] planes, which matches well with the reported values for
anatase phase (Maria Suzana et al. 2002). Presence of clear diffraction spots after calcination
of doped TiO2 nanoparticles reveals the improvement of crystallinity at 700 ◦C (Fig. 7b, c).
4 Conclusions
This study focused on the effects of calcination temperature and Si, Zr and Cu dopants on
phase transformation, crystallite size, and photocatalytic activity of Titania nanopowders.
The nanopowders were prepared from precursor solutions via sol–gel method and calci-
nations at temperature range of 500–1,000◦C. The crystal phases and crystallite sizes of
the synthesized nanopowders largely depend on the calcination temperature. The anatase to
rutile phase transformation was inhibited by Si4+ and Zr+4 doping but promoted by Cu+2
doping. Crystalline anatase single phase was found at a calcination temperature range 500–
123

700◦C and mixed phases of anatase and rutile were formed at a calcinations temperature
range 800–900◦C. Crystallite size of pure TiO2 tends to increase at higher calcination tem-
peratures. Doping Si, Zr and Cu in TiO2 was effective on crystal phases the nanopowders.
Photocatalytic activity of TiO2 is greatly influenced by its crystallinity, grain size, surface
areas, and surface hydroxyl content. Si, Zr and Cu inhibited the growth of crystallite size of
anatase and the amorphous anatase transformation as well as the subsequent anatase–rutile
transformation. The calcinations of sample at 700 ◦C seen to exhibit a higher photocatalytic
activity than TiO2 because of larger surface area.
References
Akhtar, M.K., Pratsinis, S.E., Mastrangelo, S.V.R.: Dopants in vapor phase synthesis of titania powders. J.
Am. Ceram. Soc. 75, 3408–3416 (1992)
Awate, S.V., Jacob, N.E., Deshpande, S.S., Gaydhankar, T.R., Belhekar, A.A.: Synthesis, characterization and
photocatalytic degradation of aqueous eosin over Cr containing Ti/MCM-41 and SiO2 − TiO2 catalysts
using visible light. J. Mol. Catal. A Chem. 226, 149–154 (2005)
Cao, S., Yeung, K.L., Kwan, J.K.C., To, P.M.T., Yu, S.C.T.: An investigation of the performance of catalytic
aerogel filters. J. Appl. Catal. B 86, 127–136 (2009)
Chary, K.V.R., Sagar, G.V., Naresh, N., Seela, K.K., Sridhar, B.: Characterization and reactivity of copper
oxide catalysts supported on TiO2 − ZrO2. J. Phys. Chem. B 109, 9437–9444 (2005)
Feng, J., Wong, R., Hu, X., Yue, P.: Discoloration and mineralization of Orange II by using Fe3+-doped TiO2
and bentonite clay-based Fe nanocatalysts. Catal. Today 98, 441–446 (2004)
Fu, X., Clark, L.A., Yang, Q., Anderson, M.A.: The enhanced photocatalytic performance of titania-based
binary metal oxides: TiO2/SiO2, TiO2/ZrO2. Environ. Sci. Technol. 30, 647–653 (1996)
Fujishima, A., Honda, K.: Electrochemical photolysis of water at a semiconductor electrode. Nature 238,
37–38 (1972)
Gopal, M., Chan, W., Jonghe, L.: Room temperature synthesis of crystalline metal oxides. J. Mater. Sci. 32,
6001–6008 (1997)
Guan, K.: Relationship between photocatalytic activity, hydrophilicity and self-cleaning effect of TiO2/SiO2
films. Surf. Coat. Technol. 191, 155–160 (2005)
Hermann, J.M.: Heterogeneous photocatalysis: fundamentals and applications to the removal of various types
of aqueous pollutants. Catal. Today 53, 115–129 (1999)
Hoffmann, M.R., Martin, S.T., Choi, W., Bahnemann, D.W.: Environmental applications of semiconductor
photocatalysis. Chem. Rev. 95, 69–96 (1995)
Hong, S.S., Lee, M., Park, S., Lee, G.: Synthesis of TiO2/SiO2 nanoparticles in a water-in-carbon-dioxide
microemulsion and their photocatalytic activity. Res. Chem. Intermed. 31, 379–389 (2003)
Hussain, S.T., Mazhar, M., Siddiqa, A., Javid, H., Siddiq, M.: Cu–S codoped TiO2 nanophotocatalyst for the
degradation of environmental and industrial pollutants. Catal. J. 5, 21–30 (2012)
Iida, Y., Ozaki, S.: Grain growth and phase transformation of titanium oxide during calcination. J. Am. Ceram.
Soc. 44, 120–127 (1961)
Ismail, A.A.: Synthesis and characterization of Y2O3/Fe2O3/TiO2 nanoparticles by sol-gel method. Appl.
Catal. B Environ. 58, 115–121 (2005)
Ismail, A.A., Matsunaga, H.: Influence of vanadia content onto TiO2−SiO2 matrix for photocatalytic oxidation
of trichloroethylene. Chem. Phys. Lett. 447, 74–78 (2007)
Jin, Z., Zhang, X., Li, Y., Li, S., Lu, G.: Apparent quantum efficiency for stable hydrogen generation over
eosin-sensitized CuO/TiO2 phocatalyst undervisible light irradiation. Catal. Commun. 8, 1267–1273
(2007)
Jung, K.Y., Park, S.B.: Photoactivity of SiO2/TiO2 and ZrO2/TiO2 mixed oxides prepared by sol-gel method.
Mater. Lett. 58, 2897–2900 (2004)
Kim, J., Song, K.C., Foncillas, S., Pratsinis, S.: Dopants for synthesis of stable bimodally porous titania. J.
Eur. Ceram. Soc. 21, 2863–2874 (2001)
Kostov, I.: Minerology, 3rd edn. Nauka, Izkustia, Sofia (1973)
Li, Z.J., Hou, B., Xu, Y., Wu, D., Sun, Y.H.: Hydrothermal synthesis, characterization, and photocatalytic
performance of silica-modified titanium dioxide nanoparticles. J. Colloid Interface Sci. 288, 149–154
(2005)
Li, Z.J., Hou, B., Xu, Y., Wu, D., Sun, Y.H., Hu, W., Deng, F.: Comparative study of sol–gel-hydrothermal and
sol–gel synthesis of titania–silica composite nanoparticles. J. Solid State Chem. 178, 1395–1405 (2005)
123

Maria Suzana, P., Francisco, R., Valmor, R.: Inhibition of the anatase–rutile phase transformation with addition
of CeO2 to CuO–TiO2 system: Raman spectroscopy, X-ray diffraction, and textural studies. Chem. Mater.
14, 2514–2518 (2002)
Mark, H.F., Othmer, D.F., Overberger, C.G., Seaberg, G.T.: Encyclopedia of Chemical Technology, vol. 23.
Wiley, New York (1983)
Mountjoy, G., Holland, M.A., Wallidge, G.W., Gunawidjaja, P., Smith, M.A., Pickup, D.M., Newport, R.J.:
Structural characterisation of mixed (TiO2)x(ZrO2)y(SiO2)1−x−y sol–gels (0.05 £ x, y £ 0.15) using a
combination of X-ray and spectroscopy techniques. J. Phys. Chem. B 107, 7557–7566 (2003)
Najibi Ilkhechi, N., Koozegar-Kaleji, B.: High temperature stability and photocatalytic activity of nanocrys-
talline anatase powders with Zr and Si co-dopants. J. Sol-Gel Sci. Technol. 69, 351–356 (2014)
Nakamura, T., Ichitsubo, T., Matsubara, E., Muramatsu, A., Sato, N., Takahashi, H.: On the preferential
formation of anatase in amorphous titanium-oxide film. Scr. Mater. 53, 1019–1023 (2005)
Navio, J.A., Hidalgo, M.C., Colon, G., Botta, S.G., Litter, M.I.: Preparation and physicochemical properties
of ZrO2 and Fe/ZrO2 prepared by a sol–gel technique. Langmuir 17, 202–210 (2001)
Ohko, Y., Fujishima, A., Hashimoto, K.: Kinetic analysis of the photocatalytic degradation of gas phase 2-
propanol under mass transport-limited condition with a TiO2 film photocatalyst. J. Phys. Chem. B 102,
1724–1729 (1998)
Okada, K., Yamamoto, N., Kameshima, Y., Yasumori, A.: Effect of silica additive on the anatase to rutile
phase transition. J. Am. Ceram. Soc. 84, 1591–1596 (2001)
Palmer, F.L., Eggins, B.R.: The effect of operational parameters on the photocatalytic degradation of humic
acid. J. Photochem. Photobiol. 148, 137–143 (2002)
Rajeshwar, K., Tacconi, N.R., Chenthamarakshan, C.R.: Semiconductor-based composite materials: prepara-
tion, properties and performance. Chem. Mater. 13, 2765–2782 (2001)
Reddya, B.M., Chowdhury, B., Smirniotis, P.G.: An XPS study of the dispersion of MoO3 on TiO2–ZrO2,
TiO2–SiO2, TiO2–Al2O3, SiO2–ZrO2, and SiO2–TiO2–ZrO2 mixxed oxides. Appl. Catal. A Gen. 211,
19–30 (2001)
Shannon, R.D., Pask, J.A.: Kinetic of the anatase–rutile transformation. J. Am. Ceram. Soc. 48, 391–398
(1965)
Shannon, R.D.: Revised effective ionic radii and systematic studies of interatomic distances in halides and
chalcogenides. Acta Cryst. A 32, 751–767 (1976)
Sikong, L., Damchan, J., Kooptarnond, K., Niyomwas, S.: Effect of doped SiO2 and calcinations temperature
on phase transformation of TiO2 photocatalyst prepared by sol–gel method. J. Sci. Technol. 30, 385–391
(2008)
Subramanian, V., Wolf, E., Kamat, P.V.: Semiconductor-metal composite nanostructures. To what extent do
metal nanoparticles improve the photocatalytic activity of TiO2 films? J. Phys. Chem. B 105, 11439–
11446 (2001)
Vishwanathan, V., Roh, H.S., Kim, J.W., Jun, K.W.: Surface properties and catalytic activity of TiO2/ZrO2
mixed oxides in dehydration of methanol to dimethyl ether. Catal. Lett. 96, 23–28 (2004)
Wang, C.Y., Liu, C.Y., Shen, T.: The photocatalytic oxidation of phenylmercaptotetrazole in TiO2 dispersions.
J. Photochem. Photobiol. A Chem. 109, 65–70 (1997)
Weast, R.C.: Handbook of Chemistry and Physics. CRC Press, Boca Raton (1984)
Wellbrock, U., Beier, W., Frischat, C.H.: Preparation of SiO2–TiO2–ZrO2 gel glasses and coatings by means
of modified alkoxide solutions. J. Non-Cryst. Solids 147(148), 350–355 (1992)
Wu, C., Zhao, X., Ren, Y., Yue, Y., Hua, W., Cao, Y., Tang, Y., Gao, Z.: Gas-phase photo-oxidations of organic
compounds over different forms of zirconia. J. Mol. Catal. A 229, 233–239 (2005)
Xie, C., Xu, Z., Yang, Q.J., Xue, B.Y., Du, Y.G., Zhang, J.H.: Enhanced photocatalytic activity of titania–silica
mixed oxide prepared via basic hydrolyzation. Mater. Sci. Eng. B 112, 34–41 (2004)
Xie, C., Yang, Q.J., Xu, Z.L., Liu, X.G., Du, Y.G.: New route to synthesize highly active nanocrystalline
sulfated titania–silica: synergic effects between sulfate species and silica in enhancing the photocatalysis
efficiency. J. Phys. Chem. B 110, 8587–8592 (2006)
Yang, J., Ferreira, J.M.F.: On the titania phase transformation by zirconia additive in a sol–gel derived powder.
Mater. Res. Bull. 33(3), 389–394 (1998)
Ying, G., Chang, Y.: Role of moisture in adsorption, photocatalytic oxidation, and reemission of elemental
mercury on a SiO2 − TiO2 nanocomposite. Environ. Sci. Technol. 40, 6444–6448 (2006)
You, M., Kim, T.G., Sung, Y.M.: Synthesis of cu doped TiO2 nanorods with various aspect ratios and dopant
concentration. Cryst. Growth Des. 10(2), 983–987 (2009)
Yu, J., Yu, J.C., Zhao, X.: The effect of SiO2 addition on the grain size and photocatalytic activity of TiO2
thin films. J. Sol-Gel Sci. Technol. 24, 95–103 (2002)
Zhang, Y.H., Reller, A.: Phase transformation and grain growth of doped nanosized titania. Mater. Sci. Eng.
19, 323–326 (2002)
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