Fabrication of coupled twin-shaped hollow hemispherical calcium molybdate via a facile ultrasound-assisted approach

Article abstract of DOI:10.1039/c4ce02124j

Coupled twin-shaped hollow hemispherical calcium molybdate (CTHH-CaMoO₄) microstructures were successfully synthesized via a facile ultrasound-assisted template-free route in the presence of absolute ethanol and ethylenediaminetetraacetic acid (EDTA). The oriented attachment and subsequent Ostwald ripening mechanism were responsible for the formation of this novel architecture. This journal is

Full text of DOI:10.1039/c4ce02124j

CrystEngComm
View Article Online
View Journal | View Issue
COMMUNICATION
Fabrication of coupled twin-shaped hollow
hemispherical calcium molybdate via a facile
ultrasound-assisted approach†
Cite this: CrystEngComm, 2015, 17,
444
2
ac
*bc
*a
a
a
Received 23rd October 2014,
Accepted 13th February 2015
Yongfang Zhang, Limin Wang,
Deqing Chu, Hongming Sun, Aoxuan Wang,
b
a
a
a
Zhongchao Ma, Lufeng Yang, Yan Zhuang and Yuze Bai
DOI: 10.1039/c4ce02124j
www.rsc.org/crystengcomm
1
8
Coupled twin-shaped hollow hemispherical calcium molybdate
architectures. Therefore, hollow CaMoO4 microstructures
with reduced material consumption and enhanced perfor-
mance urgently need to be developed.
(
4
CTHH-CaMoO ) microstructures were successfully synthesized
via a facile ultrasound-assisted template-free route in the presence
of absolute ethanol and ethylenediaminetetraacetic acid (EDTA).
The oriented attachment and subsequent Ostwald ripening mech-
anism were responsible for the formation of this novel
architecture.
The sonochemical process has been proven to be an effec-
tive technique to obtain novel materials with unique mor-
phologies and properties.
methods, the sonochemical method is advantageous as it is
nonhazardous, clean, facile and rapid in reaction rate. So far,
the sonochemical method has been used to prepare numer-
ous hollow materials, including PbS, CdSe, MoS
to the mechanism, various known physical phenomena, such
as oriented attachment, corrosion-based inside-out evacua-
tion, Kirkendall effect, and Ostwald ripening, have been
employed in template-free fabrications of inorganic hollow
structures. Thereto, Ostwald ripening is a near-equilibrium
process of aging, redistribution, or coarsening of matter, in
which smaller or less dense particles in an aggregate dissolve
gradually, while larger or denser particles in the same aggre-
gate are growing to minimize surface energy.
In this paper, we took an environmentally friendly
ultrasound-assisted template-free approach at room tempera-
4
ture to synthesize well-defined CTHH-CaMoO architecture.
Compared with the reactions in pure water, synthesis of
micro/nanomaterials in an ethanol–water mixture was favor-
able for the solvent properties to be changed.
1
9–21
In contrast to other synthesis
It is well-known that properties of materials can be pro-
foundly affected by their morphologies, and the structure–
function relationship is the underlying motive for discovering
and fabricating novel structures. Recently, tremendous scien-
tific efforts have been devoted to the inorganic hollow micro/
22
23
24
2
,
etc. As
25
26
27
28
1–3
nanostructures owing to their higher specific surface area,
lower density, better permeability, and more widespread
applications in many fields compared with their entity coun-
terparts. CaMoO , as an important member of the metal
4
molybdate families, has promising applications in various
4
5
fields, such as electro-optical devices,
scintillators,
29
6
–8
photoluminescence and so forth. Up to now, different mor-
9
phologies of CaMoO
4
,
including nanoparticles, nano-
10,11
12
13
rods,
structures,
erythrocyte-like hierarchical nanostructures, have been suc-
microclews, notched microspheres, flower-like
1
4,15
16
persimmon-like micro/nanomaterials
and
1
7
1
4
cessfully fabricated by microemulsion, hydrothermal reac-
30,31
EDTA, as
6,12
11
tion,
template-based rheological phase reaction and so
32,33
the structure-directing agent,
also makes a significant
on. However, to the best of our knowledge, there are rare
reports about the fabrication of hollow CaMoO4
contribution to this unique CTHH-CaMoO4 morphology.
Time-dependent experiments were conducted to observe the
morphology evolution. Based on the experimental results, a
possible hollow structure formation mechanism related to
Ostwald ripening was proposed.
a
College of Environment and Chemical Engineering, Tianjin Polytechnic
University, Tianjin 300387, PR China. E-mail: dqingchu@163.com;
Fax: +86 22 83955762; Tel: +86 22 83955762
All chemicals were of analytical grade and used without
further purification. In a typical procedure, 1 mmol of cal-
b
College of Materials Science and Engineering, Tianjin Polytechnic University,
Tianjin 300387, PR China. E-mail: wanglimin@tjpu.edu.cn
2
cium chloride (CaCl ) and 0.02 mmol of EDTA were added
c
State Key Laboratory of Hollow-Fiber Membrane Materials and Membrane Pro-
into 20 mL of mixed solvent (the volume ratio of ethanol to
deionized water R = 1 : 1) to form solution A, which was
stirred at room temperature for 30 min to be fully homoge-
cesses, Tianjin 300387, PR China
†
Electronic supplementary information (ESI) available: The controlled
experiments, characterization explanations and Fig. S1 are presented as ESI. See
DOI: 10.1039/c4ce02124j
2 4
nized. Then 0.6 mmol of sodium molybdate IJNa MoO ) was
2444 | CrystEngComm, 2015, 17, 2444–2449
This journal is © The Royal Society of Chemistry 2015

View Article Online
CrystEngComm
Communication
added into another 20 mL of mixed solvent with the same
ratio to form solution B. Next, solution B was rapidly mixed
with solution A to form a turbid liquid, which was disposed
under continuous magnetic agitation for another 15 min.
After that, the resulting turbid liquid was treated by ultra-
sound irradiation at an ambient atmosphere for 30 min in an
ordinary ultrasonic cleaning bath. Finally, the obtained prod-
ucts were collected by centrifugation, washed several times
with deionized water and ethanol, and dried in vacuum at 60
°C for 12 h.
Fig. 1 presents scanning electron microscopy (SEM) and
X-ray diffraction (XRD) images of the as-prepared uniform
CTHH-CaMoO . A panoramic morphology of the product is
4
displayed in Fig. 1a, indicating that large scale coupled hemi-
spheres are achieved. A magnified SEM image showing a
closer observation of the microstructure is given in Fig. 1b,
which reveals that the detailed morphology of the CaMoO4
product is a well-defined coupled twin-shaped hollow hemi-
sphere with diameters in the range of 2–3 μm. Fig. 1c shows
an individual broken coupled hemisphere, and it can be seen
that the interior is hollow and the thickness of the shell is
Fig. 2 SEM images of the CaMoO4 samples produced with different
volume ratios of ethanol to deionized water (R = v/v): (a) R = 0; (b) R =
1/9; (c) R = 1/3; (d) R = 3.
from Fig. 2d that irregular nanorods assembled together
unorientedly with the volume ratio R = 3.
It is well known that solvent properties greatly influence
the solubility and transport behaviour of the reactant, and
will further influence the morphology of the product. With
the increase in ethanol amount in the mixed solvent, the
polarity of the solution decreases and the solubility of the
~
400 nm. The phase of the synthesized CaMoO microcrystals
4
was identified by XRD characterization. As shown in Fig. 1d,
all the diffraction peaks can be indexed to tetragonal CaMoO
4
1
6
(
JCPDS-ICDD card no. 7-212). No peaks of impurity are
detected in the XRD pattern, indicating the formation of pure
CaMoO under these experimental conditions.
3
0
2
reactant decreases similarly. In addition, the H O molecule
4
is small enough to be easily polarized, which can effectively
stabilize the ions in the solution, leading to the low reactivity
The volume ratio of ethanol to deionized water (R = v/v) in
the reaction solution is an important factor in determining
the structure and morphology of the final CaMoO samples.
4
3
1
of the reactant. It has been reported that the decreased sol-
vent polarity causes a decreased tendency of oriented attach-
3
4
In the absence of ethanol, flowerlike spheres (Fig. 2a) assem-
bled by nanoplates were obtained. When the volume ratio
was R = 1/9, messy spheres with a trace amount of flowerlike
spheres (Fig. 2b) were generated. As the volume ratio
increased to R = 1/3, aggregated microspheres with a diame-
ter of about 1.5 μm (Fig. 2c) were achieved. It can be seen
ment of the primary nanoparticles. Fig. 2a shows that with-
out ethanol, the polarity of the solvent is relatively high,
which gives the primary particles enough time to assemble
into regular nanoplates and the nanoplates assemble further
into flowerlike spheres. With the increased fraction of etha-
nol, the reactivity of the ions in the solution increases, so the
number of nucleation particles is larger and the reaction rate
is faster, which results in little time to age and aggregate the
particles in order and to generate the product with irregular
3
1
morphologies. In our experiments, different morphologies
of CaMoO products such as messy spheres in Fig. 2b, aggre-
4
gated microspheres in Fig. 2c, and finally irregular assembled
nanorods in Fig. 2d were obtained with increasing amount of
ethanol.
The presence of an appropriate amount of EDTA plays a
vital structure-directing role in the formation of this unique
4
CTHH-CaMoO architecture. It is obvious that with the
increasing addition of EDTA, the split degree of the crystals
3
5,36
increases (Fig. 3).
Controlled experiments showed that
without the addition of EDTA in the reaction system, peony-
shaped hierarchical architecture assembled by nanorods was
obtained, as shown in Fig. 3a and b. As the amount of EDTA
is 0.01 mmol, the outline of the product was coupled twin-
shaped as well as cauliflower-shaped hemispheres with rug-
ged surface (Fig. 3c), and the overall dispersity and unifor-
mity are poor. If the amount of EDTA increases to 0.04 mmol,
Fig. 1 SEM images and XRD pattern of the as-synthesized CTHH-
CaMoO
c) a close-up image of an individual CTHH-CaMoO
tive XRD pattern recorded for the CTHH-CaMoO
4
: (a) overall product morphology; (b) a magnified SEM image;
(
4
; (d) a representa-
4
.
This journal is © The Royal Society of Chemistry 2015
CrystEngComm, 2015, 17, 2444–2449 | 2445

View Article Online
Communication
CrystEngComm
coupled twin-shaped hemispherical entity CaMoO4 micro-
structures were obtained (Fig. 4c, d), as we can observe from
a broken coupled twin-shaped hemisphere. If ultrasonic
treatment was further implemented to the above product for
10 min, partial hollow coupled twin-shaped hemispheres
were achieved (Fig. 4e, f), the thickness of the shell varies
from 200 nm to 400 nm. As shown in Fig. 1b and c,
completely hollow coupled hemispheres were generated by
prolonging the ultrasonic time to 30 min, while the outline
and average particle size changed little. Interestingly, the hol-
low interior can't be obtained without ultrasonic processing
even aging for a relatively long time (1 hour, 10 hours and 1
day). Regarding the synthesis of hollow interiors, it is recog-
nized that the ripening process involves the mass transfer
between solid core and outside chemical solution under
Fig. 3 SEM images of the obtained samples in the presence of
different amounts of EDTA: (a) and (b) 0 mmol; (c) 0.01 mmol; (d)
0
.04 mmol.
2
8
ultrasonic treatment.
In order to verify the crystal form of the time-dependent
products, XRD patterns are presented in Fig. 5. It can be seen
that the crystallinity was considerably low when the reaction
time was 0 min (Fig. 5a), and increased gradually with the
reaction time prolonged (Fig. 5b, c), especially when ultra-
sound was implemented. When the reaction time was 45
the split degree increases further, and most of the obtained
particles were single microspheres (Fig. 3d) instead of uni-
form coupled hemispheres (Fig. 1b). It can be concluded
from the above phenomena that EDTA acted as an efficient
crystal-growth modifier to modify the morphology of the
3
3
product.
4
min, well-crystallized CTHH-CaMoO was obtained (Fig. 5d),
For a substantial view of the growth mechanism of the
CTHH-CaMoO4 architecture, the time-dependent evolution
process was monitored. The samples obtained at various
reaction times were inspected by SEM and TEM. The tempo-
ral evolution of the resulting structure is shown in Fig. 4.
Obviously, the primary particles in the range of 20–30 nm
while the location of the peaks and crystal form remained
throughout the whole process.
4
The growth pathway of CaMoO microstructures from pri-
mary particles to coupled twin-shaped hemispherical entities
was investigated at various intervals by TEM/HR-TEM. Fig. 6a
illustrates the low magnification TEM micrograph of shuttle-
(Fig. 4a, b) formed once solution B was mixed with solution
4
like CaMoO oriented aggregate crystals obtained when the
A. After continuous magnetic agitation for 15 min, the
reaction time was 1 min. HR-TEM performed in the corner of
the shuttle-like morphology (dashed white square in Fig. 6a)
reveals that the lattice fringes were a little obscure (Fig. 6b).
As the reaction time prolonged to 5 min, shuttle-like CaMoO4
transformed to straw-like structures (Fig. 6c) through imper-
3
7
fect oriented attachment, as can be confirmed by the
Fig.
5 Time-dependent XRD patterns: (a) 0 min; (b) 15 min
Fig. 4 TEM and SEM images of products obtained at various reaction
times: (a) and (b) 0 min; (c) and (d) 15 min (continuous magnetic
agitation); (e) and (f) 25 min (including 15 min continuous magnetic
agitation and 10 min ultrasonic treatment).
(continuous magnetic agitation); (c) 25 min (including 15 min
continuous magnetic agitation and 10 min ultrasonic treatment); (d) 45
min (including 15 min continuous magnetic agitation and 30 min
ultrasonic treatment).
2446 | CrystEngComm, 2015, 17, 2444–2449
This journal is © The Royal Society of Chemistry 2015

View Article Online
CrystEngComm
Communication
min. Fig. S1c and d† demonstrate straw-like morphologies
about 600–800 nm in length and 300–400 nm in width
obtained at 5 min. Coupled twin-shaped hemispherical
microstructures about 3–4 μm in length and 2–3 μm in width
were generated at 15 min (Fig. S1e and f†). The gradual
increase in length and width of the crystals can further iden-
tify the existence of the oriented attachment process.
On the basis of the above analysis, it is reasonable to spec-
4
ulate that the formation of CTHH-CaMoO structure is based
on the oriented attachment and subsequent Ostwald ripening
2
8,40,41
mechanism,
and the evolution process is illustrated in
nuclei aggregate into
Fig. 7. In this process, primary CaMoO
4
solid coupled twin-shaped hemispheres through oriented
attachment in the solution to minimize the surface energy.
The positive influence of ultrasonic treatment caused local
2
1
hotspots and cavitation effects, a phenomenon occurring
when a liquid is exposed to high power ultrasound. And the
creation of these extreme conditions can drive a variety of
chemical reactions, such as dissolution. Then redistribution
happens with the assistance of ultrasonic treatment, larger
crystallites outside are essentially immobile while the unsta-
ble smaller ones inside are undergoing mass relocation
through dissolving and regrowing, which creates the interior
space within the original aggregates. Finally, solid cores are
consumed and disappear, forming the hollow cavity inside
the coupled hemisphere.
The nitrogen adsorption–desorption isotherms of coupled
twin-shaped hemispherical CaMoO4 before and after the
ultrasonic treatment are shown in Fig. 8. As can be seen,
both isotherms exhibit stepwise adsorption and desorption,
which indicate the presence of mesoporosity in the sam-
Fig. 6 TEM and HR-TEM micrographs of the samples at various inter-
vals: (a) and (b) 1 min; (c) and (d) 5 min; (e) and (f) 15 min. (b, d and f
are corresponding HR-TEM images performed on the edge of the crys-
tal from a, c and e, respectively. The lattice fringes spaced at ca. 3.12 Å
4
2,43
ples.
The Brunauer–Emmett–Teller (BET) surface areas
2
−1
correspond to the distance of the (112) plane of tetragonal CaMoO
4
.)
for them are 125.2 and 142.4 m g , respectively. The larger
BET surface area of the latter one may come from the hollow
interior, which is caused by the sonochemical process. The
plot of the pore size distribution (inset in Fig. 8) was deter-
mined by using the Barrett–Joyner–Halenda (BJH) method
from the desorption branch of the isotherm. It can be seen
from the narrow distribution of pore size that almost all the
pores can be attributed to mesoporosity. The average pore
diameters before and after ultrasound are 3.5 and 3.4 nm,
respectively.
dislocations of the lattice fringes in Fig. 6d. The lattice
fringes spaced at ca. 3.12 Å, which correspond to the distance
of the (112) plane of tetragonal CaMoO , become clear. The
4
crystals maturated at 15 min exhibited coupled twin-shaped
hemispherical morphology (Fig. 6e). In this sample, the 3.12
Å lattice fringes were more clearly and frequently observed
than at 5 min, confirming the increased crystallinity and the
3
8
ordered structure of these nanoparticles (Fig. 6f), which has
been demonstrated by the XRD patterns in Fig. 5. Further
observing it, the spontaneous self-organization of adjacent
particles can be seen, and they would rotate and have contact
with each other until the crystallographic orientation of the
two crystals match (black arrow marked with oriented attach-
3
9
ment). Then they share a common crystallographic orienta-
tion, followed by the joining of these particles at a planar
interface to reduce the overall surface energy, which is in
3
7
agreement with previous results. The values of the length
and width of the crystals at various intervals were observed
(see the ESI† Fig. S1). It can be seen from Fig. S1a and b†
that most of shuttle-like CaMoO microstructures were in the
4
Fig.
7 Schematic formation process based on the oriented
range 200–400 nm in length and 100–200 nm in width at 1
attachment and Ostwald ripening mechanism.
This journal is © The Royal Society of Chemistry 2015
CrystEngComm, 2015, 17, 2444–2449 | 2447

View Article Online
Communication
CrystEngComm
7
8
9
A. K. Parchur, A. I. Prasad, A. A. Ansari, S. B. Rai and R. S.
Ningthoujam, Dalton Trans., 2012, 41, 11032–11045.
B. P. Singh, A. K. Parchur, R. S. Ningthoujam, A. A. Ansari,
P. Singh and S. B. Rai, Dalton Trans., 2014, 43, 4779–4789.
A. K. Parchur and R. S. Ningthoujam, Dalton Trans.,
2
011, 40, 7590–7594.
1
0 L. N. Wang, Y. Sun, C. S. Li, Y. Z. Wang, X. G. Ma, Y. D.
Wang, S. S. Li, Z. J. Zhang, P. J. Ma and G. H. Cui, Cryst. Res.
Technol., 2012, 47, 1231–1236.
1
1 Y. G. Liang, X. Y. Han, Z. H. Yi, W. C. Tang, L. Q. Zhou, J. T.
Sun, S. J. Yang and Y. H. Zhou, J. Solid State Electrochem.,
2
007, 11, 1127–1131.
1
1
1
1
1
2 Y. Jin, J. H. Zhang, Z. D. Hao, X. Zhang and X. J. Wang,
J. Alloys Compd., 2011, 509, L348–L351.
3 W. S. Wang, L. Zhen, W. Z. Shao and Z. L. Chen,
CrystEngComm, 2014, 16, 2598–2604.
4 Q. Gong, X. F. Qian, X. D. Ma and Z. K. Zhu, Cryst. Growth
Des., 2006, 6, 1821–1825.
5 J. J. Zhang, L. L. Li, W. W. Zi, N. Guo, L. C. Zou, S. C. Gan
and G. J. Ji, J. Phys. Chem. Solids, 2014, 75, 878–887.
6 Y. Sun, C. S. Li, Z. J. Zhang, X. G. Ma, L. N. Wang, Y. Z.
Wang, M. Y. Song, P. J. Ma, L. P. Jiang and Y. M. Guo, Solid
State Sci., 2012, 14, 219–224.
Fig.
8
N
2
adsorption–desorption isotherms of the samples
synthesized at different reaction times: (a) 15 min (without ultrasonic
treatment); (b) 45 min (with 30 min ultrasonic treatment). The inset
shows the pore size distribution of the corresponding samples.
Conclusion
1
1
1
2
2
7 Y. S. Luo, X. J. Dai, W. D. Zhang, Y. Yang, C. Q. Sun and
S. Y. Fu, Dalton Trans., 2010, 39, 2226–2231.
In summary, CTHH-CaMoO4 microstructures with uniform
morphology and controllable size have been synthesized via a
facile ultrasound-assisted template-free route at room tem-
perature. The oriented attachment and Ostwald ripening
mechanism are proposed to account for the formation of this
novel structure via time-dependent observations. It is the
influence of the solvent properties of ethanol and the
structure-directing effect of EDTA that play pivotal roles in
the fabrication of this unique architecture. This novel archi-
tecture possessing high specific surface area, hollow interior,
mesoporous structure and low density will show better per-
formance in electro-optical devices, scintillators, photo-
luminescence, etc. This environmentally friendly technique
can be applied to synthesize other metal molybdate and tung-
state microstructures with complex morphologies.
8 G. C. Fan, Z. Y. Huang and T. H. Wang, Solid State Sci.,
2
013, 16, 121–124.
9 J. Geng, J. J. Zhu and H. Y. Chen, Cryst. Growth Des., 2006, 6,
21–326.
0 J. L. Zhang, J. M. Du, B. X. Han, Z. M. Liu, T. Jiang and Z. F.
Zhang, Angew. Chem., Int. Ed., 2006, 45, 1116–1119.
1 C. C. Yu, M. Yu, C. X. Li, C. M. Zhang, P. P. Yang and J. Lin,
Cryst. Growth Des., 2009, 9, 783–791.
3
2
2
2 S. F. Wang, F. Gu and M. K. Lu, Langmuir, 2006, 22, 398–401.
3 J. J. Zhu, S. Xu, H. Wang, J. M. Zhu and H. Y. Chen, Adv.
Mater., 2003, 15, 156–159.
2
2
2
2
4 N. A. Dhas and K. S. Suslick, J. Am. Chem. Soc., 2005, 127,
2
368–2369.
5 X. W. Lou, Y. Wang, C. L. Yuan, J. Y. Lee and L. A. Archer,
Adv. Mater., 2006, 18, 2325–2329.
6 Y. J. Xiong, B. Wiley, J. Y. Chen, Z. Y. Li, Y. D. Yin and Y. N.
Xia, Angew. Chem., Int. Ed., 2005, 44, 7913–7917.
7 Y. S. Wu, H. Yu, F. Peng and H. J. Wang, Mater. Lett.,
2012, 67, 245–247.
Notes and references
1
2
3
J. Hu, M. Chen, X. S. Fang and L. M. Wu, Chem. Soc. Rev.,
011, 40, 5472–5491.
Y. B. Cao, J. M. Fan, L. Y. Bai, F. L. Yuan and Y. F. Chen,
Cryst. Growth Des., 2010, 10, 232–236.
P. Podsiadlo, S. G. Kwon, B. Koo, B. Lee, V. B. Prakapenka,
P. Dera, K. K. Zhuravlev, G. Krylova and E. V. Shevchenko,
J. Am. Chem. Soc., 2013, 135, 2435–2438.
G. S. R. Raju, E. Pavitra, Y. H. Ko and J. S. Yu, J. Mater.
Chem., 2012, 22, 15562–15569.
2
28 H. G. Yang and H. C. Zeng, J. Phys. Chem. B, 2004, 108,
3492–3495.
29 A. X. Wang, D. Q. Chu, L. M. Wang, B. G. Mao, H. M. Sun
and Z. C. Ma, RSC Adv., 2014, 4, 7545–7548.
30 Y. K. Yin, F. H. Yang, Y. Yang, Z. B. Gan, Z. M. Qin, S. Gao,
B. B. Zhou and X. X. Li, Superlattices Microstruct., 2011, 49,
599–607.
31 H. P. Cong and S. H. Yu, Cryst. Growth Des., 2009, 9, 210–217.
32 T. S. Sreeprasad and T. Pradeep, Langmuir, 2011, 27,
3381–3390.
4
5
6
V. B. Mikhailik and H. Kraus, Phys. Status Solidi B,
2
010, 247, 1583–1599.
S. Dutta, S. Som and S. K. Sharma, Dalton Trans., 2013, 42,
654–9661.
33 Y. K. Yin, Y. Li, H. F. Zhang, F. Y. Ren, D. W. Zhang, W. X.
Feng, L. L. Shao, K. J. Li, Y. Liu, Z. P. Sun, M. J. Li, G. C.
9
2448 | CrystEngComm, 2015, 17, 2444–2449
This journal is © The Royal Society of Chemistry 2015

View Article Online
CrystEngComm
Communication
Song and G. Wang, Superlattices Microstruct., 2013, 55,
09–117.
4 Y. K. Yin, Z. B. Gan, Y. Z. Sun, B. B. Zhou, X. Zhang, D. W.
Zhang and P. Gao, Mater. Lett., 2010, 64, 789–792.
5 H. Deng, C. M. Liu, S. H. Yang, S. Xiao, Z. K. Zhou and Q. Q.
Wang, Cryst. Growth Des., 2008, 8, 4432–4439.
6 J. Tang and A. P. Alivisatos, Nano Lett., 2006, 6, 2701–2706.
7 R. L. Penn and J. F. Banfield, Science, 1998, 281, 969–971.
8 M. Iafisco, G. B. Ramírez-Rodríguez, Y. Sakhno, A. Tampieri,
G. Martra, J. Gómez-Morales and J. M. Delgado-López,
CrystEngComm, 2015, 17, 507–511.
39 D. S. Li, M. H. Nielsen, J. R. I. Lee, C. Frandsen, J. F.
Banfield and J. J. De Yoreo, Science, 2012, 336,
1014–1018.
40 L. Zhou, W. Z. Wang, H. L. Xu and S. M. Sun, Cryst. Growth
Des., 2008, 8, 3595–3601.
41 G. Z. Chen, C. X. Xu, X. Y. Song, S. L. Xu, Y. Ding and S. X.
Sun, Cryst. Growth Des., 2008, 8, 4449–4453.
42 Y. D. Hou, X. C. Wang, L. Wu, Z. X. Ding and X. Z. Fu,
Environ. Sci. Technol., 2006, 40, 5799–5803.
1
3
3
3
3
3
43 P. Zarabadi-Poor, A. Badiei, B. D. Fahlman, P. Arab and
G. M. Ziarani, Ind. Eng. Chem. Res., 2011, 50, 10036–10040.
This journal is © The Royal Society of Chemistry 2015
CrystEngComm, 2015, 17, 2444–2449 | 2449