Controllable growth of three-dimensional CdS nanoparticles on TiO2nanotubes to enhance photocatalytic activity

Article abstract of DOI:10.1039/c9ra10895e

Exploiting photocatalysts with characteristics of low cost, high reactivity and good recyclability is a great significance for environmental remediation and energy conversion. Herein, hollow TiO₂nanotubes were fabricated by a novel and efficient methodviaelectrospinning and an impregnation calcination method. With the hydrothermal method, the CdS nanoparticles were modified on the surface and in walls of the TiO₂nanotubes. By changing the reaction conditions, the morphology of CdS nanoparticles presents a controllable three-dimensional (3D) structure. The morphology of the samples was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure and components of samples were characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). The light absorption efficiency was detected using UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL). The photocatalytic properties were evaluated by degradation of methyl orange (MO) and photocatalytic hydrogen evolution under visible light irradiation. From the results, the TiO₂/CdS nanotubes exhibit better photocatalytic activity than the pure TiO₂. The synthetic mechanism of TiO₂/CdS heterostructures and a possible photocatalytic mechanism based on the experimental results were proposed.

Full text of DOI:10.1039/c9ra10895e

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PAPER
Controllable growth of three-dimensional CdS
nanoparticles on TiO nanotubes to enhance
2
Cite this: RSC Adv., 2020, 10, 16776
photocatalytic activity†
Guo-Min Liu, Wen-Yuan Jia, Qiu-Shi Jiang and Zhi-Qiang Cheng *b
a
a
b
Exploiting photocatalysts with characteristics of low cost, high reactivity and good recyclability is a great
2
significance for environmental remediation and energy conversion. Herein, hollow TiO nanotubes were
fabricated by a novel and efficient method via electrospinning and an impregnation calcination method.
With the hydrothermal method, the CdS nanoparticles were modified on the surface and in walls of the
2
TiO nanotubes. By changing the reaction conditions, the morphology of CdS nanoparticles presents
a controllable three-dimensional (3D) structure. The morphology of the samples was characterized by
scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure and
components of samples were characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis
EDX) and X-ray photoelectron spectroscopy (XPS). The light absorption efficiency was detected using
UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL). The photocatalytic
properties were evaluated by degradation of methyl orange (MO) and photocatalytic hydrogen evolution
(
Received 16th January 2020
Accepted 6th April 2020
under visible light irradiation. From the results, the TiO
activity than the pure TiO . The synthetic mechanism of TiO
photocatalytic mechanism based on the experimental results were proposed.
2
/CdS nanotubes exhibit better photocatalytic
DOI: 10.1039/c9ra10895e
2
2
/CdS heterostructures and a possible
rsc.li/rsc-advances
and morphology, for nanoscale semiconductor to perform well
as catalysts, they at least satisfy three characteristics: (1) high
With progress in the eld of nanotechnology, it has become specic surface area, (2) have good stability and (3) the size and
1
Introduction
2
3–25
possible to prepare semiconducting materials of nanocrystal distribution should be uniform.
Therefore, TiO
2
nanotubes
in
terms of size and specic surface area, design and fabricate
which have garnered extensive attention on account of their TiO based nanotubes for heterogeneous photocatalysis have
become a hot research topic. Thus far, many synthesis methods
structures with special shapes and dimensions, such as nano- shows intrinsic advantages compared to traditional TiO
2
1
–5
26

bers, nanorods, nanoowers, nanospheres and nanotubes,
2
6
–9
unique electronic, optical, and photoactive properties.
Meanwhile, they are widely utilized in the elds of gas sensors, such as electrodeposition method, sol–gel method, template-
optical devices, visible light detectors, and eld emission assisted and hydrothermal treatment, have been developed
10–15
18,19,27,28
emitters, especially for photocatalysis.
Among copious for fabricating TiO
2
nanotube.
However, these tradi-
inorganic semiconductor nanostructures, titanium oxide (TiO2) tional method oen accompanied problems such as cumber-
has been extensively studied to date, with extensive research on some operation, template hard removal, high production cost
2
9
its high surface-to-volume ratio, low cost, environmental and poor structural stability, etc.
16–19
friendliness and unique physical and chemical properties.
Recently, the application of TiO
as photocatalysts for degra- (PG) electron/hole pairs is another limits factor of photo-
dation of toxic organic pollutants have attracted wide public catalysis.
attention, because the TiO
nanostructure and its composites a convenient way for improving photocatalytic efficiency, but it
can signicantly improve the photocatalytic performance.
The properties of nanomaterials mainly rely on their nanoscale making TiO
Meanwhile, the high recombination rate of photogenerated
2
30,31
Although reduce the size of nanoscale TiO open
2
2
20–22
32,33
cannot tackle the fundamental limits issue.
By contrast,
2
doped with other elements, modied with noble
metal and combined with other semiconductors to form het-
erostructures, which provide a effective means to inhibit the
a
34–38
Department of Orthopedics, The Second Hospital of Jilin University, Changchun
recombination of PG electron/hole pairs.
It is necessary to
1
b
30000, China
design new-type composite photocatalysts not only improve the
separation of PG electron/hole pairs, but also extend the optical
College of Resources and Environment, Jilin Agriculture University, Changchun
1
30118, China. E-mail: czq5974@163.com
absorption of TiO , thus to obtain a more efficient utilization of
2
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c9ra10895e
39,40
solar energy.
Cadmium sulde (CdS) is an excellent n-type
1
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semiconductor with an ideal band-gap energy of 2.4 eV, which
4
1,42
could absorb the visible light radiation up to 520 nm,
has
By
34,43
been widely used as a visible light response sensitizer.
comparing the energy levels of TiO with CdS, which could nd
2
their analogical band structures are quite suitable to construct
heterostructures and bring an effective separation of PG
44,45
electron/hole pairs.
tion the TiO with CdS form a heterostructure structure for
overcoming the demerits that exist in TiO and CdS
Therefore, that is expected to combina-
2
2
46
simultaneously.
Herein, we described the fabrication of CdS decorated TiO2
nanotubes via electrospinning combined with controlled calci-
nation and hydrothermal process. By changing the synthesis
condition, the density and size of CdS on the surface (inner
2
Fig. 1 An illustration of the formation mechanism of the TiO /CdS
nanotubes.
wall) of the TiO
2
nanotubes can be controlled. The morphology
nanotubes were observed by the
and dimension of the CdS/TiO
2
SEM and TEM. The crystal phases, optical absorption proper- volumes are 15 mL. Then, the Teon-lined autoclave was heated
ꢀ
ties, elemental and chemical state were explored by XRD, DRS to 200 C and keep 8 hours. Finally, the CdS/TiO
2
nanotubes
and XPS. Due to the formation of CdS/TiO2 heterojunction were collected and washed in DI water. For compare the effect of
structure, the hybrid nanoparticles could reduce the recombi- reactant concentration on morphology, change the concentra-
À1
nation of PG electron–hole pairs, and the hollow nanotubes tion of Cd(NO
structure provides a larger specic surface area and more active corresponding CdS/TiO
sites, that the as-prepared CdS/TiO
nanotubes signicantly TC3 and TC4, respectively (Fig. 1).
)
solution to 5, 10, 20, 30 mmol L and the
3
2
nanotubes was named as TC1, TC2,
2
2
improved photocatalytic activity. Moreover, that may provide
a new method for preparation of semiconductor hetero-
structure nanotubes.
2
.3 Measurement of photocatalytic activity
Methyl orange (MO) was used as the target substrates for eval-
uating the photocatalytic activity. The photocatalytic reaction
was carried out in a reactor with a circulating water system to
maintain a constant temperature. The xenon lamp (Philips, 100
W) equipped with a 420 nm cut-off lter instead and the irra-
diation time were ranged from 5 to 200 min. Under the same
conditions, all samples were placed in the quartz tube, which
away from the irradiation source 5 cm. The degradation ratio
2
Experimental
2.1 Materials
À1
Polystyrene (PS, M
w
z 350 000 g mol ), tetrabutyltitanate
TBOT, 97%), cadmium nitrate [Cd(NO ) $4H O, 99%], thiourea
(
(
3
2
2
CH N S, 99%), absolute ethanol (C H O, 99%), N,N-dime-
4
2
2
6
thylformamide (DMF, 99%), and methyl orange (MO, 96%) were
purchased from Aladdin; all of chemicals used in the experi-
ments were analytical grade and used without further
purication.
À1
was 40 mL MO solution (10 mg L ) with 40 mg photocatalyst.
Then, the suspension was stirred in the dark for 1 hour to
establish adsorption and desorption equilibrium. During the
photoreaction process, approximately 3 mL of the mixture was
sampled in a constant time, and use centrifugation to separate
the nanoparticles. The, using the spectrophotometer to deter-
mination the solution concentration. H2 evolution reactions
were proceed in a closed gas-circulation system. 50 mg samples
were dispersed in 200 mL aqueous solution of Na
Na SO (1.0 M). Aer removing the air of reaction system, the
solution were irradiated by a 100 W xenon lamp equipped with
a 420 nm cut-off lter, and the amount of H were measured by
gas chromatography (GC-9700, N carrier).
2.2 Methods
The precursor solution was prepared by adding 1.4 g PS to
ꢀ
5
.0 mL DMF with magnetic stirring at 50 C. Aer PS dissolution
2
S (1.0 M) and
in the DMF completely, the prepared solution was loaded into
2
3
a syringe, which was connected to a 15 kV high voltage. The ow
À1
rate of the solution was controlled at 0.5 mL h , and the
2
distance from needle to the rotate acceptor was 20 cm. The
whole process was kept with humidity below 20%. Then, the PS
membrane were soaked in the BOT/ethanol (volume ratio 1 : 10)
precursor solution for 5 min. Then, the composite TBOT/PS
precursor bers were natural air dried. Finally, the precursor
2
3
Results and discussion
ꢀ
ꢀ
À1
3.1 XRD patterns

bers were calcined to 550 C with a rate of 2 C min and keep
ꢀ
5
50 C for 2 hours, to burn the PS templates completely. Aer Fig. 2 present the XRD pattern of the as-prepared photocatalysts.
annealing, the hollow TiO nanotubes were obtained.
The sharp and strong diffraction peaks showed the nanotubes
2
Hydrothermal method was used for CdS nanoparticles were well crystallized. The main diffraction peaks of TiO were
2
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
modied. The as prepared TiO nanotubes were transferred into located at 25.45 , 37.95 , 48.20 , 55.16 and 62.81 can be indexed
2
a Teon-lined autoclave, which containing 30 mL solution of to the (101), (004), (200), (211) and (204) directions, respectively,
Cd(NO ) and thiourea, the concentration are equal and both which indicates that the prepared titanium oxide belongs to the
3 2
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regular and uniform nanotubes with diameter of approximately
700 nm and the uniformity was above 80%, demonstrating the
TBOT/ethanol solution permeate into the surface of the PS
template bers successful. From the illustration of Fig. 3A, we
can observe the high magnication SEM of a TiO nanotube
2
that present the wall thickness of the nanotube about 100 nm
and the inwall of the nanotubes are rough. Fig. 3B clearly
2
present the SEM image of core–shell structure TiO nanotubes,
which was obtained by replacing PS/DMF solution with PAN/
DMF solution (PAN: 13 wt%) and other operations were the
same. The core might be carbon bers which produced by the
PAN incomplete calcination. The SEM of four kinds of CdS/TiO2
hybrid showed in the Fig. 3C–F with low and high magnica-
2 2
tions. Compared to the pure TiO nanotubes, the CdS/TiO
nanotubes could observed amount of nanoparticles deposited
on the surface and inwall, and the density of nanoparticles
2
+
increase with the concentration of Cd ions. These results show
that the morphology of CdS modied on the nanotubes was
related to the solution concentration. Notably, further increase
of Cd , the CdS nanoparticles grown together to form a pine-
cone shaped 3D structure as shown in Fig. 3F. The
morphology and microstructure of as-prepared photocatalysts
also investigated by TEM. The low magnication TEM image
Fig. 2 The XRD patterns of the as-prepared photocatalysts.
2
+
(Fig. 4B) further veries that CdS nanoparticles were well
covered the surface and inwall of TiO nanotubes, compared to
2
the TEM of TiO nanotubes (Fig. 4A). These nanoparticles with
2
sizes of 5–50 nm are distributed randomly on the TiO . The high
2
resolution TEM image (Fig. 4D) clearly reveals an intimate
interface between the TiO
heterojunctions, which is favorable for the electron transfer in
photocatalytic activity. Also demonstrates the CdS/TiO photo-
catalyst obtained by hydrothermal method form a hetero-
structure rather than a mixture of TiO and CdS. Meanwhile, the
2
and CdS in the composite to form
2
2
Fig. 3 The SEM images of the samples: (A) TiO
shell structure TiO nanotubes, (C) TC1 nanotubes, (D) TC2 nanotubes,
E) TC3 nanotubes and (F) TC4 nanotubes.
2
nanotubes, (B) core–
2
(
anatase structure (JCPDS 21-1272), and with a high purity.
Compared with pure TiO2, the CdS/TiO nanotubes can observe
the peak at 26.52 , 43.72 conrms the formation of CdS peaks
JCPDS 65-2280), and the peaks were enhanced with increased
2
ꢀ
ꢀ
(
2
+
Cd concentration. Meanwhile, there is also a certain amount of
ꢀ
rutile phase at 27.2 in the all CdS/TiO nanotubes. Compared the
2
main diffraction pattern of three CdS/TiO
of rutile show an decreased trend due to the addition of Cd ,
which mean the rutile may be an intermediate form of CdS/TiO
heterogeneous structure.
2
nanotubes, the peaks
2
+
2
2
Fig. 4 The TEM image of TiO nanotubes (A) and TC3 nanotubes (B),
the STEM image of TC3 nanotubes (C) and the HRTEM of TC3 nano-
tubes (D), the SAED pattern of the TC3 (E) and the CdS Nps of the
3
.2 Morphology of electrospun nanotubes TiO
The morphology of the nanotubes were characterized by SEM.
Fig. 3A show the SEM image of TiO
2
/CdS
, which are composed by surface of TC3 (F).
2
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high resolution TEM are carried out to survey the lattice fringes
of CdS/TiO2 nanotubes, the lattice spacing are 0.35 nm and
0.33 nm, which are coincident with the (101) spacing of anatase
TiO and (111) of CdS phase. The legible fringe also suggests the
2
high degree of crystallinity corresponds with the result of XRD
results. The Fig. 4E illustrates the selected area electron
diffraction (SAED) pattern of TiO /CdS, which presentation
2
a bright diffraction rings assigned to high crystallization and
polycrystalline structure. The Fig. 4F was SAED pattern of pure
CdS nanoparticles on the surface of TC3 means the obtained
CdS particles were pure single crystals.
3
.3 XPS analysis
XPS analyze could reveal the information about the surface
composition and chemical state. As shown in Fig. 5A, CdS/TiO
2
hybrid (TC2) is mainly composed of ve elements, which is Ti,
O, Cd, S and C, The peak of C 1s can be ascribed to the
hydrocarbon from the instrument itself. The high resolution
spectra of Ti 2p were exhibited in the Fig. 5B. The Ti 2p spectra
shows the peaks at 458.3 eV and 464.1 eV for Ti 2p3/2 and Ti 2p1/2
of TiO
2
, respectively. The distance between the two peaks is
indicating that
Ti ion is in the form of Ti , high resolution spectrum of Cd 3d
Fig. 4C) displayed characteristic peaks of 404.5 eV and 411.4 eV,
which are corresponding to the Cd 3d5/2 and Cd 3d3/2 states of
5
.8 eV, which is identical to that of the neat TiO
2
4
+
Fig. 6 (A) The UV-vis diffuse reflection spectra (DRS) of the as-
prepared photocatalysts and (B) Kubelka–Munk transformed reflec-
tance spectra.
(
2
+
Cd in CdS, respectively. Consequently, XPS analysis further
determines the formation of TiO and CdS in the sample, which
2
is agreement with XRD and TEM result.
spanning from 230 to 800 nm were showed. Compared to the
TiO
40–380 nm, especially in the ultraviolet light range. Aer the
modied of CdS, all CdS/TiO nanotubes present a remarkable
2
nanotubes, the TC2 had a lower reectivity in the range of
3
.4 UV-vis diffuse reection spectra and PL spectra
2
UV-vis DRS are tested to determine the optical properties of the
2
light adsorption into the visible light region, which may due to
the excellent visible-light photoresponse of CdS nanoparticles.
photocatalysts. From the results of DRS (Fig. 6A) the reection
spectra of TiO
2
and CdS/TiO
2
heterostructure in the region
Notably, the adsorption edges of CdS/TiO nanotubes gradually
2
broaden with the mount of modied CdS nanoparticles
increasing, indicated the high responsiveness of the photo-
catalyst to visible light.
Fig. 6B is the forbidden bandwidth obtained by the catalyst
according to the Kubelka–Munk formula. Among them, the
forbidden band widths of TiO
structures (TC1, TC2, TC3 and TC4) are 3.17 eV, 2.17 eV, 2.08 eV,
.92 eV and 2.01 eV. It can be seen from the comparison with
2 2
and four CdS/TiO hetero-
1
the TiO tubes that the forbidden bandwidth of the CdS/TiO2
2
heterostructure is signicantly reduced. Among them, TC3 has
the lowest forbidden bandwidth. We can speculate that this
sample has the best catalytic performance, and the catalytic
experiments proved that the prediction was correct. (The
detailed content of the edge position is Fig. S1.†)
3.5 Photoluminescence analysis
PL spectroscopy is correlation with the separation and recom-
bination of PG electrons/holes. As shown in Fig. 7, the PL
spectra of the TiO nanotubes showed a strong emission peak at
2
390 nm (excitation wavelength: 370 nm). However, the PL peak
Fig. 5 The XPS spectra of the TiO
2
and TC3 nanotubes: full spectrum
of the sample (A), the Ti 2p spectrum (B) and Cd 3d spectrum (C).
intensity of CdS/TiO
nanotubes was signicantly decreased
2
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Fig. 8B, under visible light irradiation (l > 420 nm) for 200
minutes the TC3 shows the excellent visible light catalysis
(
95.2%) similar to the TC4 (94.7%), which CdS load looks like
pine-cone shaped and much higher than TC2 (82.6%), TC1
61.2%), and pure TiO nanotubes (0.09%), which was consis-
tent with the results of UV-vis DRS. In addition, we also inves-
tigated the photocatalytic stability of TiO /CdS heterostructure
TC3) under visible light irradiation. The results indicated that
(
2
2
(
the hybrids exhibited good stability aer being reused for ve
times (Fig. 8D).
Meanwhile, the photocatalytic activities of the nanotubes were
evaluated by H production experiment under the visible light
2
irradiation in aqueous solution (containing 1.0 M Na
.0 M Na S as sacricial reagents). Fig. 8C shows the H
rate by the TiO and TiO /CdS nanotubes, and there is no
appreciable H was observed when TiO nanotubes was tested. In
2
SO
evolution
3
and
1
2
2
Fig.
7 The photoluminescence spectra of the as-prepared
2
2
photocatalysts.
2
2
2
contrast, the TC1 exhibited a slightly enhanced H evolution rate
À1 À1
of 22.35 mmol g
h . With the increase of CdS, the H evolution
2
with modication amount of CdS nanoparticles increased. The
key factor in the formation of this phenomenon is the defects in
rate are increased. The H evolution rate of TC2 photocatalyst is
2
À1 À1
À1 À1
6
4.26 mmol g
a maximum H
employ CdS as cocatalyst for improving efficiency of TiO
h
and TC3 (118.73 mmol g
evolution rate, demonstrates that is effective to
photo-
h ) reaches
the crystal structure of TiO , which act as traps for capturing the
2
2
photo-excited electrons and thus, inhibit the recombination of
the electrons and holes pairs.
2
catalytic activity. Further increases the amount of modication of
À1 À1
CdS, the H
2
generation rate (TC4 112.86 mol g
h ) showed
3.6 Photocatalytic activity and recycled photocatalytic
a slight decrease. This might be due to the less exposed active
degradation performance
sites of TiO /CdS resulting from the excess CdS shielding.
2
To identify the photocatalytic of the as-prepared samples, MO
solution degradation were tested under UV and visible irradia-
tion. The photocatalytic effect was evaluated by C /C (C nd C
0 t 0 t
were the initial concentration and the concentration of MO at
time t, respectively). From the Fig. 8A, shows the concentration
change of MO in the process of photodegradation, aer irradi-
ated by UV light for 30 min, the photocatalytic degradation
efficiencies of the TC2 nanotubes are 95.3% slightly better than
the TC3 (83.2%), which is much higher than the TC4 (72.5%)
3
.7 Mechanism for the enhancement of photocatalytic
activity
The principle of photocatalytic decomposition over CdS/TiO
2
heterostructure is delineated in Fig. 9. Under the visible-light
irradiation, the charge carriers were rstly generated from
CdS owing to its narrow energy band gap. The photoexcited
electrons on the valence band (VB) of CdS can move to their own
conduction band (CB). However, the high recombination of
2
and pure TiO nanotubes (37.8%). The photodegradation of MO
without catalysis almost negligible. However, as shown in
À
+
electrons (e ) and holes (h ) of CdS limits its photocatalytic
activity. When the TiO and CdS form a heterostructure, the PG
2
À
e
on CdS nanoparticles can easily transfer to the CB of TiO
2
through the interface as a result of the lower conduction edge
Fig. 8 Degradation rates of as-prepared photocatalysts under the UV-
light (A); degradation rates of as-prepared photocatalysts under the
visible light (B); the rate of H
visible light (C); the repeatability tests studied on the TC3 nanotubes Fig. 9 Schematic diagram for the photocatalytic mechanism of the
for five recycles (D). TiO /CdS catalysts under visible-light irradiation.
2 2
evolution on TiO /CdS nanotubes under
2
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+
potential of TiO
2
than that of CdS. Meanwhile, the h remain on
3 J. N. Li, Z. Q. Cheng, M. Z. Liu, M. Y. Zhang, M. J. Hu,
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À
the VB of CdS. Therefore, the TiO acts as a temporary e trap to
decrease the recombination of PG e /h . Consequently, the PG
h on the VB of CdS can react with the surface adsorbed H O to
2
À
+
+
2
À
generate $OH. The e on the CB of TiO
2
could reduce the
. Organic dye (MO) are eventually
À
adsorbed O
2
to form $O
2
oxidized by these highly active species to CO
ucts. The major reaction steps are revealed as follows:
2
and H
2
O prod-
5 R. Zamiri, B. Singh, M. S. Belsley and J. M. F. Ferreira, Ceram.
Int., 2014, 40, 6031–6036.
6
W. Tian, T. Y. Zhai, C. Zhang, S. L. Li, X. Wang, F. Liu,
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À
+
TiO /CdS + hv / TiO /CdS (e + h )
(1)
(2)
(3)
(4)
(5)
2
2
À
+
À
+
(e ) + CdS (h )
TiO
2
/CdS (e + h ) / TiO
2
7
8
À
À
e
+ O + / $O
2
2
Y. A. Zhang, C. X. Wang, Z. M. Yuan, L. Y. Zhang and
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À
2À
+
À
e
+ $O + H / $OH + OH
10.1002/ejic.201601535.
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h + H
9
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$
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2
1
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Conclusions
In summary, hollow TiO nanotubes were obtained using elec-
2
trospinning combined with an impregnation calcination 12 S. H. Hwang, J. Song, Y. Jung, O. Y. Kweon, H. Song and
J. Jang, Chem. Commun., 2011, 47, 9164–9166.
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method. CdS nanoparticles were modied on the surface and
inner wall of TiO nanotubes via hydrothermal process. By
changing the reaction conditions, the size and density of CdS on
the surface and inner wall of the TiO nanotubes can be
1
2
1
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À
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hollow nanotubes structure provides a larger specic surface
area and more active sites, that the CdS/TiO nanotubes showed
remarkably photocatalytic activity than pure TiO . Moreover,
that may provide a new method for preparation of hetero-
structure nanotubes.
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1
1
1
2
2
Conflicts of interest
6
, 7402–7410.
No conicts of interest in this article.
2
0 F. X. Xiao, ACS Appl. Mater. Interfaces, 2012, 4, 7054–7062.
1 F. L. Zhang, Z. Q. Cheng, L. Y. Cui, T. T. Duan, A. Anan,
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Acknowledgements
2
This study was supported by the Special Health Project of Jilin
Province, China (No. 3D516D703429) and the Special Health
Project of Department of Finance of Jilin Province, China (No.
6
3520–63525.
3 D. D. Lin, H. Wu, R. Zhang and W. Pan, Chem. Mater., 2009,
1, 3479–3484.
4 G. H. Hou, Z. Q. Cheng, L. J. Kang, X. J. Xu, F. L. Zhang and
H. J. Yang, Crystengcomm, 2015, 17, 5496–5501.
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