Visible-Light-Driven Photocatalysis of Gd-Doped ZnO Nanoparticles Prepared by Tartaric Acid Precipitation Method

Article abstract of DOI:10.1134/S0036023619120143

Abstract: Visible-light-driven Gd-doped ZnO nanoparticles have been synthesized by tartaric-assisted precipitation method. The content of Gd dopant can play the role in morphology and photocatalysis. XRD patterns of ZnO and Gd-doped ZnO certified that all

Full text of DOI:10.1134/S0036023619120143

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2019, Vol. 64, No. 12, pp. 1600–1608. © Pleiades Publishing, Ltd., 2019.
INORGANIC MATERIALS
AND NANOMATERIALS
Visible-Light-Driven Photocatalysis of Gd-Doped ZnO
Nanoparticles Prepared by Tartaric Acid Precipitation Method
a
a,
b, c
b, d
Surisa Sa-nguanprang , Anukorn Phuruangrat *, Titipun Thongtem , and Somchai Thongtem
a
Department of Materials Science and Technology, Faculty of Science, Prince of Songkla University,
Hat Yai, Songkhla, 90112 Thailand
b
Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 Thailand
c
Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 Thailand
d
Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 Thailand
e-mail: phuruangrat@hotmail.com
*
Received January 31, 2019; revised May 3, 2019; accepted June 24, 2019
Abstract—Visible-light-driven Gd-doped ZnO nanoparticles have been synthesized by tartaric-assisted pre-
cipitation method. The content of Gd dopant can play the role in morphology and photocatalysis. XRD pat-
terns of ZnO and Gd-doped ZnO certified that all samples have hexagonal ZnO structure. TEM images of
the samples showed that the particle size of products has been deceased with increasing in Gd content from
0
wt % to 5 wt % due to the inhibited growth of crystallite. The photocatalytic activities of Gd-doped ZnO
samples with different contents of Gd dopant have been studied by measuring the degradation of methylene
blue (MB) under visible light irradiation. In this research, 5 wt % Gd-doped ZnO nanoparticles with particle
size of 20–30 nm showed the highest photocatalytic activity for photodegradation of MB at 100% within
3+
4
5 min because Gd ions acted as an effective electron scavenger to trap photo-induced electrons and inhibit
electron–hole recombination.
Keywords: Gd-doped ZnO nanoparticles, photocatalysis, spectroscopy
DOI: 10.1134/S0036023619120143
INTRODUCTION
reported that visible-light-driven photocatalytic effi-
ciencies of ZnO can be improved by doping with rare
earth metal such as La, Ce, Dy, Pr, Er, Sc, Y and Yb
Semiconductor photocatalyst is a promising mate-
rial used for photodegradation of organic contami-
nants containing in wastewater from dye textile indus-
tries, paper and pulp industries, and pharmaceutical
industries because photocatalysis is green technology.
The material has high chemical stability and complete
elimination of organic contaminants in wastewater by
transforming the contaminants into CO , H O and
small organic/inorganic compounds [1–4]. Among a
number of semiconductor photocatalysts, ZnO with
direct band gap of 3.37ꢀeV at room temperature is an
important member of the II–VI semiconductor and is
able to apply for many fields such as energy conver-
sion, gas sensors, photovoltaic material, water split-
ting, photocatalysis and transparent electrodes for
solar cells because of its outstanding properties: phys-
ical and chemical stability, thermal stability, high
refractive index, low cost and non-toxicity [5–11].
However, the photocatalytic reaction of ZnO is lim-
ited and active to only UV light, including fast recom-
bination of the photogenerated electron–hole pairs
[
5–7, 12, 13]. The rare earth metal dopant acts as elec-
tron trapping site on the host lattice to reduce recom-
bination of electron-hole pairs and increase surface
defects, that help to shift the absorption towards visi-
3+
ble light region [5–7, 12, 13]. Thus, Gd ion with
half-filled structure in the 4f orbital was selected as a
dopant containing in ZnO lattice because it has an
effective ability of electronic trapping and releasing,
including high photocatalytic activity for photodegra-
dation of dyes and organic contaminants in wastewater
such as rhodamine B (RhB), methylene blue (MB),
tetracycline, methyl orange (MO) and 4-chlorophenol
under visible light [14–17]. For example, pure ZnO
and Gd-doped ZnO nanostructures were synthesized
by a sonochemical method [15]. Gd-doped ZnO was
able to show higher photocatalytic rate for methylene
blue under UV and visible light irradiation than pure
2
2
ZnO. Gd-doped β-Bi O also showed much higher
2
3
photocatalytic activity for photodegradation of phe-
nol, methyl orange (MO) and rhodamine B (RhB)
[
5, 12, 13]. Thus, developing of visible light-responsive
photocatalyst has become one of the greatest chal-
lenges in doing the research of ZnO. There has been tion of photo-induced electron–hole pairs by Gd
dyes than pure β-Bi O , attributed to effective separa-
2
3
3+
1600

VISIBLE-LIGHT-DRIVEN PHOTOCATALYSIS of Gd-DOPED ZnO
1601
served as an efficient scavenger to trap photo-gener- source. All the XPS spectra were calibrated w.r.t. a C
ated electrons [16].
1s electron peak at 285.1 eV.
The photocatalytic activities of the as-synthesized
ZnO and Gd-doped ZnO samples with different con-
tents of Gd dopant were monitored by measuring the
photodegradation of methylene blue (MB) solution
under visible light radiation of a Xe lamp. Each 200 mg of
In this work, Gd-doped ZnO samples with differ-
ent concentrations of Gd dopant were synthesized by
the tartaric acid assisted precipitation method. The
structure, morphology and atomic vibration of pure
ZnO and Gd-doped ZnO samples were studied by
X-ray diffraction (XRD), Fourier transform infrared
spectroscopy (FTIR), Raman spectroscopy, transmis-
sion electron microscopy (TEM) and X-ray photo-
electron spectroscopy (XPS). The photocatalytic
properties of pure ZnO and Gd-doped ZnO samples
were investigated by photodegradation of methylene
blue (MB) under visible light of Xe lamp.
–5
the photocatalysts was suspended in 200 mL 1 × 10
M
MB solutions. The suspended solutions were stirred in
the dark condition for 30 min to stabilize the adsorp-
tion-desorption equilibrium of MB on the surface of
photocatalyst. Then, a visible light of Xe lamp was
turned on to irradiate on the suspended solution with
keeping the light on until 45 min completion. The
photodegradation of MB was examined for analytical
samples taken out from the photoreactor at regular
time intervals, centrifuged at 4000 rpm for 20 min to
remove photocatalyst. The concentration of MB solu-
EXPERIMENTAL
Zinc nitrate hexahydrate (Zn(NO ) · 6H O), gad- tion was measured by PerkinElmer, Lambda 25 UV-
3
2
2
olinium nitrate hexahydrate (Gd(NO ) · 6H O) as visible spectrometer at λ of 664 nm wavelength. The
3
3
2
max
zinc and gadolinium sources, tartaric acid (C H O ) decolorization efficiency (%) of MB by the photocat-
4
6
6
and sodium hydroxide (NaOH) were purchased from alyst was calculated by
Sigma-Aldrich Chemical Corporation and used with-
out further purification.
C − C
0
t
Decolorization efficiency
( )
%
=
×100, (1)
C0
Each 0.01ꢀmol Zn(NO ) · 6H O and 0–5 wt %
3
2
2
where C and C are the absorbance of MB solutions
Gd(NO ) · 6H O were dissolved in 50 mL C H OH
0
t
3
3
2
2
5
before and after visible light irradiation. In the end, the
degraded products of the photocatalytic system were
investigated by direct mass spectrometry (Agilent
G6545A Q-TOF LC/MS) using an electrospray ion-
solutions with 30ꢀmin stirring and mixed together
under continued stirring. Subsequently, 0.0100 mole
tartaric acid solution in 50 mL C H OH solvent was
2
5
added to the mixed solution at room temperature, and
followed by 20 mL of 1 M NaOH solution adding with
continued stirring for 30 min. The as-synthesized
white precipitates were filtered, washed by distilled
water and ethanol several times, dried at 80°C for 24ꢀh
and ground into fine powder. The 2.00 g fine powder
was put in an alumina crucible and calcined in air at
+
ization operating in the positive (ESI ) mode for the
treated MB. At the end of photocatalysis, the mass to
charge (m/z) ratio of the degraded products was also
investigated by mass spectroscopy.
RESULTS AND DISCUSSION
600°C for 2ꢀh.
The degree of crystallinity and phase of as-pre-
pared ZnO and Gd-doped ZnO samples were studied
by XRD as the results shown in Fig. 1. The XRD pat-
tern of pure ZnO without Gd dopant revealed five dif-
fraction peaks at 2θ of 31.78°, 34.42°, 36.27°, 47.55°
and 56.60° which were assigned to the (100), (002),
Phase and structure of ZnO and Gd-doped ZnO
samples were characterized by X-ray diffraction
(
XRD) on a Rigaku SmartLab X-ray diffractometer
equipped with CuK radiation ranging from 20° to 60°
α
at a scanning rate of 0.005 deg/s. The morphology of
ZnO and Gd-doped ZnO samples was recorded by
transmission electron microscopy (TEM) on a JEOL,
(
101), (102) and (110) planes of wurtzite hexagonal
ZnO (JCPDS no. 36-1451 [18]). The sharp diffraction
peaks in the XRD pattern of ZnO sample indicated
JEM 2010 TEM with LaB as electron gun at an accel-
6
eration voltage of 200 kV. The molecular vibration was that ZnO was highly crystallized in nature. Neverthe-
measured by Raman spectroscopy and Fourier trans- less, the XRD patterns of as-prepared 1, 3 and 5 wt %
form infrared (FTIR) spectroscopy. Raman spectra Gd-doped ZnO samples were still the same diffraction
–1
were operated in the wavenumber of 100–800 cm
patterns as the pattern of ZnO sample. The impurity
, Gd(OH) were not detected in
Yvon Raman spectrometer using a 50 mW and 514.5 nm these XRD patterns, indicating that Gd ions were
–1
with 0.1 cm resolution on a T64000 HORIBA Jobin phases such as Gd
O
2
3
3
3+
2+
wavelength Ar green laser. FTIR spectra were operated
uniformly substituted for Zn ions. The addition of
–1
in the wavenumber of 400–4000 cm on Bruker Ten- Gd ions to ZnO matrix had no effect in shifting the
sor 27 using KBr as a diluting agent. X-ray photoelec- XRD peaks of ZnO [15, 19]. They can be seen that the
tron spectroscopy (XPS) was carried out by an Axis increasing content of Gd dopant in ZnO matrix, the
Ultra DLD│Kratos–Kratos Analytical with a mono- diffraction peaks of Gd-doped ZnO were broadened.
chromatic AlK radiation (1486.6 eV) as a providing These led to reduce the particle size of Gd-doped ZnO
α
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 64 No. 12 2019

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SURISA SA-NGUANPRANG et al.
samples. All diffraction peaks of Gd-doped ZnO sam-
ples were slightly shifted towards smaller diffraction
angle due to the expansion of ZnO lattice, because the
(a)
3+
2+
radius of Gd ion (0.938 Å) is larger than that of Zn
ion (0.74 Å) [7, 15, 16, 20, 21]. The crystallite size (D)
of as-prepared ZnO and Gd-doped ZnO samples were
calculated by the Scherrer equation
5
3
1
0
% Gd
% Gd
% Gd
D = kλ/βhkl cos θ,
(2)
where k = 0.89, λ is the wavelength of CuK radiation
α
(
0.154056 nm), θ is the Bragg’s angle of X-ray diffrac-
tion peak of the (101) plane and β is the full width at
half maximum (FWHM) of the diffraction peak [7, 15,
1
9, 22]. The crystallite sizes were 53, 36, 32 and 30 nm
for ZnO, 1 wt % Gd-doped ZnO, 3 wt % Gd-doped ZnO
and 5 wt % Gd-doped ZnO, respectively. The crystallite
size was reduced due to the introduction of Gd ion and
creation of cationic vacancy, which in turn to reduce lat-
tice parameter and to increase a stress [15, 22].
% Gd
25
20
30
35
40
2θ, deg
45
50
55
60
According to group theory, wurtzite ZnO belongs
(b)
4
to the C space group with two formula units in a
6
v
primitive cell. At the central point of Brillouin zone,
group theory predicts the existence of the following
phonon modes
Γopt = A + 2B + E + 2E .
(3)
1
1
1
2
For optical modes, B is Raman silent. Both A and
1
1
E are polar and are split into transverse optical (TO)
5% Gd
1
and longitudinal optical (LO) phonons. A nonpolar
phonon mode with E symmetry has two frequencies:
2
3
1
0
% Gd
E
associated with oxygen atom and E associated
2L
2
H
with Zn sublattice [15, 23–25]. Among the optical
mode, A , E and E are Raman active. Fig. 2a shows
1
1
2
% Gd
Raman spectra of pure ZnO and 5 wt % Gd-doped
ZnO samples using 514.5 nm wavelength of an argon
green laser. They show five Raman peaks at 202, 330,
% Gd
31
–
1
3
4
82, 437 and 579 cm . The strong Raman peak at
–
1
30
32
33 34 35
θ, deg
36
37
38
37 cm is attributed to the ZnO nonpolar optical
2
phonons of E mode, the characteristic peak of
2
H
−1
wurtzite ZnO [13, 15, 23–25]. The peak at 382 cm is
associated with A (TO) which the first-order is also
Fig. 1. XRD patterns of 0–5 wt
%
Gd-
1
doped ZnO synthesized by a tartaric acid precipitation
optical mode of wurtzite ZnO [10, 12, 20–22]. The
small peak at 202 cm−1 is attributed to E2L which is the
second-order feature caused by multiphonon process
method over the 2θ range of (a) 20°–60° and (b) 30°–38°.
−1
−1
[
E
13, 15, 23–25]. The peak at 579 cm was assigned as shown in Fig. 2b. The strong absorption band at 426 cm
mode of ZnO nanoparticles and related to the for- was specified as the Zn–O stretching vibration of all
L
1
samples and certified the formation of hexagonal ZnO
2, 5, 7, 25, 27]. The FTIR band at 3013–3633 cm
mation of defects, such as zinc interstitial and oxygen
−1
−1
[
vacancy [13, 15, 23–25]. The 330 cm mode is related
to the E –E multiphonon scattering process. The corresponds to the O–H stretching vibration of physi-
2H
2L
cal adsorbed water on surface of samples [5, 7, 25, 27].
intensity of both E2H and E modes gradually
2L
3+
increased with increasing Gd concentration and was
In order to determine the surface composition and
chemical state of the sample, 5 wt % Gd-doped ZnO
attributed to the lattice distortion in ZnO matrix [26].
The FTIR spectra of pure ZnO and 5 wt % Gd- was characterized by XPS technique. Figure 3a shows
doped ZnO samples diluted with KBr at the ratio of a survey spectrum of 5 wt % Gd-doped ZnO which
1
4
: 40 were performed in the wavenumber range of contained Zn, O and Gd elements and was certified
00–4000 cm− at room temperature as the results that 5 wt % Gd-doped ZnO was composed of zinc,
1
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VISIBLE-LIGHT-DRIVEN PHOTOCATALYSIS of Gd-DOPED ZnO
a)
1603
(
5
% Gd doped ZnO
% Gd doped ZnO
0
1
00 200 300 400 500
60
700 800
–
1
Wavenumber, cm
(b)
5% Gd doped ZnO
0% Gd doped ZnO
4
00 800 1200 1600 2000 2400 2800 3200 3600 4000
–1
Wavenumber, cm
Fig. 2. Raman (a) and FTIR(b) spectra of pure ZnO and 5 wt % Gd-doped ZnO samples.
oxygen and gadolinium. The high-resolution XPS lytic surface [2, 5, 8, 28]. Furthermore, the Gd 3d
spectra of Zn 2p, O 1s and Gd 3d of 5 wt % Gd-doped spectrum consists of binding energy doublet located at
ZnO nanoparticles are shown in Figs. 3b–3d. The 1219.52 eV for Gd 3d and 1187.27 eV for Gd 3d ,
3
/2
5/2
XPS spectrum of Zn 2p shows the binding energy
3+
indicating the existence of Gd ions [26, 26, 29].
peaks centered at 1021.25 eV and 1044.34 eV which
3+
Hence, this spectrum further demonstrated that Gd
were assigned to the Zn 2p3/2 and Zn 2p of ZnO [2,
1/2
ions were successfully doped.
5
, 8, 28]. They certified that Zn mainly exists as the
2+
Zn chemical state of 5 wt % Gd-doped ZnO lattice
Figure 4 presents typical TEM images and SAED
[
8, 28]. Three fitted peaks of O 1s located at three patterns of the 0–5 wt % Gd-doped ZnO samples. A
binding energies of 530.19, 531.64 and 532.44 eV. They typical TEM image of ZnO sample presents nanopar-
were attributed to the crystalline lattice of oxygen con- ticles of pure ZnO phase with approximately 100 nm
taining in ZnO and the adsorbed oxygen on the cata- diameter. When Gd was doped to ZnO sample, the
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 64 No. 12 2019

1604
SURISA SA-NGUANPRANG et al.
(a)
(b)
0
150 300 450 600 750 900 1050 1200 1350 1016
Binding energy, eV
1024
1032
1040
1048
1056
Binding energy, eV
(d)
(c)
526
528
530
532
534
536 1180
1190
1200
1210
1220
1280
Binding energy, eV
Binding energy, eV
Fig. 3. XPS (a) survey spectrum and high-resolution XPS spectra (b–d) of Zn 2p, O 1s and Gd 3d of 5 wt % Gd-doped ZnO
sample, respectively.
products remained as nanoparticles. Moreover, the shows a steady decreasing trend with the increase of
particle size of products was deceased with the irradiation time, indicating that MB structure was
increase of Gd content from 1 to 5 wt %, due to the destroyed by the 5 wt % Gd-doped ZnO photocata-
inhibit growth process of ZnO crystallite. TEM images lyst, almost complete photodegradation of MB under
of 1, 3 and 5 wt % Gd-doped ZnO samples show a
number of nanoparticles with size distribution of 50–
visible light irradiation by 5 wt % Gd-doped ZnO pho-
tocatalyst within 45 min.
80, 40–50 and 20–30 nm, respectively. In order to fur-
ther investigate the structure of products, SAED pat-
The photocatalytic degradation of MB by undoped
terns appear as concentric rings of diffraction white and Gd-doped ZnO photocatalysts is shown in Fig. 6a.
spots of polycrystalline wurtzite structure. The d-spaces The concentration of MB was little reduced by pure
of diffraction planes were calculated, compared with ZnO phase under visible light illumination. But for the
those of the JCPDS file no. 36-1451, and can be presence of Gd-doped ZnO, a significant decrease in
indexed to the (100), (002), (101), (102) and (110)
planes of hexagonal ZnO.
the concentration of MB dye was detected. Within
5 min photocatalysis, the decolorization efficiencies
4
The photocatalytic activity of undoped and Gd-doped by ZnO, 1 wt % Gd-doped ZnO, 3 wt % Gd-doped
ZnO samples was investigated by monitoring photo- ZnO and 5 wt % Gd-doped ZnO were about 16, 96, 97
degradation of MB under visible light irradiation. Fig- and 100%, respectively. The 5 wt % Gd-doped ZnO
ure 5 shows the variation of absorbance versus wave-
length within different lengths of irradiation time for
photodegradation of MB solution by 5 wt % Gd-doped
ZnO photocatalyst. They can be seen that the MB
solution shows a strong maximum absorption at the
shows the highest photocatalytic activity. Evidently,
Gd dopant played the role in accelerating the photo-
catalytic degradation of MB dye.
The photocatalytic reaction for photodegradation
wavelength of 664 nm. The absorbance at 664 nm of MB by photocatalyst under visible light irradiation
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
Vol. 64
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2019

VISIBLE-LIGHT-DRIVEN PHOTOCATALYSIS of Gd-DOPED ZnO
a)
1605
(
(b)
2
00 nm 100 nm
(c)
(d)
100 nm
100 nm
Fig. 4. TEM images and SAED patterns of 0 (a), 1 (b), 3 (c) and 5 wt % (d) Gd-doped ZnO samples synthesized by a tartaric acid
precipitation method.
can be explained as a pseudo-first-order reaction
below.
0
min
lnc /c = kt,
(4)
1
5 min
0
t
30 min
5 min
where k is the rate constant, c and c are the spectral
4
0
t
intensities of MB solutions before and after visible
light irradiation and t is the irradiation time [7, 15, 16].
Figure 6b shows the relationship between ln(c /c ) and
o
t
the reaction time for photodegradation of MB by pho-
tocatalysts under visible light irradiation. The plot of
photocatalytic decolorization of MB was fitted to a
straight line, indicating that the photodegradation
strongly followed the peuso-first-order kinetics. The
calculated first-order rate constant values (k) for pho-
todegradation of MB by ZnO, 1 wt % Gd-doped ZnO,
3
00
400
500
600
700
800
Wavelength, nm
3
wt % Gd-doped ZnO and 5 wt % Gd-doped ZnO were
–1
respectively 0.0039, 0.0666, 0.0737 and 0.0982 min ,
certifying the increase of degradation rate of MB dye
by increasing of Gd dopant in ZnO.
Fig. 5. UV–visible absorption of MB in the solution con-
taining 5 wt % Gd-doped ZnO under visible light irradia-
tion.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 64 No. 12 2019

1606
SURISA SA-NGUANPRANG et al.
0
0
0
0
0
(a)
(a)
2
4
6
8
0
1
% Gd doped ZnO
% Gd doped ZnO
3% Gd doped ZnO
5% Gd doped ZnO
1
00
100
200
300
400
500
600
0
15
30
45
Mass to charge, m/z
Time, min
(b)
(b)
5
4
3
2
1
0
0% Gd doped ZnO
1
3
% Gd doped ZnO
% Gd doped ZnO
5% Gd doped ZnO
100
200
300
400
500
600
0
15
30
Time, min
45
Mass to charge, m/z
Fig. 6. Decolorization efficiency (a) and reaction kinetics
Fig. 7. Mass-spectra of (a) MB dye and (b) degraded prod-
ucts of MB dye photocatalyzed by 5 wt % Gd-doped ZnO
under visible light within 45ꢀmin.
(
b) for photodegradation of MB by 0–5 wt % Gd-doped
ZnO under visible light irradiation.
The degradation of MB by 5 wt % Gd doped ZnO
2C H N SCl + 51O → 2HCl + 2H SO
1
6
18
3
2
2
4
(5)
sample at t = 0 and 45 min was identified by direct
mass spectrometry (MS) in a positive mode as the
results shown in Fig. 7. Pure MB molecules has a sig-
nal at m/z = 284 corresponding to methylene blue
molecular ions [8, 29]. At the end of photocatalysis,
the signal shows m/z at 128, 168, 234, 274, 310, 340,
+
6HNO + 32CO +12H O.
3 2 2
2
−
−
3
Formation of SO , NO and CO from the
4
2
degraded MB solution indicated the mineralization of
the dye [8, 30, 31].
3
80, 421, 446, 486, 552 and 592 due to the oxidation of
Figure 8 shows a schematic diagram for photodeg-
−
2
●
●
●
MB dye by O and OH radicals. The OH radical radation by Gd-doped ZnO photocatalyst. Under vis-
−
+
ible light irradiation, photo-induced electrons (e ) in
attacked the C–S =C functional group in MB by
●
the valence band (VB) were excited to the conduction
forming sulfoxide (RS(=O)R'). The second OH rad-
+
band (CB) with the generation of holes (h ) in the VB
ical attacked the sulfoxide to produce sulfone
3+
(
RSO R') and caused the dissociation of two benzenic for Gd-doped ZnO sample. The Gd released photo-
2
induced electrons to the adsorbed O via an oxidation
rings. Sulfone then gave rise to sulfonic acid (RSO H)
2
3
process and produced a superoxide anion radical
which was further oxidized to sulphate ion. This pro-
−
2
●
4+
cess could form ring cleavage products, and even min-
(
O ) [5, 7, 12, 32]. The Gd acted as an effective
eralization to CO and H O [30, 31]. The complete
2
2
electron scavenger to trap photo-induced electrons in
mineralization of the molecule can be written as fol- CB of the Gd-doped ZnO photocatalyst and inhibited
lows. the electron–hole recombination process in Gd-
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
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VISIBLE-LIGHT-DRIVEN PHOTOCATALYSIS of Gd-DOPED ZnO
O2
1607
Gd4+
O2
e– e– e– e–
Gd3+
CB
CO + H O
MB
2
2
OH
h+ h+ h+ h+
Gd-doped ZnO
VB
–
OH /H O
2
Fig. 8. Schematic diagram for photodegradation of Gd-doped ZnO photocatalyst.
doped ZnO sample [5, 7, 12, 32]. Meanwhile, the
photoinduced hole in Gd-doped ZnO was also readily
2. N. Güya and M. Özacar, J. Photochem. Photobio.
A 370, 1 (2019).
−
scavenged by immanent H O/OH to yield hydroxyl
3. Y. N. Rane, D.A. Shende, M.G. Raghuwanshi, et al.,
2
Optik 179, 535 (2019).
−
2
●
●
●
(
OH) radical. These highly reactive O and OH
4
5
. Z. Ye, L. Kong, F. Chen, et al., Optik 164, 345 (2018).
. V. H. T. Thi and B. K. Lee, Mater. Res. Bull. 96, 171
as strong oxidizing agents were responsible for
destruction of MB structure and transforming MB
into mineral acids, CO and H O as final products
(
2017).
2
2
6. M. A. Lahmer, Appl. Surf. Sci. 457, 315 (2018).
[
5, 7, 8, 12, 32].
7
. S. Bhatia, N. Verma, and R. Kumar, J. Alloy. Compd.
7
26, 1274 (2017).
8
. A. Phuruangrat, S. Siri, P. Wadbua, et al., J. Phys.
CONCLUSIONS
In summary, 0–5% Gd-doped ZnO nanoparticles
Chem. Solid 126, 170 (2019).
9. E. P. Simonenko, N. P. Simonenko, I. A. Nagornov,
et al., Russ. J. Inorg. Chem. 62, 1415 (2017).
were successfully synthesized by a tartaric acid precip-
itation method. The structure, morphology and pho- 10. A. S. Chizhov, N. E. Mordvinova, M. N. Rumyantsev,
et al., Russ. J. Inorg. Chem. 63, 512 (2018).
this research. The experimental results demonstrated 11. E. P. Simonenko, N. P. Simonenko, I. A. Nagornov,
that the as-synthesized 5 wt % Gd-doped ZnO has the
et al., Russ. J. Inorg. Chem. 63, 1519 (2018).
tocatalytic activity of the products were investigated in
highest photocatalytic activity for degradation of 12. E. Cerrato, C. Gionco, I. Berruti, et al., J. Solid State
methylene blue under visible light irradiation.
Chem. 264, 42 (2018).
3. D. R. Kumar, K. S. Ranjith, and R. T. R. Kumar, Optik
54, 115 (2018).
4. H. Li, W. Li, F. Wang, et al., Appl. Surf. Sci. 427, 1046
2018).
5. O. Yayapao, T. Thongtem, A. Phuruangrat, and
S. Thongtem, Mater. Sci. Semicond. Process. 39, 786
2015).
6. X. Luo, G. Zhu, J. Peng, et al., Appl. Surf. Sci. 351, 260
2015).
7. X. Q. Cheng, C. Y. Ma, X. Y. Yi et al., Thin Solid Films
15, 13 (2016).
8. Powder Diffraction File, JCPDS-ICDD (2001).
. P. Shandilya, D. Mittal, M. Soni, et al., Journal Clean. 19. D.K. Sharma, K.K. Sharma, V. Kumar, et al., J. Mater.
Prod. 203, 386 (2018). Sci. 27, 10330 (2016).
1
1
FUNDING
1
(
We wish to thank the Thailand’s Office of the Higher
Education Commission for providing financial support
through the Research Professional Development Project
under the Science Achievement Scholarship of Thailand
1
(
1
(
SAST).
(
1
6
REFERENCES
1
1
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 64 No. 12 2019

1608
SURISA SA-NGUANPRANG et al.
2
0. P. Sudhagar, A. Devadoss, K. Nakata, et al., J. Electro- 26. R. Kumar, A. Umar, G. Kumar, et al., Ceram. Int. 41,
chem. Soc. 162, H108 (2015).
7773 (2015).
2
2
2
3
7. G. Vijayaprasath, R. Murugan, Y. Hayakawa, et al.,
2
1. Z. M. El-Bahy, A. A. Ismail, and R. M. Mohamed, J.
J. Luminescence.178, 375 (2016).
Hazard. Mater. 166, 138 (2009).
8. Y. Liang, N.Guo, L. Li, et al., RSC Adv. 5, 59887
2
2
2
2
2. N. Aggarwal, K. Kaur, A. Vasishth, et al., J. Mater. Sci.
(2015).
2
7, 13006 (2016).
9. A. Hao, M. Ismail, S. He, et al., Mater. Sci. Eng. B 229,
3. A. Phuruangrat, S. Thongtem, and T. Thongtem, Ma-
86 (2018).
ter. Design 107, 250 (2016).
0. V. Borker, R. Karmali, and K. Rane, Eur. Chem. Bull.
4. T. Thongtem, A. Phuruangrat, and S. Thongtem, Ce-
3, 520 (2014).
ram. Int. 36, 257 (2010).
31. Hu. Wang, P. Zhou, R. Guo, et al., Catal. 8, 107 (2017).
5. N. Ekthammathat, S. Thongtem, T. Thongtem, and 32. R. M. S. Rayes, Y. Kumar, M. A. Cortes-Jácome, et al.,
A. Phuruangrat, Powder Tech. 254, 199 (2014). Phys. Status Solidi A 212, 170022 (2017).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY
Vol. 64
No. 12
2019