A novel composite of α-MoO3/BiVO4 for triethylamine selective detection

Article abstract of DOI:10.1039/c9nj06198c

One-dimensional α-MoO₃ nanorods were synthesized by a hydrothermal method and BiVO₄ nanoparticles were grown directly onto the α-MoO₃ nanorods using a simple metal organic decomposition process in order to construct an α-MoO₃/BiVO₄ composite with a heterojunction, for the fabrication of a rapid response triethylamine (TEA) sensor. The morphology and structure of the composite were characterized via various spectral techniques and the sensing properties of the sensor for TEA were investigated via resistance measurements. The results showed that the response of the 16Mo/Bi composite to 20 ppm TEA was 1.86 times and 15 times higher than those of α-MoO₃ and BiVO₄, respectively, at an optimum operating temperature of 125 °C. The enhancement can be ascribed to the existence of a heterojunction between α-MoO₃ and BiVO₄, creating an additional barrier at the interface of the heterojunction, and this increases the resistance of the composite in air and decreases the resistance in TEA, thus enhancing the response of the composite to TEA.

Full text of DOI:10.1039/c9nj06198c

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Fan, J. Guo, R. Luo, D. Li and A. Chen, New J. Chem., 2020, DOI: 10.1039/C9NJ06198C.
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ISSN 1144-2546
PAPER
Chechia Hu, Tzu-Jen Lin et al.
Yellowish and blue luminescent graphene oxide quantum dots
prepared via a microwave-assisted hydrothermal route using
H2O2 and KMnO4 as oxidizing agents
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Novel composite of α-MoO3/BiVO4 for Triethylamine selective
detection
Received 00th January 20xx,
Accepted 00th January 20xx
Shouli Baia, Jingyi Hana, Xiangxiang Fanb, Jian Guoa,*, Ruixian Luoa, Dianqing Lia,*, Aifan Chena
DOI: 10.1039/x0xx00000x
The one-dimensional α-MoO3 nanorods were synthesized by hydrothermal method and then BiVO4 nanoparticles were
grown directly on α-MoO3 nanorods using a simple metal organic decomposition process to construct the α-MoO3/BiVO4
composite with heterojunction for fabrication of a rapid response sensor to triethylamine (TEA). The morphology and
structure of the composite were characterized by various spectral techniques and the sensing properties of the sensor to
TEA were investigated by resistance measurement. The results showed that the response of 16Mo/Bi composite to 20
ppm TEA is 1.86 times and 15 times higher that of α-MoO3 and BiVO4 at an optimum operating temperature of 125 °C,
respectively. The enhancement can be ascribed to the existence of heterojunction between α-MoO3 and BiVO4, which
creates an additional barrier at interface of heterojunction increasing the resistance of the composite in air and decreasing
the resistance in TEA, thus enhances the response of the composite to TEA.
with other metal oxide semiconductors to form
a
heterojunction is an effective method.10 Since potential energy
barrier height at the heterojunction interface is related to the
amount of oxygen adsorbed on the surface of material, it can
be effectively adjusted by reconstructing the Fermi level
between the two semiconductors in the heterojunction.11 The
development of new material forever is research frontier for
various application fields. As a photocatalyst, monocline BiVO4
Introduction
Triethylamine (TEA) is a dangerous volatile organic
compound (VOCs) with toxicity and irritation, which comes
from rotten seafood and has great harm to the environment
and human health. Semiconductor metal oxides based
2
4
chemical gas sensors, such as ZnO1, V2O5 , CuO3，Fe2O3 , and
5
CoFe2O4 , have attracted wide attention and obtained
has
been
widely
investigated
and
applied
in
important application in monitoring TEA vapour to identify
seafood freshness due to their ease of manufacture, low cost,
and high sensitivity. Transition metal oxide of α-MoO3, as an
n-type wide band gap semiconductor is considered to be an
important multifunctional material widely used in the fields of
catalysis, energy storage and gas sensors.6-8 In the gas sensor
field, α-MoO3 can dissociate the C-N bond of the organic
amine and specifically interact with the TEA molecule at the
desired temperature. Sui et al.9 prepared a better sensitive
TEA sensor with a layered flower structure MoO3 by
solvothermal method and acquired the response of 416 to 100
ppm TEA at 250°C, but the sensor had a longer recovery time
up to 1283 s. In order to further improve the sensing
performance of single metal oxides to TEA, combining α-MoO3
photoelectrochemical water splitting and photodegradation of
pollutant driven by sunlight due to its appropriate band gap
(2.4 eV) and high photocatalytic activity. However, as a kind of
gas sensing material, BiVO4 is rarely reported and still in the
early investigation stages to date12-14, but it has better
compatibility with other metal oxides. In this study, α-MoO3
nanorods were firstly synthesized by hydrothermal method.
Monoclinic BiVO4 was selected as second semiconductor oxide
to form α-MoO3/BiVO4 n-n heterojunction via metal organic
decomposition method for improving the sensitivity of α-MoO3
to TEA and expanding the application of BiVO4 in the sensor
field. For comparison, The MoO3 based TEA sensors reported
to date were listed in following Table 1.
a. State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of
Environmentally Harmful Chemicals Analysis, Beijing University of Chemical
Technology, Beijing 100029, China.
Experimental section
b Zhejiang Province Key Laboratory of Smart Management & Application of Modern
Agricultural Resources, Huzhou University, Huzhou 313000, China
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
Synthesis of α-MoO3 nanorods
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were observed by scanning electron microscoVpieyw A(rStiEclMe O)nlinine
conjunction with energy dispersive X-ray spectrometer (EDS)
and transmission electron microscopy (TEM, JEM-2010). The
solid-state UV–vis absorption spectrum was performed via a
spectrometer equipped with an integrating sphere attachment
(Shimadzu UV-3000).
DOI: 10.1039/C9NJ06198C
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Measurements of gas sensing properties
The sample powder was dispersed in the ethanol to form
a paste and then the paste was painted on the ceramic tube
with an Au electrode. After aging the prepared sensors at 100
◦C for one week, the responses of the samples in TEA vapor at
various concentrations were conducted on a static system
(JF02E, Guiyan Jinfeng Technology Co Kunming, China). The
response of the n-type semiconductor sensor to reducing gas
is defined as Ra / Rg, where Ra represents the resistance of the
sensor in the air and Rg represents the resistance of the sensor
in the test gas.
Fig. 1 Schematic diagram of α-MoO3/BiVO4 composite synthesis process
All the chemicals involved were analytically pure and
can be used directly without further purification. The α-MoO3
nanorods were synthesized by typical method.15 0.494 g of
ammonium molybdate ((NH4)6Mo7O24•4H2O,Merck,99%)
powder and 1 mmol of cetyltrimethylammonium bromide
(CTAB,Merck,99%) were dissolved in deionized water (10 mL)
to form transparent solution, and then 10 ml of nitric
acid(HNO3, Aladdin,65% ～ 68%) (2.2 M) was added to the
above solution. This aqueous solution was transferred to a 50
Results and discussion
Phase structure and morphology of sensing
material
o
mL Teflon-lined stainless-steel autoclave and kept it at 180 C
for 20 h. The light gray precipitates were harvested by
centrifugation, washed with ethanol and dried at 80 °C
overnight. Finally, the obtained product was calcined at 500 oC
for 2 h to obtain α-MoO3 nanorods.
Crystal information of all the materials was investigated by
XRD technique. The 2θ values of MoO3 at 12.76°, 23.33° and
25.70° can be ascribed to (020),(110) and (040) crystal planes
of standard the orthorhombic phase MoO3 (JCPDS No. 05-
0508). The XRD pattern of pure BiVO4 conforms to monoclinic
Preparation of α-MoO3/BiVO4 composites
0.14
M
of Bismuth nitrate pentahydrate (Bi
(NO3)3 · 5H2O, Aladdin, ≥ 99%) and 0.14 M of vanadium
acetylacetonate(C10H17O5V,Aladdin, 95%) were added to 3 mL
of 2-methoxy ethanol(C3H8O2, Aladdin, 99%), followed by
ultrasound for 2 min to obtain a light green solution. After
slowly instilling 100 μl of the above BiVO4 precursor solution in
0.05 g of α-MoO3, it was calcined at 500° for 2 h to obtain α-
MoO3/BiVO4 composite. By adjusting the concentration of
BiVO4 precursor solution,
a
series of α-MoO3/BiVO4
composites with different molar ratios of α-MoO3/BiVO4 were
prepared and labeled as 8Mo/Bi, 12Mo/Bi, 16Mo/Bi and
18Mo/Bi. Fig. 1 depicts the schematic illustration of the
preparation process.
Characterization
Crystallographic information for the samples were examined
by X-ray diffraction (XRD, Shimadzu XRD-600 diffractometer,
copper Kα radiation with λ = 0.15406 nm). The surface
element composition and element valence state of the
samples were performed by X-ray photoelectron spectroscopy
(XPS, VG ESCALAB-MK). The morphology and composition
Fig.2 XRD patterns of α-MoO3, BiVO4, and α-MoO3/BiVO4 composite.
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between α-MoO3 and BiVO4 effectively reduces tVhieewfAortricbleidOdnleinne
band width of α-MoO3, thereby further DimOpI:r1o0v.1i0n3g9/tCh9eNsJ0e6n1s9i8nCg
characteristics of the semiconductor metal oxide.
XPS analysis was performed to determine the chemical
composition and elemental valence of 16Mo/Bi composite. Fig.
5a demonstrates that Mo, O, Bi, V and C exist in BiVO4/ MoO3
composite. To be specific, deconvolution of Mo 3d spectrum
(Fig. 5b) depicts that the binding energy of 236.1 eV and 233.0
eV, corresponding to Mo 3d 5/2 and Mo 3d 3/2 derived from
Mo6+ in MoO3.20 In addition to the characteristic mode of Mo6+
ions, the obvious binding energies of Mo 3d 5/2 at 232.5 eV
and Mo 3d 3/2 at 235.4 eV were also observed, which
corresponds to Mo5+ ions by comparison with the reported
standard values.21 The O 1s (Fig.6c) peak with values of 530.65
eV is assigned to the crystal lattice oxygen (Mo-O、Bi-O-Bi),
the peak at 531.6 eV belongs to the surface-adsorbed oxygen
on the composites, and the peak at a binding energy of 532.8
eV is ascribed to the −OH or water molecules on the surface of
the BiVO4/MoO3 composite. The peaks of Bi 4f 5/2 at around
164.8 eV and Bi 4f 7/2 at 159.44 eV can be assigned to Bi3+.
The XPS signals of V 2p are observed at binding energies of
524.36 eV and 516.85eV (Fig. 5e), which ascribes to the V 2p
1/2 and V 2p 3/2 states of the tetrahedral VO43− group.18This
demonstrates the successful synthesis of the BiVO4/MoO3
composites.
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Fig. 3 (a-c) SEM images of α-MoO3, 16Mo/Bi composite and BiVO4; (d, e) TEM
and HRTEM images of 16Mo/Bi composite; (f) EDX spectra of 16Mo/Bi composite
crystal phase of JCPDS: 14-0688.16 The MoO3/BiVO4 composite
peaks are also a superposition of two substance peaks. In
addition, the perfect formation of BiVO4/MoO3 composite is
confirmed by no excessive diffraction peak and no peaks shift.
The SEM,HRTEM and TEM images are shown in Fig 3 to
reveal the microscopic morphology of the prepared α-MoO3,
BiVO4 and 16Mo/Bi composite. Fig 3a and 3c show α-MoO3
nanorods with a width of approximately 200 nm and BiVO4
nanoparticles with
a size of approximately 100 nm,
respectively. After BiVO4 nanoparticles grew on MoO3
nanorods (Fig.3b), the BiVO4/MoO3 composite was still
nanorods. Fig. 3e reveals that two typical lattice spacing are
0.38 nm and 0.31 nm, corresponding to the (110) plane of α-
MoO3 and the (121) plane of BiVO4, respectively.17,18 It can be
seen that the BiVO4 nanoparticles have uniformly coated on
the surface of MoO3 nanorods and confirmed the formation of
heterojunction at interface between BiVO4 and MoO3. The
corresponding TEM image is shown in Fig.3d. Additionally,
from the survey EDS spectrum (Fig. 3f), O, Mo, Bi and V
elements can be detected for the Mo/Bi composite with atom
ratio of 16:1.
Gas sensing properties and mechanism
Fig. 6a shows the dependence of the responses of the
MoO3, BiVO4, 16Mo/Bi to 20 ppm TEA on the operating
temperature. All sensors show an "increase - maximum -
decrease" trend. It can be observed that all response values
increase with increasing operating temperature, and 16Mo/Bi
based sensor reveals the highest response of 64.5 to 20 ppm
TEA, which is 1.84 and 15 times higher than that of MoO3 and
BiVO4, respectively at 125 ◦C. As the operating temperature
increases further, the response decreases rapidly because the
adsorbed gas molecules tend to escape from the surface of the
material before the reaction occurs.22 Fig. 6b shows the
response time curves of Mo/Bi composites with different
molar ratios to 20 ppm TEA at the operating temperature of
125°C. It can be observed that these composites show typical
response curves, and the response is the highest for composite
The band gap energy of the samples analyzed by UV-vis
characterization is shown in Fig 4, and equation (1) is used to
estimate the bandgap energy.19
(α Ephoton)n=K(Ephoton-Eg)
(1)
In which, α, K and Ephoton represent absorption coefficient,
constant and discrete photo energy, respectively. The value of
n is related to whether the band gap of the semiconductor is a
direct band gap or an indirect band gap. The orthorhombic
structure α-MoO3 and the monoclinic BiVO4 are direct band
gap semiconductors, so the substitution value of n in the
formula (1) is 2. It can be observed from Fig. 4 that the main
light absorption edge of α-MoO3 appears at 440 nm, and the
corresponding band gap energy value is estimated to be about
3.05 eV, while the light absorption edge of pure BiVO4 is about
525 nm, the corresponding bandgap energy value is about 2.43
eV, which is very close to the values reported in literature. The
absorption edge of 16Mo/Bi composite is between α-MoO3
and BiVO4, and the corresponding band gap energy is also
between two pure semiconductors (2.62 eV), as shown in fig 4.
This confirms that the formation of the heterojunction
Fig. 4 (a, b) UV-Vis absorption spectra of α-MoO3, BiVO4 and 16Mo/Bi composite
This journal is © The Royal Society of Chemistry 20xx
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Fig. 5 XPS spectra: (a) full survey of α-MoO3/BiVO4 composite, (b) Mo 3d, (c) O 1s,
(d) Bi 4f and (e) V 2p.
Fig. 6 (a) Responses of α-MoO3, BiVO4 and 16Mo/Bi composite at different
operating temperature to 20 ppm TEA; (b) Transient responses of α-MoO3, BiVO4
and α-MoO3/BiVO4 composites with different molar ratio to 20 ppm TEA; (c)
Response-recovery time of α-MoO3, BiVO4 and 16Mo/Bi composite to 20 ppm
TEA; (d) Response of α-MoO3, BiVO4 and 16Mo/Bi composite to 20 ppm different
gases at 125 oC
with Mo/Bi molar ratio of 16:1. The response time of BiVO4,
pure MoO3 and 16Mo/Bi composite to 20 ppm TEA is shown in
Fig. 6c. It can be seen that the response and recovery time of
the 16Mo/Bi composite-based sensor are 15 s and 110 s,
respectively. The longer recovery time mainly is due to the
strong interaction between the surface of α-MoO3 and TEA,
thus resulting in a very slow rate of desorption26.
good line relationship between TEA concentration and
response value. The response values are 22.43, 40.70, 52.78,
60.6 and 70.79, respectively, corresponding to 5, 15, 20, 25, 30
ppm TEA at same operating temperature of 125 °C. To further
acquire the varying of transient response with gas
concentration, the transient response (S (t)) were simulated
according to the Langmuir–Hinshelwood gas-solid phase
reaction equation:29
Selectivity is a need to be improved indicator for metal
oxide semiconducting gas sensor. Good selectivity reflects the
sensor’s interference capability and can specifically detect
certain target gases.Fig.6d shows the responses of the two
pure oxides and the optimum composite based sensors to 20
ppm different VOCs at operating temperature of 125°C. The
results reveal that the 16Mo/Bi based sensor exhibits the
highest response of 63.56 that are higher than pure MoO3
(35.1) and BiVO4 (4.22) based sensors for 1.81 times and 15
times, respectively. From Fig. 6d, it can also be seen that the
16Mo/Bi based sensor shows higher response to TEA than n-
butanol, while to methanol, toluene, formaldehyde and
acetone almost no response. Such good selectively may be
ascribed to the bond energies difference for various VOCs. The
bond energy data of TEA(C-N), n-butanol/methanol (O-H),
toluene(C=C), formaldehyde (C=O) and acetone (C=O) are 307,
458.8, 610.3 and 798.9 kJ/mol, respectively. These data
indicate that the reducibility of TEA is much higher than that of
other VOCs due to its lower C-N bond energy, that is, TEA is
the most easily oxidized compared with other VOCs vapours,
leading to the highest response. Besides, the different
materials to different gases have different optimum operating
temperatures, because the oxygen adsorption and the sensing
reaction are temperature-dependent. So, the selectivity of the
sensor can also be adjusted by operating temperature.
However, to deeply elucidate the mechanism of selectivity
needs still further study.
S (t) = Smax(1 - e-k·Ca·t
)
(2)
Where Smax represents the maximum response, k represents
Fig 7a shows the transient responses for α-MoO3, BiVO4
and 16Mo/Bi composites and exhibits the change of response
with gas concentration, in which the 16Mo/Bi composite has
the best ratio to TEA gas at different concentrations (5-25 ppm)
at 125 °C. From Fig 7a, the prepared 16Mo/Bi composite has
Fig. 7 (a) The transient response curve of the α-MoO3 ，BiVO4 and 16Mo/Bi samples
based sensors to TEA concentration range from 5 ppm to 25 ppm at a working
temperature of 125 oC; (b) transient resistances of α-MoO3 and 16Mo/Bi samples to
different concentration TEA (5-25 ppm) at 125oC;(c) Experimental and fitted transient
responses of sensor based on the 16Mo/Bi composite to different concentrations of
TEA at 125 ◦C.
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Table 1 Response summarization of MoO3 based TEA sensors reported in the literature and the work
Materials
Concertration (ppm)
Temperature ( oC)
Response (Ra/Rg)
Res/Ret time
(s)
Refs
Cr-doped α-MoO3 nanorods
α-MoO3/PAIN
3D flower-like a-MoO3
a-MoO3 nanorods
TEA(100ppm)
TEA(100ppm)
TEA(100ppm)
TEA(100ppm)
TEA(10ppm)
200
20
250
300
260
150.25
22.6
416
101.74
75
7/80
24
25
12
26
27
35/82.42
3/1283
4/88
MoO3nanorods/RuO2
Nanoparticles
2/10
MoO3/BiVO4 nanorods
TEA(20ppm)
125
64.5
15/110
This
work
indicating that the response rate of the composite to TEA was
the surface rate constant and Ca represents the initial gas much higher. Generally, detection limit (DL) is defined as the
concentration. The transient resistances of the α-MoO3 ， lowest concentration at which the response is different from the
BiVO4 and 16Mo/Bi composite to different concentrations of noise signal, which is three times the standard deviation of the
TEA (5-25 ppm) at 125oC are shown in Fig. 7b. Fig. 7c reveals noise. The result indicates that the detection limit of the
that the actual response curves of the 16Mo/Bi composite can 16Mo/Bi composite based sensor (0.041 ppm) is lower than that
well conform to the Langmuir–Hinshelwood model, which of the pure α-MoO3 based sensor (0.679 ppm).
indicates the single molecular layer adsorption of TEA on the
composite .
Previous studies have shown that the formation of
heterojunction at the interface of two metal oxides plays a
Exploring the linear relationship between gas significant part in improving the sensing performance of
concentrations and sensing response facilitates the direct semiconductor.28,30 Fig. 9 shows the gas sensing sketch map of
acquisition of the concentration of the test gas from the the α-MoO3/BiVO4 composite in air and in TEA. When MoO3
sensitivity response value, thereby facilitating the practical and BiVO4 start to contact each other, since MoO3 has a
application of the sensor. Fig. 8 shows the sensor response of smaller work function (4.33 eV) 31,32 compared with BiVO4(5.3-
α-MoO3 and 16Mo/Bi composite as a function of TEA 5.27 eV)33, electrons flow from MoO3 to BiVO4 until their Fermi
concentration, and the linear trend of pure MoO3 and 16Mo/Bi energy levels are equal, forming an n-n heterojunction
composite can be observed. The slope of the straight line of between MoO3 and BiVO4. Meanwhile, the band-bending at
16Mo/Bi composite was higher than that of pure MoO3,
heterojunction interface results in the increase of the potential
energy barrier of interface. Compared to pure MoO3, the
composite sensor exhibits additional low resistance in TEA gas
and additional high resistance in air. Thence, the gas response
is significantly improved. The gas sensing process is shown as
follows: when MoO3/BiVO4 composite was exposed to the air
at 125 °C (Fig.9a), oxygen molecules in the air adsorbed on the
surface of the composite, trapping electrons from the metal
oxides and producing adsorbed oxygen ions, resulting in
increased resistance. Once the composite was exposed to the
TEA (Fig. 9b), since TEA molecule is less electronegative than
–
oxygen ion, the TEA reacted with the adsorbed oxygen ion (O2 )
on the surface of the composite to release the electrons back
into the composite. The release of electrons reduced the
depletion layer at the interfaces of two oxides, causing in a
reduction in the resistance (Rg) of the composite in the TEA.
Therefore, the response (Ra/Rg) of the 16Mo/Bi based sensor
to TEA gas is significantly enhanced, the relevant reaction
equations were shown in following: 34-36
Fig.
8 Based on α-MoO3 and 16Mo/Bi composite sensor: (a) linear relationship
between response and concentration and (b) double logarithmic coordinate fitting
response curve with concentration and corresponding detection limits.
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and Fundamental Research Funds for the CentraVlieUwnAirvticelersOitnilienes
(12060093063) and Zhejiang provincial natural science
foundation （LQ20F010001）.
DOI: 10.1039/C9NJ06198C
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Notes and references
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Fig. 9 (a) Schematic diagram of α-MoO3 and BiVO4 semiconductor energy band
structures in air (b) Schematic diagram of α-MoO3 and BiVO4 semiconductor
energy band structures in TEA (c) Schematic diagram of the three-dimensional
structure of MoO3/BiVO4 and changes in the depletion layer
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O2 (ads) + e- → O2– (ads)
<150 oC
(3)
4 N (C2H5)3 + 43 O2− →30 H2O+ 4NO2 + 24 CO2 + 43 e−
(4)
Conclusions
α-MoO3 nanorods were synthesized by hydrothermal
method, then BiVO4 nanoparticles were grown on α-MoO3
nanorods by metal organic decomposition method to
construct a n-n heterostructure composite. The as-fabricated
sensor based on 16Mo/Bi composite exhibits the highest
response (64.5), better selectivity and rapid response (15 s) to
20 ppm TEA at 125 ℃ . The existence of n-n heterojunction
MoO3-BiVO4 is considered to be mainly responsible for the
enhanced gas sensing performance of the composite.
Considering the simple synthesis process of MoO3/BiVO4 and
excellent gas sensing properties, the composite will be
promising candidate for TEA sensor applications.
Conflicts of interest
There are no conflicts to declare.
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Acknowledgements
This work was supported by the National Key R&D Program of
China (2016YFB0301600) and National Natural Science 28 D. Ju, H. Xu, X. Qi, H. Gong, Z. Qiu, G. Jing, J. Zhang, B.
Cao,Sensors & Actuators B Chemical 2015, 215, 39-44.
Foundation of China (Grant Nos. 21627813, and 51772015)
6 | J. Name., 2012, 00, 1-3
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Journal Name
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DOI: 10.1039/C9NJ06198C
Novel composite of α-MoO3/BiVO4 for Triethylamine
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selective detection
Shouli Baia, Jingyi Hana, Xiangxiang Fanb, Jian Guoa,*, Ruixian Luoa, Dianqing Lia,*, Aifan Chena
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a. State Key Laboratory of Chemical Resource Engineering, Beijing Key
Laboratory of Environmentally Harmful Chemicals Analysis, Beijing University
of Chemical Technology, Beijing 100029, China
b. Zhejiang Province Key Laboratory of Smart Management & Application of
Modern Agricultural Resources, Huzhou University, Huzhou 313000, China
The new gas sensing material of BiVO4 modified MoO3 was synthesized for the first
time by the combination of hydrothermal and metal organic decomposition.
Compared with the original MoO3, the 16Mo/Bi composite has a significant
improvement in the sensing performance of triethylamine, indicating the new
α-MoO3/BiVO4 composite with n-n heterojunction is a promising sensing material for
the detection of toxic TEA gases.
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