Accepted Manuscript Controlled synthesis of manganese tungstate nanorods for highly selective NH3 gas sensor Do Dang Trung, Nguyen Duc Cuong, Khuc Quang Trung, Thanh-Dinh Nguyen, Nguyen Van Toan, Chu Manh Hung, Nguyen Van Hieu PII:
S0925-8388(17)33918-X
DOI:
10.1016/j.jallcom.2017.11.161
Reference:
JALCOM 43854
To appear in:
Journal of Alloys and Compounds
Received Date: 13 July 2017 Revised Date:
23 September 2017
Accepted Date: 12 November 2017
Please cite this article as: D.D. Trung, N.D. Cuong, K.Q. Trung, T.-D. Nguyen, N. Van Toan, C.M. Hung, N.V. Hieu, Controlled synthesis of manganese tungstate nanorods for highly selective NH3 gas sensor, Journal of Alloys and Compounds (2017), doi: 10.1016/j.jallcom.2017.11.161. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Controlled synthesis of manganese tungstate nanorods for highly selective NH3 gas sensor
1
RI PT
Do Dang Trung1,*, Nguyen Duc Cuong2,3,†, Khuc Quang Trung1, Thanh-Dinh Nguyen4, Nguyen Van Toan5, Chu Manh Hung5, Nguyen Van Hieu5,‡
Department of Basics Science, University of Fire Fighting and Prevention, 243 Khuat Duy Tien, Thanh Xuan, Hanoi, Vietnam
4
Faculty of Hospitality and Tourism, Hue University, 22 Lam Hoang, Hue City, Vietnam
M AN U
3
College of Sciences, Hue University, 77 Nguyen Hue, Hue City, Vietnam
SC
2
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, V6T 1Z1, Canada 5
International Training Institute for Materials Science, Hanoi University of Science and
Abstract: In this paper, single-crystalline MnWO4 nanorods were prepared through a facile single-step hydrothermal approach and used for gas sensing. The morphology and phase of the
RI PT
products were characterized in detail through transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and elemental dispersive spectrum analyses. Results showed that the as-prepared MnWO4 nanorods possess uniform shape with their length
SC
of 250-300 nm and width of 20-30 nm. The nanorods were used to fabricate sensors for detecting reducing gases such as NH3, H2 and CO and evaluate gas sensing properties. The sensors exhibit
M AN U
not only good response and fast response time, but also almost full recovery and good stability, to NH3 gas.
AC C
EP
TE D
Keywords: Gas sensors; MnWO4; Nanorods; Hydrothermal
2
ACCEPTED MANUSCRIPT 3
1. Introduction Scholars have focused on controlling the chemical composition and structure of nanomaterials to explore new physical and chemical properties with promising applications in
RI PT
electronics, magnetics, photonics, sensors, and catalysis [1–4]. Many mixed metal oxides with indefinite nanostructures have been synthesized and investigated because their excellent behavior depends not only on the complex morphology but also on the crystallinity of particles in the
SC
microarchitectures [5]. Among various mixed metal oxides, metal tungstate complexes are important inorganic functional materials with potential applications in various fields [6]. In
M AN U
particular, novel complexes, such as FeWO4, NiWO4, PbWO4 and MnWO4, SrWO4 have been widely used to fabricate white-emitting diodes [7], magnetic devices [8], electrodes [9], scintillators [10], humidity sensors [11] and photocatalyst [12,13]. The binary metal oxide MnWO4, an important metal tungstate, has gained increasing
TE D
attention because of its application in supercapacitors [14], humidity sensors [15], photoluminescence [16], and photocatalytic and multiferroic materials [17]. MnWO4 material exhibits narrow band gap (~ 2.8 eV), strong redox capability, high photocatalytic efficiency,
EP
satisfactory bulk electrical conductivity, low melting point, and low cost [18]. These properties strongly depend on the shape, size, and structured surface of the products. In this regard,
AC C
different types of MnWO4 nanostructures have been successfully prepared through various methods; these structures include nanocapsules [19], nanococoons [20], nanoflowers [21], nanowires [22], and nanoparticles [23,24]. Despite advancements in fabrication of MnWO4 nanostructures [25], the synthesized product usually includes a mixture of various shapes. Thus, material researchers must develop a simple and scalable approach for controllable synthesis of MnWO4 nanomaterials. The sensing properties of MnWO4 nanomaterials have been rarely
3
ACCEPTED MANUSCRIPT 4
investigated, and related research is still in the early stages of development. In this work, we developed an effective method for controllably synthesizing MnWO4 nanorods for highly efficient gas sensors. Analysis of the gas-sensing properties of the as-fabricated MnWO4
RI PT
nanorods showed that these nanomaterials exhibit potential for gas sensors for NH3 detection. 2. Experimental 2.1. Materials
SC
All chemicals were used as received without further purification. (Mn(NO3)2.4H2O, Na2WO4.2H2O, 5-aminovaleric acid (AVA, 97%), 6-aminohexanoic acid (AHA, 70%), 2-
M AN U
aminononanoic acid (ANA, 90%), and hexamethylenediamine (98%) were purchased from Sigma–Aldrich. Analytical grade nitric acid (63%) and ethylene glycol (HOCH2CH2OH, 99.8%) were purchased from Reagent ACS. 2.2. Synthesis of MnWO4 nanorods
TE D
Here, the MnWO4 nanorods were synthesized based on the previous reported by Nguyen et al. [25]. Briefly, Mn(NO3)2·6H2O (0.60 mmol) and 6-aminohexanoic acid (24 mmol) were dissolved in 20 mL of distilled water to synthesize MnWO4 nanorods. The solution was added
EP
with 20 mL of an aqueous solution (0.60 mmol) of Na2WO4·2H2O under magnetic stirring at room temperature for 10 min. The solution immediately produced white amorphous MnWO4
AC C
precipitate because of the combination of Mn2+ cations and WO42- anions. The pH of the synthesis solution was adjusted to 9 by adding 1 mol·L-1 NaOH solution. The reaction mixture (40 mL) was transferred to 70 mL Teflon-lined stainless steel autoclave, treated at 180 °C for 20 h, and cooled naturally to room temperature. The product was filtered, washed several times with ethanol, and dried at 60 °C for 2 h to obtain MnWO4 nanorods.
4
ACCEPTED MANUSCRIPT 5
2.3. Material characterizations X-ray diffraction (XRD) data were recorded on a Bruker SMART APEXII X-ray diffractometer under Cu–Kα radiation. Scanning electron microscopy (SEM) analysis was
RI PT
conducted on Model JSM-5300LV. Transmission electron microscopic (TEM) images were obtained using JEOL JEM 1230 operated at 120 kV. High-resolution TEM images were acquired using JEOL field-emission transmission electron microscope (2100F) operated at 200 kV.
SC
Elemental dispersive spectrum (EDS) analysis was conducted on JEOL 6360 instrument working
2.4. Gas sensing properties
M AN U
at 3 kV.
Gas sensors were fabricated using thick film technique. The MnWO4 nanorod solution was drop casted onto an interdigitated electrode substrate. The sensors were treated at high temperatures to increase the adhesion between the sensing material and the substrate. The gas-
TE D
sensing properties of the sensors were investigated for NH3 detection at different concentrations (10 ppm to 1000 ppm) and temperatures (350 °C to 450 °C). The effects of MnWO4 on the sensing performance for detection of H2 and CO gases at 400 °C were also evaluated and
EP
compared. The system employed flow-through technique with a constant rate of 200 sccm [26]. The resistance of the sensors during the measurement was automatically recorded using Keithley
AC C
2602 controlled by a computer through a software program. Sensor response was defined as S = Rg/Ra, where Rg and Ra are the resistance of the sensor measured in the target gas and dry air, respectively. Response time (τresp.) is the time taken by the resistor to obtain Ra to Ra + 90%(Rg – Ra) when the sensor is exposed to the target gas. Recovery time (τrecov.) is the time taken by the resistor to change from Rg to Rg – 90%(Rg – Ra) when the sensor is retrieved from the target gas.
5
ACCEPTED MANUSCRIPT 6
3. Results and discussion The morphology and the crystal structure and phase of the as-synthesized MnWO4 nanostructures were determined by FESEM, TEM, HRTEM, and EDS analyses (Figure 1). The
RI PT
FESEM and TEM images of the MnWO4 samples are shown in Figures 1 (a) and (c), respectively. The particles exhibit a rod like structure with 20–30 nm diameter and 250–300 nm length. The HRTEM image [Figure 1 (d)] of a randomly chosen MnWO4 nanorod suggests that
SC
the nanoparticles comprise a single crystal with a uniform interplanar spacing of 0.3 nm [27]. The EDS spectrum indicates the presence of Mn, W, and O, with 1:1 molar ratio of Mn/W
M AN U
[Figure 1 (b)]. Hence, the as-prepared materials are composed of pure phase MnWO4. The purity and crystallinity of the as-prepared samples were characterized by power XRD patterns (Figure 2). All the diffraction peaks can be indexed as pure phase MnWO4 with a
TE D
monoclinic structure (space group P2/c), consistent with the literature data (JCPDS: 13-0434) [28]. All strong diffraction peaks and the lack of diffraction peaks corresponding to impurities were observed, indicating the high purity and crystallinity of the MnWO4 sample, respectively.
EP
The average crystalline size of the MnWO4 nanostructures estimated from the broadening (111) peak using the Debye-Scherrer equation is about 20 nm. This result is consistent with SEM and
AC C
TEM results indicating that the as-synthesized MnWO4 nanorods are a single-crystal structure. The mechanism formation of the MnWO4 nanorods may be explained by two steps: nucleation and growth [29]. In the first step, the combination of Mn2+ cations and WO anions forms MnWO4 nuclei. This stage is followed by the crystal growth process. In reaction solution, 6aminohaxanoic as a capping agent, plays an important role in controlling the lengths and aspect ratios (length/with) of MnWO4 nanoparticles. Nguyen et al. [25] demonstrated that the (021)
6
ACCEPTED MANUSCRIPT 7
faces of MnWO4 nanocrystals were selectively adsorbed and stabilized by 6-aminohaxanoic molecules, while the (100) faces were uncovered. The crystal grew anisotropically along the
RI PT
[100] direction because of its higher surface energy to obtain the MnWO4 nanorods.
The development of reliable and affordable gas sensors for ammonia detection has gained
SC
increasing attention because NH3 is a toxic gas with irritating smell [30]. These sensors also exhibit potential for various important applications, such as in automotive exhaust detection,
M AN U
environmental monitoring, and chemical and medical science industries [31]. Hence, the gassensing characteristics of sensors with the fabricated MnWO4 nanorods for NH3 detection were investigated at different concentrations (10–1000 ppm) and operating temperatures (350 °C to 450 °C). Figure 3(a) shows that the plots of transient resistance versus time are similar upon
TE D
exposure to NH3 gas at different working temperatures. The resistance of the sensor increased abruptly when exposed to NH3 gas (reducing gas) and recovered to the original values when the flow of analytic gas stopped at all working temperatures. This finding indicates the reversible
EP
adsorption between NH3 molecules and sensing elements, stable sensing characteristics, regardless of the working temperature, and the p-type semiconducting behavior of MnWO4 [32].
AC C
The base resistance of the sensor decreased when the operating temperature increases because of thermal activation, which excites electrons from the valence band to the conduction band, thereby enhancing conduction [33]. Figure 3(b) shows the plot of sensor response as a function of NH3 gas concentration at different temperatures. The response of the sensor increased with increasing working temperature. The sensor response to NH3 gas (10–1000 ppm) at 400 °C ranged from 1.3 to 2.87, which are higher than that at 350 °C and 450 °C. The sensing
7
ACCEPTED MANUSCRIPT 8
temperature of 400 °C can be considered the optimum operating temperature of the fabricated MnWO4 nanorod sensors. Figures 4 (a–c) present the response and recovery times of the MnWO4 nanorod sensors
RI PT
for detecting 50 ppm NH3 at different operating temperatures. Both response and recovery times rapidly decreased with increasing temperatures. The response time values ranged from 79 s at 350 °C to 65 s at 450 °C, and the recovery times are longer than the respective response times
SC
(from 120 s at 350 °C to 70 s at 450 °C). The effect of working temperature to response and recovery times exhibits a similar trend to those previously reported in the literature [34–36]. The
M AN U
dependence of sensor response and response and recovery times of the sensors on the working temperature can be explained by diffusion-reaction processes [37]. The reaction rate of analytic molecules and pre-adsorbed oxygen increased with increasing working temperature from 350 °C to 400 °C (optimal value), resulting in increased sensor responses. With further increase in the
TE D
working temperature above the optimal value, the penetration of analytic gas to the sensing surface was reduced, leading to decreased sensor responses [38]. The gas-sensing properties for NH3 have been extensively investigated on various materials, such as Co3O4 nanostructures
nanowires [46,47]; however, the properties of NH3 sensors based on MnWO4 material have rarely been reported. Comparison with the NH3 gas sensing properties of other nanosensors such as SnO2 nanoparticles, ZnO2 nanoparticles [48], Co3O4 nanowire-like network and Co3O4 nanowire-like network [49], the MnWO4 nanorods exhibits slight enhancement. Furthermore, the ammonia gas response time of the MnWO4 sensors also shows significant improvement in
8
ACCEPTED MANUSCRIPT 9
comparison with that of TiO2 nanoparticles, WO3 nanoparticles, TiO2/WO3 nanocomposite and TiO2@WO3 nanoparticles [41]. Selectivity is an important parameter of a gas sensor. In this regard, the fabricated
RI PT
MnWO4 nanorod sensors were tested for detecting various type of gases including CO (1–200 ppm) and H2 (25–1000 ppm) at the optimal working temperature. Figures 5 (a) and (c) show the transient resistance responses of the sensors versus time for detecting CO and H2 at 400 °C,
SC
respectively. The resistance of the sensor slightly increased upon exposure to CO or H2 gases; hence, the developed MnWO4 nanorod sensors can be used to detect CO and H2 gases. For CO
M AN U
sensing characteristics, the response of the MnWO4 sensor for 1–10 ppm CO slightly increased from 1.35 to 1.56 [Figure 5 (b)] and remained constant with further increase in CO concentration. Similarly, the response of the sensor slightly differed at various H2 concentrations [Figure 5 (d)]. The insert of Figure 5(b, d) displays the real-time transient responses of the sensor
TE D
for 50 ppm CO and H2 at 400 °C. The response and recovery times are 71 and 75 s for CO, respectively, and 66 and 62 s, respectively, for H2. The response times to CO or H2 are slightly shorter, and the recovery times are significantly lower than those to NH3. Scholars have
EP
investigated the use of gas sensors based on MnWO4 and other metal tungstate to detect H2 [50– 52]. However, the gas sensing characteristics of MnWO4 have been rarely investigated.
AC C
The gas-sensing mechanism of the as-fabricated MnWO4 nanorod sensors is based on the
reaction between the surface of the nanorods and the interaction of gas molecules, which cause a change in their conductance, as described by the Wolkenstein model [53]. MnWO4 material is a p-type semiconductor with holes being majority carriers. Thus, upon the exposure of the p-type MnWO4 nanorods to air, the oxygen molecules adsorb on the surface nanorods, capturing electrons in the valence band of the p-type MnWO4 nanorods, consequently generating
9
ACCEPTED MANUSCRIPT 10 additional holes and adsorbed oxygens become ionized into oxygen species (O , O , O ) [50].
When reducing gas molecules such as NH3, CO or H2 are exposed to the sensor, adsorbed oxygen species react with reducing gas based on the following chemical reactions (1-3) [39,54]: (1)
+ → +
(2)
+ → +
RI PT
4 + 6 → 2 + 6 + 6
(3)
SC
This process will release the previously trapped electrons, resulting in electron-hole compensation and consequently decreasing hole carriers, which leads to an increase in electrical
M AN U
resistance [39]. The selectivity of the sensors to NH3 may be related to factors, such as morphological and microstructural features [40], synergistic effect among the compositions [42,55], and interactions between NH3 molecule and the sensor surface. Ullah et al. [56] suggested that the polyaniline emeraldine salt (PANI ES) was very selective for sensing NH3
TE D
because of the large force of attraction established between the cationic form of nPANI and the electronegative part of the NH3 molecule; this result corroborates well with the experimental findings [57–59]. Hence, the good sensing properties of the MnWO4 nanorod sensors toward
EP
NH3 could be due to electrostatic interaction between the NH3 molecule containing a lone electron pair as proton acceptor and the hole accumulation layer (positive charge) over the
AC C
nanocrystals surface. This interaction may be related to the higher recovery time value to 50 ppm NH3 at 400 °C than that to CO or H2. Conclusions
Single-crystal MnWO4 nanorods were successfully synthesized through a simple hydrothermal method. The as-prepared nanostructures exhibit a uniform morphology and welldispersed particles. Sensors fabricated using the MnWO4 nanorods showed good selectivity to
10
ACCEPTED MANUSCRIPT 11
NH3 gas with short response and recovery times. This phenomenon may be related to the electrostatic interaction between NH3 molecules containing the hole accumulation layer (positive charge) over the MnWO4 nanocrystal surface. Our results demonstrated that manganese tungstate
RI PT
materials exhibit good sensing properties and thus can be used to fabricate sensors for detection of flammable and toxic gases. Acknowledgment
SC
This work was supported by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.02-2015.15.
[1]
M AN U
References
W. Hu, W. Tong, L. Li, J. Zheng, G. Li, Cation non-stoichiometry in multi-component oxide nanoparticles by solution chemistry: A case study on CaWO4 for tailored structural properties, Phys. Chem. Chem. Phys. 13 (2011) 11634. doi:10.1039/c0cp02153a. Y. Su, B. Zhu, K. Guan, S. Gao, L. Lv, C. Du, et al., Particle size and structural control of
TE D
[2]
ZnWO4 nanocrystals via Sn2+ doping for tunable optical and visible photocatalytic Properties, J. Phys. Chem. C 116 (2012) 18508–18517. doi:10.1021/jp3052505. M. Valian, F. Beshkar, M. Salavati-Niasari, Two facile methods to produce the cobalt
EP
[3]
manganite nanostructures and evaluation of their photocatalytic performance, J. Mater.
F. Namvar, F. Beshkar, M. Salavati, Novel microwave-assisted synthesis of leaf-like MnMo4 nanostructures and investigation of their photocatalytic performance, J. Mater. Sci. Mater. Electron. 28 (2017) 7962–7968. doi:10.1007/s10854-017-6499-0.
[5]
U. Nithiyanantham, S.R. Ede, T. Kesavan, P. Ragupathy, M.D. Mukadam, S.M. Yusuf, et al., Shape-selective formation of MnWO4 nanomaterials on a DNA scaffold: magnetic,
microcrystals: Solvothermal synthesis and their photocatalytic and magnetic properties,
P. Urbanowicz, E. Tomaszewicz, T. Groń, H. Duda, A.W. Pacyna, T. Mydlarz, Magnetic
SC
properties of R2WO6 (where R=Nd, Sm, Eu, Gd, Dy and Ho), Phys. B Condens. Matter. 404 (2009) 2213–2217. doi:10.1016/j.physb.2009.04.016.
W. Hu, Y. Zhao, Z. Liu, C.W. Dunnill, D.H. Gregory, Y. Zhu, Nanostructural evolution:
M AN U
[8]
from one-dimensional tungsten oxide nnowires to three-dimensional ferberite flowers, Chem. Mater. 20 (2008) 5657–5665. doi:10.1021/cm801369h. [9]
U. Nithiyanantham, S.R. Ede, S. Anantharaj, S. Kundu, Self-Assembled NiWO4
TE D
nanoparticles into chain-like aggregates on DNA scaffold with pronounced catalytic and supercapacitor activities, Cryst. Growth Des. 15 (2015) 673–686. doi:10.1021/cg501366d. [10]
M. Anicete-Santos, E. Orhan, M.A.M.A. de Maurera, L.G.P. Simões, A.G. Souza, P.S.
EP
Pizani, et al., Contribution of structural order-disorder to the green photoluminescence of PbWO4, Phys. Rev. B 75 (2007) 165105. doi:10.1103/PhysRevB.75.165105. K. Dong, Z. Liu, J. Liu, S. Huang, Z. Li, Q. Yuan, et al., Biocompatible and high-
AC C
[11]
performance amino acids-capped MnWO4 nanocasting as a novel non-lanthanide contrast agent for X-ray computed tomography and T1-weighted magnetic resonance imaging, Nanoscale 6 (2014) 2211. doi:10.1039/c3nr05455a.
[12]
H. Hossainian, M. Salavati-Niasari, M. Bazarganipour, Facile synthesis, structural characterization and degradation of organic contaminant over scheelite-type calcium
H. Hossainian, M. Salavati-Niasari, M. Bazarganipour, Photodegradation of organic dye
RI PT
using strontium tungstate spherical-like nanostructures; Synthesis and characterization, J. Mol. Liq. 220 (2016) 747–754. doi:10.1016/j.molliq.2016.04.129.
J. Tang, J. Shen, N. Li, M. Ye, Facile synthesis of layered MnWO4/reduced graphene oxide for
supercapacitor application,
J.
Alloys
doi:10.1016/j.jallcom.2015.12.219.
666
(2016) 15–22.
W. Qu, W. Wlodarski, J.-U. Meyer, Comparative study on micromorphology and
M AN U
[15]
Compd.
SC
[14]
humidity sensitive properties of thin-film and thick-film humidity sensors based on semiconducting MnWO4, Sens. Actuators B 64 (2000) 76–82. doi:10.1016/S09254005(99)00487-6.
Y. Xing, S. Song, J. Feng, Y. Lei, M. Li, H. Zhang, Microemulsion-mediated
TE D
[16]
solvothermal synthesis and photoluminescent property of 3D flowerlike MnWO4 micro/nanocomposite
structure,
Solid
State
Sci.
10
(2008)
1299–1304.
[17]
EP
doi:10.1016/j.solidstatesciences.2008.01.019. J. Ungelenk, S. Roming, P. Adler, W. Schnelle, J. Winterlik, C. Felser, et al., Ultrafine
AC C
MnWO4 nanoparticles and their magnetic properties, Solid State Sci. 46 (2015) 89–94. doi:10.1016/j.solidstatesciences.2015.06.004.
[18]
Y.N. Jiang, B.D. Liu, W.J. Yang, B. Yang, X.Y. Liu, X.L. Zhang, et al., New strategy for
the in situ synthesis of single-crystalline MnWO4/TiO2 photocatalysts for efficient and cyclic photodegradation of organic pollutants, CrystEngComm. 18 (2016) 1832–1841. doi:10.1039/C5CE02445E.
13
ACCEPTED MANUSCRIPT 14
[19]
S. Muthamizh, R. Suresh, K. Giribabu, R. Manigandan, S. Praveen Kumar, S. Munusamy, et al., MnWO4 nanocapsules: Synthesis, characterization and its sensing
property,
J.
Alloys
Compd.
doi:10.1016/j.jallcom.2014.09.049. [20]
(2015)
601–609.
W.B. Hu, X.L. Nie, Y.Z. Mi, Controlled synthesis and structure characterization of nanostructured
MnWO4,
Mater.
Charact.
61
(2010)
85–89.
SC
doi:10.1016/j.matchar.2009.10.009. [21]
619
RI PT
electrochemical
M.S. Hassan, T. Amna, S.S. Al-Deyab, H.-C. Kim, M.-S. Khil, Monodispersed 3D
H. Zhou, Y. Yiu, M.C. Aronson, S.S. Wong, Ambient template synthesis of multiferroic MnWO4 nanowires and nanowire arrays, J. Solid State Chem. 181 (2008) 1539–1545.
[23]
TE D
doi:10.1016/j.jssc.2008.03.009.
M. Mączka, M. Ptak, M. Kurnatowska, L. Kępiński, P. Tomaszewski, J. Hanuza, Phonon properties of nanosized MnWO4 with different size and morphology, J. Solid State Chem.
and optical property of MnWO4 nanoparticles synthesized by microwave-assisted method, J. Phys. Chem. Solids. 74 (2013) 426–430. doi:10.1016/j.jpcs.2012.11.004.
for shape-controlled synthesis of single-crystalline MnWO4 nanoparticles and spontaneous assembly of polypeptide-stabilized mesocrystal microspheres, CrystEngComm. 13 (2011) 1450–1460. doi:10.1039/C0CE00091D.
14
ACCEPTED MANUSCRIPT 15
[26]
L.V. Thong, L.T.N. Loan, N.V. Hieu, Comparative study of gas sensor performance of SnO2 nanowires and their hierarchical nanostructures, Sens. Actuators B 150 (2010) 112– 119. doi:10.1016/j.snb.2010.07.033. S. Lei, K. Tang, Z. Fang, Y. Huang, H. Zheng, Synthesis of MnWO4 nanofibres by a
RI PT
[27]
surfactant-assisted complexation–precipitation approach and control of morphology, Nanotechnology 16 (2005) 2407–2411. doi:10.1088/0957-4484/16/10/069.
L. Yang, Y. Wang, Y. Wang, X. Wang, L. Wang, G. Han, Shape-controlled synthesis of
SC
[28]
MnWO4 nanocrystals via a simple hydrothermal method, J. Alloys Compd. 578 (2013)
[29]
M AN U
215–219. doi:10.1016/j.jallcom.2013.05.133.
L. Thi, T. Tuyen, D.Q. Khieu, H.T. Long, D.T. Quang, C. The, L. Trang, T.T. Hoa, N.D. Cuong,
Monodisperse
uniform
CeO2
nanoparticles:
Controlled
synthesis
and
photocatalytic property, J. Nanomater. 2016 (2016) 7 pages.
S.-K. Lee, D. Chang, S.W. Kim, Gas sensors based on carbon nanoflake/tin oxide
TE D
[30]
composites for ammonia detection, J. Hazard. Mater. 268 (2014) 110–114. doi:10.1016/j.jhazmat.2013.12.049.
Y. Tang, Z. Li, X. Zu, J. Ma, L. Wang, J. Yang, et al., Room-temperature NH3 gas
EP
[31]
sensors based on Ag-doped γ-Fe2O3/SiO2 composite films with sub-ppm detection ability,
[32]
AC C
J. Hazard. Mater. 298 (2015) 154–161. doi:10.1016/j.jhazmat.2015.04.044. H. Farahani, R. Wagiran, M. Hamidon, Humidity Sensors Principle, Mechanism, and
Fabrication Technologies: A Comprehensive Review, Sensors 14 (2014) 7881–7939. doi:10.3390/s140507881.
[33]
P.V. Tong, N.D. Hoa, N.V. Duy, D.T.T. Le, N.V. Hieu, Enhancement of gas-sensing characteristics of hydrothermally synthesized WO3 nanorods by surface decoration with
15
ACCEPTED MANUSCRIPT 16
Pd nanoparticles, Sens. Actuators B 223 (2016) 453–460. doi:10.1016/j.snb.2015.09.108. [34]
M. Tonezzer, N.V. Hieu, Size-dependent response of single-nanowire gas sensors, Sens. Actuators B 163 (2012) 146–152. doi:10.1016/j.snb.2012.01.022. N.V. Hieu, P.T.H. Van, L.T. Nhan, N.V. Duy, N.D. Hoa, Giant enhancement of H2S gas
RI PT
[35]
response by decorating n-type SnO2 nanowires with p-type NiO nanoparticles, Appl. Phys. Lett. 101 (2012) 253106. doi:10.1063/1.4772488.
N.D. Cuong, D.Q. Khieu, T.T. Hoa, D.T. Quang, P.H. Viet, T.D. Lam, et al., Facile
SC
[36]
synthesis of α-Fe2O3 nanoparticles for high-performance CO gas sensor, Mater. Res. Bull.
G. Sakai, N. Matsunaga, K. Shimanoe, N. Yamazoe, Theory of gas-diffusion controlled sensitivity for thin film semiconductor gas sensor, Sens. Actuators B 80 (2001) 125–131. doi:10.1016/S0925-4005(01)00890-5.
X. Du, S.M. George, Thickness dependence of sensor response for CO gas sensing by tin
TE D
[38]
oxide films grown using atomic layer deposition, Sens. Actuators B 135 (2008) 152–160. doi:10.1016/j.snb.2008.08.015.
B. Wu, L. Wang, H. Wu, K. Kan, G. Zhang, Y. Xie, et al., Templated synthesis of 3D
EP
[39]
hierarchical porous Co3O4 materials and their NH3 sensor at room temperature, Mesoporous
AC C
Microporous
Mater.
225
(2016)
154–163.
doi:10.1016/j.micromeso.2015.12.019.
[40]
Z. Li, Z. Lin, N. Wang, J. Wang, W. Liu, K. Sun, et al., High precision NH3 sensing using
network nano-sheet Co3O4 arrays based sensor at room temperature, Sens. Actuators B
W. Meng, L. Dai, J. Zhu, Y. Li, W. Meng, H. Zhou, et al., A novel mixed potential NH3
16
ACCEPTED MANUSCRIPT 17
sensor based on TiO2@WO3 core–shell composite sensing electrode, Electrochim. Acta. 193 (2016) 302–310. doi:10.1016/j.electacta.2016.02.028. [42]
X. Liu, N. Chen, B. Han, X. Xiao, G. Chen, I. Djerdj, et al., Nanoparticle cluster gas
RI PT
sensor: Pt activated SnO2 nanoparticles for NH3 detection with ultrahigh sensitivity, Nanoscale 7 (2015) 14872–14880. doi:10.1039/C5NR03585F. [43]
Q. Xue, H. Chen, Q. Li, K. Yan, F. Besenbacher, M. Dong, Room-temperature high-
SC
sensitivity detection of ammonia gas using the capacitance of carbon/silicon heterojunctions, Energy Environ. Sci. 3 (2010) 288. doi:10.1039/b925172n. A.D. Ugale, R. V. Jagtap, D. Pawar, S. Datar, S.N. Kale, P.S. Alegaonkar, Nano-carbon:
M AN U
[44]
preparation, assessment, and applications for NH3 gas sensor and electromagnetic interference shielding, RSC Adv. 6 (2016) 97266–97275. doi:10.1039/C6RA17422A. [45]
M.-S. Park, K.H. Kim, M.-J. Kim, Y.-S. Lee, NH3 gas sensing properties of a gas sensor
TE D
based on fluorinated graphene oxide, Colloids Surfaces A Physicochem. Eng. Asp. 490 (2016) 104–109. doi:10.1016/j.colsurfa.2015.11.028. [46]
N. Kumar, A.K. Srivastava, R. Nath, B.K. Gupta, G.D. Varma, Probing the highly
EP
efficient room temperature ammonia gas sensing properties of a luminescent ZnO nanowire array prepared via an AAO-assisted template route, Dalt. Trans. 43 (2014) 5713.
[47]
AC C
doi:10.1039/c3dt53305k.
F. Shao, J.D. Fan, F. Hernández-Ramírez, C. Fàbrega, T. Andreu, A. Cabot, et al., NH3
sensing with self-assembled ZnO-nanowire µHP sensors in isothermal and temperaturepulsed mode, Sens. Actuators B 226 (2016) 110–117. doi:10.1016/j.snb.2015.11.109.
[48]
I. Rawal, Facial synthesis of hexagonal metal oxide nanoparticles for low temperature ammonia
gas
sensing
applications,
17
RSC
Adv.
5
(2015)
4135–4142.
ACCEPTED MANUSCRIPT 18
doi:10.1039/C4RA12747A. [49]
S. Yi, S. Tian, D. Zeng, K. Xu, X. Peng, H. Wang, S. Zhang, C. Xie, A novel approach to fabricate metal oxide nanowire-like networks based coplanar gas sensors array for selectivity,
Sens.
Actuators
B
204
doi:10.1016/j.snb.2014.07.076.
type
MnWO4/YSZ/Pt
sensor,
Sens.
Actuators
doi:10.1016/j.snb.2014.09.055.
206
(2015)
176–180.
Z. Tang, X. Li, J. Yang, J. Yu, J. Wang, Z. Tang, Mixed potential hydrogen sensor using ZnWO4
sensing
electrode,
doi:10.1016/j.snb.2014.01.086. [52]
B
M AN U
[51]
351–359.
Y. Li, X. Li, Z. Tang, Z. Tang, J. Yu, J. Wang, Hydrogen sensing of the mixed-potential-
SC
[50]
(2014)
RI PT
enhanced
Sens.
Actuators
B
195
(2014)
520–525.
C. Li, Y. Liang, J. Mao, L. Ling, Z. Cui, X. Yang, et al., Enhancement of gas-sensing
TE D
abilities in p-type ZnWO4 by local modification of Pt nanoparticles, Anal. Chim. Acta. 927 (2016) 107–116. doi:10.1016/j.aca.2016.04.050. [53]
T. Wolkenstein, Electronic processes on semiconductor surfaces during chemisorption,
[54]
EP
Springer US, Boston, MA, 1991. doi:10.1007/978-1-4615-3656-7. N.D. Cuong, T.T. Hoa, D.Q. Khieu, T.D. Lam, N.D. Hoa, N.V. Hieu, Synthesis,
AC C
characterization, and comparative gas-sensing properties of Fe2O3 prepared from Fe3O4
and
Fe3O4-chitosan,
J.
Alloys
Compd.
523
(2012)
120–126.
doi:10.1016/j.jallcom.2012.01.117.
[55]
L. Wang, Z. Lou, R. Zhang, T. Zhou, J. Deng, T. Zhang, Hybrid Co3O4/SnO2 core–shell
nanospheres as real-time rapid-response sensors for ammonia gas, ACS Appl. Mater. Interfaces 8 (2016) 6539–6545. doi:10.1021/acsami.6b00305.
18
ACCEPTED MANUSCRIPT 19
[56]
H. Ullah, A.-H.A. Shah, S. Bilal, K. Ayub, DFT study of polyaniline NH3, CO2, and CO gas sensors: Comparison with recent experimental data, J. Phys. Chem. C 117 (2013) 23701–23711. doi:10.1021/jp407132c. X. Huang, N. Hu, R. Gao, Y. Yu, Y. Wang, Z. Yang, et al., Reduced graphene oxide–
RI PT
[57]
polyaniline hybrid: Preparation, characterization and its applications for ammonia gas sensing, J. Mater. Chem. 22 (2012) 22488. doi:10.1039/c2jm34340a.
X. Huang, N. Hu, L. Zhang, L. Wei, H. Wei, Y. Zhang, The NH3 sensing properties of
SC
[58]
gas sensors based on aniline reduced graphene oxide, Synth. Met. 185–186 (2013) 25–30.
D.K. Bandgar, S.T. Navale, M. Naushad, R.S. Mane, F.J. Stadler, V.B. Patil, Ultrasensitive polyaniline–iron oxide nanocomposite room temperature flexible ammonia
Figure 1. FESEM image (a), EDS spectra (b), TEM image (c), and HRTEM image (d) of MnWO4 nanorods.
RI PT
Figure 2. Experimental and calculated XRD patterns of MnWO4 nanorods.
Figure 3. NH3 gas sensing characterizations: (a) transient response to NH3 gas at different temperatures (350-400 oC); the response plotted as a function gas concentration (b).
SC
Figure 4. The response and recovery times at 50 ppm NH3 and 350oC (a), 400oC (b), 450oC(c). Figure 5. Transient response to CO (a) and H2 (c) gases at 400oC; the response as a function of
AC C
EP
TE D
M AN U
CO (b) and H2 gas concentration. The inserts are response and recovery times for CO and H2 gas.
20
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
Figure 1
AC C EP
10
20
2θ (degree) 30
40
50 013
-131
002
M AN U SC
-111 111
RI PT
Figure 2
220 -202 202
112
-102 121 -112
020
011 110
TE D
010 100
Intensity (a.u.)
ACCEPTED MANUSCRIPT
60
ACCEPTED MANUSCRIPT
RI PT
Figure 3
o
2.5M
@350 C
(a)
2.0M
750k
1000 ppm
o
@400 C NH3
600k
500 ppm
250 ppm
M AN U
Resistance (Ω)
1.0M
SC
1.5M
100 ppm
450k
25 ppm 10 ppm
300k
50 ppm
o
@450 C
200k
TE D
150k 100k
500
EP
0
AC C
Response (Rgas/Rair)
2.8
1000
1500
2000
2500
Time (s)
o
@350 C o @400 C o @450 C
(b)
2.4 2.0 1.6 1.2 10
3000
100
NH3 conc. (ppm)
1000
ACCEPTED MANUSCRIPT
(a)
1.4M
1.2M o
@ 350 C & 50 ppm NH3
NH3
(b)
105 s
72 s
400k
320k
Air
TE D
360k
SC
Air
1.0M
Resistance (Ω)
120 s
79 s
M AN U
Resistance (Ω)
1.6M
RI PT
Figure 4
o
@400 C & 50 ppm NH3
AC C
EP
280k
(c)
Resistance (Ω)
130k
NH3
70 s 65 s Air
120k
o
@450 C & 50 ppm NH3
110k 100k 90k
NH3
0
100
200
300
Time (s)
400
RI PT
ACCEPTED MANUSCRIPT
1.5
280k
AC C
240k 0
500 1000 1500 2000 2500
Time (s)
Gas out
360k 50 ppm CO o 400 C
320k
0.5
280k Gas in
0
1
100
200 300 Time (s)
10
400
500
100
CO conc. (ppm)
Response (Rgas/Rair)
500 ppm
250 ppm
TE D
EP
320k
100 ppm
360k
50 ppm
(c)
1000 ppm
o
@ 400 C &H2 gas
25 ppm
Resistance (Ω)
400k
R (Ω )
1.0
75 s
71 s
400k
500 1000 1500 2000 2500
Time (s)
SC
Response (Rgas/Rair)
(b)
2.0 1.5
o
(d)
@ 400 C & H2 gas
360k
1.0
R (Ω )
250k
200 ppm
10 ppm
300k
2.0
M AN U
350k
5 ppm
2.5 ppm
400k 1 ppm
Resistance (Ω )
(a)
450k
50 ppm
o
@400 C & CO gas
100 ppm
Figure 5.
320k
Gas out
50 ppm H2
280k
0.5
o
400 C
240k
Gas in
0
10
62 s
66 s
100
100
200 300 Time (s)
400
1000
H2 conc. (ppm)
ACCEPTED MANUSCRIPT Highlights
AC C
EP
TE D
M AN U
SC
RI PT
MnWO4 nanorods were controllably synthesized by an effective method. MnWO4 nanorods exhibited single-crystallite after heated treatment. Gas sensor based on MnWO4 showed higher performance to NH3 gas.
