f-SWCNT polymer nanocomposite thin films prepared by electrochemical polymerization

Accepted Manuscript Hydrogen sulfide sensors based on PANI/f-SWCNT polymer nanocomposite thin films prepared by electrochemical polymerization Mahdi Hasan Suhail, Omed Gh. Abdullah, Ghada Ayad Kadhim PII:

S2468-2179(18)30202-8

DOI:

https://doi.org/10.1016/j.jsamd.2018.11.006

Reference:

JSAMD 191

To appear in:

Journal of Science: Advanced Materials and Devices

Received Date: 30 September 2018 Revised Date:

23 November 2018

Accepted Date: 25 November 2018

Please cite this article as: M.H. Suhail, O.G. Abdullah, G.A. Kadhim, Hydrogen sulfide sensors based on PANI/f-SWCNT polymer nanocomposite thin films prepared by electrochemical polymerization, Journal of Science: Advanced Materials and Devices, https://doi.org/10.1016/j.jsamd.2018.11.006. 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 Hydrogen sulfide sensors based on PANI/f-SWCNT polymer nanocomposite thin films prepared by electrochemical polymerization

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Mahdi Hasan Suhail1, Omed Gh. Abdullah2,3,*, Ghada Ayad Kadhim4

Department of Physics, College of Science, University of Baghdad, Baghdad, Iraq.

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Department of Physics, College of Science, University of Sulaimani, Sulaymaniyah, Iraq.

3

Komar Research Center, Komar University of Science and Technology, Sulaymaniyah, Iraq.

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Department of Physics, College of Science, University of Wassit, Wassit, Iraq.

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E-mail: [email protected]

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ACCEPTED MANUSCRIPT Hydrogen sulfide sensors based on PANI/f-SWCNT polymer nanocomposite thin films

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prepared by electrochemical polymerization

Abstract

Hydrogen sulfide (H2S) gas sensor in the form of thin films based on polyaniline (PAN)

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incorporated with various concentration of functionalized single wall carbon nanotube (fSWCNT) were prepared by electrochemical polymerization of Aniline monomer with sulfuric

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acid in aqueous solution. Surface morphology of thin film nanocomposites was investigated by Field Emission Scanning Electron microscopy (FE-SEM) and revealed that the f-SWCNTs were almost uniformly distributed on the surface of host PANI matrix. The X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Hall effect measurements were

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used to characterize the synthesized PANI/f-SWCNT nanocomposites. The Hall measurements reveal the p-type conductivity. The grown FTIR band at 1145 cm-1 with the increase of the f-SWCNT content evidence a formation of charge transfers due to a

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remarkable interaction between PANI and f-SWCNTs. The response of this nanocomposite film towards H2S gas was investigated by monitoring the change in electrical resistance with

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time in the presence of 30% H2S at different operating temperatures. The sensing analysis showed that the sensitivity increased with f-SWCNT content in the PANI matrix. The rapid response/recovery times toward H2S gas, at 50 oC, was achieved for PANI/0.01% f-SWCNT nanocomposite sample.

Keywords: conductive polymer; PANI; nanocomposites; f-SWCNT; H2S gas sensor.

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1. Introduction Hydrogen sulfide (H2S) is widely used in various chemical industries and research laboratories, and it is a very poisonous, flammable, and explosive gas. Exposure to low

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concentrations of H2S can cause various respiratory symptoms [1]. However, high exposure level can cause very serious health effects and even death. Accordingly, the fast and accurate detection of this harmful gas at low concentrations is very important to protect human health.

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Conventional chemical gas sensors often rely on thin/thick films of various sensing materials [2]. In terms of their application as H2S gas sensors, thin film semiconducting metal oxides,

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such as SnO2, WO3, BaTiO3, and Fe2O3, have been extensively studied [3-5]. The metal oxides based sensors inherently suffer from some problems, such as low selectivity, short lifetime and relatively high operating temperature leading to high power consumption which limit their versatility [6,7]. Thus the conducting polymers, such as

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polyaniline (PANI), polypyrrole (PPy), and polythiophene (PTh), have been used as sensing active layers in chemical sensors due to their high sensitivity, and reversible changes in their optical and electrical properties when exposed to certain liquids or gases [8,9]. The greatest

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advantage of conductive polymers is their flexibility and low-cost processability, which allows a facile-fabrication of the active layer of gas sensors. As a result, more and more

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attention has been paid to the gas sensors based on conducting polymers [10,11]. However, these sensors often have a low sensitivity, and relatively high operating temperature range. To improve sensing performance, conducting polymer hybrid nanostructured materials have been employed to overcome the fundamental limitations of film-based sensors. Hybrid polymernanocomposite materials represent interesting strategies developed to circumvent limitations of the individual components and to improve the response of mechanical actuators [8]. The high surface-to-volume ratio and unique size-dependent properties of nanomaterials have

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ACCEPTED MANUSCRIPT resulted in very promising further improvements in sensing performance [2]. The gas-sensing mechanism of thin-film gas sensors is essentially based on the change in the electrical resistance of the sensing element, when specific gases interact with its surface [12-14]. In recent years, a great deal of research effort has been directed to develop a sensor based on

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conducting polymers incorporated with carbon nanotubes (CNTs), due to their high stiffness, and good electrical conductivity at relatively low concentrations of CNTs [15]. CNTs have shown as a new class of one-dimensional crystal structure having extraordinary mechanical,

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thermal and electrical properties [16,17].

Among the conducting polymers, PANI is considered to be one of the most technologically

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promising because of its easy preparation, low cost, environmental stability, and controllable electrical conductivity [18]. Moreover, PANI has also been used in various applications such as electrodes for batteries, sensors, photovoltaic cells and electrochemical displays [19]. It has previously been established that incorporating nanoparticles in polar-polymers often

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modifies the electron structures of the compound which resulted in changes to both the bulk and surface properties [12]. Consequently, the resulting polymer nanocomposite can achieve sensitivity and selectivity for gas detection far exceeds those achievable performance with the

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individual constituent of the composite. Until recently, many researchers have demonstrated that the PANI based nanocomposites can be widely used as sensors to detect various gases

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[20]. Srivastava et al. [21] reported multiwall carbon nanotube (MWCNT) doped polyaniline (PANI) composite thin films for hydrogen gas sensing applications. Their results reveal that the MWCNT/PANI composite film shows a higher sensitivity in comparison to pure PANI and it decreases with increasing hydrogen gas pressure. Zhang et al. [22] developed PANISWCNT thin film nanocomposite based sensor for ammonia (NH3) gas sensing, and they conclude that the electrochemical functionalization of SWCNTs provides a promising new method with improved sensitivity, response time, and reproducibility.

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ACCEPTED MANUSCRIPT The influence of the morphology on the gas sensing performance is another important factor, should be considered. The literature survey of polymer nanocomposites reveals that the sensors composition is a key factor that affected the surface morphology of sensing materials which depend primarily on the nature of the components and the processing conditions [23].

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In the present work, structural, morphology, and H2S sensing properties of polyaniline functionalized single-wall carbon nanotubes (PANI/SWCNTs) thin films prepared by electrochemical polymerization were systematically investigated. The effect of f-SWCNT

2. Experimental 2.1. Preparation of thin film sensors

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concentration as well as operating temperature on sensing parameters was also studied.

The electrochemical method was used to polymerize PANI/f-SWCNTs thin film nanocomposites using aniline monomer in the aqueous acid medium at room temperature. A

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titanium plate was used as the working electrode and indium tin oxide (ITO) as a reference electrode. ITO substrates were ultrasonically cleaned by typical methods. Nanocomposite solution is prepared by dissolving 0.3 M aniline monomer in 0.1 M sulfuric acid (H2SO4) and

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mixed with the different ratio of f-SWCNTs (0.005 and 0.01 %) in the 150 ml of distilled water. The synthesized electrodes were carefully washed with distilled water thoroughly to

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avoid the possible presence of electrolyte species on the surface of the polymer film. PANI/CNT films were deposited at voltage 2.4 and 2.2 V with two different ratios of fSWCNT in 3 minutes. The prepared nanocomposite thin films were green, uniform, and strongly adherent to the ITO substrate. The thickness of the samples was ~100 nm measured by optical interferometer technique using He-Ne laser (632 nm). A mask used to deposit 100 nm thin aluminum layer on the films surface by thermal evaporation.

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o

to 80 o, and Cu Kα

radiation (λ=1.5414 Å) was used for X-ray source. The surface microstructures were analyzed

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by using field emission scanning electron microscopy (FE-SEM) Hitachi model S-4160 operating at 30 kV. The Fourier transform infrared (FTIR) spectrum of perpetrated samples was recorded using Shimadzu IR Affinity-1, in the range of 400-4000 cm-1. Room

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temperature Hall effect was carried out using the Van der Pauw method. Hall measurements were used to quantify important electrical parameters such as Hall coefficient, Hall carrier

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concentration, and Hall mobility. The gas sensing properties such as sensitivity, response and recovery time were subsequently measured and evaluated, at exposure nanocomposite thin films to 30% H2S at different operating temperature 20, 50, 100, 150, 200 oC for different f-

3. Results and discussion 3.1. XRD Analysis

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SWCNT concentration.

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The XRD patterns of pure and f-SWCNT doped PANI nanocomposite films are shown in Figure 1. The diffraction patterns of samples exhibit two crystalline peaks at around 2θ=25o

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and 50o which referred, respectively, to (200) and (210) plane directions, which represent the characteristic peaks of PANI [24]. It can be clearly seen that the intensity of crystalline peaks for nanocomposite films become higher and sharper in comparison to pure PANI film. The average grain size of the films were estimated by using the Debye-Scherrer formula [25]. The results obtained are shown in Table 1. As seen from Table 1, the average grain size increases with increasing f-SWCNT concentration.

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3.2. FTIR analysis FTIR spectroscopy was conducted on the pure and f-SWCNT doped PANI nanocomposite thin film samples, and the results are shown in Figure 2. The main characteristic band of

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PANI observed at 3466 cm-1 assigned to the asymmetric N-H2 stretching vibration [26]. The two bonds situated at 1461 cm-1 and 1554 cm-1 corresponding to the C=C stretching modes for the benzenoid and quinoid rings, respectively [27,28]. The prominent band at 775 cm-1 may

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be attributed to C-H out of plane deformation.

It is observed that all the characteristic bands appeared in the fingerprint region of PANI are

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appeared in the FTIR spectra of PANI/f-SWCNT nanocomposite samples, indicating that main constituents of PANI and its nanocomposite with f-SWCNTs have the same chemical structure. However, the incorporation of f-SWCNT results into the slight shift in peaks position to lower or higher wavenumbers from its original position. A noticeable shift in the

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characteristic peaks position depicted in Table 2 reveals the presence of interaction between PANI and f-SWCNT during electrochemical polymerization. Such an interaction was also reported by Patil et al. [29] between PANI and ZnO nanoparticle thin films.

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The polymer shows an interaction promote and stabilize the quinoid ring structure in the polymer nanocomposite. This interaction between PANI and f-SWCNTs may result in a

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charge transfer between them [30-32]. The π- bonded surface of f-SWCNT might interact strongly with conjugated structure of PANI, especially through the quinoid ring. The strong band at 1145 cm-1 is considered to be a measure of the degree of delocalization of electrons, and thus it is characteristics peak of PANI conductivity [33]. It appears that the interaction between PANI and f-SWCNTs increase the effective degree of electron delocalization, and thus enhances the conductivity of polymer composite films [34].

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3.3. FE-SEM analysis The microstructure and surface morphology of pure and f-SWCNT doped PANI nanocomposite films were studied by FE-SEM analysis. The images were taken at 60,000

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times magnification. Figure 3 shows the FE-SEM images and interactive 3D surface plot (the inset figure) of pure and f-SWCNT doped PANI thin films. The image of pure PANI sample shows the formation of nanostructured conducting PANI which distributed almost uniformly

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and the average grain size of spherical PANI nanoparticles was estimated to be 36.62 nm, and increased to 49.84 and 84.86 nm upon incorporating 0.005% and 0.010% of f-SWCNT,

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respectively. The micrograph also reveals some clusters made up from aggregates of many PANI nanoparticles.

The micrographs of prepared nanocomposite thin films show the effect of f-SWCNT on the morphology of these films. The increase in f-SWCNT concentration caused an increase in the

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average surface grain size and surface roughness of the nanocomposite films, which corresponds well with the obtained result from XRD. As a result of strong interaction between f-SWCNT and polar groups of PANI (which was previously confirmed by FTIR analysis),

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f-SWCNT.

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homogeneous interaction is typically obtained on polymerization of aniline in the presence of

A higher degree of roughness is observed for f-SWCNT doped PANI based nanocomposite surface when compared with pure PANI. These features are shown in the inset of Figure 2. The high degree of roughness, as identified in the 3D surface images, is associated with an increase in the exposed surface area. It is well reported in the literature that, the high exposed surface area of sensing element usually has positive effects on the gas-sensing performance by provides more active sites for adsorption of gas molecules [35,36].

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3.4. Hall measurements The Hall-effect measurements are a useful diagnostic for the characterization of materials,

particular applications [37]. The values of Hall coefficient ( Hall mobility (

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which provide the basic electrical parameters to find the suitability of the material for ), carriers concentration (

),

), and the type of charge carriers conductivity have been estimated from

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Hall measurements for pure and f-SWCNT doped PANI nanocomposite thin films at room temperature, using the following equations:

| 2

=

3

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and

is Hall voltage,

1

= | where;

Here,

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=

is constant current,

is conductivity,

is a charge of an electron,

is an applied magnetic field in Gauss.

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The positive sign of Hall coefficients (

) for all compositions of PANI/f-SWCNT confirmed

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the p-type nature conductivity of this system. It can also be noted that the magnitude of decreases with increasing f-SWCNT concentration. During the electropolymerization, emeraldine salt is formed onto the surface of carbon nanotubes, making the polyaniline a ptype semiconductor. Table 3 illustrates electrical parameters for PANI/f-SWCNT nanocomposite thin films. It is seen that the carrier’s concentration ( (

) and Hall mobility

) increases with increasing f-SWCNT concentration, which indicated the reduction of

resistivity.

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PANI/f-SWCNT nanocomposite thin films with respect to H2S gas were measured by collecting change in electrical resistance with time over two sensing electrodes under H2S gas. Figure 4 shows the variation of normalized resistance (∆ /

) as a function of time with

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on/off gas valve of pure PANI and PANI/f-SWCNT films at different operating temperature. From Hall measurement the present polymer nanocomposite thin films are p-type

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semiconductors with holes as major charge carriers. The H2S gas is believed to partly dissociate into H+ and HS− as it is a weak acid, resulting in the partial protonation of PANI. This causes a band bending and space-charge layer near the surface of each grain boundary [39]. By introducing H2S gas, the electrical conductivity of the film change due to the

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interactions process between surface grains and the gas molecules, which caused remove of electrons from the aromatic rings of PANI. The electron transferring can cause the changes in work function and hence the resistance of the sensing element. When this occurs for the p-

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[10].

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type conductive polymer, the electrical conductance of the conductive polymer is enhanced

The variation of H2S gas sensitivity versus operating temperature for PANI/f-SWCNT polymer nanocomposite thin films are shown in Figures 5. The doped films exhibited an improvement in the sensitivity in comparison with pure PANI film. This is attributed to an increase in the rate of surface reaction of the target gas, which confirmed by SEM analysis. The highest sensitivity is found at 50 °C, and the value decreases with a further increase in the

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The response time of the sensor is dependent on how rapidly gas molecules can diffuse and

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reacts with the sensitive active layer. Figures 6 and 7 respectively exhibit the variation of response time and recovery time versus operating temperature for pure and f-SWCNT doped PANI films. The results reveal that f-SWCNT doped PANI film has faster response/recovery

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times in comparison to pure PANI film. This may be attributed to the formation of conducting paths and electron hopping through conducting channels of carbon nanotubes. The presence

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of f-SWCNT in PANI may promote the possibility of more H2S absorption due to their centrally hollow core structure, and their large surface area provides more interaction sites within PANI film. On the other hand, both the response and recovery times of sensor was found to decrease with increasing operating temperature. This can be explained as follow: The

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gas sensing process involves adsorption and diffusion of the gas molecules on the sensor active layer and their reaction with the sensing film. Since the adsorption takes place at low temperature and decreases with increasing temperature [41], consequently, the gas sensing

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response will decrease with increase in temperature.

4. Conclusions

The electrochemical polymerization technique was used to prepare pure and f-SWCNT doped PANI nanocomposite thin films. XRD and FTIR spectrum revealed the incorporation of fSWCNT into the conducting PANI matrix. FE-SEM images confirmed that the f-SWCNTs were uniformly dispersed on the surface of nanocomposite film. The Hall effect measurements confirm that the PANI/f-SWCNT nanocomposite films behave as p-type

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temperature equal to 50 oC.

References

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[1] K.S. Yoo, S.D. Han, H.G, Moon, S.J. Yoon, C.Y. Kang, Highly sensitive H2S sensor

Sensors 15 (2015) 15468-15477.

M AN U

based on the metal-catalyzed SnO2 nanocolumns fabricated by glancing angle deposition,

[2] J.H. Lim, N. Phiboolsirichit, S. Mubeen, M.A. Deshusses, A. Mulchandani, N.V. Myung, Electrical and gas sensing properties of polyaniline functionalized single-walled carbon nanotubes, Nanotechnology 21 (2010) 075502.

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[3] G.H. Jain, L.A. Patil, M.S. Wagh, D.R. Patil, S.A. Patil, D.P. Amalnerkar, Surface modified BaTiO3 thick film resistors as H2S gas sensors, Sensor. Actuat. B-Chem. 117 (2006) 159-165.

EP

[4] Y. Wang, Y. Wang, J. Cao, F. Kong, H. Xia, J. Zhang, B. Zhu, S. Wang, S. Wu, Lowtemperature H2S sensors based on Ag-doped α-Fe2O3 nanoparticles, Sensor. Actuat. B-

AC C

Chem. 131 (2008) 183-189. [5] V. Manikandan, M. Singh, B.C. Yadav, J.C. Denardin, Fabrication of lithium substituted copper ferrite (Li-CuFe2O4) thin film as an efficient gas sensor at room temperature, J. Sci. Adv. Mater. Devices 3 (2018) 145-150. [6] S.G. Bachhav, D.R. Patil, Study of polypyrrole-coated MWCNT nanocomposites for ammonia sensing at room temperature, J. Mater. Sci. Chem. Eng. 3 (2015) 30-44.

11

ACCEPTED MANUSCRIPT [7] V. Talwar, O. Singh, R.C. Singh, ZnO assisted polyaniline nanofibers and its application as ammonia gas sensor, Sensor. Actuat. B-Chem.191 (2014) 276-282. [8] M.R. Santos, H.P. Oliveira, Simple method for mass production of polypyrrole/carbon nanotubes hybrid, Quim. Nova 37 (2014) 1000-1003.

RI PT

[9] R.L.D. Whitby, A. Korobeinyk, S.V. Mikhalovsky, T. Fukuda, T. Maekawa, Morphological effects of single-layer graphene oxide in the formation of covalently bonded polypyrrole composites using intermediate diisocyanate chemistry, J. Nanopart.

SC

Res. 13 (2011) 4829-4837.

[10] H. Bai, G. Shi, Gas sensors based on conducting polymers, Sensors 7 (2007) 267-307.

M AN U

[11] S.J. Park, C.S. Park, H. Yoon, Chemo-electrical gas sensors based on conducting polymer hybrids, Polymers 9 (2017) 155.

[12] A.F. Abdulameer, M.H. Suhail, O.G. Abdullah, I.M. Al-Essa, Fabrication and characterization of NiPcTs organic semiconductors based surface type capacitive-

TE D

resistive humidity sensors, J. Mater. Sci. Mater. Electron. 28 (2017) 13472-13477. [13] N.R. Stradiotto, H. Yamanaka, M.V.B. Zanoni, Electrochemical sensors: a powerful tool in analytical chemistry, J. Braz. Chem. Soc. 14 (2003) 159-173.

EP

[14] M.H. Suhail, A.A. Ramadan, S.B. Aziz, O.G. Abdullah, Chemical surface treatment with toluene to enhances sensitivity of NO2 gas sensor based on CuPcTs/Alq3 thin films, J.

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Sci. Adv. Mater. Devices 2 (2017) 301-308. [15] B. Philip, J.K. Abraham, A. Chandrasekhar, V.K. Varadan, Carbon nanotube/PMMA composite thin films for gas-sensing applications, Smart Mater. Struct. 12 (2003) 935939. [16] S.M. Lee, K.H. An, Y.H. Lee, G. Seifert, T. Frauenheim, A hydrogen storage mechanism in single-walled carbon nanotubes, J. Am. Chem. Soc. 123 (2001) 5059-5063.

12

ACCEPTED MANUSCRIPT [17] S. Srivastava, S.S. Sharma, S. Agrawal, S. Kumar, M. Singh, Y.K. Vijay, Study of chemiresistor type CNT doped polyaniline gas sensor, Synthetic Met. 160 (2010) 529534. [18] H.K. Hassan, N.F. Atta, A. Galal, Electropolymerization of aniline over chemically

RI PT

converted graphene-systematic study and effect of dopant, Int. J. Electrochem. Sci. 7 (2012) 11161-11181.

[19] S.B. Kondawar, P.T. Patil, S.P. Agrawal, Chemical vapour sensing properties of

SC

electrospun nanofibers of polyaniline/ ZnO nanocomposites, Adv. Mater. Lett. 5 (2014) 389-395.

M AN U

[20] S. Pandey, Highly sensitive and selective chemiresistor gas/vapor sensors based on polyaniline nanocomposite: A comprehensive review, J. Sci. Adv. Mater. Devices 1 (2016) 431-453.

[21] S. Srivastava, S.S. Sharma, S. Kumar, S. Agrawal, M. Singh, Y.K. Vijay,

TE D

Characterization of gas sensing behavior of multi walled carbon nanotube polyaniline composite films, Int. J. Hydrogen Energ. 34 (2009) 8444-8450. [22] T. Zhang, M.B. Nix, B.Y. Yoo, M.A. Deshusses, N.V. Myung, Electrochemically

1153-1158.

EP

functionalized singleÅwalled carbon nanotube gas sensor, Electroanalysis 18 (2006)

AC C

[23] C. Liu, H. Tai, P. Zhang, Z. Yuan, X. Du, G. Xie, Y. Jiang, A high-performance flexible gas sensor based on self-assembled PANI-CeO2 nanocomposite thin film for trace-level NH3 detection at room temperature, Sensor. Actuat. B-Chem. 261 (2018) 587-597. [24] R.K. Agrawalla, V. Meriga, R. Paul, A.K. Chakraborty, A.K. Mitra, Solvothermal synthesis of a polyaniline nanocomposite-a prospective biosensor electrode material, Express Polym. Lett. 10 (2016) 780-787.

13

ACCEPTED MANUSCRIPT [25] S.F. Bdewi, O.G. Abdullah, B.K. Aziz, A.A.R. Mutar, Synthesis, structural and optical characterization of MgO nanocrystalline embedded in PVA matrix, J. Inorg. Organomet. Polym. Mater. 26 (2016) 326-334. [26] S. Mousavi, K. Kang, J. Park, I. Park, A room temperature hydrogen sulfide gas sensor

flexible substrates, RSC Adv. 6 (2016) 104131-104138.

RI PT

based on electrospun polyaniline–polyethylene oxide nanofibers directly written on

[27] S.H. Kazemi, B. Karimi, S.A. Aghdam, H. Behzadnia, M.A. Kiani, Polyaniline–ionic

behavior, RSC Adv. 5 (2015) 69032-69041.

SC

liquid derived ordered mesoporous carbon nanocomposite: synthesis and supercapacitive

M AN U

[28] O.G. Abdullah, S.A. Saleem, Effect of copper sulfide nanoparticles on the optical and electrical behavior of poly (vinyl alcohol) films, J. Electron. Mater. 45 (2016) 5910-5920. [29] S.L. Patil, S.G. Pawar, M.A. Chougule, B.T. Raut, P.R. Godse, S. Sen, V.B. Patil, Structural,

morphological,

optical,

and

electrical

properties

of

PANi-ZnO

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nanocomposites, Int. J. Polym. Mater. Polym. Bioma. 61 (2012) 809-820. [30] M. Baibarac, I. Baltog, S. Lefrant, J.Y. Mevellec, O. Chauvet, Polyaniline and carbon nanotubes based composites containing whole units and fragments of nanotubes, Chem.

EP

Mater. 15 (2003) 4149-4156.

[31] O.G. Abdullah, Y.A.K. Salman, S.A. Saleem, Electrical conductivity and dielectric

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characteristics of in-situ prepared PVA/HgS nanocomposite films, J. Materi. Sci. Mater. Electron. 27 (2016) 3591-3598. [32] S.B. Aziz, O.G. Abdullah, M.A. Rasheed, A novel polymer composite with a small optical band gap: New approaches for photonics and optoelectronics, J. Appl. Polym. Sci. 134 (2017) 44847 (1-8).

14

ACCEPTED MANUSCRIPT [33] S. Quillard, G. Louarn, S. Lefrant, A.G. Macdiarmid, Vibrational analysis of polyaniline: a comparative study of leucoemeraldine, emeraldine, and pernigraniline bases, Phys. Rev. B 50 (1994) 12496-12508. [34] I.D. Sharma, P.K. Saini, V.K. Sharma, Structural, optical, morphological and electrical

RI PT

characteristics of polyaniline for device applications, Indian J. Eng. Mater. Sci. 20 (2013) 145-149.

[35] C.M. Hung, D.T.T. Le, N.V. Hieu, On-chip growth of semiconductor metal oxide

SC

nanowires for gas sensors: A review, J. Sci. Adv. Mater. Devices 2 (2017) 263-285.

[36] R. Ferro, J.A. Rodriguez, P. Bertrand, Development and characterization of a sprayed

M AN U

ZnO thin film-based NO2 sensor, Phys. Stat. Sol. C 2 (2005) 3754-3757. [37] S.A.O. Russell, L. Cao, D. Qi, A. Tallaire, K.G. Crawford, A.T.S. Wee, D.A.J. Moran, Surface transfer doping of diamond by MoO3: A combined spectroscopic and Hall measurement study, Appl. Phys. Lett. 103 (2013) 202112.

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[38] H. Yoon, Current trends in sensors based on conducting polymer nanomaterials, Nanomaterials 3 (2013) 524-549.

[39] C. Wang, L. Yin, L. Zhang, D. Xiang, R. Gao, Metal oxide gas sensors: sensitivity and

EP

influencing factors, Sensors 10 (2010) 2088-2106. [40] S.A. Garde, LPG and NH3 sensing properties of SnO2 thick film resistors prepared by

[41]

AC C

screen printing technique, Sensors Transducers J. 122 (2010) 128-142. N.V.

Hieu,

N.Q.

Dung,

P.D.

Tam,

T.

Trung,

N.D.

Chien,

Thin

film

polypyrrole/SWCNTs nanocomposites-based NH3 sensor operated at room temperature, Sensor. Actuat. B-Chem. 140 (2009) 500-507.

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Figure 1. The XRD pattern of pure and f-SWCNT doped PANI nanocomposite thin films.

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Figure 2. FTIR spectra of the pure and f-SWCNT doped PANI nanocomposite films.

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Figure 3. FE-SEM images of (a) pure PANI, (b) PANI/0.005% f-SWNT, and (c) PANI/0.01% f-SWNT thin films (scale bar 500 nm).

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Figure 4. The variation of normalized resistance with time for: (a) pure PANI, (b)

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EP

TE D

PANI/0.005% f-SWNT, and (c) PANI/0.01% f-SWNT.

Figure 5. Sensitivity versus operating temperature for PANI/f-SWNT thin films nanocomposite based sensor.

20

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

nanocomposite based sensor.

M AN U

Figure 6. Response time versus operating temperature for PANI/f-SWNT thin films

Figure 7. Recovery time versus operating temperature for PANI/f-SWNT thin films nanocomposite based sensor.

21

ACCEPTED MANUSCRIPT Table 1. Structural parameters of XRD pattern for pure and f-SWCNT doped PANI nanocomposite thin films. Samples

2θ (Deg.)

FWHM

dhkl (Å)

G.S. (nm)

(hkl)

25.630

0.172

3.4729

49.7

(200)

50.080

0.116

1.8200

86.9

(210)

f- 25.600

0.156

3.4769

57.4

(200)

50.090

0.104

1.8196

94.3

(210)

25.599

0.141

3.4770

60.4

(200)

50.100

0.087

1.8193

112.5

(210)

0.005%

SWCNT

SC

PANI/

RI PT

Pure PANI

M AN U

PANI/ 0.01% f-SWCNT

Table 2. The value of FTIR bonds for PANI/f-SWCNT thin films N-H

Pure PANI

3466

PANI/0.005 f-SWCNT

3469

PANI/0.01 f-SWCNT

C=C

S=O

C-H

1554, 1461

1145

775

1557, 1463

1137

775

1560, 1464

1141

780

TE D

Samples

3470

EP

Table 3. Effect of f-SWCNT concentration on the Hall measurements results of PANI/f-

Content %

(Ω-1.cm-1)

(cm3/C)

(cm-3)

(cm2/V.sec)

0.000

AC C

SWCNT nanocomposite thin films

2.21

0.08987

69.5

19.89

0.005

4.51

0.06657

93.8

30.04

0.010

6.22

0.05567

112.2

34.62

f-SWCNT

x102

x1019

22