Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3. The gas sensing study revealed that the response value increases with increasing concentration of NH3. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2791

Bandgar, D.K.

Chougule, M.A.

Godse, P.R.

Patil, S.L.

Patil, V.B.

Pawar, S.G.

Electronic Sumy State University Institutional Repository

   J. Nano- Electron. Phys. 3 (2011) No1, P. 1056-1063  2011 SumDU (Sumy State University)   1056 PACS number: 81.07. Pr  FABRICATION OF POLYANILINE/TIO2 NANOCOMPOSITE AMMONIA VAPOR SENSOR   S.G. Pawar, S.L. Patil, M.A. Chougule, P.R. Godse,  D.K. Bandgar, V.B. Patil   Materials Research Laboratory, School of Physical Sciences,  Solapur University, Solapur-413255, M.S., India  E-mail: drvbpatil@gmail.com Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3. The gas sensing study revealed that the response value increases with increasing concentration of NH3. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration.  Keywords: PANi/TiO2 NANOCOMPOSITE, RESPONSE, SELECTIVITY, RESPONSE TIME, RECOVERY TIME.  (Received 04 February 2011)  1.  INTRODUCTION  In recent years, the demand for gas sensors for safety control requirements and environmental monitoring has expanded enormously. Choice of suitable sensing material along with efficient microelectronics for the detection system is the key step in such efforts [1]. The use of conducting polymers as sensing elements in chemical sensors is attracting attention due to their high sensitivity in change of the electrical and optical properties when exposed to different types of gases or liquids. The ease in synthesis of these polymers and sensitivity at room temperature add to the sensor’s advantages. This can be of importance particularly as ammonia sensors that are used in different applications such as industrial process, fertilizers, food technology, clinical diagnosis, farms and environmental pollution monitoring [2]. Polyaniline is one of the most attractive materials among the variety of conducting polymers due to its unique electrical properties, environmental stability, easy fabrication process and intrinsic redox reaction [3-5]. Polyaniline has also been used in different applications such as light emitting diodes [6], rechargeable batteries [7] and photovoltaic cells [8]. However, the problems with these conducting polymers are their low processing ability, poor chemical stability and mechanical strength [9]. There is a tremendous approach for the enhancement of the mechanical strength and characteristics of sensors by combining the organic materials with inorganic counterparts to form composites [10, 11]. Accordingly, organic inorganic nanocomposite sensors have been developed by several research groups. Dhawale et al. [12] fabricated polyaniline titanium dioxide heterostructure gas sensor for LPG     FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1057 sensing, Tai et al. [13] fabricated a polyaniline titanium dioxide nanocomposite for NH3 and CO sensors and reported that the resistance of the composite increased with increasing concentration of the gases. The PANi / SnO2 hybrid material was prepared by a hydrothermal method and studied for gas sensing of ethanol and acetone by L. Geng et al. [14]. Parvatikar et al. [15] fabricated polyaniline / WO3 composite based sensor and reported that the film conductivity increased with increasing humidity. Among the inorganic materials, nanocrystalline TiO2 is one of the most attractive and extensively used materials for detection of H2, LPG, NO2 and NH3 gases [12].  In the present paper, we report fabrication of polyaniline / TiO2 nanocomposite thin film gas sensors working at room temperature. The cross sensitivity of the sensor to various gases indicate the selectivity of the sensor to ammonia. The nanocomposites were characterized by X-ray diffraction (XRD) in 2  range of 10-70  using X-ray Diffractometer (Model: Philips PW3710). Morphological study of PANi / TiO2 (0-50 weight ) composite films was carried out using scanning electron microscopy (SEM Model: JEOL JSM 6360) operating at 20 kV. The gas sensing measurements were made using gas sensor set up at room temperature.  2.  EXPERIMENTAL  2.1 Fabrication of PANi/TiO2 nanocomposite sensor films  The TiO2 nanocomposites with PANi were prepared by adding TiO2 in different weight percentage (0  50 weight ) in smooth agate mortar and pestle. The nanocomposite powder was put in m-cresol and stirred for 11 hrs to get casting solution. Thin films were prepared on glass substrates by spin coating method at 3000 rpm for 40 s and dried on hot plate at 1000 C for 10 min [16]. The silver paste strips of 1 mm wide and 1 cm apart from each other were made on films for contacts.   3. RESULTS AND DISCUSSION  3.1 X-ray diffraction studies  Fig. 1 denotes X-ray diffraction patterns of the PANi, TiO2 and PANi/TiO2 nanocomposites (20-50 wt ) materials. The XRD pattern of PANi (Fig. 1 a) shows a broad peak at 2   25.30  which corresponds to (110) plane of PANi [17]. The diffraction pattern of TiO2 (Fig. 1 b) show sharp and well defined peaks, indicate the crystallinity of synthesized material. The intensities of diffraction peaks for PANi/TiO2 nanocomposites (Fig. 1 c) are lower than that for TiO2. The presence of amorphous PANi reduces the mass volume percentage of TiO2 and sequentially weakens diffraction peaks of TiO2. It has also been observed that the crystallinity of PANi is improved by the addition of TiO2 nanoparticles. XRD diffractograms of PANi/TiO2 nanocomposites have shown that all major diffraction peaks of nanocrystalline TiO2 and are in the same peak angle positions. The observed 2  values are consistent with the standard JCPDS values (JCPDS No. 78-1285 & 86) which enumerate the mixed anatase and rutile tetragonal structure of TiO2.    1058 S.G. PAWAR, S.L. PATIL, M.A. CHOUGULE, ET AL.  10 20 30 40 50 60 70(a) Pure PANi110   Intensity (a.u)2  (degree)       20 30 40 50 60 70 80(b)215A220 A116 A204 A211 A105 A200 A101 R111 R004 A101 A  Intensity (a.u)2  (degree)TiO2  10 20 30 40 50 60 70(c)116 A204 A211 A105 A112 A004 A101 A110 PANiPANi:TiO240 %50 %30 %20 %Intensity (a.u.)  2 q (degree)  Fig. 1  X-ray diffraction patterns of Pure PANi (a), TiO2 (b) and PANi/TiO2  (0-50 wt ) (с).  3.2 Scanning electron microscopy  Fig. 2 a, b and c shows the scanning electron micrographs of PANi, TiO2 and PANi/TiO2 (50 wt ) films at  20,000 magnification, respectively. The SEM image of the polyaniline film (Fig. 2 a) exhibits a fibrous structure with many pores and gaps among the fibers. Fig. 2 b shows the surface morphology of the TiO2 nanoparticles film, annealed at 700  C for 1 h. The image shows that the nanoparticles are fine with an average grain size of about 60 nm. The image of the nanocomposite (Fig. 2 c) shows that there is no agglomeration and uniform distribution of the TiO2 particles in the PANi matrix. It was considered that the nanostructured TiO2 particles embedded within the netlike structure built by PANi chains.  The morphology plays an important role in sensitivity of the gas sensing films. The grain sizes, structural formation, surface to volume ratio and film thickness are important parameters for gas sensing films. It can be seen that the PANi and PANi / TiO2 films have a very porous structure, interconnected network of fibers and high surface area. It has also been pointed out that such structure contributes to a rapid diffusion of dopants into the film.      FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1059                Fig. 2  Scanning electron micrographs of a) PANi, b) TiO2 and c) PANi/TiO2 ( 50 wt ) films  3.3 Gas sensing measurements  In order to record response to different gases, contacts were made on the silver paste strips, 1 mm wide and 1 cm apart from each other. The films deposited on the glass substrates were mounted in an airtight SS housing of 250 cc and measured quantity of desired gas (from a standard canister of 1000 ppm concentration) was injected through syringe so as to yield desired gas concentration in the housing. The room temperature gas response to various concentrations of different oxidizing and reducing (ammonia, ethanol, methanol, nitrogen dioxide and hydrogen sulfide) gases were measured by recording the resistance of the film in air and in presence of any particular ambient. A Rigol 3062 (6 ½ digit) DMM was used to measure the resistance variation of the sensor films. The sensor response (S) was defined as S  (Rg – Ra)/Ra, where Rg and Ra are the resistance of sensor film in a measuring gas and in clean air respectively [13]. The gas sensing measurement set up used is as shown in Fig. 3.  An attempt was made to study selectivity of PANi/TiO2 films for lower concentration of NH3 (20 ppm) as compared to the sensitivities for higher concentration of CH3-OH, C2H5-OH, NO2 and H2S (100 ppm). The bar chart for selectivity is as shown in Fig. 4. It is observed that PANi/TiO2 thin films can sense lower concentration of NH3 with higher sensitivity value as compared to large concentration of other gases. The plausible mechanism of selectivity for NH3 may be traced to the characteristics of vapor adsorbed over the surface of PANi/TiO2 nanocomposite.  c b a    1060 S.G. PAWAR, S.L. PATIL, M.A. CHOUGULE, ET AL.    Fig. 3  Gas sensing measurement set up  NH3 CH3-OH C2H5-OH NO2 H2S0246810100 ppm100 ppm100 ppm100 ppm20 ppm PANi/TiO2  Response %Gas  Fig. 4  Gas responses of PANi/TiO2 sensor film to 20 ppm of NH3 and 100 ppm of CH3-OH,C2H5-OH, NO2  and H2S   Therefore the sensing capability of PANi / TiO2 (50 wt ) nanocomposite sensor towards different concentrations (20-100 ppm) of ammonia vapour has been explored and compared with the results obtained for PANi sensor film. Fig. 5 (a) shows electrical response of PANi to 100 ppm of NH3 and Fig. 5 (b) of PANi / TiO2 to 20, 40, 60, 80 and 100 ppm of NH3. As seen for both the sensor films, the resistance increases dramatically upon exposure to ammonia vapor, attains stable value and decreases gradually after being transferred to clean air.  Moreover, the nanocomposite sensor exhibit high response to ammonia than pure PANi sensor. The increase in resistance after exposure to NH3 may be because of porous structure of PANi/TiO2 films leads to the predominance     FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1061 of surface phenomena over bulk material phenomena, which may again be due to surface adsorption effect, and chemisorptions leads to the formation of ammonium. The resistance attains stable value when dynamic equilibrium is attained [19]. In order to explain the higher response and gas sensing mechanism of PANi/TiO2 nanocomposite H. Tai et al. [13] postulated that PANi and TiO2 may form a p-n junction and the observed increased response of the nanocomposite material may be due to the creation of positively charged depletion layer on the surface of TiO2 which could be formed owing to inter  particle electron migration from TiO2 to PANi at the heterojunction. This would cause the reduction of the activation energy and enthalpy of physisorption for NH3 gas.  0 100 200 300 400 500 6001.81.92.02.12.22.3(a)Gas outGas in100ppm NH3PANiResistance (x106)/ Time/ s   100 200 300 400 500 600 7001.61.82.02.22.42.6(b) PANi:TiO2  Resistance (x105 )/ Time/ s 100ppm 80ppm 60ppm 40ppm 20ppm  Fig. 5  Gas responses of PANi/TiO2 sensor film to 20 ppm of NH3 and 100 ppm of CH3-OH, C2H5-OH, NO2, and H2S   The response values of PANi/TiO2 sensor film is plotted as a function of NH3 concentration in Fig. 6. It is observed that the response slows down at higher concentration; this may be due to less availability of surface area with possible reaction sites on surface of the film.    1062 S.G. PAWAR, S.L. PATIL, M.A. CHOUGULE, ET AL.  20 40 60 80 100101520253035404550 PANi: TiO2  Response%NH3 ppm  Fig. 6  Response of PANi/TiO2 thin film sensor to NH3 (20-100 ppm)   The response/recovery time is an important parameter use for characterizing a sensor. The response time and recovery time are defined as the times of 90  total resistance change [12]. Fig. 7 shows the response and recovery times of PANi / TiO2 for different concentrations of NH3. It is revealed that the response time decreases from 72 s to 41 s, when NH3 concentration increased from 20 ppm to 100 ppm, this may be because of high surface area due to porous structure of exposed film which facilitates rapid diffusion of gas molecules into the film. From the same graph, it is found that for higher concentration of NH3, the recovery time was long. This may probably due to lower desorption rate and reaction products are not leaving from the interface immediately after the reaction.  20 40 60 80 10038404244464850525456586062646668707274 Response RecoveryNH3 Conc./ ppmResponse time /s340360380400420440460480500520540Recovery time /s  Fig. 7  Variation of response and recovery time of the PANi / TiO2 thin film sensor with NH3 concentration      FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1063 4. CONCLUSIONS  The PANi/TiO2 thin film sensor was fabricated by spin coating technique. The composites have poorer crystallinity than TiO2, because of amorphous structure of PANi. But crystallinity of nanocomposites has been improved with increasing percentage of TiO2 nanoparticles. It can be seen that PANi/TiO2 film has a very porous structure, interconnected network of fibers and high surface area which contributes to a rapid diffusion of dopants into the film. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3 at room temperature. It is observed that the response slows down at higher concentration; this may be due less availability of surface area with possible reaction sites on surface of the film. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration.   Authors (VBP) are grateful to the Department of Science and Technology, New Delhi for financial support through the scheme no. SR/FTP/PS-09/2007. Thanks are also extended to Dr. Rashinkar, Department of Chemistry, SUK for FTIR facility, Prof. Lonikar, School of chemical Sciences, SUS for UV facility and Dr. P.S. Patil, Department of Physics, Shivaji University, Kolhapur for providing SEM facility.  REFERENCES 1. G.K. Prasad, T.P. Radhakrishnan, D.S. Kumar, M.G. Krishna, Sens. Actuat. B-Chem. 106, 626 (2005). 2. C. Wrenn, Occu. Health Saf. 69b, 64 (2000). 3. R.L.N. Chandrakanthi, M.A. Careem, Thin Solid Films 417, 51 (2002). 4. P.R. Somani, R. Marimuthu, U.P. Mulik, S.R. Mulik, S.R. Sanikar, D.P. Amalnerkar, Synth. Met. 106, 45 (1999). 5. Y. He, Mater. Chem. Phys. 92, 134 (2005). 6. S.A. Chen, K.R. Chuang, C.I. Chao, H.T. Lee, Synth. Met. 82, 207 (1996). 7. A.G. MacDiarmid, L.S. Yang, W.S. Huang, B.D. Humphrey, Synth Met. 18, 393 (1987). 8. D. Verma, V. Dutta, Sens. Actuat. B-Chem. 134, 373 (2008). 9. M. Mastuguchi, A. Okamoto, Y. Sakai, Sens. Actuat. B-Chem. 94, 46 (2003). 10. F.Y. Chaung, S.M Yang, Synth. Met. 152, 361 (2005). 11. A.Z. Sadek, W. Wlodarski, K. Shin, R. Bkaner, K. Kalantarzadeh, Nanotechnology 17, 4488 (2006). 12. D.S. Dhawale, R.R. Salunkhe, U.M. Patil, K.V. Gurav, A.M. More, C.D. Lokhande, Sens. Actuat. B-Chem. 134, 988 (2008). 13. R. Zeggari, B. Wacogne, C. Pieralli, C. Roux, T. Gharbi, Sens. Actuat. B-Chem. 125, 664 (2007). 14. L. Geng, Y. Zhao, X. Huang, S. Wang, S. Zhang, S. Wu, Sens. Actuat. B-Chem. 120, 568 (2007). 15. J. Wang, I. Matsubara, N. Murayama, S. Woosuck, N. Izu, Thin Solid Films 514, 329 (2006). 16. S.G. Pawar, S.L. Patil, M.A. Chougule, A.T. Mane, D.M. Jundale, V.B. Patil, Int. J. Polym. Mater. 59, 777 (2010). 17. S.G. Pawar, S.L. Patil, A.T. Mane, B.T. Raut, V.B. Patil, Archives of Applied Science Research 1(2), 109 (2009). 18. S.G. Pawar, S.L. Patil, M.A. Chougule, D.M. Jundale, V.B. Patil, J. Mater. Sci: Mater. Electron. 22, 260 (2011). 19. H. Tai, Y. Juang, G. Xie, J. Yu, X. Chen, Z. Ying, Sens. Actuat. B-Chem 129, 319 (2008). 

Fabrication of polyaniline/TiO2 nanocomposite ammonia vapor sensor

Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The gas sensing measurements were carried out for different concentrations of NH3. The gas sensing study revealed that the response value increases with increasing concentration of NH3. Moreover, as concentration of NH3 increases, the response time decreases while recovery time increases, which can be attributed to the varying adsorption and desorption rates of an ambient gas with increasing concentration

S. G. Pawar

S. L. Patil

M. A. Chougule

B. T. Raut

S. A. Pawar

V. B. Patil

Directory of Open Access Journals

Fabrication of Polyaniline/ TiO2 Nanocomposite Ammonia Vapor Sensor

SocioEconomic Challenges Journal (Sumy State University)

 
 
 
J. Nano- Electron. Phys. 
3 (2011) No1, P. 1056-1063 
 2011 SumDU 
(Sumy State University) 
 
 
1056 
PACS number: 81.07. Pr 
 
FABRICATION OF POLYANILINE/TIO2 NANOCOMPOSITE AMMONIA 
VAPOR SENSOR  
 
S.G. Pawar, S.L. Patil, M.A. Chougule, P.R. Godse,  
D.K. Bandgar, V.B. Patil 
 
 Materials Research Laboratory, School of Physical Sciences, 
 Solapur University, Solapur-413255, M.S., India 
 E-mail: drvbpatil@gmail.com 
Polyaniline/Titanium dioxide (PANi/TiO2) nanocomposite was fabricated from 
PANi, prepared by oxidative chemical polymerization and TiO2, synthesized by sol gel 
method. The PANi/TiO2 thin film sensors were prepared by spin coating technique. 
PANi/TiO2 nanocomposites were characterized by XRD and SEM. The cross sensitivity 
of thin film sensor indicate that the sensor exhibit selectivity to ammonia (NH3). The 
gas sensing measurements were carried out for different concentrations of NH3. The 
gas sensing study revealed that the response value increases with increasing 
concentration of NH3. Moreover, as concentration of NH3 increases, the response time 
decreases while recovery time increases, which can be attributed to the varying 
adsorption and desorption rates of an ambient gas with increasing concentration. 
 
Keywords: PANi/TiO2 NANOCOMPOSITE, RESPONSE, SELECTIVITY, RESPONSE 
TIME, RECOVERY TIME. 
 
(Received 04 February 2011) 
 
1.  INTRODUCTION 
 
In recent years, the demand for gas sensors for safety control requirements 
and environmental monitoring has expanded enormously. Choice of suitable 
sensing material along with efficient microelectronics for the detection 
system is the key step in such efforts [1]. The use of conducting polymers as 
sensing elements in chemical sensors is attracting attention due to their 
high sensitivity in change of the electrical and optical properties when 
exposed to different types of gases or liquids. The ease in synthesis of these 
polymers and sensitivity at room temperature add to the sensor’s advantages. 
This can be of importance particularly as ammonia sensors that are used in 
different applications such as industrial process, fertilizers, food technology, 
clinical diagnosis, farms and environmental pollution monitoring [2]. 
Polyaniline is one of the most attractive materials among the variety of 
conducting polymers due to its unique electrical properties, environmental 
stability, easy fabrication process and intrinsic redox reaction [3-5]. 
Polyaniline has also been used in different applications such as light emitting 
diodes [6], rechargeable batteries [7] and photovoltaic cells [8]. However, the 
problems with these conducting polymers are their low processing ability, 
poor chemical stability and mechanical strength [9]. There is a tremendous 
approach for the enhancement of the mechanical strength and characteristics 
of sensors by combining the organic materials with inorganic counterparts 
to form composites [10, 11]. Accordingly, organic inorganic nanocomposite 
sensors have been developed by several research groups. Dhawale et al. [12] 
fabricated polyaniline titanium dioxide heterostructure gas sensor for LPG 
 
 
 
 FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1057 
sensing, Tai et al. [13] fabricated a polyaniline titanium dioxide nanocomposite 
for NH3 and CO sensors and reported that the resistance of the composite 
increased with increasing concentration of the gases. The PANi / SnO2 hybrid 
material was prepared by a hydrothermal method and studied for gas sensing of 
ethanol and acetone by L. Geng et al. [14]. Parvatikar et al. [15] fabricated 
polyaniline / WO3 composite based sensor and reported that the film 
conductivity increased with increasing humidity. Among the inorganic 
materials, nanocrystalline TiO2 is one of the most attractive and extensively 
used materials for detection of H2, LPG, NO2 and NH3 gases [12]. 
 In the present paper, we report fabrication of polyaniline / TiO2 
nanocomposite thin film gas sensors working at room temperature. The cross 
sensitivity of the sensor to various gases indicate the selectivity of the 
sensor to ammonia. The nanocomposites were characterized by X-ray 
diffraction (XRD) in 2  range of 10-70  using X-ray Diffractometer (Model: 
Philips PW3710). Morphological study of PANi / TiO2 (0-50 weight ) 
composite films was carried out using scanning electron microscopy (SEM 
Model: JEOL JSM 6360) operating at 20 kV. The gas sensing measurements 
were made using gas sensor set up at room temperature. 
 
2.  EXPERIMENTAL 
 
2.1 Fabrication of PANi/TiO2 nanocomposite sensor films 
 
The TiO2 nanocomposites with PANi were prepared by adding TiO2 in 
different weight percentage (0  50 weight ) in smooth agate mortar and 
pestle. The nanocomposite powder was put in m-cresol and stirred for 11 hrs 
to get casting solution. Thin films were prepared on glass substrates by spin 
coating method at 3000 rpm for 40 s and dried on hot plate at 1000 C for 
10 min [16]. The silver paste strips of 1 mm wide and 1 cm apart from each 
other were made on films for contacts.  
 
3. RESULTS AND DISCUSSION 
 
3.1 X-ray diffraction studies 
 
Fig. 1 denotes X-ray diffraction patterns of the PANi, TiO2 and PANi/TiO2 
nanocomposites (20-50 wt ) materials. The XRD pattern of PANi (Fig. 1 a) 
shows a broad peak at 2   25.30  which corresponds to (110) plane of 
PANi [17]. The diffraction pattern of TiO2 (Fig. 1 b) show sharp and well 
defined peaks, indicate the crystallinity of synthesized material. The 
intensities of diffraction peaks for PANi/TiO2 nanocomposites (Fig. 1 c) are 
lower than that for TiO2. The presence of amorphous PANi reduces the mass 
volume percentage of TiO2 and sequentially weakens diffraction peaks of 
TiO2. It has also been observed that the crystallinity of PANi is improved by 
the addition of TiO2 nanoparticles. XRD diffractograms of PANi/TiO2 
nanocomposites have shown that all major diffraction peaks of 
nanocrystalline TiO2 and are in the same peak angle positions. The observed 
2  values are consistent with the standard JCPDS values (JCPDS No. 78-
1285 & 86) which enumerate the mixed anatase and rutile tetragonal 
structure of TiO2. 
 
 
 
1058 S.G. PAWAR, S.L. PATIL, M.A. CHOUGULE, ET AL.  
10 20 30 40 50 60 70
(a) Pure PANi
1
1
0
 
 
 
In
te
n
s
it
y
 (
a
.u
)
2  (degree)       
20 30 40 50 60 70 80
(b)
2
1
5
A
2
2
0
 A
1
1
6
 A2
0
4
 A2
1
1
 A
1
0
5
 A
2
0
0
 A
1
0
1
 R
1
1
1
 R
0
0
4
 A
1
0
1
 A
 
 
In
te
n
s
it
y
 (
a
.u
)
2  (degree)
TiO2
 
 
10 20 30 40 50 60 70
(c)
11
6 
A
20
4 
A
21
1 
A
10
5 
A
11
2 
A0
04
 A
10
1 
A
11
0 
P
A
N
i
PANi:TiO
2
40 %
50 %
30 %
20 %
In
te
n
si
ty
 (
a.
u
.)
 
 
2 q (degree)
 
 
Fig. 1  X-ray diffraction patterns of Pure PANi (a), TiO2 (b) and PANi/TiO2  
(0-50 wt ) (с). 
 
3.2 Scanning electron microscopy 
 
Fig. 2 a, b and c shows the scanning electron micrographs of PANi, TiO2 
and PANi/TiO2 (50 wt ) films at  20,000 magnification, respectively. The 
SEM image of the polyaniline film (Fig. 2 a) exhibits a fibrous structure 
with many pores and gaps among the fibers. Fig. 2 b shows the surface 
morphology of the TiO2 nanoparticles film, annealed at 700  C for 1 h. The 
image shows that the nanoparticles are fine with an average grain size of 
about 60 nm. The image of the nanocomposite (Fig. 2 c) shows that there is 
no agglomeration and uniform distribution of the TiO2 particles in the PANi 
matrix. It was considered that the nanostructured TiO2 particles embedded 
within the netlike structure built by PANi chains. 
 The morphology plays an important role in sensitivity of the gas sensing 
films. The grain sizes, structural formation, surface to volume ratio and film 
thickness are important parameters for gas sensing films. It can be seen that 
the PANi and PANi / TiO2 films have a very porous structure, interconnected 
network of fibers and high surface area. It has also been pointed out that such 
structure contributes to a rapid diffusion of dopants into the film. 
 
 
 
 
 FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1059 
      
  
      
 
Fig. 2  Scanning electron micrographs of a) PANi, b) TiO2 and c) PANi/TiO2 
( 50 wt ) films 
 
3.3 Gas sensing measurements 
 
In order to record response to different gases, contacts were made on the 
silver paste strips, 1 mm wide and 1 cm apart from each other. The films 
deposited on the glass substrates were mounted in an airtight SS housing of 
250 cc and measured quantity of desired gas (from a standard canister of 
1000 ppm concentration) was injected through syringe so as to yield desired 
gas concentration in the housing. The room temperature gas response to 
various concentrations of different oxidizing and reducing (ammonia, 
ethanol, methanol, nitrogen dioxide and hydrogen sulfide) gases were 
measured by recording the resistance of the film in air and in presence of 
any particular ambient. A Rigol 3062 (6 ½ digit) DMM was used to measure 
the resistance variation of the sensor films. The sensor response (S) was 
defined as S  (Rg – Ra)/Ra, where Rg and Ra are the resistance of sensor 
film in a measuring gas and in clean air respectively [13]. The gas sensing 
measurement set up used is as shown in Fig. 3. 
 An attempt was made to study selectivity of PANi/TiO2 films for lower 
concentration of NH3 (20 ppm) as compared to the sensitivities for higher 
concentration of CH3-OH, C2H5-OH, NO2 and H2S (100 ppm). The bar chart 
for selectivity is as shown in Fig. 4. It is observed that PANi/TiO2 thin films 
can sense lower concentration of NH3 with higher sensitivity value as 
compared to large concentration of other gases. The plausible mechanism of 
selectivity for NH3 may be traced to the characteristics of vapor adsorbed over 
the surface of PANi/TiO2 nanocomposite. 
 
c 
b a 
 
 
 
1060 S.G. PAWAR, S.L. PATIL, M.A. CHOUGULE, ET AL.  
 
 
Fig. 3  Gas sensing measurement set up 
 
NH3 CH3-OH C2H5-OH NO2 H2S
0
2
4
6
8
10
100 ppm100 ppm100 ppm
100 ppm
20 ppm PANi/TiO2
 
 
R
es
p
o
n
se
 %
Gas
 
 
Fig. 4  Gas responses of PANi/TiO2 sensor film to 20 ppm of NH3 and 100 ppm of 
CH3-OH,C2H5-OH, NO2  and H2S 
 
 Therefore the sensing capability of PANi / TiO2 (50 wt ) nanocomposite 
sensor towards different concentrations (20-100 ppm) of ammonia vapour 
has been explored and compared with the results obtained for PANi sensor 
film. Fig. 5 (a) shows electrical response of PANi to 100 ppm of NH3 and 
Fig. 5 (b) of PANi / TiO2 to 20, 40, 60, 80 and 100 ppm of NH3. As seen for 
both the sensor films, the resistance increases dramatically upon exposure to 
ammonia vapor, attains stable value and decreases gradually after being 
transferred to clean air. 
 Moreover, the nanocomposite sensor exhibit high response to ammonia 
than pure PANi sensor. The increase in resistance after exposure to NH3 may 
be because of porous structure of PANi/TiO2 films leads to the predominance 
 
 
 
 FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1061 
of surface phenomena over bulk material phenomena, which may again be 
due to surface adsorption effect, and chemisorptions leads to the formation 
of ammonium. The resistance attains stable value when dynamic equilibrium 
is attained [19]. In order to explain the higher response and gas sensing 
mechanism of PANi/TiO2 nanocomposite H. Tai et al. [13] postulated that 
PANi and TiO2 may form a p-n junction and the observed increased response 
of the nanocomposite material may be due to the creation of positively 
charged depletion layer on the surface of TiO2 which could be formed owing 
to inter  particle electron migration from TiO2 to PANi at the 
heterojunction. This would cause the reduction of the activation energy and 
enthalpy of physisorption for NH3 gas. 
 
0 100 200 300 400 500 600
1.8
1.9
2.0
2.1
2.2
2.3
(a)
Gas out
Gas in
100ppm NH3
PANi
R
e
s
is
ta
n
c
e
 (
x
1
0
6
)/
 
Time/ s  
 
100 200 300 400 500 600 700
1.6
1.8
2.0
2.2
2.4
2.6
(b) PANi:TiO
2
 
 
R
e
si
st
a
n
ce
 (
x1
0
5 )
/ 
Time/ s
 100ppm
 80ppm
 60ppm
 40ppm
 20ppm
 
 
Fig. 5  Gas responses of PANi/TiO2 sensor film to 20 ppm of NH3 and 100 ppm of 
CH3-OH, C2H5-OH, NO2, and H2S 
 
 The response values of PANi/TiO2 sensor film is plotted as a function of 
NH3 concentration in Fig. 6. It is observed that the response slows down at 
higher concentration; this may be due to less availability of surface area 
with possible reaction sites on surface of the film. 
 
 
 
1062 S.G. PAWAR, S.L. PATIL, M.A. CHOUGULE, ET AL.  
20 40 60 80 100
10
15
20
25
30
35
40
45
50 PANi: TiO2
 
 
R
e
s
p
o
n
s
e
%
NH
3
 ppm
 
 
Fig. 6  Response of PANi/TiO2 thin film sensor to NH3 (20-100 ppm) 
 
 The response/recovery time is an important parameter use for 
characterizing a sensor. The response time and recovery time are defined as 
the times of 90  total resistance change [12]. Fig. 7 shows the response 
and recovery times of PANi / TiO2 for different concentrations of NH3. It is 
revealed that the response time decreases from 72 s to 41 s, when NH3 
concentration increased from 20 ppm to 100 ppm, this may be because of 
high surface area due to porous structure of exposed film which facilitates 
rapid diffusion of gas molecules into the film. From the same graph, it is 
found that for higher concentration of NH3, the recovery time was long. 
This may probably due to lower desorption rate and reaction products are 
not leaving from the interface immediately after the reaction. 
 
20 40 60 80 100
38
40
42
44
46
48
50
52
54
56
58
60
62
64
66
68
70
72
74
 Response
 Recovery
NH
3
 Conc./ ppm
R
e
s
p
o
n
s
e
 t
im
e
 /
s
340
360
380
400
420
440
460
480
500
520
540
R
e
c
o
v
e
ry
 tim
e
 /s
 
 
Fig. 7  Variation of response and recovery time of the PANi / TiO2 thin film sensor 
with NH3 concentration 
 
 
 
 
 FABRICATION OF POLYANILINE / TIO2 NANOCOMPOSITE… 1063 
4. CONCLUSIONS 
 
The PANi/TiO2 thin film sensor was fabricated by spin coating technique. The 
composites have poorer crystallinity than TiO2, because of amorphous 
structure of PANi. But crystallinity of nanocomposites has been improved 
with increasing percentage of TiO2 nanoparticles. It can be seen that 
PANi/TiO2 film has a very porous structure, interconnected network of fibers 
and high surface area which contributes to a rapid diffusion of dopants into 
the film. The cross sensitivity of thin film sensor indicate that the sensor 
exhibit selectivity to ammonia (NH3). The gas sensing measurements were 
carried out for different concentrations of NH3 at room temperature. It is 
observed that the response slows down at higher concentration; this may be 
due less availability of surface area with possible reaction sites on surface of 
the film. Moreover, as concentration of NH3 increases, the response time 
decreases while recovery time increases, which can be attributed to the 
varying adsorption and desorption rates of an ambient gas with increasing 
concentration. 
 
 Authors (VBP) are grateful to the Department of Science and Technology, 
New Delhi for financial support through the scheme no. SR/FTP/PS-09/2007. 
Thanks are also extended to Dr. Rashinkar, Department of Chemistry, SUK 
for FTIR facility, Prof. Lonikar, School of chemical Sciences, SUS for UV 
facility and Dr. P.S. Patil, Department of Physics, Shivaji University, 
Kolhapur for providing SEM facility. 
 
REFERENCES 
1. G.K. Prasad, T.P. Radhakrishnan, D.S. Kumar, M.G. Krishna, Sens. Actuat. B-Chem. 
106, 626 (2005). 
2. C. Wrenn, Occu. Health Saf. 69b, 64 (2000). 
3. R.L.N. Chandrakanthi, M.A. Careem, Thin Solid Films 417, 51 (2002). 
4. P.R. Somani, R. Marimuthu, U.P. Mulik, S.R. Mulik, S.R. Sanikar, D.P. Amalnerkar, 
Synth. Met. 106, 45 (1999). 
5. Y. He, Mater. Chem. Phys. 92, 134 (2005). 
6. S.A. Chen, K.R. Chuang, C.I. Chao, H.T. Lee, Synth. Met. 82, 207 (1996). 
7. A.G. MacDiarmid, L.S. Yang, W.S. Huang, B.D. Humphrey, Synth Met. 18, 393 (1987). 
8. D. Verma, V. Dutta, Sens. Actuat. B-Chem. 134, 373 (2008). 
9. M. Mastuguchi, A. Okamoto, Y. Sakai, Sens. Actuat. B-Chem. 94, 46 (2003). 
10. F.Y. Chaung, S.M Yang, Synth. Met. 152, 361 (2005). 
11. A.Z. Sadek, W. Wlodarski, K. Shin, R. Bkaner, K. Kalantarzadeh, Nanotechnology 17, 
4488 (2006). 
12. D.S. Dhawale, R.R. Salunkhe, U.M. Patil, K.V. Gurav, A.M. More, C.D. Lokhande, 
Sens. Actuat. B-Chem. 134, 988 (2008). 
13. R. Zeggari, B. Wacogne, C. Pieralli, C. Roux, T. Gharbi, Sens. Actuat. B-Chem. 125, 
664 (2007). 
14. L. Geng, Y. Zhao, X. Huang, S. Wang, S. Zhang, S. Wu, Sens. Actuat. B-Chem. 120, 
568 (2007). 
15. J. Wang, I. Matsubara, N. Murayama, S. Woosuck, N. Izu, Thin Solid Films 514, 329 (2006). 
16. S.G. Pawar, S.L. Patil, M.A. Chougule, A.T. Mane, D.M. Jundale, V.B. Patil, Int. J. 
Polym. Mater. 59, 777 (2010). 
17. S.G. Pawar, S.L. Patil, A.T. Mane, B.T. Raut, V.B. Patil, Archives of Applied Science 
Research 1(2), 109 (2009). 
18. S.G. Pawar, S.L. Patil, M.A. Chougule, D.M. Jundale, V.B. Patil, J. Mater. Sci: Mater. 
Electron. 22, 260 (2011). 
19. H. Tai, Y. Juang, G. Xie, J. Yu, X. Chen, Z. Ying, Sens. Actuat. B-Chem 129, 319 (2008). 


English

https://essuir.sumdu.edu.ua/bitstream/123456789/27910/1/Pawar.pdf

Fabrication of polyaniline/TiO2 nanocomposite ammonia vapor sensor

Abstract

Similar works

Full text

Available Versions

Electronic Sumy State University Institutional Repository

Directory of Open Access Journals

SocioEconomic Challenges Journal (Sumy State University)