- Email: [email protected]
Composites of various cation exchanged forms of mesoporous zeolite A with polypyrrole-thermal, spectroscopic and gas sensing studies
Accepted Manuscript Composites of various cation exchanged forms of mesoporous zeolite A with polypyrrole-thermal, spectroscopic and gas sensing studies Rawoof A. Naikoo, Sami U. Bhat, Muzzaffar A. Mir, Radha Tomar PII:
S1387-1811(17)30082-3
DOI:
10.1016/j.micromeso.2017.02.027
Reference:
MICMAT 8137
To appear in:
Microporous and Mesoporous Materials
Received Date: 28 October 2016 Revised Date:
21 January 2017
Accepted Date: 9 February 2017
Please cite this article as: R.A. Naikoo, S.U. Bhat, M.A. Mir, R. Tomar, Composites of various cation exchanged forms of mesoporous zeolite A with polypyrrole-thermal, spectroscopic and gas sensing studies, Microporous and Mesoporous Materials (2017), doi: 10.1016/j.micromeso.2017.02.027. 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
AC C
EP
TE D
M AN U
SC
RI PT
Graphical Abstract
ACCEPTED MANUSCRIPT
Composites of various cation exchanged forms of mesoporous zeolite A with Polypyrrole-Thermal, spectroscopic and gas sensing studies Rawoof A. Naikoo1, Sami U. Bhat1, Muzzaffar A. Mir1 & Radha Tomar1* School of studies in Chemistry, Jiwaji University, Gwalior (M.P)-474011-India *[email protected], +91-9425341452
RI PT
1
Abstract
TE D
M AN U
SC
Composites of polypyrrole with various cation exchanged forms of Zeolite A were successfully synthesized via chemical oxidative polymerization of Pyrrole (Py) in presence of a dispersion of A-zeolite (powder) in deionised water using anhydrous FeCl3 as an oxidant. The composites were characterized spectroscopically by Fourier Transform-Infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopic (SEM) and Energy dispersive X-ray analysis (EDXA) for their nature, morphology and elemental analysis. Thermo-gravimetric analysis (TGA) was carried out for the thermal stability of the composites. Gas sensing studies were carried out for the carbon monoxide gas at the concentrations ranging from 5 ppm to 1000 ppm. The effects of cation type, zeolite content and CO concentration on the response of the composites were also investigated. The sensitivity of synthesized composites was found to obey the following order: Na-A/PPy > H-A/PPy > Fe-A/PPy > Cu-A/PPy > PPy depending upon the ionic radius of the cation present in the zeolite-polymer composites and the electronegativity. The response of the Na-A/PPy composite increases from 19.36% to 40.00% as the zeolite content was increased from 10 % to 60 % (w/w %). This increase in the sensitivity by increasing the zeolite content is due to the increase in the surface area of the composite. Keywords: Zeolites; polypyrrole; composites; sensing; carbon monoxide 1. Introduction
AC C
EP
The formation of a conducting polymer within and outside an inorganic host has been considered as an important method to fabricate a new type of hybrid materials which are having both the unique properties of organic polymers and the mechanical strength and chemical properties of inorganic hosts [1]. These composites are having wide range of applications in electronic devices due to their superior electronic, magnetic, optical and electrical properties as well as in catalytic applications [2–4]. Zeolites are considered to be one of the most recommended host materials due to their well-ordered channel and pore systems that can serve as hosts for growing of conducting polymers. The anionic groups present in the zeolite frameworks are expected to function as the dopants during the polymerization [5–9]. Polyaniline [10], polypyrrole (PPy) [11], polythiophene [12] and polyacrylonitrile [13] have been reported to grow in channels and cages of different zeolites both in electrochemical and chemical polymerization. As a sensing layer, zeolites are very advantageous because of their high thermal stability and chemical resistance. Characteristic molecular sieving properties have been explored and utilized in various gas sensing applications so as to detect toxic gases and other large organic 1
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
molecules [14-24]. Fabrication of polymer matrix within and outside an inorganic host is of great significance since this enables us to combine characteristics of both the parent constituents as a consequence of their molecular level interaction. Zeolites are the most favorable host materials because of their highly ordered pore systems, channels and cages of different shapes and dimensions and having their negatively charge-balanced with exchangeable cations [25]. Besides, the intercalation of a conducting polymer into a porous zeolite, reducing its aging rate and protects the former from degradation. Conductive polypyrrole (PPy) is found to be one of the most promising conductive polymers for many applications because of its ease of synthesis, high environmental stability and high conductivity [26, 27]. Its electrical conductivity is found to be highly tunable by changing the synthesis conditions [28], the oxidation state [29], counter ions or dopants [30, 31], solvents used in the fabrication processes [32], the chemical treatments [33, 34], and the heat treatments [34]. Carbon monoxide (CO) is odorless, colorless and tasteless gas which can hinder the proper transportation of oxygen in human blood [35]. Various gas sensing materials have been developed for CO detection; they are required to have long life times, offer high selectivity and low manufacturing costs [36]. Conductive polymers were reported to have many advantages over conventional metal sensors; they are less expensive, lighter, and can be operated at lower applied temperature and voltage [37]. Recently, many conductive polymers have been reported as gas sensing materials [38]. To enhance or induce the interaction between target gases and the CPs, zeolite molecular sieves have been employed [39] due to their nanometric sized channel systems that provide size and shape selective properties. The adsorption properties of zeolite depend on the pore size, zeolite type, temperature and the type of cation residing in the pore. There are two well-known mechanisms reported for the selective adsorption of zeolites [24]. First, the molecular sieve property, whereby molecules small enough to pass through are adsorbed while larger molecules are restricted. Second is the zeolite chemical composition. Si/Al ratio is found to be the major factor controlling the hydrophilic/hydrophobic properties of materials. The incorporation of specific cations within a zeolite framework by using the cation exchange method can significantly alter the gas adsorption properties. This work is aimed at fabricating the composites between Polypyrrole and various cation exchanged forms of zeolite A and their spectroscopic, thermal and gas sensing studies. The influences of the cation type, concentration of CO, zeolite amount on the response of the composites were also studied. 2. Experimental
2.1 Synthesis of Zeolite A 0.723 g of sodium hydroxide (Aldrich) was completely dissolved in 80 ml of deionized water which was then distributed into two equal halves. To first half, 8.258 g of sodium aluminate (Riedel-de Haën) was gently mixed till clear solution was obtained and to the second half; 15.48 g of sodium metasilicate (Aldrich) was added. Both the halves were quickly mixed and a thick gel was formed. Crystallization was carried out in a polypropylene bottle at 99oC for 2
ACCEPTED MANUSCRIPT
RI PT
3 h in an oven under static conditions. The material formed i.e Na-zeolite A was washed till the filtrate attained the pH ≤ 9 and finally dried overnight at 100oC. 2.2 Conversion of zeolite A in H-form Na-form of zeolite A was converted into H-form by mixing 9.0 g of synthesized zeolite, 7.230 g of NH4NO3 and 13.80 ml of deionized water. The mixture was stirred at 80oC for 30 min. Then the material was filtered under suction and washed with deionized water. After the removal of nitrates, the resulting material, NH4-zeolite, was placed in an oven at 60oC for 24 h. The ammonium form of zeolite was converted into H-form by calcinations over 60 min at 500oC.
M AN U
SC
2.3 Conversion into various cation exchanged forms of zeolite A Na-form of zeolite A was converted into various cation exchanged forms by exchanging + Na ion present on the parent zeolite A with other metal ions like Fe2+ and Cu2+ by stirring zeolite material in their corresponding alkali metal salt solutions. A mixture containing 5 g of zeolite A and 144 ml of 0.0125 M metal nitrate {Fe(NO3)2, Cu(NO3)2} was stirred at 80oC for 24 h. The sample was dried for 10 h at 120oC and calcined at 450oC for 3 h to remove nitrate ions from the surface.
EP
TE D
2.4 Synthesis of Zeolite A/Polypyrrole Composites 1.0 g of Zeolite-A powder was taken in a conical flask containing 35 ml of deionised water and sonicated until complete dispersion was observed. 0.5 ml of pyrrole (Py) was injected to it and again sonicated for 10 min so that the monomer gets uniformly dispersed in the zeolite pores. Polymerization was started by adding an oxidant solution (FeCl3) drop by drop into the dispersion and the reaction mixture was kept under magnetic stirring for 2 h at room temperature. 25 ml of acetone was added to stop the polymerization reaction and to remove excess of FeCl3. The black precipitate formed was washed alternatively with deionized water and methanol for several times and finally dried at 50oC under vacuum for 1 h.
AC C
2.5 Fabrication of Zeolite A/ Polypyrrole sensor films Composites were first dissolved in the appropriate amount of N-Methyl pyrrolidone and sonicated for about 30 min. Thereafter, Sensor films were prepared by drop casting technique on the glass substrate having the coated electrodes of silver paste. The sensor film was finally dried at 50oC for 48 h. 2.6 Materials characterization and instrumentation Powder X-ray diffraction was recorded on Shimadzu XRD 6000 equipment operating at 40 kV and 30 mA in the 2θ range from 2o to 60o. SEM Micrograph was obtained by using the JEOL JSM 5800 instrument at 10,000 and 50,000 magnifications. Fourier transform infrared (FT-IR) spectra were recorded by PerkinElmer (Spectrum RX-IFTIR) spectrometer using KBr pellets over a range from 450 cm-1 to 4000 cm-1. TGA/DSC studies were carried out on the SDT Q600 V20.9. 3
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
2.7 Gas sensing measurement A custom made two point probe connected with data acquisition system was used for measuring the response (in terms of resistance) of the composites towards the CO gas (shown in fig. 1). The gas detection unit consists of two chambers of equal volume: a mixing chamber is connected in series with a working chamber. Temperature and pressure in both chambers were controlled and monitored. The operating temperature was fixed at 30±2 ◦C during the experiment. In the serial dilution method, CO concentration was successively reduced from 10000 ppm to 1000 ppm, 500 ppm, 100 ppm, 50 ppm, and 5 ppm. Initially both the chambers contain nitrogen till the sample shows a constant resistance value. The resistance value was recorded. Then nitrogen was evacuated from the chamber and 5 ppm of CO/N2 was injected into the mixing chamber. The concentration of CO was checked by CO detector. Then the gas was allowed to enter into the working chamber and the resistance value was recorded. After the saturation in the resistance value was obtained the gas was evacuated from the working chamber and N2 was injected into the working chamber.
Fig. 1 Systematic diagram for measuring the sensitivity of the thin film sensors
3. Results and Discussion
3.1 FTIR spectra The bands observed at 1055 cm-1, 794 cm-1 and 467 cm-1 correspond to internal vibrations of Si–O–Si and Si–O–Al bridges in zeolite. The bands observed at 1638 cm-1 and between 3200 cm-1 and 3700 cm-1 in the zeolite originate from water absorbed by zeolite [40]. Fig. 2 shows FTIR spectra of different forms of Zeolite A. The absorption bands at around 500cm-1 is attributed to Si, Al-O bond and those at 1000 cm-1 and 750 cm-1 respectively are due to 4
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
asymmetric and symmetric stretches of the zeolite network. A band for OH group was observed at 3485 cm-1. It is found that spectra of different cation exchanged forms of zeolite A are similar indicating their structure stability; however there may be variation in transmittance % due to presence of different cations [41]. Spectrum of pure PPy exhibits the characteristic absorption bands at 1513 cm-1 (C–C and C=C stretching vibrations), 1422 cm-1 (C–N stretching vibration), 1265 cm-1 (C–H or C–N in-plane vibration) and 1075 cm-1 (C–H and N–H in-plane deformation vibrations) [42, 43]. Fig. 3 represents the FTIR spectra of composites of Polypyrrole with various cation exchanged forms of zeolite-A. It is clearly seen that the characteristic peaks of PPy (3370 cm-1, 1560 cm-1and 1340 cm-1) are present indicating the presence of polypyrrole in the composite. Also the characteristic peaks of zeolite A (1000 cm-1, 740 cm-1, 471 cm-1) in the composites show presence of zeolite in the composites.
80 70
Na-A H-A Fe-A Cu-A
50 40
TE D
30 20 10 0 4000
3500
3000
2500
2000
1500
1000
500
-1
EP
Wavenumber (cm )
Fig. 2 FTIR spectra of various cation exchanged forms of zeolite A
Fig. 3 FTIR spectra of composites of PPy with various cation exchanged forms of Zeolite-A
AC C
Transm ittance (%)
60
3.2 XRD analysis
Fig. 4 shows the X-ray diffraction patterns of synthesized zeolite-A and its various cation exchanged forms. From the Fig. 4, it is seen that the degree of crystallinity is very high and all the materials are crystalline in nature without having any amorphous phase. Also, it is found that there is little change particularly in the intensity of peaks in the all the forms, indicating that there is no significant structural change in converting the Na zeolite-A into its various cation exchanged forms. All forms of the zeolite are showing the sharp peaks at 2 theta values of 25o.
5
ACCEPTED MANUSCRIPT
Zeolite Na-A
0
10
20
30
2-Theta(deg.)
40
50
Na-A/PPy H-A/PPy Fe-A/PPy Cu-A/PPy
10
20
30
40
50
60
2-Theta (deg.)
Fig. 5 XRD spectra of composites of PPy with various cation exchanged forms of Zeolite A
TE D
Fig. 4 XRD spectra of various cation exchanged forms of Zeolite A
3.3 SEM analysis
RI PT
2000 1500 1000 500 0
Zeolite H-A
320 300 280 260 240 220 200 180 160 140 120 100 80
SC
Intensity
1600 1200 800 400 0
Zeolite Fe-A
Intensity
Intensity
1600 1200 800 400 0
Zeolite Cu-A
M AN U
Intensity
2000 1500 1000 500 0
Intensity
The XRD spectra of Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy composites are shown in Fig. 5. In each case, a broad peak at about 2θ =26o was observed. The broad peaks are characteristic of amorphous PPy [44]. However, the intensity of peaks in these composites was found different which may be attributed to the presence of different cations.
AC C
EP
The synthesized materials Na-A, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy were characterized for morphologies by FEG-SEM analysis at 10,000 and 50,000 magnifications as shown in Fig. 6 (a-e). From SEM images, zeolite-A particles appear to have a cuboid shape with excellent crystal edges and have particle size in 2–5 µm range as shown in the Fig. 6a. FEG-SEM image of PPy have cauliflower like morphology and its grain size varies from ~130 nm to ~200 nm [45]. Fig. 6 b-e shows the presence of cuboids and cauliflower type structures indicating the formation of zeolite/polypyrrole composites.
6
ACCEPTED MANUSCRIPT
(b)
SC
RI PT
(a)
(d)
(e)
AC C
EP
TE D
M AN U
(c)
Fig. 6 SEM micrographs of a) Zeolite Na-A b) Na-A/PPy c) H-A/ PPy d) Fe-A/PPy and e) Cu-A/PPy
7
ACCEPTED MANUSCRIPT
3.4 EDS analysis
M AN U
TE D
(a)
SC
RI PT
Elemental analysis for Si, O, Al, C, N, Cl, Na, Fe and Cu in the Na-A/PPy, H-A/PPy, FeA/PPy and Cu-A/PPy composites were carried out using energy dispersive X-ray microanalysis (Fig. 7 a-d). In the EDXA spectra, all the composites were found to contain the elements like Si, O, Al, C, N and Cl indicating the successful synthesis of zeolite/Polypyrrole composites since Si, O, Al and Cl are the constituent elements of zeolite A and C & N of Polypyrrole. The presence of Na in Na-A/PPy, Fe in Fe-A/PPy and Cu in Cu-A/PPy composites validate the successful conversion of Na-A into various cation exchanged forms. No iron was found in the Na-A/PPy, H-A/PPy and Cu-A/PPy composites due to the repeated washing after the synthesis of the composite. Chlorine, however retained in the structure of the composites due to its role as the doping anion (chloride) in the synthesis of polypyrrole.
(d)
AC C
EP
(c)
(b)
Fig. 7 EDX spectra of a) Na-A/PPy b) H-A/PPy c) Fe-A/PPy and d) Cu-A/PPy
8
ACCEPTED MANUSCRIPT
SC
RI PT
3.5 Thermal analysis The thermal stability of the zeolite A/PPy composites was studied by TGA. Fig. 8 a-d presents the curves of weight loss versus temperature of Zeolite A/PPy composites. A weight loss of 27.50% for Na-A/PPy, 30.02% for H-A/PPy, 31.18% for Fe-A/PPy and 26.45 % for CuA/PPy which is attributed to expulsion of water has been observed upto the temperature of 200oC. Further, the degradation process of PPy matrix in the composites was initiated at 200oC and continued until 700oC where the weight loss reached up to 55.11% for Na-A/PPy, 52.22% H-A/PPy, 54.69% Fe-A/PPy and 56.78% Cu-A/PPy. From the thermal studies of the composites shown in table 1, it can be concluded that the thermal stability of the composites follow the order as: H-A/PPy> Na-A/PPy > Fe-A/PPy >Cu-A/PPy.
(b)
TE D
M AN U
(a)
(d)
AC C
EP
(c)
Fig. 8 TGA thermograms of a) Na-A/PPy b) H-A/PPy c) Fe-A/PPy and d) Cu-A/PPy
9
ACCEPTED MANUSCRIPT
Table 1 Weight loss % of zeolite A/PPy composites at different temperatures Weight loss % upto 200oC
Weight loss % upto 700oC
Weight loss % upto 1000oC
Na-A/PPy
27.50
55.11
66.83
H-A/PPy
30.02
52.22
Fe-A/PPy
31.18
54.69
Cu-A/PPy
26.45
56.78
RI PT
Materials
59.01
66.96
SC
69.02
3.6 Response to CO gas
M AN U
For the sensing of CO, the samples are mounted on the suitable sample holder and the electrical connections are made by silver paste. The change in value of resistance is measured at different concentrations of CO. The sensitivity (S) of sensors is calculated by using the following equation
S% =
100
AC C
EP
TE D
Where S % is the Sensitivity of the sample for the gas, Rg is the saturation value of resistance in presence of gas and Ro is the resistance in presence of nitrogen. The CO gas sensing of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy thin film sensors are measured under nearly same practical conditions i.e. atmospheric pressure, room temperature and N2 as a reference gas environment. Sensing films are firstly exposed to clean dry air for 10 min. to record the base value of the sensor resistance. The nitrogen gas is used for the recovery of the sensors. From Fig. 9, it is observed that the Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy thin film sensors are having higher sensitivity to CO as compared to the PPy thin film sensor. Since zeolite is having a porous structure, the gas molecules are provided with large surface area to get adsorbed and interact with the polymer chains. Hence, adding zeolite to the polymer provides adsorption sites for the gas molecules to interact with the polymer chains and therefore response increases. From Fig. 9 and Table 2, it is found that the response time of PPy, Na-A/PPy, HA/PPy, Fe-A/PPy and Cu-A/PPy, at 5 ppm were 245, 180, 204, 239, and 262 sec. respectively. The reason is that by addition of zeolite, surface area of the sensor increases and more CO molecules get adsorbed. The slightly higher value of response times for Fe-X/PPy and Cu-X/PPy may be attributed to the interaction of CO molecules with the Fe and Cu ions and thus less number of CO are available for interaction with polymer chains. The reversibility of these sensors was checked by flushing of N2 and it was found that after flushing, the sensors retained their original value of resistance. The recovery time of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy was found to be 235, 121, 163, 211 and 222 sec. respectively. The higher values of 10
ACCEPTED MANUSCRIPT
80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 -5
PPy Cu-A/PPy Fe-A/PPy H-A/PPy Na-A/PPy
RI PT
1000 PPM
500 PPM
100 PPM
SC
50 PPM 5 PPM
-200
0
200
M AN U
Sensitivity ( % )
recovery times for Fe-A/PPy, and Cu-A/PPy were attributed to the stronger interaction of CO molecules with Fe and Cu ions.
400
600
800 1000 1200 1400 1600 1800
Time (sec.)
Fig. 9 The CO sensitivity of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy composites at 5 ppm to 1000 ppm
CO concentr ation (ppm)
PPy
TE D
Table 2 Sensitivity (S%), response time and recovery time of PPy, PPy, Na-A/PPy, HA/PPy, Fe-A/PPy and Cu-A/PPy composites at various ppm concentration of CO gas Na-A/PPy
Respo nse Time (sec.)
Max. S %
Max. S%
Respo nse Time (sec.)
5
6.36
245
16.52
50
11.83
221
100
14.94
500 1000
180
13.29
26.44
144
202
39.66
20.41
187
26.62
163
235
Respo nse Time (sec.)
Reco very Time (sec.)
Fe-A/PPy Max. S%
Respo nse Time (sec.)
204
9.09
20.88
180
138
28.48
56.02
119
74.38
104
AC C
Reco very Time (sec.)
EP
Max. S%
H-A/PPy
121
Reco very Time (sec.)
Cu-A/PPy Max. S%
Resp onse Tim e (sec. )
239
8.58
262
15.34
223
14.07
235
161
24.43
202
18.80
226
37.97
144
33.52
181
26.42
207
51.26
125
40.90
164
31.62
181
163
Reco very Time (sec.)
211
11
Reco very Time (sec.)
222
ACCEPTED MANUSCRIPT
SC
RI PT
Fig. 10 shows the Sensitivity values of polypyrrole and the composites in presence of CO from 5 ppm and 1000 ppm. When PPy is exposed to CO concentration of 5 ppm, it shows a sensitivity value of 6.36 %. The sensitivity of PPy towards CO increases from 6.36 to 26.62 % as the CO concentration is increased from 5 ppm to 1000 ppm. When the concentration is increased, more and more CO molecules come in contact with the polymer chains and the sensitivity value increases. From Fig. 10 and Table 2, it can be seen that the sensitivity of PPy towards CO increases when zeolite is added to it. This is because zeolite is having a porous structure, the gas molecules are provided with high surface area to get adsorbed and interact with the polymer chains. Hence, adding zeolite to the polymer provides adsorption sites for the gas molecules to interact with the polymer chains and therefore sensitivity value increases.
PPy Cu-A/PPy Fe-A/PPy H-A/PPy Na-A/PPy
60 50 40 30 20 10 0
TE D
Sensitivity (%)
70
M AN U
80
0
200
400
600
800
1000
1200
Concentration (PPM)
EP
Fig. 10 Sensitivity (%) vs concentration graph of PPy and Zeolite A/PPy Composites. The BET surface area, Langmuir surface area and total pore volume values of the
AC C
synthesized materials are shown in the table 3. As shown in the table, PPy showed least surface area (35.9065 m²/g) and pore volume (0.054552 cm³/g) as compared to the composites. Among the composites, Na-A/PPy is having higher surface area value (58.8334 m²/g) and pore volume (0.098007 cm³/g) and Cu-A/PPy shows the least surface area value (39.9215 m²/g) and pore volume (0.071218 cm³/g).The higher sensitivity value of the Na-A/PPy composite is confirmed from the BET analysis, since Adsorption of gases is a surface phenomenon. For BET surface area, adsorption desorption isotherms are shown in figure 11.
12
ACCEPTED MANUSCRIPT
Table 3 Surface area and pore volume analysis of PPy and Zeolite-A/PPy composites
BET
Langmuir
H-A/PPy
53.3294 m²/g
81.2715 m²/g
Na-A/PPy
58.8334 m²/g
84.5036 m²/g
PPy
35.9065 m²/g
51.4095 m²/g
Fe-A/PPy
47.9799 m²/g
68.8796 m²/g
Cu-A/PPy
39.9215 m²/g
57.5399 m²/g
Sample Name
0.094963 cm³/g
0.098007 cm³/g 0.054552 cm³/g 0.088383 cm³/g 0.071218 cm³/g
M AN U
H-A/PPy Na-A/PPy PPy Fe-A/PPy Cu-A/PPy
60 50 40 30 20
TE D
Quantity adsorbed (cm3/g STP)
70
Pore volume (cm3/g)
RI PT
Surface Area (m2/g)
SC
Surface area (m2/g)
10
0
0.0
0.2
0.4
0.6
0.8
1.0
EP
Relative Pressure (P/PO)
AC C
Fig. 11 Adsorption-desorption isotherms of PPy and Zeolite A/PPy composites.
3.7 Effect of cation type on the sensitivity of Zeolite A/PPy composites Fig. 12 shows the effect of cation type on the sensitivity of zeolite A/PPy composites towards CO at 100 ppm. For this purpose four types of cations were selected: 1) Na+ 2) Fe2+ 3) Cu2+ 4) H+. In all these composites, the zeolite content was kept at a constant value of 50%. From the Fig. 12, it is clearly evident that the sensitivity of Na+-A/ PPy, H+-A /PPy, Fe2+-A/PPy, Cu2+-A/PPy and PPy at 100 ppm of CO concentration is 39.66%, 28.43%, 24.43% , 18.8% and 11.83% respectively.
13
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
The sensitivity value of these synthesized composites depends up on two factors- i) ionic radius of the cation present in the zeolite/polymer composites and ii) Electronegativity. It is clearly evident that Na+-A/PPy shows larger sensitivity to CO than other cationic forms and PPy. The reason of having the largest sensitivity of Na+-A/PPy is because of its smallest electronegativity and large ionic radius. The sensitivity obeys the following order: Na+-A/PPy > H+-A/PPy > Fe2+-A/PPy > Cu2+-A/PPy > PPy. It is found that the electronegativity of Na+, Fe2+, Cu2+, H+ is 0.93, 1.83, 1.9, 2.1 with corresponding ionic radii 186 pm, 124 pm, 128 pm, 78 pm respectively. In case of Na+-form because of its small electronegativity and large ionic radius, the gas molecules do not interact with the ion present in the zeolite instead interact with the polymer chain and hence result in large sensitivity. However for Cu2+-A/PPy, there is strong interaction of the gas molecules with the Cu ion present in the composite than with the polymer chain resulting in less sensitivity. It is clearly evident that the sensitivity of PPy towards CO increased as zeolite is added to it. This is because zeolites are having three-dimensional (3D) frameworks with an open porosity that gives rise to an exceptionally high surface area. Thus on adding zeolite to PPy, the surface area increases and more CO molecules get adsorbed to get interacted with the polymer chains
40
Sensitivity vs cation type at 100 ppm
25 20 15 10
AC C
5
TE D
30
EP
Sensitivity(%)
35
Na
H
Fe
Cu
PPy
Cation Type
Fig. 12 Sensitivity of PPy and zeolite A/PPy composites of various cation types when exposed to 100 ppm of CO concentration
14
ACCEPTED MANUSCRIPT
3.8 Effect of zeolite content on the sensitivity of Zeolite A/PPy composites
SC
RI PT
The sensitivity of Na-A/PPy towards CO at 100 ppm concentration at various zeolite contents is shown in Fig. 13. The sensitivity of the Na-A/PPy composite increases from 19.36% to 40.00% as the zeolite content was increased from 10 % to 60 % (w/w %). This increase in the sensitivity by increasing the zeolite content is due to the increase in the surface area of the composite. Due to which large no. of active sites become available for gas molecules to be adsorbed so that they can penetrate deep inside the composite and interact with the PPy chains. Beyond 60 % of zeolite content there is no further increase in the sensitivity of the Na-A/PPy composite and attains almost a steady state. This steady state sensitivity beyond 60 % of zeolite content is because all the CO molecules present get their active sites and further increasing the active sites are of no mean. 45 Na-A/PPy at 100 ppm of CO
M AN U
Sensitivity (%)
40 35 30 25 20 15
10
20
30
TE D
0
40
50
60
70
80
Zeolite content (% w/w)
EP
Fig. 13 Sensitivity of Na-A/PPy at 100ppm of CO vs zeolite content
3.9 Polypyrrole/Zeolite A sensitivity to CO: Effect of the subsequent runs
AC C
The Sensitivity of Na-A/PPy at 500 ppm of CO was found to be 55.37%, 53.64%, 49.36% and 43.66 % during 1st, 2nd, 3rd and 4th cyclic intervals respectively. It has been found that there is little loss in the sensitivity after repeating the cyclic interval upto 3 times. However, after 3 runs there is significant loss in the sensitivity value. The reason is that during the successive runs, some gas molecules may get adsorbed permanently and thus cause reduction in the sensitivity of the composite. Hence, the sensitivity of the composite goes on decreasing with the cyclic interval as shown in Fig. 14.
15
ACCEPTED MANUSCRIPT
Na-A/PPY at 500 ppm of CO
50 45 40 35 0
1
2
3
Cyclic interval
4
RI PT
Sensitivity (%)
55
5
SC
Fig. 14 Sensitivity of Na-A/PPy towards CO at 500 ppm for various intervals
M AN U
4. Conclusion
AC C
EP
TE D
Composites of polypyrrole with various cation exchanged forms of Zeolite A were successfully synthesized via chemical oxidative polymerization of Pyrrole (Py) in presence of a dispersion of A-zeolite (powder) in deionised water using anhydrous FeCl3 as an oxidant. The composites were characterized by FTIR, Powder XRD, SEM, EDXA and TGA. Formation of Polypyrrole (PPy) and its subsequent incorporation in the zeolite A/PPy composites was confirmed by Fourier Transform-Infrared (FTIR) spectral studies and X-ray diffraction (XRD) pattern analysis. Scanning electron microscopic (SEM) analysis revealed the external morphology of the zeolite A (average diameter of 2-5µm) and various composites (average size of about ~130 nm to ~200 nm). Energy dispersive X-ray analysis (EDXA) confirmed the presence of various constituents viz. metal ions, silicon, Aluminium, Oxygen, Nitrogen and Carbon in the composites. The presence of Na in Na-A/PPy, Fe in Fe-A/PPy and Cu in CuA/PPy was confirmed by EDX analysis. The effects of cation type, zeolite content, CO concentration on the sensitivity of the composites towards the CO were studied. The response time of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy, at 5 ppm were 245, 180, 204, 239, and 262 sec respectively. The reason is that by addition of zeolite, surface area of the sensor increases and more CO molecules get adsorbed. The recovery time of PPy, NaA/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy was found to be 235, 121, 163, 211 and 222 sec. respectively. The higher values of recovery times for Fe-X/PPy, and Cu-X/PPy were attributed to the stronger interaction of CO molecules with Fe and Cu ions. The sensitivity of the Na-A/PPy composite increases from 19.36% to 40.00% as the zeolite content was increased from 10 % to 60 % (w/w %). This increase in the sensitivity by increasing the zeolite content is due to the increase in the surface area of the composite. The sensitivity of synthesized composites was found to obey the following order: Na-A/PPy > H-A/PPy > Fe-A/PPy > Cu-A/PPy > PPy depending upon the ionic radius of the cation present in the zeolite-polymer composites and the electronegativity. 16
ACCEPTED MANUSCRIPT
Acknowledgements
RI PT
The authors are highly thankful to IIT Kanpur and Jamia Millia Islamia University for carrying out characterization of the synthesized materials. The authors are also thankful to School of studies in Chemistry, Jiwaji University, Gwalior and DRDE, Gwalior for providing the necessary facilities to carry out the experimental work. References
AC C
EP
TE D
M AN U
SC
1. R. Gangopadhyay and A. De, Chem. Mater., 2000, 12, 608– 621. 2. T. G. Jiu, H. B. Liu, H. Y. Gan, Y. L. Li, S. Q. Xiao, H. M. Li, Y. Liu, F. S. Lu, L. Jiang and D. B. Zhu, Synth. Met., 2005, 148, 313–319. 3. H. Rein, K. Ruckpaul and W. Haberditzl, Chem. Phys. Lett., 1973, 20, 71–76. 4. A. P. Alivisators, Science, 1996, 271, 933–937. 5. O. Kresnawahjuesa, G. H. K¨uhl, R. J. Gorte and C. A. Quierini, J. Catal., 2002, 210, 106–115. 6. L. B. McCusker and C. Baerlocher, in Introduction to Zeolite Science and Practice, ed. J. Cejka, H. Van Bekkum, A. Corma and F. Sch¨uth, Elsevier B.V., Amsterdam, 2007. 7. T. Bein and P. Enzel, Angew. Chem., Int. Ed. Engl., 1989, 28(12), 1692–1694. 8. Y. Kitayama, H. Katoh, T. Kodama and J. Abe, Appl. Surf. Sci., 1997, 121/122, 331– 334. 9. G. Larsen, G. L. Haller and M. Marquez, J. Phys. Chem., 1992, 96, 4145–4148. 10. P. Enzel and T. Bein, J. Phys. Chem., 1989, 93, 6270–6272. 11. M. Nakayama, J. Yano, K. K. Nakaoka and K. Ogura, Synth. Met., 2002, 128, 57–62. 12. P. Enzel and T. Bein, Synth. Met., 1993, 55–57, 1238–1245. 13. P. Enzel, J. J. Zoller and T. Bein, J. Chem. Soc., Chem. Commun., 1992, 8, 633–635. 14. R. Gangopadhyay, A. De, Sens. Actuators B 77 (2001) 326–329. 15. S. Jain, S. Chakane, A.B. Sumui, V.N. Krishnamurthy, S.V. Bhoraskar, Sens. Actuators B 96 (2003) 124–129. 16. K.H. Hong, K.W. Oh, T.J. Kang, J. Appl. Polym. Sci. 92 (2004) 37–42. 17. K. Fukui, S. Nishida, Sens. Actuators B 45 (1997) 101–106. 18. G. Li, S. Kawi, Sens. Actuators B 59 (1999) 1–8. 19. O. Hugon, M. Sauvan, P. Benech, C. Pijolat, F. Lefebvre, Sens. Actuators B 67 (2000) 235–243. 20. I. Sasaki, H. Tsuchiya, M. Nishioka, Sens. Actuators B 85 (2002) 26–33. 21. M. Vilaseca, J. Coronas, A. Cirera, A. Cornet, J.R. Morante, J. Santamaria, Catal. Today 82 (2003) 179–185. 22. J. Zhou, P. Li, S. Zhang, Y. Long, F. Zhou, Y. Huang, P. Yang, M. Bao, Sens. Actuators B 94 (2003) 337–342. 23. H. Huang, J. Zhou, S. Chen, J. Zeng, Y. Huang, Sens. Actuators B 101 (2004) 316–321.
17
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
24. M. Vilaseca, C. Yague, J. Coronas, J. Santamaria, Sens. Actuat. B-Chem. 117, 2006, 143150. 25. M. Nakyama, J. Yano, K. Nakaoka, K. Ogura Synth Met. 138, 2003, 419-22. 26. M. Salmon, K.K. Kanazawa, A.F. Diaz, M. Krounbi, J. Polym. Sci., Polym. Lett. Ed. 20 (1982) 187. 27. S.A. Chen, C.S. Liao, Macromolecules 26 (1993) 2810-2816. 28. K.C. Khulbe, R.S. Mann, J. Polym. Sci. 20 (1982) 1089-1095. 29. H. Okuzaki, T. Kondo, T. Kunugi, Polymer 40 (1999) 995-1000. 30. C. Cassignol, P. Oliver, A.J. Ricard, Appl. Polym. Sci. 70 (1998) 1567-1577. 31. Y. Shen, M. Wan, Synth. Met. 96 (1998) 127-132. 32. S. Lee, J.Y. Lee, H. Lee, Synth. Met. 101 (1999) 248-249. 33. R.G. Davidson, L.C. Hammond, T.G. Turner, A.R. Wilson, Synth. Met. 81 (1996) 1-4. 34. K. Cheah, M. Forsyth, V.-T. Truong, Synth. Met. 94 (1998) 215-219. 35. J. Beni’tez, Process Engineering and Design for Air Pollution Control, New York, 1993. 36. J. Stejskal, P. Kratochvil, Polymer 37 (2) (1996) 367-369. 37. J.J. Miasik, A. Hooper, B.C. Tofield, J. Chem. Soc. Faraday Trans. I 82 (1986) 11171126. 38. W.R. Slalaneck, I. Lundstrom, B. Ranby, Conjugated Polymers and Related Materials: The International of Chemical and Electronic Structure, Oxford Science, Oxford, 1993. 39. B. Soontornworajit, L. Wannatong, P. Hiamtup, S. Niamlang, D. Chotpattananont, A. Sirivat, J. Schwank, Mat. Sci. Eng. B-Solid, 136, 2007, 78–86. 40. E.M. Flaningen, E.M. Khatami, H. Szymanski, Molecular, Sieve Zeolites, Advanced Chemistry Series: American Chemical, 1971. 41. S. Bose, N.H. Kim, T. Kuila, K.T. Lau, J.H. Lee, Nanotechnology 22 (2011) 295202– 295210. 42. C. M. B. G´omez, J. M. Juarez, M. L. Martinez, A. R. Beltramone, J. Cussa and O. A. Anunziata, Mater. Res. Bull. 2013, 48, 661–667. 43. Q. Cheng, V. Pavlinek, A. Lengalova, C. Li, Y. He and P. Saha, Microporous Mesoporous Mater. 93(2006) 263–269. 44. R.E. Partch, S.G. Gangoli, E. Matijevic,W. Cai, S. Arajs, J. Colloid Interface Sci. 144 (1991) 27–34. 45. D. C. Tiwari, P. Atri, R. Sharma, Synth. Metals. 203 (2015) 228–234.
18
ACCEPTED MANUSCRIPT
RI PT
SC
•
M AN U
•
TE D
•
EP
•
Composites of polypyrrole with various cation exchanged forms of Zeolite A were successfully synthesized via chemical oxidative polymerization of Pyrrole (Py) in presence of a dispersion of A-zeolite (powder) in deionised water using anhydrous FeCl3 as an oxidant. The composites were characterized spectroscopically by Fourier Transform-Infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopic (SEM) and Energy dispersive X-ray analysis (EDXA) for their nature, morphology and elemental analysis. Gas sensing studies were carried out for the carbon monoxide gas at the concentrations ranging from 5 ppm to 1000 ppm. The effects of cation type, zeolite content and CO concentration on the response of the composites were also investigated. The sensitivity of synthesized composites was found to obey the following order: NaA/PPy > H-A/PPy > Fe-A/PPy > Cu-A/PPy > PPy depending upon the ionic radius of the cation present in the zeolite-polymer composites.
AC C
•
S1387-1811(17)30082-3
DOI:
10.1016/j.micromeso.2017.02.027
Reference:
MICMAT 8137
To appear in:
Microporous and Mesoporous Materials
Received Date: 28 October 2016 Revised Date:
21 January 2017
Accepted Date: 9 February 2017
Please cite this article as: R.A. Naikoo, S.U. Bhat, M.A. Mir, R. Tomar, Composites of various cation exchanged forms of mesoporous zeolite A with polypyrrole-thermal, spectroscopic and gas sensing studies, Microporous and Mesoporous Materials (2017), doi: 10.1016/j.micromeso.2017.02.027. 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
AC C
EP
TE D
M AN U
SC
RI PT
Graphical Abstract
ACCEPTED MANUSCRIPT
Composites of various cation exchanged forms of mesoporous zeolite A with Polypyrrole-Thermal, spectroscopic and gas sensing studies Rawoof A. Naikoo1, Sami U. Bhat1, Muzzaffar A. Mir1 & Radha Tomar1* School of studies in Chemistry, Jiwaji University, Gwalior (M.P)-474011-India *[email protected], +91-9425341452
RI PT
1
Abstract
TE D
M AN U
SC
Composites of polypyrrole with various cation exchanged forms of Zeolite A were successfully synthesized via chemical oxidative polymerization of Pyrrole (Py) in presence of a dispersion of A-zeolite (powder) in deionised water using anhydrous FeCl3 as an oxidant. The composites were characterized spectroscopically by Fourier Transform-Infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopic (SEM) and Energy dispersive X-ray analysis (EDXA) for their nature, morphology and elemental analysis. Thermo-gravimetric analysis (TGA) was carried out for the thermal stability of the composites. Gas sensing studies were carried out for the carbon monoxide gas at the concentrations ranging from 5 ppm to 1000 ppm. The effects of cation type, zeolite content and CO concentration on the response of the composites were also investigated. The sensitivity of synthesized composites was found to obey the following order: Na-A/PPy > H-A/PPy > Fe-A/PPy > Cu-A/PPy > PPy depending upon the ionic radius of the cation present in the zeolite-polymer composites and the electronegativity. The response of the Na-A/PPy composite increases from 19.36% to 40.00% as the zeolite content was increased from 10 % to 60 % (w/w %). This increase in the sensitivity by increasing the zeolite content is due to the increase in the surface area of the composite. Keywords: Zeolites; polypyrrole; composites; sensing; carbon monoxide 1. Introduction
AC C
EP
The formation of a conducting polymer within and outside an inorganic host has been considered as an important method to fabricate a new type of hybrid materials which are having both the unique properties of organic polymers and the mechanical strength and chemical properties of inorganic hosts [1]. These composites are having wide range of applications in electronic devices due to their superior electronic, magnetic, optical and electrical properties as well as in catalytic applications [2–4]. Zeolites are considered to be one of the most recommended host materials due to their well-ordered channel and pore systems that can serve as hosts for growing of conducting polymers. The anionic groups present in the zeolite frameworks are expected to function as the dopants during the polymerization [5–9]. Polyaniline [10], polypyrrole (PPy) [11], polythiophene [12] and polyacrylonitrile [13] have been reported to grow in channels and cages of different zeolites both in electrochemical and chemical polymerization. As a sensing layer, zeolites are very advantageous because of their high thermal stability and chemical resistance. Characteristic molecular sieving properties have been explored and utilized in various gas sensing applications so as to detect toxic gases and other large organic 1
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
molecules [14-24]. Fabrication of polymer matrix within and outside an inorganic host is of great significance since this enables us to combine characteristics of both the parent constituents as a consequence of their molecular level interaction. Zeolites are the most favorable host materials because of their highly ordered pore systems, channels and cages of different shapes and dimensions and having their negatively charge-balanced with exchangeable cations [25]. Besides, the intercalation of a conducting polymer into a porous zeolite, reducing its aging rate and protects the former from degradation. Conductive polypyrrole (PPy) is found to be one of the most promising conductive polymers for many applications because of its ease of synthesis, high environmental stability and high conductivity [26, 27]. Its electrical conductivity is found to be highly tunable by changing the synthesis conditions [28], the oxidation state [29], counter ions or dopants [30, 31], solvents used in the fabrication processes [32], the chemical treatments [33, 34], and the heat treatments [34]. Carbon monoxide (CO) is odorless, colorless and tasteless gas which can hinder the proper transportation of oxygen in human blood [35]. Various gas sensing materials have been developed for CO detection; they are required to have long life times, offer high selectivity and low manufacturing costs [36]. Conductive polymers were reported to have many advantages over conventional metal sensors; they are less expensive, lighter, and can be operated at lower applied temperature and voltage [37]. Recently, many conductive polymers have been reported as gas sensing materials [38]. To enhance or induce the interaction between target gases and the CPs, zeolite molecular sieves have been employed [39] due to their nanometric sized channel systems that provide size and shape selective properties. The adsorption properties of zeolite depend on the pore size, zeolite type, temperature and the type of cation residing in the pore. There are two well-known mechanisms reported for the selective adsorption of zeolites [24]. First, the molecular sieve property, whereby molecules small enough to pass through are adsorbed while larger molecules are restricted. Second is the zeolite chemical composition. Si/Al ratio is found to be the major factor controlling the hydrophilic/hydrophobic properties of materials. The incorporation of specific cations within a zeolite framework by using the cation exchange method can significantly alter the gas adsorption properties. This work is aimed at fabricating the composites between Polypyrrole and various cation exchanged forms of zeolite A and their spectroscopic, thermal and gas sensing studies. The influences of the cation type, concentration of CO, zeolite amount on the response of the composites were also studied. 2. Experimental
2.1 Synthesis of Zeolite A 0.723 g of sodium hydroxide (Aldrich) was completely dissolved in 80 ml of deionized water which was then distributed into two equal halves. To first half, 8.258 g of sodium aluminate (Riedel-de Haën) was gently mixed till clear solution was obtained and to the second half; 15.48 g of sodium metasilicate (Aldrich) was added. Both the halves were quickly mixed and a thick gel was formed. Crystallization was carried out in a polypropylene bottle at 99oC for 2
ACCEPTED MANUSCRIPT
RI PT
3 h in an oven under static conditions. The material formed i.e Na-zeolite A was washed till the filtrate attained the pH ≤ 9 and finally dried overnight at 100oC. 2.2 Conversion of zeolite A in H-form Na-form of zeolite A was converted into H-form by mixing 9.0 g of synthesized zeolite, 7.230 g of NH4NO3 and 13.80 ml of deionized water. The mixture was stirred at 80oC for 30 min. Then the material was filtered under suction and washed with deionized water. After the removal of nitrates, the resulting material, NH4-zeolite, was placed in an oven at 60oC for 24 h. The ammonium form of zeolite was converted into H-form by calcinations over 60 min at 500oC.
M AN U
SC
2.3 Conversion into various cation exchanged forms of zeolite A Na-form of zeolite A was converted into various cation exchanged forms by exchanging + Na ion present on the parent zeolite A with other metal ions like Fe2+ and Cu2+ by stirring zeolite material in their corresponding alkali metal salt solutions. A mixture containing 5 g of zeolite A and 144 ml of 0.0125 M metal nitrate {Fe(NO3)2, Cu(NO3)2} was stirred at 80oC for 24 h. The sample was dried for 10 h at 120oC and calcined at 450oC for 3 h to remove nitrate ions from the surface.
EP
TE D
2.4 Synthesis of Zeolite A/Polypyrrole Composites 1.0 g of Zeolite-A powder was taken in a conical flask containing 35 ml of deionised water and sonicated until complete dispersion was observed. 0.5 ml of pyrrole (Py) was injected to it and again sonicated for 10 min so that the monomer gets uniformly dispersed in the zeolite pores. Polymerization was started by adding an oxidant solution (FeCl3) drop by drop into the dispersion and the reaction mixture was kept under magnetic stirring for 2 h at room temperature. 25 ml of acetone was added to stop the polymerization reaction and to remove excess of FeCl3. The black precipitate formed was washed alternatively with deionized water and methanol for several times and finally dried at 50oC under vacuum for 1 h.
AC C
2.5 Fabrication of Zeolite A/ Polypyrrole sensor films Composites were first dissolved in the appropriate amount of N-Methyl pyrrolidone and sonicated for about 30 min. Thereafter, Sensor films were prepared by drop casting technique on the glass substrate having the coated electrodes of silver paste. The sensor film was finally dried at 50oC for 48 h. 2.6 Materials characterization and instrumentation Powder X-ray diffraction was recorded on Shimadzu XRD 6000 equipment operating at 40 kV and 30 mA in the 2θ range from 2o to 60o. SEM Micrograph was obtained by using the JEOL JSM 5800 instrument at 10,000 and 50,000 magnifications. Fourier transform infrared (FT-IR) spectra were recorded by PerkinElmer (Spectrum RX-IFTIR) spectrometer using KBr pellets over a range from 450 cm-1 to 4000 cm-1. TGA/DSC studies were carried out on the SDT Q600 V20.9. 3
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
2.7 Gas sensing measurement A custom made two point probe connected with data acquisition system was used for measuring the response (in terms of resistance) of the composites towards the CO gas (shown in fig. 1). The gas detection unit consists of two chambers of equal volume: a mixing chamber is connected in series with a working chamber. Temperature and pressure in both chambers were controlled and monitored. The operating temperature was fixed at 30±2 ◦C during the experiment. In the serial dilution method, CO concentration was successively reduced from 10000 ppm to 1000 ppm, 500 ppm, 100 ppm, 50 ppm, and 5 ppm. Initially both the chambers contain nitrogen till the sample shows a constant resistance value. The resistance value was recorded. Then nitrogen was evacuated from the chamber and 5 ppm of CO/N2 was injected into the mixing chamber. The concentration of CO was checked by CO detector. Then the gas was allowed to enter into the working chamber and the resistance value was recorded. After the saturation in the resistance value was obtained the gas was evacuated from the working chamber and N2 was injected into the working chamber.
Fig. 1 Systematic diagram for measuring the sensitivity of the thin film sensors
3. Results and Discussion
3.1 FTIR spectra The bands observed at 1055 cm-1, 794 cm-1 and 467 cm-1 correspond to internal vibrations of Si–O–Si and Si–O–Al bridges in zeolite. The bands observed at 1638 cm-1 and between 3200 cm-1 and 3700 cm-1 in the zeolite originate from water absorbed by zeolite [40]. Fig. 2 shows FTIR spectra of different forms of Zeolite A. The absorption bands at around 500cm-1 is attributed to Si, Al-O bond and those at 1000 cm-1 and 750 cm-1 respectively are due to 4
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
asymmetric and symmetric stretches of the zeolite network. A band for OH group was observed at 3485 cm-1. It is found that spectra of different cation exchanged forms of zeolite A are similar indicating their structure stability; however there may be variation in transmittance % due to presence of different cations [41]. Spectrum of pure PPy exhibits the characteristic absorption bands at 1513 cm-1 (C–C and C=C stretching vibrations), 1422 cm-1 (C–N stretching vibration), 1265 cm-1 (C–H or C–N in-plane vibration) and 1075 cm-1 (C–H and N–H in-plane deformation vibrations) [42, 43]. Fig. 3 represents the FTIR spectra of composites of Polypyrrole with various cation exchanged forms of zeolite-A. It is clearly seen that the characteristic peaks of PPy (3370 cm-1, 1560 cm-1and 1340 cm-1) are present indicating the presence of polypyrrole in the composite. Also the characteristic peaks of zeolite A (1000 cm-1, 740 cm-1, 471 cm-1) in the composites show presence of zeolite in the composites.
80 70
Na-A H-A Fe-A Cu-A
50 40
TE D
30 20 10 0 4000
3500
3000
2500
2000
1500
1000
500
-1
EP
Wavenumber (cm )
Fig. 2 FTIR spectra of various cation exchanged forms of zeolite A
Fig. 3 FTIR spectra of composites of PPy with various cation exchanged forms of Zeolite-A
AC C
Transm ittance (%)
60
3.2 XRD analysis
Fig. 4 shows the X-ray diffraction patterns of synthesized zeolite-A and its various cation exchanged forms. From the Fig. 4, it is seen that the degree of crystallinity is very high and all the materials are crystalline in nature without having any amorphous phase. Also, it is found that there is little change particularly in the intensity of peaks in the all the forms, indicating that there is no significant structural change in converting the Na zeolite-A into its various cation exchanged forms. All forms of the zeolite are showing the sharp peaks at 2 theta values of 25o.
5
ACCEPTED MANUSCRIPT
Zeolite Na-A
0
10
20
30
2-Theta(deg.)
40
50
Na-A/PPy H-A/PPy Fe-A/PPy Cu-A/PPy
10
20
30
40
50
60
2-Theta (deg.)
Fig. 5 XRD spectra of composites of PPy with various cation exchanged forms of Zeolite A
TE D
Fig. 4 XRD spectra of various cation exchanged forms of Zeolite A
3.3 SEM analysis
RI PT
2000 1500 1000 500 0
Zeolite H-A
320 300 280 260 240 220 200 180 160 140 120 100 80
SC
Intensity
1600 1200 800 400 0
Zeolite Fe-A
Intensity
Intensity
1600 1200 800 400 0
Zeolite Cu-A
M AN U
Intensity
2000 1500 1000 500 0
Intensity
The XRD spectra of Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy composites are shown in Fig. 5. In each case, a broad peak at about 2θ =26o was observed. The broad peaks are characteristic of amorphous PPy [44]. However, the intensity of peaks in these composites was found different which may be attributed to the presence of different cations.
AC C
EP
The synthesized materials Na-A, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy were characterized for morphologies by FEG-SEM analysis at 10,000 and 50,000 magnifications as shown in Fig. 6 (a-e). From SEM images, zeolite-A particles appear to have a cuboid shape with excellent crystal edges and have particle size in 2–5 µm range as shown in the Fig. 6a. FEG-SEM image of PPy have cauliflower like morphology and its grain size varies from ~130 nm to ~200 nm [45]. Fig. 6 b-e shows the presence of cuboids and cauliflower type structures indicating the formation of zeolite/polypyrrole composites.
6
ACCEPTED MANUSCRIPT
(b)
SC
RI PT
(a)
(d)
(e)
AC C
EP
TE D
M AN U
(c)
Fig. 6 SEM micrographs of a) Zeolite Na-A b) Na-A/PPy c) H-A/ PPy d) Fe-A/PPy and e) Cu-A/PPy
7
ACCEPTED MANUSCRIPT
3.4 EDS analysis
M AN U
TE D
(a)
SC
RI PT
Elemental analysis for Si, O, Al, C, N, Cl, Na, Fe and Cu in the Na-A/PPy, H-A/PPy, FeA/PPy and Cu-A/PPy composites were carried out using energy dispersive X-ray microanalysis (Fig. 7 a-d). In the EDXA spectra, all the composites were found to contain the elements like Si, O, Al, C, N and Cl indicating the successful synthesis of zeolite/Polypyrrole composites since Si, O, Al and Cl are the constituent elements of zeolite A and C & N of Polypyrrole. The presence of Na in Na-A/PPy, Fe in Fe-A/PPy and Cu in Cu-A/PPy composites validate the successful conversion of Na-A into various cation exchanged forms. No iron was found in the Na-A/PPy, H-A/PPy and Cu-A/PPy composites due to the repeated washing after the synthesis of the composite. Chlorine, however retained in the structure of the composites due to its role as the doping anion (chloride) in the synthesis of polypyrrole.
(d)
AC C
EP
(c)
(b)
Fig. 7 EDX spectra of a) Na-A/PPy b) H-A/PPy c) Fe-A/PPy and d) Cu-A/PPy
8
ACCEPTED MANUSCRIPT
SC
RI PT
3.5 Thermal analysis The thermal stability of the zeolite A/PPy composites was studied by TGA. Fig. 8 a-d presents the curves of weight loss versus temperature of Zeolite A/PPy composites. A weight loss of 27.50% for Na-A/PPy, 30.02% for H-A/PPy, 31.18% for Fe-A/PPy and 26.45 % for CuA/PPy which is attributed to expulsion of water has been observed upto the temperature of 200oC. Further, the degradation process of PPy matrix in the composites was initiated at 200oC and continued until 700oC where the weight loss reached up to 55.11% for Na-A/PPy, 52.22% H-A/PPy, 54.69% Fe-A/PPy and 56.78% Cu-A/PPy. From the thermal studies of the composites shown in table 1, it can be concluded that the thermal stability of the composites follow the order as: H-A/PPy> Na-A/PPy > Fe-A/PPy >Cu-A/PPy.
(b)
TE D
M AN U
(a)
(d)
AC C
EP
(c)
Fig. 8 TGA thermograms of a) Na-A/PPy b) H-A/PPy c) Fe-A/PPy and d) Cu-A/PPy
9
ACCEPTED MANUSCRIPT
Table 1 Weight loss % of zeolite A/PPy composites at different temperatures Weight loss % upto 200oC
Weight loss % upto 700oC
Weight loss % upto 1000oC
Na-A/PPy
27.50
55.11
66.83
H-A/PPy
30.02
52.22
Fe-A/PPy
31.18
54.69
Cu-A/PPy
26.45
56.78
RI PT
Materials
59.01
66.96
SC
69.02
3.6 Response to CO gas
M AN U
For the sensing of CO, the samples are mounted on the suitable sample holder and the electrical connections are made by silver paste. The change in value of resistance is measured at different concentrations of CO. The sensitivity (S) of sensors is calculated by using the following equation
S% =
100
AC C
EP
TE D
Where S % is the Sensitivity of the sample for the gas, Rg is the saturation value of resistance in presence of gas and Ro is the resistance in presence of nitrogen. The CO gas sensing of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy thin film sensors are measured under nearly same practical conditions i.e. atmospheric pressure, room temperature and N2 as a reference gas environment. Sensing films are firstly exposed to clean dry air for 10 min. to record the base value of the sensor resistance. The nitrogen gas is used for the recovery of the sensors. From Fig. 9, it is observed that the Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy thin film sensors are having higher sensitivity to CO as compared to the PPy thin film sensor. Since zeolite is having a porous structure, the gas molecules are provided with large surface area to get adsorbed and interact with the polymer chains. Hence, adding zeolite to the polymer provides adsorption sites for the gas molecules to interact with the polymer chains and therefore response increases. From Fig. 9 and Table 2, it is found that the response time of PPy, Na-A/PPy, HA/PPy, Fe-A/PPy and Cu-A/PPy, at 5 ppm were 245, 180, 204, 239, and 262 sec. respectively. The reason is that by addition of zeolite, surface area of the sensor increases and more CO molecules get adsorbed. The slightly higher value of response times for Fe-X/PPy and Cu-X/PPy may be attributed to the interaction of CO molecules with the Fe and Cu ions and thus less number of CO are available for interaction with polymer chains. The reversibility of these sensors was checked by flushing of N2 and it was found that after flushing, the sensors retained their original value of resistance. The recovery time of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy was found to be 235, 121, 163, 211 and 222 sec. respectively. The higher values of 10
ACCEPTED MANUSCRIPT
80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0 -5
PPy Cu-A/PPy Fe-A/PPy H-A/PPy Na-A/PPy
RI PT
1000 PPM
500 PPM
100 PPM
SC
50 PPM 5 PPM
-200
0
200
M AN U
Sensitivity ( % )
recovery times for Fe-A/PPy, and Cu-A/PPy were attributed to the stronger interaction of CO molecules with Fe and Cu ions.
400
600
800 1000 1200 1400 1600 1800
Time (sec.)
Fig. 9 The CO sensitivity of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy composites at 5 ppm to 1000 ppm
CO concentr ation (ppm)
PPy
TE D
Table 2 Sensitivity (S%), response time and recovery time of PPy, PPy, Na-A/PPy, HA/PPy, Fe-A/PPy and Cu-A/PPy composites at various ppm concentration of CO gas Na-A/PPy
Respo nse Time (sec.)
Max. S %
Max. S%
Respo nse Time (sec.)
5
6.36
245
16.52
50
11.83
221
100
14.94
500 1000
180
13.29
26.44
144
202
39.66
20.41
187
26.62
163
235
Respo nse Time (sec.)
Reco very Time (sec.)
Fe-A/PPy Max. S%
Respo nse Time (sec.)
204
9.09
20.88
180
138
28.48
56.02
119
74.38
104
AC C
Reco very Time (sec.)
EP
Max. S%
H-A/PPy
121
Reco very Time (sec.)
Cu-A/PPy Max. S%
Resp onse Tim e (sec. )
239
8.58
262
15.34
223
14.07
235
161
24.43
202
18.80
226
37.97
144
33.52
181
26.42
207
51.26
125
40.90
164
31.62
181
163
Reco very Time (sec.)
211
11
Reco very Time (sec.)
222
ACCEPTED MANUSCRIPT
SC
RI PT
Fig. 10 shows the Sensitivity values of polypyrrole and the composites in presence of CO from 5 ppm and 1000 ppm. When PPy is exposed to CO concentration of 5 ppm, it shows a sensitivity value of 6.36 %. The sensitivity of PPy towards CO increases from 6.36 to 26.62 % as the CO concentration is increased from 5 ppm to 1000 ppm. When the concentration is increased, more and more CO molecules come in contact with the polymer chains and the sensitivity value increases. From Fig. 10 and Table 2, it can be seen that the sensitivity of PPy towards CO increases when zeolite is added to it. This is because zeolite is having a porous structure, the gas molecules are provided with high surface area to get adsorbed and interact with the polymer chains. Hence, adding zeolite to the polymer provides adsorption sites for the gas molecules to interact with the polymer chains and therefore sensitivity value increases.
PPy Cu-A/PPy Fe-A/PPy H-A/PPy Na-A/PPy
60 50 40 30 20 10 0
TE D
Sensitivity (%)
70
M AN U
80
0
200
400
600
800
1000
1200
Concentration (PPM)
EP
Fig. 10 Sensitivity (%) vs concentration graph of PPy and Zeolite A/PPy Composites. The BET surface area, Langmuir surface area and total pore volume values of the
AC C
synthesized materials are shown in the table 3. As shown in the table, PPy showed least surface area (35.9065 m²/g) and pore volume (0.054552 cm³/g) as compared to the composites. Among the composites, Na-A/PPy is having higher surface area value (58.8334 m²/g) and pore volume (0.098007 cm³/g) and Cu-A/PPy shows the least surface area value (39.9215 m²/g) and pore volume (0.071218 cm³/g).The higher sensitivity value of the Na-A/PPy composite is confirmed from the BET analysis, since Adsorption of gases is a surface phenomenon. For BET surface area, adsorption desorption isotherms are shown in figure 11.
12
ACCEPTED MANUSCRIPT
Table 3 Surface area and pore volume analysis of PPy and Zeolite-A/PPy composites
BET
Langmuir
H-A/PPy
53.3294 m²/g
81.2715 m²/g
Na-A/PPy
58.8334 m²/g
84.5036 m²/g
PPy
35.9065 m²/g
51.4095 m²/g
Fe-A/PPy
47.9799 m²/g
68.8796 m²/g
Cu-A/PPy
39.9215 m²/g
57.5399 m²/g
Sample Name
0.094963 cm³/g
0.098007 cm³/g 0.054552 cm³/g 0.088383 cm³/g 0.071218 cm³/g
M AN U
H-A/PPy Na-A/PPy PPy Fe-A/PPy Cu-A/PPy
60 50 40 30 20
TE D
Quantity adsorbed (cm3/g STP)
70
Pore volume (cm3/g)
RI PT
Surface Area (m2/g)
SC
Surface area (m2/g)
10
0
0.0
0.2
0.4
0.6
0.8
1.0
EP
Relative Pressure (P/PO)
AC C
Fig. 11 Adsorption-desorption isotherms of PPy and Zeolite A/PPy composites.
3.7 Effect of cation type on the sensitivity of Zeolite A/PPy composites Fig. 12 shows the effect of cation type on the sensitivity of zeolite A/PPy composites towards CO at 100 ppm. For this purpose four types of cations were selected: 1) Na+ 2) Fe2+ 3) Cu2+ 4) H+. In all these composites, the zeolite content was kept at a constant value of 50%. From the Fig. 12, it is clearly evident that the sensitivity of Na+-A/ PPy, H+-A /PPy, Fe2+-A/PPy, Cu2+-A/PPy and PPy at 100 ppm of CO concentration is 39.66%, 28.43%, 24.43% , 18.8% and 11.83% respectively.
13
ACCEPTED MANUSCRIPT
M AN U
SC
RI PT
The sensitivity value of these synthesized composites depends up on two factors- i) ionic radius of the cation present in the zeolite/polymer composites and ii) Electronegativity. It is clearly evident that Na+-A/PPy shows larger sensitivity to CO than other cationic forms and PPy. The reason of having the largest sensitivity of Na+-A/PPy is because of its smallest electronegativity and large ionic radius. The sensitivity obeys the following order: Na+-A/PPy > H+-A/PPy > Fe2+-A/PPy > Cu2+-A/PPy > PPy. It is found that the electronegativity of Na+, Fe2+, Cu2+, H+ is 0.93, 1.83, 1.9, 2.1 with corresponding ionic radii 186 pm, 124 pm, 128 pm, 78 pm respectively. In case of Na+-form because of its small electronegativity and large ionic radius, the gas molecules do not interact with the ion present in the zeolite instead interact with the polymer chain and hence result in large sensitivity. However for Cu2+-A/PPy, there is strong interaction of the gas molecules with the Cu ion present in the composite than with the polymer chain resulting in less sensitivity. It is clearly evident that the sensitivity of PPy towards CO increased as zeolite is added to it. This is because zeolites are having three-dimensional (3D) frameworks with an open porosity that gives rise to an exceptionally high surface area. Thus on adding zeolite to PPy, the surface area increases and more CO molecules get adsorbed to get interacted with the polymer chains
40
Sensitivity vs cation type at 100 ppm
25 20 15 10
AC C
5
TE D
30
EP
Sensitivity(%)
35
Na
H
Fe
Cu
PPy
Cation Type
Fig. 12 Sensitivity of PPy and zeolite A/PPy composites of various cation types when exposed to 100 ppm of CO concentration
14
ACCEPTED MANUSCRIPT
3.8 Effect of zeolite content on the sensitivity of Zeolite A/PPy composites
SC
RI PT
The sensitivity of Na-A/PPy towards CO at 100 ppm concentration at various zeolite contents is shown in Fig. 13. The sensitivity of the Na-A/PPy composite increases from 19.36% to 40.00% as the zeolite content was increased from 10 % to 60 % (w/w %). This increase in the sensitivity by increasing the zeolite content is due to the increase in the surface area of the composite. Due to which large no. of active sites become available for gas molecules to be adsorbed so that they can penetrate deep inside the composite and interact with the PPy chains. Beyond 60 % of zeolite content there is no further increase in the sensitivity of the Na-A/PPy composite and attains almost a steady state. This steady state sensitivity beyond 60 % of zeolite content is because all the CO molecules present get their active sites and further increasing the active sites are of no mean. 45 Na-A/PPy at 100 ppm of CO
M AN U
Sensitivity (%)
40 35 30 25 20 15
10
20
30
TE D
0
40
50
60
70
80
Zeolite content (% w/w)
EP
Fig. 13 Sensitivity of Na-A/PPy at 100ppm of CO vs zeolite content
3.9 Polypyrrole/Zeolite A sensitivity to CO: Effect of the subsequent runs
AC C
The Sensitivity of Na-A/PPy at 500 ppm of CO was found to be 55.37%, 53.64%, 49.36% and 43.66 % during 1st, 2nd, 3rd and 4th cyclic intervals respectively. It has been found that there is little loss in the sensitivity after repeating the cyclic interval upto 3 times. However, after 3 runs there is significant loss in the sensitivity value. The reason is that during the successive runs, some gas molecules may get adsorbed permanently and thus cause reduction in the sensitivity of the composite. Hence, the sensitivity of the composite goes on decreasing with the cyclic interval as shown in Fig. 14.
15
ACCEPTED MANUSCRIPT
Na-A/PPY at 500 ppm of CO
50 45 40 35 0
1
2
3
Cyclic interval
4
RI PT
Sensitivity (%)
55
5
SC
Fig. 14 Sensitivity of Na-A/PPy towards CO at 500 ppm for various intervals
M AN U
4. Conclusion
AC C
EP
TE D
Composites of polypyrrole with various cation exchanged forms of Zeolite A were successfully synthesized via chemical oxidative polymerization of Pyrrole (Py) in presence of a dispersion of A-zeolite (powder) in deionised water using anhydrous FeCl3 as an oxidant. The composites were characterized by FTIR, Powder XRD, SEM, EDXA and TGA. Formation of Polypyrrole (PPy) and its subsequent incorporation in the zeolite A/PPy composites was confirmed by Fourier Transform-Infrared (FTIR) spectral studies and X-ray diffraction (XRD) pattern analysis. Scanning electron microscopic (SEM) analysis revealed the external morphology of the zeolite A (average diameter of 2-5µm) and various composites (average size of about ~130 nm to ~200 nm). Energy dispersive X-ray analysis (EDXA) confirmed the presence of various constituents viz. metal ions, silicon, Aluminium, Oxygen, Nitrogen and Carbon in the composites. The presence of Na in Na-A/PPy, Fe in Fe-A/PPy and Cu in CuA/PPy was confirmed by EDX analysis. The effects of cation type, zeolite content, CO concentration on the sensitivity of the composites towards the CO were studied. The response time of PPy, Na-A/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy, at 5 ppm were 245, 180, 204, 239, and 262 sec respectively. The reason is that by addition of zeolite, surface area of the sensor increases and more CO molecules get adsorbed. The recovery time of PPy, NaA/PPy, H-A/PPy, Fe-A/PPy and Cu-A/PPy was found to be 235, 121, 163, 211 and 222 sec. respectively. The higher values of recovery times for Fe-X/PPy, and Cu-X/PPy were attributed to the stronger interaction of CO molecules with Fe and Cu ions. The sensitivity of the Na-A/PPy composite increases from 19.36% to 40.00% as the zeolite content was increased from 10 % to 60 % (w/w %). This increase in the sensitivity by increasing the zeolite content is due to the increase in the surface area of the composite. The sensitivity of synthesized composites was found to obey the following order: Na-A/PPy > H-A/PPy > Fe-A/PPy > Cu-A/PPy > PPy depending upon the ionic radius of the cation present in the zeolite-polymer composites and the electronegativity. 16
ACCEPTED MANUSCRIPT
Acknowledgements
RI PT
The authors are highly thankful to IIT Kanpur and Jamia Millia Islamia University for carrying out characterization of the synthesized materials. The authors are also thankful to School of studies in Chemistry, Jiwaji University, Gwalior and DRDE, Gwalior for providing the necessary facilities to carry out the experimental work. References
AC C
EP
TE D
M AN U
SC
1. R. Gangopadhyay and A. De, Chem. Mater., 2000, 12, 608– 621. 2. T. G. Jiu, H. B. Liu, H. Y. Gan, Y. L. Li, S. Q. Xiao, H. M. Li, Y. Liu, F. S. Lu, L. Jiang and D. B. Zhu, Synth. Met., 2005, 148, 313–319. 3. H. Rein, K. Ruckpaul and W. Haberditzl, Chem. Phys. Lett., 1973, 20, 71–76. 4. A. P. Alivisators, Science, 1996, 271, 933–937. 5. O. Kresnawahjuesa, G. H. K¨uhl, R. J. Gorte and C. A. Quierini, J. Catal., 2002, 210, 106–115. 6. L. B. McCusker and C. Baerlocher, in Introduction to Zeolite Science and Practice, ed. J. Cejka, H. Van Bekkum, A. Corma and F. Sch¨uth, Elsevier B.V., Amsterdam, 2007. 7. T. Bein and P. Enzel, Angew. Chem., Int. Ed. Engl., 1989, 28(12), 1692–1694. 8. Y. Kitayama, H. Katoh, T. Kodama and J. Abe, Appl. Surf. Sci., 1997, 121/122, 331– 334. 9. G. Larsen, G. L. Haller and M. Marquez, J. Phys. Chem., 1992, 96, 4145–4148. 10. P. Enzel and T. Bein, J. Phys. Chem., 1989, 93, 6270–6272. 11. M. Nakayama, J. Yano, K. K. Nakaoka and K. Ogura, Synth. Met., 2002, 128, 57–62. 12. P. Enzel and T. Bein, Synth. Met., 1993, 55–57, 1238–1245. 13. P. Enzel, J. J. Zoller and T. Bein, J. Chem. Soc., Chem. Commun., 1992, 8, 633–635. 14. R. Gangopadhyay, A. De, Sens. Actuators B 77 (2001) 326–329. 15. S. Jain, S. Chakane, A.B. Sumui, V.N. Krishnamurthy, S.V. Bhoraskar, Sens. Actuators B 96 (2003) 124–129. 16. K.H. Hong, K.W. Oh, T.J. Kang, J. Appl. Polym. Sci. 92 (2004) 37–42. 17. K. Fukui, S. Nishida, Sens. Actuators B 45 (1997) 101–106. 18. G. Li, S. Kawi, Sens. Actuators B 59 (1999) 1–8. 19. O. Hugon, M. Sauvan, P. Benech, C. Pijolat, F. Lefebvre, Sens. Actuators B 67 (2000) 235–243. 20. I. Sasaki, H. Tsuchiya, M. Nishioka, Sens. Actuators B 85 (2002) 26–33. 21. M. Vilaseca, J. Coronas, A. Cirera, A. Cornet, J.R. Morante, J. Santamaria, Catal. Today 82 (2003) 179–185. 22. J. Zhou, P. Li, S. Zhang, Y. Long, F. Zhou, Y. Huang, P. Yang, M. Bao, Sens. Actuators B 94 (2003) 337–342. 23. H. Huang, J. Zhou, S. Chen, J. Zeng, Y. Huang, Sens. Actuators B 101 (2004) 316–321.
17
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
RI PT
24. M. Vilaseca, C. Yague, J. Coronas, J. Santamaria, Sens. Actuat. B-Chem. 117, 2006, 143150. 25. M. Nakyama, J. Yano, K. Nakaoka, K. Ogura Synth Met. 138, 2003, 419-22. 26. M. Salmon, K.K. Kanazawa, A.F. Diaz, M. Krounbi, J. Polym. Sci., Polym. Lett. Ed. 20 (1982) 187. 27. S.A. Chen, C.S. Liao, Macromolecules 26 (1993) 2810-2816. 28. K.C. Khulbe, R.S. Mann, J. Polym. Sci. 20 (1982) 1089-1095. 29. H. Okuzaki, T. Kondo, T. Kunugi, Polymer 40 (1999) 995-1000. 30. C. Cassignol, P. Oliver, A.J. Ricard, Appl. Polym. Sci. 70 (1998) 1567-1577. 31. Y. Shen, M. Wan, Synth. Met. 96 (1998) 127-132. 32. S. Lee, J.Y. Lee, H. Lee, Synth. Met. 101 (1999) 248-249. 33. R.G. Davidson, L.C. Hammond, T.G. Turner, A.R. Wilson, Synth. Met. 81 (1996) 1-4. 34. K. Cheah, M. Forsyth, V.-T. Truong, Synth. Met. 94 (1998) 215-219. 35. J. Beni’tez, Process Engineering and Design for Air Pollution Control, New York, 1993. 36. J. Stejskal, P. Kratochvil, Polymer 37 (2) (1996) 367-369. 37. J.J. Miasik, A. Hooper, B.C. Tofield, J. Chem. Soc. Faraday Trans. I 82 (1986) 11171126. 38. W.R. Slalaneck, I. Lundstrom, B. Ranby, Conjugated Polymers and Related Materials: The International of Chemical and Electronic Structure, Oxford Science, Oxford, 1993. 39. B. Soontornworajit, L. Wannatong, P. Hiamtup, S. Niamlang, D. Chotpattananont, A. Sirivat, J. Schwank, Mat. Sci. Eng. B-Solid, 136, 2007, 78–86. 40. E.M. Flaningen, E.M. Khatami, H. Szymanski, Molecular, Sieve Zeolites, Advanced Chemistry Series: American Chemical, 1971. 41. S. Bose, N.H. Kim, T. Kuila, K.T. Lau, J.H. Lee, Nanotechnology 22 (2011) 295202– 295210. 42. C. M. B. G´omez, J. M. Juarez, M. L. Martinez, A. R. Beltramone, J. Cussa and O. A. Anunziata, Mater. Res. Bull. 2013, 48, 661–667. 43. Q. Cheng, V. Pavlinek, A. Lengalova, C. Li, Y. He and P. Saha, Microporous Mesoporous Mater. 93(2006) 263–269. 44. R.E. Partch, S.G. Gangoli, E. Matijevic,W. Cai, S. Arajs, J. Colloid Interface Sci. 144 (1991) 27–34. 45. D. C. Tiwari, P. Atri, R. Sharma, Synth. Metals. 203 (2015) 228–234.
18
ACCEPTED MANUSCRIPT
RI PT
SC
•
M AN U
•
TE D
•
EP
•
Composites of polypyrrole with various cation exchanged forms of Zeolite A were successfully synthesized via chemical oxidative polymerization of Pyrrole (Py) in presence of a dispersion of A-zeolite (powder) in deionised water using anhydrous FeCl3 as an oxidant. The composites were characterized spectroscopically by Fourier Transform-Infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopic (SEM) and Energy dispersive X-ray analysis (EDXA) for their nature, morphology and elemental analysis. Gas sensing studies were carried out for the carbon monoxide gas at the concentrations ranging from 5 ppm to 1000 ppm. The effects of cation type, zeolite content and CO concentration on the response of the composites were also investigated. The sensitivity of synthesized composites was found to obey the following order: NaA/PPy > H-A/PPy > Fe-A/PPy > Cu-A/PPy > PPy depending upon the ionic radius of the cation present in the zeolite-polymer composites.
AC C
•