Study of the primary sensitivity of polypyrrole/r-Fe2O3 to toxic gases

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Abstract

Polypyrrole (PPy) was prepared by chemical oxidation using methoxy ethanol as solvent and Fe(NO3)3·9H2O as oxidant. PPy/r-Fe2O3 was prepared by simultaneously gelling and polymerization, using the same solvent and oxidant. The materials were characterized by FTIR, XRD, TG-DTA, SEM, and HRTEM, and studied for the gas sensitivity. From the TG-DTA curve of PPy/r-Fe2O3, we found that the degradation temperature of PPy was about 210 °C, so the annealing temperatures of PPy/r-Fe2O3 were selected at 110 °C, 150 °C, 180 °C, and 200 °C. The influence of the mole ratio of Fe(NO3)3·9H2O to py = 1:1, 2:1, 3:1, 4:1, and 5:1 on the gas sensitivities of PPy was investigated. It was found that PPy had the maximum sensitivity to NH3 and H2S at the mole ratio of Fe(NO3)3·9H2O:py = 3:1 at room temperature, and the sensitivities were 48.5 and 31.4, respectively. PPy/r-Fe2O3 materials had no gas sensitivity at room temperature. When the working temperature increased to 90 °C, PPy/r-Fe2O3 materials appeared gas sensitivity, PPy/r-Fe2O3 annealed at 150 °C had the maximum sensitivity to NH3 and H2S, and the sensitivities were 68 and 406.8, respectively, but PPy lost gas sensitivity at this temperature. The results suggested that PPy/r-Fe2O3 had higher sensitivity and more heat stability than PPy, and the working temperature was lower than the reported working temperature of r-Fe2O3 about 350 °C, it had better properties than both pure PPy and r-Fe2O3.

Introduction

In order to prevent human from being harmed by toxic gas and to protect the environment, the detection of toxic gas has become increasingly important. The sensing materials, which are inorganic or organic, have been studied widely [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]. But both of them have particular advantage and drawbacks. Though inorganic semiconductors, such as SnO2, Fe2O3, and ZnO, either undoped or doped have been studied extensively [1], [2], [3], [4], [5], [6] and have emerged as economical sensors for monitoring toxic gases, the disadvantages of semiconductor oxide sensors are their high operating temperature (350–450 °C) [15], [16], which increases power consumption, reduces sensor life, and limits the portability. Several organic semiconductors, such as polypyrrole, polyaniline, polythiophere, polyacetylene, etc. also have gas sensitivity at normal temperature [7], [8], [9], [10], [11], [12], [13], [14]. Polypyrrole is the most studied among these, but the self-limitations reduce the application largely. Because PPy is sensitivity to electrochemical and chemical degradation and the conductivity exhibits a long-term irreversible decay due to the irreversible attack of oxygen present in the ambient, and the long response time due to the highly ordered structure [17].

To prepare the optimized properties materials, organic–inorganic sensing hybrids have been developed [18], [19], considering which can complement the characteristics of pure inorganic and organic materials. The relating studies for gas sensors are few. Benjamin et al. [20] reported the polypyrrole/SnO2 had sensitivity to organic vapors at room temperature. Suri et al. [21] studied the pressure and humidity sensitivity of polypyrrole/iron oxide. These types of hybrid materials have been shown to possess small grain size and high stability in air [22], [23]. Nardis et al. [24] reported that cobalt porphyrin/tin dioxide had superior selectivity to methanol vapor than to CO.

In this paper, we prepared polypyrrole (PPy) by chemical oxidation and PPy/r-Fe2O3 by simultaneously gelling and polymerization. Methoxy ethanol was used as solvent and Fe(NO3)3·9H2O as oxidant in the two reactions. The samples were characterized by FTIR, XRD, TG-DTA, SEM, and HRTEM, and the gas sensitivity of them was then studied. To the best of our knowledge it is the first time to study the gas sensitivity of PPy/r-Fe2O3 to toxic gases, and for comparison the gas sensitivity of PPy was also studied at the same condition.

Section snippets

Experiment

Pyrrole (py) monomer was distilled under reduced pressure, put in a desiccator, and stored in the refrigerator to use.

PPy was prepared by chemical oxidation in nitrogen atmosphere. Methoxy ethanol was added to a specific amount of Fe(NO3)3·9H2O contained in a 100-ml round bottom flask containing a magnetic stir bar, and then few drops of distilled pyrrole were added to the stirred solution (the mole ratio of Fe(NO3)3·9H2O:pyrrole monomer = 1:1, 2:1, 3:1, 4:1, and 5:1, respectively). After a

The characterizations of materials

The FTIR transmission spectra of PPy and PPy/r-Fe2O3 using KBr pellets were recorded (Fig. 1). In the spectra of PPy, the specific absorption bands are observed at 1560 cm−1, 1398 cm−1, 1298 cm−1, 1211 cm−1, 1047 cm−1, 930 cm−1, and 790 cm−1. They are close to those reported data [25], [26]: stretching vibration (1560 cm−1) of Cdouble bondC bond, stretching vibration (1298 cm−1) of Csingle bondC bond, stretching vibration (1211 cm−1) of Csingle bondN bond, and bond (1398 cm−1) of pyrrole ring. In the PPy/r-Fe2O3 spectra, peaks of PPy are

Conclusion

In order to develop the new gas sensors, we put emphasis on organic–inorganic materials, and firstly studied the gas sensitivity of PPy/r-Fe2O3 to NH3 and H2S. The materials were characterized by FTIR, XRD, TG-DTA, SEM, and HRTEM. The r-Fe2O3 particle in PPy/r-Fe2O3 was spherical as it can be seen from SEM and HRTEM. The results of gas sensitivity test suggested that PPy had the maximum sensitivity to NH3 and H2S at the mole ratio Fe(NO3)3·9H2O:py = 3:1 at room temperature, but the sensitivity

References (29)

  • C. Baratto et al.

    Sens. Actuators B

    (2004)
  • J.-P. Ahn et al.

    Sens. Actuators B

    (2004)
  • Y.D. Wang et al.

    Solid State Electron.

    (2004)
  • O.K. Tan et al.

    Sens. Autuators B

    (2003)
  • X.F. Zhang

    Songliao J. (Nat. Sci. Ed.)

    (2002)
  • C. Jouve et al.

    Sens. Autuators B

    (1995)
  • J. Chen et al.

    Radiat. Phys. Chem.

    (2003)
  • N.E. Agbor et al.

    Sens. Actuators B

    (1995)
  • H.-K. Jun et al.

    Sens. Actuators B

    (2003)
  • G. Sberveglieri et al.

    Sens. Actuators B

    (1995)
  • E. Bescher et al.

    Mater. Sci. Eng. C

    (1998)
  • K. Suri et al.

    Sens. Actuators B

    (2002)
  • R. Partch et al.

    J. Colloid Interface Sci.

    (1991)
  • S. Nardis et al.

    Sens. Actuators B

    (2004)
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