Polyaniline as a Gas-Sensor Material

ABSTRACT

Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized by UV-visible, FTIR, and XRD analyses. The electrical conductivity of the PANI film was studied by a four-point probe method at room temperature. Finally, ammonia gas-sensing characteristics of the prepared polyaniline film were studied by measuring the change in electrical conductivity on exposure to ammonia gas at different concentrations. The influence of concentration of acid during polymerization of aniline and dopant concentration on the gas sensing characteristics of PANI film are reported in this paper.

Keywords:

• Benzenoid ring
• Bipolarons
• Chemisorption
• Conductivity
• Conjugated polymers
• Crystallinity
• Electrical properties
• Film casting
• Four-probe method
• Gas-sensor
• Measuring cell
• Ohmic contact
• Polarons
• Polyaniline
• Probe spacing
• Quinone diimine unit
• Recovery time
• Response time
• Solution casting

ACKNOWLEDGMENT

We gratefully acknowledge the University Grants Commission, Government of India for providing fellowship to one of the authors, Partha Pratim Sengupta.