Biopolymer-Polyaniline Composite for a Wide Range Ammonia Gas Sensor

This paper reports the wide range ammonia sensing behavior of biopolymer polyaniline composite. The agarose–guar gum-polyaniline (A–G-PANI) composite films were prepared by the
${\textit {in situ}}$
synthesis of polyaniline in the biopolymeric matrix. The polyaniline biocomposite exhibits an interpenetrated network structure as confirmed by field emission scanning electron microscopy. The synthesized polyaniline biopolymer composite shows an excellent ammonia sensing behavior over a wide range of 10–90 000 ppm (9%). The sensor shows high performance in terms of sensitivity factor (
$R_{\mathrm {gas}}/R_{\mathrm {air}})$
ranging from 1.07 to 34.95 in the entire concentration range. The response time and recovery time of the sensor varies from 2 to 5 min and 5 to 25 min, respectively, with respect to the increase in the concentration of gas. The sensor shows selective response against H
₂
S, ethanol, methanol, and acetone. The enhanced performance of the sensor is attributed to the presence of large number of sites provided by the interpenetrated network structure of polyaniline biocomposite. The electrical circuit model for A–G-PANI is constructed using the electrical impedance spectroscopy, and a probable mechanism is proposed for detection over a wide range.