Development of water-based polyaniline sensor for hydrazine detection

Abstract

In this study, water-soluble polyaniline-methylcellulose complex (PAni-MC) was applied as an environmental friendly chemical sensor for hydrazine detection. PAni was rendered water-soluble through chemical modification with MC. Fourier transform infrared (FTIR) and Ultraviolet-visible (UV–vis) spectroscopies confirmed the chemical structures of PAni-MC to be the conducting emeraldine salt form with electrical conductivity values of 0.068 S cm−1 for pristine PAni and 0.132 S cm−1 for PAni-MC respectively. In the hydrazine detection procedure, PAni-MC solution was added into samples containing various concentrations of hydrazine (10−100 ppm) and the sensor responses were recorded using a conductivity meter. Several parameters have been studied, including (i) different volume ratio of PAni to hydrazine, (ii) different mass ratio of aniline (Ani) monomer to MC, and (iii) detection at low concentration range of hydrazine (1−10 ppm). From the results obtained, PAni-MC (volume ratio 2:5 of PAni-MC: hydrazine) with the mass ratio 0.2:1 of Ani: MC has achieved the best sensitivity of 0.0143 ppm−1, hence it was selected to further study its sensor performance. Calibration has shown a good sensitivity of 0.0132 ppm-1 and a good linear correlation (R2 = 0.9953), the limit of detection (LOD) of 0.55 ppm, and the limit of quantitation (LOQ) of 1.82 ppm respectively. The sensor performance was supported by UV–vis and FTIR analyses. Significant decrease in the UV–vis absorbance was observed at bipolaron (∼821 nm) and polaron (∼450 nm) bands, meanwhile the intensity of quinoid/benzenoid (IQ/IB) ratio in the FTIR spectra has shown a decrease from 1.03 to 0.97. In real sample analysis, PAni-MC eventually indicated the best recovery range of 96–136 % and a good relative standard deviation (RSD) of 2.69–5.84 %.