Effect of dopant concentration on polyaniline for hydrazine detection

Abstract

In this study, a simple and cost-effective sensor was developed for hydrazine detection using polyaniline (PANI) thin film, replacing traditional expensive and complicated sensor setups. PANI was synthesized via chemical oxidation by using different ratio of sodium dioctyl sulfosuccinate (AOT) dopant. Simple techniques, such as Fourier transform infrared (FTIR), ultraviolet–visible (UV–vis) spectroscopy, X-ray diffraction (XRD), energy-dispersive X-ray microscopy (EDX) and four-point probe were utilized to study the chemical structure of the resulted PANI and to understand the interaction between PANI and the analyte. Field emission scanning electron microscopy (FESEM) was used to study the morphology of PANI sample. The effect of dopant concentration on the performance of PANI sensor for hydrazine detection was investigated. The results showed a significant decrease in the absorption of polaron peak in UV–vis at ~780nm. PANI with the highest ratio (Ani:AOT=5:7) of dopant in this study, worked as a highly sensitive sensor and gave fast response time within 0.12min (7s), compared to the PANI with lesser content (5:3 and 5:5) of dopants. The sensor responses were also evaluated based on the conductivity study, where PANI in the conducting state possessed conductivity in the range of 0.4–0.8S/cm and it decreased upon immersion in various concentrations of hydrazine due to the dedoping process by hydrazine. FTIR analysis is useful to analyze the intensity ratio of quinoid/benzenoid in order to understand the structural changes occurring during hydrazine detection. However, all PANI, regardless on the difference of Ani/AOT ratio, showed good reusability up to 10 cycles. As a conclusion, PANI3 with the highest ratio of AOT dopant in the PANI matrix is chosen as the best chemical sensor among the synthesized PANI with good reusability for hydrazine detection.