Synthesis, Surface Morphology, Gas Sensor, DSC Technique and Third-Order Behavior of Conducting Polymer

The compound polyaniline (Poly-ANI) with different concentrations of (H₂SO₄) sulfuric acid has been synthesized by the chemical polymerization method. The prepared compounds have been characterized using number of techniques including FTIR, FE-SEM, EDS and DSC. Additionally, UV-Vis spectroscopy employed for studying the linear optical properties of polymer with different acid concentrations. Third order optical nonlinearity was characterized using Z-scan at 532 nm. The results showed that the nonlinear refractive index has a negative sign. It was observed that the nonlinear refractive index changes in different ratios of H₂SO₄. The high value of nonlinear refractive index ( $n_2$ ) obtained along Z-axis is $74.62\times {10}^{-7}$ cm²/W, and the corresponding ${\chi }^3$ is 21.5 × 10^-5 esu. Also, the Poly-ANI film shows the response to NH₃ gas sensing in the range 20 ppm-250 ppm and can be used for NH₃ sensing application.