Synthesis and fluorescence sensing of energetic materials using benzenesulfonic acid-doped polyaniline

The Fluorescence sensing technique for trace detection of High Energy Materials (HEMs) has gained more attention in recent times. In the present paper, the interaction between the fluorophore and HEMs is studied using spectroscopic and electrochemical techniques. The fluorophore polyaniline (PANI) was functionalised by doping it with benzenesulfonic acid (BSA) to increase the processability, and mobility of π-electrons along with decreased π-stacking. It is observed that upon doping the solubility of BSA-PANI is increased, facilitating a higher quenching by commercial explosives, i.e., RDX, CL-20, CL-20:RDX cocrystal. The interaction studies undertaken though fluorescence quenching, FTIR and Resonance Raman studies shows that the benzenoid unit, polaron and bipolaron nitrogen in BSA-PANI interact with nitro groups of HEMs and form a charge-transfer complex between HEMs and BSA-PANI undergoing predominantly a PET mechanism. LOD value is found to be least for Cocrystal (1.876 × 10^–5 M) when compared to other HEMs 3.191 × 10^–5 M (CL-20), 5.904 × 10^–5 M (RDX), 3.734 × 10^–5 M (PETN) indicating that cocrystal can be detected in trace level. The collaborative study between cyclic voltammetry and the observed results of fluorescence quenching, revealed that the emeraldine salt form of (BSA-PANI) is sensitive to HEMs.