Mechanistic Insight into the Turn-Off Sensing of Nitroaromatic Compounds Employing Functionalized Polyaniline

Conducting Polymers (CPs), in recent times have contributed significantly in the detection of High Energy Materials possessing nitro functional groups through fluorescence quenching studies. Camphor sulphuric acid doped polyaniline (C-PANI) is studied with a view to obtain easily processable PANI without pi-stacking for the detection of Picric acid(PA) and p-nitro toluene(pNT) in trace levels. The quenching constant and limit of detection were found to be 2.236x10(-6) M and 6.14x10(-7) M for PA and 1.9447x10(-7) M and 3.57x10(-7) M for pNT, respectively showing a very good sensitivity in detection. Resonance Raman spectroscopy (RRS) showed the involvement of the bipolaronic and benzenoid group in the charge transfer complex formed between the conducting polymer and the analyte. The photoluminescence studies indicated a predominant PET mechanism. The electrochemical studies employing cyclic voltammetry gave higher band gap on comparison with absorption studies. The positive and negative shift in oxidation and reduction potential of polymer-analyte was observed and collaborated with the fluorescence studies to understand the possible fluorescence quenching mechanism from electrochemical approach.