Stimuli Responsive PANI Based Composites for Optical Sensing Applications

Abstract

Stimuli-responsive polymeric materials have emerged as powerful platforms for next- generation optical sensing technologies due to their tunable physicochemical properties and rapid response to environmental changes. In this work, polyaniline (PANI)-based composites were synthesized and engineered to exhibit sensitivity toward external stimuli such as pH, light, and chemical vapors. PANI was selected as the primary functional component because of its inherent redox activity, environmental stability, controllable conductivity, and strong optical transitions in the UV-Vis region. To enhance its sensing performance, PANI was incorporated into composite structures with carbon-based nanomaterials and biodegradable supports, providing improved surface area, enhanced charge-transfer pathways, and higher optical response. Structural characterization through FTIR, XRD, and Raman spectroscopy confirmed successful composite formation and preserved PANI backbone vibrations. UV-Vis spectroscopy demonstrated distinct π→π* and n→π* transitions, accompanied by measurable shifts in absorbance intensity as a function of pH and analyte concentration, validating the composite’s optical sensitivity. Raman spectroscopy further revealed changes in vibrational modes associated with protonation and deprotonation, indicating rapid and reversible responsiveness to chemical stimuli. Optical sensing experiments showed that the PANI-based composite exhibited high sensitivity, stability, and repeatability, particularly in pH-triggered optical modulation, making it an excellent candidate for real-time environmental and biochemical sensing. The results highlight that stimuli-responsive PANI composites offer a cost-effective, flexible, and highly tunable platform for optical sensing systems. Their robust performance positions them as promising materials for future smart sensors, environmental monitoring tools, and optical detection devices.