M. S. Thesis Colloquium: Synergistic Enhancement of Humidity Sensors: Arc-Discharge CNS, Acid Functionalization, and PANI Integration

Title: “ Synergistic Enhancement of Humidity Sensors: Arc-Discharge CNS, Acid Functionalization, and PANI Integration.”

Humidity sensing is essential for applications spanning environmental monitoring, industrial processing, and healthcare, yet the development of materials that simultaneously offer high sensitivity, fast response, and long-term stability remains challenging due to limitations in conductivity and surface activity of conventional systems. This thesis addresses these challenges by investigating the design and development of carbon nanosphere (CNS)/polyaniline (PANI) nanocomposites, with a focus on exploiting the structural advantages of arc-discharge-derived CNS and their functionalized. Highly graphitized CNS were synthesized using the electric arc-discharge method at temperatures exceeding 3000 ◦C, followed by controlled acid functionalization to enhance surface reactivity and inter facial compatibility. The resulting pristine CNS and functionalized car bon nanospheres (f-CNS) were incorporated into PANI matrices via in-situ chemical polymerization to form nanocomposites with improved dispersion and interfacial interactions. Comprehensive characterization using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning and transmission electron microscopy (SEM, TEM), and Brunauer–Emmett–Teller (BET) surface area analysis con firmed enhanced structural ordering, surface area, and strong coupling between constituents. Systematic humidity sensing studies demonstrate that the incorporation of CNS and f-CNS significantly improves sensor performance, with the 10 wt% f-CNS/PANI composite exhibiting a maximum response of 40.18%, along with rapid response and recovery times of 20 s and 5 s, respectively, outperforming pristine CNS, pure PANI, and all other hybrid systems. The observed enhancements are attributed to synergistic effects arising from increased active surface area, polar groups, and and improved charge transport and proton conduction pathways. The findings establish arc-discharge-derived and functionalized CNS as effective nanofillers for high-performance polymer-based humidity sensors and provide fundamental insights into structure property relationships for the rational design of next-generation sensing materials.