Silver-coated polypyrrole/indium oxide (Ag-PPY/In₂O₃) nanocomposites for humidity sensing

The development of sustainable humidity sensors is crucial for next-generation electronics and telecommunication systems. In this study, silver-coated polypyrrole (Ag–PPy) nanocomposites integrated with indium oxide (In₂O₃, 2–10 wt%) were synthesized via a green route using phytochemical-rich green tea extract as a natural reducing and stabilizing agent. This eco-friendly approach enabled controlled nanoparticle formation while minimizing hazardous by-products. Comprehensive structural and morphological characterization confirmed the successful fabrication of hybrid nanocomposites with tunable physicochemical properties. Humidity-sensing investigations revealed that increasing In₂O₃ content enhanced baseline resistance and sensitivity. Composites containing 6 % and 10 % In₂O₃ exhibited sharp decreases in resistance with increasing relative humidity, demonstrating superior sensitivity, whereas the 2 % composite provided a stable, reversible response, ensuring reliable operation. The improved sensing performance arises from the synergistic effects of the conductive PPy framework, plasmonic Ag, and semiconducting In₂O₃, which collectively facilitate charge transport and water adsorption. These findings highlight Ag–PPy/In₂O₃ nanocomposites as promising eco-engineered materials for humidity sensing in flexible electronics, environmental monitoring, and smart communication technologies.