Synergistic Charge Transfer and Surface Defect Effects in Cellulose-PANI-ZnO Sensors for Early Lung Cancer VOC Diagnosis

Abstract Non-invasive breath analysis of volatile organic compounds (VOCs) represents a promising pathway for early-stage lung cancer detection. In this study, cellulose-PANI-ZnO nanocomposites (ZO1, ZO2, and ZO3) with component ratios of 1:2:1, 1:2:2, and 1:2:3 were synthesized and systematically characterized using XRD, UV-DRS, PL, SEM, and EIS techniques. The analyses confirmed the successful incorporation of crystalline ZnO along with strong interfacial interactions that promoted enhanced charge transport across the p-n heterojunction and facilitated defect-mediated gas adsorption. Gas sensing evaluations toward clinically relevant lung cancer VOC biomarkers-including toluene, benzene, ethanol, acetone, and hexane-revealed distinct selective detection profiles. ZO1 demonstrated the highest sensitivity toward toluene and acetone, benzene showed enhanced interaction with ZO2, while ethanol and hexane exhibited optimal responses with ZO3. Overall, toluene and ethanol produced the strongest signals across the composite series, while hexane consistently presented a prominent secondary response in all sensing layers. The observed selectivity and sensitivity trends arise from synergistic effects involving interfacial charge transfer, controlled ZnO-PANI heterojunction formation, and optimized composite stoichiometry. These results highlight the potential of cellulose-PANI-ZnO nanocomposites as promising room-temperature sensing platforms for breath-based detection of lung cancer-associated VOCs.