Comparison Between Wet and Dry Transfer Fe2O3-CNT Hybrid Thin Films as Room-Temperature Liquefied Petroleum Gas (LPG) Sensors

Abstract

Fe₂O₃-CNT hybrid thin films are promising candidates for room-temperature gas sensors with high sensitivity, rapid response, and recovery times. In this work, we reported the suitable fabrication strategies of Fe₂O₃-CNT hybrid thin films as liquefied petroleum gas (LPG) sensors by comparing the dry (without using aqueous solutions) and wet processes. Fe-CNT hybrid thin films were used as the primary material for synthesizing Fe₂O₃-CNT hybrid thin films, which were then annealed in air at 350oC to create α-Fe₂O₃. Characterizations by X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy (FE-SEM) confirmed the decoration of α- Fe₂O₃ nanoparticles on CNT surfaces. The transfer process had effects on the surface morphology and sensor characteristics. FE-SEM presents that the surface morphology of the wet-transfer Fe₂O₃-CNT films was web-like structures with a highly porous morphology. Whereas the surface morphology of the dry-transferred Fe₂O₃-CNT films was a branch-like structure. The I-V relationship of both annealed wet- and dry- films was non-linear indicating the present of n-type α- Fe₂O₃. Under 5 vol.% of LPG, the wet-transferred Fe₂O₃- CNT films have higher sensitivity (S = ~ 3% T_resp.= 10 s, t_rec.= 59s) compared to the dry- transferred Fe₂O₃-CNT films (S = ~ 1.4%, T_resp.=90s, trec.= incomplete recovery). Moreover, the wet-transferred Fe₂O₃-CNTs could detect LPG concentration at a lower value than 25% of LEL (Lower Explosive Limit) with rapid response and recovery time of 23 s and 49 s, respectively.