Ligand-assisted deposition of ultra-small Au nanodots on Fe₂O₃/reduced graphene oxide for flexible gas sensors

The development of flexible room-temperature gas sensors is important in environmental monitoring and protection. In this contribution, by using 1-octadecanethiol (ODT) as a surface ligand, Au nanodots (NDs) with ultra-small size of ∼1.7 nm were deposited on the surface of α-Fe2O3/reduced graphene oxide (rGO). The Au ND-ODT/α-Fe2O3/rGO composite was fabricated into flexible gas sensors, which could detect NO2 gas down to 200 ppb at room temperature. Compared with α-Fe2O3/rGO, Au ND-ODT/α-Fe2O3/rGO showed enhanced sensing performance because of the beneficial effects of Au NDs, including facilitating the adsorption of NO2 molecules and forming ohmic-like contact with rGO and α-Fe2O3. In addition, the sensing performance of the composite was also influenced by the surface ligands of the Au NDs. Ligands with less polar terminal groups were found to be beneficial to charge transfer in the sensing film. Moreover, Au ND-ODT/α-Fe2O3/rGO-based flexible sensors showed negligible performance deterioration under moderately bent conditions, suggesting their potential to be used in portable and wearable devices.