Abstarct: In this thesis, the morphology, structural, and optical properties of hematite-baxsed nanocomposite samples, including α-Fe₂O₃/rGO, α-Fe₂O₃/PANI, and the quaternary composite α-Fe₂O₃/PANI/Ag/MWCNT, synthesized via a hydrothermal method, were investigated. The synthesized nanocomposites were subsequently employed in the fabrication of Schottky-type gas sensors for the detection of acetone and ammonia gases, as well as for the evaluation of their antibacterial properties. According to the FESEM images, in the α-Fe₂O₃/rGO nanocomposite, hematite exhibits a cubic morphology, while the reduced graphene oxide shows a sheet-like and porous structure. In the α-Fe₂O₃/PAni nanocomposite, hematite particles possess a rod-like structure, and polyaniline exhibits a fibrous morphology, resulting in a uniform composite. In the quaternary composite α-Fe₂O₃/PAni/Ag/MWCNT, multi-walled carbon nanotubes (MWCNTs) are uniformly dispersed throughout the structure, and silver nanoparticles are well-decorated on their surface. The gas-sensing results revealed that the Schottky sensor baxsed on α-Fe₂O₃/rGO exhibited a response of 135.93% toward 1 ppm acetone gas. The Schottky sensor baxsed on α-Fe₂O₃/PANI successfully detected 0.5 ppm ammonia gas with a response of 10.2%, demonstrating a high sensing capability. Furthermore, the Schottky sensor fabricated from the quaternary composite α-Fe₂O₃/PANI/Ag/MWCNT exhibited a response of 15.42% toward 0.25 ppm acetone gas, making it a promising candidate for room-temperature acetone sensing applications. Additionally, the antibacterial performance of the quaternary composite was evaluated against Staphylococcus aureus and Escherichia coli bacteria. The results indicated that the sample containing 2.5 wt% MWCNTs exhibited the highest inhibitory effect against the growth of both bacterial strains.