Abstarct: Hematite (α-Fe۲O۳) is the most stable phase of iron oxide and it has been employed in gass sensors, catalytic and antibacterial agents. In the first part of the thesis, thin films of hematite were synthesized on top of glass substrates by spray pyrolysis at temperatures ۳۵۰, ۴۰۰, ۴۵۰ and ۵۰۰ ⁰C. Then the sensing performance of the films was investigates toward different concentration of ethanol vapor. The XRD patterns analysis of the synthesized films indicate crystallinity of the samples prepared at substrate temperatures of ۴۰۰ and ۴۵۰ ⁰C. FESEM image of thin films exhibited that with increasing the substrate temperature to ۴۰۰ and ۴۵۰ ⁰C the surface of the samples got more porous, but it got more uniform and consisting of nanosized grains for sample prepared at ۵۰۰ ⁰C. Gas sensing measurements toward ۲۰۰ppm ethanol vapor showed the response values of ۴۵, ۴۶, ۳۰ and ۲۰% for samples prepared at the substrate temperatures of ۳۵۰, ۴۰۰, ۴۵۰ and ۵۰۰ ⁰C. In the second part of this thesis, grapheme oxide nanoparticles were synthesized using conventional modified Hamers method. Also, α-Fe۲O۳/GO nanocomposite at different weight ratios were synthesized by hydrothermal technique. The XRD patterns analysis showed the highest crystallite size and the lowest strain for the composite prepared with ۰.۰۷۲ gr GO in α-Fe۲O۳, estimated using the Williamson-Hall method. FESEM image showed a decrease in the mean diameter of nanocomposites grains with increasing the α-Fe۲O۳/GO weight ratio. Also, according to UV-Vis analysis an increasing the GO weight raito in α-Fe۲O۳/GO nanocomposites. Antibacterial effects of all nanocomposites were measured toward both gram positive (S.aureus) and gram negative (E.coli) bacteria and reported in this thesis.