Abstarct: In this thesis, the morphological, structural, and optical characteristics of molybdenum disulfide (MoS2)-baxsed nanocomposite samples, including MoS2/PANI, MoS2/RGO, and MoS2/PANI/RGO nanocomposites, prepared by hydrothermal method, were studied. Then, the synthesized nanocomposite samples were used as a sensing material in the fabrication of resistance and Schottky sensors to detect ammonia gas. The XRD spectra confirmed the successful synthesis of nanocomposites, and Raman spectroscopy showed the formation of both 1T- and 2H-phases of MoS2 in nanocomposite samples. According to FESEM images, MoS2/PANI nanocomposites have been composed of PANI nanofibers surrounded by MoS2 nanosheets and created a porous morphology that influenced their sensing characteristics significantly. The FESEM images show that MoS2/RGO nanocomposites are constructed of ultrathin MoS2 nanosheets that cover the surface of RGO. Also, the FESEM images of the MoS2/PANI/RGO ternary nanocomposite sample reveal that MoS2 nanosheets are grown on RGO nanosheets, and the PANI nanofibers anchored onto the nanosheets of the flower-like MoS2. Additionally, a large number of discrete gold nanoparticles with a uniform distribution were observed on the surface of samples of ternary nanocomposite MoS2/PANI/RGO and MoS2 loaded with gold. The results of the sensing tests showed that the response of the MoS2/PANI nanocomposite-baxsed sensor, with the same weight ratio of ammonium heptamolybdate and PANI, was obtained to be about 1.44% at 100 ppm ammonia gas. The response of the MoS2/RGO nanocomposite-baxsed sensor, with 10% of GO, was also obtained to be about 1.41% at 500 ppm ammonia gas, which is much more than MoS2- and PANI-baxsed sensors. Among all fabricated resistive-chemical and Schottky sensors, the Schottky sensor of the ternary nanocomposite sample loaded with gold had the highest response value of 76.88% to 50 ppm of ammonia gas. The sensor can also detect ammonia as low as 500 ppb and exhibits high selectivity, making it an attractive candidate for ammonia gas sensing applications at room temperature.