الفهرس 
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Abstract
There is a great need today to offer a gas sensor (GS) device for improving the environment, safety, and regulation of gases. This type of sensor is also in high demand in the increasing transportation industry and in domestic and industrial applications. GSs are used to detect gases, distinguish odors, and monitor general changes in the gas atmosphere. Because of the concern for safety requirements in domestic uses, developing GSs to monitor combustible gases is critical.
The semiconductor sensor has the best gas sensing capabilities in that environment among the numerous techniques of gas detectors and sensors utilized in the industry. According to extensive research into sensing materials, tungsten trioxide (WO3) has excellent sensing properties.
The thesis is divided into three sections; the first part is the preparation of nanomaterials, including the precursor of Na2WO4.2H2O and different weight ratios of PdCl2 solution, which are synthesized using the hydrothermal technique at 120 °C for 24h to fabricate Tungsten oxide (WO3) and WO3: Pd nanopowders. Different weight ratios (0.3, 0.6, 0.9, and 1.2 %) of Pd-doped WO3 GSs are considered during the synthesis, which is sensitive to various low gas concentrations.
Secondly, the characterization tools, including the nanopowders surface structure, are investigated using field emission scanning electron microscopy (FESEM). The chemical bound of the produced materials is also determined using Fourier-Transform Infrared (FTIR) Spectroscopy. X-ray Diffraction (XRD) is used to study the crystalline structures, while High-Resolution Transmission Electron Microscopy (HRTEM) is used to determine the atomic structure of the samples. The presence of tungsten and palladium is detected using EDX spectra. The optical characteristics of produced nanoparticles were investigated using a UV-VIS spectrophotometer at room temperature; the
IV
measurement was conducted in the wavelength range of 190-1000 nm. The characteristics of the electrical I-V curves of doped and undoped gas sensors are also investigated.
Thirdly, the sensing characteristic of the manufactured sensors is tested against (carbon dioxide, LPG, oxygen & nitrogen) recording very acceptable results.