In this Research, tin)II( oxide doped with graphene )SnO /graphene( nanocomposite was synthesized by hydrothermal method. Structural characteristics of the nanocomposites were studied using X-ray Diffraction )XRD(, Energy-dispersive X-ray spectroscopy )EDS( scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR), to confirm possible interactions which may have formed between the nanocomposites. Then, SnO /graphene nanocomposite was used as a sensitive and active layer for preparing a gas sensor for ethanol gas sensing. To optimize the condition and function of the sensor, the sensitivity and response of the nanocomposite at working temperature were investigated and important parameters such as response time, recovery time, and selectivity were determined. At the working temperature also at operating temperature, the sensor showed a sensitivity of about 12 times the concentration of 200 ppm and its response time was significantly lower. In addition, the SnO /graphene sensor had good selectivity over the target gas compared to other gases such as methanol, phenylethyl alcohol, acetone, n-hexane, etc. Due to the properties of bamboo charcoal and specific surface properties and its porosity structure, tin )II( oxide doped with bamboo charcoal )SnO/Bamboo charcoal( nanocomposite synthesis, this sensor was also studied. SnO/Bamboo charcoal nanocomposite showed a significant sensitivity to the low concentration of ethanol at 10 ppm which is better than the sensitivity and detection limit compared to SnO /graphene sensor.

In this research work, TiO2, TiO2-graphene, and TiO2-graphene/Alginate catalysts were synthesized and characterized by different methods such as XRD, TEM, SEM, and EDX analysis methods. Photocatalytic activity of prepared samples was investigated by photocatalytic removal of malachite green and methyl orange as cationic and anionic dyes from aqouse solutions. The results showed that photocatalytic activity of samples depends on the chemical structure of pollutants. TiO2-graphene/Alginate nanocomposite showed higher photocatalytic activity on the removal of cationic dye from aqouse solutions. While TiO2-graphene sample showed higher photocatalytic activity on the removal of anionic dye from aqouse solutions comparison. The figures of merit based on electric energy consumption (electrical energy per order (EEO)) were evaluated in the photodegradation of malachite green in the presence of prepared samples. The results indicate that less energy is consumed during the degradation of malachite green in the presence of TiO2-graphene/Alginate compared with other photocatalysts. To understand the nature of adsorption process, the equilibrium adsorption isotherms were studied. Based on results, for TiO2-graphene/Alginate, Langmuir isotherm model with correlation coefficient of 0. 995 fitted the experimental data, respectively. According to the Langmuir isotherm model, the maximum adsorption capacity of TiO2-graphene/Alginate for adsorption malachite green was about 86. 45 mg. g^(-1), which was about 4 times the adsorption capacity of Ag-TiO2. Also, recyclability of TiO2-graphene/Alginate nanocomposite was investigated. The results showed that TiO2-graphene/Alginate nanocomposite with recycling ability is highly stable.