Synthesis and characterization of semiconductor oxide nanoparticles

Abstract

Environmental pollution is becoming more and more serious. The green house effect is brought about by the increase in the carbon dioxide concentration in the atmosphere. In order to detect and solve such environmental problems, semiconductor oxides, such as $TiO_2$, $SnO_2$, $WO_3$, ZnO, and $In_2O_3$, have been attracting a great deal of attention. These semiconductor oxides have good properties, such as large effective surface area, good thermal and chemical stability. From the viewpoint of gas sensor, $SnO_2$ surpasses other semiconductor oxide due to its high sensitivity to the reducing atmosphere and $TiO_2$ photocatalyst has received interest due to its powerful oxidation potential, high photo-stability and non-toxicity in water and air purification. However, the interaction of $SnO_2$ with a surrounding atmosphere at elevated temperature may lead the degradation of its electrical properties due to its relatively high equilibrium oxygen pressure. On the other hand, $TiO_2$ shows stable electrical properties within wide range of oxygen pressure and temperature. In addition to that, $TiO_2$ photocatalytic activity depends on coupling with other semiconductor particles, such as CdS, ZnO, $Cd_3P_2$, and $SnO_2$, due to the charge separation effect. And both of $SnO_2$ and $TiO_2$ crystallize in tetragonal symmetry, with two molecules per unit cell (space group $P4_2$/mnm). Because of the slight difference in radius between $Sn^{4+}$ cation (0.71A) and the $Ti^{4+}$ cation (0.68A), a $TiO_2-SnO_2$ solid solution can be formed over the entire range (0≤X≤1) at high temperature (Tc = 1430 ℃). PART I. Mixed Oxide Nanoparticles In this study, mixed oxide nanoparticles were prepared by hydrothermal synthesis. Their applications were the photocatalytic activity in $TiO_2-SnO_2$ system and NOx gas sensing properties in $WO_3-TiO_2$ system. $TiO_2-SnO_2$ nanoparticles were synthesized by hydrothermal treatment. The final crystalline phase and particle siz...