Preparation And Properties Of Doped ZnO Nanoparticles

The electrical and optical properties of ZnO can be significantly improved by doping other elements. High doping concentrations of ZnO powders have good prospects in electromagnetic shielding, conductive and antistatic materials, photocatalyst, solar cells, and many other fields. However, the doping concentrations of ZnO powders reported are no more than10%.High concentration (up to20mol%) Ga-doped ZnO (GZO) and Al-doped ZnO (AZO) nanoparticles have been prepared by a simple sol-gel combustion method. The crystal structures, morphology, chemical composition, and crystallite sizes/lattice fringe images of the nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), and energy-dispersive X-ray analysis (EDX).The results show that Ga and Al element have been successfully doped into ZnO crystal structure, and all GZO and AZO samples are of a single phase and have the same wurtzite structure as pure ZnO. The results also indicate that the crystal growth of the ZnO can be suppressed by the presence of Ga and Al, and the ZnO crystal size can be reduced to around5.7nm at the presence of20mol%Ga, and6.4nm at the presence of20mol%Al.The optical properties have been analyzed by UV-VIS-NIR spectroscopy, and it indicates that the range of the optical band gap energy (Eg) for the GZO nanoparticles is3.058～3.225eV, and3.168～3.237eV for the AZO nanoparticles. The reflectance spectra show that both GZO and AZO samples have very high reflectivity in the wavelength region between450to2500nm, which indicated the potential use in cooling materials.The photocatalytic activities have been evaluated in terms of the adsorption and degradation of methyl orange (MO) solution under UV light (or solar light) irradiation. The results showed that the photocatalytic activities and the adsorption capacities increase with Ga concent. For AZO the photocatalytic activities and the adsorption capacities increase with Al when the concent is between0～15mol%, while the increase dopping amount from15to20cannot further increase the absorption capacity and photocatalytic activity.The molecular weight of MS sealant decreased after the added of ZnO and AZO nanoparticles. The results indicate that both ZnO and AZO nanoparticles can degrade MS sealant under UV irradiation. Moreover, pure ZnO and AZO-10have better degradation efficiency.The transmittance of PE film decreased with the adding of ZnO and AZO nanoparticles, indicating both of them have cooling effect. Moreover, the transmittance of AZO-5is the lowest, suggesting the cooling effect of it is the best, and may be applied in cooling materials.