Polyol synthesis of Al-doped ZnO spherical nanoparticles and their UV–vis–NIR absorption properties

Al-doped ZnO spherical nanoparticles were synthesized using a polyol method, and the particle sizes and absorption spectra from the ultraviolet to the near-infrared were investigated in detail. Al-doped ZnO spherical nanoparticles with sizes of about 70 nm were obtained, with zinc–aluminum layered double hydroxide as a by-product. The aluminum concentration of the obtained nanoparticles was approximately 1.3% whether the starting aluminum concentration was 2% or 10% in the polyol process, suggesting that 1.3% is the solid solubility limit of Al in ZnO. A homogeneous Al-distribution, a peak shift in an X-ray diffraction pattern, and some near-infrared absorption reveal that aluminum ions were doped in the ZnO lattice. When the synthesis temperature was 150 °C for the polyol process without heat treatment, we obtained Al-doped ZnO spherical nanoparticles not only with high transparency in the visible light region but also with absorption properties in the ultraviolet and near-infrared.