Synthesis of ZnO nanospheres with uniform nanopores by a hydrothermal process

ZnO nanospheres were successfully synthesized by a hydrothermal process (S1 sample) and a wet-chemical method (S2 sample). Following synthesis, calcination treatment at 450 °C was performed for the sample prepared by the wet-chemical method (S3 sample). All of the samples possessed a regular spherical shape. A polycrystalline wurtzite structure was confirmed in the S1 and S3 samples by X-ray diffraction and selected area electron diffraction, whereas a mixture of ZnO nanoparticles and amorphous materials was observed in the sample S2. The surface area and pore structure of the samples were investigated by nitrogen adsorption–desorption measurements. Uniform nanopores with a diameter of 4.07 nm were present in the S1 sample while a broad pore size distribution was obtained for the S2 and S3 samples. The highest surface area was obtained for the S1 sample and a possible formation mechanism was studied.