Effect of pH on ZnO nanoparticle properties synthesized by sol–gel centrifugation

ZnO nanoparticles were synthesized at different pH values by the sol–gel method and centrifuged at 3000 rpm for 30 min. The ZnO powders agglomerate when synthesized in acidic and neutral conditions (pH 6 and 7). Fine powders were obtained when the pH of the sols was increased to 9. The maximum crystallite size (25.36 nm) of the ZnO powder was obtained at pH 9. The particles sizes of the ZnO synthesized between pH 6 and 11 were in the range of 36.65–49.98 nm. Ultraviolet–visible analysis (UV–vis) also demonstrated that ZnO synthesized from pH 8 to 11 has good optical properties with band gap energy (Eg) between 3.14 and 3.25 eV.