In situ calorimetric investigation of ZnO transformation from flower-like nanostructures to microrod

The evolution of Zn₄₍OH₎²⁻$\text{Zn}{{(\text{OH})}_4}^{2-}$ solution during hydrothermal processing was studied using in situ calorimetry and the solid products were characterized by X-ray diffraction, scanning electron microscopy. It was shown that the formation of flower-like ZnO nanostructures exhibited first endothermic and then exothermic processes, of which the associated heat effect was measured as being −50.45 ± 0.01 J mol⁻¹. Flower-like ZnO nanostructures and ZnO microrod may be selectively formed simply based on the hydrothermal reaction temperatures. The mechanism for the flower-like ZnO nanostructures and ZnO microrod has been suggested.