Kinetic analysis of zinc oxide anisotropic growth in supercritical water

Abstract We examined the effect of KOH addition on the anisotropic growth of ZnO nanoparticles during supercritical hydrothermal synthesis using a continuous flow reactor at 400 °C and 30 MPa. Time-resolved experiments revealed that sphere- and rod-like nanoparticles were synthesized and that the KOH concentration affected the growth rate and anisotropy of the particles. A kinetic analysis and equilibrium calculations indicated that the increase in the growth rate was due to the larger number of hydroxyl group from the dissolved Zn species, and that ZnOH+ contributed to the growth along the c-axis of the wurtzite crystal structure, while Zn(OH)3- and Zn(OH)42- contributed to the growth along the a-axis compared with ZnOH+.