Unified ZnO Q-dot growth mechanism from simultaneous UV–Vis and EXAFS monitoring of sol-gel reactions induced by different alkali base
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This article aims to give experimental evidences of the universality of main steps involved in ZnO nanoparticles formation and growth from sol-gel process. In this way, we revisit the effect of the alkali base (LiOH, NaOH, KOH) used to induce the hydrolysis-condensation reaction in order to unfold the ZnO Q-dot formation mechanisms by using simultaneous time resolved monitoring of zinc species and Q-dot size by combining EXAFS and UV–Vis spectroscopy. Irrespective of the alkali base used, nucleation and growth of ZnO Q-dots occur by consumption of zinc oxy-acetate precursor. Higher amounts of ZnO nanocrystal are produced as the strength of the base increases. After achieving the steady state equilibrium regime the Q-dot growth occurs initially by oriented attachment coalescence mechanism followed by the Ostwald ripening coarsening. The dependence of the formation and growth mechanisms on the base strength allows the fine tuning of the Q-dot size and photoluminescence properties.