Nucleation and Growth of ZnO in Organic Solvents - an in Situ Study

Abstract

ZnO is a metal oxide material which possesses versatile properties and applications. Therefore, the target-oriented preparation of ZnO has become a major issue. Many preparation techniques involve bottom-up methods from precursor solutions. In the current contribution, a special precursor system is described that enables a fine-control of kinetic parameters for the nucleation and growth of ZnO in various organic solvents. A large variety of analytical techniques could be applied in an in situ fashion to probe for the ZnO formation at all times and all length scales. Among the analytical techniques are UV/vis, Raman, Fluorescence, X-ray absorption, 1H NMR-spectroscopy, dynamic light-scattering, and TEM. Three different regimes for nucleation and growth with different characteristics could be identified. Furthermore, the effect of different parameters on the resulting ZnO particle size was investigated.

Shape Anisotropy Influencing Functional Properties: Trigonal Prismatic ZnO Nanoparticles as an Example

“…The reaction of the Zn 4 O 4 precursors with an equimolar amount of water (see Scheme 1 ) and the resulting nucleation and growth of ZnO was reported recently in a detailed in situ study. [ 31 ] Because the emerging inorganic particles were not stabilized by surfactants, as expected, it was observed that the growth period of ZnO is very short due to rapid precipitation of ZnO. [ 31 ] When the reaction is performed in the presence of a suitable surfactant, colloidal stabilization occurs and one obtains transparent solutions.…”

“…[ 31 ] Because the emerging inorganic particles were not stabilized by surfactants, as expected, it was observed that the growth period of ZnO is very short due to rapid precipitation of ZnO. [ 31 ] When the reaction is performed in the presence of a suitable surfactant, colloidal stabilization occurs and one obtains transparent solutions. The results obtained by the latter experiments will be discussed only shortly because they have to be seen as references for the new synthesis approach towards colloidal ZnO nanoparticles described in Section 2.2.…”

“…The rather enduring presence of amorphous ZnO particles is worth noting, as it has been recognized recently that crystalline ZnO nanoparticles form much earlier when no additive is present. [ 31 ] Obviously, the surfactant interacts with the forming inorganic phase early in the reaction. Similar observations have been made by Guizard and Ayral for sol-gel processes leading to titania.…”

Li-doped ZnO nanorods with single-crystal quality – non-classical crystallization and self-assembly into mesoporous materials

“…[37][38][39] All other chemicals were obtained from chemical suppliers and were purified and/or dried prior to use.…”

The evolution of crystalline ordering for ligand-ornamented zinc oxide nanoparticles

“…7,8,10 Sol-gel processes, and in particular reaction pathways in organic solvents have become increasingly attractive in comparison to aqueous routes, as it is easier to tune the nanoparticle size, shape and crystallinity. 11 With available knowledge of chemical reaction pathways, 4,12 in situ small angle X-ray scattering (SAXS) and UV-vis spectroscopy have given access to the nucleation and growth behaviour, 3,4,7,8,[13][14][15][16] however with somewhat contradictory ripening rates and growth models. 13 Theoretical attempts to describe ZnO nanoparticle nucleation have involved molecular dynamics (MD) simulations 17 knowledge, besides the Spanhel model, all other experimental and theoretical approaches have so far assumed the nucleation of dense particles, which further grow or agglomerate.…”