Nucleation and growth of catalyst-free ZnO nanostructures

TL;DR

This study investigates the catalyst-free synthesis of ZnO nanostructures, revealing how temperature and oxygen vacancies influence the formation of diverse nanostructures like nanotetrapods, nanorods, nanoflowers, and nanoparticles.

Contribution

It provides new insights into the nucleation and growth mechanisms of ZnO nanostructures without catalysts, highlighting the role of oxygen vacancies and temperature conditions.

Findings

ZnO forms first then converts to ZnOx with oxygen vacancies

Various nanostructures are formed depending on synthesis conditions

Temperature and oxygenation influence nanostructure morphology

Abstract

This paper deals with the investigations on the nucleation and growth of ZnO nanostructures in a catalyst free synthesis. The ZnO nanostructures have been formed by evaporation of Zn (99.99%) in O_2 and Ar atmosphere in single zone furnace under two temperature regions, region A (~1173-1073K) and region B (~873-773K). Through application of XRD and TEM techniques, it has been shown that first ZnO is formed which changes to ZnOx through creation of oxygen vacancies. The ZnOx acts as self-catalyst and leads to formation of various nanostructures. Those observed in the present investigation are nanotetrapods (1D, diameter ~ 70-450nm, length ~ 2-4.5mm) nanorods (1D, diameter ~ 45-95nm, length ~ 2.5-4.5mm), nanoflowers(2D,central core diameter ~ 90-185nm, length of petals/nanorod ~ 1.0-3.5mm) and nanoparticles (3D, size ~ 0.85-2.5mm). These nanostructures have been revealed by SEM explorations. Attempts have been made to explain the formation of the various nanostructures in terms of the creation and distribution of the ZnOx, the temperature as well as oxygenation conditions.