Issue 9, 2023

Controlling simonkolleite crystallisation via metallic Zn oxidation in a betaine hydrochloride solution

Abstract

Zinc oxide nanoparticles, with a hexagonal flake structure, are of significant interest across a range of applications including photocatalysis and biomedicine. Simonkolleite (Zn5(OH)8Cl2·H2O), a layered double hydroxide, is a precursor for ZnO. Most simonkolleite synthesis routes require precise pH adjustment of Zn-containing salts in alkaline solution, and still produce some undesired morphologies along with the hexagonal one. Additionally, liquid-phase synthesis routes, based on conventional solvents, are environmentally burdensome. Herein aqueous ionic liquid, betaine hydrochloride (betaine·HCl), solutions are used to directly oxidise metallic Zn, producing pure simonkolleite nano/microcrystals (X-ray diffraction analysis, thermogravimetric analysis). Imaging (scanning electron microscopy) showed regular and uniform hexagonal simonkolleite flakes. Morphological control, as a function of reaction conditions (betaine·HCl concentration, reaction time, and reaction temperature), was achieved. Different growth mechanisms were observed as a function of the concentration of betaine·HCl solution, both traditional classical growth of individual crystals and non-traditional growth patterns; the latter included examples of Ostwald ripening and oriented attachment. After calcination, simonkolleite's transformation into ZnO retains its hexagonal skeleton; this produces a nano/micro-ZnO with a relatively uniform shape and size through a convenient reaction route.

Graphical abstract: Controlling simonkolleite crystallisation via metallic Zn oxidation in a betaine hydrochloride solution

Article information

Article type
Paper
Submitted
20 Febr. 2023
Accepted
23 Febr. 2023
First published
02 Marts 2023
This article is Open Access
Creative Commons BY license

Nanoscale Adv., 2023,5, 2437-2452

Controlling simonkolleite crystallisation via metallic Zn oxidation in a betaine hydrochloride solution

S. Qu, E. Hadjittofis, F. Malaret, J. Hallett, R. Smith and K. S. Campbell, Nanoscale Adv., 2023, 5, 2437 DOI: 10.1039/D3NA00108C

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