Synthesis of ZnO Crystals under Bio-Friendly Conditions

: Hydrothermal ZnO synthesis optimalization

Abstract

Zinc oxide is a material of high interest due to its wide variety of applications caused by its wide bandgap and piezoelectric properties. To optimize the efficiency of the piezoelectric crystal, the dimensions of the crystal need to be optimized. Theoretically, the maximum potential will be achieved by growing a thin platelet with a [0001] growth direction. However, these platelets cannot be grown using the current synthesis techniques. To grow ZnO platelets a matrix may be used. Since in nature the size, shape and structure is precisely controlled, as is shown by the mineralization of hydroxyapatite platelets in collagen. A collagen matrix may be used. To use collagen as a template for crystal growth a mild reaction pH (5-9) and temperature (40 °C) is required. Otherwise the collagen will denaturate and lose structure. Currently the synthesis of ZnO at mild pH requires a reaction temperature of > 50 °C, this temperature is needed for thermal base release. To circumvent this temperature restriction a direct base titration strategy is investigated. Using ammonia titration at 37 °C and low pH (6.0 – 6.5), ZnO can be synthesized. In the reaction product a major phase of layered basic zinc acetate (LBZA) is found. The ZnO yield can be increased by using additives such as l-Lysine or poly(allylamine) to promote crystal growth. This work shows that ZnO can be synthesized at collagen friendly conditions.

Date of Award	29 Apr 2020
Original language	English
Supervisor	Mark M.J. van Rijt (Supervisor 1) & G. (Bert) de With (Supervisor 2)