Keywords

Abstract

ZnO nanorods;

 Hydrothermal method; 

Zinc substrate; 

High alignment; 

Seed layer; 

Thermal oxidation

In this work, uniform and highly aligned ZnO nanorod arrays were simply synthesized on zinc plates by hydrothermal method using zinc–ammonia complex solution. Effects of ZnO seed layer formation, Zn(NO₃)₂ concentration and NH₃/Zn(NO₃)₂ mole ratio (R) in the reaction medium on the morphology and crystal structure of nanorods were investigated in detail. ZnO nanorods grown on zinc surfaces were highly crystalline and had a hexagonal wurtzite structure, as revealed by XRD analysis. In addition, the dominant crystal growth direction was in c-axis, indicating the verticality of the nanorods. SEM images showed that one-dimensional (1D) ZnO nanorods with high verticality and number density were synthesized on seeded plates whereas randomly oriented arrays were grown on non-seeded surfaces. Increase in the Zn²⁺ concentration changed the top ends of the rods from tapering to hexagonal ends; and also led to an increase in the average size and verticality of the nanorods. The increase in R value (or i.e., amount of NH₃) caused the rods to misalign on the surface and decrease in size. The size of well-aligned nanorods can be adjusted from 50 to 260 nm in diameter and 0.11 to 6 mm in length by changing the reaction parameters, implying their large potential to be used in photocatalytic and also in electronic applications.

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