Investigation of morphology (SEM)
The surface morphology ofthe ZnO samples synthesized by microwave irradiation is analyzed using SEM micrographs and it is shown in Fig.
3A and B. All the SEM micrographs reveal that the different pH of the precursor solution affect the particle size, length and diameter of the nano rods and not their morphology [18].As shown in Fig. 3.2, at pH 9 and 11, ZnO powder exhibited well
separated rods with few tetrapod and flower-like structure with each petal having the single hexagonal rod shape respectively.
When the pH of the solution was maintained at 13, shorter nano rods were
formed in aggregation. As can be seen from the SEM images, it could be inferred that the solution pH keeping the concentration of the Znþ2 ion and other parameters constant play a vital role in determining the morphology of the ZnO crystals.
When the pH of the solution was 9, the length and diameter of the nano rods are around
4.96 mm and 704.8 nm, respectively.
The length and diameter of the A3 rods are approximately twice than that of the A1 rods formed at pH 13.
The aspect ratios are listed in Table 2 and they vary in the order A1oA3oA2.
Thus higher alkalinity of the precursor solution resulted in bigger and longer rods. The variation in the aspect ratio and crystallinity of the samples with pH is depicted in Fig. 4