In the process of oriented aggregation, the single crystalline nanobat-like structure forms through oriented arrangement by rotating adjacent divergent sized rectangular structure (e) to allocate identical crystallographic orientation [37,38]. It can be realized that controlled aggregation likely takes place along [0 1 0] direction which has highest reactivity [39]. In general, during the anisotropic crystal growth, tiny primary crystals at their high-energy surfaces are energetically favored since the formation of large crystals can greatly reduce interfacial energy. Thus, we can conclude that the ultimate crystal with well-defined shape and morphology can be attained by adjusting crystal along the three preferred directions pursued by reorganization and crystallization process. To substantiate the formation of rectangular shaped nanobat-like structure via orientation attachment, TEM study was carried out
( f ).