Structure formation oriented attachment

Self-assembled nanorods of vanadium oxide bundles were synthesized by treating bulk V2O5 with high intensity ultrasound [34]. By prolonging the duration of ultrasound irradiation, uniform, well defined shapes and surface structures and smaller size of nanorod vanadium oxide bundles were obtained. Three steps which occur in sequence have been proposed for the self-assembly of nanorods into bundles (1) Formation of V2O5 nuclei due to the ultrasound induced dissolution and a further oriented attachment causes the formation of nanorods (2) Side-by-side attachment of individual nanorods to assemble into nanorods (3) Instability of the self-assembled V2O5 nanorod bundles lead to the formation of V2O5 primary nanoparticles. It is also believed that such nanorods are more active for n-butane oxidation. 

By oriented attachment, Yu et al. [8] could obtain ZnS nanorods with cubic blend structure, in which the (11 1) planes of the component ZnS nanocrystals are nearly perfectly aligned. Pradhan et al. [9] have reported the formation of colloidal CdSe quantum wires by the oriented attachment of magic-sized clusters of CdSe. 

Fig.5 Classical (a) vs. non-classical crystallization (b,c). a Crystallization of hydroxyapatite (HAP) fibers from block copolymer aggregates [108], where the block copolymers adsorb to all faces parallel to the HAP c-growth axis resulting in whisker structures with occasional branches (see arrows). b,c Formation of single crystalline and defect-free BaS04 (210) oriented fiber bundles by the process of oriented attachment in experiments described in [109-111], Figure reproduced from [112] with kind permission of Editorial Universitaria, Universidad de Chile, Santiago, Chile...

Sun and co-workers developed a novel template-free method to prepare hollow ceria nanocubes with peroxyacetic acid as the oxidant. The formation mechanism was explained as having two steps including the oriented attachment of small nanoparticles to form nanocubes and Ostwald ripening to form the hollow structure dominated by solid-solution-solid mass transportation. 

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