# Recent Advances in Research from Nanoparticle to Nano-Assembly: A Review
## 2 Oriented Assembly of Nanomaterials
Inorganic intermediates were created by performing a partial exchange of Cu\({}^{+}\) with Cu\({}_{2}\)S domains [44] since Cu-based chalcogenides can also attach through oriented attachment. The high reactivity of Cu\({}^{+}\) led to the exchange of both ends of the asymmetric NR, forming small Cu\({}_{2}\)S domains with higher and lower curvatures. As Cu\({}^{+}\) is incorporated into Cu\({}_{2}\)S domains, the driving force for cation exchange gradually decreases, ultimately leading to preferential dissolution at the tail-end region due to size-dependent solubility and resulting in mainly epitaxial head-to-head linking (Figure 1c). For building structural complexity, inorganic intermediates are an excellent synthetic strategy. For example, the Cu\({}^{+}\)-based linkage of tail-to-tail linked dimers is capable of secondary joining, resulting in an orderly arrangement of asymmetric NRs (Figure 1d) [46; 49]. It is essential to join NPs in a stoichiometrically controlled manner to form heterostructures without forming links between NPs with the same composition. Conventional methods of attachment pose an inherent challenge. A facile method of joining colloidal semiconductor NRs of different shapes and compositions in a stoichiometrically controlled manner was conducted by linking CdTe TPs to CdSe NRs in solution. The fabrication of complex semiconductor nano heterostructures was simplified by synthesizing CdTe TPs and CdSe NRs separately, then combining them through partial cation exchange. The CdTe TPs and CdSe NRs form small domains of Ag\({}_{2}\)Te and Ag\({}_{2}\)Se after partial cation exchange. After the surface ligands have been selectively removed from the Ag chalcogenide surfaces, a cohesive bond is formed when the unpassivated surfaces meet. Because many of the NRs in Ag\({}_{2}\)Te-tipped CdTe TPs haven't been exchanged for Ag\({}^{+}\), they are sterically prevented from joining, enabling heterolinking with Ag\({}_{2}\)Se-tipped CdSe NRs. TPs and NRs are linked spontaneously by the fusion of Ag\({}_{2}\)Te-tipped CdTe TPs and Ag\({}_{2}\)Se-tipped CdSe NRs, ensuring electronic coupling between TP and NR [50]. Due to the energetic favorability of the process, bare silver chalcogenide facets form numerous covalent bonds with the CdSe NRs at the tips of CdTe TPs. Based on the HAADF image (Figure 1g) of the NR-joined TPs, it is evident that several hetero nanostructures are formed via joining CdTe TPs with CdSe NRs, resulting in hetero-linked CdTe\(-\)Ag\({}_{2}\)Te/Ag\({}_{2}\)Se\(-\)CdSe structures. Unlike pristine CdSe NRs, homo-linked CdSe NR chains are rare, due to the relatively small proportion of CdSe NRs that undergo Ag\({}^{+}\) exchange. It was also rare to find chains or free TPs that were homo-linked. Heterostructures can thus be produced very effectively through the exemplified technique. As illustrated in Figure 1f, the morphology of the converted CdTe\(-\)CdSe TP\(-\)NR structure is preserved, as expected from cation-exchange reactions carried out at room temperature. The PL spectrum shifts blue with increasing pump fluence, as shown in Figure 1h. Consequently, this observation relates to a Coulombic interaction between electrons and holes separated by space [51; 52; 53; 54]. These works of controlled OA were advanced by [PERSON] et al. ; by linking non-spherical semiconductor nanoparticle building blocks facet-to-facet, they were able to synthesize branched nanostructures, which is inherently different from the traditional process of heterogeneous nucleation and growth. The principle of facet-to-facet linking was illustrated for the first time using monoclinic Ag\({}_{2}\)S-seeded ZnS NRs [47]. Nanoparticle OA creates bipods and tripods by covalently linking the facets of proximal Ag\({}_{2}\)S NPs with ZnS NRs with Ag\({}_{2}\)S tips. As a result of gold deposition experiments, it was concluded that the sides of the Ag\({}_{2}\)S tip have more S than Ag, resulting in angular rather than linear structures.