Colloidal superparticles are nanoparticle assemblies in the form of colloidal particles. The assembly of nanoscopic objects into mesoscopic or macroscopic complex architectures allows bottom-up fabrication of functional materials. We report that the self-assembly of cadmium selenide-cadmium sulfide (CdSe-CdS) core-shell semiconductor nanorods, mediated by shape and structural anisotropy, produces mesoscopic colloidal superparticles having multiple well-defined supercrystalline domains. Moreover, functionality-based anisotropic interactions between these CdSe-CdS nanorods can be kinetically introduced during the self-assembly and, in turn, yield single-domain, needle-like superparticles with parallel alignment of constituent nanorods. Unidirectional patterning of these mesoscopic needle-like superparticles gives rise to the lateral alignment of CdSe-CdS nanorods into macroscopic, uniform, freestanding polymer films that exhibit strong photoluminescence with a striking anisotropy, enabling their use as downconversion phosphors to create polarized light-emitting diodes.

Colloidal superparticles are size- and shape-controlled nanoparticle assemblies in the form of colloidal particles. Because these superparticles can exhibit physical and chemical properties different from both individual nanoparticles and their bulk assemblies, the development of superparticle synthesis has attracted significant research attention and is emerging as a new frontier in the field of nanotechnology. In this review, we discuss theoretical considerations on the nucleation and growth of colloidal superparticles. We then present recent progress in the synthesis and characterization of monodispersed colloidal superparticles, which are important for applications such as biomedical diagnosis, biological separation, and light emitting devices.

Quality and quantity: A non‐injection synthesis of high‐quality CdSe nanocrystals can be conducted in air, that is without the need for any oxygen‐free manipulation. The synthesis, which uses SeO2 as the selenium precursor, is suitable for the large‐scale industrial synthesis of high‐quality nanocrystals at low cost and has been generalized for the formation of other metal selenides, such as PbSe and Pd4.5Se nanocrystals.

A supramolecular chemistry approach is used to make supercrystalline spherical colloidal superparticles (SPs, see picture) from nanoparticles. Detailed mechanistic studies show that the formation of the SPs is a two‐step process. The major driving force for superparticle formation is the solvophobic interaction between nanoparticle building blocks and the growth solution; fine‐tuning the interaction led to a size‐controlled synthesis.

In this paper, we report an approach for using solvophobic interactions to synthesize well-defined colloidal superparticles from nonpolar-solvent-dispersible Fe3O4 nanoparticle artificial atoms. These colloidal superparticles possess a “single-supercrystal” structure, of which Fe3O4 artificial atoms occupy the lattice points of a face-centered cubic superlattice. In addition, these superparticles exhibit superlattice fringes under a low-resolution TEM, providing an interesting analogue to the lattice fringes of colloidal nanocrystals under a high-resolution TEM. Moreover, these superparticles can be further assembled into close-packed solid structures, demonstrating their role as a new type of building block in nanoscience.