The concept of colloidal molecules was first evoked by van Blaaderen in 2003 for describing small non-spherical colloids made of the aggregation of a small number of particles. He predicted original properties to the complex assemblies of such colloids, in particular in optics. This critical review deals with the different strategies reported for creating robust clusters of spherical particles which could mimic the space-filling models of simple conventional molecules. These routes concern either the controlled clustering of preformed colloids directed by coalescence, physical routes, chemical routes, or 2-D/3-D geometrical confinement, or strategies starting from a single colloid which is decorated by satellite colloids by taking advantage of controlled phase separation or nucleation and growth phenomena. These routes are compared from the viewpoint of the accessible shapes, their tunability and scalability (146 references).

Large amounts of regular tetrapods and hexapods made of a central silica core and four or six polystyrene satellite nodules were prepared with yields over 80% from 55 nm and 85 nm silica seeds, respectively. The robustness of the process is supported by extensive statistical analyses and large-field transmission electron microscopy images.

In addition to the role of CTAB surfactant, the strong impact of the AuNPs shape on their colloidal stability and aggregation behavior is demonstrated.

Time-resolved light scattering techniques reveal that viscous and solvation stabilization is relevant in ionic liquids and their water mixtures.

New luminescent poly(methylmethacrylate) (PMMA) nanocomposites with high content of different hexanuclear octahedral cluster building blocks, namely [Mo₆I₈(C₂F₅COO₆)]²⁻, [Re₆Se₈(CN)₆]⁴⁻ and [W₆Cl₁₄]²⁻ have been prepared by free-radical polymerisation. To do so, cluster complexes bearing a polymerisable ammonium counter-cation have been synthesised. In this way, we demonstrate that ionic assembling is a powerful tool to functionalise easily any type of anionic cluster units to be introduced in a PMMA organic matrix. All samples remain homogeneous, stable during several months, and retain the luminescence properties of the cluster precursor.