Yolk-shell nano-particles (also named nano-rattles), are in the center of many studies thanks to their interesting properties in multiple fields ranging from medicine to physics.^[1] These properties come from both, the non-homogeneous composition of the nano-rattles, and also from the particular environment around the core, as it behaves like a nano-reactor. Synthesizing such nano-objects is challenging,^[2] but we decided to take it one step further by organizing them in different ways and levels for optical effects.

In a first part we focused on obtaining a controllable and reversible way of aggregating the nano-particles, using silica spheres as model. The second part focused on the development of anisotropic and magnetic nano-particles and on how to use these as starting point for the synthesis of the desired nano-rattles. Having such a high control over the organization of nano-materials might allow to control opalescent properties of the aggregates.

Figure 1. Schematic representation of the different synthesis and organization steps