From Nanoparticle Assembly to Monolithic Aerogels of YAG, Rare Earth Fluorides, and Composites

In the past few years, the efforts of scientists in the field of nanoparticle design have focused on building 2D and 3D macroscopic objects from controlled assembly processes. Among the few proposed methods, the preparation of aerogels allows production of 3D monolithic materials of several centimeters in size with desired porosity. The use of nanocrystals as building blocks provides access to highly crystalline macroscopic structures, imitating porous crystals. Herein, a general and versatile approach to aerogels development starting from aqueous colloidal solutions is introduced. A strong and abrupt change of the dielectric constant of the nanoparticle dispersion solvent induces formation of homogeneous and stable gels. The drying of these gels, under supercritical conditions, leads to transparent aerogels. By this approach, Y3Al5O12:Ce and GdF3 monolithic aerogels are prepared for the first time, opening the route to a broad range of chemical compositions with metal oxides and fluorides. Additionally, the method is suitable for composite aerogels with sophisticated structures made of several different nanobuilding blocks.