view article
Figure 4
Self-transformation of a solid microsphere (made of highly monodisperse size nanoparticles) into a core-shell structure. (a) Formation of a solid microsphere made from highly monodisperse size nanoparticles of high Gibbs free energy. The color of the nanoparticles refers to their Gibbs free energy (G) with, for simplicity, three levels: red (high G), orange (medium G) and blue (low G). (b) Formation of a multilayered shell shown in orange. The outermost layers are more stable due to their larger nanoparticles. The innermost layers are more stable due to their lower interfacial free energy. The higher thickness of the contour of the nanoparticles refers to a higher PSS coverage corresponding to a lower interfacial free energy. In the core, the largest nanoparticles continue to grow by Ostwald ripening. (c) Progressive dissolution of the core forming a core-shell structure. (d) Formation of an almost-hollow microsphere. The presence of nanoparticles in the core results from the growth of the largest nanoparticles of the initial solid microspheres. With full size monodispersity of the nanoparticles in the initial solid microsphere, the final structure would be completely hollow.

IUCrJ
Volume 9| Part 5| September 2022| Pages 580-593
ISSN: 2052-2525
https://doi.org/10.1107/S2052252522006108