Mechanistic Insight into the Yolk@Shell Transformation of MnO@Silica Nanospheres Incorporating Ni2+ Ions toward a Colloidal Hollow Nanoreactor



As an effort to develop a simple and versatile synthetic strategy that contributes to the evolution of hollow nanostructures with increasing complexity and functionality, this research is devoted to study the hollow transformation within a nanosized solid matrix. Through an in-depth investigation of a hollowing process of MnO nanocrystals confined within a Ni2+ incorporating silica nanosphere, a very distinct transformation pathway can be explained that produces the yolk@shell nanostructure with a single Ni nanocrystal inside a silicate nanoshell. The yolk@shell structure is developed by a mechanism combining different processes, including the formation of a (Ni0.1Mn0.9)O mixed-metal oxide and subsequent segregation of the reduced Ni. Furthermore, this study also devises a protocol to exploit the solid-state-synthesized powder for fabricating a colloidal hollow nanoreactor that can selectively catalyze the reduction of nitroarenes and be recycled via the magnetic process.