Facile and generalized encapsulations of inorganic nanocrystals with nitrogen-doped carbonaceous coating for multifunctionality

A simple strategy toward versatile encapsulations of inorganic nanocrystals, through a green hydrothermal treatment of commercial polyurethane sponge, was developed. This approach enables us to realize a general method to form a surface-adherent, N-doped coating with a controllable thickness for well-defined structures. These composites exhibit active properties in optical applications and energy storage. For example, N-doped carbon encapsulated Fe₂O₃ nanoboxes show a very high discharge capacity and outstanding cyclability, and the capacity still remained at 1086 mA h g^-1 at a current density of 400 mA g^-1 after 200 cycles. Our results described here provide a simple surface coating technique to design various functional nanostructures.