Surface‐Initiated Redox Route to Hollow MnO2 Nanostructures

Abstract Nanostructured MnO 2 are gaining great research interest because of their wide applications ranging from optical and electronic devices to energy storage and catalysis. However, the formation of a well‐defined MnO 2 coating on the surface of various colloidal objects has been challenging due to surface incompatibility. Here, we report a unique and robust surface‐initiated redox route to the controlled deposition of MnO 2 on colloidal particles, which can be employed to produce high‐quality hollow MnO 2 nanoshells and a variety of MnO 2 coated nanocomposites. Colloidal resorcinol formaldehyde (RF) resin spheres serve as both reducing agents and sacrificial templates to initiate the controlled deposition of MnO 2 on their surfaces. Further, the RF resin can also be coated on the surface of other colloidal nanostructures to allow overcoating of MnO 2 through the redox reaction and produce nanocomposites such as SiO 2 @MnO 2 and Au@MnO 2 . The size and thickness of the MnO 2 nanoshells can be tuned precisely to induce resonant Mie scattering, leading to bright colorations that can shift reversibly in response to the changes in the refractive index of the surroundings.