Discovered by Ugarte in 1992, carbon nano-onions are multilayer fullerenes belonging to the family of carbon allotropes which include diamond, graphite, graphene and carbon nanotubes. They are composed of increasing concentric graphitic layers. Carbon nano-onions have a variety of unique characteristics, such as high surface area to volume ratio, low density and multilayer morphology. These properties have rendered them potentially useful macromolecules in many areas of science. Our research focused on functionalizing the surface of carbon nano-onions with a spiropyran derivative. A spiropyran is a molecule that undergoes reversible transformations as a response to external stimulation. Upon ultraviolet irradiation it converts to the zwitterionic merocyanine form and may complex metal cations like Zn²⁺. Upon exposure to visible light, the Zn²⁺ is released and the molecule reverts back to the spiropyran form. We combine the two moieties to take advantage of their respective properties and to explore the potential for applications in molecular sensing and light activated delivery of small metal ions.