Graphene oxide–silica hybrid capsules for sustained fragrance release

Encapsulation of active or valuable cargoes has become one of the most important methods for controlled delivery and release. However, many existing capsule technologies suffer from scalability issues, and capsules from surfactant- or polymer-stabilised emulsions tend to have weak shells or limited stability. Here we present a robust and scalable method for the surfactant-free preparation of silica hybrid capsules templated from Pickering emulsions stabilised by graphene oxide. These capsules are produced using a single step, undemanding formulation process with cheap and scalable precursors. The mechanical and chemical stability provided by the silica shell grown around these droplets is explored using surface pressure measurements and atomic force microscopy, demonstrating that a rigid and robust capsule is produced from higher loadings of silica precursor. In order to demonstrate the utility of these capsules, the sustained release of a fragrance molecule (vanillin) from the capsules is monitored, and compared to release from unencapsulated vanilla oil. It is seen that the capsules retain the fragrance for multiple weeks, offering new pathways for scalable encapsulation systems for the delivery of valuable actives.