One-Step Synthesis of Silica@Resorcinol-Formaldehyde Nanospheres and their Application for the Fabrication of Functional Polymer and Carbon Capsules

The synthesis of silica, carbon or polymer nanospheres and capsules has attracted widespread interest because of their potential applications in the fields of drug delivery, catalysis, photonic crystals, biodiagnostic or energy storage. Special attention has been paid to colloidal silica nanospheres of uniform size. These particles are commonly produced by the hydrolysis and condensation of silicon alkoxides (i. e. tetraethyl orthosilicate, TEOS) in a water-ethanol mixture in the presence of ammonia as catalyst (Stöber method). Recently, this simple procedure has been successfully extended to the fabrication of monodisperse polymeric nanospheres of resorcinol–formaldehyde (RF). The numerous similarities between the reaction mechanisms in the synthesis of colloidal silica and resorcinol-formaldehyde, both of which are catalysed by ammonia, foreshadowed the success of this strategy. However, it is worth mentioning one important difference between both processes; i. e. they occur at very different reaction rates. Indeed, whereas the synthesis of Stöber silica particles takes only ~ 1 hour (30 oC), the formation of RF nanospheres occurs slowly and requires long reaction times (~ 24 h at 30 oC). The fact that both processes take place under similar reaction conditions (i. e. reaction medium, temperature and catalyst) but over different time scales immediately suggests that the one-step synthesis of silica-RF nanocomposites is feasible with a rationally designed synthesis scheme. In order to prove this hypothesis, we