Synthesis of Mono-Dispersed Silicalite-1 Nanocrystals in Water-Surfactant-Organic Solvent

In this paper, we report a method for preparing mono-dispersed silicalite-1 nanocrystals via hydrothermal synthesis in a water-surfactant-organic solvent consisting of a polyoxyethylene (15) oleyl-ether/cyclohexane system. Mono-dispersed silicalite-1 nanocrystals of approximately 60 nm diameter were successfully prepared. It was found that the crystal size depended on both the surfactant concentration and the amount of water solution added to the surfactant-organic solvent. The effects of the surfactant concentration and the amount of water solution on crystal morphology and size were investigated to clarify the mechanism underlying the formation of silicalite-1 nanocrystals in water-surfactant-organic solvent. Since the surfactant coexisted in the synthetic solvent, it was considered that the micellar structure and/or surfactants affected the rates of nucleation and crystal growth of silicalite-1, thus affecting crystal size. Crystal size was controllable within the range of 60 to 1000 nm by changing the W/S values.