Preparation of mesoporous silica nanoparticles by spray drying

Abstract

Mesoporous silica nanoparticles (MSNs) are usually obtained by conventional sol-gel synthesis techniques, in a process that requires long reaction periods, and goes through many critical steps. Small variation in the synthesis conditions can modify the morphology, structural and textural properties of materials. An alternative route for silica nanoparticles manufacturing is the spray drying (SD) technique, which involves particle formation by evaporation-induced hydrolysis and condensation of silicates, also providing continuous production. In this context, we have developed a new SD-based methodology for the preparation of well-dispersed MSNs by properly adjusting the pH of the synthesis mixture (e.g., pH = 8.5), and using NaF as silica mobilizing agent. These nanoparticles present wormhole-like pores that are randomly distributed in all directions and hexagonal symmetry easily recognizable in the mesoporous wall at small domains. In addition, optimizing the gas inlet temperature (T_in) to 90 °C promoted rapid assembly between silicate network building species during the SD process, yielding nanoparticles with good structural and textural properties. This technique is highly scalable and adaptable to the industrial stage, showing enormous interest in the pharmaceutical development.