Scalable fabrication of uniform microparticles with highly ordered mesoporous structures

Mesoporous silica is a versatile material with controllable pore size and ease of functionalization, enabling them to be employed in a vast range of applications, such as catalysis, adsorption, and drug delivery. A common method to produce mesoporous silica is via a wet chemistry route involving multiple steps, frequently with organic solvents, while producing relatively small amounts of (often polydisperse) nanoparticles. Spray drying offers a faster, easily scalable route of production without waste. The use of a micro-fluidic jet spray dryer developed at Monash University enables the production of monodisperse microparticles in larger quantities compared to wet synthesis methods. Here, a combination of surfactant templated and evaporation induced self-assembly provides the ability to control the pore size and the particle size of mesoporous microparticles produced. A protocol to assemble these particles was developed with their properties characterized via TEM, SEM, XRD, and nitrogen adsorption. The microparticles demonstrated highly ordered hexagonal mesostructures with high surface areas and pore volumes closely approaching those of mesoporous nanoparticles. The increase in surfactant to silica ratio resulted in increasing surface area and pore volume, provided that the concentration of surfactant was sufficient for the self-organisation of surfactant-silica micelles, while particle size could be controlled by varying the initial solute content in the precursor. This work contributed towards the understanding of formation mechanisms and effects of process parameters on the synthesis of mesoporous materials via the spray drying approach. The knowledge is useful in enabling a rapid and scalable process for the production of functional particles for a wide range of applications.