Controlling Particle Size and Structural Properties of Mesoporous Silica Nanoparticles Using the Taguchi Method

Abstract

The Taguchi method, a statistical design with an L8 orthogonal array, was adopted to optimize the synthetic conditions of mesoporous silica nanoparticles (MSNs) with respect to particle size and structural properties. The amount of the silica source (i.e., tetraethoxysilane), pH value, and reaction time were selected as significant parameters affecting the size and structural properties of the synthesized MSNs. Particle sizes ranging from 17 to 247 nm were successfully controlled by the Taguchi method, and the statistical data based on experimental results indicated that the pH value of the silica/surfactant precursor solution had a greater influence (57%) on particle size than did reaction time and the TEOS amount (29% and 13%, respectively). The effects of individual parameters on particle size and structural properties, such as surface area and structural ordering, were also investigated by changing one parameter at a time. We concluded that the pH value strongly affected mesostructural ordering and particle size. Longer reaction times in basic conditions had little effect on structural ordering but caused erosion of the MSN silica framework, resulting in smaller particle sizes. The minimum amount of TEOS for ordered MSNs was 5 mL, and more TEOS slightly increased the particle size of the synthesized MSNs. The rational design and systematic investigation of synthetic conditions for MSNs with controllable particle sizes and structural properties presented in this study show great potential for MSN-based catalytic and biomedical applications.