Determine apparent shell density for evaluation of hollow silica nanoparticle

To maximize excellent property of hollow nanoparticles, it is important to determine physical property of shell because it directly affects functionality of the final product. In this study, hollow silica nanoparticles (HSNPs) with different shell structure were prepared based on sol–gel reaction using polystyrene (PS) beads template. As physical property, apparent shell density was determined using specific surface area and shell thickness. The obtained HSNPs were categorized into three types of (A) thickness of silica shell is relatively thin and spherical shape of the stacked particulates is clearly identified in the shell, (B) thickness of silica shell is similarly thin to type A, but shape of the stacked particulates is identified as half-round shape, and (C) thickness of silica shell is thick and the stacked particulates are not recognized in the shell, which were controlled by suspension pH and reaction time. Apparent shell density of types A, B, C appeared in the 1.4–2.2 g/cm3 and it increased with increase in pH and/or reaction time. This must be useful technique to design hollow silica nanoparticles.