Shell-thickness control of hollow SiO2 nanoparticles through post-treatment using sol–gel technique toward efficient water confinement

Abstract

Hollow structures possess a confinement function, which enables the handling and use of functional liquids. In this study, we focus on the confinement of water in the inner spaces of hollow SiO 2 nanoparticles (HSNPs). Water is introduced into the hollow spaces passing through the mesopores of the shells. The introduced water is then confined by thickening the shell through a post-treatment using silicon alkoxides. HSNPs with a variety of shell thicknesses are prepared by tuning the synthetic conditions of the reaction media and the alkoxides. It is found that the amount of water retained in a hollow space is increased with shell thickness. The resultant water–HSNP nanocomposites exhibit effective far-infrared absorption. The facile confinement approach reported in this study will lead to highly functional complex nanocomposites, such as isolated metal nanoparticles–water–silica.