Silicashelled

Silicashelled, often written as silica-shelled, refers to materials in which a silica (SiO2) shell surrounds a core particle, forming a core–shell architecture. The core can be inorganic, organic, or hybrid, and the silica layer provides a protective, chemically versatile outer surface.

Synthesis of silicashelled structures commonly employs sol-gel chemistry. A typical route involves coating preformed core particles with silica by hydrolyzing and condensing tetraethyl orthosilicate (TEOS) in alcohol-water–ammonia or ammonium hydroxide media (the Stöber process and its variants). The shell thickness and uniformity can be tuned by adjusting the TEOS amount, reaction time, and core surface chemistry. Mesoporous silica shells (MSS) are created by templating with structure-directing agents such as CTAB, followed by template removal to yield porous shells that enhance cargo loading and diffusion. Other methods include layer-by-layer deposition and direct synthesis on functionalized cores.

Key properties of silicashelled particles include chemical and mechanical stability, biocompatibility of silica, and a readily functionalizable surface through silanol groups. The shell can be dense or porous, influencing permeability and protection of the core, and surface silanization enables attachment of a wide range of functional groups and biomolecules for targeting, imaging, or catalysis.

Applications span drug delivery, bioimaging and diagnostics, catalysis, sensing, and protective coatings. In practice, silica shells protect sensitive cores (such as quantum dots or enzymes) and enable surface modification without compromising core functionality. Considerations include diffusion through thick shells, potential aggregation, and safety assessments for biomedical use.

See also: silica, core–shell nanoparticles, Stöber process, mesoporous silica.