AuSiO2

AuSiO2 refers to composite materials that combine gold nanoparticles with a silica (SiO2) component. The most common form is a gold core with a silica shell (often written as Au@SiO2), which is sometimes collectively described as AuSiO2 core–shell nanoparticles. Another form is gold nanoparticles embedded within a mesoporous silica shell (Au@MSN), or gold particles dispersed in a silica matrix.

Synthesis typically starts with colloidal gold nanoparticles produced by citrate reduction or similar methods. A silica shell is then grown by hydrolyzing tetraethyl orthosilicate (TEOS) in a water-alcohol-ammonia solution, using the gold particles as seeds. Alternative approaches include microemulsion or templated sol–gel processes. Shell thickness is controlled by TEOS concentration, catalyst amount, and reaction time, allowing tuning of optical and diffusion properties.

The silica coating provides several advantages. It enhances colloidal stability and prevents aggregation, especially in complex media. Silica offers abundant surface silanol groups for chemical functionalization with silane chemistry, enabling attachment of polymers, antibodies, dyes, or drugs. The gold core maintains localized surface plasmon resonance (LSPR), which can be leveraged for enhanced optical sensing, imaging, and photothermal therapy. The shell also modulates the plasmonic coupling and protects the core from chemical damage or environmental fluctuations.

Applications span biosensing, diagnostic imaging, targeted drug delivery, photothermal therapy, and catalysis. Mesoporous silica shells enable drug loading and controlled release, while core–shell configurations can combine imaging and therapeutic modalities. Variants include hollow silica shells, multilayer shells, and gold nanoparticles embedded in silica matrices.