Controllable synthesis, growth mechanism, structure and optical properties of ZnO–SiO₂ nanocomposites

ZnO quantum dots (QDs) have been successfully encapsulated in the amorphous SiO₂ matrix by a modified Stöber method. The effects of the sequence of adding the ZnO QDs and tetraethyl orthosilicate (TEOS) and the hydrolysis time of TEOS on the structure, ordered and optical properties of ZnO–SiO₂ nanocomposites were investigated in detail. When the TEOS was added to the solution of ZnO QDs, the QDs were disorderly dispersed within the amorphous SiO₂ matrix. On the other hand, as adding the ZnO QDs to the already hydrolyzed TEOS solution, the self-assembly of ZnO–SiO₂ nanocomposites was observed through a general route of zero-dimensional (0D) → 1D → 3D with the hydrolysis time of TEOS increased. The possible formation mechanisms were schematically illustrated. PL results showed that the PL peak intensity and the position of UV emission were sensitive to the hydrolysis time of TEOS, the luminescence intensity of the UV emission for the ZnO–SiO₂ nanocomposites reached the highest value when t = 6 h. These ZnO–SiO₂ nanocomposites would show a wider application for its particular structure, stability and enhanced emission, such as the conjugation of the nanocrystals to biological entities after functionalization.