Our Core-shell materials are prepared by modifying the production of the Hollow silica shells through the addition of a metal salt. The result is an outer silica shell that encapsulates inner layers of the chosen metal, usually in the form of a metal oxide (if thermal removal of the template bead is performed in air).

The following images show both the outside and cross-sectional slices of an encapsulated iron(III) oxide sample. The image to the far right is a transmission image of encapsulated silver indicating that metals introduced at lower levels form smaller particulates on the inside of the Hollow silica shells.

The following image shows both the metals in the periodic table that have been examined in this manner and also the resultant colours produced. For this, all thermal treatment was performed in air so the encapsulated compounds are primarily oxides, chlorides and oxychlorides.

If the right mixture of metal salts is introduced to the reaction mixture in the production of a core-shell material then multi-component products are possible. For example, the following image shows yttrium vanadate doped with 2% europium, under both normal and ultraviolet light (inset). This mixture was prepared from adding yttrium oxide, ammonium vanadate and europium oxide in appropriate stoichiometric amounts.

Encapsulation inside the silica shells can alter not only the appearance but also the physical properties of the entrapped material. For example, copper oxide results as a white product instead of the usual black, while zinc oxide is produced with a brown colouration instead of white.

Please contact us if you wish to enquire more about the use of Exilica’s Core-shell materials.

Please note: Core-shell materials are made to order, Exilica does not keep a stock of each metal option.

Publications:

Shakiela Begum, Ian P. Jones, Chengge Jiao, Daniel E. Lynch and Jon A. Preece, “Characterisation of hollow Russian doll microspheres”, J. Mater. Sci., 2010, 45, 3697-3706.