Deposition of colloidal gold onto supports

Methods for preparing colloidal gold and also bimetallic colloids containing gold have been described in Section 3.2.3. The gold particles may be immobilised on supports by dipping the supports in the colloidal suspension, 

The method is also applicable to making Au/SiC 2, by using a sol derived from an ethanolic solution of Au(PPh3)3Cl reduced by sodium borohydride.106 lwt.% Au/SiC 2 contained particles 2.7nm in size, increased only slightly by calcination at 673 K to eliminate the phosphine ligands. 

Using preformed particles is advantageous because particle size is independently controllable, the size distribution is narrow and the gold already reduced. The mean size can be varied by well-established methods, and thermal post-treatment can be avoided for liquid-phase reactions if the stabiliser is appropriately chosen, and does not cover the particles completely. 

For gas-phase reactions, however, elimination of the stabiliser is recommended, but this may lead to sintering of the particles. 

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