Silica encapsulation of quantum dots and metal clusters

The use of nanometre thick silica shells as a means to stabilize metal clusters and semiconductor particles is discussed, and its potential advantages over conventional organic capping agents are presented. Shell deposition depends on control of the double layer potential, and requires priming of the core particle surface. Chemical reactions are possible within the core, via diffusion of reactants through the shell layer. Quantum dots can be stabilized against photochemical degradation through silica deposition, whilst retaining strong fluorescence quantum yields and their size dependent optical properties. Ordered 3D and 2D arrays of a macroscopic size with uniform particle spacing can be created. Thin colloid films can also be created with well-defined interparticle spacing, allowing controlled coupling of exciton and surface plasmon modes to be investigated. A number of future core-shell nanocomposite structures are postulated, including quantum bubbles and single electron capacitors based on Au@SiO2.