Silica encapsulation of quantum dots and metal clusters

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