With a reduction of their size, nanoparticles reveal unique properties. A size reduction results in a substantial increase in the specific surface and the surface Gibbs free energy. This physical parameter of free energy reflects the fact that chemical reactivity increases rapidly as particle size diminishes. For example, water has a specific surface of m2 /g at a diameter of one millimetre but the surface expands to m2 /g at a diameter of one nanometre. Surface energy also rises by a factor of one million as size decreases from millimetres to nanometres (Zhao and Nalwa, 2007c). This means.
