A Possible universal definition for the nanophase
  A possible universal definition for a nanostructured material based purely on experimental data available in literature for a wide variety of physical phenomena is proposed. It is suggested that for values of the ratio of sample volume, V to that of the unit cell volume, Vc, 10^5- 10^6 the samples behave as nanostructures. This is mirrored in the ratio of the number of particles in sample, N to that in the unit cell, Nc. It is further proposed that the transition to the nanophase from bulk is a phase transition in all cases investigated. The nanophase should therefore be treated as a distinct phase of matter, entirely in the quantum mechanical domain, and treated appropriately. 
M. Ghanashyam Krishna, M. Durga Prasad and V. Srinivasan