Characteristic Features of Nanoparticles

What makes the science of the nanoscale genuinely special is that, at such a small scale, different physical laws come to dominate a material's behaviour compared with the laws that govern everyday, human-scale experience. A bulk sample of a given element or compound has essentially fixed physical, optical, thermal, mechanical and electrical properties, more or less independent of exactly how large the bulk sample is; at the nanoscale, by contrast, those same properties become strongly size-dependent, changing measurably as the particle size is varied even while the chemical identity of the substance stays exactly the same. The following six subsections work through this size-dependence property by property: colour (an optical property), surface area (a structural property with knock-on effects for reactivity), catalytic activity, thermal properties (melting point), mechanical properties ( …