Nanoscience

Nanoscience is the study of structures and materials on the scale of nanometres -- 'nano' means one-billionth of a metre, i.e. $10^{-9}\,\text{m}$. When ordinary (bulk) matter is divided down into objects this small, its mechanical, electrical, optical, magnetic and other physical properties change, often dramatically, compared to the same substance in bulk.

Nanotechnology is the technology built on this science: the design, production, characterization and application of nano-structured materials.

Nanoparticles. All solids are made of particles, each containing some definite number of atoms that varies from material to material. A solid whose particle size is less than $100\,\text{nm}$ is called a nano solid; once particle size exceeds $100\,\text{nm}$ it is a bulk solid. Crucially, a nano solid and its bulk counterpart can share the exact same chemical composition -- zinc oxide (ZnO), for instance, exists in both bulk and nano form -- yet the nano form shows strikingly different physical properties from the bulk form, purely because of its reduced size, not any change in chemistry. …