Bound Nanoparticle: An engineered particle “dispersed and fixed within a polymer matrix, incapable as a practical matter of becoming airborne” is BOUND.
Unbound Nanoscale Particle (UNP): Not contained within a matrix under normal temperature and pressure conditions that would reasonably be expected to prevent the particles from being separately mobile. Examples of UNP include intentionally produced fullerenes, nanotubes, nanowires, nanoropes, nanoribbons, quantum dots, nanoscale metal oxides, nanoplates, nanolayers, and other engineered nanoscale particles.