In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. It is further classified according to size: In terms of diameter, fine particles cover a range between 100 and 2500 nanometers, while ultrafine particles, on the other hand, are sized between 1 and 100 nanometers. Similarly to ultrafine particles, nanoparticles are sized between 1 and 100 nanometers, though the size limitation can be restricted to two dimensions. Nanoparticles may or may not exhibit size-related intensive properties that differ significantly from those observed in fine particles or bulk materials.
Nanoclusters have at least one dimension between 1 and 10 nanometers and a narrow size distribution. Nanopowders are agglomerates of ultrafine particles, nanoparticles, or nanoclusters. Nanometer sized single crystals, or single-domain ultrafine particles, are often referred to as nanocrystals. The term NanoCrystal® is a registered trademark of Elan Pharma International (EPIL) used in relation to EPIL’s proprietary milling process and nanoparticulate drug formulations.
Nanoparticle research is currently an area of intense scientific research, due to a wide variety of potential applications in biomedical, optical, and electronic fields. The National Nanotechnology Initiative has led to generous public funding for nanoparticle research in the United States.