Nanoparticle
Nanoparticles are particles between 1 and 100 nanometers in size. In nanotechnology, a particle is defined as a small object that behaves as a whole unit with respect to its transport and properties. Particles are further classified according to diameter. Ultrafine particles are the same as nanoparticles and between 1 and 100 nanometers in size, fine particles are sized between 100 and 2,500 nanometers, and coarse particles cover a range between 2,500 and 10,000 nanometers. Scientific research on nanoparticles is intense as they have many potential applications in medicine, physics, optics, and electronics. The U.S. National Nanotechnology Initiative offers government funding focused on nanoparticle research.
Particle of any shape with dimensions in the 1 × 10−9 and 1 × 10−7 m range.
Note 1: Modified from definitions of nanoparticle and nanogel in [refs.,].
Note 2: The basis of the 100-nm limit is the fact that novel properties that
differentiate particles from the bulk material typically develop at a critical
length scale of under 100 nm.
Note 3: Because other phenomena (transparency or turbidity, ultrafiltration,
stable dispersion, etc.) that extend the upper limit are occasionally considered,
the use of the prefix nano is accepted for dimensions smaller than 500 nm,
provided reference to the definition is indicated.
Note 4: Tubes and fibers with only two dimensions below 100 nm are also
nanoparticles.
The term "nanoparticle" is not usually applied to individual molecules; it usually refers to inorganic materials.
The reason for the synonymous definition of nanoparticles and ultrafine particles is that, during the 1970s and 80s, when the first thorough fundamental studies with "nanoparticles" were underway in the USA (by Granqvist and Buhrman) and Japan, (within an ERATO Project) they were called "ultrafine particles" (UFP). However, during the 1990s before the National Nanotechnology Initiative was launched in the USA, the new name, "nanoparticle," had become more common (for example, see the same senior author's paper 20 years later addressing the same issue, lognormal distribution of sizes ). Nanoparticles can exhibit size-related properties significantly different from those of either fine particles or bulk materials.
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