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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.〔(Module 3: Characteristics of Particles – Particle Size Categories ). epa.gov〕 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. Nanoparticle research is currently an area of intense scientific interest 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. ==Definition== ''Note 1'': Modified from definitions of nanoparticle and nanogel in (). ''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 reason for the synonymous definition of nanoparticles and ultrafine particles is that, during the 1970-80s, 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 fashionable (see, for example the same senior author's paper 20 years later addressing the same issue, lognormal distribution of sizes ). Nanoparticles may or may not exhibit size-related properties that differ significantly from those observed in fine particles or bulk materials.〔(ASTM E 2456 – 06 Standard Terminology Relating to Nanotechnology )〕 Although the size of most molecules would fit into the above outline, individual molecules are usually not referred to as nanoparticles. 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「nanoparticle」の詳細全文を読む スポンサード リンク
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