Size and Scale
Nanotechnology usually deals with the research and development of molecular particles, devices and composites between approximately one and 100 nanometres. A nanometre is one billionth of a metre.
To gain a greater appreciation of the size and scale of matter involved in nanotechnology, a sheet of paper is about 100,000 nanometres thick, while a strand of human hair is anywhere between 15,000 and 180,000 nanometres wide--depending on its colour. Black hair tends to be thicker than blond hair.
Nanotechnology, therefore, involves substances at the molecular and atomic levels--levels at which human DNA is two nanometres wide and a hydrogen atom is 0.1 nanometres in size.
At this minute scale, elements and materials can have different properties than they would have at a much larger scale. For instance, nanoparticles of gold and silver have a colour, melting point and chemical properties that are different from much larger samples of gold or silver. Important changes in behavior are caused not only by continuous modification of characteristics with diminishing size, but also by the emergence of totally new phenomena such as quantum confinement. A typical example of a new phenomenon seen at the nanoscale would be the colours emitted from semiconductor nanoparticles, which change depending on its size.
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