At nanoscale dimensions the properties of materials no longer depend solely on composition and structure in the usual sense. Nanomaterials display new phenomena associated with quantized effects and with the preponderance of surfaces and interfaces.
Quantized effects arise in the nanometre regime because the overall dimensions of objects are comparable to the characteristic wavelength for fundamental excitations in materials. For example, electron wave functions (see also de Broglie wave) in semiconductors are typically on the order of 10 to 100 nanometres. Such excitations include the wavelength of electrons, photons, phonons, and magnons, to name a few. These excitations carry the quanta of energy through materials and thus determine the dynamics of their propagation and transformation from one form to another. When the size of structures is comparable to the quanta themselves, it influences how these excitations move through and interact in the material. Small structures may limit flow, create wave interference effects, and otherwise bring into play quantum mechanical selection rules not apparent at larger dimensions.
Examples-from-biological-and-mechanical-realms-illustrate-various-orders-ofExamples from biological and mechanical realms illustrate various “orders of magnitude” …[Credits : Encyclopædia Britannica, Inc.]
The-structure-of-buckminsterfullereneThe structure of buckminsterfullerene (C60).[Credits : Encyclopædia Britannica, Inc.]
Top-down-approaches-have-been-developed-for-building-structures-atTop-down approaches have been developed for building structures at the scale of the micrometre …[Credits : Encyclopædia Britannica, Inc.]
Phospholipid-molecules-composed-of-fatty-acid-tails-and-a-phosphatePhospholipid molecules, composed of fatty acid “tails” and a phosphate …[Credits : Encyclopædia Britannica, Inc.]
Coherent-X-ray-diffraction-patterns-such-as-the-one-shownCoherent X-ray diffraction patterns, such as the one shown here of a nanosized metal cube, can be …[Credits : Reprinted by permission from Macmillan Publishers Ltd.; Nature, July 6, 2006, vol. 442, …]
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