Nano-materials

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Nanomaterials describe, in principle, materials of which a single unit is sized (in at least one dimension) between 1 and 100 nm (the usual definition of nanoscale).

Nanomaterials research takes a materials science-based approach to nanotechnology, leveraging advances in materials metrology and synthesis which have been developed in support of microfabrication research. Materials with structure at the nanoscale often have unique optical, electronic, thermo-physical or mechanical properties.

Nanomaterials are slowly becoming commercialized and beginning to emerge as commodities.

Definition

In ISO/TS 80004, ''nanomaterial'' is defined as the "material with any external dimension in the nanoscale or having internal structure or surface structure in the nanoscale", with ''nanoscale'' defined as the "length range approximately from 1 nm to 100 nm". This includes both ''nano-objects'', which are discrete pieces of material, and ''nanostructured materials'', which have internal or surface structure on the nanoscale; a nanomaterial may be a member of both these categories.

On 18 October 2011, the European Commission adopted the following definition of a nanomaterial: "A natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and for 50% or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm – 100 nm. In specific cases and where warranted by concerns for the environment, health, safety or competitiveness the number size distribution threshold of 50% may be replaced by a threshold between 1% to 50%."

Sources

Engineered

Engineered nanomaterials have been deliberately engineered and manufactured by humans to have certain required properties.

Legacy nanomaterials are those that were in commercial production prior to the development of nanotechnology as incremental advancements over other colloidal or particulate materials. They include carbon black and titanium dioxide nanoparticles.

Incidental

Nanomaterials may be unintentionally produced as a byproduct of mechanical or industrial processes through combustion and vaporization. Sources of incidental nanoparticles include vehicle engine exhausts, smelting, welding fumes, combustion processes from domestic solid fuel heating and cooking. For instance, the class of nanomaterials called fullerenes are generated by burning gas, biomass, and candle. It can also be a byproduct of wear and corrosion products. Incidental atmospheric nanoparticles are often referred to as ultrafine particles, which are unintentionally produced during an intentional operation, and could contribute to air pollution.

Natural

Biological systems often feature natural, functional nanomaterials. The structure of foraminifera (mainly chalk) and viruses (protein, capsid), the wax crystals covering a lotus or nasturtium leaf, spider and spider-mite silk, the blue hue of tarantulas, the "spatulae" on the bottom of gecko feet, some butterfly wing scales, natural colloids ( milk, blood), horny materials ( skin, claws, beaks, feathers, horns, hair), paper, cotton, nacre, corals, and even our own bone matrix are all natural ''organic'' nanomaterials.

Natural ''inorganic'' nanomaterials occur through crystal growth in the diverse chemical conditions of the Earth's crust. For example, clays display complex nanostructures due to anisotropy of their underlying crystal structure, and volcanic activity can give rise to opals, which are an instance of a naturally occurring photonic crystals due to their nanoscale structure. Fires represent particularly complex reactions and can produce pigments, cement, fumed silica etc.

Natural sources of nanoparticles include combustion products forest fires, volcanic ash, ocean spray, and the radioactive decay of radon gas. Natural nanomaterials can also be formed through weathering processes of metal- or anion-containing rocks, as well as at acid mine drainage sites.

;Gallery of natural nanomaterials

File:Kapsid Schema-01.png, Viral capsid
File:Lotoseffekt.jpg, " Lotus effect", hydrophobic effect with self-cleaning ability
File:Gecko foot on glass.JPG, Close-up of the underside of a gecko's foot as it walks on a glass wall (spatula: 200 × 10-15 nm)
File:SEM image of a Peacock wing, slant view 4.JPG, SEM micrograph of a butterfly wing scale (× 5000)
File:Trevarno, pavo cristatus06.jpg, Peacock feather (detail)
File:62cts Brazilian Crystal Opal.JPG, Brazilian Crystal Opal. The play of color is caused by the interference and diffraction of light between silica spheres (150 - 300 nm in diameter).
File:Lasiodora parahybana, claws.JPG, Blue hue of a species of tarantula (450 nm ± 20 nm)

Types

Nano-objects are often categorized as to how many of their dimensions fall in the nanoscale. A '' nanoparticle'' is defined a nano-object with all three external dimensions in the nanoscale, whose longest and the shortest axes do not differ significantly. A '' nanofiber'' has two external dimensions in the nanoscale, with ''nanotubes'' being hollow nanofibers and ''nanorods'' being solid nanofibers. A ''nanoplate/nanosheet'' has one external dimension in the nanoscale, and if the two larger dimensions are significantly different it is called a ''nanoribbon