Definition of Nanotechnology
Nanotechnology is the general term for designing and making anything whose use depends on specific structure at the nanoscale-generally taken as being 100 nanometres (100 millionths of a millimetre or 100 billionths of a metre) or less. It includes dvices or systems made by manipulating individual atoms or molecules, as well as materials which contain very small structures. Nanomaterials are usually considered to be materials with at least one external dimension that measures 100 nanometres or less or with internal structures measuring 100 nm or less. They may be in the form of particles, tubes, rods or fibres.
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 incudes bothnano-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.
Sources
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 “spatula” 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, claysdisplay 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 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.
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 has one external dimension in the nanoscale, and if the two larger dimensions are significantly different it is called a nanoribbon . For nanofibers and nanoplates, the other dimensions may or may not be in the nanoscale, but must be significantly larger. Nanostructured materials are often categorized by what phases of matter they contain.
A nanocomposite is a solid containing at least one physically or chemically distinct region, or collection of regions, having at least one dimension in the nanoscale. A nanofoam has a liquid or solid matrix, filled with a gaseous phase, where one of the two phases has dimensions on the nanoscale. A nanoporous material is a solid material containing nanopores , cavities with dimensions on the nanoscale.
Applications
Nano materials are used in a variety of, manufacturing processes, products and healthcare including paints, filters, insulation and lubricant additives. In healthcare Nanozymes are nanomaterials with enzyme-like characteristics. They are an emerging type of artificial enzyme , which have been used for wide applications in such as biosensing, bioimaging, tumor diagnosis, antibiofouling and more. In paints nanomaterials are used to improve UV protection and improve ease of cleaning. In the air purification field, nano technology was used to combat the spread of MERS in Saudi Arabian hospitals in 2012. Nanomaterials are being used in modern and human-safe insulation technologies. As a lubricant additive, nano materials have the ability to reduce friction in moving parts. Worn and corroded parts can be repaired with self-assembling anisotrpic nanoparticles called TriboTEX. Nanomaterials can also bu used in three-way-catalyst (TWC)applications.TWC converters have the advantage of controlling the emission of nitrogen oxides (NOX), which are precursors to acid rain and smog. In core-shell structure, nanomaterials form shell as the catalyst support to protect the noble metals such as palladiu rhodium. The primary function is that the supports can be used for carrying catalysts active components, making them highly dispersed, reducing the use of noble metals, enhancing catalysts activity, and improving the mechanical strength.
NEWS
JULY 16,2019
UT Research Team Develops Technique to Study How Nanomaterials Form
A new form of electron microscopy allows researchers to examine nano-scale tubular materials while they are “alive” and forming liquids—a first in the field.
Developed by a multidisciplinary team at the University of Tennessee, Knoxville, and Northwestern University, the new technique, called variable temperature liquid-phase transmission electron microscopy (VT-LPTEM), allows researchers to investigate these dynamic, sensitive materials with high resolution. With this information, researchers can better understand how nano-materials grow, form, and evolve.
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