Important nanomaterials

Quantum dots with emission maxima shifted by 10 nm each. Image provided by PlasmaChem
Quantum dots with emission maxima shifted by 10 nm each. Image provided by PlasmaChem

In the following section, some important nanomaterials are presented:

Nano silver: Nano silver (usually in the form of silver nanoparticles) is mainly used for its antimicrobial properties. There are numerous examples of applications as medical products like wound dressings or surface coatings. An example for consumer products are silver nanoparticles that are used in textiles for preventing odors        (T-shirts, socks, etc.).

Soot (carbon black): Carbon black is the nanomaterial which is produced in largest quantities for industrial applications. Carbon black is applied in car tires, where the added particles optimize the rolling resistance or reduce abrasion. Carbon black is also used as a black pigment in paints, lacquers and cosmetics or as an antistatic additive in plastics.

Carbon nanotubes (CNT): tiny tubes, which are composed of carbon atoms. One differentiates between single-walled (SWCNT) and multi-walled (MWCNT) carbon nanotubes. CNTs are extremely stable. Therefore, they may be incorporated in plastic matrices in order to improve their mechanical properties. CNTs are also applied in various sports equipment (bicycle frames, tennis rackets). Research in the field of electronics will be carried out in the future.

Animation of a single-walled CNT © Schwarzm, Wikimedia Commons
Animation of a single-walled CNT © Schwarzm, Wikimedia Commons

Titanium dioxide (TiO2): nanoscale titanium dioxide is the most commonly used metal oxide. Titanium dioxide is photocatalytic, i.e. it can accelerate the decomposition of organic materials with sunlight (UV radiation). If the particles are incorporated into facade paints, they ensure that the facades remain clean. In cosmetic products, coated titanium dioxide nanoparticles are used as filters against harmful UVA and UVB rays.

Zinc oxide (ZnO): ZnO nanoparticles absorb UV radiation from the sun very efficiently and are also used in cosmetic products. ZnO is a direct semiconductor and is used as a transparent conductive layer in light emitting diodes (LEDs) or liquid crystal displays (LCDs). Nanometer-thin zinc oxide coatings are used in solar cells.

Silicon dioxide (SiO2): silica nanoparticles are added to surface coatings and paints and serve to increase hardness and scratch resistance. As a filler in car tires, they reduce the rolling resistance and thus reduce fuel consumption. Amorphous SiO2 particles have been used for decades as a food additive (E551) to prevent the agglomeration of powders (salt, seasoning etc.). In this application, the SiO2 particles are present as nanostructured agglomerates and not as "free" nanoparticles. The size of agglomerates is in the micrometer range.

Graphene: honeycomb, two-dimensional modification of carbon. Graphene is extremely tensile, stable, electrically conductive and also stretchable. Applications in transistors and solar cells are the subject of current research.

Fullerenes: consist of carbon and are spherical. The most famous fullerene is the Buckminsterfullerene (“Buckyball”), which consists of 60 carbon atoms and looks like a football. Various applications of fullerenes (e.g. as radical scavengers in cosmetic products) are currently under investigation.

Quantum dots: Quantum dots refer to a few nanometer-small nanocrystals, which exhibit quantum effects. They usually consist of semiconducting materials. Quantum dots can be used in transistors, displays or as biomarkers.