Nanoparticles are now being used in the manufacture of scratchproof eyeglasses, crack- resistant paints, anti-graffiti coatings for walls, transparent sunscreens, stain-repellent fabrics, self-cleaning windows and ceramic coatings for solar cells. Nanoparticles can contribute to stronger, lighter, cleaner and “smarter” surfaces and systems. At the nanoscale, the properties of particles may change in unpredictable ways. Nanoparticles of titanium oxide used in sunscreens, for example, have the same chemical composition as the larger white titanium oxide particles used in conventional products for decades, but nanoscale titanium oxide is transparent. Antimony - tin oxide provides another example since nanoparticles of this oxide are incorporated into a coating to provide scratch- resistance and offer transparent protection from ultra-violet radiation, not seen with larger size particles.
There are several safety concerns in the automotive sector relating to nanotechnology. Nanoparticles as fillers in tyres can improve adhesion to the road, reducing the stopping distance in wet conditions. The stiffness of the car body can be improved by use of nanoparticle-strengthened steels. New sol-gel deposition methods make it possible to apply, economically, nanometre thick antireflection layers of silicon dioxide or other materials onto displays or panes. Ultra-thin transparent layers on a silver base can be used for heatable, and therefore mist and ice-free, window panes. Transparent and light materials could substitute car body parts that reduce all-round vision at the moment. (Nanoforum Report 2004)
Nanotechnology can be applied in the production, processing, safety and packaging of food. It is possible that nanotechnology will allow the manipulation of the molecular forms of food to provide more capability, lower costs and greater sustainability than at present. A nanocomposite coating process should improve food packaging by placing anti-microbial agents directly on the surface of the coated film and could increase or decrease gas permeability as required for different products. They can also improve the mechanical and heat-resistance properties and lower the oxygen transmission rate. It should also be possible to apply nanotechnology to the detection of chemical and biological substances for sensing biochemical changes in foods, extending to the whole food chain in the future (Nanoforum Report 2004).
As reviewed by Salata (2004), nanomaterials are also being used in biology and medicine in a wide variety of ways, including the direct application of products into patients. Examples include products for drug delivery and gene therapy, the separation and purification of biological molecules and cells, fluorescent biological labels, imaging contrast agents, tissue engineering, DNA probes and nanoscale biochips, and microsurgical technology.
Inhaled nanoparticles may represent a potential health risk. Aerosols in workplace environments may be derived from a wide variety of sources, depending on the type of activity and processes taking place. Nanoparticle aerosols arising from mechanical processes (e.g. the breaking or fracture of solid or liquid material) are unlikely to be formed. Grinding and surface finishing typically releases micrometre and submicrometre particles, possibly down to 100 nm but rarely below this. Most plasma and laser deposition and aerosol processes are performed in evacuated or at least closed reaction chambers. Therefore exposure to nanoparticles is more likely to happen after the manufacturing process itself, except in those cases of failures during the processing (Luther 2004). In processes involving high pressure (e.g. supercritical fluid techniques), or with high energy mechanical forces, particle release could occur in the case of failure of sealing of the reactor or the mills. Nanoparticles exhibit increased diffusivity with decreasing size and therefore show delayed sedimentation in the earth’s gravitational field, which translates into potentially increased lifetimes for nanoparticulate impurities at low concentration. In the presence of larger microparticles, as with the wide size distribution in aerosols such as smoke, the highly diffusive character of nanoparticles may lead to faster agglomeration or impaction on the larger particles. Furthermore, many particles, including metallic particles, are highly pyrophoric and there is a considerable risk of dust explosions.