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3.3 Nanoscience and Nanotechnology
3.3.1 Introduction
Current knowledge of science at the nanometre scale is derived from many disciplines, originating with the atomic and molecular concepts in chemistry and physics, and then incorporating molecular life sciences, medicine and engineering. The observation and understanding of atomic and molecular behaviour from first principles was followed by the increasing ability to control and selectively modify properties of ever smaller pieces of matter in a functional way. Early examples here are the discoveries in self assembly (Bain et al 1989) which culminated in current synthetic and supra-molecular chemistry (Lehn 1988, Gomez –Lopez et al 1996), the increasing knowledge about life’s replication processes and the co-evolution of physical (Perutz et al 1960, Aue et al 1976, Wuthrich 1995) and chemical methodologies. These have resulted in the portfolio of current molecular life sciences such as molecular motors and other functional entities (Mavroidis et al 2004, Clark et al 2004), including biomolecular and medical engineering and the emerging area of systems biology. On the other hand, man made micro and nanoscale sensing devices originate from other domains in microscopy and device engineering but relate to biomedical applications (Ziegler 2004, Emerich and Thanos 2003).
The deviation of surface and interface properties from the bulk properties of larger amounts of materials led to the sometimes unexpected significance of surface effects, including catalytic activity and wetting behaviour in material composed of nanosized entities, such as nanoparticles, composites and colloids (Kamat 2002, Schwerdtfeger 2003). Quantum mechanical principles manifest themselves in the properties of surfaces of clusters of very small particles, especially those of the order of 1000 atoms or molecules and less. Composite materials (Komarneni 1992, Schmidt 2000, Hadjipanayis 1999), with increasingly smaller characteristic sizes of the domains or phases, allowed for the design of materials with new and optimised physical and / or chemical properties. In electronic engineering, the miniaturization of devices has progressed well into the nanometre range with gate oxides in devices being routinely 25 nm thick. The recently increased public awareness of nanoscience is closely related to the availability of first real space images of atomic and molecular processes at surfaces through the invention of Scanning Probe Microscopies (Binnig and Rohrer 1985).
With the continuous development of nanotechnology, the possibility for the bottom-up production of nanoscale materials may result in some kind of self assembly of structures similar to the self assembly of phospholipid bilayers that resembles cellular membranes.
On the basis of current knowledge however, the spontaneous formation of artificial living systems through self assembly and related processes, suggested by some prominent commentators, is considered highly improbable. The combination of self replication with self perpetuation in an engineered nanosystem is extremely difficult to realize on the basis of current scientific knowledge.
3.3.2 Examples of Engineered Nanostructures and Materials and Their Applications
There are several areas of science and technology in which nanoscale structures are under active development or already in practical use.
In materials science, nanocomposites with nanoscale dispersed phases and nanocrystalline materials in which the very fine grain size affords quite different mechanical properties to conventional microstructures are already in use. In surface science and surface engineering, nanotopographies offer substantially different properties related to adhesion, tribology, optics and electronic behaviour. Supramolecular chemistry and catalysis have led to novel surface and size dependent chemistry, such as enantioselective catalysis at surfaces. In biological sciences, fundamental understanding of molecular motors and molecular functional entities on the nanometre scale has been responsible for advances in drug design and targeting. Nanoscale functionalised entities and devices are in development for analytical and instrumental applications in biology and medicine, including tissue engineering and imaging.
The application areas in which these advances in nanoscience are making their biggest impact include electronic, electro-optic and optical devices. The transition from semiconductor (conventional and organic) technology to nanoscale devices has anticipated improved properties and resolution, e.g. fluorescence labelling, scanning probe microscopy and confocal microscopy. Data storage devices based on nanostructures provide smaller, faster, and lower consumption systems.
In medicine, greater understanding of the origin of diseases on the nanometre scale is being derived, and drug delivery through functionalised nanostructures may result in improved pharmacokinetic and targeting properties.
A wide variety of functional nanoscale materials and functional nanoscale surfaces are in use in consumer products, including cosmetics and sunscreens, fibres and textiles, dyes, fillers, paints, emulsions and colloids.
Source & ©: SCENIHR 
3.3 Nanoscience and Nanotechnology, p. 11
3.3.4 Nanoscale materials properties
Material properties depend on structure and composition, and can typically be engineered or modified by changing the relative influence of interfacial or interphase properties and the macroscopic bulk properties through the characteristic size or dimension of components and domains. This approach had already emerged centuries ago with steel alloys and has been so powerful that many engineering materials today are composites with micro to nanoscale domain sizes. Depending on the physical or chemical character of each domain, there is a complex interrelation between the structure and the composition of the material, which may relate to the bulk and surface properties of each ingredient and newly emerging properties localized at the interface. Selective chemical reactivity is quite common with nanocomposites, which gives the potential for disintegration of the material into one or the other component. Complex processes govern this behaviour, which clearly relates to nanoparticle release into the environment.
3.3.5 Conclusions.
The exploitation of the properties associated with the nanoscale is based on a small number of discrete differences between features of the nanoscale and those of more conventional sizes, namely the markedly increased surface area of nanoparticles compared to larger particles of the same volume or mass, and also quantum effects. Questions naturally arise as to whether these features pose any inherent threats to humans and the environment. Bearing in mind that naturally occurring processes, such as volcanoes and fires, in the environment have been generating nanoparticles and other nanostructures for a very long time, it would appear that there is no intrinsic risk associated with the nanoscale per se for the population as a whole. As noted above, there is also no reason to believe that processes of self assembly, which are scientifically very important for the generation of nanoscale structures, could lead to uncontrolled self perpetuation. The real issues facing the assessment of risks associated with the nanoscale are largely concerned with the increased exposure levels, of both humans and environmental species, now that engineered nanostructures are being manufactured and generated in larger and larger amounts, in the new materials that are being so generated, and the potentially new routes by which exposure may occur with the current and anticipated applications.
Source & ©: SCENIHR
3.3.4 Nanoscale materials properties, p. 13
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