‘Nano’: a little word with huge potential

 

A little word with huge potential has been rapidly working its way into the world's consciousness. This word is ‘nano’, nowadays, frequently used as prefix to indicate that nanotechnology or nanomaterials are used to add specific properties to products. The prefix nano refers to the size of the materials being a nanometer (nm=10⁻⁹m).

 

Modern synthetic chemistry has reached the point where it is possible to control and manipulate matter at atomic, molecular or macromolecular level and manufacture components at the ‘nano’-scale (dimensions between 1 and 100nm).

 

 

What is nanotechnology

 

Nanotechnology is a collective term referring to the application of nanomaterials or techniques at the nanoscale. It is an innovative enabling technology with the potential to develop novel materials able to introduce new nano-specific properties to products, devices and systems in wide-ranging professional and consumer applications, in almost all industrial sectors, including medicines, cosmetics, electronics, energy production, etc. Therefore, generally the more appropriate plural form ‘nanotechnologies’ is used.

 

The essence of nanotechnologies is the ability to work at the molecular level, atom by atom, to create larger structures with fundamentally new molecular organization.[1] At the nanoscale one enters a world where physics and chemistry meet and develop novel properties of matter, where the most fundamental properties of materials and machines depend on their size in a way they don't at any other scale.[2] Nanotechnologies take advantage of these properties and aim to fabricate improved materials, devices and systems that have new properties and functions.

 

Nanomaterials (also called nano-objects) are defined as particles with one, two or three dimensions at the nanoscale. Based on their structure they can be classified into one of the following categories:

 

Nanoplates - particles with only one dimension at the nanoscale and the other two dimensions being significantly larger (differing by more than 3 times) that may not be in the nanoscale (i.e. a nanoclay).

 

Nanofibers - particles with two dimensions at the nanoscale and the third dimension significant larger (i.e. single wall carbon nanotubes and multiwall carbon nanotubes).

・Nanotube - a nanofiber possessing a hollow tub-like structure (i.e. carbon nanotube);
・Nanowire - a massive, flexible nanofiber;
・Nanorod - a massive, rigid nanofiber.

Nanoparticles - particles with all three dimensions at the nanoscale (i.e. nano-titanium dioxide).

 

Nanomaterials may be suspended in a gas (e.g. nanoaerosol), suspended in a liquid

(e.g. nanocolloid or nanohydrosol), or embedded in a matrix (e.g. nanocomposite).

 

 

Defining nanomaterials: a challenging task

 

After several years of scientific and policy dispute over how exactly to define nanomaterials, in October 2011, the EC adopted the Recommendation on the definition of nanomaterials, according to which ‘nanomaterial’ is defined as “a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1nm - 100nm. 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 and 50 %. […]”.

 

The issue of defining nanomaterials has been a challenging task and even though the proposed definition is rather ‘narrow’, it is a solid starting point for further discussions. The requirement that at least 50% of the number of particles should be in the size range of 1nm - 100nm is expected to be further explored and take into account future scientific findings, in the foreseen definition review in 2014.

 

It is worthwhile noting that according to the EC definition, nanomaterials are not exclusively synthesized/manufactured nanomaterials. The term also covers particles originating from natural processes and heating/combustion processes (incidental nanoparticles), which may pose similar risks to human health and the environment.

 

It may not be obvious to most people, but definitions of substances, threats and issues are what underpin the legal instruments regulating them.

The scale of things.

Towards the molecular dimension. Nanoscale structures.

[1] Ali Mansoori. Principles of Nanotechnology. Molecular-based study of condensed matter in small systems. World Scientific Publ, 2005.

[2] Goddard W. Brenner DW, Lysevski S, Lafrate GJ. Handbook of Nanoscience, engineering and technology. CRC Press, Taylor & Francis, 2nd ed., 2007.

A historical journey into the Nano World

 

The fundamentals of nanotechnologies were gradually set over many decades of research in many different scientific fields. The dawn of the nano world can be traced back to 1959, when a physicist at Caltech, Richard P. Feynman, later Nobel Prize Winner in Physics, gave a talk titled "There's Plenty of Room at the Bottom".[3] In his talk which is widely considered to have been prophetic, Feynman hypothesized that atoms and molecules could be accurately manipulated, like building blocks, though he never explicitly mentioned the term "nanotechnology." He suggested that it would be possible to create small-scale machines able to manufacture objects with atomic precision. As the scale got smaller and smaller the properties of matter such as gravity would become more negligible, while both Van Der Waals attraction (forces which are relatively weak compared to normal chemical bonds) and surface tension would become very important.

 

In the late 1970s and early 1980s the researcher and author Eric Drexler established the fundamental principles of molecular design, protein engineering and productive nanosystems. In 1986 Drexler introduced the term "nanotechnology" in his book “Engines of Creation” to describe engineering at the nanometer scale.[4] The term though, had been used previously in 1974 by Norio Taniguchi in Japan, referring to precision micromachining.

 

 

Are Nanotechnologies new?

 

Even though nanomaterials are often perceived as new materials this is not the case. All biological cells are comprised by smart materials that have been positioning atoms since time immemorial and nanostructures are associated with natural processes. There are hundreds of examples of naturally occurring nanomaterials present in the environment, such as volcanic ash, ocean spray, mineral composites, ferritin, lipoprotein particles and others. There are the incidental-nanomaterials which are often by-products produced as a result of industrial or other processes (also called process-generated nanoparticles) such as combustion of fossil fuels, mining, biomaterial degradation, etc. The third category includes manufactured nanomaterials which are materials that have been deliberately created and designed for specific functions.

 

Research at the nanoscale level has catalyzed the development of nanotechnologies which involve purposeful manipulation at atomic level and structural assembly to achieve predetermined properties and functions of materials or products.[5]

 

 

What makes ‘nano’ special?

 

The nano world is full of surprises and potential. The reason that nanoscale materials and structures are so interesting is that size constraints often produce qualitatively new behavior. At the nanometer scale matter has different, sometimes unexpected, physical and chemical properties. At the nanoscale the chemical, electrical, magnetic, mechanical and optical properties of matter are quite different than in the bulk form of the same materials. For example, bulk silver is non-toxic, whereas silver nanoparticles are capable of killing bacteria and viruses upon contact, and therefore are used as biocides. Also, the same metal can become a semiconductor or insulator at the nanoscale. A key element contributing to the exceptional properties of nanomaterials is their increased surface-to-volume compared to bulk materials. This is important in catalysis (the process in which the rate of a chemical reaction is either increased or decreased by means of a chemical substance known as a catalyst) and detection processes, as it results in increased surface reactivity.[6]

 

 

Fundamental concepts of nanotechnologies

 

Atoms as basic units of matter can be combined to form more complex structures such as molecules and compounds. Nanomaterials as arrangements of matter at the nanoscale can be fabricated either bottom-up or top-down.[7]

 

The bottom-up approach is the process where nanostructures are created atom-by-atom. One bottom-up approach called self-assembly refers to the tendency of some materials to organise themselves into ordered arrays. This self-assembling nature allows different atoms, molecules, or nanomaterials when mixed together to spontaneously organize into stable, well-defined structures, with unique geometries and electronic structures.

 

The top-down approach refers to the way of fabricating nanomaterials of a desired size or shape by being carved out of a bulkier one.

 

Bottom-up and Top-Down approach

[3] Feynman R. There is plenty room at the bottom. Journal of Microelectromechanical systems, 1(1): 60-66, 1992.

(http://media.wiley.com/product_data/excerpt/53/07803108/0780310853.pdf)

[4] Drexler KE. Engines of Creation. The coming era of Nanotechnology. Anchor Books, New York, 1986. (http://e-drexler.com).

[5] Environmental Protection Agency (http://epa.gov/ncer/nano/questions/)

[6] Filiponi L, Sutherland D. Nanotechnology: A brief introduction. Interdisciplinary Nanoscience Center, University of Aarhus, Denmark, 2007.

[7] Miller JC, Serrato RM, Represas-Cardenas JM, Kundahl GA, Graffagnini M. The Handbook of Nanotechnology. Business, Policy and Property Law. John Wiley & Sons, 2004.

Nanotechnologies and nanomaterials:

fields of application

 

Due to the unique chemical, physical and mechanical properties nanomaterials possess, they are used in a wide variety of applications of advanced materials, devices and products. Some fields of nanotechnologies and nanomaterial applications are listed below:

 

Medicine: improved diagnosis of diseases through the use of sensitive nanotech detectors, treatment of diseases through more targeted drug therapies or “smart drugs” that use nanostructures, prevention of diseases through nanotechnology immune stimulants which prevent the propagations of infections, etc.

Environment: monitoring of the environment, reducing pollution impacts through air and water nanofilters, by using less material, reducing emissions through improved fuel catalysis, remediation of contaminated sites, etc.

Energy: miniaturized data storage devices that use less energy to operate, better insulation materials, improved efficiency of renewable energy sources, etc.

Electronics: enhanced computer and telecommunications properties, etc.

Consumer goods: improved production processes, safety and packaging of food, self cleaning surfaces, water- and stain-repellent or wrinkle-free textiles, etc.

 

Commercialisation of nanotechnology applications and products is proceeding quickly, with a large number of products identified already in the market (>1000 products). Some of the commercially available nanoproducts are computer processors and hard disks, nanotube tennis rackets, nanodynamic golfballs, nanofilm window sprays, deep penetrating skin creams, titanium dioxide sunscreens, silver nano toothpaste, footwarmers, washable bed mattresses, nano silver anti-odor socks, stain resistance clothing, antibacterial kitchenware, nano vitamin sprays, nano tea, nutritional drinks, etc.[8],[9],[10]

Nanotechnology products available on the market