Materials scientists have long focused their attention on the structure of materials in the scale varying from micro (1μm = 10-6 m) to macro (or bulk), as well as on the properties of materials controlled by structures that exist and interact over these scales. Furthermore there are other materials having a critical dimension on the scale of 1-100 nm (1 nanometer = 1nm = 10-9m), at least in one of the three dimensions, that exhibit properties being absent in the bulk solid state; these are called nanomaterials. These unique properties of nanomaterials, which are dominated by quantum-mechanical effects, play a primary role in many of the bulk properties exhibited by real materials. Nanomaterials exist with great chemical diversity in the form of metals, metal oxides, semiconductors, polymers, carbon materials, organics or biological. They also exhibit great morphological diversity with shapes such as spheres, cylinders, disks, platelets, hollow spheres and tubes, etc.
For terminology reasons, we mention that nanoscience is the study of the properties of nanomaterials and nanotechnology is the collection of procedures for manipulating nanomaterials in order to build new and advanced nanosized entities for useful purposes. Strictly speaking, the National Nanotechnology Initiative (NNI) has defined nanotechnology as “working at the atomic, molecular and supramolecular levels, in the length scale of approximately 1–100 nm range, in order to understand and create materials, devices and systems with fundamentally new properties and functions because of their small structure”. Naturally, this broadly defined area of science and engineering has a significant “chemistry” component.
It is worth noting that the original version of nanotechnology occurs in nature, where organisms developed the ability to manipulate light and matter on an atomic scale to build devices that perform specific functions, such as storing information, reproducing themselves and moving about. For instance, ‘DNA is the ultimate nanomaterial’ that stores information and reproduces itself as the sequence of base-pairs that are spaced about 0.3 nm apart. Moreover, the folded DNA-molecules have an information density of more than 1 Tb·cm-2, approximately (1Tb = 1012bits). Another example of bio-nanotechnology is ‘photosynthesis’, where nanostructures are exploited to absorb light, separate electric charge, shuttle protons around and substantially convert solar energy into biologically useful chemical energy.
Last but not least, humans have practiced nanotechnology more as an art than a science or/and engineering for centuries, since gold and silver salts have long been used to stain the glass red and yellow, respectively. In stained glass, the metal atoms form nanoparticles, previously known as ‘colloidal particles’, with optical properties strongly dependent upon their size. Nowadays, metallic nanopigments are becoming a focal point of biomedical nanotechnology, since they can be used to tag DNA and other bio-nanoparticles.
The science and engineering of nanotechnology began to take shape in the latter half of 20th-century. The development of scanning tunneling microscopy, which was made by Gerd Binnig and Heinrich, contributed decisively to this direction, by providing us with the capability to characterize the nanostructures.
Nanomaterials can be generated via a number of synthetic routes based on gas, liquid or solid phase approaches. The nanomaterials are also surface-functionalized in order to meet the needs of specific applications. To sum up, nanomaterials serve as the building blocks for various nanotechnology applications. Therefore nanotechnology is very diverse, ranging from extensions of conventional device physics to completely new approaches based upon molecular self-assembly, from developing new materials with dimensions on the nanoscale to investigating whether we can directly control matter on the atomic
scale. Nanotechnology entails the application of fields of science as diverse as surface science, organic chemistry, molecular biology, semiconductor physics, microfabrication, etc.
There is much debate on the future implications of nanotechnology. Nanotechnology may be able to create many new materials and devices with a vast range of applications, such as in medicine, electronics, biomaterials and energy production. On the other hand, nanotechnology raises many of the same issues as any new technology, including concerns about the toxicity and environmental impact of nanomaterials, as well as their potential effects on global economics. It must be recognized that, because of the diverse and unique
properties of engineered nanomaterials, safe implementation of nanotechnology is a multidisciplinary exercise that goes beyond traditional hazard, exposure and risk assessment models. The significant challenge now concerns the standardization, harmonization and implementation of environmental, health and safety data related to nanomaterials and nanotechnology and a coordinated governance strategy to ensure safe implementation of this technology.
References
1.Klabunde, K.J.; Richards, R.M. (Eds.). Nanoscale Materials in Chemistry; 2nd Ed.; Wiley, 2009.
2. Nagarajan, R.; Hatton, T.A. (Eds.). Nanoparticles: Synthesis, Stabilization, Passivation and Functionalization; In ACS Symposium Series 996; USA, 2008.
3. Roco, M.C.; Mirkin, C.A.; Hersam, M.C. Nanotechnology Research Directions for Societal Needs in 2020: Retrospective and Outlook; In Science Policy Reports Series; Springer, 2011.
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Notes:
i.This article could be classed in the category of Technology or/and Chemistry
ii.The author of this article is Dr. Eleni D. Metaxa