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Nanotechnology Nanoparticles Particles
1.0 Introduction
1.1 Definition of Nanotechnology
Nanotechnology offers a way to create smaller, cheaper, lighter and faster devices that can do more things by using fewer raw materials and consume less energy. In simple terms, nanotechnology is defined as the design, characterization, production, and application of structures and devices by controlling shape and size between 1 nanometer and 100 nanometers or ‘engineering at a very small scale’.
1.1.1 Significance of Nanoscale
Properties of materials can be very different from those that are larger scale at nanoscale for two main reasons which are due to nanomaterials have a relatively larger surface area and the behaviour of matter at the nanoscale can be dominated by quantum effects.
1.2 Physics of Nanotechnology
1.2.1 Production of Nanoparticles
The building blocks of nanotechnology are nanoparticles. Production of nanoparticles can be basically classified into three general categories which are wet synthesis, dry synthesis and milling. Nanoparticles are produced in a bottom-up way from atomic precursor in both wet and dry synthesis. On the other hand, nanoparticles are produced from the top down by mechanically breaking down larger particles in the milling approach.
1.2.2 Application of Nanoparticles
Nanoparticles have the optical and magnetic properties that can be used to apply in many fields. The magnetic properties of nanotechnology can be applied in magnetic resonance imaging (MRI) because the small magnetic nanoparticles have the tendency to be superparamagnetic nanoparticles.
The other important market for nanoparticles is in the semiconductor industry, in a process known as chemical mechanical planarization (CMP). A combination of chemical removal and mechanical abrasion acts to accomplish the atomic-level polishing task in the chemical mechanical planarization.
1.3 Moore’s Law
Moore’s Law is an observation made in 1965 by Intel co-founder Gordon Moore that the number of transistors on a chip doubles about every 18 months, which translates to higher performance for roughly the same manufacturing cost. Moore’s empirical law summarizes the ‘economy of scale’ in getting the same function by making the working elements even smaller.
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2.1 Carbon Nanotubes
Carbon nanotubes(CNTs) were first observed by Sumio Iijima in 1991 (Foster 2006).
Carbon nanotubes are often described as graphene cylinders about 1-2nm in diameter and capped with end-containing pentagonal rings. There are two types of CNTs: single-walled (one tube) or multi-walled (several concentric tubes). The discovery of nanotubes enables the scientist exploit and observes materials and properties at the nanoscale. The general principle of nanotube growth involves producing reactive carbon atoms at a very high temperature.
These atoms will accumulate on the surface of metal particles in regular patterns and hence result in a long chain of assembled carbon atoms. Arc discharge, laser ablation, and chemical vapor deposition (CVD) are the methods to produce carbon nanotubes in enough quantities. The arc discharge method can produce a large amount of single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs) compared to the laser ablation. The CVD method is aided by a wealth of well-known inorganic chemicals specifically involving the formation of highly efficient catalysts of transition metals to produce primarily single-walled nanotubes.
2.1.1 Novel Properties
Carbon nanotubes have the properties of remarkable strength, high elasticity, and large thermal conductivity and current density. Studies have shown that SWNTs have strength of between 50 and 100 times that of steel and the elasticity of SWNT is 1-1.2 terrapascal (TPa). In addition, SWNTs have a thermal conductivity almost as great as twice that of diamond, which is known to be one of the best conductors of heat.
The most impressive property of SWNTs is their electrical conductivity, which is reported to be 109 Amps per square centimeter, about 100 times that reported in copper. SWNTs are very light because they have a density approximately half that of aluminium. Moreover, they are also very stables at temperatures up to 2700oC under vacuum.
2.2 Nanowires
Nanowires are ultrafine wires or linear array of dots, formed by self-assembly. Nanowires have potential applications in high-density data storage; either as magnetic read heads or as patterned storage media, and electronic and opto-electronic nanodevices, for metallic interconnects of quantum devices and nanodevices.
The preparation of nanowires relies on sophisticated growth techniques, which include self assembly processes, where atoms arrange themselves naturally on stepped surfaces, chemical vapour deposition (CVD) onto patterned substrates, electroplating or molecular beam epitaxy (MBE). The ‘molecular beams’ are typically from thermally evaporated elemental sources.
2.3 Quantum Dots
Quantum dots are the nanoparticles of semiconductors that created in the early 1980s. These are nanometer-sized single crystal grown in solution, taking care to give a uniform size. Quantum effects will limit the energies at which electrons and holes can exists in the particles when the quantum dots are made small enough. As energy is related to wavelength, this means that the optical properties of the particle can be finely tuned depending on its size.
Thus, particles can be made to emit or absorb specific wavelengths of light, merely by controlling their size. Quantum dots have been used in the fields of solar cells, fluorescent biological labels and composites as well which use both the small particle size and tuneable energy level. Recent advances in chemistry have resulted in the preparation of monolayer-protected, high-quality, monodispersed, crystalline quantum dots as small as 2nm in diameter, which can be conveniently treated and processed as a typical chemical reagent.
3.0 Application of nanotechnology
3.1 Medical Field
3.1.1 Drug Delivery
Biopolymers have been intensively studied for application in nanoparticulate drug delivery. Nanotechnology increase bioavailability and improve drug delivery like encapsulate molecules within nanoscale cavities inside polymers. It has an internal frame, skin panels, internal organelles and a control system. (Malsch n.d.)
Source: http://www.tipmagazine.com/tip/INPHFA/vol-8/iss-3/p15.pdf
When patient swallow the polymer, the polymeric structure opens within the body and released out the drugs to particular target cells or organs. Much more complex drug delivery schemes have also been developed such as the ability to get drugs through cell walls and into cells by encapsulating the polar drug in a nonpolar coating that will easily pass through the cell membrane (Ratner 2002).
3.1.2 Diagnosis
Nanotechnology enables a much faster and more precise diagnosis, as many tests can be built into a single, often palm-sized device which is known as ‘lab-on-a-chip’ that only requires tiny quantities of sample and the sample can be processed and analyzed in a short time.
3.2 Sensors
3.2.1 Biological Sensors
Nanotechnology enables the sensitive detection of a broad range of biomolecules. A cylindrical rod that made up of metal section is done by the sequential electrochemical reduction of the metal ions onto an alumina template. These particles are known as Nanobarcodes can be coated with analyte-specific entities such as antibodies, for selective detection of complex molecules.
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Carbon nanotubes, zinc oxide nanowires or palladium nanoparticles are the types of detecting elements can be used in nanotechnology-based sensors. The nanomaterial are very small in size and this enable a few gas molecules which mean a low concentration of chemical vapours are enough to change the electrical properties of the sensing elements.
3.2.3 Physical Sensors
According to Foster (2006), researchers at the Georgia Institute of Technology demonstrated the world’s smallest balance by taking advantage of the unique electrical and mechanical properties of carbon nanotubes. The carbon nanotubes will oscillate without breaking and the mass of the particle was calculated from changes in the resonance vibrational frequency with and without particle. This approach leads to a technique for the weight measurement of individual biomolecules.
3.3 Electronics
Nanotechnology can improve display screens on electronic devices. This involves reducing power consumption while decreasing the weight and thickness of the screens. In addition, nanotechnology also increase density of memory chips by developing one type of memory chips with a projected density of one terabyte of memory per square inch or greater and reduce the size of transistors that used in integrated circuit in the electronics field.
3.4 Environment
3.4.1 Air Quality
There are two major ways in which nanotechnology is being used to reduce air pollution: catalysts, which are currently in use and constantly being improved upon; and nano-structured membranes, which are still under development. Nanotechnology can improve the performance of catalyst used to transform vapors escaping from vehicles or industrial plants into harmless gasses due to the catalyst made from nanoparticles have a greater surface area to interact with reacting chemicals.
This characteristic enables more chemicals to interact with the catalyst simultaneously. On the other hand, nanostructured membranes are being developed to filter the carbon dioxide which is one type of greenhouse gases from industrial plant exhaust streams.
3.4.2 Water Quality
Nanotechnology is also being used to develop solutions to solve problems in water quality. First problem is the removal of industrial wastes such as a cleaning solvent called TCE by the use of nanoparticles. The second problem is the removal of salt and metal from water. A deionization method using electrodes composed of nano-sized fibers shows proof for reducing the cost and energy requirements of turning salt water into drinking water.
3.5 Food Industries
Many food and drinks contain natural components that are nanoscale in size, and the manipulation of naturally occurring particles involved in the processing in of, for example in dairy products. Targeted delivery has enable food companies to deliver scents, flavors, vitamins and minerals that offer health benefits or impart new physical, visual and sensory effects to foods. In addition, the antibacterial work surfaces which act as a filter can extract toxins and packaging that provide better protection against contamination, or can signal when its contents are spoilt.
4.0 Conclusion
Nanotechnology is still developing nowadays. The advantages of nanotechnology are far overweighing the disadvantages. In brief, nanotechnology is very useful in most of the field and researchers have successfully found out it has the biggest impact on the medical industry.
However, there are some hefty social concerns about nanotechnology too. Nanotechnology may also allow us to create more powerful weapons which are very dangerous. Hence, we should cooperate to prevent the negative effects of nanotechnology to occur and on the other way to magnify the positive application of nanotechnology in order to have a more convenient life.
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