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The term paper deals with the introduction to nanotechnology a chemistry point of view and its derivation from past. The new devices, technologies and materials in nanotechnology that are being used in the present era are discussed. Since chemistry has various branches therefore, there are different fields of nanotechnology in which chemistry is studied. The molecular nanotechnology (MTN) and radical nanotechnology are covered. Nanotechnology has a feature that, it involves various sciences of nature. The potential harms and its applications are also discussed.
NanotechnologyÂ comprises anyÂ technologicalÂ developments on theÂ nanometerÂ scale, usually 0.1 to 100 nm. (One nanometer equals one thousandth of aÂ micrometerÂ or one millionth of aÂ millimeter.) The term has sometimes been applied to anyÂ microscopicÂ technology.
The term nanotechnology is often used interchangeably withÂ molecular nanotechnologyÂ (also known as "MNT"), a hypothetical, advanced form of nanotechnology believed to be achievable at some point in the future. Molecular nanotechnology includes the concept ofÂ mechanosynthesis. The term nanoscienceÂ is used to describe the interdisciplinary field of science devoted to the advancement of nanotechnology.
The size scale of nanotechnology makes it susceptible to quantum-based phenomena, leading to often counterintuitive results. These nanoscale phenomena includeÂ quantumÂ size effects and molecular forces such asÂ Van der Waals forces. Furthermore, the vastly increased ratio of surface area to volume opens new possibilities in surface-based science, such asÂ catalysis.
Origin Of Nanotechnology
The first mention of nanotechnology (not yet using that name) occurred in a talk given byÂ Richard FeynmanÂ inÂ 1959, entitledÂ There's Plenty of Room at the Bottom. Feynman suggested a means to develop the ability to manipulate atoms and molecules "directly", by developing a set of one-tenth-scale machine tools analogous to those found in any machine shop. These small tools would then help to develop and operate a next generation of one-hundredth-scale machine tools, and so forth. As the sizes get smaller, we would have to redesign some tools because the relative strength of various forces would change.Â GravityÂ would become less important, surface tension would become more important,Â Van der WaalsÂ attraction would become important, etc. Feynman mentioned these scaling issues during his talk. Nobody has yet effectively refuted the feasibility of his proposal.
The termÂ NanotechnologyÂ was created by Tokyo Science University professor Norio Taniguchi inÂ 1974Â to describe the precision manufacture of materials with nanometre tolerances. In theÂ 1980sÂ the term was reinvented and its definition expanded byÂ K Eric Drexler, particularly in hisÂ 1986Â bookÂ Engines of Creation: The Coming Era of Nanotechnology. He explored this subject in much greater technical depth in hisÂ MITÂ doctoral dissertation, later expanded intoÂ Nanosystems: Molecular Machinery, Manufacturing, and Computation. Computational methods play a key role in the field today because nanotechnologists can use them to design and simulate a wide range of molecular systems.
Early discussions of nanotechnology involved the notion of a general-purpose assembler with a broad range of capability to build different molecular structures. The possibility of self-replication, the idea that assemblers could build more assemblers, suggests that nanotechnology could reduce the price of many physical goods by several orders of magnitude. Self-replication is also the basis for theÂ grey gooÂ scenario. More recent thinking has focused instead on a moreÂ factory-oriented approachÂ to construction. The smallest elements of a product would be built on assembly lines, then assembled into progressively larger assemblies until the final product is complete.
A cut-away view of a desktop nanofactory (made by artist)
New Materials, Devices, Technologies In Nanotechnology With Application Of Chemistry
Nanotechnology develops minute technology; this is a model of "nanogears", as small as only a few atoms wide.
As science becomes more sophisticated it naturally enters the realm of what is arbitrarily labeled nanotechnology. The essence of nanotechnology is that as we scale things down they start to take on extremely novel properties. Nanoparticles (clusters at nanometre scale), for example, have very interesting properties and are proving extremely useful as catalysts and in other uses. If we ever do make nanobots, they will not be scaled down versions of contemporary robots. It is the same scaling effects that make nanodevices so special that prevent this. Nanoscaled devices will bear much stronger resemblance to nature's nanodevices: proteins, DNA, membranes etc. Supramolecular assemblies are a good example of this.
One fundamental characteristic of nanotechnology is that nanodevices self-assemble. That is, they build themselves from the bottom up.Â Scanning probe microscopyÂ is an important technique both for characterization and synthesis of nanomaterials.Â Atomic force microscopesÂ andÂ scanning tunneling microscopesÂ can be used to look at surfaces and to move atoms around. By designing different tips for these microscopes, they can be used for carving out structures on surfaces and to help guide self-assembling structures. Atoms can be moved around on a surface with scanning probe microscopy techniques, but it is cumbersome, expensive and very time-consuming, and for these reasons it is quite simply not feasible to construct nanoscaled devices atom by atom. You don't want to assemble a billion transistors into a microchip by taking an hour to place each transistor, but these techniques can be used for things like helping guide self-assembling systems.
One of the problems facing nanotechnology is how to assemble atoms and molecules into smart materials and working devices.Â Supramolecular chemistryÂ is here a very important tool. Supramolecular chemistry is the chemistry beyond the molecule, and molecules are being designed toÂ self-assembleÂ into larger structures. In this case, biology is a place to find inspiration: cells and their pieces are made from self-assembling biopolymers such asÂ proteinsÂ and protein complexes. One of the things being explored is synthesis of organic molecules by adding them to the ends of complementary DNA strands such as ----A and ----B, with molecules A and B attached to the end; when these are put together, the complementary DNA strands hydrogen bonds into a double helix, ====AB, and the DNA molecule can be removed to isolate the product AB.
Natural or man-made particles or artifacts often have qualities and capabilities quite different from their macroscopic counterparts.Â Gold, for example, which is chemically inert at normal scales, can serve as a potent chemicalÂ catalystÂ at nanoscales.
"Nanosize" powder particles (a few nanometres in diameter, also called nano-particles) are potentially important in ceramics, powder metallurgy, the achievement of uniform nanoporosity, and similar applications. The strong tendency of small particles to form clumps ("agglomerates") is a serious technological problem that impedes such applications. However, a few dispersants such as ammonium citrate (aqueous) and imidazoline or oleyl alcohol (nonaqueous) are promising additives for deagglomeration. (Those materials are discussed in "Organic Additives And Ceramic Processing," by D. J. Shanefield, Kluwer Academic Publ., Boston.)
In October 2004, researchers at The University Of Manchester succeeded in forming a small piece of material only 1 atom thick calledÂ graphene. Robert FreitasÂ has suggested that graphene might be used as a deposition surface for a diamandoid mechanosynthesis tool.
Molecular Nanotechnology (MNT)- In Accordance With Chemistry
Molecular nanotechnology, sometimes called molecular manufacturing, describes engineered nanosystems (nanoscale machines) operating on the molecular scale. Molecular nanotechnology is especially associated with theÂ molecular assembler, a machine that can produce a desired structure or device atom-by-atom using the principles ofÂ mechanosynthesis. Manufacturing in the context of productive nanosystemsÂ is not related to, and should be clearly distinguished from, the conventional technologies used to manufacture nanomaterials such as carbon nanotubes and nanoparticles.
When the term "nanotechnology" was independently coined and popularized byÂ Eric DrexlerÂ (who at the time was unaware of anÂ earlier usageÂ byÂ Norio Taniguchi) it referred to a future manufacturing technology based onÂ molecular machineÂ systems. The premise was that molecular scale biological analogies of traditional machine components demonstrated molecular machines were possible: by the countless examples found in biology, it is known that sophisticated,Â stochasticallyÂ optimised biological machines can be produced.
It is hoped that developments in nanotechnology will make possible their construction by some other means, perhaps usingÂ biomimeticÂ principles. However, Drexler and other researchersÂ have proposed that advanced nanotechnology, although perhaps initially implemented by biomimetic means, ultimately could be based on mechanical engineering principles, namely, a manufacturing technology based on the mechanical functionality of these components (such as gears, bearings, motors, and structural members) that would enable programmable, positional assembly to atomic specification.Â The physics and engineering performance of exemplar designs were analyzed in Drexler's bookÂ Nanosystems.
In general it is very difficult to assemble devices on the atomic scale, as all one has to position atoms on other atoms of comparable size and stickiness. Another view, put forth by Carlo Montemagno,Â is that future nanosystems will be hybrids of silicon technology and biological molecular machines. Yet another view, put forward by the lateÂ Richard Smalley, is that mechanosynthesis is impossible due to the difficulties in mechanically manipulating individual molecules.
This led to an exchange of letters in theÂ ACSÂ publicationÂ Chemical & Engineering NewsÂ in 2003.Â Though biology clearly demonstrates that molecular machine systems are possible, non-biological molecular machines are today only in their infancy. Leaders in research on non-biological molecular machines are Dr.Â Alex ZettlÂ and his colleagues at Lawrence Berkeley Laboratories and UC Berkeley. They have constructed at least three distinct molecular devices whose motion is controlled from the desktop with changing voltage: a nanotubeÂ nanomotor, a molecular actuator,Â and a nano electromechanical relaxation oscillator.
An experiment indicating that positional molecular assembly is possible was performed by Ho and Lee atÂ Cornell UniversityÂ in 1999. They used a scanning tunneling microscope to move an individual carbon monoxide molecule (CO) to an individual iron atom (Fe) sitting on a flat silver crystal, and chemically bound the CO to the Fe by applying a voltage.
Radical Nanotechnology- In Accordance With Chemistry
Radical nanotechnology is a term given to sophisticated nanoscale machines operating on the molecular scale. By the countless examples found in biology it is currently known that radical nanotechnology would be possible to construct. Many scientists today believe that it is likely that evolution has made optimized biological nanomachines with close to optimal performance possible for nanoscale machines, and that radical nanotechnology thus would need to made byÂ biomimeticÂ principles. However, it has been suggested byÂ K Eric DrexlerÂ that radical nanotechnology can be made by mechanical engineering like principles. Drexler's idea of a diamondoidÂ molecular nanotechnologyÂ is currently controversial and it remains to be seen what future developments will bring.
A definitive feature of nanotechnology is that it constitutes an interdisciplinary ensemble of several fields of the natural sciences that are, in and of themselves, actually highly specialized. Thus, physics plays an important role-alone in the construction of the microscope used to investigate such phenomena but above all in the laws of quantum mechanics. Achieving a desired material structure and certain configurations of atoms brings the field of chemistry into play. In medicine, the specifically targeted deployment of nanoparticles promises to help in the treatment of certain diseases. Here, science has reached a point at which the boundaries separating discrete disciplines become blurred, and it is for precisely this reason that nanotechnology is also referred to as a convergent technology.
An often cited worst-case scenario is the so-called "grey goo", a substance into which the surface objects of the earth might be transformed by self-replicating nano-robots running amok, a process which has been termedÂ global ecophagy. Defenders point out that smaller objects are more susceptible to damage from radiation and heat (due to greater surface area-to-volume ratios). Nanomachines would quickly fail when exposed to harsh climates. More realistic are criticisms that point to the potentialÂ toxicityÂ of new classes of nanosubstances that could adversely affect the stability ofÂ cell wallsÂ or disturb theÂ immune systemÂ when inhaled or digestedÂ . Objective risk assessment can profit from the bulk of experience with long-known microscopic materials like carbonÂ sootÂ orÂ asbestosÂ fibres.
Application and future prospective
Smart Materials and Nanosensors
One application of nanotechnology is the development of so-called smart materials . This term refers to any sort of material designed and engineered at theÂ nanometreÂ scale to perform a specific task, and encompasses a wide variety of possible commercial applications. One example is materials designed to respond differently to various molecules; such a capability could lead, for example, to artificial drugs which would recognize and render inert specific viruses. Another is the idea of self-healing structures, which would repair small tears in a surface naturally in the same way as self-sealing tires or human skin; and while this technology is relatively new, it is already seeing commercial application in various engineering plastics.
A nanosensor would resemble a smart material, involving a small component within a larger machine that would react to its environment and change in some fundamental, intentional way. As a very simple example: a photosensor could passively measure the incident light and discharge its absorbed energy as electricity when the light passes above or below a specified threshold, sending a signal to a larger machine. Such a sensor would cost less and use less power than a conventional sensor, and yet function usefully in all the same applications - for example, turning on parking lot lights when it gets dark.
While smart materials and nanosensors both exemplify useful applications of nanotechnology, they pale in comparison with the complexity of the technology most popularly associated with the term: the replicating nanorobot.
Nanofacturing is popularly linked with the idea of swarms of coordinated nanoscale robots working together, as proposed by Drexler in his 1986 popular discussions of the subject. In theory, nanobots could construct more nanobots.
However, critics doubt the feasibility of controllable self-replicatingÂ nanobots: they cite the possibility ofÂ mutationsÂ removing any control and favoring reproduction of mutant pathogenic variations. Advocates counter thatÂ bacteriaÂ are (of necessity) evolved to evolve, while nanobot mutation can be actively prevented by commonÂ error-correctingÂ techniques. Similar ideas are advocated in theÂ Foresight Guidelines on Molecular Nanotechnology.
Recent technical proposals forÂ nanofactoriesÂ do not include self-replicating nanobots, and recent ethical guidelines prohibit self-replication.
One of the most important applications of molecular nanotechnology will be medicalÂ nanoroboticsÂ orÂ nanomedicine. The ability to design, build, and deploy large numbers of medical nanorobots will make possible the rapid elimination of disease and the reliable and relatively painless recovery from physical trauma. Medical nanorobots will also make possible the convenient correction of genetic defects, and can help to ensure a greatly expanded healthspan. More controversially, medical nanorobots could be used to augment natural human capabilities. However, mechanical medical nanodevices will not be allowed (or designed) to self-replicate inside the human body, nor will medical nanorobots have any need for self-replication themselvesÂ since they will be manufactured exclusively in carefully regulated nanofactories.
Another proposed application of nanotechnology involvesÂ utility fogÂ - in which a cloud of networked microscopic robots (simpler thanÂ assemblers) changes its shape and properties to form macroscopic objects and tools in accordance with software commands. Rather than modify the current practices of consuming material goods in different forms, utility fog would simply replace most physical objects.
Yet another proposed application would be phased-array optics (PAO). PAO would used the principle of phased-array millimeter technology but at optical wavelengths. This would permit the duplication of any sort of optical effect but virtually. Users could request holograms, sunrises and sunsets, or floating lasers as the mood strikes. PAO systems were described in BC Crandall'sÂ Nanotechnology: Molecular Speculations on Global AbundanceÂ in the Brian Wowk article "Phased-Array Optics".
The primary technical reference work on this topic isÂ Nanosystems: Molecular Machinery, Manufacturing, and Computation, an in-depth, physics-based analysis of a particular class of potential nanomachines and molecular manufacturing systems, with extensive analyses of their feasibility and performance.Â NanosystemsÂ is closely based on Drexler's MIT doctoral dissertation,Â "Molecular Machinery and Manufacturing with Applications to Computation". Both works also discuss technology development pathways that begin with scanning probe and biomolecular technologies.
Drexler and others extended the ideas of molecular nanotechnology with several other books.Â Unbounding the Future: the Nanotechnology RevolutionÂ "Unbounding the Future: Table of Contents". Foresight.org.
Nanotechnology: Molecular Speculations on Global AbundanceÂ Edited by BC Crandall offers interesting ideas for MNT applications.