INTRODUCTION

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Nano technology-Introduction:

The emerging fields of nanoscience and nanoengineering are leading to unprecedented understanding and control over the fundamental building blocks of all physical matter. This is likely to change the way almost everything —from vaccines to computers to automobile tires to objects not yet imagined —is designed and made.

                                Some notes on scale

                                     1A0=10-10m      

                                    1 nm=10-9m     atomic/crystallographic

 

                                     1 µm=10-6m    micro structure

                                   

                                    1mm=10-3m     macro structure

                                     1cm=10-2m

The word “Nano” means dwarf in Greek language. Use it as a prefix for any unit like a second or a meter and it means a billionth of that unit. A nanosecond is one billionth of a second. And a nanometer is one billionth of a meter—about the length of a few atoms lined up shoulder to shoulder. A world of things is built up from the tiny scale of nanometers. The thousands of cellular proteins and enzymes that constitute eg., The human bodies are a few nanometers thick. Enzymes typically are constructions of thousands of atoms in precise molecular structures that span some tens of nanometers. That kind of natural nanotechnology is about ten times smaller than some of the smallest synthetic nanotechnology that has been prepared until now. The individual components of an Intel Pentium III microprocessor span about 200 nanometers. This is the reason that computing is so powerful and easy these days. Nanotechnology makes microelectronics to be mere hints of what will come from engineering that begins on the even smaller scales of nanostructures.

 

Figure: The whole size issue; (a) Less than a nanometre- individual atoms are up to a few angstroms, or upto a few tenths of a nanometer in diameter; (b) Nanometer- Ten shoulder-to-shoulder hydrogen atoms (blue balls) span 1 nm. DNA molecules are about 2.5 nm wide; (c) Thousands of nanometers- Biological cells, like these red blood cells, have diameters in the range of thousands of nm; (d) a million nanometers- A pinhead sized patch of this thumb (black point) is a million nanometers across; (e) Billions of nanometers-a two meter tall person is two billion nanometers tall.                                                                                                                                                                                                    

 

                                  

 

 

 

 

Nanostructure science and technology is a broad and interdisciplinary area of research and development activity that has been growing explosively worldwide in the past few years. It has the potential for revolutionizing the ways in which materials and products are created and the range and nature of functionalities that can be accessed. It is already having a significant commercial impact, which will assuredly increase in the future.

                             

Figure: Evolution of science & technology and the future.

 

Emergence of Nano technology:

 

Nanotechnology is new, but research on nanometer scale is not new at all.

 

v      The Chinese are known to use Au nano particles as in inorganic dye to introduce red color into their ceramic porcelains more than thousand years ago.

v      A comprehensive study on the preparation and properties of colloidal gold was first published in the middle of the 19th century.

v      Colloidal dispersion of gold prepared by Faraday in 1857 was stable for almost a century before being destroyed during world war-II.

v      Colloidal gold is used for treatment of arthiritis.

v      In 1947 Dec 23 at AT&T Bell lab, the original Cm scale transistor made by Bardeen, Brattain, and Shockley at AT&T Bell lab.

v      With the evolution of semiconductor industry, there is continuous decrease in device dimensions, today’s transistors have well fallen in nanometer range.

v      The discovery of synthetic materials, such as carbon fullerenes, carbon nano tubes and ordered mesomorphous materials has further fuelled the research in nanotechnology and nanomaterials.

v      With the invention and development of scanning tunneling microscopy in the early 1980’s and subsequently SPM, AFM, TEM, it is possible to study and manipulate the nanostructures and nanomaterials to a great detail and often down to the atomic level.

v      Nanotechnology is not new, it is the combination of existing technologies and our new found ability to observe and manipulate at the atomic scale, this makes NT so compelling from scientific point.

The following are the mile stones in the evolution of Nanotechnology.

*       3.5 Mrd.years: First cells with nano machines.

*       400 B.C:  Demokrit: Reasoning about atoms and matter.

*       1905:  Albert Einstein: Calculated molecular diameter.

*       1931:  Max knoll&Ernst Ruska: Electron microscope

*       1959:  Richard Feynman: There is plenty of room at the bottom.

*       1968: Alfred Y.Cho & JohnArthur (Bell Labs): MBE (atomic layer growth).

*       1974: Norio Taniguchi: Nanotechnology for fabrication methods below 1µm.

*       1981: Gerd Binnig& Heinrich Rohrer: Noble prize for inventing STM.

*       1985: Robert F.Carl, Harald W.Kroto: Richard smalley: Bucky balls.

*       1986: K.Eric Drexler: writing with a STM tool.

*       1991: Sumio Ligima: Carbon Nanotubes.

*       1993: Warren robinett, R.Stanley Williams:  Combination of SEM and VR (virtual reality system).

*       1998: Cees Dekkar et all: Carbon nanotube transistor.

*       1999: James M.Tour& Mark.A.Read: Single molecule switch.

*       2000: Eigler et all: Construction of quantum mirrors.

*       2001: Florian Bambers: Soldering of nanotube with e-beam.

*       2004: Intel launches the Pentium iv ‘PRESCOFT’ processor based on 90nm technology.

 

“One nanometer is a magical point on the dimensional scale”. Why?

 

One nanometer is a magical point on the dimensional scale. Because there is a sudden shift of all properties of material when they just enters into the nanoscale.

As material size reduces from centimeter (bulk) to nanometer scale, properties mostly decreases as much as six orders of magnitude to that at macro level. The reason for this change is due to the nature of interactions among the atoms that are averaged out of existence in the bulk material. The same can be explained in another way i.e., surface energy increases with the overall surface area which in turn strongly dependent on the dimension of material. As nanostructures are having reduced dimensions, it leads to increase in surface energy via increase in surface area.

The change in properties from macro scale to nano scale can be observed by taking a simple example as given below.

Let us take an imaginary cube of gold 3 feet on each side. It is sliced in half along its length, width and height to produce eight little cubes, each 18 inches on a side. If we continue cutting the gold in this way from inches to centimeters, from centimeters to millimeters, and from millimeters to microns; we still notice no change in properties of gold between each stage except cash value and weight. All gold cubes are soft, shiny yellow and having same melting point.

But when these µm size gold particles are further sliced into nano size particles, every thing will be changed including gold’s color, melting point and chemical properties.

Melting point of nano gold is less than that of bulk gold melting point. Similarly instead of yellow color, nano gold particles appear in different color. This color depends on the size of the particle.

Not only for gold, all the materials will show the peculiar behavior and change in their properties when they enter into the nano scale. That is why one nanometer is called as a magical point on the dimensional scale.