2 - 1 - 1.1 Definitions and Nanomaterials [15_36]

8/10/2019 2 - 1 - 1.1 Definitions and Nanomaterials [15_36]

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Hello my name is Hossam Haick and I willserveas the lecturer of the MOOC course onnanotechnology and nanosensors.I wish you a successful course on thegreatjourney into the amazing world ofnanotechnology and nanosensors.Today I will make an introduction to thefield of nantechnology.I will start with defining the mainphrases that include the word nano.Then I will present the main and uniquefeatures ofthe materials and technologies that existat the nanoscale level.I will end this topic by making a genericpresentation ofthe main categories of the materials thatexist at the nanoscale level.The prefix nano is derived from theancient Greek nanos, which meansdwarf.Today, nano is used as a

prefix that means, billionth or a factorof 10 to the minus9.Coupling the word nano with the unit meterbrings the term nanometer, which actuallyindicates a unit of spatial measurementthat is one billionth of a meter.With this in mind, we shalldefine nanotechnology as the science,engineering,and technology conducted at the scale thatranges between one to 100 nanometers.The idea and the concept behind the

nanotechnology started with atalk entitled, There is Plenty of Room atthe Bottom, by thephysicist Richard Feynman, at the AmericanPhysical Society meeting, at theCaliforniaInstitute of Technology, CalTech, in ameeting that was held in 1959.In his talk, Feynman described a processin which scientistswould be able to manipulate and controlindividual atoms as well as individualmolecules.

Over a decade later, Professor NorioTaniguchi coined the term nanotechnologyduringhis explorations and research in the fieldof ultra precise machining process.However, practicing the modernnanotechnology beganonly in 1981, when the scanningtunneling microscope, which basicallycould see individual atoms


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or could see individual molecules, wasdeveloped and used.To demonstrate the length of scale of thenanometer, I willpresent first the units or measures usedin our daily life.If we cut a meter into 100 equal pieces,then each piece would be one centimeter insize.This is equivalent to the size of yourpinky finger or a sugar cube.If we cut a centimeter into 100 equalpieces, each piece will be one millimeter.A cent coin is approximately onemillimeter thick, and a grainof sand ranges from 0.1 millimeter to 2millimeter in size.Objects as small as millimeter can be seenwith our own eyes.However, when things get smaller than amillimeter, it getsharder and harder to see them with justour eyes.If we cut up a millimeter into 100 equal

pieces, each piece will be a micrometer.In other words, a micrometer is equal toone millionth of the meter.For example, the diameter of hair is about40 to 50 micrometers wide, redblood cells are six to ten micrometers indiameter and many types of bacteriatypically measure five to 20 micrometersin diameter or in size.Things on this scale usually cannot beseen with our own eyes,but rather, can be seen with a magnifyingglass or with a microscope.

If we cut a micrometer, now, into 1,000equal pieces, then each piece will be onenanometer.In other words, a nanometer is equal toone billionth of a meter.When things are as small as the nanometeryou cannot see them withyour own eyes, or even you cannot see themwith a light microscope.Objects this small require special toolsof imaging.Things that have a nanometer scale includeviruses which

have a characteristic size of 30 to 50nanometer.DNA, which have a diameter of one to twonanometer.Buckyballs with have a characteristic sizeor diameter of one nanometer.And also carbon nanotubes which have acharacteristic diameter of one nanometer.In this context I would like toclarify that atoms are smaller than a


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nanometer.Actually, one atom measures 0.1 to 0.3nanometer, andthis, of course, depends on the elementthat is examined.Now I will give you some examples forobjectsfrom our daily life that are measured innanometer.One inch is equal to 25.4 millionnanometers,and a sheet of paper is about 100,000nanometers think.A human hair measures roughly 50,000 to100,000 nanometers in diameter, and pleasenote that your fingernails grows onenanometer every second.Itis acceptable that a picture is worth1,000 ofwords, and that a video is worth thousandof pictures.Therefore, our, I will add with thepresented

short video to further demonstrate themeaning of nano.Of course, I will give the girl in thevideo the privilege to talk on her behalf.[MUSIC]>> Hey.Do you know what nano means?It means small, very small.It is a million times smaller than thesmallest measure on a ruler.If you want to get an idea for how small ananometerreally is, you'll need to take a piece of

hair from your head.Go on, it won't hurt.Got it.Now, take a good, close look at thatstrand of hair.Not much to look at, is it?If we were to shrink you down, smallerthan the smallest thing you can see withthenaked eye, you will find that your pieceof hair starts to look a lot moreinteresting.You are now about the size of a red blood

cell.Your strand of hair is a massive treecompared to you.Even at this size, you're still about 1000times too big to be considered nano.To get you down to the nano scale, wewill have to shrink you to about 100nanometers tall.Hey, where are all the lights?You are now smaller


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than the wavelength of visible light.You are practically invisible.But for the sake of demonstration, I thinkwe should turn on some lights.At this size, the red blood cell is 1,000times bigger than you are.It is like an enormous stadium.Welcome to the nanoscale.You could probably hold the common coldvirus in your hands quite comfortably now.The rhinovirus is only about 30 nanometersacross, and is nearly impossible to seenext to the red blood cell.A red blood cell is too big to beconsidered nano.However, it's made up of all kinds ofnanomaterials.If you were to look close enough, youwould see that theouter walls of the cell are stabilized bya flexible mesh-like protein skeleton.The bars and connectors that make upthis mesh are considered part of ananomaterial.

Without these reinforcing nanostructures,the cell would bemuch more fragile, and not nearly asflexible.It wouldn't stand a chance in your body.Everything is made up of nanomaterials.Nanomaterials are an arrangement ofmoleculesand atoms that, when combined createstablebuilding blocks that can be madeinto larger, more complex materials andstructures.

>> After this demonstration I will giveright now anexample for the importance ofminiaturization ability of thenanotechnology.A such example, let's have a look on howcellphones developed from the bulky walkietalkie to today's miniaturizedarchitecture.In 1985 mobile phones used to look huge insize and with a pretty long antenna.On the other hand in present we have the

smartphones which are becoming acomputer, GPS, radio, and actually ourlifeline to the Internet.And to still be able to fit our pockets.With the help of nanotechnology, mobilephones willbe further evolved in terms of theirperformance, and features.And would include for example, augmentedreality, flexible screens,


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in built projector, seamless voicecontrol, three-dimensional screensand holograms, and of course it mightinclude also remote medical diagnosisfeatures and many, many more features.Nanotechnology in one sense is the naturalcontinuation ofthe evolution that we have witnessed overthe last decade.Where millionth of a meter electronics,whichwe call usually micro electronics, becamecommonplace.Thus enabling the construction of higherquality of materials and devices andmany more applications on equivalent oreven smaller areas than wehave knew previously.So far, the miniaturization ability of themicroelectronics allow theintegration or placement of thousands ofchips into an equivalent area.Further miniaturization with the help ofnanotechnology

would allow putting millions of currentlyavailableelectronic devices over an area that isless that few millimeters over fewmillimeters.In a constituent example, a team from theTechnion Israel Institute of Technologyleveraged the power of nanotechnology toengraveall the content of the Old Testamenton a piece of silicon that is less thanone millimeter by one millimeter,as could be seen by the image in the

bottom right of the screen.One of the parameters that is directlyconnected with theminiaturization and nano technology istermed surface to volume ratio.This parameter is of fundamentalimportance in theapplications involving chemical catalysisand nucleation of physical processes.Usually, surface area to volume ratioincreases with adecrease in characteristic dimensions ofthe material, and vice versa.

Therefore as the material size decreases,a greater portion of the atoms are foundon the surface compared to those found inthe bulk or inside the same material.As growth and catalytic chemical reactionoccurs atthe surfaces, therefore a given mass ofnanomaterial will be much morereactive than the same mass of materialmade up of larger particles.


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It is also found that materials which areinert in their bulkfrom form a reactive whenproduced in their nanoscale form.And therefore they can improvetheir properties.To demonstrate the relationship betweenthe miniaturizationof the materials and the surface to volumeratio, let's consider a cube made of asilicon with a characteristic size of tennanometers.In this case, the number of the unit cellsin this nanocube is estimated by 6,250,which is actually equivalent to to fif, to50,000 atoms.On the other hand, the number of the unitcells that are located oneach face is 340, thus resulting in 680atoms on each face ofthe nanocube, and 4,080 atoms on all facesof the nanocube.Dividing the number of the atoms availableon the surface of the

nanocube, namely 4080 atoms, by the numberof the atoms available in all partsof the nanocube, which is basically 50,000atoms, brings to the conclusion thataround 10% of the atoms in the nanocubeare located on the surface.On the other hand if we applied a similarconsideration with a piece of silicon often square centimeters and the thicknessof one micrometer.This leads to the conclusion that only0.03% of thesilicon atoms in this structure are

available on the surface.Therefore, nanomaterials have a muchgreater surfacearea per unit volume compared with thelarger particles.Actually this leads to nanoparticles thatare more chemically reactive.This is so because the molecules at thesurface of the material don't have fullallocation of covalent bonds and are inenergetically unstable states.Since many more molecules are located onthe surface are in energetically unstable

states, nanomaterials are more reactivecompared tothe microscale or to the macroscalematerials.With the higher reactivity almost alltypes of nanomaterials are capableof catalyzing reactions and freenanomaterialstend to agglomerate into bigger particles.On to the specific physical and chemical


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properties ofthe nanoparticles there are expect,expected to interact withsubstances such as proteins, lipids,carbohydrates, and nucleic acidsthat present in food, biological, orduring desalination processes.Other applications of such feature includedrugdelivery, clothing insulation, and many,many more.With this, we come now to the end of classnumber one, session number one.Thank you.

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2 - 1 - 1.1 Definitions and Nanomaterials [15_36]