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Thread: Carbon Nanotubes

  1. #1
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    Carbon Nanotubes

    I was watching Sci Fi Science with Michio Kaku last night and he visited an MIT professor working on Nanotubes who pulled out what appeared to be a ~ 4'x20' thin sheet of nanotubes professed to be stronger than steel. I had no idea we were that far along with constructing nanotubes, how long before that space elevator?

    http://science.discovery.com/videos/...cience-videos/

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    yes, nanotechnology is exploding..
    it is amazing at what is happening the industry...
    carbon nanostructures can be grown, they have very unique properties in the electrical field and can be used as semiconductors.
    computers with nanodiamond substrates can already be grown in the lab.
    the cost is going down very quickly.
    we will soon have CPU chips that are far more powerful, use way less energy and can withstand incredible tempature varations (unlike silicone based chips)

    these processors will be on the order of magnitudes smaller than current processor etchings..

    nanotube radios can already pick up and recieve radio frequencies. they are tuned based on their architure. and small enought that they can in theory fit inside of the neurons in your brain.

    i can see people having direct access to wireless network resources through neural connections..

    full computers, audio and video recorders, and laser projectors will be able to be printed on the surface of a contact lens..

    nanotubes can be used as optical light antennas, we can have the technology to capture images photon by photon on nanotube plates. it is not unreasonable to have cameras that are the equivilent to gigapixel or even terapixels in size..

    better sensitivity to a much wider portion of the electromagnetic spectrum will be realized giving better solutions to the way light information is processed and understood.

    the nano world is really marching on and we are within a decade of having nanotechnology replace silicone in computers..

    i still think we are a ways away from the space elevator though.

    but maybe with new more powerful computers, the space elevator will come quicker.

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    Quote Originally Posted by peledre View Post
    I was watching Sci Fi Science with Michio Kaku last night and he visited an MIT professor working on Nanotubes who pulled out what appeared to be a ~ 4'x20' thin sheet of nanotubes professed to be stronger than steel. I had no idea we were that far along with constructing nanotubes, how long before that space elevator?

    http://science.discovery.com/videos/...cience-videos/
    I still think it will be decades till we can make structures on the order of 100+ kilometers made of nanomaterials.
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    Are nano-structures a health hazard?

    Will the detritus from nanotubes and other nano-structures create a health hazard similar in scope to that caused by asbestos? Someone told me that nano-structures can go right through walls of an animal cell.

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    Quote Originally Posted by tashirosgt View Post
    Will the detritus from nanotubes and other nano-structures create a health hazard similar in scope to that caused by asbestos? Someone told me that nano-structures can go right through walls of an animal cell.
    actually, this is a very real concern and the EPA is looking into the effects of nanosubstrates in the envirnment.

    but like processors aad other materials where the structures are locked within another structure, (i am thinking of an example like a CPU, the envirnmental helth risk is minimal.

    it is the free particules that pose the most risk.
    there is concern that nanoparticules in beauty products and the like are the most risky..

    cause once they are in an environment, they are really really really hard to get rid of..


    http://neat.ucdavis.edu/

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    Quote Originally Posted by tashirosgt View Post
    Will the detritus from nanotubes and other nano-structures create a health hazard similar in scope to that caused by asbestos? Someone told me that nano-structures can go right through walls of an animal cell.
    Airborne carbon nanotubes can cause lung fibrosis in rodent models:

    A review of carbon nanotube toxicity and assessment of potential occupational and environmental health risks.
    Lam CW, James JT, McCluskey R, Arepalli S, Hunter RL.
    J Toxicol Environ Health A. 2010 Jan;73(5):410-22.
    Abstract:
    Nanotechnology has emerged at the forefront of science research and technology development. Carbon nanotubes (CNTs) are major building blocks of this new technology. They possess unique electrical, mechanical, and thermal properties, with potential wide applications in the electronics, computer, aerospace, and other industries. CNTs exist in two forms, single-wall (SWCNTs) and multi-wall (MWCNTs). They are manufactured predominately by electrical arc discharge, laser ablation and chemical vapor deposition processes; these processes involve thermally stripping carbon atoms off from carbon-bearing compounds. SWCNT formation requires catalytic metals. There has been a great concern that if CNTs, which are very light, enter the working environment as suspended particulate matter (PM) of respirable sizes, they could pose an occupational inhalation exposure hazard. Very recently, MWCNTs and other carbonaceous nanoparticles in fine (<2.5 microm) PM aggregates have been found in combustion streams of methane, propane, and natural-gas flames of typical stoves; indoor and outdoor fine PM samples were reported to contain significant fractions of MWCNTs. Here we review several rodent studies in which test dusts were administered intratracheally or intrapharyngeally to assess the pulmonary toxicity of manufactured CNTs, and a few in vitro studies to assess biomarkers of toxicity released in CNT-treated skin cell cultures. The results of the rodent studies collectively showed that regardless of the process by which CNTs were synthesized and the types and amounts of metals they contained, CNTs were capable of producing inflammation, epithelioid granulomas (microscopic nodules), fibrosis, and biochemical/toxicological changes in the lungs. Comparative toxicity studies in which mice were given equal weights of test materials showed that SWCNTs were more toxic than quartz, which is considered a serious occupational health hazard if it is chronically inhaled; ultrafine carbon black was shown to produce minimal lung responses. The differences in opinions of the investigators about the potential hazards of exposures to CNTs are discussed here. Presented here are also the possible mechanisms of CNT pathogenesis in the lung and the impact of residual metals and other impurities on the toxicological manifestations. The toxicological hazard assessment of potential human exposures to airborne CNTs and occupational exposure limits for these novel compounds are discussed in detail. Environmental fine PM is known to form mainly from combustion of fuels, and has been reported to be a major contributor to the induction of cardiopulmonary diseases by pollutants. Given that manufactured SWCNTs and MWCNTs were found to elicit pathological changes in the lungs, and SWCNTs (administered to the lungs of mice) were further shown to produce respiratory function impairments, retard bacterial clearance after bacterial inoculation, damage the mitochondrial DNA in aorta, increase the percent of aortic plaque, and induce atherosclerotic lesions in the brachiocephalic artery of the heart, it is speculated that exposure to combustion-generated MWCNTs in fine PM may play a significant role in air pollution-related cardiopulmonary diseases. Therefore, CNTs from manufactured and combustion sources in the environment could have adverse effects on human health.

    Unusual inflammatory and fibrogenic pulmonary responses to single-walled carbon nanotubes in mice.

    Shvedova AA, Kisin ER, Mercer R, Murray AR, Johnson VJ, Potapovich AI, Tyurina YY, Gorelik O, Arepalli S, Schwegler-Berry D, Hubbs AF, Antonini J, Evans DE, Ku BK, Ramsey D, Maynard A, Kagan VE, Castranova V, Baron P.
    Am J Physiol Lung Cell Mol Physiol. 2005 Nov;289(5):L698-708. Epub 2005 Jun 10.
    Abstract:
    Single-walled carbon nanotubes (SWCNT) are new materials of emerging technological importance. As SWCNT are introduced into the life cycle of commercial products, their effects on human health and environment should be addressed. We demonstrated that pharyngeal aspiration of SWCNT elicited unusual pulmonary effects in C57BL/6 mice that combined a robust but acute inflammation with early onset yet progressive fibrosis and granulomas. A dose-dependent increase in the protein, LDH, and gamma-glutamyl transferase activities in bronchoalveolar lavage were found along with accumulation of 4-hydroxynonenal (oxidative biomarker) and depletion of glutathione in lungs. An early neutrophils accumulation (day 1), followed by lymphocyte (day 3) and macrophage (day 7) influx, was accompanied by early elevation of proinflammatory cytokines (TNF-alpha, IL-1beta; day 1) followed by fibrogenic transforming growth factor (TGF)-beta1 (peaked on day 7). A rapid progressive fibrosis found in mice exhibited two distinct morphologies: 1) SWCNT-induced granulomas mainly associated with hypertrophied epithelial cells surrounding SWCNT aggregates and 2) diffuse interstitial fibrosis and alveolar wall thickening likely associated with dispersed SWCNT. In vitro exposure of murine RAW 264.7 macrophages to SWCNT triggered TGF-beta1 production similarly to zymosan but generated less TNF-alpha and IL-1beta. SWCNT did not cause superoxide or NO.production, active SWCNT engulfment, or apoptosis in RAW 264.7 macrophages. Functional respiratory deficiencies and decreased bacterial clearance (Listeria monocytogenes) were found in mice treated with SWCNT. Equal doses of ultrafine carbon black particles or fine crystalline silica (SiO2) did not induce granulomas or alveolar wall thickening and caused a significantly weaker pulmonary inflammation and damage
    Nick

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    Quote Originally Posted by tashirosgt View Post
    Will the detritus from nanotubes and other nano-structures create a health hazard similar in scope to that caused by asbestos? Someone told me that nano-structures can go right through walls of an animal cell.
    I think it is an open question and I highly doubt that the answer will be a blanket statement for all nanomaterials. I suspect it will depend upon the composition of the material, its size, possibly its morphology/shape, and maybe even things like the surface composition of the particles. For example, with asbestos, different crystallographies have different toxicities.

    And even if true for a certain material, it doesn't mean that it will not be a usable technology, it just means that things will have to be done to control exposure in both its manufacturing and use.
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    Quote Originally Posted by Swift View Post
    I think it is an open question and I highly doubt that the answer will be a blanket statement for all nanomaterials. I suspect it will depend upon the composition of the material, its size, possibly its morphology/shape, and maybe even things like the surface composition of the particles. For example, with asbestos, different crystallographies have different toxicities.

    And even if true for a certain material, it doesn't mean that it will not be a usable technology, it just means that things will have to be done to control exposure in both its manufacturing and use.

    And better to be considering the issues now before the technology becomes ubiquitous.

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    Quote Originally Posted by Garrison View Post
    And better to be considering the issues now before the technology becomes ubiquitous.
    And, in fact, we're already behind. There was a small article about this very problem in a recent issue of Chemical & Engineering News (I can try to search out a link if anyone is very interested).

    Nanomaterials are actually already in fairly widespread use. We're just not making Space Elevators with them, just more mundane stuff like abrasives. And there are naturally occurring materials, such as in soot.

    One of the problems with them is that the technology to even characterize them (fundamental things like particle size) have only recently been developed.

    And one of their special characteristics, the fact that their chemical and other properties are different than the bulk materials (nano-carbon for example, is different than other forms of carbon in many fundamental physical properties) means that we have to remeasure all the environmental and safety issues of them, and such studies are extremely non-trivial and take a very long time.
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    Quote Originally Posted by peledre View Post
    ...who pulled out what appeared to be a ~ 4'x20' thin sheet of nanotubes professed to be stronger than steel.
    http://science.discovery.com/videos/...cience-videos/
    Unfortunately that's not too impressive. I have glue that when it dries is stronger than steel, my friendly neighborhood spiders make silk that is stronger than steel every day and in some countries bike shops sell kevlar tyres that are stronger than steel. Strong as diamond objects meters in length, now that would be impressive.

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    Quote Originally Posted by sarongsong View Post
    That's questionable.
    I tend to think this thread is all about the advancement in size that they have been able to accomplish. (unless I missed something in the other threads)

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    On the subject of planar or "pseudo-planar" molecules--it has long been speculated that molecules that contain a Benzenoid moiety are toxic partially due to their planarity... e.g. polycyclicaromatic hydrocarbons as most of us know are a part of the lore for the basis of life on Earth---but that is another question entirely

    Wiki on PAH

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    Anyone interested in carbon nanotubes and toxicity, might be interested in this commentary from the January-February 2010 issue of Materials Today ( Vol 13, # 1-2, p 6). Unfortunately, you have to register to read it, but I think that's free.
    The first issue that we address and justify in this paper is the pejorative and provocative tone of the title; the contradictory data on the toxic effects of single-walled carbon nanotubes (SWCNT) make us believe that it is appropriate and necessary.
    They have an interesting table of 8 studies that have looked at toxicity and found contradictory results - but there are a lot of differences in the CNTs used, how they were treated, the cell lines used in the studies, the conditions, the tests conducted, and even in the definition of "toxic".
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    I imagine that inhaling carbon nanotubes wouldn't be much different than inhaling coal dust. Not very healthy for your lungs.

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    Quote Originally Posted by TampaDude View Post
    I imagine that inhaling carbon nanotubes wouldn't be much different than inhaling coal dust. Not very healthy for your lungs.
    Actually, I do not believe that coal dust is a good analogy.

    As I understand it, the vast majority of the toxicity of coal dust is not from the coal itself, but from the crystalline silicas/quartz (crushed rocks) that get mixed with the coal dust. Coal is also a pretty dirty material, with lots of metals, sulfates, etc. in it.

    Carbon nanotubes will be essentially pure carbon. And, in the article I referenced above, even subtle changes to the surface treatment of the nanotubes had a big effect on toxicity.
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    Quote Originally Posted by Swift View Post
    Actually, I do not believe that coal dust is a good analogy.

    As I understand it, the vast majority of the toxicity of coal dust is not from the coal itself, but from the crystalline silicas/quartz (crushed rocks) that get mixed with the coal dust. Coal is also a pretty dirty material, with lots of metals, sulfates, etc. in it.

    Carbon nanotubes will be essentially pure carbon. And, in the article I referenced above, even subtle changes to the surface treatment of the nanotubes had a big effect on toxicity.
    I still wouldn't want to inhale that stuff, though (lights cigarette).

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    Carbon 12

    What is it about the atomic structure of carbon that suits it to nanotechnology?

    With carbon having 12 particles in the nucleus, is there something about a twelve particle atomic weight that enables nanotechnology?

    I'm thinking by geometric analogy, that a sphere is surrounded by twelve spheres. Does the carbon atomic nucleus form a hollow sphere?

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    The nucleus doesn't affect carbon's ability to from bonds, it's having four electrons in its outer "shell" that lets it form so many compounds. Four outer electrons lets it make four bonds. For example, it can bond with four hydrogen atoms to make CH4 or methane.

    The wikipedia page on carbon might help: http://en.wikipedia.org/wiki/Carbon

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    http://en.wikipedia.org/wiki/Carbon_nanotube has a good picture of the hexagonal molecular shape of a carbon nanotube, in which each atom links to three neighbouring atoms. This doesn't seem to match the 4 electron shell linkage of methane. Is the carbon nucleus a hollow sphere?
    Last edited by Robert Tulip; 2010-Mar-05 at 10:48 AM. Reason: typo: three atoms not two

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    Quote Originally Posted by Ronald Brak View Post
    The nucleus doesn't affect carbon's ability to from bonds, it's having four electrons in its outer "shell" that lets it form so many compounds. Four outer electrons lets it make four bonds. For example, it can bond with four hydrogen atoms to make CH4 or methane.
    The other thing about the four bonding electrons of carbon is that carbon is very good at bonding to itself, and those bonds can be single bonds (2 shared electrons), double bonds (4 electrons), or triple bonds (6 electrons), not to mention the aromatic bonding found in things like benzene.

    Quote Originally Posted by Robert Tulip View Post
    http://en.wikipedia.org/wiki/Carbon_nanotube has a good picture of the hexagonal molecular shape of a carbon nanotube, in which each atom links to two neighbouring atoms. This doesn't seem to match the 4 electron shell linkage of methane. Is the carbon nucleus a hollow sphere?
    I'm not sure why you think the nucleus is hollow - it isn't, and that doesn't explain what is happening here.

    In a carbon nanotube (as in materials like graphite), each carbon atom is actually bonded to three other carbon atoms. The fourth "bond" is actually "smeared" around all atoms - and this sort of shared bond leads to the property called aromaticity (aromatic bonding).

    Start with the old fashioned view of benzene. Each carbon has four bonds, one each to a neighboring carbon, one to a hydrogen, and what is represented as a double bond to one of the two carbon atoms. But this alternating single/double bond around the ring is not correct, and a better model is that the three double bonds are shared equally around the ring (good explanation of all of this).

    To make graphite, imagine that you took that benzene, removed the hydrogens, and used those extra bonding electrons so that the benzene rings can bond to each other. You get a structure with a sheet of carbon atoms in 6 atom rings. Within a sheet of these rings, the atoms are very strongly bonded to each other, and if you stack the sheets up, there is only very weak bonding between the sheets. That's why graphite has a layered structure.

    Now, take one graphite sheet and roll it up into a tube. That essentially is a carbon nanotube.
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    Quote Originally Posted by Robert Tulip View Post
    What is it about the atomic structure of carbon that suits it to nanotechnology?
    By the by, carbon is very far from the only material or atom being used in nanotechnology.
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    Quote Originally Posted by Swift View Post
    The other thing about the four bonding electrons of carbon is that carbon is very good at bonding to itself, and those bonds can be single bonds (2 shared electrons), double bonds (4 electrons), or triple bonds (6 electrons), not to mention the aromatic bonding found in things like benzene.
    I'm not sure why you think the nucleus is hollow - it isn't, and that doesn't explain what is happening here.
    In a carbon nanotube (as in materials like graphite), each carbon atom is actually bonded to three other carbon atoms. The fourth "bond" is actually "smeared" around all atoms - and this sort of shared bond leads to the property called aromaticity (aromatic bonding).
    Start with the old fashioned view of benzene. Each carbon has four bonds, one each to a neighboring carbon, one to a hydrogen, and what is represented as a double bond to one of the two carbon atoms. But this alternating single/double bond around the ring is not correct, and a better model is that the three double bonds are shared equally around the ring (good explanation of all of this).
    To make graphite, imagine that you took that benzene, removed the hydrogens, and used those extra bonding electrons so that the benzene rings can bond to each other. You get a structure with a sheet of carbon atoms in 6 atom rings. Within a sheet of these rings, the atoms are very strongly bonded to each other, and if you stack the sheets up, there is only very weak bonding between the sheets. That's why graphite has a layered structure.
    Now, take one graphite sheet and roll it up into a tube. That essentially is a carbon nanotube.
    Thanks Swift for the simple explanation. I didn't know a carbon nanotube was a rolled up sheet of graphite.

    The reason I ask about a spherical nucleus is that carbon 12 has six protons and six neutrons. If the protons and neutrons are spherical, then the tightest way they can pack would seem to be a duodecahedral sphere, like the stack of spheres I linked to earlier, if they are equal in size. A proton mass is 1.672621637(83)×10−27 kg while a neutron mass is 1.67492729(28)×10−27 kg. Is this slight difference of mass enough to mean the nucleus is not spherical?

    http://www.windows.ucar.edu/tour/lin...c_nucleus.html says "one way of thinking about an atomic nucleus [is] as a cluster of tightly packed "balls"." I'm just wondering how true this is, and whether protons and neutrons stack with each other as equal sized spheres. If the carbon 12 nucleus is 'a cluster of tightly packed balls', the tightest pack formation would seem to be a hollow sphere. Or would a central sphere with eleven others distributed around it be tighter? I'm not at all wanting to defend this as a proposition, just explaining why I ask the question.

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    I think it is not correct to think of protons and neutrons as rigid spheres and how they pack into a nucleus as some sort of stacking of hard spheres.

    The wikipedia article on nuclear structure might be a good place to start to read about some of the models of this structure. This is an even more technical discussion from San Jose State - I like this quote: "These models are not mutually exclusive. Each may capture an element of nuclear structure." But my take on that quote is that each of those models is probably also incomplete.
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    New research on carbon nanotubes

    From R&D Magazine
    A team of Swedish and American scientists has shown for the first time that carbon nanotubes can be broken down by an enzyme—myeloperoxidase (MPO)—found in white blood cells. Their discoveries are presented in Nature Nanotechnology and contradict what was previously believed, that carbon nanotubes are not broken down in the body or in nature.
    This could be very good news for toxicity concerns about carbon nanotubes.
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    Quote Originally Posted by Swift View Post
    From R&D Magazine

    This could be very good news for toxicity concerns about carbon nanotubes.
    This could be a case of the cure being worse than the disease. Myeloperoxidase is produced by neutrophils, a type of immune cell. When activated,they undergo a process called a respiratory burst, which produces a bunch of toxic products, including hypochlorous acid, which is made by neutrophil myeloperoxidase. Basically, an activated neutrophil is your body's way of sending a suicide truck bomb into an infected area.

    Nick

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