Nano-tehnologija

1

Nano-tehnologija

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

When it comes to taking the next "giant leap" in space exploration, NASA is thinking small -- really small.
n laboratories around the country, NASA is supporting the burgeoning science of nanotechnology. The basic idea is to learn to deal with matter at the atomic scale -- to be able to control individual atoms and molecules well enough to design molecule-size machines, advanced electronics and "smart" materials.

If visionaries are right, nanotechnology could lead to robots you can hold on your fingertip, self-healing spacesuits, space elevators and other fantastic devices. Some of these things may take 20+ years to fully develop; others are taking shape in the laboratory today.

Thinking Small

Simply making things smaller has its advantages. Imagine, for example, if the Mars rovers Spirit and Opportunity could have been made as small as a beetle, and could scurry over rocks and gravel as a beetle can, sampling minerals and searching for clues to the history of water on Mars. Hundreds or thousands of these diminutive robots could have been sent in the same capsules that carried the two desk-size rovers, enabling scientists to explore much more of the planet's surface -- and increasing the odds of stumbling across a fossilized Martian bacterium!

But nanotech is about more than just shrinking things. When scientists can deliberately order and structure matter at the molecular level, amazing new properties sometimes emerge.

An excellent example is that darling of the nanotech world, the carbon nanotube. Carbon occurs naturally as graphite -- the soft, black material often used in pencil leads -- and as diamond. The only difference between the two is the arrangement of the carbon atoms. When scientists arrange the same carbon atoms into a "chicken wire" pattern and roll them up into miniscule tubes only 10 atoms across, the resulting "nanotubes" acquire some rather extraordinary traits. Nanotubes:

* have 100 times the tensile strength of steel, but only 1/6 the weight;

* are 40 times stronger than graphite fibers;

* conduct electricity better than copper;

* can be either conductors or semiconductors (like computer chips), depending on the arrangement of atoms;

* and are excellent conductors of heat.

Much of current nanotechnology research worldwide focuses on these nanotubes. Scientists have proposed using them for a wide range of applications: in the high-strength, low-weight cable needed for a space elevator; as molecular wires for nano-scale electronics; embedded in microprocessors to help siphon off heat; and as tiny rods and gears in nano-scale machines, just to name a few.

Nanotubes figure prominently in research being done at the NASA Ames Center for Nanotechnology (CNT). The center was established in 1997 and now employs about 50 full-time researchers.

"[We] try to focus on technologies that could yield useable products within a few years to a decade," says CNT director Meyya Meyyappan. "For example, we're looking at how nano-materials could be used for advanced life support, DNA sequencers, ultra-powerful computers, and tiny sensors for chemicals or even sensors for cancer."

A chemical sensor they developed using nanotubes is scheduled to fly a demonstration mission into space aboard a Navy rocket next year. This tiny sensor can detect as little as a few parts per billion of specific chemicals--like toxic gases--making it useful for both space exploration and homeland defense. CNT has also developed a way to use nanotubes to cool the microprocessors in personal computers, a major challenge as CPUs get more and more powerful. This cooling technology has been licensed to a Santa Clara, California, start-up called Nanoconduction, and Intel has even expressed interest, Meyyappan says.

Designing the future

If these near-term uses of nanotechnology seem impressive, the long-term possibilities are truly mind-boggling.

The NASA Institute for Advanced Concepts (NIAC), an independent, NASA-funded organization located in Atlanta, Georgia, was created to promote forward-looking research on radical space technologies that will take 10 to 40 years to come to fruition.

For example, one recent NIAC grant funded a feasibility study of nanoscale manufacturing--in other words, using vast numbers of microscopic molecular machines to produce any desired object by assembling it atom by atom!

That NIAC grant was awarded to Chris Phoenix of the Center for Responsible Nanotechnology.

In his 112 page report, Phoenix explains that such a "nanofactory" could produce, say, spacecraft parts with atomic precision, meaning that every atom within the object is placed exactly where it belongs. The resulting part would be extremely strong, and its shape could be within a single atom's width of the ideal design. Ultra-smooth surfaces would need no polishing or lubrication, and would suffer virtually no "wear and tear" over time. Such high precision and reliability of spacecraft parts are paramount when the lives of astronauts are at stake.

Although Phoenix sketched out some design ideas for a desktop nanofactory in his report, he acknowledges that -- short of a big-budget "Nanhatten Project," as he calls it -- a working nanofactory is at least a decade away, and possibly much longer.

Taking a cue from biology, Constantinos Mavroidis, director of the Computational Bionanorobotics Laboratory at Northeastern University in Boston, is exploring an alternative approach to nanotech: Rather than starting from scratch, the concepts in Mavroidis's NIAC-funded study employ pre-existing, functional molecular "machines" that can be found in all living cells: DNA molecules, proteins, enzymes, etc.

Shaped by evolution over millions of years, these biological molecules are already very adept at manipulating matter at the molecular scale -- which is why a plant can combine air, water, and dirt and produce a juicy red strawberry, and a person's body can convert last night's potato dinner into today's new red blood cells. The rearranging of atoms that makes these feats possible is performed by hundreds of specialized enzymes and proteins, and DNA stores the code for making them.

Making use of these "pre-made" molecular machines -- or using them as starting points for new designs -- is a popular approach to nanotechnology called "bio-nanotech."

"Why reinvent the wheel?" Mavroidis says. "Nature has given us all this great, highly refined nanotechnology inside of living things, so why not use it -- and try to learn something from it?"

The specific uses of bio-nanotech that Mavroidis proposes in his study are very futuristic. One idea involves draping a kind of "spider's web" of hair-thin tubes packed with bio-nanotech sensors across dozens of miles of terrain, as a way to map the environment of some alien planet in great detail. Another concept he proposes is a "second skin" for astronauts to wear under their spacesuits that would use bio-nanotech to sense and respond to radiation penetrating the suit, and to quickly seal over any cuts or punctures.

Futuristic? Certainly. Possible? Maybe. Mavroidis admits that such technologies are probably decades away, and that technology so far in the future will probably be very different from what we imagine now. Still, he says he believes it's important to start thinking now about what nanotechnology might make possible many years down the road.

Considering that life itself is, in a sense, the ultimate example of nanotech, the possibilities are exciting indeed.
Ovde



Registruj se da bi učestvovao u diskusiji. Registrovanim korisnicima se NE prikazuju reklame unutar poruka.
offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

By combining one natural component of a cell with the synthetic analog of another component, researchers at the University of California, Santa Barbara, have created a nanoscale hybrid they call the "smart bio-nanotube": a novel structure that could one day become a vehicle for ultra-precise drug or therapeutic gene delivery.

The nanotubes are "smart" because they can open or close at the ends, depending on how the researchers manipulate the electric charge on the two components. So in principle, a nanotube could encapsulate a drug or a gene, and then open on command to deliver the cargo where it would have the best effect.

The tube's components play roles similar to skin and bone. The "skin" is a soap-bubble-like arrangement of molecules known as a lipid bilayer, akin to the bilayer that forms the cell's protective outer membrane. The "bone" is a hollow, cylindrical structure known as a microtubule, which is ubiquitous in the cell's internal cytoskeleton, the system of nanoscale struts and girders it uses for internal transport, structural stability and many other purposes. The researchers have found that when they combine the two components and control the conditions properly, open or closed bio-nanotubes will assemble themselves spontaneously.

The discovery resulted from a collaboration between the laboratories of UCSB materials scientist Cyrus R. Safinya, and UCSB biochemist Leslie Wilson. Their work was funded by the National Science Foundation's biomaterials program and is reported in the Aug. 9 issue of The Proceedings of the National Academy of Sciences. The report also appeared on-line in the PNAS Early Edition.
Ovde



offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

UCLA chemists have created the first nano valve that can be opened and closed at will to trap and release molecules. The discovery, federally funded by the National Science Foundation, will be published July 19 in the Proceedings of the National Academy of Sciences.
"This paper demonstrates unequivocally that the machine works," said Jeffrey I. Zink, a UCLA professor of chemistry and biochemistry, a member of the California NanoSystems Institute at UCLA, and a member of the research team. "With the nano valve, we can trap and release molecules on demand. We are able to control molecules at the nano scale.

"A nano valve potentially could be used as a drug delivery system," Zink said.

"The valve is like a mechanical system that we can control like a water faucet," said UCLA graduate student Thoi Nguyen, lead author on the paper. "Trapping the molecule inside and shutting the valve tightly was a challenge. The first valves we produced leaked slightly."

"Thoi was a master nano plumber who plugged the leak with a tight valve," Zink said.

This nano valve consists of moving parts — switchable rotaxane molecules that resemble linear motors designed by California NanoSystems Institute director Fraser Stoddart's team — attached to a tiny piece of glass (porous silica), which measures about 500 nanometers, and which Nguyen is currently reducing in size. Tiny pores in the glass are only a few nanometers in size.

"It's big enough to let molecules in and out, but small enough so that the switchable rotaxane molecules can block the hole," Zink said.

The valve is uniquely designed so one end attaches to the opening of the hole that will be blocked and unblocked, and the other end has the switchable rotaxanes whose movable component blocks the hole in the down position and leaves it open in the up position. The researchers used chemical energy involving a single electron as the power supply to open and shut the valve, and a luminescent molecule that allows them to tell from emitted light whether a molecule is trapped or has been released.

Switchable rotaxanes are molecules composed of a dumbbell component with two stations between which a ring component can be made to move back and forth in a linear fashion. Stoddart, who holds UCLA's Fred Kavli Chair in nanosystems sciences, has already shown how these switchable rotaxanes can be used in molecular electronics. Stoddart's team is now adapting them for use in the construction of artificial molecular machinery.

"The fact that we can take a bistable molecule that behaves as a switch in a silicon-based electronic device at the nanoscale level and fabricate it differently to work as part of a nano valve on porous silica is something I find really satisfying about this piece of research," Stoddart, said. "It shows that these little pieces of molecular machinery are highly adaptable and resourceful, and means that we can move around in the nanoworld with the same molecular tool kit and adapt it to different needs on demand."

In future research, they will test how large a hole they can block, to see whether they can get larger molecules, like enzymes, inside the container; they are optimistic.

The research team also includes Hsian-Rong Tseng, a former postdoctoral scholar in chemistry who is now an assistant professor of molecular and medical pharmacology in UCLA's David Geffen School of Medicine; Paul Celestre, a former undergraduate student in Stoddart's laboratory; Amar Flood, a former UCLA researcher in Stoddart's supramolecular chemistry group who is now an assistant professor of chemistry at Indiana University; and Yi Liu, a former UCLA graduate student who is now a postdoctoral scholar at the Scripps Research Institute in La Jolla.

"Our team and Fraser's have very different areas of expertise," Zink said. "By combining them and working together we were able to make something new that really works."

Stoddart has noted that it is only in the past 100 years that humankind has learned how to fly. Prior to the first demonstration of manned flight, there were many great scientists and engineers who said it was impossible.

"Building artificial molecular machines and getting them to operate is where airplanes were a century ago," Stoddart said. "We have come a long way in the last decade, but we have a very, very long way to go yet to realize the full potential of artificial molecular machines."

The nano valve is much smaller than living cells. Could a cell ingest a nano valve combined with bio-molecules, and could light energy then be used to release a drug inside a cell? Stay tuned.
Ovde

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

A new form of water has been discovered by physicists in Argonne's Intense Pulsed Neutron Source (IPNS) Division. Called nanotube water, these molecules contain two hydrogen atoms and one oxygen atom but do not turn into ice - even at temperatures near absolute zero.
Instead, inside a single wall tube of carbon atoms less than 2 nanometers, or 2 billionths of a meter wide, the water forms an icy, inner wall of water molecules with a chain of liquid-like water molecules flowing through the center. This occurs at 8 Kelvins, which is minus 509 Fahrenheit. As the temperature rises closer to room temperature, the nanotube water gradually becomes liquid.

Researchers ranging from biologists to geologists and materials scientists are interested in water's behavior in tightly confined spaces controlled by hydrophobic - water repulsing - materials because this situation is found in nature, for example when tiny roots carry water to plants. Some membrane proteins also face this challenge, including aquaporin, which controls water flow through cell walls.

This IPNS study is the first experiment with water in a nanotube. "I was surprised," said principal investigator Alexander Kolesnikov, "that no one has tried testing water in nanotubes. There have been a large number of calculations, made even more difficult because water is so difficult to model, but no experimental work."

"Even though people have been modeling water for decades," said visiting scientist Christian J. Burnham from the University of Houston, "we are only now just beginning to appreciate the importance of including the correct quantum-level description of the motion of the hydrogen nuclei and we are still working on a more accurate mathematical description of the charge clouds enveloping each water molecule."

Researchers Kolesnikov, Chun Loong, Nicolas de Souza, Pappannan Thiyagarajan and Jean-Marc Zanotti used the IPNS for the experiments. Instruments at the IPNS study atomic arrangements and motions in liquids and solids. The IPNS is open to researchers from industry, academia and other national and international laboratories.

Research partners at MER Corp., Tucson, Ariz., supplied the nanotube samples made of nearly pure carbon only one atom thick. Each tube was 1.4 nanometers across and 10,000 nanometers long; imagine a piece of dry, hollow spaghetti 200 meters long because the nanotube is 100,000 times longer than wide.

"With this one-dimensional confinement," Kolesnikov said, "we expected something new, but not the characteristics we observed. Something extraordinary appeared."

What appeared was "totally different from bulk liquid or ice," said Kolesnikov. At 8 K, four-coordinated water molecules create an icy lining inside the naturally hydrophobic carbon nanotube. The lining free-floats inside the carbon nanotube with a 0.32 nanometer space all around it because that is as close as nature allows the water to the carbon. "An interior chain is running inside the lining, but compared to bulk water is much more mobile," Kolesnikov said.
Researchers attribute the peculiarities to the low "coordination numbers" of the molecules. In liquid water, an average of 3.8 (the coordination number) hydrogen bonds connect the molecule to its closest neighbors. In ice, four hydrogen bonds connect to its closest neighbors. In nanotube water, the number of hydrogen bonds for the chain water molecules is only 1.86.

"Because of the loose bonding, the water is very active and is always moving," Kolesnikov said. The icy lining is much more stable, but the mobile chain makes and BREAKs bonds continuously between parts of the chain and sometimes with the icy wall.

A molecular divining rod

To prepare for the experiment, the carbon nanotube sample was exposed to water vapor for several hours and dried to remove exterior water. Then researchers studied it with several neutron scattering techniques at the IPNS. Neutrons are uncharged particles found in nearly all matter. When the IPNS sends beams of neutrons through materials, they reveal a material's structural and dynamic properties.

First, researchers used the Small Angle Neutron Diffractometer to determine that water filled only the interior of the nanotube. If water were on the exterior, it would have skewed the neutron-scattering results. Other neutron diffraction techniques provided the atomic arrangement, and inelastic and quasielastic neutron scattering measurements revealed the water's molecular motions.

Next, Burnham, an expert in modeling the molecular dynamics of water, developed the simulation that shows how the new form of water behaves in the nanotube.

The small scale of the materials was an advantage in creating the simulation, making it much faster in comparison to the simulation of, for instance, a biological structure thousands of times larger and more complex.

Another advantage, according to Kolesnikov, is that scientists from other disciplines will be able to isolate water's behavior in this one-dimensional confinement. "In the inelastic neutron scattering experiment, the carbon is almost invisible compared to the hydrogen atoms, so you only see the water. Biologists can use our information to understand how the water behaves in their much larger, complex models," Kolesnikov said.

Funding for this research was supplied by the U.S. Department of Energy's Office of Basic Energy Sciences.

Research continues. Burnham will expand his classical molecular dynamics research to include quantum effects using parallel computing with funding from Argonne's Theory Institute. IPNS researchers plan to look at water in nanotubes with smaller diameters close in size to membrane proteins that selectively transport water. They also want to study the thermodynamic properties of nanotube water.

Kolesnikov said he has studyied water on and off during his career "because it is so critical to everyday life - here on Earth and in the planetary system."
Ovde

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

Renowned for their ability to walk up walls like miniature Spider-Men--or even to hang from the ceiling by one toe--the colorful lizards of the gecko family owe their wall-crawling prowess to their remarkable footpads. Each five-toed foot is covered with microscopic elastic hairs called setae, which are themselves split at the ends to form a forest of nanoscale fibers known as spatulas. So when a gecko steps on almost anything, these nano-hairs make such extremely close contact with the surface that they form intermolecular bonds, thus holding the foot in place.

Now, polymer scientist Ali Dhinojwala of the University of Akron and his colleagues have shown how to create a densely packed carpet of carbon nanotubes that functions like an artificial gecko foot--but with 200 times the gecko foot's gripping power. Potential applications include dry adhesives for microelectronics, information technology, robotics, space and many other fields.

The group's work was funded by the National Science Foundation, and is reported in a recent issue of the journal Chemical Communications.
Ovde

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

Radeći sa platinastim nanožicama, koje su 100 puta tanje od ljudske kose i koristeći krvne sudove kao cevovod kroz koji se provodi žica, tim naučnika iz SAD-a i Japana je predložio tehniku koja će jednog dana omogućiti lekarima da posmatraju pojedinačne ćelije mozga i obezbediti nove postupke lečenja neuroloških oštećenja kao što je Parkinsonova bolest.
Početkom jula u časopisu The Journal of Nanoparticle Research, tim naučnika sa univerziteta u Njujorku i Tokiju je objavio da su u stanju da naprave nanožicu (debljina ove žice je reda veličine jednog nanometra, a to je milijardu puta manje od metra). Ovo je najtanja žica proizvedena do sada i kao takva, mnogo je tanja i od najtanjeg krvnog suda. Upravo u ovome leži najveći značaj nanožica – one će se, bar u principu, moći provlačiti kroz krvni sistem do bilo koje tačke u telu, a da se ne zaustavi normalan protok krvi ili da se ne omete izmena hranjivih materija kroz zidove krvnih sudova. Nanožice su toliko tanke da bez poteškoća mogu da dopru i do mozga, a tu su vrlo korisne, jer registruju aktivnost svakog neurona u blizini krvnih sudova.

Sam princip rada nanožica nije nov. I do sada su lekari koristili arterijske puteve da bi kroz njih provlačili glomazne katetere pomoću kojih posmatraju specifične tačke u telu, na primer, pri proučavanju protoka krvi oko srca.

Predviđa se da će u budućnosti biti moguće u mozgu napraviti čitavu mrežu nanožica. Ta mreža mogla bi se koristiti za praćenje električne aktivnosti pojedinačnih nervnih ćelija ili malih grupa ćelija.

Ako ova tehnika proradi, a autori veruju da hoće, dovešće do revolucije u proučavanju funkcija mozga. Tehnologije koje se trenutno koriste (poziciono emisiono tomografsko skeniranje i funkcionalna nuklearna magnetna rezonanca) su dovele do značajnog pomaka u razumevanju neuroloških procesa kao što je primanje vizuelne informacije ili korišćenje jezika, ali ovo znanje je još uvek prilično nejasno i okvirno. Kada se iskoriste nanožice, dobiće se znatno jasnija slika, jer će se posmatrati pojedinačne nervne ćelije – neuroni. Nakon perioda ispitivanja tehnike, ona će se koristiti za lečenje, jer će omogućiti lekarima da precizno odrede mesto oštećenja ili bilo kakvog deformiteta na mozgu.

Nanožice se mogu koristiti ne samo kao prijemnici električnih signala u mozgu, već i kao emiteri, tako da će se primenjivati kao terapeutsko sredstvo kod Parkinsove i sličnih bolesti mozga. Direktna stimulacija pojedinih delova mozga kod bolesnika će dovesti do značajnog poboljšanja njihovog stanja, a pri tome im se neće naneti nikakva šteta.

Veliki je izazov izvesti umrežavanje mozga sa hiljadama žica. Autori veruju da će to u budućnosti biti moguće, pogotovo kad se završe ispitivanja novih provodnih polimera, koji imaju osobinu da menjaju oblik u zavisnosti od električnog polja, tako da će se sa njima moći upravljati. Ovi materijali imaju osobinu da se raspadaju bakteriološkim putem, pa se mogu koristiti za proizvodnju vremenski ograničenih moždanih implantata. Dodatna prednost ovih materijala je da će žice proizvedene od njih biti 20 do 30 puta tanje od platinastih.

Najznačajniji rezultati nanotehnologije vezani su za razvoj računara. Ovo je prvi slučaj da se nanotehnologija koristi za proučavanje mozga i uzajamnog dejstva dva neurona, a to će nam pomoći da shvatimo funkcionisanje najsavršenijeg računara – našeg mozga.
Ovde

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

Ovde kacite teme vezne za datu oblast

Dopuna: 19 Avg 2005 0:05

Carbon-nantobuse pokazuju svoju snagu u brojevima
WASHINGTON - Carbon nanotubes, the wunderkind molecules of the nanoworld, are finally showing strength in numbers. Researchers have now made large nanotube sheets that have many of the same star qualities as the prima donna-like single molecules, bringing the promises of nanotechnology a step closer to reality.

The flexible, transparent sheets can conduct electricity and emit light or heat when a voltage is applied, leading their creators to propose that our car windows and the canopies of military aircraft could contain nearly invisible antennae, electrical heaters for defrost, or informative optical displays.

These sheets, which are presently several meters long but could potentially be much larger, might also be useful in everything from flexible computer screens that could be rolled into a sack, to light bulb-like devices providing uniform lighting, to strong sails that could be propelled in space by sunlight.
“When you have a remarkable material, it’s easy to make advances in terms of applications,” said Ray Baughman of the University of Texas, Dallas, who led the research team that made the nanotube sheets. The scientists report their findings in the 19 August issue of the journal Science, published by AAAS, the nonprofit science society.

Growing a nanotube forest
Individual carbon nanotubes, long, cylindrical sheets of carbon atoms, are like minute bits of string, and researchers must assemble many trillions of these strings to make useful objects, including wide sheets and long yarns.

Until now, nanotube sheets have usually been made using versions of the ancient art of paper making, by filtering solutions of nanotubes and then peeling the nanotubes off the filter once they’re dry, which can take about a week. Baughman’s group has been working instead with nanotube “forests” that consist of nanotube bundles standing vertically.

The researchers have now shown that by teasing nanotubes away from one side of a forest and attaching them to a strip of sticky tape they can draw the nanotubes into a continuous sheet. With this method they can produce nanotube sheets at up to seven meters per minute, which is fairly close to the rate of commercial wool spinning.

“It’s so surprising that this works,” Baughman said. “A trillion nanotubes must be automatically rotated by about 90 degrees and self-assembled in a parallel fashion for every meter-long, 7 centimeter-wide sheet that we make.”
Group dynamics in the nanoworld
Carbon nanotubes, which have high electrical conductivity, flexibility, and strength, are consummate individualists. When lumped together into a larger object, they often lose the remarkable properties that made them shine by themselves.

The new sheets have many of the same abilities as the single nanotubes, although their strength does decrease, becoming comparable to that of high-strength Mylar and Kapton, which are used for ultralight air vehicles. The nanotube sheets, however, can better tolerate extreme temperatures and exposure to sunlight and higher energy radiation in space.

As with individual nanotubes, when you pass an electrical current through a nanotube sheets, then things really get cooking. For example, if the nanotubes are electrically injected with electronic charge to slightly change their structure, this charge injection can make the sheets move, generating the force and stroke needed for an artificial muscle. Electrical current can also induce the sheets to emit heat at infrared wavelengths or higher-energy wavelengths of light.
Putting nanotube sheets to work
These tricks with nanotube sheets may help researchers make good on some of the promises that nanotechnology offers.

For example, Baughman and other researchers would dearly love to create artificial versions of the body’s muscle fibers, which can convert a chemical energy supply into mechanical work with even more efficiency than a car engine. Artificial muscles might be useful for prosthetic limbs, humanoid robots, and bird- or insect-like air vehicles that fly by flapping wings.
To get an artificial muscle material to move over large distances, researchers need a highly elastically electrode that will stay in contact with this artificial muscle during movement. To produce such a system, Baughman’s group attached a nanotube sheet onto a stretched piece of artificial muscle rubber. As the rubber was relaxed and then restretched, the nanotube sheet-electrode moved right along with it, without losing its electrical conductivity.

The researchers also used an electric current to make a nanotube sheet light up almost instantly, via incandescent heating (the same process that causes the filament in a light bulb to glow), offering possibilities for sensor light sources or headlights that don’t use filament-based light bulbs.

Using nanotubes, Baughman and his colleagues produced devices called “light emitting diodes” that manipulate the flow of electricity to generate light particles called photons. The beauty of these diodes is that they’re transparent, so if you stuck them on a window, for example, you’d have a light source that was nearly invisible until it was turned on.

Microwave radiation can be used to heat the nanotube sheets, so the researchers sealed a sheet between two plates of plexiglas with a few blasts from a kitchen microwave oven. This type of process could be used to make windows or transparent adhesive appliqués, say for heating car windows or perhaps the outer surfaces of airplanes, according to Baughman.

Other applications for these nanotube sheets may include solar cells, surfaces that store energy storage while offering structural support for electric vehicles, and electrodes for flexible electronic circuits. The authors also say that, with further tweaking, their nanotube sheets may be useful for building a space elevator tether. They’re planning to put the sheets to the test by entering the Spaceward Foundation’s Elevator:2010 contest.

Baughman noted that other research teams have also been able to make sheets and other types of objects with carbon nanotubes, but they aren’t transparent, strong, and highly conducting at the same time, like the ones he and his colleagues have made.

He also credits much earlier developments with paving the way to his research. The ancient Egyptians, for example, were early unknowing nanotech experts, using nanosized gold particles to make their beautiful glassware.
Ovde

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

Imagine a future in which the rooftops of residential homes and commercial buildings can be laminated with inexpensive, ultra-thin films of nano-sized semiconductors that will efficiently convert sunlight into electrical power and provide virtually all of our electricity needs. This future is a step closer to being realized, thanks to a scientific milestone achieved at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

Researchers with Berkeley Lab and the University of California, Berkeley, have developed the first ultra-thin solar cells comprised entirely of inorganic nanocrystals and spin-cast from solution. These dual nanocrystal solar cells are as cheap and easy to make as solar cells made from organic polymers and offer the added advantage of being stable in air because they contain no organic materials.

“Our colloidal inorganic nanocrystals share all of the primary advantages of organics — scalable and controlled synthesis, an ability to be processed in solution, and a decreased sensitivity to substitutional doping – while retaining the broadband absorption and superior transport properties of traditional photovoltaic semiconductors,” said Ilan Gur, a researcher in Berkeley Lab’s Materials Sciences Division and fourth-year graduate student in UC Berkeley’s Department of Materials Science and Engineering.

Gur is the principal author of a paper appearing in the October 21 issue of the journal Science that announces this new development. He is a doctoral candidate in the research group of Paul Alivisatos, director of Berkeley Lab’s Materials Sciences Division, and the Chancellor's Professor of Chemistry and Materials Science at UC Berkeley . Alivisatos is a leading authority on nanocrystals and a co-author of the Science paper. Other co-authors are Berkeley Lab’s Neil A. Fromer and UC Berkeley’s Michael Geier.

In this paper, the researchers describe a technique whereby rod-shaped nanometer-sized crystals of two semiconductors, cadmium-selenide (CdSe) and cadmium-telluride (CdTe), were synthesized separately and then dissolved in solution and spin-cast onto a conductive glass substrate. The resulting films, which were about 1,000 times thinner than a human hair, displayed efficiencies for converting sunlight to electricity of about 3 percent. This is comparable to the conversion efficiencies of the best organic solar cells, but still substantially lower than conventional silicon solar cell thin films.
Vise

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

Ugljenične nanočestice pomažu zgrušavanje krvi, tvrde istraživači sa Univerziteta Teksas, a prenosi Sajens Dejli. Oni su na pacovima isprobali ponašanje raznih vrsta nanočestica u slučaju tromboze arterije, kao i njihov uticaj na ljudske krvne pločice.
- Otkrili smo da neke ugljenične nanočestice stimulišu ljudske krvne pločice da se okupljaju, vezuju jedna za drugu; takođe, dokazali smo da iste te čestice stimulišu blokadu arterije, u eksperimentu na pacovima - rekao je za Sajens dejli Marek Radomski iz Centra za vaskularnu biologiju Univerziteta Teksas.

Ugljenične nanočestice o kojima je reč su reda veličine milijarditog dela metra, što im omogućava da bez teškoće prolaze kroz pluća i ulaze u krvotok.
Ovde

offline
  • Pridružio: 10 Feb 2005
  • Poruke: 3549

A molecule that flips its arms like the slats on a Venetian blind might in future find uses in computer displays, computer memory, or even windows that become tinted at the flick of a switch.

Molecules whose shapes or movements can be easily controlled are important for nanotechnology. One kind that promises to be useful are those shaped in a helix that can be made to reverse its direction. When that happens the molecule is said to reverse its chirality.

Researchers at North Carolina State University in Raleigh and Vanderbilt University in Nashville, Tennessee, were working with a helical polymer called polyguanidine. Polyguanidine actually switched chirality so easily that it was difficult to control. To try to make the helices more stable, the researchers stuck side chains of anthracene along the helical backbone.

One characteristic of chiral molecules is that they are optically active - when polarised light passes through them in solution, its plane is rotated one way or another, depending on the chirality of the molecules.
Vise

Ko je trenutno na forumu
 

Ukupno su 703 korisnika na forumu :: 31 registrovanih, 4 sakrivenih i 668 gosta   ::   [ Administrator ] [ Supermoderator ] [ Moderator ] :: Detaljnije

Najviše korisnika na forumu ikad bilo je 3028 - dana 22 Nov 2019 07:47

Korisnici koji su trenutno na forumu:
Korisnici trenutno na forumu: A.R.Chafee.Jr., amaterSRB, angelas, Belac91, Bojan5150, Boris90, Doca, FOX, Gama, ikan, ljuba, MaksicZoran, manda87, Mercury, Milan A. Nikolic, Mirage 2000N, MrNo, Panter, Radoje, Recce, rovac, sabros, sekretar, Sr.Stat., suton, trajkoni018, V.P., VJ, vlada035, vukdra, zixmix