When it comes to producing nanoparticle-sized semiconductors called quantum dots, scientists are now looking to earthworms to do their dirty work.
Like all semiconductors, the conductive properties of quantum dots are very specific to their crystals’ size and shape. But quantum dots have an advantage because scientists can precisely control the size of the crystals formed, and the resulting conductive properties of the dots. Their applications include LED lights, solar cells, and tiny lasers. Since quantum dots absorb and emit light, they may also aid in medical imaging, but thus far scientists have struggled to incorporate these dots into living cells. Because they are potentially toxic, the dots must undergo a number of chemical reactions before they are able to enter or attach to living cells. Scientists now think the trick to making the dots compatible may lie in producing the dots within living organisms.
Using carbon nanotubes and a dash of boron, scientists at Rice University have created a sponge that only absorbs oil. The superabsorbent sponge may not be of much use in the kitchen, but selective sucking of oil could be very helpful in cleaning up oil spills in the ocean. Other perks: the nanosponge is attracted to magnets, so that’s they’re easily controlled, and they’re reusable. At the end of this video, grad student Daniel Hashim shows how to extract energy from the oil-soaked nanosponge by burning it. Then you’re left with just the nanosponge, all ready to absorb oil again.
The nanoparticle. ACUPA is a protein that helps the particle attach to cancer
cells; the red and blue pieces are polymers that make up the particle’s shell.
One of the persistent problems in cancer treatments is that try as we might, it’s hard to get drugs to attack just tumors: they nearly always attack patients’ healthy cells too. Finding ways to get drugs to kill tumors, and tumors alone, is a major area of research, and a recent trial in Science Translational Medicine indicates that one promising strategy, encasing the drug in a tiny particle that dissolves when it reaches a tumor, works better than just using the drug alone.
The smallest named unit in the metric system is the yoctogram, equal to 0.000000000000000000000001 grams. (Yes, that’s 24 zeros.) For a scale that can measure differences in mass as small as a yoctogram, which is on the order of the mass of a proton, physicists writing in Nature Nanotechnology turned to the wunderkind of nanotechnology: carbon nanotubes.
What’s the News: In traditional solar cells, sunlight is absorbed by the cell (made from silicon or titanium dioxide), freeing electrons, which travel across the cell to an electron collector, or electrode. A problem with solar cells is that many electrons don’t find their way to the electrode; carbon nanotubes can be used as bridges between the loosened electrons and the electrode, but nanotubes tend to bunch up, decreasing the efficiency and causing short circuits. Researchers have now created genetically engineered viruses can be used to keep the nanotubes in place, increasing energy conversion by nearly one-third. “A little biology goes a long way,” research group leader Angela Belcher told MIT News, noting that the entire virus-nanotube bridging layer represents only 0.1% of the finished cell’s weight.
What’s the News: Scientists are using nanoparticles to develop ways to fight bacteria that are resistant to conventional antibiotics. These tiny drugs physically punch holes through bacteria instead of killing them chemically, which means that they could be especially effective on antibiotic-resistant bacteria strains like the dangerous methicillin-resistant Staphylococcus aureus (MRSA). “The applications are going to be very diverse, whether we’re talking about wound healing or dressing, skin infection, and quite possibly injections into the bloodstream,” James Hedrick, master inventor at IBM Almaden Research Center in San Jose, California, told Popular Science.
What’s the News: Scientists have developed a new carbon nanotube device (pictured above) that’s capable of detecting single cancer cells. Once implemented in hospitals, this microfluidic device could let doctors more efficiently detect the spread of cancer, especially in developing countries that don’t have the money for more sophisticated diagnostic equipment. Any improvement in detecting cancer’s spread is important, says MIT associate professor of aeronautics and astronautics Brian Wardle, because “of all deaths from cancer, 90 percent are … from tumors that spread from the original site.”
What’s the Context:
Not So Fast: The process of commercializing a technology like this takes quite a while; the previous version from four years ago is being tested in hospitals now and is may be commercially available “within the next few years.”
Next Up: The scientists are currently tweaking the device to try to catch HIV.
Reference: Grace D. Chen et al. “Nanoporous Elements in Microfluidics for Multiscale Manipulation of Bioparticles.” Small. DOI: 10.1002/smll.201002076
Image: Brian Wardle/MIT
Today in the journal Nature, researchers led by Charles Lieber report a big step forward in the field of tiny computing: the creation of linked-up logic circuits made of nanowires, which could be used to build itty-bitty processors.
The devices described in the paper layer additional wires across the germanium-silicon ones; charges can be trapped in these wires, influencing the behavior of the underlying nanowires. This charge trapping is nonvolatile but reversible; in other words, you can switch one of the nanowires on or off by altering the charge stored in its neighborhood. This makes it possible to turn the nanowires into a standard field-effect transistor (the authors term them NWFETs for “nanowire field-effect transistors”). [Ars Technica]
Lieber had been able to create simple versions of those NWFETs before, but those were difficult to build on a large enough scale to create logic circuits.
This picture may look like an exuberant patchwork quilt, or a stretch of really interesting farmland as seen from an airplane. In fact, what you’re looking at is sheet of graphene–a one-atom-thick layer of carbon, measuring about 100,000 atoms across.
The image, produced by an electron microscope, reveals that the honeycomb-like lattice of carbon atoms that forms a sheet of graphene is full of irregularities. Each sheet is composed of patches of atoms, and each patch has a slightly different rotation than that of its neighbors. By firing electrons at a sheet and using different colors to identify the angles at which the electrons bounced back, researchers made this rainbow image of a graphene sheet with the patch boundaries clearly shown.
Lead researcher David Muller says this is an easy and efficient way to understand a graphene sheet’s properties.
“You don’t want to look at the whole quilt by counting each thread. You want to stand back and see what it looks like on the bed. And so we developed a method that filters out the crystal information in a way that you don’t have to count every atom,” said David Muller, professor of applied and engineering physics and co-director of the Kavli Institute at Cornell for Nanoscale Science. [press release]
The research, which was published in Nature, will be useful as nanotechnologists continue to investigate graphene’s exciting electrical properties. Researchers had previously thought that larger patches would improve the electrical conductivity of graphene, but Muller’s experiments suggest that theory is wrong. Rather, it’s impurities in graphene sheets that interfere with their conductivity, he argues.
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Image: Cornell University/ P.Y. Huang / D. A. Muller
Now and then we stop to marvel at the feats of carbon nanotube researchers, who use these infinitesimal tubes to build materials of adamantine strength and impressive electrical conductivity. But what if you could marry the robustness of nanotubes to the stretchiness of viscous liquids? You’d be Xu Ming and his fellow Japan-based scientists, who have creating a super rubber that—unlike normal rubber—does not crack and fall apart at extreme temperatures.
Xu’s team outlines its creation in a study for this week’s edition of the journal Science.
Made entirely of carbon, it can flow and stretch slowly like thick honey and spring back to its original form, said [Xu].”It looks like a metal sponge that is porous, it is made from trillions of entangled carbon nanotubes,” she said in a telephone interview. “When you stretch and release it, it can come back slowly (to its original shape).” [ABC News]
The material’s litany of talents—especially its ability to keep its shape up to temperatures of 1000 degrees C (1832 Fahrenheit) and down to -196 C (-321 F)—inspires visions of using it in all kinds of extreme conditions.
That huge range of temperatures means the new material could be used in everything from spacecraft to car shock absorbers, said Roderic Lakes, a scientist at the University of Wisconsin who studies viscoelastic materials. Spacecraft equipped with this material could withstand the intense cold of [Saturn]’s largest moon, Titan, said Gogotsi, or the heat of the sun in space, said Lakes. [Discovery News]