Nanotubular awesomeness

Single-walled carbon nanotubes (SWCNT) are vertical hollow structures comprised of carbon atoms enjoined via industrial-strength hexagonal lattice.  Scientists at Rice University have published research  into a method of "gluing" the SWCNTs to sheets of graphene that maintain the ohmic properties of the bond.

Picture chicken wire that is stronger than steel, yet able to conduct electricity.  Comparatively, copper (Cu) and gold (Au) -- two traditionally "conductive" materials are soft and would never be able to support comparative structures of these relative heights.  Just as an ant is able to lift ~50 times their body weight, these carbon nanotube structures are able to scale to heights beyond imagination -- "up to a distance of 120 microns (0.12mm), which is really rather impressive at this scale. If we scaled it up to actual trees, they would rise into outer space," reports ExtremeTech.

This microcosm of tubular awesomeness is significant because it means that the surface area of a base can actually support much more "storage" power.    That is, supercapacitors, lithium-ion batteries, and other kinds of energy storage may  be able do do more with less. Denser energy storage structures mean longer-life batteries in a smaller space. 

Screening pollutants

Research sponsored by the National Science Foundation and DARPA Research Center for Micro/Nano-Electromechanical Transducers has garnered some breakthroughs in what could be the next era of pollution reduction.

Graphene membranes, which are known to be selectively porous, exhibit the capability to screen out pollutants by separating inert carbon dioxide molecules from larger, more potentially harmful ones, such as nitrogen and sulphur hexaflouride.   The graphene membranes work especially well for gaseous "pollutant" materials because of the semi-permeable nature of graphene membranes.

Illustration by Zhangmin Huang

"The findings are a significant step toward the realization of more energy-efficient membranes for natural gas production and for reducing carbon dioxide emissions from power plant exhaust pipes," reports the University of Colorado at Boulder, where much of the research took place.  "Those characteristics make graphene an ideal material for creating a separation membrane because it is durable and yet doesn’t require a lot of energy to push molecules through it, he said."

Given these findings, may I hypothesize about some other related applications --  Radiation containment?   Automobile exhaust pipes?  Chimney screens?

As with any recent breakthrough, there are some logistical challenges to be overcome before the applications can be widely applied.    For example, "creating large enough sheets of graphene to perform separations on an industrial scale, and developing a process for producing precisely defined nanopores of the required sizes are areas that need further development. The CU-Boulder experiments were done on a relatively small scale."

Extending memory beyond Moore's Law

Red Orbit is reporting that researchers at Rice University have been able to combine the almost ionic properties of graphene with the light-penetrable properties of silicone oxide to design what amounts to flexible and transparent 3D, two-terminal memories. 

"[The] highly transparent, nonvolatile resistive memory devices are based on the revelation that silicon oxide can be a switch  At just 5 nanometers, a channel can be created to extend memory beyond Moore’s Law, which predicts computer circuitry will double in power every two years.

Manufacturers are finding physical limits on current architectures when trying to fit millions of bits on small devices. Currently, electronics are made with 22 nanometer circuits.

Combining silicon and graphene enables the scientists to extend the possibilities of where memory can be placed. The devices could not only have potential for facing the harsh conditions of radiation, but also could be able to withstand heat of up to about 1,300 degrees Fahrenheit.

source:  http://www.redorbit.com/news/technology/1112706299/graphene-flexible-transparent-memory-100312/?print=true

Stepping down from 22 to 5 nanometers may not seem like a huge leap, but thus far it has presented some logistical challenges.  Up to this point, the primary limitation in down-sizing circuitry has been in finding materials that can retain their "transmission" properties at such small diameters.  As explained by Dr. James Tour, "We need transparent wires to wire them together and bring in the needed voltages and record the currents."

So what is it that makes graphene so special?  

"Graphene, being transparent, is being used as the wiring for both the input and output electrodes on the plastic substrates." he explains further.  "On the glass substrates, we use indium-tin-oxide (ITO), a transparent metallic electrode for the input and graphene on top for the output.”

Boosting the anti-corrosive properties of copper

A microscopic layer of graphene atoms coating a simple copper wire can boost the anti-corrosive properties of that wire by up to 100 times, reports Science Direct

Pure copper is one of the softest and most malleable metals, and copper ions alone are water-soluble. But with the application of a single layer of graphene atoms, the wire can stand up to much more harsh environments.
The implications are for better "insulation" materials allowing copper to be used in places where it otherwise wouldn't make sense.

The researchers applied the graphene to copper at temperatures between 800 and 900 degrees, using a technique known as chemical vapour deposition, and tested it in saline water. “In nations like Australia, where we are surrounded by ocean, it is particularly significant that such an atomically thin coating can provide protection in that environment,” Dr Banerjee said. Initial experiments were confined to copper, but Dr Banerjee said research was already under way on using the same technique with other metals. This would open up uses for a huge range of applications, from ocean-going vessels to electronics: anywhere that metal is used and at risk of corrosion. Such a dramatic extension of metal’s useful life could mean tremendous cost savings for many industries.

source: http://www.sciencedirect.com/science/article/pii/S0008622312003636
source: http://www.nanowerk.com/news2/newsid=26835.php

Downsides to the science

Amazing as it is, there appear to be some potential downsides to the amazing graphene. 

Two recent stories stick out in my constant perusal of this topic. The first is potential danger to individuals, the second is a potential downside to our fragile ecosystem.

The first one discusses the downside of carbon nanotubes as they can essentially "trap" cancer cells

source:  nanotube posts from technewsdaily

According to a new study conducted by researchers at Brown University, nanomaterials such as carbon nanotubes mimic asbestos and can fool our cells into thinking they are big enough to ingest, leading to some disastrous results. This is the same thing that makes asbestos dangerous, a process lead researcher Huajian Gao compared to eating a lollipop that's bigger than your own body — it would get stuck.

The second source of danger appears even more disturbing, as the extremely durable, pliant and "resistant" materials that graphene can enhance end up being toxic to many aquatic animals:

Nickel, chromium and other metals used in the manufacturing process can remain as impurities. Deng and his colleagues found that these metals and the CNTs themselves can reduce the growth rates or even kill some species of aquatic organisms. The four species used in the experiment were mussels (Villosa iris), small flies' larvae (Chironomus dilutus), worms (Lumbriculus variegatus) and crustaceans (Hyalella azteca).

 source

"Zapped" graphene increases power density of lithium-ion batteries

That which doesn't kill it makes it stronger . . . Research has revealed that the action of "zapping" a sheet of graphene with a laser or super-concentrated camera flash actually helps it become a more powerful anode for lithium ion batteries. It works because the damage done to the sheet allows the ions to cycle more quickly through the cracks and newly-created pores, without damaging the actual charging ability of the battery.

The new material is made from graphene, which is the world's thinnest material. They took a sheet of graphene and blasted it with a camera flash or laser to deform it, causing several pores and cracks. This made the graphene sheet a great anode for lithium ion batteries because the lithium ions could cut through the pores/cracks to charge and discharge rather than run the entire length of graphene (which took much longer). This ultimately increased the power density. Source

Other research revealed graphene's self-healing capacity to "knit" itself back together. Hole-burning "metals" which were initially thought to damage sheets of graphene were later discovered to magically mend themselves. Source

Applying graphene to solar panel technology

Researchers Develop Method to Create Photovoltaic Solar Cells from Any Materials

Graphene's awesomeness can also be applied to solar panel technologies. The article is a little. . . chewy, but the basic gist is that a single layer of graphene applied to a panel creates somewhat of self-fueling system to power the "self-gating configuration, in which the gate was powered internally by the electrical activity of the cell itself."

Under the SFPV system, the architecture of the top electrode is structured so that at least one of the electrode’s dimensions is confined. In one configuration, working with copper oxide, the Berkeley researchers shaped the electrode contact into narrow fingers; in another configuration, working with silicon, they made the top contact ultra-thin (single layer graphene) across the surface. With sufficiently narrow fingers, the gate field creates a low electrical resistance inversion layer between the fingers and a potential barrier beneath them. A uniformly thin top contact allows gate fields to penetrate and deplete/invert the underlying semiconductor. The results in both configurations are high quality p-n junctions.

http://theenergycollective.com/energyrefuge/98631/researchers-develop-method-create-photovoltaic-solar-cells-any-materials

Graphene self-repairs

This has some amazing implications for bendable circuits, wearable electronics, etc.

RESEARCHERS at the University of Manchester and the SuperSTEM facility at STFC’s Daresbury Laboratory have found that graphene can self-repair its holes. Graphene is composed of one-atom-thick carbon sheets and has electronic and physical properties that promise a number of exciting applications in the future. The team, led by Professor Kostya Novoselov was originally looking to gain a deeper understanding into how metals interact with graphene. However, in the course of their study, they found that while metals can cause holes in the graphene sheet, some of these holes mended themselves using nearby loose carbon atoms to re-knit the graphene structure. According to the researchers, not only can they use metals to controllably sculpt the graphene at an atomic level, they can also grow it back in new shapes, making for an increased degree of flexibility.

Source: http://www.electronicsnews.com.au/news/graphene-self-repairs

Making salt-water fresh

Oh, the many uses of this amazing material!  Discovered a new application today -- desalination!  With 70 percent of the Earth's water containing salt, the possible application of this to use the most plentiful source of water?  Awesome.

"Earlier this year, University of Manchester researchers studying graphene’s ion permeation properties found that water molecules from a container diffused through a graphene membrane at the same evaporation rate whether the container was closed or open. Professor Andre Geim, a recipient of the 2010 Nobel Prize in Physics for his research with graphene, told WDR, “Its properties are so unusual that it is hard to imagine that they cannot find some use in the design of filtration, separation or barrier membranes and for selective removal of water.”

SOURCES:  http://www.desalination.com/wdr/48/28/graphene-membranes-show-promise 

Transforming the capabilities of electronics

A sheet of graphene "one carbon atom thick" has unique physical properties that can transform a passive device into one that can produce and interact with microwave frequencies.  

New research by Columbia Engineering demonstrates remarkable optical nonlinear behavior of graphene that may lead to broad applications in optical interconnects and low-power photonic integrated circuits. With the placement of a sheet of graphene just one-carbon-atom-thick, the researchers transformed the originally passive device into an active one that generated microwave photonic signals and performed parametric wavelength conversion at telecommunication wavelengths.

SOURCE:  http://www.pddnet.com/news-graphene-leads-to-a-new-paradigm-for-low-power-telecommunications-071612/