Article courtesy of Liesbeth Venema| Feb 8 , 2014 | The Guardian| Shared as educational material
A perfect sieve
Graphene, the sheet of carbon just one atom thick, has already featured a few times on this blog thanks to its unique promise for many applications. Could it even turn seawater into drinking water? Scientists at Manchester University think it may be possible using a filter made from laminates of graphene oxide, a form of graphene with oxygen-containing molecules attached to it.
This laminate can perform a magic trick: in the dry state it doesn’t let any gas molecule through and is vacuum-tight. When wet, however, nanoscale channels open up and water flows through rapidly, without any resistance. Any particle, molecule or ion that can’t squeeze through the channels is left behind.
But the nanochannels actually swell a little in water, opening up enough to let through two or three atomic layers of water and some ions. The researchers will try out ways to prevent the swelling, so that the nanochannels are so small that they block small ions while water still flows through quickly: a perfect filter for removing salt from water.
Dr Irina Grigorieva, a co-author of the study, says in a press release from Manchester University: “Our ultimate goal is to make a filter device that allows a glass of drinkable water to be made from seawater after a few minutes of hand pumping. We are not there yet but this is no longer science fiction.”
Graphene’s first text message
Wireless communication has become an essential part of our way of life as electronic gadgets are increasingly used on the move. In the near future, wireless chips will need to transmit data faster and be more compact to enable a wide variety of applications, including in smart tags or wearable electronics.
Graphene, which has ultra-efficient electronic properties, seems an ideal candidate for transistors in fast, wireless circuits, which convert radio-frequency signals into electrical currents. However, the conventional chip-making process damages the thin graphene layers, degrading circuit performance.
Now researchers at IBM have found a solution: they reverse the fabrication process, only introducing graphene at the final fabrication step. To test the chip, they sent a message by radio-signal, which the chip received and converted into a three letter message: I-B-M.
Looking for clues
Finding fingerprints is as important as ever in crime scene investigation. Now researchers from Wuhan, China, have used nanoparticles to reveal the merest smudge of a print, even on difficult surfaces such as plastic and coins.
A common technique to detect fingerprints is to treat surfaces with chemicals that make the residues left behind by a finger light up faintly in ultraviolet light. However, there is also fluorescence from the surface itself so that prints that are too weak remain hidden in the background noise. The researchers have therefore turned to infrared light, which causes hardly any fluorescence.
To make the fingerprints light up, nanoparticles are applied that convert two low-energy infrared photons into one high-energy UV one. To ensure this only happens at the fingerprints, molecules are attached to the nanoparticles that bind to lysosome, which is found in human sweat and left in fingerprint residue. Researchers used the new method to detect fingerprints on various surfaces and from different people, without any background interference.
Sun, sand and nanoparticles
Official health agencies advise using sunscreen lotion when the sun is out to protect against UV light, which causes sunburn and increases the risk of skin cancer. However, some researchers question whether the overall health benefits are clear enough.
One reason is that several studies over the past decade have reported potential harmful effects from the ingredients of sunblock. In recent years, sunscreens have appeared on the market that contain zinc oxide nanoparticles and, given existing concerns, the possible toxic effects are being closely studied.
There is no conclusive evidence that the nanoparticles could be harmful, but researchers at Harvard reason that it may be better to be safe than sorry. They propose sealing the nanoparticles within a thin shell of silica to minimise any toxic effects. Silica is what sand is made of, and is known to be a safe ingredient of many consumer products, including cosmetics.
The researchers compared how much damage the bare and encapsulated nanoparticles caused to DNA in live cells in a laboratory experiment and report three times less damage for the silica-coated nanoparticles.
This study does not say whether the uncoated nanoparticles are actually harmful inside a human body, but the researchers point out that a safer-by-design approach will reduce any possible risks.
In a heartbeat
Implantable medical devices such as pacemakers need batteries, which are bulky and have to be replaced in risky operations. Researchers at the University of Illinois have now found a way to power such devices using energy from the body itself, such as a beating heart. They use nanoribbons made of a piezoelectric material that produces an electric current when its is bent. The nanoribbons are held in place on a flexible silicone layer that conforms to the shape of the tissue on which it is placed.
The researchers have showed that sufficient power can be generated to operate a cardiac pacemaker. To extend the potential use, the device is also connected to a rechargeable battery.