(Press-News.org) Graphene has proven itself as a wonder material with a vast range of unique properties. Among the least-known marvels of graphene is its strange love affair with water.
Graphene is hydrophobic – it repels water – but narrow capillaries made from graphene vigorously suck in water allowing its rapid permeation, if the water layer is only one atom thick – that is, as thin as graphene itself.
This bizarre property has attracted intense academic and industrial interest with intent to develop new water filtration and desalination technologies.
One-atom-wide graphene capillaries can now be made easily and cheaply by piling layers of graphene oxide – a derivative of graphene – on top of each other. The resulting multilayer stacks (laminates) have a structure similar to nacre (mother of pearl), which makes them also mechanically strong.
Two years ago, University of Manchester researchers discovered that thin membranes made from such laminates were impermeable to all gases and vapours, except for water. This means that even helium, the hardest gas to block off, cannot pass through the membranes whereas water vapour went through with no resistance.
Now the same team led by Dr Rahul Nair and Prof Andre Geim has tested how good the graphene membranes are as filters for liquid water. The results appear in the latest issue (Feb 14, 2014) of Science.
The researchers report that, if immersed in water, the laminates become slightly swollen but still allow ultrafast flow of not one but two monolayers of water.
Small salts with a size of less than nine Angstroms can flow along but larger ions or molecules are blocked. Ten Angstroms is equivalent to a billionth of a metre.
The graphene filters have an astonishingly accurate mesh that allows them to distinguish between atomic species that are only a few percent different in size.
On top of this ultraprecise separation, it is also ultrafast. Those ions that can go through do so with such a speed as if the graphene membranes were an ordinary coffee filter.
The latter effect is due to a property that the Manchester scientists call "ion sponging". Their graphene capillaries suck up small ions as powerful hoovers leading to internal concentrations that can be hundreds of times higher than in external salty solutions.
Dr Nair said: "The water filtration is as fast and as precise as one could possibly hope for such narrow capillaries. Now we want to control the graphene mesh size and reduce it below nine Angstroms to filter out even the smallest salts like in seawater. Our work shows that it is possible."
Dr Irina Grigorieva, a co-author of the study, added: "Our ultimate goal is to make a filter device that allows a glass of drinkable water made from seawater after a few minutes of hand pumping. We are not there yet but this is no longer science fiction".
INFORMATION:
The work was done in collaboration with a group led by Hengan Wu from Chinese Academy of Sciences who carried out extensive computer simulations to understand the filtration mechanism.
Graphene's love affair with water
2014-02-14
ELSE PRESS RELEASES FROM THIS DATE:
Stopping smoking linked to improved mental health
2014-02-14
The researchers say the effect sizes are equal or larger than those of antidepressant treatment for mood and anxiety disorders.
It is well known that stopping smoking substantially reduces major health risks, such as the development of cancers, cardiovascular and respiratory diseases. But the association between smoking and mental health is less clear cut.
Many smokers want to stop but continue smoking as they believe smoking has mental health benefits. And health professionals are sometimes reluctant to deal with smoking in people with mental disorders in case ...
Children living close to fast food outlets more likely to be overweight
2014-02-14
Children living in areas surrounded by fast food outlets are more likely to be overweight or obese according to new research from the University of East Anglia (UEA) and the Centre for Diet and Activity Research (CEDAR).
New research published today looked at weight data from more than a million children and compared it with the availability of unhealthy food from outlets including fish and chip shops, burger bars, pizza places, and sweet shops.
They found that older children in particular are more likely to be overweight when living in close proximity to a high density ...
London's bicycle sharing scheme has had positive overall health effect
2014-02-14
The authors say the potential benefits of cycling "may not currently apply to all groups in all settings."
Over 600 cities around the world have implemented bicycle sharing schemes, but there is very little published evidence on the health effects of such schemes.
So researchers at the University of Cambridge, University College London and the London School of Hygiene and Tropical Medicine set out to estimate the health impacts of London's cycle hire scheme on its users.
Using registration and usage data collected from April 2011 to March 2012, they modelled the medium ...
Researchers find breast cancer drug in bodybuilding supplement
2014-02-14
In a letter to The BMJ this week, they explain that, for more than 30 years, bodybuilders have taken tamoxifen to prevent and treat gynaecomastia (breast swelling) caused by use of anabolic steroids.
Usually, tamoxifen is sourced from the illicit market, they say. However, bodybuilding discussion forums have speculated that a dietary supplement called Esto Suppress contains tamoxifen because the label listed one of its chemical names.
The researchers purchased four samples at different times between late 2011 and early 2012 and analysed their contents. Tamoxifen ...
Mental health patients up to 4 times more likely to be infected with HIV, Penn study finds
2014-02-14
PHILADELPHIA— People receiving mental health care are up to four times more likely to be infected with HIV than the general population, according to a new study published Feb. 13 in the American Journal of Public Health from researchers at Penn Medicine and other institutions who tested over 1,000 patients in care in Philadelphia and Baltimore. Of that group, several new HIV cases were detected, suggesting that not all patients are getting tested in mental health care settings, despite recommendations to do so from the CDC and the Institute of Medicine.
The study is ...
Scientists reveal cosmic roadmap to galactic magnetic field
2014-02-14
DURHAM, NH –-Scientists on NASA's Interstellar Boundary Explorer (IBEX) mission, including a team leader from the University of New Hampshire, report that recent, independent measurements have validated one of the mission's signature findings—a mysterious "ribbon" of energy and particles at the edge of our solar system that appears to be a directional "roadmap in the sky" of the local interstellar magnetic field.
Unknown until now, the direction of the galactic magnetic field may be a missing key to understanding how the heliosphere—the gigantic bubble that surrounds ...
Massachusetts' fire-safe cigarette law appears to decrease likelihood of residential fires
2014-02-14
Boston, MA – A six-year-old Massachusetts law requiring that only "fire-safe" cigarettes (FSCs) be sold in the state appears to decrease the likelihood of unintentional residential fires caused by cigarettes by 28%, according to a new study by Harvard School of Public Health (HSPH) researchers.
The study will appear online February 13, 2014 in the American Journal of Public Health.
"This study is the first rigorous population-based study to evaluate the effectiveness of the fire-safe cigarette standards, and shows that science-based tobacco product regulation can protect ...
Efficient treatment a step closer in the fight against cancer-causing herpes
2014-02-14
Herpes virus proteins are more 'spaghetti-like' than previously thought, which provides a vital clue in the search for an efficient treatment against a type of herpes which causes a form of cancer known as Kaposi's sarcoma.
That's according to researchers from The University of Manchester who have discovered that the virus protein uses its flexible arms to pass on viral building blocks to the proteins of cells that it hijacks.
The latest part of this research is published in the February edition of PLoS Pathogens which has uncovered how the protein of cells hijacked ...
Robotic construction crew needs no foreman
2014-02-14
Cambridge, Mass. – February 13, 2014 – On the plains of Namibia, millions of tiny termites are building a mound of soil—an 8-foot-tall "lung" for their underground nest. During a year of construction, many termites will live and die, wind and rain will erode the structure, and yet the colony's life-sustaining project will continue.
Inspired by the termites' resilience and collective intelligence, a team of computer scientists and engineers at the Harvard School of Engineering and Applied Sciences (SEAS) and the Wyss Institute for Biologically Inspired Engineering at Harvard ...
'Sexy' underwear is not the only way to feel feminine on Valentine's Day, academic says
2014-02-14
AUDIO:
This is a Podcast recording of Dr. Christiana Tsaousi explaining her research.
Click here for more information.
TV makeover shows and glossy magazines can leave women feeling guilty for not wearing "sexy" lingerie – especially on Valentine's Day.
But in fact, many different types of underwear could make them feel feminine, according to an expert on underwear consumption.
Dr Christiana Tsaousi, a lecturer in marketing and consumption at the University of Leicester's ...