NewScientist (September 3, 2010) -COTTON impregnated with silver nanowires and carbon nanotubes (CNTs) could provide a cheap and effective method of purifying water in remote locations.
A new filter needs only gravity and a weak electric current to produce its sterilising effect, making it suitable for a portable water-treatment device.
The fabric is easy to produce, says lead researcher Yi Cui at Stanford University in California. Cui's team simply dip a piece of cotton into a solution of CNTs and then pipette droplets containing silver nanowires onto the cotton.
Analysing the fabric with a scanning electron microscope reveals that the CNTs stick to the individual cotton fibres, while the slightly larger silver nanowires form a mesh between the fibres. The nanoparticles enable the fabric to conduct electricity, so a weak electric current can run across it. This helps kill bacteria by damaging their outer membranes, while the silver nanowires' anti-bacterial properties do the rest.
So when Cui and his colleagues poured water contaminated with the bacterium Escherichia coli (pictured) through the silver-coated, electrically-conducting fabric, they found it killed 89 per cent of the bacteria. By conducting three successive runs through the fabric, they were able to kill over 98 per cent - enough to make the water safe to drink.
As well as testing the fabric with other micro-organisms, Cui is making sure the CNTs and silver nanowires aren't washed into the water. "So far, our evidence suggests that they don't come off," Cui told New Scientist.
"It is an interesting academic study," says nanoengineer Eric Hoek at the University of California, Los Angeles. He says proving that the potentially harmful CNTs do not leach into the water will be a key step in finding out if it is useful on a practical level.
Source: http://www.newscientist.com/article/mg20727765.900-nanoengineered-cotton-promises-to-wipe-out-water-bugs.html
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Reflections:
Definitely, technology has advanced at a shocking speed over the years such that appalling discoveries are uncovered almost every day. In the past, such scientific discoveries which were uncovered could cause a public uproar. However, in this day and time, the scientific world is oblivious to us. In this case, this new technology could prove useful in third-world countries where proper sanitation and supply of fresh water is unavailable. However, this could also prove costly if there is not enough research. From the article, we can already see loopholes in this project. As claimed by the nanoengineer Eric Noek, "proving that the potentially harmful CNTs do not leach into the water will be a key step in finding out if it is useful on a practical level." Using CNTs could raise fears that it might become the next absestos which could completely rule out this form of treatment. Despite these challenging factors, I would like to commend on the nanoengineers' efforts in trying to enhance the living conditions of people in remote areas.
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