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 at Stanford University in California. Cui鈥檚 team simply dip a piece of cotton into a solution of CNTs and then pipette droplets containing silver nanowires onto the cotton.
Advertisement
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鈥� 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 鈥� enough to make the water safe to drink (Nano Letters, ).
As well as testing the fabric with other micro-organisms, Cui is making sure the CNTs and silver nanowires aren鈥檛 washed into the water. 鈥淪o far, our evidence suggests that they don鈥檛 come off,鈥� Cui told New Scientist.
鈥淚t is an interesting academic study,鈥� says nanoengineer 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.
