Nanoscopic gold springs could unravel twisted molecules
Researchers at the University of Bath have built gold spring-shaped coils that are 5,000 times thinner than human hairs. These are being used with lasers to improve communications systems, nanorobotics and pharmaceutical design.
“Closely observing the chirality of molecules has lots of potential applications”
Many molecules twist in certain ways and can exist in left or right ‘handed’ forms depending on how they twist. This twisting, called chirality, is crucial because it changes the way a molecule behaves.
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Chiral molecules are examined using particular laser light, which itself twists as it travels, but this examination can be difficult when dealing with the small amounts of molecules scientists typically have to work with. However, when these tiny gold springs are present they also twist the light and could help enhance the detection of chirality.
Second Harmonic Generation
The Bath researchers worked with colleagues from the Max Planck Institute for Intelligent Systems to see how the gold springs, or nanohelices, could be used with a colour-conversion method for light, known as Second Harmonic Generation (SHG), where the better the performance of the spring, the more red laser light converts into blue laser light.
The springs are tiny. They have a pitch of 37nm, a height of 81nm, a wire thickness of 18nm, an inner diameter of 28nm and an outer diameter of 55nm. The laser light in contrast has a central frequency of 800nm, ten times the size of the nano springs, and the pulses are just 100 femtoseconds long.
The researchers found that the springs were indeed very promising but that how well they performed depended on the direction they were facing.
“It is like using a kaleidoscope to look at a picture; the picture becomes distorted when you rotate the kaleidoscope. We need to minimise the distortion,” said David Hooper, a PhD student and first author of the study,
“Closely observing the chirality of molecules has lots of potential applications, for example it could help improve the design and purity of pharmaceuticals and fine chemicals, help develop motion controls for nanorobotics and miniaturise components in telecommunications,” said Dr Ventsislav Valev who led the study and the University of Bath research team.
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