Gold Spring-Shaped Coils and Lasers Detect Twisted Molecules

A novel technique that uses powerful lasers and gold spring-shaped coils 5,000 times thinner than human hair could improve pharmaceutical design, telecommunications and nanorobotics, as it has the ability to detect twisted molecules.

Gold spring-shaped coils 5000 times thinner than human hairs offer promising application through the interaction of their helical shape with light. Courtesy of Ventsislav Valev.

Molecules twist in certain ways and depending on which way they twist can take on left or right handed forms. This twisting — called chirality — changes the way a molecule behaves in the body.

Studying small amounts of chiral molecules is difficult to do with laser light because the laser light itself twists as it travels. Researchers from the University of Bath Department of Physics and the Max Planck Institute for Intelligent Systems have incorporated the miniscule gold spring into the process as their shape twists the light and fits better in the molecules, making it easier to detect minute amounts.

Using some of the smallest springs ever created, the researchers examined how effective the gold springs could be at enhancing interactions between light and chiral molecules. Their study is based on a color-conversion method for light, known as second harmonic generation (SHG); the better the performance of the spring, the more red laser light converts into blue laser light.

Researcher David Hooper said they found that how well the springs 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 minimize the distortion,” said Hooper. “In order to reduce the distortions, the team is now working on ways to optimize the springs, which are known as chiral nanostructures.”

Observing the chirality of molecules offers many potential applications, It could help improve the design and purity of pharmaceuticals and fine chemicals, help develop motion controls for nanorobotics and miniaturize components in telecommunications.

The research is published in the journal Advanced Materials (doi: 10.1002/adma.201605110).