One-atom tractor beams enhance chemical catalysis

By trapping light in tiny gaps just a few atoms wide, a team at the NanoPhotonics Center at the Cavendish Laboratory at the University of Cambridge increased the optical forces a thousandfold, strong enough to force atoms into positions that drive chemical reactions more efficiently.

“We’ve found a new way to amplify the powers of light, enough to move now metal atomsand that is the key to reducing the energy barrier to make catalysis work more easily,” explains co-lead researcher Shu Hu.

Weak draw beams are used to optical tweezers who can investigate biological processes with beams of tightly focused light that capture transparent micro-objects made of glass or polymer. But to use light to pick single atoms of solids requires much stronger forces. Now, a team at the NanoPhotonics Center at the Cavendish Laboratory has demonstrated a way to build tiny slits that amplify the optical powers of visible light. They use these to pull single gold atoms out of a crystal, get them close to a molecular bond, and watch the effects directly on their flopping and vibration. Published in scientific progress they show new ways to make light work powerfully and suggest new approaches for driving chemical transformations.

Looking at one band at a time in their experiments avoids averaging a multitude of different effects. “Single metal atoms are the anvil where catalysis forges new chemical bonds,” Prof Jeremy Baumberg promises, “and we can begin to watch and control this process.” Catalysis is essential for all man-made chemicals and polymers.

“It’s like watching the beautiful dance of an atom and a molecule in real time,” Hu notes.