Loading the Molecular Dice
How a framework for controlling molecular reactions at the atomic scale has potential implications for nanotechnology, pharmaceutical synthesis, and clean energy research
| 2 min read | News
An artist’s representation of a scanning tunnelling microscope probing a toluene molecule
Credit: Dr Kristina Rusimova, Hannah Martin and Pieter Keenan
Researchers at the University of Bath, UK, have demonstrated that the outcomes of single-molecule chemical reactions can be influenced by controlling the energy of injected electrons. Published in Nature Communications, the study addresses a long-standing challenge in nanotechnology: achieving precision control over reactions with multiple possible outcomes. Potential applications include pharmaceutical synthesis, where minimizing unwanted byproducts could improve efficiency and sustainability.
The team used scanning tunneling microscopy (STM) to study the reactions of toluene molecules on a silicon surface. By injecting electrons into the molecules, researchers induced two competing outcomes: i) desorption, where the molecule detached from the surface or ii) switching, where it relocated to a nearby site. Using density functional theory (DFT) simulations alongside STM, they identified energy thresholds and molecular barriers that dictated reaction dynamics.
In addition to STM, the researchers employed mass spectrometry to validate the chemical composition of the toluene molecules and their interactions with the silicon surface. This confirmed the stability of the molecules during experimental preparation and provided insights into the structural changes associated with reaction outcomes.
“Our latest research demonstrates that STM can control the probability of reaction outcomes by selectively manipulating charge states and specific resonances through targeted energy injection,” said Kristina Rusimova, who led the study.
In a press release, PhD student and first author Pieter Keenan explained, “The differing reaction barriers drive the probabilities. Altering only the energy input allows us, with high precision, to make a reaction outcome more likely than another – in this way we can ‘load the molecular dice.’”
The researchers also demonstrated how the energy thresholds for these reactions correspond to changes in the thermal energy of an intermediate molecular state. Using STM’s precise electron injection, they created a controlled "heating" effect within the molecule, influencing reaction outcomes without altering initial experimental conditions.
Tillmann Klamroth from Potsdam University in Germany, added: “This study combines advanced theoretical modelling with experimental precision, leading to a pioneering understanding of the reactions’ probabilities based on the molecular energy landscape. This paves the way for further advances in nanotechnology.”
Looking ahead, Rusimova said: “With applications in both basic and applied science, this advancement represents a major step toward fully programmable molecular systems. We expect techniques such as this to unlock new frontiers in molecular manufacturing, opening doors to innovations in medicine, clean energy, and beyond.”
