Dive into the pioneering research of Leo Gross, a principal research staff member at IBM Research Europe – Zurich. With a focus on atom and molecule manipulation, he’s a driving force behind revolutionary breakthroughs in the field. Discover how he’s pushing the boundaries of atomic force microscopy (AFM) and scanning tunnelling microscopy (STM) to explore chemical reactions, resolve molecular structures, and delve into the world of single-electron charges. By revealing the secrets of chemical bonds and charged molecules on the atomic scale, his work holds immense promise for advancing fields like combustion, medicine, and catalysis. Explore the cutting-edge world of atomic-scale chemistry as Dr. Gross breaks down barriers and opens new frontiers in our understanding of molecules and their behaviour.

Which wall does your research break?

We break the wall to resolving single molecules [https://www.science.org/doi/full/10.1126/science.1176210] and single electron charges [https://www.science.org/doi/full/10.1126/science.1172273] with atomic resolution by force measurements. Using a home-built atomic force microscope (AFM), functionalized a with single CO molecule at its tip, operated at 5 Kelvin, we can not only see individual chemical bonds in a molecule but even form and break them. I developed these techniques and now apply them to studying chemistry on the atomic scale. We discovered new chemical reactions [https://www.nature.com/articles/nchem.2438] and new ways to control them [https://www.science.org/doi/full/10.1126/science.abo6471]. That way, we created elusive molecules, that could not be generated or characterized before, such as triangulene, a carbon-based single-molecule magnet [https://www.nature.com/articles/nnano.2016.305], or the carbon allotrope cyclo[18]carbon, revealing its debated structure [https://www.science.org/doi/full/10.1126/science.aay1914], achieving long-standing goals and fundamental challenges in chemistry. Moreover, we apply the techniques we developed for identifying individual molecular structures in complex molecular mixtures. For example, in collaboration with the Clean Combustion Institute in Naples, Italy, resolving incipient soot formed in combustion engines [https://www.sciencedirect.com/science/article/pii/S1540748918302839] or, in collaboration with NASA, organic molecules of meteorites [https://onlinelibrary.wiley.com/doi/full/10.1111/maps.13784]. The fundamental insights we obtain provide a deeper understanding with implications for several societal challenges. Our results impact cleaner combustion and with this health and climate change, as well as finding new medicines and improving chemical synthesis and heterogenous catalysis to give examples.

We also developed techniques that allow us to detect and control single-electron charges in single atoms and molecules [https://www.nature.com/articles/ncomms9353]. By that we could measure the reorganization energy of a single molecule [https://www.nature.com/articles/s41565-018-0087-1] – an important parameter for charge transfer. And we could demonstrate chemical reactions based on the attachment and detachment of single electrons [https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.226101]. Bringing the synthesis of molecules by atom manipulation and the control of single-electron charges together, we work towards novel molecular machines that might be constructed on the atomic scale using atom manipulation and which functionality we envisage based on single-electron transfer.

What inspired or motivated you to work on your current research or project?

Already when I started studying physics, the works of Don Eigler and his team at IBM Research Almaden motivated me to working in this research field. About the time the Berlin Wall fell – I was still in high school – they were the first to demonstrate that single atoms could be moved with atom precision. It is inspiring how they took advantage of that breakthrough by building up fantastic experiments on the atomic scale such as quantum corrals and revealed unprecedented insight in quantum mechanical phenomena.

After we developed AFM with atomic lateral resolution on molecules and single-electron charge resolution in 2009, it was the discussion with scientists of different communities that inspired me to tackle some of their – and our society’s – most important challenges by taking advantage of our new technique. Through our experiments with atom resolution, we contribute towards revealing the pathways for soot formation in combustion, to finding new natural products and maybe with that, new medicines, and resolving questions of theoretical chemists, such as: What is the structure or symmetry of a certain molecule, how can it be synthesized, what is its reorganization energy? We advance the atom manipulation techniques pioneered by Eigler and his team to create molecules and induce novel chemical reactions.

I find it highly rewarding to break walls in physics and chemistry that impact our societal challenges, as in soot formation for cleaner combustion or identifying novel natural compounds for new medicines.

In what ways does society benefit from your research?

In our research, resolving single molecules on the atomic scale, we discover novel molecules and novel chemical reactions and provide a deeper fundamental understanding with implications for several societal challenges.

We apply our invented technique as an analytical tool for identifying individual molecular structures in complex molecular mixtures, as incipient soot molecules formed in combustion engines and fuel pyrolysis. In our studies of incipient soot formation, we could reveal long-sought pathways of how molecules grow and merge in the flame. This is among the most important questions of this research field and critical for finding ways towards cleaner combustion. With our results, we contribute to a cleaner combustion, and with this health and climate change.

We resolved natural products and discovered molecules that could not have been identified without our AFM technique. Such new natural products, metabolites that function in nature, provide promising candidates for new cures.

We discover and investigate chemical reactions obtaining atomistic insights into these reactions. Moreover, the investigation of charged molecules, resolving the structural changes when charging a single molecule with one or two electrons, has implications for chemical reactions, catalysis, electrochemistry, photoconversion, and charge transport. With that, we hope to contribute to improvements in photovoltaics, chemical synthesis and heterogeneous catalysis.

Finally, we aim toward single-electron devices, such as novel molecular switches and machines that in the future might find energy-efficient applications in information technology or medicine. On the long path to such applications, we benefit from the atomically defined investigations improving our knowledge of how artificial molecular machines function and advance our understanding of nature, which developed molecular machines and motors by evolution that carry out the most important life tasks.

Looking ahead, what are your hopes or aspirations for the future based on your research or project?

We would like to still get a better understanding of how chemical bonds form and break, and to become better in forming them. We wish to build up more complex custom-designed nanoscale structures molecule-by-molecule, which will lead to increased functionalities. For our understanding, it would be great to resolve bond formation in time and with atomic resolution.

Further information

Further Activities to have a look at