Molecules as switches for sustainable light-driven technologies
A team of LMU researchers identifies new mechanisms of plasmonic attenuation
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Metal nanostructures can concentrate light so strongly that they can trigger chemical reactions. The key players in this process are plasmons - collective oscillations of free electrons in the metal that concentrate energy into extremely small volumes. A new study published in the journal Science Advances now shows how crucial adsorbed molecules are for how quickly these plasmons lose their energy.
The team led by LMU nanophysicists Dr. Andrei Stefancu and Professor Emiliano Cortés identified two fundamentally different mechanisms of chemical interface damping (CID), i.e. plasmonic damping caused by adsorbed molecules. Which mechanism dominates depends on how the electronic states of the molecule are aligned with those of the metal surface - in this case gold. This alignment is even reflected in the electrical resistance of the material.
Two mechanisms identified
In the first mechanism, the molecule absorbs the energy directly and resonantly: if the plasmon energy corresponds to an unoccupied electronic state of the molecule, an electron can immediately transition to this state. This process is extremely fast and strongly dependent on the color (energy) of the incident light.
The second mechanism works without such resonant excitation. Instead, electrons undergo diffuse, inelastic scattering at the interface between the gold surface and the molecule. This scattering causes the plasmons to lose energy - and at the same time increases the electrical DC resistance of the gold. The study shows that this scattering process and plasmonic attenuation are closely linked.
The results combine two phenomena that were previously studied separately: electrical surface effects and plasmonic energy transfer. They show that the energy flow between light, metal and molecules can be specifically controlled simply by the choice of molecules adsorbed on the surface. This opens up new possibilities for light-driven catalysis, sensor technologies and energy-efficient chemical processes.
The study was made possible by an international collaboration with researchers from Imperial College London, the Universidad de La Laguna in Tenerife and Rice University, who worked together with the LMU team. As Emiliano Cortés points out: "These findings show that the energy flow at the nanoscale can be specifically tuned by molecular design, opening up new possibilities for technology transfer and practical applicability. This is an important step towards sustainable processes that use sunlight to carry out chemical reactions, including the production of fuels and valuable chemical products."
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
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