Manipulating Chemistry with Vacuum Light Fields (Manipulight)

Main funder

Research Council of Finland

Funder's project number: 323995

Funds granted by main funder (€)

399 091,00

Funding program

Academy Project, AoF (Research Council of Finland)

Project timetable

Project start date: 01/09/2019

Project end date: 31/08/2023

Summary

Catalysts are the backbone of chemical technology and are available for most, if not all, industrially relevant processes. Since the time and spatial resolutions required to to improve a catalyst or to design a new one, are notoriously difficult to achieve experimentally, much of our knowledge is based on computations, which are nowadays routinely used to investigate catalysis in atomic detail. The standard assumption in such computations is that molecules are surrounded by a 'normal' electromagnetic vacuum field, i.e., the lowest energy state of the quantized electro-magnetic field, also called the vacuum light field. In such situation, coupling to photonic modes is weak and only the electronic and nuclear degrees of freedom matter, which can be described accurately with modern quantum chemistry methods. Although valid for ordinary chemical reactions in regular environments, this assumption breaks down when the vacuum field is modified to the extent that also photonic degrees of freedom become important. This kind of change in the vacuum field is realized rather easily with photonic structures that confine light, such as optical cavities or surface plasmons. The confinement furthermore enhances the light-matter interaction, which can become even strong enough for the molecular degrees and photonic degrees of freedom to hybridize into new light-matter states, the polaritons. The hybridization between light and matter into polaritons not only delocalizes the excitation over many molecules but also changes their potential energy surface, and thus provides a new way to control chemistry.

Previously we have pioneered an approach to include the effect of confined light on the molecular dynamics in atomistic computer simulations. With this method, we could not only interpret experiments on molecules in cavities and near surface plasmons, but also guide new experiments, the most notably of which is the manipulation of excited-state intramolecular proton transfer with an optical cavity. However, the method only includes the effect of optical structures that are tuned to match the bright electronic transitions of the molecules. Although excellently suited therefore for investigating the intriguing effects cavities can have on photochemical reactivity, recent experiments suggest that tuning a cavity to match vibrational transitions might provide a route towards even more versatile or even mode-selective chemistry. Thus, to unlock the full potential of manipulating chemistry with photonic nano- and microstructures, we need to extend our model to also include coupling of the lower (infra-red, IR) frequency cavities to vibrational modes, and demonstrate its validity via experiments.

The extended method for performing atomistic simulations of molecules inside all types of cavities, will go significantly beyond existing theoretical descriptions that are typically limited to low dimensional model systems, and for the first time reveal in full atomistic detail how the interaction with the modified vacuum fields alters the dynamics of real molecules. By addressing the effects of cavities on the molecular dynamics, we will gain comprehensive new insights into the relation between cavity parameters and reactivity. With that information, we will demonstrate experimentally that by fabricating appropriate cavities we can selectively change the reactivity. Thus, our project has the potential to open the door to a totally new type of catalysis with major implications for future technologies, including light harvesting and mode-selective chemical synthesis.