Charge, Energy transfer and chemical Reactions with molecules in an electromagnetic Cavity – CERCa
Charge, Energy transfer and chemical Reactions with molecules in an electromagnetic Cavity (CERCa)
The emergent field of cavity-induced chemistry opens the way to engineer and control the kinetics of chemical reactions for molecular systems confined inside a cavity-QED setup. We will investigate two relevant cases for chemistry: (i) passing an electronic current across the tip of an STM plasmonic hot-spot involving single to few molecules, (ii) using a stationary flow of reactants in solution, entering and leaving an open-chemical reactor made of a nano-fluidic optical cavity.
We propose to investigate original and innovative nano-probes and open chemical nano-reactors in order to initiate, probe and modulate the rate of chemical reactions at the nanoscale.
Recent progresses in nanotechnology led to a new generation of nano-structures playing the role of electromagnetic cavities, like plasmonic structures, organic micro-cavities and nano-fluidic Fabry-Pérot cavities. Of particular interest, is the possibility to confine inside such a nano-cavity a solution of complex organic molecules and to further study their optical and chemical properties.<br />Recent experiments were performed on sub-micrometer cavities, that exhibit a cavity photon-mode of frequency located in the optical range, that is resonant with a molecular transition. The conjunction of a large dipole moment of the embedded organic molecules, weak effective cavity volume, and favorable scaling of the coupling strength with the molecules’ concentration, results in the formation of hybrid molecule-cavity polaritons.<br />The formation of hybrid cavity polaritons has important consequences on the physical and chemical properties of the confined molecules. In particular, it has remarkable effects on the kinetics of chemical reactions and was shown to be responsible for a significant slowing-down of photochromic chemical reaction rates, compared to the case of absence of cavity.<br />The emergent field of cavity-induced chemistry thus opens the way to engineer and control the kinetics of chemical reactions of molecular systems confined inside a cavity-QED setup. We propose to investigate original and innovative nano-probes and open chemical nano-reactors in order to initiate, probe and modulate the rate of chemical reactions at the nanoscale. We will investigate two relevant cases for chemistry: (i) passing an electronic current across the tip of an STM plasmonic hot-spot involving single to few molecules, (ii) using a stationary flow of reactants in solution, entering and leaving an open-chemical reactor made of a nano-fluidic optical cavity.
We describe the strong-coupling between electronic or vibrational molecular degrees of freedom and a cavity photon mode, and incorporate them into the theoretical description of chemical reactions.
We computed the polaritonic potential energy surface of a photoisomerization chemical reaction of organic molecules confined inside a Fabry-Perot cavity. We included properly the role of the solvent into the calculation of the reaction rate. We have shown that the reaction rate is significantly altered by the confinement, despite the strong dissipation rate due to the coupling to the environment. We included the computation of dissipation and dephasing rates due to the coupling between the molecule and cavity mode to the environment (cavity losses, solvent and internal molecular vibrational modes). We described the whole photochemical mechanism for the chemical reaction and computed the time evolution of the difference between the concentration of the excited charge-transfer state inside and outside cavity, after a single UV photon has been absorbed to initiate the reaction. We have shown the importance of considering the losses induced by coupling the polariton to the cavity and solvent. This ultrafast picosecond dynamics could be measured in state-of-the-art a pump-probe experiment.
We also investigated the coupling between the electrical tunneling current passing across a single molecule and a plasmonic mode located at the hot-spot of a scanning tunneling microscope. We investigated theoretically this system in the experimentally relevant limit of large damping rate for the cavity mode and arbitrary coupling strength to a single-electronic level. We found that for bias voltages close to the first inelastic threshold of photon emission, the emitted light displays antibunching behavior with vanishing second-order photon correlation function. Our theory thus predicts that strong coupling to a single level allows current-driven nonclassical light emission and thus opens new ways for quantum technologies in order to design electrically driven single photon sources.
As a perspective for the part related to the investigation of chemical reaction rates in Fabry-Perot cavities, we are currently including the collective coupling to N molecules in the full model of the reaction dynamics, taking into account the other sources of losses, like the photon losses of the cavity. The next step in the project will be to deal with open chemical reaction configurations (coupling to a hydrodynamics flows), in which a flow of reactants enters the cavity and leaves it after having reacting with the cavity photon-mode.
As a perspective for the part related to passing an electrical current inside a STM plasmonic cavity, a natural extension of this work would be to investigate and extend our theoretical approach to a molecule with two electronic levels both coupled to the plasmonic cavity mode and to local molecular vibrational modes.
Teaching courses. R. A. gave a 12 hours course at the University of Bordeaux opened to M2 PhD students, postdocs and researchers entitled “Introduction to Marcus Theory of charge transfer chemical reactions” .
29/03/2019: Lesson I “Introduction to Marcus Theory. Some necessary physical backgrounds”.
04/04/2019: Lesson II “CT reaction seen as a multiphonon relaxation process I”.
05/04/2019: Lesson III “CT reaction seen as a multiphonon relaxation process II”.
08/04/2019: Lesson IV “CT reaction seen as a multiphonon relaxation process III”.
12/04/2019: Lesson V “Molecular electronics & Marcus theory I”
15/04/2019: Lesson VI “Molecular electronics & Marcus theory II”.
Published paper : Q. Schaeverbeke, R. Avriller, T. Frederiksen, and F. Pistolesi, “Single-Photon Emission Mediated by Single-Electron Tunneling in Plasmonic Nanojunctions”, Phys. Rev. Lett. 123, 246601 (2019).
Oral presentations.
17-20/12/2018: International conference ElecMol2018, Paris, oral presentation of R. A. “Charge-
transfer chemical reactions for molecular populations confined inside a nanofluidic Fabry-Perot
cavity”.
27-31/10/2019: International conference 704. WE-Heraeus-Seminar, Explorig the Limits of
Nanoscience with Scanning Probe Methods, Bad Honnef, invited talk of R. A. “Single-photon
emission mediated by single-electron tunneling in plasmonic nanojunctions”.
Poster presentations.
22-26/04/2019: International workshop Discussions on Nano & Mesoscopic Optics DINAMO,
Galápagos Islands, poster of K. Caicedo.
08-10/07/2019: International workshop MolecularPolaritonics2019: Theoretical and Numerical
Approaches, Madrid, poster of R.A.
03-04/10/2019 : GDR MecaQ, Palaiseau, poster of L. Mauro.
02-04/12/2019 : GDR Physique Quantique Mésoscopique, Aussois, poster of L. Mauro.
In this ANR project, we propose original and innovative nano-probes and open chemical nano-reactors in order to initiate, probe and modulate the kinetics of chemical reactions at the nanoscale. This purpose will benefit from advances in designing a new generation of electromagnetic cavities, like plasmonic nano-structures, organic micro-cavities and nano-fluidic Fabry-Pérot cavities. Recent experimental findings indeed reported the reach of light-matter strong-coupling regime in such cavities, which was shown to be responsible for a significant slowing-down of chemical reactions for molecules embedded inside the cavity. In this project, we will imagine, investigate theoretically and propose a new class of open chemical nano-reactors, where the reactants entering an electromagnetic nano-cavity, undergoes chemical reactions otherwise not or hardly possible in absence of the cavity. More specifically, we will explore from a theoretical point of view, physical and chemical properties of a collection of molecules confined in such an electromagnetic nano-cavity. We wish in this way to identify crucial physical ingredients, related to the strong-coupling between electronic or vibrational degrees of freedom of the embedded molecules and a cavity photon mode, and to incorporate them into the description of chemical reactions. In the first part of the project, we will investigate the impact of passing of an electronic current across the tip of an STM plasmonic hot-spot on chemical reactions involving single to few molecules. The role of current-excited vibrational modes of the molecule is of particular interest as they provide an additional non-radiative decay channel for the reaction mediated by a non-equilibrium mode of the environment. In the second part of the project, we will investigate electron transfer reactions in open-chemical reactors made of a nano-fluidic optical cavity. A stationary flow of fluid containing photochromic molecules in solution enters the cavity, undergoes chemical reactions, and finally leaves the cavity. We will calculate the rate of charge-transfer chemical reactions between donor-acceptor molecules in such cavities. For this purpose, we will develop a generalized-form of Marcus theory of charge-transfer chemical reactions, taking into account the coupling to a non-equilibrium hybrid-polariton mode of the cavity. At the heart of the theoretical approach proposed in this ANR project is the new concept of “reacton”, namely the collective entity built-up by the reactant of the chemical reaction strongly-hybridized to the cavity photon mode plus its immediate environment. The ambition of this project is thus to incarnate this concept of reacton into a quantitatively working theory and to compute the kinetics and efficiency of charge-transfer chemical reactions in such nano-reactors. We will finally compute experimentally measurable observables to quantify the kinetics of the reaction by reading for instance to the time-dependent optical absorption of the cavity in the case of a nano-fluidic reactor or to the electronic current in the case of the STM plasmonic hot-spot. The total efficiency of the chemical reaction will be obtained by computing the ratio between the products and reactants concentrations’ in and out the cavity. At the end of the project, we aim at proposing a specific experimental realization of the proposed nano-reactors. Such open electromagnetic nano-cavities play the role of a new type of catalytic environment that could lead to a breakthrough in studying elementary mechanisms of chemical reactions happening in complex biological or chemical systems.
Project coordination
Rémi Avriller (LABORATOIRE ONDES ET MATIERE D'AQUITAINE)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
Partnership
LOMA LABORATOIRE ONDES ET MATIERE D'AQUITAINE
Help of the ANR 160,110 euros
Beginning and duration of the scientific project:
September 2018
- 48 Months
