Tilting a ground-state reactivity landscape by vibrational strong coupling.

Many chemical methods have been developed to favor a particular product in transformations of compounds that have two or more reactive sites. We explored a different approach to site selectivity using vibrational strong coupling (VSC) between a reactant and the vacuum field of a microfluidic optical cavity. Specifically, we studied the reactivity of a compound bearing two possible silyl bond cleavage sites-Si-C and Si-O, respectively-as a function of VSC of three distinct vibrational modes in the dark. The results show that VSC can indeed tilt the reactivity landscape to favor one product over the other. Thermodynamic parameters reveal the presence of a large activation barrier and substantial changes to the activation entropy, confirming the modified chemical landscape under strong coupling.

Coherent coupling of molecular resonators with a microcavity mode.

The optical hybridization of the electronic states in strongly coupled molecule-cavity systems have revealed unique properties, such as lasing, room temperature polariton condensation and the modification of excited electronic landscapes involved in molecular isomerization. Here we show that molecular vibrational modes of the electronic ground state can also be coherently coupled with a microcavity mode at room temperature, given the low vibrational thermal occupation factors associated with molecular vibrations, and the collective coupling of a large ensemble of molecules immersed within the cavity-mode volume. This enables the enhancement of the collective Rabi-exchange rate with respect to the single-oscillator coupling strength. The possibility of inducing large shifts in the vibrational frequency of selected molecular bonds should have immediate consequences for chemistry.

Probing the kinetics of lipid membrane formation and the interaction of a nontoxic and a toxic amyloid with plasmon waveguide resonance.

The kinetics of formation of solid-supported lipid model membranes were investigated using a home-made plasmon waveguide resonance (PWR) sensor possessing enhanced properties relative to classic surface plasmon resonance sensors. Additionally, the kinetics of interaction of two amyloid peptides with zwitterionic and anionic membranes and their effect on lipid organization were followed.

Figure-of-merit enhancement of surface plasmon resonance sensors in the spectral interrogation.

We show that adding a thin dielectric layer with high refractive index on top of the metallic layer in surface plasmon resonance sensors in the Kretschmann-Raether configuration in the spectral mode causes a redshift of the resonance wavelength, narrowing of the resonance dip, and an enhancement to the spectral sensitivity. Surprisingly, together with the sensitivity enhancement, the dip becomes much narrower and the figure of merit is considerably improved, particularly in the IR range.