Efficient Photosensitizing Capabilities and Ultrafast Carrier Dynamics of Doped Carbon Dots.

Carbon dots (C-Dots) are promising new materials for the development of biocompatible photosensitizers for solar-driven catalysis and hydrogen production in aqueous solution. Compared to common semiconducting quantum dots, C-Dots have good physicochemical, as well as photochemical stability, optical brightness, stability and nontoxicity, while their carbon based source results in tunable surface chemistry, chemical versatility, low cost, and biocompatibility. Herein we show that doping the C-Dots with phosphate or boron significantly influences their excited-state dynamics, which is observed by the formation of a unique long-lived photoproduct as a function of the different dopants.

Strong coupling of collective intermolecular vibrations in organic materials at terahertz frequencies.

Several years ago, strong coupling between electronic molecular transitions and photonic structures was shown to modify the electronic landscape of the molecules and affect their chemical behavior. Since then, this concept has evolved into a new field known as polaritonic chemistry. An important ingredient in the progress of this field was the demonstration of strong coupling with intra-molecular vibrations, which enabled the modification of processes occurring at the electronic ground-state.

Temporal Dynamics of Localized Exciton-Polaritons in Composite Organic-Plasmonic Metasurfaces.

We use femtosecond transient absorption spectroscopy to study the temporal dynamics of strongly coupled exciton-plasmon polaritons in metasurfaces of aluminum nanoantennas coated with J-aggregate molecules. Compared with the thermal nonlinearities of aluminum nanoantennas, the exciton-plasmon hybridization introduces strong ultrafast nonlinearities in the composite metasurfaces. Within femtoseconds after the pump excitation, the plasmonic resonance is broadened and shifted, showcasing its high sensitivity to excited-state modification of the molecular surroundings.

Picosecond optomechanical oscillations in metal-polymer microcavities.

We experimentally study mechanical vibrations in planar Fabry-Perot microcavities made of metallic mirrors and a polymer spacer, using broadband pump-probe spectroscopy. These acoustic waves oscillate at a picosecond time-scale and result in spectral oscillations of the cavity transmission spectrum. We find that the oscillations are initiated at the metal mirrors and that their temporal dynamics match the elastic modes of the polymer layer, indicating that mechanical momentum is transferred within the structure.

Acid effect on excited Auramine-O molecular rotor relaxations in solution and adsorbed on insulin fibrils.

Steady-state and time-resolved UV-Vis spectroscopy techniques were employed to study the non-radiative process of Auramine-O (AuO). We focused our attention on the ultrafast nonradiative decay of Auramine-O in water and on the acid effect on Auramine-O spectroscopy. We found that weak acids like formic acid shorten the excited-state decay times of both the emission and the transient pump-probe spectra of Auramine-O.