Non-equilibrium electron and energy transfer dynamics for plasmonic nanoparticles and their assemblies will be described. Plasmon-resonant excitation of gold nanoparticles generates a non-equilibrium electron gas, which can mediate carrier transfer across material interfaces. The mechanisms of plasmon-based electronic relaxation and energy transfer have been difficult to resolve. The inhomogeneous line widths obtained from coherent two-dimensional electronic spectroscopy (2DES) are sensitive to metal Fermi level carrier densities. Hence, 2DES provides a sensitive probe of electron dynamics on short time scales. As one example, the use of sub-15 fs optical pulses to resolve electron-electron scattering for plasmon-supporting nanorods will be described. For these samples, the time-dependent inhomogeneous linewidth  broadening was monitored over a time scale spanning 10s to 100s of femtoseconds. Analysis of these data yield electronic relaxation rates that exhibited quadratic dependences on laser excitation pulse energies, in agreement with the Fermi liquid model. The 2DES method was also used to distinguish electron and hole transfer for multi-component systems by monitoring time-dependent changes to electronic carrier densities at the metal Fermi level.

Probing non-equilibrium electron transfer in plasmonic assemblies using two-dimensional electronic spectroscopy

2019 Fall National Meeting

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