Surface plasmons (SPs) are evanescent waves generated through the collective oscillations of electrons at a metal/dielectric interface under optical excitation. Due to the strong light-electron coupling and near-field nature, surface plasmons offer: (1) the opportunity for sub-wavelength spatial confinement of optical waves is enabled; and (2) giant local field enhancement of optical waves is permitted. These unique attributes lead to the long-envisaged optical circuits, and allowed breakthroughs in the generally termed “plasmonics” . For example, in the realizations of optical nano-...
PQI members Hrvoje Petek, Jin Zhao and their colleagues investigated a less known fact about the microscopic details of how the combined optical, electronic and chemical properties of metal/semiconductor interfaces define the coupling of light into the electronic reagents on their recent paper published in Nature Photonics. In this study, they investigated the coherence and hot electron dynamics in a prototypical Ag nanocluster/TiO2 heterojunction via ultrafast two-photon photoemission (2PP) spectroscopy, scanning tunneling microscopy (STM) and density functional theory (DFT). The silver nanoclustors used in this study were grown via e-beam evaporation of Ag on top of TiO2 surface.They have shown that the plasmon excitation, dephasing and hot electron processes that are related to plasmonically enhanced photocatalysis involve complex physical and chemical interactions, with strong interfacial character involving the chemical and plasmonic coupling of Ag nanoclusters and the TiO2 substrate that cannot be predicted by the properties of the component materials, but rather require an understanding of their interactions. They found that the dephasing of the perpendicular and parallel plasmons by the dielectric screening response of the TiO2 substrate generates hot electrons with anisotropic and non-thermal distributions.
Karl Johnson and Jill Millstone will collaborate with Pitt chemistry professor Nathaniel Rosi and Temple chemistry professor Eric Borguet on research funded by a grant from the Defense Threat Reduction Agency's (DTRA) Joint Science and Technology Office (JSTO) within the United States Department of Defense. They will investigate the use of multifunctional metal-organic frameworks (MOFs) with plasmonic cores that can be used to detect and destroy chemical warfare agents and toxic industrial chemicals. The $1.5 M award comes with a 1 M dollar 2 year option period after the initial 3 years. The collaborative team will develop and study new MOF-nanoparticle hybrid materials for the selective detection and destruction of toxic chemicals.