Resonance Energy Transfer in Hybrid Plasmonic-Polymetallophthalocyanine Nanoantennas Fabricated By Electropolymerization

Abstract

Metal nanoparticles have exceptionally high photon absorption cross-sections at energies that excite a localized surface plasmon resonance compared to non-metallic particles. The light energy absorbed by these metal “nanoantennas” can be transferred non-radiatively to a coupled semiconductor material. The energy is stored in the semiconductor as electron-hole pairs through the dephasing of localized surface plasmon dipoles. The electrons and holes can then be extracted for charge transfer applications, such as catalysis. Here, we show that individual gold nanorods can be selectively coated via electropolymerization with metallophthalocyanines, a well-established class of oxygen and carbon dioxide reduction catalysts, to produce hybrid plasmonic-polymeric nanoantennas. The semiconducting polymer coatings have a high density of π-π* dipole transitions with energies matching the dipole resonance energy of the gold nanorods, enabling efficient dipole-dipole coupling. Using in situ hyperspectral dark-field imaging, we observed large plasmon resonance linewidth increases in the scattering spectra of single gold nanorods with the anodic deposition of the polymer coating, and attribute this to a greatly decreased plasmon dephasing time due to resonance energy transfer. In situ single particle spectroscopy was required to reveal that the increase in resonance linewidth was dependent on the polymer thickness and the energy of the uncoated gold nanorod longitudinal plasmon resonance. Permeable metallophthalocyanine polymer coatings are spectroscopically and chemically tunable, and have a high effective surface area opening up new opportunities for plasmonic antenna-reactor electrodes in energy sustainability applications.