Exciton Generation in Semiconductor Nanocrystals via the Near-Field Plasmon Energy Transfer

Abstract

The plasmon resonance of small-diameter metal nanoparticles has a unique decay character, as it produces almost no far field scattering. Instead, most of the absorbed light is emitted in the near field (NF), phenomenon also known as strong field localization. Such non-radiative emission is short lived and decays primarily via the production of heat, which prevents efficient harvesting of the NF energy.Here, we demonstrate a general strategy for coupling the NF radiation of surface plasmons to long-lived optical excitations in semiconductor nanocrystals (NCs). This concept was manifested through the observation of an enhanced exciton generation in CdSe NCs coupled to 5-nm Au nanoparticles. To distinguish the plasmon antenna effect from photoinduced charge transfer processes, both Au and CdSe nanoparticles were encapsulated into insulating CdS or ZnS matrices. A unique signature of the plasmon to exciton energy transfer was observed in photoexcitation measurements that unambiguously correlate the increase in the CdSe exciton population with the excitation of plasmon modes in Au domains. The demonstrated scheme for harvesting the NF radiation of metal nanoparticles presents an excellent opportunity for extracting the evanescent emission of surface plasmons that can find practical applications in photovoltaic or photocatalytic technologies.

Self‐Assembled Au/CdSe Nanocrystal Clusters for Plasmon‐Mediated Photocatalytic Hydrogen Evolution

“…A very limited amount of work has been reported to date examining plasmon‐induced charge and energy transfer in CdSe‐based systems. Even fewer studies have focused on plasmon‐mediated photocatalytic reactions involving Au/CdSe materials, due primarily to synthetic difficulties of assembling the two components together while maintaining good dispersibility in aqueous media …”

Hot Electrons in TiO2–Noble Metal Nano-Heterojunctions: Fundamental Science and Applications in Photocatalysis

“…Surface plasmons have even been demonstrated to radiate the Franck–Condon structured emission of a molecular fluorophore, wherein the energy spacing between the vibronic energy levels remains similar to their separation in the molecule’s absorption spectrum [ 181 ]. Plasmon-to-exciton energy transfer mediated by Coulombic interactions (similar to Fӧrster-type resonance energy transfer in excitonic systems) can occur wherein the emission of the dye or semiconductor is enhanced (pumped) by the additional absorption associated with the plasmon resonance [ 182 ]. Yet another possibility is the hybridization of the plasmon and exciton to form a plexcitonic state, wherein splitting and shifting of the absorption and PL peaks are typically observed [ 183 ].…”

Surface plasmon resonance enhancement of photoluminescence intensity and bioimaging application of gold nanorod@CdSe/ZnS quantum dots

“…In the past decades, quantum dots (QDs) have proven to be increasingly useful for their unique features [1–5]. The light emission from QDs can be easily tuned from the visible to the near-infrared (NIR) spectrum.…”