Direct Excitation Transfer in Plasmonic Metal-Chalcopyrite-Hybrids: Insights from Single Particle Line Shape Analysis

Hybrid nanomaterials containing both noble metal and semiconductor building blocks provide an engineerable platform for realizing direct or indirect charge and energy transfer for enhanced plasmonic photoconversion and photocatalysis. In this work, silver nanoparticles (AgNPs) and chalcopyrite (CuFeS₂) nanocrystals (NCs) are combined into a AgNP@CuFeS₂ hybrid structure comprising NCs embedded in a self-assembled lipid coating around the AgNP core. In AgNP@CuFeS₂ hybrid structures, both metallic and semiconductor NCs support quasistatic resonances. To characterize the interactions between these resonances and their effect on potential charge and energy transfer, direct interfacial excitation transfer between the AgNP core and surrounding CuFeS₂ NCs is probed through single particle line shape analysis and supporting electromagnetic simulations. These studies reveal that CuFeS₂ NCs localized in the evanescent field of the central AgNP induce a broadening of the metal NP line shape that peaks when an energetic match between the AgNP and CuFeS₂ NC resonances maximizes direct energy transfer. Dimers of AgNPs whose resonances exhibit poor energetic overlap with the CuFeS₂ NC quasistatic resonance yield much weaker line shape broadening in a control experiment, corroborating the existence of resonant energy transfer in the AgNP@CuFeS₂ hybrid. Resonant coupling between the metallic and semiconductor building blocks in the investigated hybrid architecture provides a mechanism for utilizing the large optical cross-section of the central AgNP to enhance the generation of reactive charge carriers in the surrounding semiconductor NCs for potential applications in photocatalysis.