Here we present a detailed wavelength scanned surface enhanced Raman excitation spectroscopy (SERES) study on strongly coupled Ag nanoprism/TDBC J-aggregates system. Ag nanoprisms of different localized surface plasmon resonance (LSPR) relative to J-aggregates resonance were synthesized with a seeded growth method. Ag nanoprisms tended to form stacked structure after TDBC J-aggregates were mixed with colloidal Ag nanoprism, which was observed by TEM. The strongly coupled system showed clear Rabi splitting and anti-crossing behavior in the far field extinction spectra indicative of strong coupling. The wavelength scanned surface enhanced Raman excitation profiles of Ag nanoprism/TDBC J-aggregates were measured for a broad excitation wavelength range (515-640 nm) and high resolution (2 nm). The SERES profiles of different samples always only show one-peak structure and don’t have clear correlation with their far field extinction spectra, which deviates from the prediction of the two coupled harmonic oscillator model. The theoretical electrodynamics simulation on the electric field response of single Ag nanoprism and stacked nanoprism structure suggests that the far field extinction and near field Raman response are contributed by different plasmon modes for the strongly coupled system. The Ag nanoprism monomer plasmon mode dominates the far field extinction, while a large portion of Raman signals come from the gap plasmon modes of stacked structure.

Probing a strongly coupled system via surface enhanced Raman excitation spectroscopy

2019 Spring National Meeting

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