Title
Plasmonic Silver Nanoprism-Induced Emissive Mode Control between Fluorescence and Phosphorescence of a Phosphorescent Palladium Porphyrin Derivative
Author
Naoto Takeshima, Kosuke Sugawa, Hironobu Tahara, Shota Jin, Hiroki Wakui, Misa Fukushima, Kyo Tokuda, Shuto Igari, Kotomi Kanakubo, Yutaro Hayakawa, Ryuzi Katoh, Kouichi Takase, Joe Otsuki
Year
2019
Journal
ACS Nano
Abstract
We have succeeded in significantly enhancing fluorescence from intrinsically phosphorescent palladium octaethylporphyrin (Pd-porphyrin) that has an intersystem crossing efficiency of ∼1 by using silver nanoprisms (AgPRs). This was achieved by controlling the wavelength of the localized surface plasmon (LSP) resonance of AgPRs and the distance between the Pd-porphyrin molecules and the AgPR surfaces. In addition to enhancing phosphorescence by spectrally overlapping the phosphorescence band with the LSP resonance band, tuning the LSP wavelength to approximately 520 nm led to the appearance of a new emission band around the wavelength corresponding to the fluorescent radiation. The appearance of fluorescence suggests that the nonradiative energy transfer from the singlet excited state of Pd-porphyrin to the LSP of AgPRs overcame the ultrafast intramolecular intersystem crossing to the triplet excited state, manifesting the spectral properties of the singlet excited state of Pd-porphyrin. The fluorescence nature of this radiation was strongly supported by lifetime measurements of the hybrids of Pd-porphyrin and AgPRs. Furthermore, the dependence of the emissive intensities on the distance between the Pd-porphyrin molecules and the AgPR surfaces showed interesting opposite trends. The fluorescence intensity was increased as the distance between the molecules and the AgPRs was decreased from 10.5 to 1 nm, while the phosphorescence intensity was decreased, which indicates that the LSP-induced fluorescence radiation process from Pd-porphyrin near the AgPRs outweighed the quenching by the AgPRs, even though the phosphorescence significantly suffered quenching.
Full Article
Instrument
V-630, FP-8600
Keywords
Absorption, Fluorescence, Optical properties, Chemical stability, Nanostructures, Materials