Broadband Two-Photon Absorption Characteristics of Highly Photostable Fluorenyl-Dicyanoethylenylated [60]Fullerene Dyads

• Published in: Molecules (Basel, Switzerland) Vol. 21; no. 5; p. 647
• Main Authors: Jeon, Seaho, Wang, Min, Ji, Wei, Tan, Loon-Seng, Cooper, Thomas, Chiang, Long Y
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 14-05-2016; MDPI AG
• Subjects: C60-(light-harvesting antenna) nanostructures; Crystallization; Fluorenes - chemistry; Fullerenes - chemistry; Light; nonlinear absorption; Photons; Triazines - chemistry; ultrafast two-photon absorption; Z-scan measurements; ultrafast two-photon absorption; Z-scan measurements; nonlinear absorption; C60-(light-harvesting antenna) nanostructures
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules21050647

We synthesized four C60-(light-harvesting antenna) dyads C60 (>CPAF-Cn) (n = 4, 9, 12, or 18) 1-Cn for the investigation of their broadband nonlinear absorption effect. Since we have previously demonstrated their high function as two-photon absorption (2PA) materials at 1000 nm, a different 2PA wavelength of 780 nm was applied in the study. The combined data taken at two different wavelength ranges substantiated the broadband characteristics of 1-Cn. We proposed that the observed broadband absorptions may be attributed by a partial π-conjugation between the C60 > cage and CPAF-Cn moieties, via endinitrile tautomeric resonance, giving a resonance state with enhanced molecular conjugation. This transient state could increase its 2PA and excited-state absorption at 800 nm. In addition, a trend of concentration-dependent 2PA cross-section (σ₂ ) and excited-state absorption magnitude was detected showing a higher σ value at a lower concentration that was correlated to increasing molecular separation with less aggregation for dyads C60(>CPAF-C18) and C60(>CPAF-C₉), as better 2PA and excited-state absorbers.