Linear and nonlinear optical properties of photoresponsive [60]fullerene hybrid triads and tetrads with dual NIR two-photon absorption characteristics

Abstract

Two C60-(antenna)x analogous compounds having branched hybrid triad C60(>DPAF-C18)(>CPAF-C 2M) and tetrad C60(>DPAF-C18)(>CPAF- C2M)2 nanostructures were synthesized and characterized. The structural design was intended to facilitate the ultrafast femtosecond intramolecular energy transfer from photoexcited C60[> 1(DPAF)*-C18](>CPAF-C2M) 1or2 or C60(>DPAF-C18) [>1(CPAF)*-C2M]1or2 to the C 60> cage moiety upon two-photon pumping at either 780 or 980 nm, respectively. The latter nanostructure showed approximately equal extinction coefficients of optical absorption over 400-550 nm that corresponds to near-IR two-photon-based excitation wavelengths at 780-1100 nm for broadband nonlinear optical (NLO) applications. Aside from their enhanced two-photon absorption (2PA) activity at 780 nm, we also demonstrated ultrafast photoresponses at 980 nm showing 2PA cross-section (σ2) values of 995-1100 GM for the hybrid tetrad. These σ2 values were correlated to the observed good efficiency in reducing femtosecond light-transmittance down to 35% at the light intensity of 110 GW/cm2. Accordingly, 2PA characteristics of these nanostructures at multiple NIR wavelengths provided support for their suitability in uses as broadband NLO nanomaterials at 600-1100 nm that includes the 2PA ability of two antenna, DPAF (700-850 nm) and CPAF (850-1100 nm), and the fullerene cage at shorter wavelengths (600-700 nm). © 2013 American Chemical Society.