title: Linear and Nonlinear Optical Properties of Photoresponsive [60]Fullerene Hybrid Triads and Tetrads with Dual NIR Two-Photon Absorption Characteristics.
abstract: Two C60-(antenna)xanalogous compounds having branched hybrid triad C60(>DPAF-C18)(>CPAF-C2M) and tetrad C60(>DPAF-C18)(>CPAF-C2M)2nanostructures were synthesized and characterized. The structural design was intended to facilitate the ultrafast fs intramolecular energy-transfer from photoexcited C60[>1(DPAF)*-C18](>CPAF-C2M)1or2or C60(>DPAF-C18)[>1(CPAF)*-C2M]1or2to the C60> 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 photo-responses at 980 nm showing 2PA cross-section (σ2) values of 995-1100 GM for the hybrid tetrad. Theseσ2values were correlated to the observed good efficiency in reducing fs 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).
authors.affiliation: Department of Chemistry, Institute of Nanoscience and Engineering Technology, University of Massachusetts, Lowell, MA 01854, USA.
authors.forename: Seaho
authors.initials: S
authors.lastname: Jeon
authors.forename: Joy
authors.initials: J
authors.lastname: Haley
authors.forename: Jonathan
authors.initials: J
authors.lastname: Flikkema
authors.forename: Venkatram
authors.initials: V
authors.lastname: Nalla
authors.forename: Min
authors.initials: M
authors.lastname: Wang
authors.forename: Matthew
authors.initials: M
authors.lastname: Sfeir
authors.forename: Loon-Seng
authors.initials: LS
authors.lastname: Tan
authors.forename: Thomas
authors.initials: T
authors.lastname: Cooper
authors.forename: Wei
authors.initials: W
authors.lastname: Ji
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hamblin
authors.forename: Long Y
authors.initials: LY
authors.lastname: Chiang
keywords: C60-(antenna)x nanostructures; NIR two-photon absorption; broadband NLO materials; femtosecond light-transmittance reduction; ultrafast intramolecular energy-transfer