Dramatic femtosecond nonlinear absorption at a strongly coupled porphyrin-graphene nanoconjugate

Edge-functionalization of graphene is emerging as a powerful chemical method for the construction of π-delocalized highly-planar graphene nanoconjugates that are not accessible through surface-supported syntheses. Herein, a graphene-porphyrin nanoconjugate via a robust pyrazine (pz) linkage has been obtained by condensing 2,3-diamino-5,10,15,20-tetraphenylporphyrin (DA-TPP) with ortho-quinone (o-quinone) moieties at edge sites of graphene oxide (GO). The as-prepared GO-pz-TPP exhibits an intense absorption extending from 375 to 900 nm and a high quenching yield (98%) of fluorescence, indicating a strong electronic coupling effect between GO and TPP units. GO-pz-TPP displays strong nonlinear optical (NLO) absorption and giant NLO coefficients with 800 and 1,030 nm fs laser, in sharp contrast to traditional graphene-porphyrin nanohybrids only NLO-active towards ns laser. Such a dramatic NLO performance towards femtosecond pulsed laser has not been achieved in any carbon-chromophores nanohybridized materials to date. This work validates the π-extended edge-functionalization strategy as a means to tune the NLO properties of graphene, thereby providing a new paradigm for the assembly of versatile optoelectronic materials.