Broadband optical limiting optimisation by combination of carbon nanotubes and two-photon absorbing chromophores in liquids

International audienceWe report here on the optical limiting studies performed with nanosecond laser pulses on several families of multiphoton absorbers in chloroform, with carbon nanotubes suspended in solutions. Performances of these samples are compared with those of simple multiphoton absorber solutions and carbon nanotube suspensions, and the differences observed are interpreted in terms of cumulative NLO effects and adverse aggregation phenomenon

Dendritic fluorene oligomers for nonlinear absorption in the visible range

International audienceWe report here the nonlinear absorption properties of dendritic molecules of oligofluorenes. Measurements were performed in chloroform between 450 and 650 nm for nanosecond time duration pulses. The nonlinear absorption is attributed to a three-photon absorption process involving first a two-photon absorption (TPA) step followed by an excited state absorption (ESA) process. The corresponding three-photon absorption coefficient α3 presents at resonance high values (α3 > 10000 cm3/GW2 for 2G1 the first dendrimer generation bearing a bifluorene at a concentration of 50 g/L). These values are strongly enhanced with respect to those obtained in the same conditions for analog linear oligofluorenes

Excitonically Coupled Oligomers and Dendrimers for Two-Photon Absorption

International audienceThe first part of this review presents the state of the art on two-photon absorbing molecules. Earlyworks concerned the optimization of dipolar push–pull molecules. Recently, the synthesis of linearand branched centrosymmetrical quadrupolar molecules led to higher nonlinearities, but still far from reachingthe fundamental limits of molecular two-photon cross-sections.The second part of this review summarizes our theoretical and experimental results on fluorene-basedoligomers, and branched oligomers (V-shape molecules and dendrimers). They are model molecules to investigatean alternative approach based on spatial assemblies of nonsubstituted π-electronsystems that are coupled by dipole–dipole interactions. In all geometries, two-photon absorptioncross-sections have superlinear dependencies that depend on coupling energies and oligomer sizes. Theseresults are well rationalized by an excitonic model based on N interactingthree-level systems. Analytical expressions for one-photon and two-photon energies and absorption strengthsare derived for linear oligomers. An accurate calculation of large exitonic systems is obtained by diagonalizingthe Hamiltonian operator on a reduced basis set

Bifluorene Derivatives for Two-Photon Absorption in the Visible Range

International audienceWe report here linear and two-photon absorption (TPA) properties of bifluorene derivatives of different symmetries. C2v and octupolar symmetries induce a significant enhancement of molecule TPA efficiency. These properties are interpreted in terms of coupling interactions between the different branches of molecules

Design of pyridine-dicarboxamide ligands for the sensitization of europium(III) by two photon antenna effect

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Synthesis, and two photon absorption properties of 7,7′-(iminundecahydro-closo-dodecaborate)-9,9′-(dihexyl)-2,2′-bifluorene

International audienceHybrid organic–inorganic bis-tetrabutylammonium-7,7′-(iminundecahydro-closo-dodecaborate)-9,9′-(dihexyl)-2,2′-bifluorene (5) was prepared, and the influence of the closo-dodecaborate cluster on the two-photon absorption properties of bi-fluorene derivatives was demonstrated

Neutral push-pull chromophores for nonlinear optical imaging of cell membranes.

International audienceA new class of push-pull molecules was recently identified, based on pyridine dicarboxamide as an electron acceptor group and bearing a fluorenethynyl pi-conjugated bridge. The molecules present good second and third order nonlinear properties, with a static quadratic hyperpolarisability mubeta (at 1.907 microm) of 320 x 10(-48) esu (mubeta(0) = 249 x 10(-48) esu) and a maximum two-photon absorption cross-section of 1146 GM. Starting from this generic structure, we designed a series of eight amphiphilic nonlinear probes, varying the length of the lipophilic tail and the nature of the polar head, and tested their cell membrane affinity by nonlinear optical imaging. A good membrane affinity was observed with probes bearing short alkyl chains and carbohydrate moieties as the polar head, emphasizing the importance of the lipophilic-hydrophilic balance, as well as the role of the polar head. This original approach based on carbohydrate head groups is an important advancement in the design of membrane probes, since these highly versatile functional groups confer adequate hydrophilicity and yet conserve overall molecular neutrality

Synthesis, structures, optical properties, and TD-DFT studies of donor-p-conjugated dipicolinic acid/ester/amide ligands

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