Valérie Alain-Rizzo

Stable Solution‐Processed Molecular n‐Channel Organic Field‐Effect Transistors

A new solution-processable small-molecule containing electron-poor naphthalene diimide and tetrazine moieties has been synthesized. The optimized spin-coated n-channel OFETs on glass substrate shows electron mobility value up to 0.15 cm(2) V(-1) s(-1) . Inkjet-printed OFETs are fabricated in ambient atmosphere on flexible plastic substrates, which exhibits an electron mobility value up to 0.17 cm(2) V(-1) s(-1) and also shows excellent environmental and operational stability.

Π‐Stacking Functionalization of Carbon Nanotubes through Micelle Swelling

We report on a new, original and efficient method for pi-stacking functionalization of single-wall carbon nanotubes. This method is applied to the synthesis of a high-yield light-harvesting system combining single-wall carbon nanotubes and porphyrin molecules. We developed a micelle-swelling technique that leads to controlled and stable complexes presenting an efficient energy transfer. We demonstrate the key role of the organic solvent in the functionalization mechanism. By swelling the micelles, the solvent helps the non-water-soluble porphyrins to reach the micelle core and allows a strong enhancement of the interaction between porphyrins and nanotubes. This technique opens new avenues for the functionalization of carbon nanostructures.

Quantum efficiency of energy transfer in noncovalent carbon nanotube/porphyrin compounds

We report on the quantum yield of excitation energy transfer in noncovalently bound nanotube/porphyrin compounds. Evidence for energy transfer is gained from photoluminescence excitation experiments. We perform a quantitative evaluation of the transfer quantum yield in the case of (6,5) nanotubes through three independent methods: quantitative photoluminescence excitation measurements, evaluation of the luminescence quenching of the donor (porphyrin) and ultrafast transient absorption measurements. The latter shows a tremendous increase in the porphyrin recovery rate upon incorporation in the compound. All these measurements consistently lead to an exceptional quantum yield: η∼1(10−5<1−η<10−3).

Excitation transfer in functionalized carbon nanotubes.

Tailoring the properties of carbon nanotubes by functionalizing their side-wall is one of the key challenges towards the realization of carbon nanotube-based optoelectronic devices. This technique aims at combining the remarkable transport properties of the tube with the versatility of the optical properties of organic molecules. Herein, we achieve p-stacking functionalization of nanotubes with hydrosoluble porphyrins.

Redox- and Protonation-Induced Fluorescence Switch in a New Triphenylamine with Six Stable Active or Non-Active Forms

The synthesis, photophysical and electrochemical properties as well as theoretical calculation studies of a newly designed triphenylamine derivative are described. This original compound displays one neutral form, three oxidized forms, and two protonated forms with distinct photophysical characteristics. The interplay of the emission with the protonation or the redox state (electrofluorochromism) has been explored and an on-off-on-off fluorescence switching was observed in the case of oxidation and an on-on-off fluorescence switching in the case of protonation.

Redox-controlled fluorescence modulation (electrofluorochromism) in triphenylamine derivatives

The study of the chemical and electrochemical fluorescence switching properties of a family of substituted triphenylamine derivatives is reported. First of all, the synthesis of a family of six compounds is described. They are characterized by electrochemistry, UV-vis and fluorescence spectroscopy and spectroelectrochemistry. Theoretical calculations were performed in order to corroborate the experimental results. While these compounds emit blue to green light under UV irradiation with a large quantum yield (37%) in the case of one molecule, the fluorescence intensity is quenched upon oxidation. The fluorescence behavior can be switched between the strong fluorescent (neutral) state and the non-fluorescent (oxidized) state with a high contrast (around 1500 for the fluorescence intensity for one of these molecules). Furthermore, the chromatic contrast of three of these molecules reaches 70% that can be important for further applications.

Triphenylamine/tetrazine based π-conjugated systems as molecular donors for organic solar cells

Conjugated systems built by connecting one electron-donor triphenylamine to an electron-withdrawing tetrazine have been prepared using various linkers. We describe here the synthesis, the electrochemical properties and some photophysical properties of these molecules, emphasizing the dependence upon the type of linker between the groups and an organic photovoltaic solar cell was prepared with one derivative.

s-Tetrazines functionalized with phenols: synthesis and physico-chemical properties

s-Tetrazines functionalized with phenols substituted by electron withdrawing or electron donating groups have been synthesized. The electrochemical and photophysical properties of these series of compounds have been investigated. All the new tetrazines prepared can be reversibly reduced into their anion-radicals, and the reduction potential of the tetrazine is sensitive (ΔE of 0.1–0.2 V) to the meta- and the para-substitution of the phenoxy group in its 6-position. Whereas tetrazines substituted by phenoxy possessing an electron donating moiety are virtually non emissive, the ones substituted by a phenoxy possessing an electron withdrawing group are fluorescent compounds (quantum yield up to 0.36). Fluorescence quenching experiments have been performed on all the fluorescent compounds. A moderate fluorescence quenching is observed in the presence of toluene, m-xylene and styrene, whereas an efficient quenching occurs in the presence of bisphenol A, in agreement with quenching through a photoinduced electron transfer, which depends on the electron-rich character of the quencher.

Original electroactive and fluorescent bichromophores based on non-conjugated tetrazine and triphenylamine derivatives: towards more efficient fluorescent switches

The synthesis, photophysical and electrochemical properties and their interplay as well as theoretical calculations studies of newly designed fluorescent and electroactive derivatives are described. These molecules are composed of two fluorophores: one triphenylamine, electron-rich unit, and one tetrazine, electron-poor unit, connected by two different links. While in the neutral state the bichromophores are not fluorescent, due to a photoinduced electron transfer from the triphenylamine unit to the tetrazine unit, the fluorescence is restored in the oxidative state (oxidation of the triphenylamine moiety).

Novel s-tetrazine-based dyes with enhanced two-photon absorption cross-section

This paper reports the synthesis and the linear and non-linear absorption properties of a series of new tetrazine-based D–π–A–π–D and D–π–A type dyes. In these derivatives, a central tetrazine core was connected with one or two terminal triphenylamine moiety(ies) via various π-conjugated spacers. These compounds were efficiently synthesized by Stille or Suzuki–Miyaura cross-coupling as a key step. Their photophysical properties, including one-photon absorption and two-photon absorption (2PA), were investigated with special attention to structure–property relationships. Large 2PA cross-sections (>800 GM) of these tetrazine dyes were evaluated by open aperture z-scan and non-degenerate 2PA techniques. The strong 2PA of these molecules is attributed to the extended π system and to the enhanced intramolecular charge transfer between the triphenylamine donor and the center tetrazine acceptor.