| Chemical functionalization of carbon nanotubes is one of the key challenges towards their use in optoelectronic devices. It aims at combining the versatility of the optical properties of organic molecules with the exceptional transport properties of nanotubes. The delocalized P-electronic system of carbon nanotubes allows them to link non-covalently to a large range of organic molecules. In contrast to covalent functionnalization, this mild interaction preserves most of the intrinsic properties (luminescence for instance) but still leads to a strong enough coupling so to give stable compounds and so to induce new functionnalities. Here we focus on porphyrin molecules that can be attached to single-wall carbon nanotubes by means of the micelle swelling method [1]. An energy transfer [2] from the molecule to the nanotube was recently evidenced by photoluminescence excitation experiments. We report on the quantum efficiency and on the dynamics of this transfer [3]. We first performed 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 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 a quantum yield very close to one (10－5 < 1－ < 10－3). Time-resolved transient absorption spectroscopy also allowed us to track the population of the electronic levels of the compounds subunits and to build an effective transfer scenario. Finally, we will present preliminary results regarding the investigation of energy transfer at the single nanotube level. References [1] C. Roquelet, et al, ChemPhysChem, 11 (2010), pp 1667 [2] G. Magadur et al. ChemPhysChem, 9 (2008),pp 1250 [3] C. Roquelet, et al, Appl. Phys. Lett. 97 (2010), pp 141918 |
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