Photoluminescence spectroscopy of a single non-covalent carbon nanotube/porphyrin complex.
Résumé
The chemical functionalization of single-wall nanotubes (SWNTs) with dye molecules is a promising way for combining the exceptional transport properties of the nanotube and the tunability of optical properties of the chromophores in view of future carbon-based applications such as photovoltaic and other optoelectronic nanodevices. -stacking functionalization of porphyrin (TPP) molecules using a micelle swelling method was achieved recently, yielding stable and reproducible compounds [1]. Photoluminescence (PL) measurements on ensembles of such complexes evidenced a soft enough functionalization so to preserve the intrinsic properties of NTs, and yet an e cient energy transfer from the TPP to the NT [2]. In the view of overcoming the inhomogeneous e ects of ensembles studies, we report here on preliminary investigations of PL properties of such molecular assemblies at the scale of a single object lying on a quartz substrate. We run confocal spectroscopy with a HeNe laser (633 nm) excitation corresponding to the S22 transition energy of (6,4) NTs and observe spatially localized and linearly polarized light emissions. PL spectra show single peaks corresponding to the S11 transition of the minority chirality (6,4) of the sample. This brings evidence for single NTs as emitters. Further investigations are in progress, introducing the variation of the temperature, the wavelength and polarization of the excitation light, coupled with AFM imaging. That will lead to a better understanding of both structural (in uence of the substrate, surface coverage of the NT by the TPP) and optoelectronic (spectral shifts, transfer mechanisms) properties of the complex. References [1] C. Roquelet, ChemPhysChem 2010, 11, 1667-1672.