title: Synthesis, characterization, and photoinduced electron transfer in functionalized single wall carbon nanohorns.
abstract: Single-wall carbon nanohorns (SWNHs) are a new class of material that is closely related to single-wall carbon nanotubes. Here, we describe the synthesis and characterization of a series of SWNHs functionalized with ethylene glycol chains and porphyrins. Functionalization of carbon nanohorns has been achieved using two different synthetic protocols: (1) direct attack of a free amino group on the nanohorn sidewalls (nucleophilic addition) and (2) amidation reaction of the carboxylic functions in oxidized nanohorns. The nanohorn derivatives have been characterized by a combination of several techniques, and the electronic properties of the porphyrin/nanohorn assemblies (SWNH/H2P) have been investigated by electrochemistry, spectroelectrochemistry, and a series of steady-state and time-resolved spectroscopy. The cyclic voltammetry curve of nanohorn/porphyrin conjugate 6 showed a continuum of faradic and pseudocapacitive behavior, which is associated with multiple-electron transfers to and from the SWNHs. Superimposed on such a pseudocapacitive current, the curve also displays three discrete reduction peaks at -2.26, -2.57, and -2.84 V and an oxidation peak at 1.12 V (all attributed to the porphyrin moiety). Steady-state and time-resolved fluorescence demonstrated a quenching of the fluorescence of the porphyrin in SWNH/H2P conjugates 5 and 6 compared to the reference free base porphyrin. Transient absorption spectra permitted the electron-transfer process between the porphyrins and the carbon nanostructures to be highlighted.
authors.affiliation: INSTM, Unit of Trieste, Dipartimento di Scienze Farmaceutiche, Università di Trieste, Piazzale Europa 1, I-34127 Trieste, Italy.
authors.forename: Carla
authors.initials: C
authors.lastname: Cioffi
authors.forename: Stéphane
authors.initials: S
authors.lastname: Campidelli
authors.forename: Chloé
authors.initials: C
authors.lastname: Sooambar
authors.forename: Massimo
authors.initials: M
authors.lastname: Marcaccio
authors.forename: Gabriele
authors.initials: G
authors.lastname: Marcolongo
authors.forename: Moreno
authors.initials: M
authors.lastname: Meneghetti
authors.forename: Demis
authors.initials: D
authors.lastname: Paolucci
authors.forename: Francesco
authors.initials: F
authors.lastname: Paolucci
authors.forename: Christian
authors.initials: C
authors.lastname: Ehli
authors.forename: G M Aminur
authors.initials: GM
authors.lastname: Rahman
authors.forename: Vito
authors.initials: V
authors.lastname: Sgobba
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Guldi
authors.forename: Maurizio
authors.initials: M
authors.lastname: Prato
mesh_terms: D002244:Carbon / Q000737:chemistry*; D004563:Electrochemistry; D004583:Electrons; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D037742:Nanotubes, Carbon / Q000737:chemistry; D010777:Photochemistry; D013059:Spectrum Analysis, Raman
chemical_list: D037742:Nanotubes, Carbon; D002244:Carbon