Synthesis, characterization, and photoinduced electron transfer in functionalized single wall carbon nanohorns.
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.
Cioffi
Carla
C
INSTM, Unit of Trieste, Dipartimento di Scienze Farmaceutiche, Università di Trieste, Piazzale Europa 1, I-34127 Trieste, Italy.
Campidelli
Stéphane
S
Sooambar
Chloé
C
Marcaccio
Massimo
M
Marcolongo
Gabriele
G
Meneghetti
Moreno
M
Paolucci
Demis
D
Paolucci
Francesco
F
Ehli
Christian
C
Rahman
G M Aminur
GM
Sgobba
Vito
V
Guldi
Dirk M
DM
Prato
Maurizio
M
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
D037742:Nanotubes, Carbon; D002244:Carbon