1,721,066 research outputs found
A topologically new ruthenium porphyrin-fullerene donor acceptor ensemble
No full textA novel ruthenium porphyrin complex bearing an axially coordinated fullerene ligand (RuP-C60), that is, a fulleropyrrolidine that bears a pyridine moiety, was developed as an artificial reaction center mimic. Generally, the new donor acceptor dyad gives rise to rapid intramolecular deactivation of the ruthenium porphyrin triplet excited state, which evolves from instantaneous intersystem crossing. The product of the ruthenium porphyrin excited-state deactivation depends on the solvent polarity. While in non-polar solvents a transduction of triplet excited energy predominates, in medium and strongly polar media, charge-separation leads to the formation of RuP*+ C60*-
Facile and quick preparation of carbon nanohorn-based counter electrodes for efficient dye-sensitized solar cells
No full textFor the first time, Pt-free counter electrodes based on carbon nanohorns for highly efficient dye-sensitized solar cells were assembled by a facile and fast drop cast technique. These novel electrodes feature an effective catalytic behavior towards the reduction of I3− and, as such, afford even higher short-circuit current densities compared to Pt-based references. In a final device, solar cells with 7.7% efficiency were achieved
Electronic communication through pi-conjugated wires in covalently linked porphyrin/C60 ensembles
No full textPorphyrin Antennas on Carbon Nanodots: Excited State Energy and Electron Transduction
No full textWe report the synthesis and electron donor–acceptor features of a novel nanohybrid, in which the light-harvesting and electron-donating properties of a meso-tetraarylporphyrin (TArP) are combined with the electron-accepting features of nitrogen-doped carbon nanodots (NCNDs). In particular, in an ultrafast process (>1012 s−1), visible-light excitation transforms the strongly quenched porphyrin singlet excited states into short-lived (225 ps) charge-separated states. On the other hand, ultraviolet light excitation triggers a non-resolvable transduction of singlet excited state energy from the NCNDs to the porphyrins, followed by the same charge separation observed upon visible light excitation
Ruthenium(II) Tris-Bipyridine Complexes With A [60]Fullerene Ligand: Synthesis And Properties
No full textThe cycloaddition of azomethine ylides and cyclopropanation reactions have been used to covalently link a 2,2’-bipyridine (bpy) derivative to [60]fullerene through a suitable spacer. Coordination of the bucky ligands to Ru(bpy)2Cl2 produces molecular dyads in which the electron-acceptor characteristics of the fullerene spheroid are coupled with the well-known electron-donating properties of the ruthenium tris-bpy complex upon photoexcitation. Combining these donor-acceptor chromophores in the same molecule gives rise to interesting excited state behavior that can be conveniently studied through cyclic voltammetric, flash-photolytic and pulse-radiolytic techniques
Photoinduced Electron Transfer in a Tris(2,2'-bipyridine)-C60-Ruthenium(II) Dyad: Evidence of Charge Recombination to a Fullerene Excited State
No full textProbing molecular wire: synthesis of donor-acceptor ensembles exhibiting long range electron transfer
No full textA series of donor–acceptor arrays (C60–oligo-PPV–exTTF; 16–20) incorporating p-conjugated oligo(phenylenevinylene) wires (oligo-PPV) of different length between p-extended tetrathiafulvalene (exTTF) as electron donor and C60 as electron acceptor has been prepared by multistep convergent synthetic approaches. The electronic interactions between the three electroactive species present in 16–20 were investigated by UV-visible spectroscopy and cyclic voltammetry (CV). Our studies clearly show that, although the C60 units are connected to the exTTF donors through a p-conjugated oligo- PPV framework, no significant electronic interactions are observed in the ground state. Interestingly, photoinduced electron-transfer processes over distances of up to 50 6 afford highly stabilized radical ion pairs. The measured lifetimes for the photogenerated charge-separated states are in the range of hundreds of nanoseconds (~500 ns) in benzonitrile, regardless of the oligomer length (i.e., from the monomer to the pentamer). A different lifetime (4.35 ms) is observed for the heptamer-containing array. This difference in lifetime has been accounted for by the loss of planarity of the oPPV moiety that increases with the wire length, as established by semi-empirical (PM3) theoretical calculations carried out with 19 and 20. The charge recombination dynamics reveal a very low attenuation factor (b=0.01_0.005 6_1).
This b value, as well as the strong electron coupling (V~5.5 cm_1) between the donor and the acceptor units, clearly reveals a nanowire behavior for the p-conjugated oligomer, which paves the way for applications in nanotechnology
Decorating Carbon Nanotubes with Metal or Semiconductor Nanoparticles
No full textDue to their large chemically active surface and stability at high temperatures carbon nanotubes (CNTs) have been used as a support material for the dispersion and stabilization of metal and semiconductor nanoparticles (NPs). These hybrid materials have found several applications in catalysis, nanoelectronics, optics, nanobiotechnology, etc. Several ways have been described in the literature to immobilize NPs on CNTs and they can be divided into two main pathways: (a) the formation (and stabilization) of metal NPs directly on the carbon nanotube surface, and (b) the connection of chemically modified NPs to carbon nanotubes or to modified CNTs. A plethora of methods for the synthesis of different NPs have been very recently developed. This know-how is now available for the generation of a large variety of new hybrid products in combination with CNTs. A selection of representative examples of the synthesis, properties and applications of NP–CNTs is here reported and discussed
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