Synthesis and solvent dependence of the photophysical properties of [60]fullerene-sugar conjugates

A method for the synthesis of optically pure C₆₀ derivatives containing one or two d-galactose or d-glucose units is described. It involves the synthesis of sugar-malonate derivatives followed by a cyclopropanation reaction with C₆₀. The solvent dependence of the photophysical properties of the methano[60]fullerene-sugar derivatives was studied using nanosecond laser flash photolysis coupled with kinetic UV-vis absorption spectroscopy and time-resolved singlet oxygen luminescence measurements. The triplet properties of these fullerenes, including transient absorption spectra, molar absorption coefficients and quantum yield for the photosensitised production of ¹O₂ were determined in toluene, benzonitrile and acetonitrile solutions. The transient absorption spectral profiles are solvent independent although small differences are observed in the transient absorption maximum: 720±5 nm for toluene, 710±5 nm for benzonitrile and 700±5 nm for acetonitrile. Triplet state molar absorption coefficients (ε_T) of C₆₀ derivatives vary from 9456±2090 M⁻¹ cm⁻¹, for compound 10 in toluene, and 15,272±4462 M⁻¹ cm⁻¹, for compound 6 in acetonitrile. Triplet state lifetimes (τ_T) for methano[60]fullerene-sugar derivatives, under our experimental conditions, are similar in toluene or benzonitrile solutions (47.5±1.1 μs≤τ_T≤51.4±2.0 μs) but are lower in acetonitrile solutions (31.8±0.6 μs≤τ_T≤43.0±1.1 μs). Toluene and benzonitrile solutions of C₆₀ derivatives have Φ_Δ close to unity.     

“Sock-Ball” Chromatographic Separation of High Molecular Weight Fullerenes with Sock-Shaped Stationary Phase

A method for “Sock-Bail” chromatographic separation of high molecular weight fullerenes is described. A prepared sock-shaped stationary phase (Sock-SAF-phase) was used for HPLC separation of several polycyclic aromatic hydrocarbons (PAHs) and fullerenes. Fullerenes, as ball-shaped molecules, are much more strongly retained than PAHs on this stationary phase and have the eluted order C₅₀ < C₇₀ < C₇₆ < C₇₈ < C₈₄ in the mobile phase of n-hexane/dichloromethane (100/0 ～ 80/20). In contrast, chromatography on the corresponding unmodified silica phase or SC-3OH-phase (an intermediate phase of Sock-SAF-phase) gave no separation of fullerenes. This fact indicated that the separation of fullerenes on Sock-SAF-phase was related to the selective interaction with the sock moiety.     

Fullerenes for aromatic and non-aromatic N-nitrosamines discrimination

The detection of N-nitrosamines (NAms) in water supplies is an environmental and public health issue because many NAms are classified as probable human carcinogens. Non-aromatic (aliphatic and cyclic) NAms are more toxic than aromatic ones as their maximum admissible concentration is limited in drinking water (20–2000 ng L⁻¹). From that premise, a simple and novel method to discriminate between both fractions of NAms according to their toxicity was proposed. An automatic solid-phase extraction unit containing two sequential sorbent columns was constructed. A sample volume of 25 mL was passed through a C₆₀ fullerene column in which only the aromatic fraction was retained, and the effluent was then passed through a Merck LiChrolut EN column where the non-aromatic fraction was retained. Following elution of the non-aromatic NAms with 150 μL of ethyl acetate–acetonitrile (9:1), 1 μL of the extract was injected into a GC/MS. A comparative study of C₆₀ and C₇₀ fullerenes and nanotubes revealed C₆₀ fullerene to be the best choice to selectively retain the aromatic fraction. The method exhibits a linear range of 15–20,000 ng L⁻¹; limits of detection of 4–15 ng L⁻¹; and an RSD of ∼5%. Recoveries throughout the whole method were between 95% and 102% for six non-aromatic NAms spiked into several types of waters. Our study demonstrates that a simple and fast SPE system (10 min per sample) with a customary GC–MS instrument permits the quantification of these amines in complex matrices with considerable sensitivity and selectivity.     

Synthesis and spectroscopic investigation of trifluoroethoxy-coated phthalocyanine linked with fullerene

Synthesis and spectroscopic investigation of trifluoroethoxy-coated phthalocyanine-fullerene dyad 2 has been described. While nonfluorinated phthalocyanine-fullerene dyad 1 showed an efficient property of intramolecular photoinduced electron transfer, dyad 2, regardless of its covalently linked dyad system, appears not to show any electronic communication between fullerene and phthalocyanine. This observation is presumably due to the strong electron withdrawing nature of 12 trifluoroethoxy groups; fluorine leads phthalocyanine to become an acceptor whose electronic accepting property is equivalent to that of fullerene. This is a unique example that fluorine can terminate electronic communication in the covalently fullerene-phthalocyanine dyad system.     

Conjugated Polymer Based on Polycyclic Aromatics for Bulk Heterojunction Organic Solar Cells: A Case Study of Quadrathienonaphthalene Polymers with 2% Efficiency

Polycyclic aromatics offer great flexibility in tuning the energy levels and bandgaps of resulting conjugated polymers. These features have been exploited in the recent examples of benzo[2,1‐b:3,4‐b']dithiophene ( BDT )‐based polymers for bulk heterojunction (BHJ) photovoltaics (ACS Appl. Mater. Interfaces 2009 , 1, 1613). Taking one step further, a simple oxidative photocyclization is used here to convert the BDT with two pendent thiophene units into an enlarged planar polycyclic aromatic ring— q uadra t hieno n aphthalene ( QTN ). The reduced steric hindrance and more planar structure promotes the intermolecular interaction of QTN‐ based polymers, leading to increased hole mobility in related polymers. As‐synthesized homopolymer ( HMPQTN ) and donor–acceptor polymer ( PQTN ‐ BT ) maintain a low highest occupied molecular orbital (HOMO) energy level, ascribable to the polycyclic aromatic ( QTN ) moiety, which leads to a good open‐circuit voltage in BHJ devices of these polymers blended with PCBM ([6,6]‐phenyl‐C₆₁‐butyric acid methyl ester; HMPQTN : 0.76 V, PQTN ‐ BT : 0.72 V). The donor–acceptor polymer ( PQTN ‐ BT ) has a smaller optical bandgap (1.6 eV) than that of HMPQTN (2.0 eV), which explains its current (5.69 mA cm^?2) being slightly higher than that of HMPQTN (5.02 mA cm^?2). Overall efficiencies over 2% are achieved for BHJ devices fabricated from either polymer with PCBM as the acceptor.     

Fabrication and characterization of fullerene/porphyrin bulk heterojunction solar cells

Fullerene/porphyrin bulk heterojunction solar cells were fabricated and, the electronic and optical properties were investigated. Effects of exciton-diffusion blocking layer of perylene derivative on the solar cells between active layer and metal layer were also investigated. Optimized structures with the exciton-diffusion blocking layer improved conversion efficiencies. Energy levels of the molecules were calculated and discussed. Nanostructures of the solar cells were investigated by X-ray and electron diffraction, which indicated formation of fullerene/porphyrin mixed crystals. Electronic structures of the molecules were investigated by molecular orbital calculation, and energy levels of the solar cells were discussed.     

Classical atomistic simulations of protein adsorption on carbon nanomaterials

Carbon nanomaterials are receiving an increasingly large interest in a variety of fields, including also nanomedicine. In this area, much attention is devoted to investigating and modeling the behavior of these nanomaterials when they interact with biological fluids and with biological macromolecules, in particular proteins and oligopeptides. The interaction with these molecules is in fact crucial to understand and predict the efficacy of nanomaterials as drug carriers or therapeutic agents as well as their potential toxicity when they occupy the active site of a protein or severely affect the secondary and tertiary structure, or even the local dynamics, thus inhibiting their biological function. In this review, therefore, we describe the most recent work carried out in the last few years to model the interaction between carbon nanomaterials, either pristine or functionalized, and proteins or oligopeptides using classical atomistic methods, mainly molecular dynamics simulations. The attention is focused on 0-dimensional fullerenes, mainly C₆₀, on 1-dimensional carbon nanotubes, mostly the single-walled armchair and some chiral ones, and on 2-dimensional graphene and graphyne, the latter containing also sp hybridized atoms in addition to the sp² ones common to the other carbon nanomaterials.     

Can Polymer Solar Cells Open the Path to Sustainable and Efficient Photovoltaic Windows Fabrication?

Sunlight is among the most abundant energy sources available on our planet. Finding adequate solutions to properly and efficiently harvest it is of major importance to potentially solve the global energy crisis. Polymer solar cells have been introduced in the late 20^th century as low‐cost and easily processed alternative to the state‐of‐the‐art silicon photovoltaics. Their power conversion efficiencies, which were initially rather low, are constantly improving and now reach values close to 15 %. As their optical properties can be easily tuned, designing active layer which absorb homogeneously throughout the visible spectrum is relatively simple. These peculiar characteristics enable the possibility to fabricate visibly transparent solar cells with high color rendering indices which can be employed as photovoltaic windows. After reviewing some of the most successful examples of polymer solar cell‐based transparent photovoltaic window fabrication, I will discuss the possibility to produce these devices in a sustainable and/or eco‐friendly manner while maintaining their performances.     

On the estimation of the strength of supramolecular complexes of fullerenes

The accurate estimation of the free energy changes in solution for supramolecular complexes is one of the most important challenges for quantum chemistry in this century. In general, there is a good correlation between the association constants determined experimentally and the gas phase binding energies calculated using the most popular density functional methods. However, when the receptors adopt very different structures in the gas and condensed phase, this approach does not work, leading to unreliable predictions. We discuss this problem in detail using three popular fullerene receptors: Aida's dimeric porphyrins, buckycatchers I, and II. We found that it is possible to obtain a reliable order of affinities using gas phase binding energies when a special attention is put on analyzing the structure adopted by the receptor in the gas and condensed phases.     

Optical properties of soot nanoparticles

In this paper, the dipole-dipole approximation is used to characterize the dynamical electromagnetic properties of two types of carbonaceous nanoparticles modelling the basic constituents of aircraft soot particles. The corresponding polarizability per unit volume is then compared with the one calculated for equivalent defect-free structures and with the one resulting from a continuum model. It is found that the polarizability per unit volume strongly depends on the details of the structure of the nanoparticle, and that this dependence could be used to discriminate between different carbonaceous particles using optical scattering experiments in the visible or near-UV domain.