Improved spectrophotometric analysis of fullerenes C60 and C70 in high-solubility organic solvents

Synthesis and Application of New Selanylfullerene Derivatives as Photosensitizers for Photodynamic Therapy

This study aims to describe the synthesis of a new class of selanylfullerene derivatives in a convergent strategy route, affording the desired products in a few steps and in good yields. C60 compounds were evaluated as photosensitizers to be used in photodynamic therapy (PDT) via the generation of singlet oxygen (1O2), using the chemical trapping method. The photooxidation of the chemical probe1,3-diphenylisobenzofuran (DPBF) sensitized by selanylfullerenes followed a first-order kinetic and the values of singlet oxygen quantum yields (ΦΔ) are appropriate for its use in PDT. The electronic absorption spectra, and the intersystem crossing tax rates for the most prominent synthesized compounds were calculated using the density functional theory and the Marcus electron transfer theory, with the theoretical results confirming the experimental findings.

Effect of Metallic and Non-Metallic Additives on the Synthesis of Fullerenes in Thermal Plasma

The effect of metallic (Fe, Cu, Co, Ni, Ti) and non-metallic additives (Si, B) on the formation of fullerenes from graphite powders was studied in radiofrequency (RF) thermal plasma. The main component of the synthesized fullerene mixtures was C60, but higher fullerenes (C70, C82, and C84) could be detected as well. Fe and Cu additives increased the fullerene content in the soot. In contrast, the fullerene formation decreased in the presence of Ti, Si, and B as compared to the synthesis without additives. However, Ti and B addition enhanced the formation of higher fullerenes. We provide experimental evidence that decreasing the reactor pressure results in a lower yield of fullerene production, in accordance with thermodynamic calculations and numerical simulations published earlier. In the presence of titanium, a significant quantity of TiC was also formed as a by-product. The fullerene mixture synthesized with boron additives showed higher stability during storage in ambient conditions as compared to other samples.

Methanofullerene Synthesis via Photogenerated Fullerene Radical Anion Intermediates

This work describes the synthesis of PCBM ([6,6]-phenyl-C₆₁-butyric acid methyl ester) derivatives and other methanofullerene derivatives via generation of fullerene radical anions under photoirradiation and controlled by photoswitching, without preparation, a strong reducing agent, or precise control of the reaction conditions.

The Effects of Temperature and Humidity on the Microstructure of Sulfonated Syndiotactic-polystyrene Ionic Membranes

Polymeric membranes based on the semi-crystalline syndiotactic-polystyrene (sPS) become hydrophilic, and therefore conductive, following the functionalization of the amorphous phase by the solid-state sulfonation procedure. Because the crystallinity of the material, and thus the mechanical strength of the membranes, is maintained and the resistance to oxidation decomposition can be improved by doping the membranes with fullerenes, the sPS becomes attractive for proton-exchange membranes fuel cells (PEMFC) and energy storage applications. In the current work we report the micro-structural characterization by small-angle neutron scattering (SANS) method of sulfonated sPS films and sPS-fullerene composite membranes at different temperatures between 20 °C and 80 °C, under the relative humidity (RH) level from 10% to 70%. Complementary characterization of membranes was carried out by FTIR, UV-Vis spectroscopy and prompt-γ neutron activation analysis in terms of composition, following the specific preparation and functionalization procedure, and by XRD with respect to crystallinity. The hydrated ionic clusters are formed in the hydrated membrane and shrink slightly with the increasing temperature, which leads to a slight desorption of water at high temperatures. However, it seems that the conductive properties of the membranes do not deteriorate with the increasing temperature and that all membranes equilibrated in liquid water show an increased conductivity at 80 °C compared to the room temperature. The presence of fullerenes in the composite membrane induces a tremendous increase in the conductivity at high temperatures compared to fullerenes-free membranes. Apparently, the observed effects may be related to the formation of additional hydrated pathways in the composite membrane in conjunction with changes in the dynamics of water and polymer.

The Study of the Optical Properties of C60 Fullerene in Different Organic Solvents

C60 fullerene exhibits unique optical properties that have high potential for wide photo-optical applications. To analyze the optical properties of C60, its excitation and emission properties were studied using UV-Vis absorption and photoluminescence (PL) spectroscopy, which were performed in various, non-polar organic solvents such as toluene, xylene, and trichloroethylene (TCE). The C60 solutions in toluene, xylene, and TCE displayed similar excitation bands at 625, 591, 570, 535, and 404 nm corresponding to Ag → T1u and Ag → T1g transitions. However, these bands differed from the solid C60 observed by UV-Vis diffuse reflectance spectroscopy. The two emission band energies of C 60 solution in toluene and xylene were nearly the same (1.78 and 1.69 eV), whereas the C60 solution in TCE was shifted to 1.72 and 1.65 eV. Because the polarity of TCE is higher than that of toluene and xylene, the PL spectrum of the C 60 solution in TCE was red-shifted. The PL spectroscopy had a better capability than UV-Vis absorbance spectroscopy to distinguish the different interactions between C60 and the organic solvents due to their different solvent polarities.

[60]Fullerene for Medicinal Purposes, A Purity Criterion towards Regulatory Considerations

Since the early nineties countless publications have reported promising medicinal applications for [60]fullerene (C60) related to its unparalleled affinity towards free radicals. Yet, until now no officially approved C60-based drug has reached the market, notably because of the alleged dangers of C60. Nevertheless, since the publication of the effects of C60 on the lifespan of rodents, a myriad of companies started selling C60 worldwide for human consumption without any approved clinical trial. Nowadays, several independent teams have confirmed the safety of pure C60 while demonstrating that previously observed toxicity was due to impurities present in the used samples. However, a purity criterion for C60 samples is still lacking and there are no regulatory recommendations on this subject. In order to avoid a public health issue and for regulatory considerations, a quality-testing strategy is urgently needed. Here we have evaluated several analytical tools to verify the purity of commercially available C60 samples. Our data clearly show that differential scanning calorimetry is the best candidate to establish a purity criterion based on the sc-fcc transition of a C60 sample (Tonset ≥ 258 K, ∆sc-fccH ≥ 8 J g-1).

Sedimentation of C60 and C70: Testing the Limits of Stokes' Law

Virtually all dynamic methods for determining particle size on the nanoscale use the Stokes-Einstein-Sutherland (SES) equation to convert the diffusion coefficient into a hydrodynamic radius. The validity of this equation on the nanoscale has not been rigorously validated by experiment. Here we measure the sedimentation rates and diffusion coefficients of C₆₀ and C₇₀ in toluene using analytical ultracentrifugation and compare the results to the SES equation. We find that the SES equation for the drag force (nonslip boundary condition) works down to 1 nm length scales.