Preparation and Characterization of Inorganic Fluorides—Fullerenes Compounds

Reaction of metallic fluorides: WF₆ TaF₅, NbF₅ and TiF₄ with C₆₀/C₇₀ extract was performed at appropriate temperatures. M0F₅ and BF₃ fluorides do not react. Chemical formulas based on mass uptake show MF_n/C₆₀ ratios up to 2.00. Compounds were analysed by means of X-ray diffraction, FT-IR and NMR spectroscopies. The presence of neutral fluorides and associated anionic species is put forward and it is shown that MF_n compounds do not act as fluorination agents. Electrical conductivity measurements are also presented.     

Oxidized Fullerene Derivatives Containing Hydroxyl, Nitro and Fluorine Groups

Oxidation of fullerene was performed with fuming nitric acid and a soluble orange compound was synthesized and identified as polyhydroxy-polynitro fullerene. The formation of fullerene derivatives containing oxygen and fluorine were attempted by different methods using F₂, HF aqueous solution and fuming nitric acid. Resulting compounds were generally characterized by X-ray diffraction and IR and NMR spectroscopy.     

Electrochemical insertion of lithium ions into disordered carbons derived from reduced graphite fluoride

Both covalent (obtained by direct fluorination at high temperature) and semi-ionic carbon fluorides (synthesized at room temperature) were reduced in order to obtain disordered carbons containing very small content of fluorine and different physical properties according to the reduction treatment (chemical, thermal or electrochemical). After a physical characterization (X-ray diffraction, electron spin resonance and FT-IR spectroscopies), the electrochemical behaviours of the pristine carbon fluorides and of the treated samples were investigated during the insertion of lithium using liquid carbonate-based electrolytes (LiClO₄-EC/PC, 50:50%, v/v). Both galvanostatic and voltammetric modes were performed and revealed that the voltage profiles and the capacities differed according to the starting material and the reduction treatment. Semi-ionic carbon fluoride treated in F₂ atmosphere for 2 h at 150 °C and then chemically reduced in KOH exhibits high reversible capacities (the reversible capacity is 530 mAh g⁻¹ in the second cycle); in this case, the voltage profiles show a large flat portion at potentials lower than 0.3 V which is attributed to the insertion/deinsertion of lithium ions between the small graphene sheets and/or the absorption of pseudo metallic lithium into the microporosity of the sample. Nevertheless, a part of the lithium ions are removed at potentials higher than 0.5 V versus Li⁺/Li limiting the useful capacity.     

Friction Properties of Fluorinated Carbon Nanodiscs and Nanocones

The tribologic properties of carbon nanodiscs and nanocones and their fluorinated derivatives are investigated and correlated to their structure and chemical composition (atomic fluorine/carbon ratio). Two families of products are studied obtained by fluorination of ill ordered and highly graphitized carbon nanodiscs and nanocones. The studies clearly point out that friction properties of the nanoparticles are strongly dependent on the structure of the initial carbonaceous compounds. Better tribologic behaviour is obtained when the initial nanoparticles structure is highly ordered (graphitized particles). In that case, an optimum of fluorination rate is put in evidence.     

Should Doppler echography in the diagnosis of the extra-cardiac sites of atherosclerosis be routine in patients with coronary disease? Apropos of 248 cases

Doppler ultrasound investigation of cervical and aorto-iliac arteries, performed in 248 patients investigated by coronary angiography (including 80% with coronary heart disease: 23% single-vessel, 23% two-vessel and 34% three-vessel disease) confirmed the frequency of dissemination of the atheromatous process (in the cervical vessels: non-stenotic atheroma: 45%, significant single- or multi-vessel stenoses: 16%, in the aorto-iliac vessels: non-stenotic atheroma: 32.8%, significant stenoses: 17.2%), which has been known for a long time. The unreliability of clinical examination, the reliability, safety and low cost of ultrasound, the discovery of a considerable number of critical, potentially dangerous arterial lesions, some of which may require a surgical procedure or angioplasty (3.4%), the value of assessing, either before coronary angiography or before cardiac surgery, certain specific arterial territories such as the aortic bifurcation and subclavian vessels, justify systematic use of this examination in coronary patients, particularly before coronary angiography and always before coronary surgery.     

Study of chemically (AsF5) and electrochemically doped aluminium polyfluorophthalocyanine, (PcAlF)n

Chemical AsF₅ and electrochemical AsF₆^? doping of aluminium polyfluorophthalocyanine, (AlPcF)_n, has been studied. Thermogravimetric analysis, infrared spectroscopy, X-ray diffraction and electrical conductivity measurements were used to characterize the doped materials. Particular attention has been devoted to the study of the most heavily doped samples obtained in the first case (between 4 and 5 AsF₅ molecules per phthalocyanine ring). A qualitative structural model is proposed to explain the low electrical conductivity of these samples. Results are compared with those for iodine-doped (AlPcF)_n and (GaPcF)_n.Cyclic voltammetry performed on polymer films revealed the existence of two oxidation peaks. While it is very likely that the second peak is accompanied by a chemical reaction taking place at the polymer electrode, it is possible to obtain a lightly AsF₆^?-doped sample for applied potentials lower than 0.6 V (versus Ag/Ag⁺). Very similar results are obtained with BF₄^? and ClO₄^? doping anions.     

Oxidized Fullerene Derivatives Containing Hydroxyl,Nitro and Fluorine Groups

Abstract

Oxidation of fullerene was performed with fuming nitric acid and a soluble orange compound was synthesized and identified as polyhydroxy-polynitro fullerene. The formation of fullerene derivatives containing oxygen and fluorine were attempted by different methods using F₂, HF aqueous solution and fuming nitric acid. Resulting compounds were generally characterized by X-ray diffraction and IR and NMR spectroscopy.     

The synthesis of multilayer graphene materials by the fluorination of carbon nanodiscs/nanocones

Multilayer carbonaceous nanomaterial has been synthesized using a two-step process: carbon nanodiscs/nanocones were fluorinated using either the direct reaction with pure F₂ gas or the thermal decomposition of solid fluorinating agent (TbF₄). Then the fluorinated parts were removed by treatment at 600 °C in air. When the fluorine atoms are homogenously dispersed, using fluorination by TbF₄, thinning due to thermal defluorination results in multilayer materials with 7–10 nm of thickness and 400–500 nm of width. Such resulting materials and the fluorinated precursors have been characterized by solid state NMR, TGA, XRD, SEM, TEM, AFM and Raman spectroscopy.