On the Action of γ Radiation on Solid C₆₀and C₇₀Fullerenes: A Comparison with Graphite Irradiation

Abstract

Cm and C70 fullerene have been treated in sealed flasks under Ar with y radiation using radiation dosages ranging from 10 to 1000 kGy. The treated samples studied by electronic and FT-IR spectroscopy have not shown any evidence about fullerenes decomposition or radiopolymerization. However, through Raman spectroscopy it was possible to observe that y radiation induces Ce0 dimerization and trimerization. It has additionally been discovered that y-treated CSO (oligomerized) can be easily photopolymerized in the solid state by post-irradiation with laser light at 514 nm while this phenomenon has not been observed by using laser light at 782 nm and considerably higher laser power. Previously to this study, Cea photopolymerization was known to occur only by using ultraviolet light.For comparison also graphite was irradiated with 1000 kGy of y radiation. Irradiated graphite shows considerably changes in its Raman spectrum, showing the formation of glassy carbon domains, perhaps carbon onions The Id bandshift to 1310 cm-' could be interpreted in terms of formation of hexagonal diamond. 577

Hybrid materials with an increased resistance to hard X-rays using fullerenes as radical sponges

“…Upon exposure to X-rays, a change in the Raman band has also been observed with an enlargement of the full wave half-maximum and a shift of the maximum towards lower wavenumbers. In accordance with the literature, these findings indicate a C 60 polymerization to form dimers or trimers (Cataldo, 1993); this effect is mainly induced by the secondary electrons produced by irradiation (Klesper et al, 2005;Zhao et al, 1994). Upon exposure to hard X-rays, in fact, the fullerenes can be excited by secondary electrons allowing addition reactions with other C 60 molecules.…”

Stability of C60and C70fullerenes toward corpuscular and γ radiation

“…Despite fullerenes can form in space and may play a role in astrochemistry either directly or through their derivatives, the so‐called fullerene‐like structures, for instance in molecular hydrogen formation (Cataldo 2003) or even in the synthesis of relatively complex pre‐biotic molecules, their stability in the interstellar space has not yet fully clarified. Certain authors have considered exclusively the stability of C 60 fullerene toward γ radiation (Cataldo 2000b; Sakaguchi et al 2007) even at extremely high doses (Albarran et al 2004; Basiuk et al 2005) neglecting completely to consider their resistance of fullerenes to cosmic rays which are composed by corpuscular radiation. Similarly, other authors have studied the decomposition of C 60 under the action of swift heavy ions (Kalish et al 1993; Takayama 1993; Yogo, Majima & Itoh 2003; Todorović‐Marković et al 2007; Singhal et al 2008) which represent a minor, practically negligible components of cosmic rays (Stanev 2004).…”

Abstracts from the Second European Workshop on Exo/Astrobiology

“…As reviewed from literature data, fullerenes can be formed also from very unusual substrates. 15 C 60 and C 70 fullerenes are easily oligomerized and photopolymerized in the solid state under the action of photons, [16][17][18] but can be re-generated by the action of very intense electromagnetic fields. 14 Higher fullerenes appear to be much more photostable and less prone to photopolymerization than C 60 and C 70 fullerenes.…”

“…In any case, ion bombardment causes the amorphization of fullerenes 19 and similarly also graphite is radiation damaged and slowly converted into disordered graphite and then amorphous carbon. 18,20 Optical properties of carbon blacks 21 : We have also studied the optical properties in the UV-VIS of three carbon blacks having specific surface area from 145 to 7 m 2 /g and produced with furnace or thermal processes. The results have been compared to the optical properties (in the same spectral range) of C 60 fullerene photopolymer, to fullerite, i.e.…”