Fullerene C60 pristine powder exhibits only one sharp and uniform weight loss between 500°C and 650°C (Fig. 20.2(b)). The derivatised C60 powder begins to lose the weight after 300°C (Fig. 20.2(a)). First the weight loss is relatively slow up to almost 500°C, then becomes sharper and straighter, and the material decomposes completely under further heating up to 650°C.
In the infrared absorption spectra of crystalline C60 powder reacted with 1,8-diaminooctane, we observed remarkable changes as compared to the spectrum of pristine C60 (Fig. 20.3(a)). The latter exhibits four characteristic bands at 526, 576, 1181 and 1427 cm-1 (Dresselhaus et al., 1993). The derivatisation product has a richer chemical structure, and in addition to the above four bands, it shows several intense broad peaks (Fig. 20.3(b)) near 715, 1096 (Vc-c), 1643 (Snh), 2855 and 2922 cm-1 (VCH). The region of 500-800 cm-1 is a 'fingerprint' region for fullerene derivatisation, and new IR features are observed when the C60 skeleton is partially broken (Iwasa et al. 1994), for example in the formation of cross-linked fullerene molecules as reported by Sun and Reed (2000). In our case one can also see that instead of only one band at 1425 cm-1 (C=C skeleton vibration), there is another sharp peak at 1383 cm-1. Peak position for this mode is known to be very sensitive to such modifications of C60 molecule as polymerisation (Sun and Reed, 2000).
100 Cp 80 60
0 200 400 600 800 1000
Fig. 20.2. TGA curves for C60 derivatised with 1,8-diaminooctane (a) in comparison with pristine C60 powder (b)
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