_Lower_ temperature gets better solubility. They tested at 10 up to 70 dgrees Celsius. at 10 degrees, solubility was highest implying exothermic dissolution.
Solutions were created using 5ml of oil and 14mg of C60 each by stirring for several days followed by ultra-centrifuge.
Regarding commercial oils, at 20 degrees Celsius, the results are as follows, where olive oil is "extra virgin" type:
Carapelli Olive oil = ~3ug/ml
Borgess Olive oil = ~6ug/ml
Olatalia Olive oil = ~4ug/ml
Venus Sunflower oil = ~7ug/ml
Floriol Sunflower oil = ~4ug/ml
Eden Sunflower oil = ~5.6ug/ml
They also hint that both purple and orange tints (435nm and 600nm band) are clearly formed early on and purple is more intense in oils with higher unsaturation and thus high iodine number, such as linseed oil. They proposed that C60 has better solubility in lower-unsaturation oils, but the data doesn't seem conclusive, with a small dataset.
Update: they also hinted that the purple color is associated with addition of fatty chain to the C60 cage. So the C60 is not only dissolved, but also reacts resulting in some amount of C60 being grafted to the fatty chains.
Edited by testerer, 02 May 2012 - 01:28 AM.