Nanosecond laser preparation of C60 aqueous nanocolloids

C60 aqueous nanocolloids were prepared by irradiating a suspended aqueous solution of C60 with intense nanosecond 532 and 355 nm laser pulses. The initial submicron crystal of C60 was fragmented into nanoparticles, resulting in a transparent yellow solution which was followed by UV/vis absorption spectroscopy. The obtained absorption spectra were similar to those for C60 bulk film and its nanoparticles, which have a size on the order of 10 nm, and their formation had thresholds with respect to laser fluence. The nanoparticles were confirmed by their SEM observation and by examining the centrifuging effect on the colloids, while possible photochemical decomposition was excluded by 13C NMR analysis of 1,2-dichlorobenzene-d4 solution, where the possible products can be dissolved in addition to C60 nanoparticles. The present result is the first demonstration of the preparation of pure and very stable C60 aqueous nanocolloids without any additives. The formation mechanism and potential application to biological testing and toxicity are discussed.