Enhancement of water solubility of fullerene by cogrinding with mixture of cycloamyloses, novel cyclic α-1,4-glucans, via solid-solid mechanochemical reaction

Improvement of solubility for fullerene (C-60) was studied by cogrinding with cycloamyloses using a ball mill in the solid state. Cycloamylose is a novel cyclic alpha-1,4-glucan produced from synthetic amylose by enzymatic reaction. Although sample solutions showed a pale yellow for the initial period of cogrinding with cycloamyloses and C-60, the color varied to brown after 48 h. Subsequently, the solubility of C-60 was improved markedly to 560 (mug/ml) at 96 h. From powder X-ray diffraction analysis, the peak intensity of crystalline C-60 decreased as the cogrinding time was extended. The UV-VIS absorption spectrum of C-60 shows absorption bands at 262 and 340 nm in water with cycloamyloses, and 258 and 328 nm in n-hexane. These results suggested that C-60 molecules were dispersed into cycloamyloses micellar system and the red-shift of the UV-VIS spectra was due to an intermolecular interaction between C-60 and cycloamyloses.