An investigation on dispersion, stability, and agglomeration of water-soluble fullerenol in water was studied via UV-Vis spectroscopy. The results showed that the dispersion quality and stability of water-soluble fullerenol commenced decreasing after 150 h (more than six days) of solution preparation time. Furthermore, increasing the fullerenol concentration in water (C-fullerenol) showed promotion of the agglomeration in lower residence time. Considering the results of DLS and HRTEM micrographs, an average particle size of the fullerenol in the solution was measured to be similar to 150 nm after a residence of 2 months highlighting its high agglomeration tendency even at low concentration. (C) 2016 Elsevier B.V. All rights reserved.