[en] C₆₀ forms colloidally stable nanoparticles (nC₆₀) via extended mixing or solvent exchange. Many studies on the environmental impacts of nC₆₀ use aliquots from a large batch of nC₆₀ suspension and either dilute them or subject them to other modifications under the assumption that the properties of the parent suspension remain stable over time and are unaltered by these manipulations. In the present study, nC₆₀ produced via stirring in the presence of sodium citrate (cit/nC₆₀) was characterized with respect to particle size, surface charge, and morphology following dilution. Counter-intuitively, the results show that the colloidal properties of diluted cit/nC₆₀ are not fixed despite constant solution chemistry and are dependent upon the ratios of [C₆₀] to [Na⁺] and [citrate]. In some cases, diluted nC₆₀ had significantly different morphology. This study suggests that any experiment involving modifications of stock nC₆₀ suspensions must take the altered colloidal properties of the diluted nC₆₀ into consideration. -- Highlights: •Size and surface charge of nC₆₀ suspensions do not change substantially after dilution in water. •Dilution by Na₃Cit changes the colloidal properties of cit/nC₆₀. •[C₆₀], [C₆₀]/[Cit],and [C₆₀]/[Na⁺] determine the colloidal properties of the final nC₆₀. •nC₆₀ undergo significant morphological changes after dilution. -- The simple act of dilution has the potential to alter the colloidal properties of nC₆₀. Extreme care should be taken to ensure that dilution does not alter nC₆₀ in undetected ways