Nanodiamond, which has a lattice defect, the energy band gap and good biocompatibility, is an ideal inorganic fluorescent imaging material for cells. However, the nanodiamond aggregation is not exactly suitable for cells' endocytosis if the size is too small or too big. Therefore, it has a profound meaning to modify the surface of nanodiamond and control the dispersion of nanodiamond aggregate. In this study, the surface of the detonated nanodiamond is modified into carboxylated nanodiamond by using the method of mixed acid oxidation. Then, the nanodiamond aggregates' dispersion in water is regulated by adjusting the pH, which is first discussed as a factor influencing the size of nanodiamond aggregation. This process further induces the corresponding change of the electrostatic force between nanoparticles, improves its applicability in the field of living cell fluorescence imaging. 

Journal of Nanoscience and Nanotechnology, Volume 16, Number 3, March 2016, pp. 2319-2324(6)