Fig. 1

Characterization of AG-QDs. a, b: TEM imaging and size distribution of AG-QDs in deionized (DI) water and culture medium, respectively. c, d: AFM topography and height of AG-QDs in DI water and culture medium, respectively. e Zeta potentials of AG-QDs in DI water and culture medium. In panel (e), S1 represents AG-QDs (50 μg/mL) in DI water, and S2-S5 represent AG-QDs at 0, 50, 100, and 200 μg/mL in FBS-containing culture medium, respectively. (f) Fluorescence spectra of AG-QDs in DI water and culture medium. In panels (a) and (b), the size distribution of AG-QDs (as shown by the inserted figures) was obtained by calculating 50 randomly-selected points during TEM imaging. In panels (c) and (d), the inserted figures were the height profiles of AG-QDs as marked on the AFM images. In panel (e), the values are given as mean ± SD (standard deviation). Significant difference is marked with different letters (p < 0.05, LSD, n = 6)