(a) Fluorescence images of HT-1080 cells stained with QD@BRn conjugates (n = 9, 7, 5, 4, 3, 2, 1, 0 for A to H, respectively) and QD (I); (b) Fluorescence intensity of COS-7 cells in 96 microtiter plates incubated with QD@BRn (n as indicated for each column); (c) Fluorescence intensity of COS-7 cells incubated with QDs conjugated with a mixture of BR4 and BR at indicated ratios.