Fig. 1.

Comparison between organic dyes (rhodamine red/DsRed2) and inorganic nanocrystal (different size of QDs). a Absorption (Abs) and emission (Em) of rhodamine red. b Absorption and emission of six different QD dispersions. c Photo demonstrating the size-tunable fluorescence properties and spectral range of the ten QD dispersions. d Nuclear antigens were labeled with QD 630–streptavidin (red), and microtubules were labeled with AlexaFluor 488 (green) simultaneously in a 3T3 cell. Bottom row Microtubules were labeled with QD 630–streptavidin (red) and nuclear antigens were stained green with Alexa 488. Continuous exposure times in seconds are indicated. Note the QD resistance to photo-bleaching under continuous illumination (Medintz et al. 2005)