Fig. 7. (a) The in vivo fluorescence images of CQDs that are injected into a nude mouse; the excitation wavelengths are indicated above each image. The fluorescence signal and tissue autofluorescence can be seen in red and green emissions, respectively. (b) Signal-to-background separation of the image taken under 704 nm excitation, reprinted with permission from ref. 148, copyright 2011 John Wiley and Sons.