Synthesis and optical properties of emission-tunable PbS/CdS core–shell quantum dots for in vivo fluorescence imaging in the second near-infrared window

Near-infrared (NIR) fluorescence imaging at wavelengths from 1000 to 1500 nm (2nd-NIR window) is a promising modality for in vivo fluorescence imaging because of the deeper tissue penetration with lower tissue scattering of the 2nd-NIR light. For such in vivo fluorescence imaging, highly fluorescent probes in the 2nd-NIR wavelength region are needed. Although single-walled carbon nanotubes and Ag 2 S quantum dots (QDs) have recently appeared as 2nd-NIR fluorescent probes, their fluorescence brightness is relatively low (quantum yields