Figure 1.

Comparison of PbS/CdS as a novel blood contrast dye with improved clarity and penetration of depth, compared to SWNTs. A. Schematic diagram showing PbS quantum dot core (red), CdS outer coating (orange), and PMA (blue) with PEG chains on the surface. B. Emission spectrum of PbS/CdS dye showing 1500–1700 nm. C. Fluorescence of PbS/CdS within an eppendorf at 1500–1700 nm emission wavelength. D. Phantom studies comparing the penetration depth of SWNTs (NIR-II) and PbS/CdS (NIR-IIb) at depths of 0, 2, and 6mm in Intralipid® excited at 808 nm. The PbS/CdS sample shows less feature spread than that of the SWNT sample. Scale bar: 5 mm. E. Full width half max (FWHM) measurements depict the feature width of SWNT and PbS/CdS capillary images at varying depths in Intralipid®, showing increased loss of feature integrity for the NIR-II-emitting SWNTs, compared to the NIR-IIb-emitting PbS/CdS.