Fig. 1.

SWIR emission of the NIR dye ICG. (A) The full emission spectrum of ICG, measured on an NIR- and SWIR-sensitive InGaAs detector (red line), mirrors the absorption spectrum (black line) as predicted by the Franck–Condon principle. (B) The emission intensity of a 0.027 mg/mL aqueous ICG solution, detected in 20-nm spectral bands on an InGaAs camera and normalized by integration time, shows that emission is detectable up to at least 1,575 nm (Inset shows the vial). A lower intensity is observed between 1,400 and 1,500 nm due to the absorption band of water at those wavelengths.