Separate solutions of each dye (1 µM) in PBS buffer at pH 7.4 were exposed to air and irradiated for 40 minutes using a 150 W Xenon lamp equipped with a 620 nm long pass filter. The absorption decay curves in Figure indicate a substantially slower photobleaching rate for ICB compared to ICG. Together, these results show that ICB is substantially more stable than ICG, which matches the known increased stability of pentamethine cyanine dyes compared to heptamethine cyanine dyes. A photothermal heating experiment, using a laser to illuminate ICB in water, showed good stability over repeated heating and cooling cycles (Figure ) suggesting high potential for applications based on photothermal heating. But there was no sample heating using the lower power light associated with in vivo imaging.