The high brightness of DIPT-ICF NPs (Fig. ) further inspire us to explore its imaging performance as fluorescent contrast agent. Fig. and Fig. show that the fluorescence signal DIPT-ICF NPs was gradually enhanced with increasing the molecular concentration and afforded stable fluorescent signals in different aqueous media, suggesting the superior stability of these fluorescent nano contrast agent in the body fluid environment. Since the pH value of interstitial fluid varies with organ metabolism, the PL intensity of DIPT-ICF NPs under different pH was also investigated, which was almost unchanged when varying the pH from 1 to 12 in phosphate buffered solution (PBS), demonstrating the excellent stability of DIPT-ICF NPs upon pH variation (Fig. and). Photostability of the imaging contrast agent is also significant for biological process monitoring or guiding the surgery since poor photostability suffers the photobleaching effect when implementing the long-time imaging. Upon continuous laser irradiation, DIPT-ICF NPs revealed superior photostability compared with ICG in an aqueous environment, which is beneficial for application scenario of continuous imaging events, long-circulating fluorescence angiography and so on (Fig. ). Noteworthy, DIPT-ICF NPs don't not exhibit a significant photothermal effect at low energy density (~100 mW/cm 2 ), which would not cause thermal damage to living tissues during the imaging process (Fig. ).