Fig. 1: Photophysical properties of Y6CT-NPs.

a Schematic illustration of the formulation of Y6CT-NPs. WL white-light. b Dynamic light scattering and TEM image of Y6CT-NPs. Repeated for three times in independent experiments. Molar extinction coefficient (c) and fluorescence spectra (d) of Y6CT in nanoparticle and solution state (E_x = Laparoscopic-light, 643 nm long-pass filter). e The linear fitting of the integrated PL intensity vs. the absorbance values of Y6CT-NPs in deionized water, FY6-NPs in deionized water and IR26 in DCE (E_x = 808 nm laser). f The NIR-II fluorescence brightness (ɛ × QY) of different NPs. g The mean fluorescence intensity of Y6CT-NPs in water, FY6-NPs in water, ICG in water, IR26 in DCE, and IR1048 in DCE with the same concentration (10 μM). Data were presented as mean ± SD derived from n = 3 independent samples per group. The inset shows their NIR-II fluorescent images under white-light illumination (16.5 mW cm⁻²) and corresponding photographs under daylight. h Photostability of ICG and Y6CT-NPs (10 μM) in water upon continuous laparoscopic-light (50 mW cm⁻²) illumination for 40 min. Data were presented as mean ± SD derived from n = 3 independent samples per group. p value indicates the significant difference. p = 0.0002, ***p < 0.001, and statistical significance was assessed via an unpaired two-sided t-test method. I represents the PL intensity of the samples at different time, while I₀ indicates the initial intensity at 0 min. The inset shows their corresponding photographs under daylight before and after laparoscopic-light activation.