Fig. 2. Characterization of 1-NP in vitro.

a Comparison of the UV–vis-NIR absorption (abs.) spectra of 1-NP, IR1048, 1-Br-Et, and NIR775. b Dynamic light scattering (DLS), and c Transmission electron microscopy (TEM) image of 1-NP. The experiments in (c) were repeated independently three times with similar results. d Normalized UV–vis-NIR absorption and e normalized fluorescence (FL) spectra of 1-NP (56/1.65/20 μM 1-Br-Et/NIR775/IR1048) before and after incubation with •OH (200 µM Fe²⁺ + 1 mM H₂O₂) at r.t. for 3 min. Inset: FL images and ratiometric FL₇₈₀/FL₁₁₁₃ images of 1-NP before (-) and after (+) incubation with •OH. FL spectra of NIR775 within 1-NP was acquired by synchronous FL scanning (λ_ex = 700–900 nm, offset = 10 nm). FL spectra of IR1048 within 1-NP was acquired upon excitation at 808 nm, and emission with bandpass between 900-1500 nm. f Normalized photoacoustic (PA) intensity and PA images along with ratiometric PA₇₅₅/PA₉₀₅ images (inset) of 1-NP (56/1.65/20 μM 1-Br-Et/NIR775/IR1048) before and after incubation with •OH (200 µM Fe²⁺ + 1 mM H₂O₂) at r.t. for 3 min. The PA images were acquired at 755 and 905 nm, respectively. g Normalized FL₇₈₀/FL₁₁₁₃ and PA₇₅₅ /PA₉₀₅ of 1-NP upon incubation without and with •OH. h Normalized time-dependent increment of UV–vis absorption (560 nm) of 1-NP (8/0.24/2.86 μM 1-Br-Et/NIR775/IR1048) following incubation with varying concentrations of •OH (0, 50, 80, 100, 200 μM Fe²⁺ + 1 mM H₂O₂) at r.t.. i Plot of the pseudo-first-order rate (k_obs) versus •OH concentration (50–200 µM) affords the second-order reaction rate (k₂) between 1-NP and •OH at r.t. The k_obs was determined by fitting the absorption intensity with single exponential function of $y=y_0+A\times \exp \left(R_0\times t\right)$, where $k_{\mathrm{obs}}=-R_0$. The k₂ value was obtained from the slope of the linear plot between k_obs and •OH concentration (R² = 0.98). Data are presented as mean ± s.d. (n = 3 independent samples). Source data are provided as a Source Data file.