1. Illustration of activation mechanism of fluorescence signal when F@H presenting in the HClO

2. Characterization of the prepared HMPB and F@H(a) Typical TEM image, (b) XRD pattern, and (c) pore-size distribution curve of HMPB with inset showing N₂ adsorption-desorption isotherm; (d) UV-Vis spectra of FITC, HMPB and F@H; (e) Fluorescence spectra of free FITC and F@H with inset showing corresponding fluorescence intensity ratio at 520 nm; (f) Fluorescence life of FITC and F@H

3. In vitro detection of HClO and mechanism(a, b) Fluorescence (FL) spectra (a) and the corresponding calibration curve (b) of F@H (50 μg/mL) with the addition of NaClO (0-50 μmol/L) in Tris-HCl (10 mmol/L, pH 5.5). λ_ex=488 nm, λ_em=520 nm; (c) Absorbance of F@H varied with time before and after addition of NaClO; (d) XPS profiles of F@H without/with addition of NaClO

4. Fluorescence of F@H in the presence of other ROS(a) Fluorescence spectra (inset of (a)) and the corresponding fluorescence (FL) intensity (a) of F@H (50 μg/mL) with the addition of different interfering substances (500 μmol/L, 1-blank, 2-TBHP, 3-ROO, 4-NO, 5-H₂O₂, 6- · ·OH, 7-ONOO^-, 8-ClO^-) in Tris-HCl (10 mmol/L, pH 5.5) λ_ex=488 nm, λ_em=520 nm; (b) Absorbance change of F@H with addition of different interfering substances (500 μmol/L)Colorful figures are available on website

5. Detecting HClO in living cancer cells(a-d) Confocal fluorescence and (e-h) bright field images for detecting exogenous or endogenous HClO in 4T1 cellsBlank: without any treatments; Control: 50 μg/mL of F@H and 0 μmol/L NaClO; NaClO: 50 μg/mL of F@H and 100 μmol/L NaClO; Elesclomol: 50 μg/mL of F@H and 50 μmol/L elesclomol. λ_ex=488 nm, λ_em=520 nm; (i) Statistical analyses of the confocal images

S1. Dynamic light scattering (DLS) result of HMPB with insets showing digital photographs of HMPB suspension standing still for 0 and 12 h.

S2. Standard curves (a) and the corresponding calibration curve (b) of FITC, UV-Vis spectrum of F@H supernatent (c) ppm: μg/mL

S3. Time-dependent fluorescence intensity of F@H (50 μg/mL) upon the addition of 50 μmol/L NaClO in Tris-HCl buffer (10 mmol/L, pH=5.5). λ_ex = 488 nm, λ_em = 520 nm.

S4. Cytotoxicity of F@H on 4T1 cells. Cells were incubated with 0-100 μmol/L F@H in DMEM medium containing 10% fetal bovine serum (FBS) for 24 h. ppm: μg/mL