Fig. 1. ¹H NMR spectrum of PAH (400 MHz, d6-DMSO)

Fig. 1. The change of UV-Vis spectra (a) and line graph (b) of probe PAH (0.1 mmol·L^-1) in the range from pH 2.0~12.0 using PBS as buffer solution; The color change of photography of probe PAH with the pH value increases under natural light (inset)

Fig. 1. The synthetic route to probe PAH

Fig. 2. ¹³C NMR spectrum of PAH (d6-DMSO)

Fig. 2. Absorption intensity (a—c) at 424 nm of probe PAH (0.1 mmol·L^-1) with addition of different species (0.4 mmol·L^-1) in the absence/presence of ClO^- (0.4 mmol·L^-1) in PBS solution (0.01 mol·L^-1, pH 5.0), Error bar=RSD (n=3); Visible color (d—f) of probe PAH toward ClO^- (0.4 mmol·L^-1) in different species under sunlight

Fig. 2. The proposed recognition mechanism of probe PAH toward ClO^-

Fig. 3. UV-Vis absorption spectra (b) of PAH (0.1 mmol·L^-1) in the presence of I^- toward various concentration of ClO^- in PBS buffer solution (0.01 mol·L^-1, pH 5.0); The change of visible color (a) of probe PAH toward ClO^- under sunlight

Fig. 3. UV-Vis spectra of PAH (0.1 mmol·L^-1) with addition of nitrate salts of Li⁺, Co²⁺, Cr³⁺, K⁺, Cd²⁺, Pb²⁺, Ca²⁺, Hg²⁺, Ba²⁺, Cu²⁺, Mg²⁺, Ni²⁺, Zn²⁺, Al³⁺ and Fe³⁺(0.4 mmol·L^-1), sodium salts of NO2-, I^-, AcO^-, ClO4-, SO42-, CN^-, Br^-, CO32- and F^- (0.4 mmol·L^-1), ClO^- (0.4 mmol·L^-1), GSH, Vc and ROS/RNS of ONOO^-, ROO·, ·OH, H₂O₂, ·O2-,^tBuOOH, ^tBuO·, ¹O₂ and NO· (0.4 mmol·L^-1) in PBS solution (0.01 mol·L^-1, pH 5)

Fig. 4. UV-Vis absorption spectra (a—d) of PAH (0.1 mmol·L^-1) with the addition of NO2-, GSH, Vc, ONOO^- toward various concentration of ClO^- in PBS buffer solution (0.01 mol·L^-1, pH 5.0); The change of visible color of probe PAH toward ClO^- under sunlight (inset)

Fig. 4. UV-Vis spectra (a) of probe PAH (0.1 mmol·L^-1), changing of the absorption intensity (b) at 424 nm of probe PAH upon addition of increasing concentrations (0~1.4 mmol·L^-1) of ClO^- in PBS (0.01 mol·L^-1, pH 5.0) and linearity of absorption intensity (c) of probe PAH with the addition of ClO^- from 0~0.28 mmol·L^-1. Error bar=RSD (n=3)

Fig. 5. UV-Vis absorption spectra of indolinium in the absence/presence of ClO^- in aqueous solution and UV-Vis absorption spectra of probe PAH (0.1 mmol·L^-1) in the presence of ClO^- (0.12 mmol·L^-1 or 0.4 mmol·L^-1) in PBS (0.01 mol·L^-1, pH 5.0); Photography of indolinium in the absence/presence of ClO^- (inset)

Fig. 5. UV-Vis spectra of probe PAH (0.1 mmol·L^-1) with the addition of ClO^- (0~1.4 mmol·L^-1) in PBS (0.01 mol·L^-1) in pH 2.0 (a), pH 7.4 (b), respectively; The photography change of visible color of probe PAH toward ClO^- under sunlight (inset)

Fig. 6. UV-Vis spectra of probe PAH (0.1 mmol·L^-1) with the addition of ClO^- (0~1.4 mmol·L^-1) in PBS (0.01 mol·L^-1) in pH 3.0 (a), pH 4.0 (b), pH 5.0 (c), pH 6.0 (d), pH 7.0 (e), pH 8.0 (f), pH 9.0 (g), pH 10.0 (h), pH 11.0 (i), pH 12.0 (j), respectively; The photography change of visible color of probe PAH toward ClO^- under sunlight (inset)

Fig. 7. Comparison of the interaction time between PAH (0.1 mmol·L^-1) and ClO^- (0.8 mmol·L^-1) in aqueous solution of PBS (0.01 mol·L^-1, pH 2.0~12.0)

Fig. 8. HRMS of intermediate 1
The peak (m/z) at 160.111 89 corresponds to [M+H]⁺ ion (Calcd: 159.10)

Fig. 9. HRMS of 2-hydroxybenzoic acid
The peak (m/z) at 139.038 97 corresponds to [M+H]⁺ ion (Calcd: 138.03)

Fig. 10. HRMS of intermediate 2
The peak (m/z) at 282.115 84 corresponds to [M+H]⁺ ion (Calcd: 281.11)

Table 1. Determination of ClO^- concentrations in real samples