Fig. 1. Fluorescence spectra of OP-OAc in the four solvents

Fig. 2. Fluorescence spectra and standard curve of OP-OAc in water
(a): Fluorescence spectra; (b): Standard curve

Fig. 3. Fluorescence spectra and fluorescence intensity of OP-OAc in methanol-water, ethanol-water and acetonitrile-water
(a): Fluorescence spectra of methanol-water; (b): Fluorescence intensity of methanol-water;(c): Fluorescence spectra of ethanol-water; (d): Fluorescence intensity of ethanol-water;(e): Fluorescence spectra of acetonitrile-water; (f): Fluorescence intensity of acetonitrile-water

Fig. 4. Fluorescence spectra and fluorescence intensity of OP-OAc at different pH values
(a): Fluorescence spectra; (b): Fluorescence intensity