Fig. 1. (A) Absorption spectra of probe 1 (10 μM) (a) before and (b) after reaction with carboxylesterase (1 U mL⁻¹). (B) Fluorescence spectra of probe 1 (10 μM) reacting with carboxylesterase at different concentrations (0, 0.01, 0.025, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4, 0.6 and 1 U mL⁻¹). The reaction was performed in 10 mM PBS at 37 °C for 20 min. λ_ex/em = 670/706 nm.