Fig. 1. (A) The UV-vis absorption spectra and (B) fluorescence spectra of CyI-S-diCF₃ (10 μM) after incubation with different concentrations of GSH (0–100 μM) in PBS (10 mM, pH 7.4, 30% DMSO). (C) Fluorescence responses of CyI-S-diCF₃ (10 μM) with the addition of various amino acids (100 μM) in PBS (10 mM, pH 7.4, 30% DMSO) at 37 °C for 5 min (blank, GSH, Cys, Hcy). (D) The NIR-I fluorescence spectra of CyI-S-diCF₃ (10 μM) in the presence of GSH (100 μM) with or without addition of NMM (100 μM) in PBS (10 mM, pH 7.4, 30% DMSO) at 37 °C for 5 min.