Fig. 4.

(a) Fluorescence imaging of HeLa cells treated with 10 μM of probe A in a series of pH-adjusted buffers, each supplemented with 10 μM nigericin. The green fluorescence channel (I) captures the emission of probe A within the range of 425–525 nm, while the red fluorescence channel (II) detects near-infrared emission spanning 600–700 nm. Green fluorescence was visualized using Alexa Fluor 405 (excitation at 405 nm), and red fluorescence was monitored using Alexa Fluor 568 (excitation at 559 nm). Scale bars in all images represent 50 μm. (b) Histograms illustrating the emission intensities from channel I (green) and channel II (red) (top), and the fluorescence intensity ratio of channel II to channel I for probe A in HeLa cells (bottom) under varying pH conditions, as quantified from the fluorescence images with SD bars based on n = 3.