Near-infrared fluorescent probes with higher quantum yields and neutral pKa values for the evaluation of intracellular pH

We have developed two near-infrared fluorescent probes for pH, named pH-A and pH-B. The fluorescence quantum yields of pH-A and pH-B are 0.19 and 0.095 in methanol. And there is the neutral pKa value of pH-A (pKa = 7.2). What is the most important is that these probes can stain the cells, which can reflect the changes of pH in cells.