Construction strategy for ratiometric fluorescent probe based on Janus silica nanoparticles as a platform toward intracellular pH detection

Herein, we figured out a novel ratiometric fluorescent probe based on Janus silica nanoparticles (SiO 2 NPs) where fluorescein isothiocyanate (FITC) and rhodamine B (RB) were asymmetrically functionalized for intracellular pH detection. With this unique strategy, the probe exhibited dual emission bands at 530 and 580 nm upon excitation at a single wavelength of 488 nm. The pH titrations of the probe showed a remarkable increase in ratiometric intensities ratio (I 530nm /I 580nm ) when the pH was switched from 3.0 to 8.0 with a acid dissociation constant (pKa) value of 6.64. The probe was successfully applied to imaging and detection of pH in living cells without noticeable cytotoxicity, indicating that it is a promising candidate for bioanalysis and bioimaging.