pH-Dependent fluorescence of [La(OH)$_{2}$]$^{+}$ [ARS]$^{–}$ hybrid nanoparticles for intracellular pH-sensing

Saline inorganic–organic hybrid nanoparticles (IOH-NPs) [La(OH)$_{2}$]$^{+}$ [ARS]$^{–}$ (ARS: alizarin red S) are prepared in water as a new compound (particle size: 47 ± 7 nm, ARS load: 65 wt%). The IOH-NPs not only show a pH-dependent absorption colour but also a pH-dependent fluorescence with green emission at pH 5.0–9.0 and red emission at pH < 4.5. According to first in vitro studies, the pH-dependend fluorescence can be used to monitor nanoparticle internalization in cells as well as the respective intracellular pH.