Ratiometric photoluminescence sensing based on Ti₃C₂ MXene quantum dots as an intracellular pH sensor

Intracellular pH sensing is of importance and can be used as an indicator for monitoring the evolution of various diseases and the health of cells. Here, we developed a new class of surface-functionalized MXene quantum dots (QDs), Ti₃C₂, by the sonication cutting and hydrothermal approach and further explored their intracellular pH sensing. The functionalized Ti₃C₂ QDs exhibit bright excitation-dependent blue photoluminescence (PL) originating from the size effect and surface defects. Meanwhile, Ti₃C₂ QDs demonstrate a high PL response induced by the deprotonation of the surface defects. Furthermore, combining the highly pH sensitive Ti₃C₂ QDs with the pH insensitive [Ru(dpp)₃]Cl₂, we developed a ratiometric pH sensor to quantitatively monitor the intracellular pH values. These novel MXene quantum dots can serve as a promising platform for developing practical fluorescent nanosensors.