Core–shell structured phosphorescent nanoparticles for detection of exogenous and endogenous hypochlorite in live cells via ratiometric imaging and photoluminescence lifetime imaging microscopy† †Electronic supplementary information (ESI) available: Experimental procedures, characterisation data, Scheme S1 and Fig. S1–S3. See DOI: 10.1039/c4sc02600d

We report a ratiometric phosphorescence sensory system for hypochlorite (ClO ) based on core–shell structured silica nanoparticles. Two phosphorescent iridium(III) complexes were immobilised in the inner solid core and outer mesoporous layer of the nanoparticles, respectively. The former is insensitive to ClO and thus serves as an internal standard to increase the accuracy and precision, while the latter exhibits a specific and significant luminogenic response to ClO , providing high selectivity and sensitivity. Upon exposure to ClO , the nanoparticles display a sharp luminescence colour change from blue to red. Additionally, intracellular detection of exogenous and endogenous ClO has been demonstrated via ratiometric imaging and photoluminescence lifetime imaging microscopy. Compared to intensity-based sensing, ratiometric and lifetime-based measurements are independent of the probe concentration and are thus less affected by external influences, especially in intracellular applications.