Steady-State Electrochemiluminescence at Single Semiconductive Titanium Dioxide Nanoparticles for Local Sensing of Single Cells.

Obtaining steady-state bright electrochemiluminescence (ECL) at single nanoparticles is crucial but challenging for the realization of the single-nanoparticle electrochemical sensing of single cells. In this work, steady-state bright ECL is implemented at single semiconductive titanium dioxide (TiO2) nanoparticles for sensing the local efflux from single living cells. Oxygen vacancies on the surface of rutile TiO2 nanoparticles have a high affinity for hydrogen peroxides that are not easily passivated upon exposure to voltage. Therefore, the steady-state adsorption of hydrogen peroxide by the TiO2 nanoparticle surface permits the continuous electrochemical generation of superoxide and hydroxyl radicals by electrons and surface-trapped holes at the nanoparticles, resulting in constant ECL under physiological conditions. This steady-state luminescence during continuous imaging is correlated with the concentration of hydrogen peroxide, leading to the local ECL visualization of hydrogen peroxide efflux from single cells. The successful local ECL imaging demonstrated herein provides an unprecedented approach to enable subcellular electroanalysis using single nanoparticles.