Electrochemiluminescence observing the surface features of Ru-doped silica nanoparticles based on nanoparticle-ultramicroelectrode collision.

We present an innovative and sensitive electrogenerated chemiluminescence (ECL) strategy for observing the surface feature of a single silica nanoparticle based on its collision with an ultramicroelectrode (UME). As an ECL luminophore, Ru(bpy)3 2+ molecules are doped into silica nanoparticles. The stochastic collision events of Ru(bpy)3 2+ -doped silica nanoparticles (RuSNPs) can be tracked by observing the ECL 'blips' from the ECL reaction of Ru(bpy)3 2+ with a coreactant in solution. When RuSNPs collided with UME, Ru(bpy)3 2+ molecules that only exist near the collision site of silica nanoparticles (NPs) were electrochemically oxidized to form Ru(bpy)3 3+ , and then emitted light, because silica NPs are insulated. The inhomogeneous properties of silica nanoparticle surfaces will produce diverse ECL blips in intensity and shape. In addition, distribution gradients from the he Ru(bpy)3 2+ in a silica matrix also affect ECL blips. Some information on the surface properties of silica NPs can be obtained by observation of single silica collision events.