Numerical Simulation of Doped Silica Nanoparticle Electrochemiluminescence

In the present work we numerically simulated the electrogenerated chemiluminescence (ECL) from a Ru(bpy)32+-doped silica nanoparticle (Ru-DSNP) in buffer containing tripropylamine (TPrA). Experimental study reported from Zanarini et al showed that ECL intensity for the Ru-DSNP/TPrA system exhibits two emission waves while the potential of working electrode is swept in positive direction. The first ECL wave with a peak at ~0.9 V (vs. Ag|AgCl) is triggered by TPrA oxidation and is governed by the deprotonation equilibrium of TPrA cation radical (TPrA•+ = TPrA• + H+). We present a model for the description of the first ECL wave, which also takes in consideration the influence on the deprotonation equilibrium of the electrode surface functionality. This model indicated that the detachment of a Ru-DSNP (initially bound to the electrode surface via alkylthiols linkers) from the electrode surface and the subsequent electrode surface oxidation facilitate the radical deprotonation on the electrode surface causing the ECL quenching. The second ECL wave having its peak at ~1.2 V is triggered by direct Ru(bpy)32+ oxidation. We modeled the second ECL wave as related to the electron hopping mechanism between Ru(bpy)32+ labels inside the Ru-DSNP. The results of the numerical simulations indicate that electrode surface functionality modification, which occurs during potential sweep, and the electron hopping mechanism between Ru(bpy)32+ labels play important roles in defining the Ru-DSNP/TPrA ECL signal