Theory and Simulation for Optimising Electrogenerated Chemiluminescence from Tris(2,2'-bipyridine)-ruthenium(II)-Doped Silica Nanoparticles and Tripropylamine

Electrochemiluminescence (ECL), that is, light emission from an electronically excited species generated by electrochemical means, sustains powerful (bio)analytical methods for the ultrasensitive detection of biological targets. Co-reactant systems involving an inexpensive organic molecule, most generally a tertiary amine, and a metal complex luminophore are commonly used for such purposes. Owing to the high cost of the luminophore moiety, several groups have considered minimising its quantity by sequestrating it at high concentration inside nanoparticles. However, to be efficient and to optimise ECL responses, this strategy requires that the nanoparticle carrier is suitably placed inside the diffusion layer of the oxidised organic co-reactant. In this work, we firstly investigated this optimisation problem by introducing a rather simple analytical model to delineate qualitatively the main mechanistic features controlling the ECL intensity. This was then analysed in more detail by using 2D simulations. Analysis of these 2D-heavy simulations in terms of memory occupation and CPU time, evidenced that similar results (i. e. with a relative precision best than a few percent) could be achieved with much faster 1D simulations. These 1D simulations allowed specifying quantitatively the main features of the analytical model qualitative predictions and to propose simple rules for the optimisation of the luminophore-doped nanoparticles placement inside the diffusion layer of the organic co-reactant.