Kinetics of the direct energy transfer of optical excitation in crystalline nanoparticles: Theory and Monte Carlo computer simulation

A comparative analysis of direct energy transfer kinetics from donors to acceptors (obtained by Monte Carlo simulation in case of donor excitation by short (t pulse < τ D ) pulse) in a sample consisting of spherical nanoparticles with equal diameters and in a bulk crystal is performed. The influence of the finite size of nanoparticles on the process of direct (static) donor-acceptor quenching of optical excitation in nanoparticles with a crystalline structure is analytically studied. It is found that, in three-dimensional spherical nanoparticles, the quenching rates W A or and W B or found on an ordered stage of kinetics and quenching macroparameters γ F A and γ F B found on an disordered stage of kinetics for donors populating sites at the center (A) and in the surface layer (B) of nanoparticles differ by a factor of 2 (donors populating central sites A possess higher rates). An analytical expression describing disordered stage of kinetics of direct Nd3+ → OH− quenching in the sample consisting of spherical nanoparticles with equal diameters and the Y2O3 (I a 3 , T h3 7 ) crystal structure using just two energy transfer macroparameters γ F A and γ F B is proposed.