Factors influencing the luminescence quantum efficiency of nanocrystalline ZnS:Mn2+:

The influence of the Mn²⁺ concentration, the nature of the passivating polymer and UV irradiation on the luminescence efficiency of nanocrystalline ZnS : Mn²⁺ is investigated. With increasing Mn²⁺ concentration the quantum efficiency increases, until it reaches a stable value. No drastic decrease in quantum efficiency is observed at high Mn²⁺ concentrations, as was found earlier for both bulk and nanocrystalline ZnS : Mn²⁺. By altering the passivating polymer many other factors influencing the quantum efficiency are changed, such as the particle diameter and Mn content. This makes it hard to study the influence of the passivating behaviour of the various polymers on the quantum efficiency. The UV enhancement of the quantum efficiency of the various samples could be explained by two mechanisms: UV curing of the passivating polymer and passivation by a photooxidation of the surface of the nanoparticles during the irradiation. The highest quantum efficiency obtained was about 15%.