有機/無機複合型ZnS:Mnナノクリスタル蛍光体の発光機構と局所構造解析

抄録

When a diameter of doped semiconductor phosphor goes down to less than Bohr diameter, its quantum efficiency of luminescence becomes larger than that of a conventional bulk material. This issue has been comprehensively studied since Bhargava's report appeared in 1994. Nanosizing enhances interaction between a host and a dopant to induce effective energy transfer. Surface modification of nanosize phosphors plays significant roles in capping of surface luminescent killers and the confinement of electron-hole pairs inside a nanoparticle. We have studied the photoluminescence properties of Mn²⁺-doped ZnS (ZnS:Mn) nanocrystal phosphors modified by organic compounds with functional groups, such as carboxyl and phosphoric groups. Since functional groups are simultaneously excited with ZnS, we focus on energy transfer from functional groups to Mn²⁺ ions as well as the above-mentioned effects. Electron paramagnetic resonance spectroscopy reveals a near-surface Mn²⁺ site with a lower symmetry, which is characteristic of nanocrystal. This lower symmetry explains the higher probability of d-d transition of Mn²⁺ ions as well as stronger interaction between Mn²⁺ and ZnS and between Mn²⁺ and functional groups, as compared to an inside Mn²⁺ site. Here I introduce our recent works on organic/inorganic hybrid ZnS:Mn nanocrystal phosphors.