Effect of polymer cations on photoluminescence properties of blue emitting alkaline-earth metals and silicon based phosphors

Efficient blue emitting phosphors were prepared by depositing mixed hydroxides of Ca, Sr, Ba, Mg, Eu over spherical SiO2 particles from tetra-ethyl-orthosilicate (TEOS) pre-coated with polycations (polyethyleneimine: PEI) followed by calcination at 1200 degrees C in a reducing atmosphere. The prepared phosphor showed intense blue emission, which can be ascribed to 4f(7)-4f (6)5d interconfiguration transitions of Eu2+ ions. In contrast, the luminescence intensity of the phosphor was much decreased when prepared without polycations. It was suggested that negatively charged hydroxides are deposited on positively charged Si02 surfaces pre-coated with polycations through electrostatic self-assembly interaction. The common formula of the prepared phosphors is AMgSi(2)O(6):Eu2+ (A = Ca, Sr, Ba or fraction of Ca and Sr), where alkaline-carth/Si = 1, the each entire sample was prepared by treating with polycations and without polycations.