Synthesis of europium-doped silica microspheres using the sol-gel microencapsulation method

This paper demonstrates the preparation of europium (Eu ³⁺) doped silica microspheres using the W/O microencapsulation method. The water phase (W phase) solution is composed of partially hydrolyzed tetraethyl orthosilicate and acetylsalicylic acid acting as hydrophilic active agents. The Eu(NO) ₃•H ₂O was added into the W phase solution before mixing with the oil phase solution. Under a controlled stirring treatment, the W/O emulsion is obtained by dispersing the W phase solution in cyclohexene containing Span60 as the surfactant. 3-aminopropyl-triethoxysilane (APTES) is used as a gelling agent to encapsulate the micelles and Eu ³⁺ doped silica microspheres with a mean size of around 2 μm can be obtained. The experimental parameters, such as the W/O ratio, stirring condition, the amount of APTES added and the temperature, are modified and their effects on the morphology and homogeneity of the resulting Eu ³⁺ doped silica microspheres are systematically studied. The Eu ³⁺ ions are successfully confined inside the silica microcapsules, exhibiting an optimal red emission with a doping concentration of 3 mol%.