Synthesis and characterization of rare earth doped sol-gel derived monoliths containing nanomaterials

Recently pioneering experiments on the luminescent properties of RE ions coupled to nano-scale materials have generated a great deal of excitement. However, few studies have led to an understanding of the spectroscopic properties of RE ions in the presence of low-dimensional nano-scale materials with different concentrations in spite of the practical interest of these materials. This is largely due to the difficulty of fabricating the codoped materials. The emphasis of our work has been placed on the influences of low-dimensional nano-scale materials on the luminescent properties of europium ions. We believed that their anisotropic structures and quantum size and shape effects of low-dimensional nano-scale materials would exclusively modify the optical properties of RE ions.; One-dimensional nano-scale materials, specifically vanadium oxide nanotubes, were successfully embedded in Eu3+ doped silica monoliths that were prepared by a sol-gel method. Evidence suggests that the introduction of anisotropic vanadium oxide nanotubes results in an increase of photoluminescence intensity. This behavior is thought to be related to the capturing of the excited electrons in the trap centers near the vanadium oxide nanotubes, which is likely improve the absorption cross section of Eu3+ ions.; Spectroscopic properties of Eu3+ ions were also examined in the presence of two-dimensional silver nanoparticles of differing sizes, morphologies, and concentrations. Due to the thermal instability of the two-dimensional Ag nanoparticles synthesized using a solution-phase chemical approach, an alterative methodology has been developed to enable the incorporation of Ag nanoparticles into gel-derived mesostructured silica monoliths through a directed copolymer synthesis with the heat treatment only at 45°C for 36h. Luminescent intensity of the Eu3+ doped samples was enhanced in the presence of silver nanoparticles with low particle concentration, which was thought to result from coupling between the surface plasma resonance of the silver nanoparticles and the Eu3+ ions. The study of hypersensitivity ratio showed no significant changes occurred with the incorporation of Ag nanoparticles in matrix. The changes in the luminescent properties of the Eu3+ doped mesostructured silica monolithic samples were then considered in terms of the modification to the local electric field around Eu3+ ions.