Modified Silica-Based Luminescence Materials And Their Luminescence Mechanisms

Silica was widely used in the field of catalyzer carrier, medium material, and buffer layer for silicon-based photoelectronic materials due to its excellent chemical and thermal stabilities, as well as its good combination with silicon. Many studies on the optical property of silica have shown that there are many optic-active defect centers with excellent UV absorption and luminescence in silica. It is significant and important to further study the luminescence property and luminescence mechanism of silica-based materials modified with various cation and anion dopants.The nano-sized silica was synthesized by Sol-Gel method, and the luminescence properties of silica samples heat-treated at different temperatures and in different ambients were examined. It was found that there is a luminescence band at 344nm after heat-treated at lower temperature. There are two luminescence bands with a long tail toward the direction of long wavelength in the silica sample heat-treated in H₂ ambient at higher temperature. On the base of stable preparation of nano-sized silica, Cu²⁺ and Ce³⁺ cations were chemically doped into silica nanoparticles, and their optical absorption and luminescence properties were analyzed. The intensity of luminescence band at 344nm changes with the concentration of doping ions. The luminescent intensity increases with increasing concentration when the concentration of doping ions is low, but the intensity decreases and even disappears with large doping concentrations. Besides the luminescence band at 344nm, the luminescence bands at 355nm and 445nm exist in the Ce³⁺ ions doped silica nanoparticles heat-treated at different temperatures. Those two luminescence bands originate from the 5d-4f transitions of Ce³⁺ ions located in different micro-structures.The excited 5d electron sits in the outer shell, and is much easier to be influenced by ligand fields. The Ce³⁺ ions doped silica samples were further decorated with S^2-, Cl^- and F^-anions by both chemical co-doping and controlled ambient methods. The decoration of those anions changes clearly the wavelength and intensity of luminescence. Especially the luminescence band of Ce³⁺ doped silica decorated by Cl^- ion shifts from 445nm to 390nm and the intensity increases around 20 times. This alteration of luminescent wavelength and intensity is reversible...