Preparation And Luminescent Properties Of Three - Dimensional Ordered Macroporous Materials With Rare Earth Doped Ag - SiO 2

In recent years, the development of three-dimensional ordered macroporous material (3DOM) research is very rapid. Three dimensional ordered macroporous (3DOM) materials composed of interconnected nanocrystals have unique structural properties such as three-dimensional periodicity and large surface area, which make them useful for catalysis, cavities and membrane science. In addition to their structure characters, the 3DOM materials have unique optical properties such as photonic band-gap properties, which can control propagation of light and allow the preparation of sensors based on changes of refractive index. By doping the 3DOM materials with rare earth ions, the 3DOM materials can modify optical properties of rare earth ions, which could be used in several fields such as high light-emitting diodes, lasers, solar cells, optical switches, and electro-optical modulators. At present, lots of research was performed on the unique structural and optical properties of rare earth (RE) doped 3DOM materials. However, the RE ions doped 3DOM materials generally have low emission efficiency due to their structure defects and small excitation cross sections from RE ions caused by the parity forbidden intra-4f shell transitions, which limited the their application. Therefore, improving luminescence intensity of RE doped 3DOM materials is advantage to their practical application. In this paper, the rare earth ions doped Ag-SiO2 three-dimensional ordered macroporous materials were successfully synthesized by colloidal crystal template method, the presence of Ag state and its effect on the properties of rare earth ion luminescence in three-dimensional ordered macroporous materials were investigated.The rare earth ions doped Ag-SiO2 three-dimensional ordered macroporous materials were successfully synthesized by self-assembly method and sol-gel method. The existing states and photoluminescence property of silver in the SiO2 3DOM materials was investigated. The results show that only Ag ions exist in the SiO2 3DOM materials sintered at the temperature below 450 ℃. With the increasing of sintering temperature, the Ag+ ions transform gradually to Ag+-Ag+, simultaneously, part of Ag+-Ag+ transform to Ag nanoparticles. The Ag+-Ag+ and Ag nanoparticles are formed in the SiO2 3DOM materials sintered at temperature from 450 to 650 ℃. At last, only Ag nanoparticles occur in the SiOa 3DOM materials prepared at 750 ℃. Formation mechanisms of Ag species were discussed in the SiO2 3DOM materials.The Ag nanoparticles including SiO2:Tb3+ three dimensionally ordered macroporous (3DOM) composites were successfully synthesized by colloidal crystal template method. The influence of Ag nanoparticles on photoluminescence property of SiO2:Tb3+ 3DOM material was investigated. The results indicate that typical emission bands at 489,543,587 and 623 nm from Tb3+ were observed in the SiO2:Tb3+ 3DOM materials under the excitation of 235 nm. The Ag nanoparticles can greatly enhance the light emission from Tb3+ in SiO2:Tb3+ 3DOM material, which was attributed to the increased radiative decay rates of Tb3+ caused by Ag nanoparticles.Finally, The influence of Ag exist states on photoluminescence property of Eu3+ doped Ag-SiO2 three-dimensional ordered macroporous material prepared by 550 ℃ were investigated. The results showed that the mainly exist states of Ag in the sample are Ag+-Ag+ and Ag nanoparticles. The results show that luminescence enhancement of Eu3+ ions was obtained by Ag species in the SiO2 3DOM materials. For the SiO2 3DOM materials prepared by 550 ℃, the enhancement of Eu3+ luminescence is attributed to energy transfer from Ag+-Ag+ to Eu3+ under 345 and 280 nm excitation, while luminescence enhancement of Eu3+ is due to energy transfer from isolated Ag+ to Eu3+ under the excitation of 245 nm. For the SiO2 3DOM materials prepared by 750 ℃, luminescence of Eu3+ were enhanced due to plasmon resonance effect of Ag nanoparticles.