Effect Of Ag Occurrence State On The Luminescent Properties Of Rare Earth Ions In Silicate Glass Based On Ag ~ + -Na ~ + Ion Exchange

Rare earth ions (REI)-doped luminescent materials have attracted persistent attention during the past decades because of their novel luminescent performances and wide applications in illumination, display, solid-state lasers and so on. However, due to the parity forbidden character of4f-4f transitions, the absorption cross section of REI is small, which means REI cannot be efficiently excited by ultraviolet (UV) and (or) visible (VIS) light. Consequently, numerous methods, such as host absorption, f-d absorption, and charge transfer state absorption were adopted to improve the excitation efficiencies and to enhance the luminescence of REI. Recently, coupling REI with Ag species has been developed as a valuable approach to enhance the luminescence of REI. We can conclude that the enhancements of REI luminescence were caused by either local field effect induced by surface plasmon resonance (SPR) of Ag nanoparticles or energy transfer from Ag aggregates and isolated Ag+.At present, Ag-doped glasses were usually prepared by doping with Ag compounds (such as AgCl, AgN03) in the glass raw material. Generally, the amount of doped Ag+can not be introduced in high level due to the solubility limit. Otherwise the Ag+will come into being Ag elemental by precipitation. In addition, in the Ag-doped glasses, it is easily formed that the AgT ions, Ag aggregates and Ag nanoparticles coexist, so it is not conducive to distinguish what species of silver and by what mechanism that lead to enhance REI luminescence. In this study, the introduction of silver into the RE ions (Sm3+, Tb3+, Eu3+)-doped sodium-aluminosilicate glasses prepared by Ag+-Na+ion exchange leads to the formation of different ionic silver species. After heat treatment, silver nanoparticles can be formed in the silver ion-exchanged glasses. Upon silver ion-exchanged and heat treatment silver glasses, this enabled us to analyze the sensitization of the luminescence of rare earth ions by different ionic silver species and the influence of silver nanoparticles on the intensity of optical transitions of rare earth ions under investigation.Firstly, excited at250nm-280nm, effective enhancement of RE ions (Sm3+, Tb3+, Eu3+) luminescence is ascribed to energy transfer from isolated Ag+to RE ions. There is an overlap between the emission spectrum of Ag+and the excitation spectrum of RE ions (Sm3+, Tb3+, Eu3+), so the energy transfer from isolated Ag+to RE ions may occur.Secondly, excited at355nm、375nm and350nm, respectively, effective enhancement of RE ions (Sm3+, Tb3+, Eu3+) luminescence of Ag+-Na+ion exchange samples is ascribed to energy transfer from silver aggregates to RE ions. There is an overlap between the emission spectrum of silver aggregates and the excitation spectrum of RE ions (Sm3+, Tb3+, Eu3+), so the energy transfer from silver aggregates to RE ions may occur.Thirdly, the effect of Eu2+ions on the silver occurrence state has been studied. In the process of silver ion exchange and heat treatment, Eu2+ions promote the formation of silver aggregates such as Ag2+, and promote silver nanoparticles precipitate finally.Finally, In the RE ions (Sm3+, Tb3+, Eu3+)-doped glasses containing silver nanoparticles, luminescence weakening was observed, and this weaken effect was discussed by our group.