Sol-gel Preparation And Optical Properties Of Ag(Eu³⁺/Sm³⁺) Co-Doped Sodium Borosilicate Glass

The surface plasmon resonance(SPR) of noble metallic nanoparticles(NPs) especially gold and silver NPs is a remarkable phenomenon, causued by the collective oscillation of the noble metallic valence electrons resonantly excited by visible light. The SPR forms local enhanced electromagnetic field around the surface of metallic NPs, where the molecules luminescence is tremendously increased, that is commonly known as metal enhanced fluorescence. Therefore, the mechanism between the noble metallic NPs and the luminescence centers of rare earth ions has received numerable attentions. This paper aims to study the influence of the noble metallic NPs on the enhancing or quenching mechanism of rare earth luminescence, which was synthesized by the methods of sol-gel combined with atmosphere control. The photocatalytic experiment was taken under mercury lamp to evaluate the photocatalytic activity of Ag(Eu3+/Sm3+) co-doped NBS glass obtained in reducing atmosphere at different temperatures. Besides, the third-order nonlinearity of the glass was analysised by Z-scan technology. The main results are summarized as follows:(1) Pure Na2O-B2O3-SiO2(NBS) glass was prepared by the methods of sol-gel combined with atmosphere control under different drying rate and different heating rate to obtain the integrated glass without cracks. The composition and the structure of the specimens during the process from wet gel to xerogel were characterized by the means of thermogravimetric-differential scanning calorimetry(TG-DTA), Fourier-infrared(FT-IR) spectroscopy, and solid- state nuclear magnetic resonance(SSNMR) technology.-O-Si-O- network was formed through hydrolysis, dehydration, and dealcoholization of tetraethoxysilane at room temperature. And-O-B-O- bond was formed through dehydration of boric acid. As the temperature increases, boron atoms will be integrated into the silicon-oxygen network to form-O-Si-B- bonds. Sodium oxide provides bridge oxygen to [BO3] making it convert to tetrahedral [BO4] units. Up to 600 degree, a large number of tetrahedral [BO4] and [SiO4] units are formed in the glass, resulting in highly compact glass.(2) Ag-Eu3+ co-doped sodium borosilicate glass was successfully synthesized by using the sol-gel and atmosphere control methods. Further more, different kinds of silver species, id est, Ag+, Ag aggregates and Ag NPs, were prepared by adjusting the reduction duration and reduction temperature to study the effect on the luminescence of Eu3+. Under 270 and 345 nm excitation, enhancement of Eu3+ luminescencewas ascribed to energy transfer(ET) from isolated Ag+ and Ag aggregates to Eu3+, respectively. The phenomena about enhancement of Eu3+ luminescence by Ag NPs was not observed either under 270 nm(non-resonant) or use 393 nm(resonant excitation) excitationin this system. The microstructure and formation mechanism of samples were investigated by X-ray diffraction(XRD), transmission electron microscopy(TEM), Brunauer-Emmett-Teller(BET) measurements, respectively. Furthermore, rhodamine solution was used to evaluated the photocatalytic activity of Ag-Eu3+ co-doped glasses which were reduced at different temperatures, and the largest of catalytic efficiency was 18.8%, under mercury lamp. Moreover, third-order optical nonlinearity of the glass was measured by Z-scan technology, and the value of χ(3)(esu) was 7.51×10-11 which is 6 orders of magnitude than that of pure NBS glass.(3) Ag-Sm3+ co-doped sodium borosilicate glass was successfully synthesized by using the sol-gel and atmosphere control methods. Furthermore, different kinds of silver species like isolated Ag+, Ag aggregates, and Ag NPs, were prepared by adjusting the reduction duration and reduction temperature to study the effect on the luminescence of Sm3+. Under 270 and 350 nm excitation, significant enhancement of Sm3+ luminescencewas ascribed to ET from isolated Ag+ and Ag aggregates to Sm3+, respectively. The phenomena about enhancement of Sm3+ luminescence by Ag NPs was not observed either under 270 nm(non-resonant) or 401 nm(resonant excitation) excitationin this system. Furthermore, rhodamine solution was used to evaluated the photocatalytic activity of Ag-Sm3+ co-doped glasses reduced at different temperatures, and the largest of catalytic efficiency was 13.2%, under mercury lamp. Moreover, third-order optical nonlinearity of the glass was measured by Z-scan technology, the value of χ(3)(esu) was 7.51×10-11 which is 6 orders of magnitude than that of pure NBS glass.