Tunable visible emission and white light generation by Ag nanoclusters in Tm3+/Yb3+ doped GeO2-PbO glasses

GeO2-PbO glasses demonstrated to be adequate hosts for incorporation of rare-earth ions and nucleation of metallic nanoparticles. However, Ag nanoclusters were not explored in GeO2-PbO glasses. The luminescence of Ag nanoclusters in glasses has several applications such as UV-driven flexible color monitors, mercury-free white light generation under UV pumping, tunable light sources/lasers, and solar cells. The present investigation shows white light generation by Ag nanocluster in Tm3+/Yb3+ doped GeO2-PbO glasses. Moreover, we also demonstrate tunable visible emission provided by Ag nanoclusters. Glasses were produced by melt-quenching technique followed by annealing to reduce internal stress. Different emission colors ranging from the blue to the green-yellowish were obtained for GeO2-PbO glasses doped only with AgNO3, under different excitation wavelengths. Doping GeO2-PbO glasses with AgNO3 and Yb3+/Tm3+ ions resulted in a blue emission for excitation at 405nm, whereas white light generation was observed for excitation with a commercial 365 nm UV lamp. The photoluminescence (PL) was attributed to the combination of emission bands, from Tm3+ ions and Ag nanoclusters. The results reported herein show the potential of GeO2-PbO glasses for white light emitting devices such as light phosphors for UV light driven W-LEDs.