Ho3+/Yb3+/Tm3+ tri-doped NaY1-x(WO4)2 phosphors with proper doping concentrations of Ho3+, Yb3+ and Tm3+ (x = Ho3+ +Yb3+ +Tm3+, Ho3+ = 0.04, 0.03, 0.02, 0.01, Yb3+ = 0.35, 0.40, 0.45, 0.50 and Tm3+ = 0.01, 0.02, 0.03, 0.04) were successfully synthesized via the microwave sol-gel route, and their upconversion properties were investigated. Well-crystallized microcrystalline particles showed fine and homogeneous microcrystalline morphology with particle sizes of 1-2 μm. The optical properties were comparatively examined using photoluminescence emission and Raman spectroscopy. Under excitation at 980 nm, the doped particles exhibited white emissions based on blue, green and red emission bands, which correspond to the 1G4→ 3H6 transitions of Tm3+ in the blue region, the 5S2/ 5F4→ 5I8 transitions of Ho3+ in the green region, the 5F5→ 5I8 transitions of Ho3+, and the 1G4→ 3F4 and 3H4→ 3H6 transitions of Tm3+ in the red region. The pump power dependence of the upconversion emission intensity and the Commission Internationale de L'Eclairage chromaticity coordinates of the phosphors were evaluated in detail.

NaCaLa1-x(MoO4)3:Ho3+/Yb3+ ternary molybdates with proper doping concentrations of Ho3+ and Yb3+ (x = Ho3+ +Yb3+, Ho3+ = 0.05 and Yb3+ = 0.35, 0.40, 0.45 and 0.50) were successfully synthesized by microwave sol-gel method. Well-crystallized particles formed after heat-treatment at 900 oC for 16 h showed a fine and homogeneous morphology with particle sizes of 3-5 μm. Under excitation at 980 nm, the UC intensities of the doped samples exhibited strong yellow emissions based on the combination of strong emission bands at 520-nm and 630-nm emission bands in the green and red spectral regions, respectively. The optimal Yb3+:Ho3+ ratios were obtained at 9:1 and 10:1, as indicated by the compositiondependent quenching effect of the Ho3+ ions. The pump power dependence of the upconversion emission intensity and the Commission Internationale de L'Eclairage chromaticity coordinates of the phosphors were evaluated in detail.

NaLa1-x(MoO4)2:Ho3+/Yb3+ phosphors with the correct doping concentrations of Ho3+ and Yb3+ (x = Ho3++Yb3+, Ho3+ = 0.05 and Yb3+ = 0.35, 0.40, 0.45 and 0.50) were successfully synthesized by the microwave-modified sol-gel method. Well-crystallized particles formed after heat-treatment at 900 oC for 16 h showed a fine and homogeneous morphology with particle sizes of 3-5 μm. The optical properties were examined using photoluminescence emission and Raman spectroscopy. Under excitation at 980 nm, the UC intensities of the doped samples exhibited strong yellow emissions based on the combination of strong emission bands at 545-nm and 655-nm emission bands in green and red spectral regions, respectively. The strong 545-nm emission band in the green region corresponds to the 5S2/5F4→ 5I8 transition in Ho3+ ions, while the strong emission 655-nm band in the red region appears due to the 5F5→ 5I8 transition in Ho3+ ions. Pump power dependence and Commission Internationale de L'Eclairage chromaticity of the upconversion emission intensity were evaluated in detail.

Pb1-xMoO4:Er3+/Yb3+ phosphors with various doping concentrations of Er3+ and Yb3+ (x = Er3++Yb3+, Er3+ = 0.05, 0.1, 0.2, and Yb3+ = 0.2, 0.45) are successfully synthesized using a microwave sol-gel method, and the up-conversion photoluminescence properties are investigated. Well-crystallized particles, which are formed after heat treatment at 900 oC for 16 h, exhibit a fine and homogeneous morphology with particle sizes of 2-5 μm. Under excitation at 980 nm, the Pb0.7MoO4: Er0.1Yb0.2 and Pb0.5MoO4:Er0.05Yb0.45 particles exhibit a strong 525 nm emission band, a weak 550 nm emission band in the green region, and a very weak 655 nm emission band in the red region. The Raman spectra of the doped particles indicate the presence of strong peaks at higher and lower frequencies induced by the disordered structures of Pb1-xMoO4 through the incorporation of the Er3+ and Yb3+ ions into the crystal lattice, which results in the unit cell shrinkage accompanying the new phase formation of the MoO4-x group.

NaLa1-x(MoO4)2:Eu3+/Yb3 phosphors with doping concentrations of Eu3+ and Yb3+ (x=Eu3++Yb3+, Eu3+=0.05, 0.1,0.2 and Yb3+=0.2, 0.45) were successfully synthesized by the microwave-modified sol-gel method, and the upconversion andspectroscopic properties were investigated. Well-crystallized particles showed a fine and homogeneous morphology with particlesizes of 2-5µm. Under excitation at 980nm, NaLa0.5(MoO4)2:Eu0.05Yb0.45 particles exhibited a strong 525-nm emission bandand a weak 550-nm emission band in the green region, and a very weak 665-nm emission band in the red region. The strong525-nm emission in the green region corresponds to the 7F1→5D1 transition and the weak 550-nm emission in the green regioncorresponds to the 7F0→5D2 transition, while the very weak emission 665-nm band in the red region corresponds to the5D0→7F3 transition. The Raman spectra of the doped particles indicated the domination of strong peaks at higher frequenciesof 762, 890, 1358 and 1430cm−1 and weak peaks at lower frequencies of 323, 388 and 450cm−1 induced by the disorder ofthe [MoO4]2− groups with the incorporation of the Eu3+ and Yb3+ elements into the crystal lattice or by a new phase formation.

Multi-elements doped TiO2 was prepared as a new photocatalyst in order to decrease the band gap of TiO2 by sol-gel process which can provide the large active sites of TiO2. Multi-elements were doped by using a single precursor, tetraethylammonium tetrafluoroborate (TEATFB). By the benefit of large specific surface area of TiO2 prepared by sol-gel process, catalysts showed initial fast removal of dye. The photoactivity showed that the doped catalysts significantly promote the light reactivity than undoped TiO2. The commendable photoactivity of prepared catalysts is predominantly attributable to the doping of anions which may reduce the band gap.