All chemicals were analytical grade and used without further purification. nanocomposites of CaMoO₄:Eu³⁺ were prepared by a direct feeding microwave synthesis method. In a typical procedure, at a molar ratio of Ca:Mo:Eu of 1:1:0.1, 1.1 g of CaCl₂ was dissolved in 50 ml of 2% PEG aqueous solution, dispersed and dissolved with ultrasonic waves, add 1 mmol of Eu³⁺ reserve liquid, mixed uniform for A solution. 2.42 g of Na₂MoO₄・2H₂O was dissolved in 50 mL of 2% PEG aqueous solution, the dispersion was dissolved by ultrasonic mixing, for B solution. The A, B solutions were mixed rapidly transferred into 250 ml of flask, then the mixed solution was placed in a microwave refluxing system to react for 20 min with a power microwave radiation of 40% and cool down naturally to the room temperature. Then the precipitate was centrifuged, washed with the deionized water for several times and dried at 60˚C in the vacuum for 8 h, The final product was collected for the characterization.

The crystal sttructure of nanocomposites of CaMoO₄:Eu³⁺ was measured by XRD on a Shimadzu XRD-6100 X-ray diffractometer (Cu Kα radiation, λ = 0.15418 nm). The morphology and size of products were determined by SEM. The SEM images were recorded on a Quanta 200 FEG field emission scanning electron microscope. The optical property was obtained by Cary Eclipse fluorescence spectrometer (USA Varian Company).

Figure 1 shows the XRD pattern graph of as-prepared sample. The XRD pattern (peak 2θ: 18.75, 28.82, 31.36, 34.39, 47.13, 49.37, 54.14, 58.11) showed that the product is the Tetragonal system of scheelite structure of CaMoO₄ (JCPDS File No. 29-0351). The diffraction peak is strong and sharp, which indicates that the sample has a high degree of crystallinity.

Figure 2 shows the SEM image of as-prepared sample. It shows that the majority of the catalyst is a relatively flake structure, parts overlap each other, and some particles attached to it. The size of most of the flakes is 50 to 500 nm.

Figure 3 is photoluminescence spectrum of as-prepared sample. The excitation wavelength is 258 nm. It can be seen in the 430 - 450, 590 - 600, 610 - 620, 700 - 710 nm have a certain luminescence, which is the strongest at 615 nm. 430 - 450 nm belongs to calcium molybdate luminescence. The luminescence mechanism of calcium molybdate is due to transition induced by electrons in ion within the groups, belonging to the intrinsic emission. 516 nm has a very high peak, this is a frequency doubling peak of excitation light. At 590 - 600 nm, 610 - 620 nm and 700 - 710 nm, luminescence by Eu³⁺ (⁵D₀ → ⁷F₁), (⁵D₀ → ⁷F₂), (⁵D₀ → ⁷F₄) electronic energy level transition, respectively. Among them, 615 nm (⁵D₀ → ⁷F₂) electric dipole transition emission is the main, it has high emission efficiency, the strongest luminescence properties, and pure red light. So, as-prepared nanocomposite is an ideal red light-emitting material.

The effect of Eu³⁺ ions doping on the luminescence properties was studied. Figure 4 is photoluminescence spectra of samples with different Eu³⁺ doping. It can be seen that when the doping amount of Eu³⁺ ion is less than 0.10 (molar ratio), the luminescence intensity of CaMoO₄:Eu³⁺ composite increases with the increase of the amount of Eu³⁺ ions. When the doping amount of Eu³⁺ ion is 0.10, the luminescence properties are the best. When the doping amount of Eu³⁺ ion is more than 0.10, the amount of Eu³⁺ ions doping will continue to increase, the intensity of the luminescence will decrease obviously due to the concentration of the particle, the luminescence intensity of the CaMoO₄:Eu³⁺ nanocomposite decreases with the increase of Eu³⁺ doping amount.

We also investigated the effect of different surfactants on the luminescence pro- perties. Figure 5 is photoluminescence spectra of samples with different surfactants. It can be seen that the nonionic surfactant PEG is the best, next is the anionic surfactant sodium dodecyl sulfate (SDS), the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) is worst.