CN106520118A - A Ho3+/Yb3+/Li+ co-doped zinc oxide up-conversion luminescent material and its preparation method - Google Patents

Abstract

The present invention provides a Ho<3+>/Yb<3+>/Li<+> codoped zinc oxide upconversion luminescence material and a preparation method. ZnO is used as a matrix, and rare earth elements Ho<3+> and Yb<3+> and Li<+> are used as doping ions, and the composition formula of the material is Zn[1-x-y-z]Ho[x]Yb[y]Li[z]O. The zinc oxide upconversion luminescence material with high luminescent intensity is prepared through codoping of Ho<3+>/Yb<3+>/Li<+>, the synthesis process is simple, the repeatability is high, employed materials are environmentally friendly, safe and nontoxic, and industrialized production is easy to realize. At the same time, the upconversion luminescence intensity of zinc oxide can be obviously improved by changing Li<+> doping concentration, and can be used to display, illumination, laser anticouterfeit, etc.

Description

A Ho3+/Yb3+/Li+ co-doped zinc oxide up-conversion luminescent material and its preparation method

technical field

The invention belongs to the technical field of up-conversion luminescent materials, and relates to a Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material.

Background technique

In recent years, rare-earth-doped upconversion luminescent materials have attracted great attention due to their wide application in 3D stereoscopic display, laser anti-counterfeiting, bioluminescence labeling and short-wavelength lasers. But generally speaking, the up-conversion luminous efficiency is still relatively low. At present, some commonly used materials with better luminescent properties still have some problems in terms of thermal and chemical stability, mechanical strength, etc., which brings difficulties to practical applications. Therefore, finding new host materials with high conversion efficiency and excellent physical and chemical properties has become one of the current research hotspots of upconversion luminescent materials.

Zinc oxide (ZnO), as a new type of direct wide bandgap semiconductor material, has a bandgap width of 3.37eV at room temperature, a high exciton binding energy (60meV), and strong absorption in the ultraviolet region. It has stable chemical properties and low phonon energy (437cm ^-1 ), which makes it possible to become an ideal up-conversion luminescent host material. But so far, the up-conversion luminous efficiency of rare earth-doped ZnO materials is still relatively low. One of the reasons is that it is generally difficult for rare earth ions to enter the ZnO lattice in the form of replacing Zn ²⁺ sites. This is because the radius of trivalent rare earth ions is much larger than that of Zn ²⁺ ions, and the charges of the two do not match.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material and its preparation method, which solves the complex preparation process of the prior art zinc oxide up-conversion luminescent material, The technical problem of low luminous intensity and impossibility of high-concentration doping.

The technical scheme adopted in the present invention is:

Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material, with ZnO as the matrix, rare earth elements Ho ³⁺ and Yb ^{3 +} , and Li ⁺ ions as dopant ions, and its composition is, Zn _1-xy Ho _x Yb _y Li _z O, wherein 8.5 mol% ≤ x+y+z ≤ 15.5 mol%.

Preferably, the Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material is composed of Zn _1-xy Ho _x Yb _y Li _z O, where x=1mol%, y=7.5mol%, z ≤7mol%.

Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material preparation method, comprising the following steps:

Step 1, dissolving zinc acetate or zinc nitrate in deionized water, stirring until the zinc acetate or zinc nitrate is fully dissolved to obtain a zinc salt solution;

Step 2, mix Ho ₂ O ₃ , Yb ₂ O ₃ and Li ₂ CO ₃ and dissolve in dilute nitric acid or dilute hydrochloric acid solution, heat and stir at 40°C to 60°C until fully reacted and evaporate the solution to dryness at 50°C to 70°C get powdered substance;

Step 3, dissolving the powder obtained in Step 2 in water, stirring until clarified, adding dropwise the zinc salt solution obtained in Step 1, and stirring until clarified to obtain a solution;

Step 4, adding triethanolamine or monoethanolamine dropwise to the solution obtained in Step 3, until the white flocculent precipitate that appeared at the beginning is completely dissolved, and a colorless transparent solution is obtained;

Step five, adding polyethylene glycol-600 or polyethylene glycol-400 to the solution obtained in step four, stirring and mixing;

Step 6, transfer the solution obtained in step 5 into an autoclave, react at 140°C-180°C for 2-6 hours, and wait for the autoclave to cool to room temperature to obtain a precipitate;

Step 7: The precipitate obtained in step 6 is centrifuged, washed, dried at 60°C-80°C for 2-4 hours and ground to obtain a white powder, and the white powder is annealed at 550°C-750°C for 2-4 hours for annealing treatment.

The beneficial effects of the present invention are

1. Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doping of the present invention prepares zinc oxide up-conversion luminescent materials with high luminous intensity, the synthesis process is simple, the repeatability is high, the materials used are environmentally friendly, safe and non-toxic, and easy to realize industrialized production.

2. The zinc oxide up-conversion luminescent material prepared by the present invention has strong luminous intensity and can be used in display, lighting, laser anti-counterfeiting and other aspects.

3. The preparation method of Ho ³⁺ /Yb ³⁺ /Li ⁺ zinc oxide up-conversion luminescent material provided by the present invention realizes the high-concentration doping of Ho ³⁺ /Yb ^{3 +} /Li ⁺ , by changing the doping of Li ⁺ The impurity concentration can significantly improve the upconversion luminescence intensity of ZnO.

Description of drawings

Figure 1 is the XRD pattern of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped nano-ZnO;

Figure 2 is a SEM image of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped nano-ZnO;

Figure 3(a) is the up-conversion emission spectrum of samples with different Li ⁺ doping concentrations, and (b) is the relationship between the integrated emission intensity of red and green light as a function of Li ⁺ doping concentration;

detailed description

Yb ³⁺ is used as a sensitizing ion, which can greatly improve the absorption efficiency of the pump light by the active ion Ho ³⁺ , so the present invention adopts the Ho ³⁺ /Yb ³⁺ double doping method, and after doping Li ⁺ ions, it emits light The strength is obviously enhanced again, probably because the Li ⁺ ions are very small, and it is easier to enter the ZnO lattice near the Ho ³⁺ ions, and change the local crystal field symmetry of the Ho ³⁺ ions through the charge interaction, which is suitable for the 4f electronic transition, thus enhance the up-conversion luminescence.

The present invention will be described in detail below in conjunction with accompanying drawings and specific embodiments. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations done on the basis of the technical solutions of the present application all fall within the scope of protection of the present invention.

Example 1

The invention provides a Ho ³⁺ , Yb ³⁺ , Li ⁺ co-doped ZnO up-conversion luminescent material, the chemical composition is Zn _{1-xy- z} Ho _x Yb _y Li _z O, wherein Ho ³⁺ is an active ion, Yb ³⁺ is a sensitizer, x is the molar percentage of Ho ³⁺ doping, y is the molar percentage of Yb ³⁺ doping, z is the molar percentage of Li ⁺ doping, and x+y+z=15.5mol%, The preparation steps are as follows:

Step 1, prepare a zinc acetate solution, take 6.585g of Zn(Ac) ₂ , dissolve it in 30ml of deionized water, and stir until it is fully dissolved into a colorless and transparent solution ①.

Step 2, preparing rare earth nitrate and lithium nitrate. Weigh the corresponding rare earth oxides (Ho ₂ O ₃ , Yb ₂ O ₃ ) and lithium carbonate in proportion Zn:Ho:Yb:Li=0.915:0.01:0.075:0.07, mix them uniformly and dissolve them in dilute nitric acid solution. Heat and stir at 40°C to 60°C, and evaporate the solution to dryness at 50°C to 70°C after fully reacting.

Step 3: Dissolve the powder obtained above in 10ml of deionized water, stir until clear, add solution ① dropwise, and stir until clear to obtain solution ②.

Step 4: Weigh 20ml of triethanolamine and add it dropwise to the ② solution. Initially, a white flocculent precipitate appears. Continue to add until the white precipitate is completely dissolved, and finally a colorless and transparent solution ③ is obtained.

Step 5, measure 5ml of polyethylene glycol-600, add it into the solution of ③, stir well to make it evenly mixed.

Step 6, transfer the mixture solution obtained above into a 100ml autoclave, and react at 140° C. to 180° C. for 2 to 6 hours.

Step 7, after the reaction is over, take out the reactor and cool it down to room temperature. Centrifuge the obtained precipitate, wash it repeatedly, dry it at 60°C-80°C for 2-4 hours, take it out and grind it after drying. Finally, the white powder obtained above is annealed at 550° C. to 750° C. for 2 to 4 hours.

Example 2

The chemical composition and preparation method of the Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped ZnO up-conversion luminescent material in this example are the same as those in Example 1, except that x+y+z=13.5mol%, where x is 1 mol%, y is 7.5 mol%, and z is 5 mol%.

Example 3

The chemical composition and preparation method of the Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped ZnO up-conversion luminescent material in this example are the same as those in Example 1, except that x+y+z=11.5 mol%.

Example 4

The chemical composition and preparation method of the Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped ZnO up-conversion luminescent material in this example are the same as those in Example 1, except that x+y+z=9.5 mol%.

Example 5

The chemical composition and preparation method of the Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped ZnO up-conversion luminescent material in this example are the same as those in Example 1, except that x+y=8.5mol%, z=0.

Carry out X-ray powder diffraction pattern analysis, SEM picture and the up-conversion emission spectrum that the sample obtains under 980nmLD excitation to the sample that above embodiment makes and analyze, and the result is as follows:

Fig. 1 is the X-ray powder diffraction pattern of embodiment 1 sample Zn _0.915 Ho _0.01 Yb _0.075 Li _0.07 O and embodiment 5 sample Zn _0.915 Ho _0.01 Yb _0.075 Li ₀ O, and the bottom solid line is the standard PDF of ZnO (JCPDS 36 -1451) spectrum. It can be seen from Figure 1 that the diffraction peaks of all samples are sharp, the main crystal phase is ZnO with hexagonal wurtzite structure, and the crystal quality is good. A small amount of peaks of Yb ₂ O ₃ and LiYbO ₂ also appeared due to the high doping amount of Li ⁺ and Yb ³⁺ . And when the Li ⁺ doping amount is 7mol%, the diffraction peaks are sharper, indicating that the grain size is further increased.

Fig. 2 is a SEM image of the sample Zn _0.845 Ho _0.01 Yb _0.075 Li _0.07 O. It can be seen from Fig. 2 that the obtained sample is a scattered flower-cone structure composed of nanorods, the surface is not smooth, and there are some small nanoparticles, which may be caused by the distribution of some impurity phases on the surface.

Fig. 3(a) is the up-conversion emission spectrum obtained under 980nm LD excitation of the sample prepared according to the protocol of the example. After doping Li ⁺ , the up-conversion fluorescence of the sample has changed a lot, which is mainly manifested in: with the increase of Li ⁺ doping amount, the luminous intensity is obviously enhanced, especially the green light intensity is greatly increased. When the Li ⁺ doping amount reaches 5 mol% (Example 2), the up-conversion luminous intensity reaches the maximum value, and then the luminous intensity begins to decrease with the doping of Li ⁺ . Figure 3(b) shows the relationship between the integrated intensity ratio of red and green light as a function of Li ⁺ ion concentration. It can be seen from the figure that the integral ratio of red and green light gradually decreases with the increase of Li ⁺ doping concentration, and tends to be stable.

Claims (9)

1. Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material, with ZnO as the matrix, characterized in that Ho ³⁺ , Yb ³⁺ and Li ⁺ are co-doped as doping ions. 2. The Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material according to claim 1, characterized in that, the Ho ^{3 +} /Yb ³⁺ /Li ⁺ co-doped zinc oxide Convert the luminescent material composition into, Zn _1-xy Ho _x Yb _y Li _z O, wherein 8.5 mol%≤x+y+z≤15.5 mol%. 3. The Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material according to claim 2, characterized in that, the Ho ^{3 +} /Yb ³⁺ /Li ⁺ co-doped zinc oxide Convert the luminescent material composition into, Zn _1-xy Ho _x Yb _y Li _z O, wherein x=1 mol%, y=7.5 mol%, z≤7 mol%. 4. The preparation method of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material according to any one of claims 1 to 3, comprising the following steps: Step 1, dissolving zinc acetate or zinc nitrate in deionized water, stirring until the zinc acetate or zinc nitrate is fully dissolved to obtain a zinc salt solution; It is characterized in that, Step 2, mix Ho ₂ O ₃ , Yb ₂ O ₃ and Li ₂ CO ₃ and dissolve in dilute nitric acid or dilute hydrochloric acid solution, heat and stir until fully reacted, evaporate the solution to dryness to obtain a powder substance; Step 3, dissolving the powder substance obtained in Step 2 in water, stirring until clarified, adding the zinc salt solution obtained in Step 1 dropwise, and stirring until a clear solution; Step 4, adding triethanolamine or monoethanolamine dropwise to the solution obtained in Step 3, until the white flocculent precipitate that appeared at the beginning is completely dissolved, and a colorless transparent solution is obtained; Step five, adding polyethylene glycol-600 or polyethylene glycol-400 to the solution obtained in step four, stirring and mixing; In step 6, the solution obtained in step 5 is transferred to an autoclave for reaction, and the autoclave is cooled to room temperature to obtain a precipitate; In step seven, the precipitate obtained in step six is centrifuged, washed, dried and ground to obtain a white powder, and the white powder is annealed. 5. The preparation method of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material according to claim 4, characterized in that the heating and stirring temperature in the second step is 40°C-60°C. 6. The preparation method of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material as claimed in claim 4, characterized in that the evaporation temperature of the solution in the second step is 50°C to 70°C . 7. The preparation method of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material according to claim 4, characterized in that the reaction condition of the high-pressure reactor in the step 6 is 140°C-180°C Reaction 2 ~ 6h. 8. The preparation method of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material as claimed in claim 4, characterized in that, the drying condition of step 7 is 60°C to 80°C for 2- 4h. 9. The preparation method of Ho ³⁺ /Yb ³⁺ /Li ⁺ co-doped zinc oxide up-conversion luminescent material according to claim 4, characterized in that the annealing condition in the step 7 is 550°C-750°C annealing 2- 4h.