White light-emitting rare earth single-core upconversion luminescent powder material, preparation method and application thereof

Abstract

The application provides a white light-emitting rare earth mononuclear upconversion luminescent powder material and a preparation method and application thereof, and relates to the technical field of rare earth-based upconversion luminescent materials. 3+ Under the excitation of 980nm near-infrared light, upconversion luminescence appears in multiple wave bands, and through mixing of different light colors, white light emission of Er 3+ is realized without complex modification.

Description

Technical Field

[0001] This invention relates to the field of rare earth-based upconversion luminescent materials, specifically to a white luminescent rare earth mononuclear upconversion luminescent powder material, its preparation method, and its application. Background Technology

[0002] Rare-earth element-doped upconversion luminescent materials possess unique anti-Stokes luminescence, long lifetime, narrow emission, and stable energy level structure and spectral characteristics. They can effectively convert near-infrared excitation light into visible or ultraviolet light by integrating multiple low-energy photons into a single high-energy photon. These unique physicochemical properties have led to in-depth research on rare-earth upconversion materials in fields such as anti-counterfeiting, bioimaging, and security monitoring. Rare-earth upconversion materials typically consist of two parts: a matrix material and functional rare-earth ions doped within it. Fluorides, such as NaYF4 and NaGdF4, are the most common matrix materials due to their significantly low phonon energies, which greatly suppress phonon-assisted nonradiative relaxation; however, they themselves lack optical activity. The doped rare-earth ions typically include activator ions (such as Er) used to achieve visible light upconversion. 3+ ,Tm 3+ Ho 3+ (etc.) and sensitizer ions (such as Yb) that transfer the energy received by the material to the activator. 3+ and Nd 3+ Currently, the most mature upconversion luminescent material is NaYF4:Yb,Er. After being excited by 980nm near-infrared light, this material exhibits upconversion emission at 523nm, 543nm, and 653nm, and generally displays green luminescence.

[0003] However, common upconversion luminescent materials cannot overcome the limitations of light color on applications. To achieve light color modulation, it is generally necessary to further modify and optimize the materials, such as constructing core-shell structures or changing the types of dopant ions. This not only leads to resource waste and increased preparation costs, but the complex modification methods will also inevitably cause environmental pollution, thus limiting the practical application of the materials. Summary of the Invention

[0004] The purpose of this invention is to provide a white luminescent rare-earth mononuclear upconversion luminescent powder material, its preparation method and application. Under the excitation of 980nm near-infrared laser, this invention exhibits obvious upconversion emission peaks at 473nm, 543nm, 653nm and 802nm. Through the combination of different wavelengths of light, the material generally exhibits white upconversion luminescence.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a white luminescent rare-earth mononuclear upconversion luminescent powder material with the general chemical formula NaY. x Lu y F4:Yb m Er n , x+y+m+n=1, x: y=0.18~0.33: 0.45~0.60; m: n=0.17~0.20: 0.02~0.05; (x+y): (m+n)=0.63~0.93:0.19~0.25.

[0007] Preferably, the white luminescent rare-earth mononuclear upconversion luminescent powder material includes NaY. 0.25 Lu 0.53 F4:Yb 0.17 Er 0.05 NaY 0.27 Lu 0.51 F4:Yb 0.19 Er 0.03 Or NaY 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 .

[0008] This invention provides a method for preparing the white luminescent rare-earth mononuclear upconversion luminescent powder material described in the above technical solution, comprising the following steps:

[0009] Dissolve NaF in water to obtain a NaF solution;

[0010] A rare earth salt solution is obtained by mixing Y salt, Lu salt, Yb salt, Er salt, surface modifier and ethylene glycol;

[0011] The NaF solution and rare earth salt solution are mixed, and the pH of the resulting mixed solution is adjusted to 3-6. A hydrothermal reaction is then carried out to obtain upconversion nanocrystals.

[0012] The upconversion nanocrystals were dried to obtain rare-earth mononuclear upconversion luminescent powder material.

[0013] Preferably, the surface modifier includes one or more of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol.

[0014] Preferably, the molar ratio of NaF, Y salt, Lu salt, Yb salt and Er salt is 3.5-6.0: 0.18-0.33: 0.45-0.60: 0.17-0.20: 0.02-0.05.

[0015] Preferably, the ratio of the total molar amount of the Y salt, Lu salt, Yb salt and Er salt to the mass of the surface modifier is 0.8-1.2 mmol: 0.8-1.5 g.

[0016] Preferably, the concentration of the NaF solution is 0.35–0.60 mol / L; and the total concentration of rare earth salts in the rare earth salt solution is 0.041–0.059 mol / L.

[0017] Preferably, the temperature of the hydrothermal reaction is 180–220°C, and the time of the hydrothermal reaction is 12–16 hours.

[0018] Preferably, the drying temperature is 60–100°C, and the drying time is 10–16 hours.

[0019] This invention provides the application of the white luminescent rare earth mononuclear upconversion luminescent powder material described in the above technical solution or the white luminescent rare earth mononuclear upconversion luminescent powder material prepared by the preparation method described in the above technical solution in the fields of anti-counterfeiting labels, bio-imaging, or security monitoring.

[0020] This invention provides a white luminescent rare-earth mononuclear upconversion luminescent powder material. This invention achieves this by adding rare-earth elements to the matrix, thereby increasing the luminescence efficiency of the powder. 3+ Upconversion luminescence was observed in multiple wavelengths under 980nm near-infrared light excitation. Through mixing of different light colors, Er2 emission without complex modification was achieved. 3+ It emits a white glow. Unlike the common Er... 3+ The realization of green and white luminescence expands the application prospects of upconversion phosphor materials in the display field. The white-luminescent rare-earth mononuclear upconversion phosphor material provided by this invention exhibits good chemical stability and excellent stability under laser irradiation. Example results show that under 980nm near-infrared light excitation, the white-luminescent rare-earth mononuclear upconversion phosphor material provided by this invention displays bright and stable white upconversion luminescence.

[0021] This invention provides a method for preparing the white luminescent rare-earth mononuclear upconversion luminescent powder material described in the above-mentioned technical solution. The preparation method provided by this invention is simple, environmentally friendly, and saves resources and costs. This invention prepares a mononuclear white luminescent upconversion material without modification through a simple and rapid hydrothermal reaction, expanding the application range of rare-earth upconversion materials while saving costs and being environmentally friendly. Attached Figure Description

[0022] Figure 1 Scanning electron microscope image of the white luminescent rare-earth mononuclear upconversion luminescent powder material prepared in Example 1;

[0023] Figure 2 The images show the XRD patterns of the upconversion powder materials prepared in Example 1 and the comparative example.

[0024] Figure 3 The upconversion luminescence mechanism diagram of the white luminescent rare-earth mononuclear upconversion luminescent powder material prepared for the example;

[0025] Figure 4 NaY prepared in Example 1 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 Upconversion luminescence spectrum under 980nm near-infrared laser irradiation and NaY prepared in Comparative Example 1 0.546 Lu 0.234 F4:Yb 0.18 Er 0.04 Upconversion luminescence spectrum under 980nm near-infrared laser irradiation;

[0026] Figure 5 NaY prepared in Example 1 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 CIE chromaticity diagram under 980nm near-infrared laser irradiation and NaY prepared in Comparative Example 1 0.546 Lu 0.234 F4:Yb 0.18 Er 0.04 CIE chromaticity diagram under 980nm near-infrared laser illumination. Detailed Implementation

[0027] This invention provides a white luminescent rare-earth mononuclear upconversion luminescent powder material with the general chemical formula NaY. x Lu y F4:Yb m Er n , x+y+m+n=1, x: y=0.18~0.33: 0.45~0.60; m: n=0.17~0.20: 0.02~0.05; (x+y): (m+n)=0.63~0.93:0.19~0.25.

[0028] In this invention, the x:y ratio is preferably 0.20–0.28:0.50–0.58; the m:n ratio is preferably 0.175–0.192:0.028–0.045; and the (x+y):(m+n) ratio is preferably 0.70–0.86:0.203–0.237. In this invention, x represents the mole fraction of Y in the total rare earth content, y represents the mole fraction of Lu in the total rare earth content, m represents the mole fraction of Yb in the total rare earth content, and n represents the mole fraction of Er in the total rare earth content.

[0029] In this invention, the white luminescent rare-earth mononuclear upconversion luminescent powder material preferably includes NaY. 0.25 Lu 0.53 F4:Yb 0.17 Er 0.05 NaY 0.27 Lu 0.51 F4:Yb 0.19 Er 0.03 Or NaY 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 .

[0030] In this invention, the particle size range of the white luminescent rare earth mononuclear upconversion luminescent powder material is preferably 400-600 nm, more preferably 480-560 nm.

[0031] This invention provides a method for preparing the white luminescent rare-earth mononuclear upconversion luminescent powder material described in the above technical solution, comprising the following steps:

[0032] Dissolve NaF in water to obtain a NaF solution;

[0033] A rare earth salt solution is obtained by mixing Y salt, Lu salt, Yb salt, Er salt, surface modifier and ethylene glycol;

[0034] The NaF solution and rare earth salt solution are mixed, and the pH of the resulting mixed solution is adjusted to 3-6. A hydrothermal reaction is then carried out to obtain upconversion nanocrystals.

[0035] The upconversion nanocrystals were dried to obtain rare-earth mononuclear upconversion luminescent powder material.

[0036] This invention dissolves NaF in water to obtain a NaF solution. In this invention, the concentration of the NaF solution is preferably 0.35–0.60 mol / L, more preferably 0.38–0.55 mol / L. In this invention, the water is preferably deionized water. In this invention, the dissolution of NaF in water is preferably carried out under constant temperature stirring conditions; the temperature of the constant temperature stirring is preferably 18–35°C, more preferably 20–30°C, and specifically preferably room temperature; the stirring speed is preferably 800–1200 r / min, more preferably 900–1100 r / min, and most preferably 980–1000 r / min; the stirring time is preferably 1.5–3 hours, more preferably 1.8–2.5 hours, and most preferably 2 hours. In this invention, the constant temperature stirring is preferably carried out under water bath conditions. In this invention, the stirring equipment used for the constant temperature stirring is preferably a constant temperature magnetic stirrer.

[0037] This invention mixes Y salt, Lu salt, Yb salt, Er salt, a surface modifier, and ethylene glycol to obtain a rare earth salt solution. In this invention, the Y salt preferably includes one or more of YCl3, Y2(SO4)3, and Y(NO3)3; the Lu salt preferably includes one or more of LuCl3, Lu2(SO4)3, and Lu(NO3)3; the Yb salt preferably includes one or more of YbCl3, Yb2(SO4)3, and Yb(NO3)3; and the Er salt preferably includes one or more of ErCl3, Er2(SO4)3, and Er(NO3)3. In this invention, the surface modifier preferably includes one or more of polyvinylpyrrolidone (PVP), polyethylene glycol, and polyvinyl alcohol. In a specific embodiment of this invention, the surface modifier is polyvinylpyrrolidone-K30. In this invention, the molar ratio of NaF, Y salt, Lu salt, Yb salt, and Er salt is 3.5–6.0: 0.18–0.33: 0.45–0.60: 0.17–0.20: 0.02–0.05, more preferably 3.8–5.5: 0.19–0.32: 0.47–0.59: 0.175–0.198: 0.025–0.047. In this invention, the ratio of the total molar amount of Y salt, Lu salt, Yb salt, and Er salt to the mass of the surface modifier is preferably 0.8–1.2 mmol: 0.8–1.5 g, more preferably 0.85–1.15 mmol: 0.83–1.45 g. In this invention, the total concentration of rare earth salts in the rare earth salt solution is preferably 0.041 to 0.059 mol / L, more preferably 0.0432 to 0.0578 mol / L.

[0038] In this invention, the mixing of Y salt, Lu salt, Yb salt, Er salt, surface modifier, and ethylene glycol is preferably carried out under constant temperature stirring conditions; the temperature of the constant temperature stirring is preferably 35–55°C, more preferably 40–50°C; the stirring speed is preferably 800–1200 r / min, more preferably 900–1100 r / min, and most preferably 980–1000 r / min; the stirring time is preferably 1.5–3 hours, more preferably 1.8–2.5 hours, and most preferably 2 hours. In this invention, the constant temperature stirring is preferably carried out under water bath conditions. In this invention, the stirring equipment used for the constant temperature stirring is preferably a constant temperature magnetic stirrer.

[0039] After obtaining the NaF solution and the rare earth salt solution, this invention mixes the NaF solution and the rare earth salt solution, adjusts the pH of the resulting mixed solution to 3-6, and performs a hydrothermal reaction to obtain upconversion nanocrystals. In this invention, the mixing of the NaF solution and the rare earth salt solution preferably includes: adding the NaF solution to the rare earth salt solution, or adding the rare earth salt solution to the NaF solution, or directly mixing the NaF solution and the rare earth salt solution. In a specific embodiment of this invention, the NaF solution is added dropwise to the rare earth salt solution.

[0040] The present invention preferably adjusts the pH value of the resulting mixed solution to 4-5.5, more preferably 5. In the present invention, the reagent used to adjust the pH value of the resulting mixed solution is preferably one or more of an acidic solution and an alkaline solution. In the present invention, the acidic solution preferably includes a 10% hydrochloric acid solution; the alkaline solution preferably includes a 10% ammonia solution. The present invention preferably continues stirring for 30-60 minutes after adjusting the pH value of the resulting mixed solution to 3-6, more preferably for 40-50 minutes; the stirring temperature is preferably 35-50°C.

[0041] In this invention, the temperature of the hydrothermal reaction is preferably 180-220°C, more preferably 190-210°C, and most preferably 195-205°C; the time of the hydrothermal reaction is preferably 12-16 hours, more preferably 13-15 hours, and most preferably 14 hours.

[0042] Preferably, after the hydrothermal reaction, the resulting reaction system is cooled to room temperature in air, the reaction product is collected by centrifugation, and washed several times with deionized water and ethanol. In this invention, the centrifugation speed is preferably 8000–8500 r / min. Preferably, the product is washed twice with deionized water and ethanol, respectively. This invention removes impurities through washing.

[0043] After obtaining the upconversion nanocrystals, the present invention dries the upconversion nanocrystals to obtain rare-earth mononuclear upconversion luminescent powder material. In the present invention, the drying temperature is preferably 60–100°C, more preferably 70–90°C, and most preferably 75–80°C; the drying time is preferably 10–16 hours, more preferably 12–15 hours, and most preferably 13–14 hours. The present invention preferably further grinds the material after drying to obtain a white luminescent rare-earth mononuclear upconversion luminescent powder material.

[0044] This invention provides the application of the white luminescent rare-earth mononuclear upconversion luminescent powder material described in the above-described technical solution, or the white luminescent rare-earth mononuclear upconversion luminescent powder material prepared by the preparation method described in the above-described technical solution, in the fields of anti-counterfeiting labels, bio-imaging, or security monitoring. In this invention, the white luminescent rare-earth mononuclear upconversion luminescent powder material exhibits white luminescence under 980nm near-infrared excitation.

[0045] Unlike the common green luminescence of NaYF4:Yb,Er powder, this material exhibits bright white luminescence under 980nm near-infrared excitation. Furthermore, compared to other modified NaYF4 materials with tunable light color, this material presents a one-step mononuclear structure, eliminating the need for complex performance and structural optimization processes. The preparation method is simple, low-cost, and environmentally friendly, making it a promising candidate for practical applications in the display field.

[0046] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] Unless otherwise specified, the equipment used in the following embodiments and comparative examples are all conventional equipment in the art; unless otherwise specified, the reagents used are all commercially available products or prepared by conventional methods in the art; steps not described in detail in the following embodiments can be achieved by conventional experimental methods in the art.

[0048] Example 1

[0049] The white luminescent rare-earth mononuclear upconversion luminescent powder material provided in this embodiment is NaY. 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 The powder material is prepared by the following method:

[0050] Weigh out 0.0914 g of yttrium chloride (purity ≥ 99.5 wt%), 0.3072 g of lutetium chloride (purity ≥ 99.5 wt%), 0.1000 g of ytterbium chloride (purity ≥ 99.5 wt%), 0.0218 g of erbium chloride (purity ≥ 99.5 wt%), and 1.000 g of polyvinylpyrrolidone (AR) using an electronic balance with an accuracy of 0.0001 g. Place them in a clean beaker and add 40 mL of ethylene glycol (purity ≥ 99.7 wt%) to obtain a rare earth salt solution. Weigh out 0.3359 g of sodium fluoride (purity ≥ 99 wt%) and place it in another clean beaker. Add 20 mL of deionized water to obtain a sodium fluoride solution. Then place both beakers on a thermostatic magnetic stirrer and heat the rare earth salt solution in a 40°C water bath while heating the sodium fluoride solution. The mixture was stirred at room temperature, with both beakers continuously stirred at 1000 rpm for 2 hours. Then, sodium fluoride solution was added dropwise to the rare earth salt solution, and the pH of the mixed solution was adjusted to pH 4 using 5 mL of 10% hydrochloric acid solution and 5 mL of 10% ammonia solution. Stirring continued for 30 minutes. The mixed solution was then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor. The reaction system was sealed and reacted at 200°C for 14 hours. After the hydrothermal reaction, the reactor was removed and cooled to room temperature in air. The reaction product was collected by centrifugation at 8000 rpm and washed twice with deionized water and ethanol, respectively. Finally, the obtained upconversion nanocrystals were dried in an 80°C drying oven for 12 hours. After drying, the sample was ground to obtain white luminescent rare earth mononuclear upconversion luminescent powder material.

[0051] Example 2

[0052] The white luminescent rare-earth mononuclear upconversion luminescent powder material provided in this embodiment is NaY. 0.25 Lu 0.53 F4:Yb 0.17 Er 0.05 The powder material is prepared by the following method:

[0053] Weigh out 0.0978 g of yttrium chloride (purity ≥ 99.5 wt%), 0.2982 g of lutetium chloride (purity ≥ 99.5 wt%), 0.0950 g of ytterbium chloride (purity ≥ 99.5 wt%), 0.0273 g of erbium chloride (purity ≥ 99.5 wt%), and 1.100 g of polyvinylpyrrolidone (AR) using an electronic balance with an accuracy of 0.0001 g. Place them in a clean beaker and add 40 mL of ethylene glycol (purity ≥ 99.7 wt%) to obtain a rare earth salt solution. Weigh out 0.3359 g of sodium fluoride (purity ≥ 99 wt%) and place it in another clean beaker. Add 20 mL of deionized water to obtain a sodium fluoride solution. Then place both beakers on a thermostatic magnetic stirrer and heat the rare earth salt solution in a 40°C water bath while heating the sodium fluoride solution. The mixture was stirred at room temperature, with both beakers continuously stirred at 1000 rpm for 2 hours. Then, sodium fluoride solution was added dropwise to the rare earth salt solution, and the pH of the mixed solution was adjusted to pH 5 using 5 mL of 10% hydrochloric acid solution and 5 mL of 10% ammonia solution. Stirring continued for 30 minutes. The mixed solution was then transferred to a PTFE-lined stainless steel high-pressure reactor. The reaction system was sealed and reacted at 205°C for 15 hours. After the hydrothermal reaction, the reactor was removed and cooled to room temperature in air. The reaction product was collected by centrifugation at 8500 rpm and washed twice with deionized water and ethanol, respectively. Finally, the obtained upconversion nanocrystals were dried in a 90°C drying oven for 11 hours. After drying, the sample was ground to obtain white luminescent rare earth mononuclear upconversion luminescent powder material.

[0054] Example 3

[0055] The white luminescent rare-earth mononuclear upconversion luminescent powder material provided in this embodiment is NaY. 0.27 Lu 0.51 F4:Yb 0.19 Er 0.03 The powder material is prepared by the following method:

[0056] Weigh out 0.1056 g of yttrium chloride (purity ≥ 99.5 wt%), 0.2870 g of lutetium chloride (purity ≥ 99.5 wt%), 0.1062 g of ytterbium chloride (purity ≥ 99.5 wt%), 0.0164 g of erbium chloride (purity ≥ 99.5 wt%), and 0.950 g of polyvinylpyrrolidone (AR) using an electronic balance with an accuracy of 0.0001 g. Place them in a clean beaker and add 40 mL of ethylene glycol (purity ≥ 99.7 wt%) to obtain a rare earth salt solution. Weigh out 0.3359 g of sodium fluoride (purity ≥ 99 wt%) and place it in another clean beaker. Add 20 mL of deionized water to obtain a sodium fluoride solution. Then place both beakers on a thermostatic magnetic stirrer and heat the rare earth salt solution in a 43°C water bath while heating the sodium fluoride solution. The mixture was stirred at room temperature, with both beakers continuously stirred at 980 rpm for 2.5 hours. Sodium fluoride solution was then added dropwise to the rare earth salt solution. The pH of the mixed solution was adjusted to pH 4 using 5 mL of 10% hydrochloric acid solution and 5 mL of 10% ammonia solution, and stirring continued for 30 minutes. The mixed solution was then transferred to a PTFE-lined stainless steel high-pressure reactor. The reaction system was sealed and reacted at 195°C for 13 hours. After the hydrothermal reaction, the reactor was removed and cooled to room temperature in air. The reaction product was collected by centrifugation at 8500 rpm and washed twice with deionized water and ethanol, respectively. Finally, the obtained upconversion nanocrystals were dried in a 75°C drying oven for 13 hours. After drying, the sample was ground to obtain white luminescent rare earth mononuclear upconversion luminescent powder material.

[0057] Comparative Example 1

[0058] The upconversion powder material provided in this comparative example is NaY. 0.546 Lu 0.234 F4:Yb 0.18 Er 0.04 The powder material is prepared by the following method:

[0059] Weigh out 0.2132 g of yttrium chloride (purity ≥ 99.5 wt%), 0.1317 g of lutetium chloride (purity ≥ 99.5 wt%), 0.1000 g of ytterbium chloride (purity ≥ 99.5 wt%), 0.0218 g of erbium chloride (purity ≥ 99.5 wt%), and 1.000 g of polyvinylpyrrolidone (AR) using an electronic balance with an accuracy of 0.0001 g. Place them in a clean beaker and add 40 mL of ethylene glycol (purity ≥ 99.7 wt%) to obtain a rare earth salt solution. Weigh out 0.3359 g of sodium fluoride (purity ≥ 99 wt%) and place it in another clean beaker. Add 20 mL of deionized water to obtain a sodium fluoride solution. Then place both beakers on a thermostatic magnetic stirrer and heat the rare earth salt solutions in a 40°C water bath. Sodium fluoride solution was stirred at room temperature, with both beakers continuously stirred at 1000 rpm for 2 hours. Then, sodium fluoride solution was added dropwise to the rare earth salt solution, and the pH of the mixed solution was adjusted to pH 4 using 5 mL of 10% hydrochloric acid solution and 5 mL of 10% ammonia solution. Stirring continued for 30 minutes. The mixed solution was then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor. The reaction system was sealed and reacted at 200°C for 14 hours. After the hydrothermal reaction, the reactor was removed and cooled to room temperature in air. The reaction product was collected by centrifugation at 8000 rpm and washed twice with deionized water and ethanol, respectively. Finally, the obtained upconversion nanocrystals were dried in an 80°C drying oven for 12 hours. After drying, the sample was ground to obtain upconversion powder material.

[0060] Comparative Example 2

[0061] The upconversion powder material provided in this comparative example is NaY. 0.39 Lu 0.39 F4:Yb 0.18 Er 0.04 The powder material is prepared by the following method:

[0062] Weigh out 0.1523g of yttrium chloride (purity ≥ 99.5wt%), 0.2194g of lutetium chloride (purity ≥ 99.5wt%), 0.1000g of ytterbium chloride (purity ≥ 99.5wt%), 0.0218g of erbium chloride (purity ≥ 99.5wt%), and 1.000g of polyvinylpyrrolidone (AR) using an electronic balance with an accuracy of 0.0001g. Place them in a clean beaker and add 40mL of ethylene glycol (purity ≥ 99.7wt%) to obtain a rare earth salt solution. Weigh out 0.3359g of sodium fluoride (purity ≥ 99wt%) and place it in another clean beaker. Add 20mL of deionized water to obtain a sodium fluoride solution. Then place both beakers on a thermostatic magnetic stirrer and heat the rare earth salt solutions in a 40°C water bath. Sodium fluoride solution was stirred at room temperature, with both beakers continuously stirred at 1000 rpm for 2 hours. Then, sodium fluoride solution was added dropwise to the rare earth salt solution, and the pH of the mixed solution was adjusted to pH 4 using 5 mL of 10% hydrochloric acid solution and 5 mL of 10% ammonia solution. Stirring continued for 30 minutes. The mixed solution was then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor. The reaction system was sealed and reacted at 200°C for 14 hours. After the hydrothermal reaction, the reactor was removed and cooled to room temperature in air. The reaction product was collected by centrifugation at 8000 rpm and washed twice with deionized water and ethanol, respectively. Finally, the obtained upconversion nanocrystals were dried in an 80°C drying oven for 12 hours. After drying, the sample was ground to obtain upconversion powder material.

[0063] Comparative Example 3

[0064] The upconversion powder material provided in this comparative example is NaY. 0.78 F4:Yb 0.18 Er 0.04 The powder material is prepared by the following method:

[0065] Weigh out 0.3046 g of yttrium chloride (purity ≥ 99.5 wt%), 0.1000 g of ytterbium chloride (purity ≥ 99.5 wt%), 0.0218 g of erbium chloride (purity ≥ 99.5 wt%), and 1.000 g of polyvinylpyrrolidone (AR) using an electronic balance with an accuracy of 0.0001 g. Place them in a clean beaker and add 40 mL of ethylene glycol (purity ≥ 99.7 wt%) to obtain a rare earth salt solution. Weigh out 0.3359 g of sodium fluoride (purity ≥ 99 wt%) and place it in another clean beaker. Add 20 mL of deionized water to obtain a sodium fluoride solution. Then place both beakers on a thermostatic magnetic stirrer. Heat the rare earth salt solution in a 40°C water bath and stir the sodium fluoride solution at room temperature. Each beaker was continuously stirred at 1000 r / min for 2 hours. Then, sodium fluoride solution was added dropwise to the rare earth salt solution. The pH of the mixed solution was adjusted to pH=4 using 5 mL of 10% hydrochloric acid solution and 5 mL of 10% ammonia solution, and stirring continued for 30 minutes. The mixed solution was then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor. The reaction system was sealed and reacted at 200℃ for 14 hours. After the hydrothermal reaction, the reactor was removed and cooled to room temperature in air. The reaction product was collected by centrifugation at 8000 r / min and washed twice with deionized water and ethanol, respectively. Finally, the obtained upconversion nanocrystals were dried in an 80℃ drying oven for 12 hours. After the sample was dried, it was ground to obtain upconversion powder material.

[0066] Comparative Example 4

[0067] The upconversion powder material provided in this comparative example is NaLu. 0.78 F4:Yb 0.18 Er 0.04 The powder material is prepared by the following method:

[0068] Weigh out 0.4389 g of lutetium chloride (purity ≥ 99.5 wt%), 0.1000 g of ytterbium chloride (purity ≥ 99.5 wt%), 0.0218 g of erbium chloride (purity ≥ 99.5 wt%), and 1.000 g of polyvinylpyrrolidone (AR) using an electronic balance with an accuracy of 0.0001 g. Place them in a clean beaker and add 40 mL of ethylene glycol (purity ≥ 99.7 wt%) to obtain a rare earth salt solution. Weigh out 0.3359 g of sodium fluoride (purity ≥ 99 wt%) and place it in another clean beaker. Add 20 mL of deionized water to obtain a sodium fluoride solution. Then place both beakers on a thermostatic magnetic stirrer. Heat the rare earth salt solution in a 40°C water bath and stir the sodium fluoride solution at room temperature. Each beaker was continuously stirred at 1000 r / min for 2 hours. Then, sodium fluoride solution was added dropwise to the rare earth salt solution. The pH of the mixed solution was adjusted to pH=4 using 5 mL of 10% hydrochloric acid solution and 5 mL of 10% ammonia solution, and stirring continued for 30 minutes. The mixed solution was then transferred to a polytetrafluoroethylene-lined stainless steel high-pressure reactor. The reaction system was sealed and reacted at 200℃ for 14 hours. After the hydrothermal reaction, the reactor was removed and cooled to room temperature in air. The reaction product was collected by centrifugation at 8000 r / min and washed twice with deionized water and ethanol, respectively. Finally, the obtained upconversion nanocrystals were dried in an 80℃ drying oven for 12 hours. After the sample was dried, it was ground to obtain upconversion powder material.

[0069] Test case

[0070] (1) Observation of NaY prepared in Example 1 using scanning electron microscopy 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 The morphological structure, such as Figure 1 As shown, by Figure 1 As can be seen, the sample exhibits a smooth, rod-like morphology. The microstructures of the remaining examples and comparative examples are similar. Figure 1 similar.

[0071] (2) Characterization of the crystallization diffraction peaks of the upconversion luminescent powder materials prepared in the comparative example and Example 1 as follows: Figure 2 As shown. By Figure 2 It can be seen that the relative intensity and position of the main diffraction peaks of the sample changed slightly with the change of element type and ratio, but the overall hexagonal phase crystal form remained consistent. This indicates that element substitution and ratio adjustment do not have a significant impact on the crystal form of the sample.

[0072] (3) The luminescence mechanism diagram of the white luminescent rare-earth mononuclear upconversion luminescent powder material prepared in the embodiments of the present invention is shown below. Figure 3 As shown. Under 980nm infrared excitation, Yb 3+ 4f layer electrons from 2 F 7 / 2 The ground state energy level is excited to 2 F 5 / 2 The excited state energy levels. From Yb 3+ To Er 3+ Two consecutive energy transfers successively filled Er 3+ of 4 I 11 / 2 and 4 F 7 / 2 Energy level. Er 3+ from 4 F 7 / 2 arrive 2 H 11 / 2 and 4 S 9 / 2 The transition occurs through a non-radiative energy decay process. From 2 H 11 / 2 and 4 S 9 / 2 to the ground state 4 I 15 / 2 The energy levels correspond to green light emission at 523nm and 543nm, respectively. The orange-red emission near 653nm is due to... 4 F 9 / 2 and 4 I 15 / 2 The transitions between these wavelengths. The blue and red light emission of the material at 473 nm and 802 nm correspond to Er and [other wavelengths, respectively]. 3+ of 4 F 7 / 2 - 4 I 15 / 2 and 4 I 9 / 2 - 4 I 15 / 2 Energy level transition.

[0073] (4) NaY prepared in Example 1 of this invention 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 The upconversion luminescence spectrum under 980nm near-infrared laser irradiation is as follows: Figure 4 As shown in Figure a, the material exhibits significant upconversion emission peaks at 473 nm, 543 nm, 653 nm, and 802 nm. The emission spectra of the other embodiments are similar to those of the material. Figure 4 Similar to a; NaY prepared in Comparative Example 1 0.546 Lu 0.234 F4:Yb 0.18 Er 0.04The upconversion luminescence spectrum under 980nm near-infrared laser irradiation is as follows: Figure 4 As shown in b, the number of main emission peaks and the relative intensity between emission peaks of the material are related to... Figure 4 There is a significant difference compared to a; the emission spectra of the other comparative examples are similar. Figure 4 Similar to b.

[0074] (5) NaY prepared in Example 1 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04 The CIE chromaticity diagram under 980nm near-infrared laser illumination is as follows: Figure 5 As shown in Figure a, under the combined effect of different colors of light in various wavelengths, the emission color coordinates of the material are (0.2390, 0.3972), actually exhibiting white emission. The emission spectra of the other embodiments are similar to those of the material. Figure 5 Similar to a; NaY prepared in Comparative Example 1 0.546 Lu 0.234 F4:Yb 0.18 Er 0.04 The CIE chromaticity diagram under 980nm near-infrared laser illumination is as follows: Figure 5 As shown in b, the emission color coordinates of the material are... Figure 5 Compared to a, it shows a significant difference, exhibiting green luminescence; the luminescence spectra of the remaining comparative examples are different. Figure 5 Similar to b.

[0075] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A white luminescent rare-earth mononuclear upconversion luminescent powder material, characterized in that, The chemical formula of the white luminescent rare-earth mononuclear upconversion luminescent powder material is NaY. 0.25 Lu 0.53 F4:Yb 0.17 Er 0.05 NaY 0.27 Lu 0.51 F4:Yb 0.19 Er 0.03 Or NaY 0.234 Lu 0.546 F4:Yb 0.18 Er 0.04； The preparation method of the white luminescent rare-earth mononuclear upconversion luminescent powder material includes the following steps: Dissolve NaF in water to obtain a NaF solution; A rare earth salt solution is obtained by mixing Y salt, Lu salt, Yb salt, Er salt, polyvinylpyrrolidone, and ethylene glycol. The NaF solution and rare earth salt solution are mixed, and the pH of the resulting mixed solution is adjusted to 3-6. A hydrothermal reaction is then carried out to obtain upconversion nanocrystals. The upconversion nanocrystals were dried to obtain rare earth mononuclear upconversion luminescent powder material; The total molar amount of the Y salt, Lu salt, Yb salt and Er salt to the mass ratio of polyvinylpyrrolidone is 0.8~1.2 mmol: 0.8~1.5 g; The concentration of the NaF solution is 0.35~0.60 mol / L; the total concentration of rare earth salts in the rare earth salt solution is 0.041~0.059 mol / L; The hydrothermal reaction temperature is 180~220℃, and the hydrothermal reaction time is 12~16 hours.

2. The preparation method of the white luminescent rare-earth mononuclear upconversion luminescent powder material according to claim 1, comprising the following steps: Dissolve NaF in water to obtain a NaF solution; A rare earth salt solution is obtained by mixing Y salt, Lu salt, Yb salt, Er salt, polyvinylpyrrolidone, and ethylene glycol. The NaF solution and rare earth salt solution are mixed, and the pH of the resulting mixed solution is adjusted to 3-6. A hydrothermal reaction is then carried out to obtain upconversion nanocrystals. The upconversion nanocrystals were dried to obtain rare earth mononuclear upconversion luminescent powder material; The total molar amount of the Y salt, Lu salt, Yb salt and Er salt to the mass ratio of polyvinylpyrrolidone is 0.8~1.2 mmol: 0.8~1.5 g; The concentration of the NaF solution is 0.35~0.60 mol / L; the total concentration of rare earth salts in the rare earth salt solution is 0.041~0.059 mol / L; The hydrothermal reaction temperature is 180~220℃, and the hydrothermal reaction time is 12~16 hours.

3. The preparation method according to claim 2, characterized in that, The drying temperature is 60~100℃, and the drying time is 10~16 hours.

4. The application of the white luminescent rare earth mononuclear upconversion luminescent powder material according to claim 1 or the white luminescent rare earth mononuclear upconversion luminescent powder material prepared by the preparation method according to any one of claims 2 to 3 in the fields of anti-counterfeiting labels, bio-imaging or security monitoring.

Images