Method for preparing color-adjustable fluorescent powder from Er < 3 + > / Sm < 3 + > co-doped BaFCl

Abstract

The invention provides a method for preparing color-adjustable fluorescent powder from Er < 3 + > / Sm < 3 + > co-doped BaFCl, belongs to the technical field of luminescent materials in the field of materials, and solves the technical problem that rare earth ion doped nano materials are unstable in luminescent color regulation and luminescence performance. Technical problems are solved. According to the technical scheme, color-adjustable fluorescent powder is prepared based on Er < 3 + > and Sm < 3 + > ion co-doped BaFCl nanoparticles, and color tuning from yellow green to orange red is achieved by changing the Sm < 3 + > doping concentration. The method has the beneficial effect that the color tuning from yellow green to orange red is realized by changing the doping concentration of Sm < 3 + >.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent materials in the field of materials, specifically to a technology for preparing phosphors by doping nanoparticles with rare earth ions and analysis of the luminescent properties of luminescent materials, and in particular to a method for preparing color-adjustable phosphors by co-doping BaFCl with Er3+ / Sm3+. Background Art

[0002] With the development of science and technology, the potential of rare earth elements is gradually being explored. Rare earth elements (Ln) usually refer to lanthanide elements (such as lanthanum (La), neodymium (Nd), samarium (Sm), terbium (Tb), dysprosium (Dy), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.) and yttrium (Y), which exhibit excellent optical properties due to their unique electronic structure. Rare earth ions have high spectral purity and stable luminescence characteristics, and are widely used in fluorescent materials, lasers, optoelectronic displays and bioimaging. These elements have gradually become an important force in promoting scientific and technological progress and industrial upgrading with their unique properties and broad application prospects. Rare earth ion-doped nanoparticles can generally be divided into single rare earth ion doping and co-doping with multiple rare earth ions, which have different characteristics:

[0003] 1. Single rare earth ion doping: Single rare earth ion doping has the characteristics of (1) clear luminescence characteristics (single rare earth ion doping usually produces luminescence of a specific wavelength, which makes its luminescence characteristics very clear); (2) simple energy transfer mechanism (since there is only one rare earth ion, the energy transfer mechanism is relatively simple and mainly depends on the characteristic transition of the ion); (3) high quantum efficiency (because there is no competition or interference from other ions, single doped materials usually have high quantum efficiency); (4) optimization of doping concentration (luminescence intensity can be optimized by adjusting the doping concentration, but too high a concentration may lead to concentration quenching); (5) simple and clear application (single doped materials are usually used for specific applications, such as red phosphors, lasers, etc., which facilitates application development in specific fields). This also makes it widely used. In order to achieve the up-conversion effect of multi-color orthogonal luminescence and at the same time regulate the synthesis complexity and mutual interference problems caused by multiple doping ions, Er is used. 3+ The mechanism of different colors of light emission due to the special energy level transition of Er was designed. 3+Single doped dual-excitation upconversion nanoparticles were used as activators, and a three-layer structure of nanoparticles was constructed by thermal decomposition. The prepared nanoparticles have uniform size, stable structure and good dispersibility. This unique dual-excitation nanoparticle can achieve orthogonal luminescence of red and green respectively under the action of two excitation light sources of 980nm and 808nm, and the luminescence properties of each do not interfere with each other, maintaining a high degree of independence. In addition, a new near-infrared luminescent material Mg2-xSnO4∶xCr was synthesized by high-temperature solid-phase method. 3+ The structure of the sample was characterized by X-ray powder diffractometer. The results showed that the phosphor had a single spinel structure and was doped with Cr. 3+ The ions did not change its crystal structure. The luminescence characteristics of the phosphor were studied in depth using fluorescence spectroscopy and fluorescence decay spectroscopy. The results showed that the fluorescence lifetime of the sample increased with the increase of Cr 3+ The doping concentration gradually decreases with the increase of Cr 3+ There is energy transfer between them.

[0004] 2. Co-doping of multiple rare earth ions: The characteristics of co-doping of multiple rare earth ions include (1) luminescence color adjustment (co-doping can adjust the luminescence color by combining different rare earth ions); (2) energy transfer enhancement (energy transfer between different rare earth ions can significantly enhance the luminescence efficiency, especially in the co-doping system, energy transfer can improve the luminescence intensity); (3) wide-spectrum luminescence (co-doped materials can emit light in a wider spectral range, increasing the flexibility of application, such as for full-color light-emitting devices); (4) complex luminescence mechanism (the luminescence mechanism of co-doping is relatively complex, involving the energy level interaction and energy transfer of multiple ions, and in-depth research may be required to understand its luminescence behavior); (5) wide application (co-doped materials are more widely used and can be used in optoelectronic devices, display systems, biological imaging and other fields, with greater market potential). This makes it a popular research object at this stage. Tb co-doped in silicate and borosilicate glass 3+ and Sm 3+ The photoluminescent properties of ions. Under ultraviolet light, these glass materials emit a combination of green and orange-red light waves, which together form a white light effect. The intensity ratio of orange-red light to green light can be measured by measuring the intensity of Sm 3+ The ion concentration can be adjusted and the glass matrix composition can be changed to achieve flexible control. 3+ and Sm 3+ The Er-containing ZnS semiconductor quantum dots (QDs) were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). 3+ and Sm 3+existence.

[0005] Nanoparticles doped with rare earth ions show excellent performance in luminescence and have become an important raw material for preparing phosphors. More researchers are committed to the research of obtaining high-performance phosphors based on rare earth ion doping. Rare earth ion-doped phosphors have the advantages of rich spectral lines, good optical stability, long luminescence lifetime, good chemical stability and low biological toxicity. A large number of energy level transitions can produce rich and sharp luminescence spectrum lines, which can cover a wide range from ultraviolet to near infrared. It has been applied to many fields such as high-power lasers, solar cells, color displays, light-emitting diodes, optical anti-counterfeiting, biomedical imaging, etc.

[0006] With the continuous progress and innovation of energy-saving lighting technology, semiconductor lighting technology with light-emitting diodes (LEDs) as the core has developed rapidly. In LEDs, phosphors are key luminescent materials, and their performance directly determines the luminous efficiency and color quality of the device. Among them, white light LEDs (WLEDs) have been widely used in medical lighting, plant growth lighting, and health lighting due to their high efficiency, versatility, and wide adaptability. Commercial WLEDs are mainly prepared by combining blue light LED chips with K2SiF6:Mn4+ microcrystals (KSFM) and CsPbBr3 nanocrystals. However, this type of device has significant technical defects: due to the lack of red light components, its color temperature is high and the color rendering index is low, resulting in problems such as insufficient light saturation and color distortion in daily lighting, making it difficult to meet the needs of high-quality lighting.

[0007] Existing technologies still face many challenges in achieving precise control of luminescence properties and controllability of material preparation. For example, Chen et al. used ammonia source molecular beam epitaxy to grow erbium-doped GaN with different doping concentrations. In the PL measurement, the concentration quenching of Er-related luminescence was observed. It can be seen that in rare earth ion-doped nanomaterials, the optimization of luminescence performance is highly dependent on the energy transfer efficiency between doped ions. However, when the doping concentration exceeds a specific range, the luminescence intensity and color regulation stability show a significant decrease due to the concentration quenching effect, which limits its application. In addition, the research of Zhu et al. further showed that it is a complex technical problem to achieve continuous regulation of luminescence color from green light to red light by changing the doping concentration of rare earth ions. This not only requires precise control of ion distribution at a variety of doping concentrations, but also requires that the material preparation process can ensure the high crystalline quality of nanoparticles to avoid non-radiative energy transitions caused by lattice defects, thereby maintaining stable luminescence performance. Summary of the invention

[0008] In view of the above technical problems, the present invention aims to propose an effective Er 3+ / Sm 3 + Preparation method of co-doped BaFCl nanoparticles, achieving efficient and adjustable luminescence from yellow-green to orange-red, while maintaining the high crystal quality and stability of the material. Specifically, by introducing precisely controlled doping concentration and optimized laser excitation mode, the technical difficulties of rare earth ion doped nanomaterials in luminescence color regulation and luminescence performance stability are solved. Based on Er 3+ and Sm 3+ Ion co-doping of BaFCl nanoparticles to prepare color-tunable phosphors can be achieved by changing the Sm 3+ Doping concentration can achieve color tuning from yellow-green to orange-red light.

[0009] The inventive idea of ​​the present invention is: the present invention prepares color-adjustable phosphors based on the rare earth ion co-doping method. Among all trivalent lanthanide ions, Er3+ and Sm3+ have long-life excited states and unique orange-red luminescence, respectively, and are widely used as good ET sensitizers and activators. In the selection of matrix materials, oxide and fluoride nanoparticles are two common host materials. Oxide nanoparticles have good chemical stability and thermal stability, while fluorine nanoparticles have excellent energy transfer efficiency and long fluorescence lifetime. Therefore, Er3+ and Sm3+ ion co-doped BaFCl nanoparticles are selected as the research object; the present invention prepares phosphors by using rare earth ion-doped nanoparticles to achieve color tuning from yellow-green light to orange-red under visible light excitation. The main implementation process is: BaFCl:Er used in the experiment 3+ / Sm 3+ The nanoparticles were prepared by a simple chemical coprecipitation method in aqueous solution. All raw materials (NH4F (ACS reagent, ≥98%), ErCl3·6H2O (99.9%), SmCl3·6H2O (99.9%), BaCl2·2H2O (99.9%)) were purchased from Sigma without further purification.

[0010] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is specifically: a method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doping BaFCl, comprising the following steps:

[0011] Step 1: At room temperature, add (98-x) mol% BaCl2·2H2O, 2 mol% ErCl3·6H2O, (x=0, 0.5, 1.0, 1.5, 2.0) SmCl3·6H2O to 25 ml of water and stir (ultrasound) to dissolve.

[0012] Step 2: After the solution becomes transparent, the resulting mixture is allowed to stand for about half an hour, and 25 ml of an aqueous solution containing 0.01 mol of NH4F is slowly added to the solution prepared in step 1 under vigorous stirring.

[0013] Step 3: Separate the obtained nanocrystal precipitate from the solution by centrifugation at 4000 rpm for 12 min, and pour out the supernatant.

[0014] Step 4: The obtained particles were washed with ethanol for 3-5 times, and the final sample was dried at 70°C for 12 hours.

[0015] The transmission electron microscopy (TEM) and X-ray diffraction (XRD) of the prepared nanoparticles are shown in Figure 1 , as shown in (a) and (b).

[0016] Step 5: Use 527nm nanosecond pulse laser as the excitation source to observe the transient luminescence process.

[0017] In step five, the advantage of nanosecond pulse laser over continuous laser pulse is that it has a higher peak power, and the monochromator has the advantage of wavelength resolution, so its spectrum and dynamic process can be analyzed.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. In the experiment, the present invention uses rare earth ions (Er 3+ and Sm 3+ ) co-doped BaFCl nanoparticles were excited with the same laser power (112 mW) and fixed Er 3+ concentration, change Sm 3+ Doping concentration, measured 2.0mol% Er 3+ / xmol%Sm 3+ The fluorescence spectra of the co-doped nanoparticles (x = 0, 0.5, 1.0, 1.5 and 2.0) are shown in Figure 3 shown.

[0020] 2. From Figure 2 It can be seen that when Sm 3+ When the doping concentration of Sm increases from 0mol% to 2mol%, 3+ The peak intensities at 596nm, 642nm and 700nm gradually increase. It is worth noting that Er 3+ The spectral intensity at its characteristic luminescence peaks of 665nm, 800nm ​​and 847nm decreased significantly. 3+ The increase of doping concentration has an effect on Er 3+ The luminescence of Sm was significantly inhibited by combining the monochromator and PMT. 3+ Doping concentration Er 3+The dynamic evolution of luminescence at 847 nm and the decay of fluorescence lifetime further confirmed the above experimental results. The ET efficiency η increased from 7.9% to 47%, which indicates that the prepared nanoparticle samples have achieved the transition from Er 3+ To Sm 3+ Efficient ET process.

[0021] 3. The present invention summarizes the corresponding CIE coordinate diagram as follows Figure 3 As shown in the figure, we can clearly see that the color tone of the sample gradually changes from yellow-green to orange-red. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0023] Figure 1 (a) Transmission electron microscopy (TEM) image showing the uniformity and distribution of the nanoparticles.

[0024] Figure 1 (b) shows the XRD patterns of both doped samples, showing sharp and clear diffraction peaks, indicating that the samples have good crystal structures, and is compared with the standard BaFCl data pattern.

[0025] Figure 2 This is the fluorescence spectrum of 2.0 mol% Er3+ / x mol% Sm3+ (x=0, 0.5, 1.0, 1.5 and 2.0) co-doped nanoparticles of the present invention under 112 mW laser power.

[0026] Figure 3 This is the CIE chromaticity diagram of the Er3+ / Sm3+ co-doped BaFCl phosphor at different Sm3+ concentrations of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Of course, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0028] Embodiment 1

[0029] See also Figure 2 and Figure 3The technical solution provided in this embodiment is a method for preparing color-adjustable phosphor by co-doping BaFCl with Er3+ / Sm3+. At room temperature, 98 mol% BaCl2·2H2O: 249.440 mg and 2 mol% ErCl3·6H2: 7.634 mg are weighed respectively and added to 25 ml of deionized water, stirred vigorously, and allowed to stand at room temperature for about half an hour. Subsequently, under vigorous stirring, an aqueous solution containing 0.01 mol NH4F of the same volume is added dropwise to the solution prepared in the previous step. The nanoparticles obtained by centrifugation are then washed several times with ethanol. The final product is dried at 70°C for 12 hours. A powdery trivalent rare earth Er is obtained. 3+ Yellow-green fluorescent material doped with BaFCl nanoparticles.

[0030] Embodiment 2

[0031] See also Figure 2 and Figure 3 , the technical solution provided in this embodiment is a method for preparing color-adjustable phosphor by co-doping BaFCl with Er3+ / Sm3+. At room temperature, 97mol% BaCl2·2H2O: 236.997mg, 2mol% ErCl3·6H2: 7.634mg and 1mol% SmCl3·6H2O: 3.648mg are weighed respectively and added to 25ml deionized water, stirred vigorously, and allowed to stand at room temperature for about half an hour. Subsequently, under vigorous stirring, an aqueous solution containing 0.01mol NH4F of the same volume is added dropwise to the solution prepared in the previous step. The nanoparticles obtained by centrifugation are then washed several times with ethanol. The final product is dried at 70°C for 12 hours. The powdery trivalent rare earth Sm 3+ and Er 3+ Yellow fluorescent materials co-doped with BaFCl nanoparticles.

[0032] Embodiment 3

[0033] See also Figure 2 and Figure 3 , the technical solution provided in this embodiment is a method for preparing color-adjustable phosphor by co-doping BaFCl with Er3+ / Sm3+. At room temperature, 96 mol% BaCl2·2H2O: 234.553 mg, 2 mol% ErCl3·6H2: 7.634 mg and 2 mol% SmCl3·6H2O: 7.296 mg are weighed respectively and added to 25 ml of deionized water, stirred vigorously, and allowed to stand at room temperature for about half an hour. Subsequently, under vigorous stirring, an aqueous solution containing 0.01 mol NH4F of the same volume is added dropwise to the solution prepared in the previous step. The nanoparticles obtained by centrifugation are then washed several times with ethanol. The final product is dried at 70°C for 12 hours. The powdery trivalent rare earth Sm3+ and Er 3+ Orange-red fluorescent material co-doped with BaFCl nanoparticles.

[0034] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doping BaFCl, characterized in that: The following steps are involved: Step 1: Add (98-x) mol% BaCl2·2H2O, 2 mol% ErCl3·6H2O, xSmCl3·6H2O to 25 ml of water at room temperature, and dissolve by stirring and ultrasonication; Step 2: After the solution becomes transparent, the resulting mixture is allowed to stand for half an hour, and 25 ml of an aqueous solution containing 0.01 mol of NH4F is slowly added to the solution prepared in step 1 under vigorous stirring; Step 3: Separate the obtained nanoparticle precipitate from the solution by centrifugation at 4000 rpm for 12 min, and pour out the supernatant; Step 4: The obtained particles were washed with ethanol for 3-5 times, and the final sample was dried at 70 °C for 12 h; Step 5: Use 527nm nanosecond pulse laser as the excitation source to observe the transient luminescence process.

2. The method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doped BaFCl according to claim 1, characterized in that: In the step 1, at room temperature, take 25 ml of distilled water and pour it into a clean beaker or container, weigh (98-x) mol% BaCl2·2H2O, 2 mol% ErCl3·6H2O and x mol% SmCl3·6H2O in sequence, add these solids one by one into the water, stir with a magnetic stirrer, and perform ultrasonic treatment to promote dissolution, continue stirring and ultrasonication until the solution is completely clarified, and ensure that all solutes are completely dissolved to form a uniform transparent solution.

3. The method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doped BaFCl according to claim 1, characterized in that: The transmission electron microscopy (TEM) and X-ray diffraction (XRD) of the nanocrystalline precipitate prepared in step 3 are shown in FIG. 1 , (a) and (b), respectively.

4. The method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doped BaFCl according to claim 1, characterized in that: In the step 5, the nanosecond pulse laser has an average peak power of 40W at 1KHz relative to the continuous laser pulser, and the monochromator has wavelength resolution, so its spectrum and dynamic process are analyzed.

5. The method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doped BaFCl according to claim 1 or 2, characterized in that: In the step 1, x=0 or 0.5 or 1.0 or 1.5 or 2.

0.

6. The method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doped BaFCl according to claim 1, characterized in that: The transparent solution obtained in step 1 is allowed to stand for about 30 minutes to ensure the stability of the solution. At the same time, 0.01 mol NH4F is weighed and completely dissolved in another 25 ml of distilled water to prepare a uniform NH4F aqueous solution. Under vigorous stirring, the NH4F solution is slowly added to the solution in step 1 using a burette or a pipette. The dropping process should be controlled at a speed of one drop per second. After the dropping is completed, stirring is continued for 10-20 minutes to ensure that the mixture reacts uniformly.

7. The method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doped BaFCl according to claim 1, characterized in that: The mixture after the reaction in step 2 is transferred to a centrifuge tube and centrifuged at 4000 rpm for 12 minutes. After the centrifugation is completed, the upper clear liquid is poured out and the white nanoparticle precipitate at the bottom is retained.

8. The method for preparing color-adjustable phosphor by Er3+ / Sm3+ co-doped BaFCl according to claim 1, characterized in that: In step 4, after pouring out the clear liquid, the nanoparticles are washed with ethanol for 3-5 times, then transferred to a clean drying dish, placed in a constant temperature oven at 70°C, and dried for 12 hours to remove moisture and ethanol. After drying, the obtained nanopowder is collected to be the final Er 3 + / Sm 3 + Co-doped BaFCl phosphor.

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