A red and near-infrared emitting rare earth-based phosphor

Abstract

The application discloses a red and near-infrared emission rare earth-based fluorescent powder and belongs to the technical field of luminescent materials. The application adopts a high-temperature solid-phase method to prepare the red and near-infrared emission rare earth-based fluorescent powder, and the chemical formula is Bi2Er (1‑x) O4Cl:xB; wherein 0.01<=x<=0.1; the element B is one of Li, Na and K. 3+ The element Er 3+ serves as a sensitized ion and a luminescent center ion. Different from a general up-conversion luminescent system which has multi-band emission in visible light, the red and near-infrared emission rare earth-based fluorescent powder has single-band red light emission in visible light, the luminescence is enhanced by 3.2 times, the emission range is wide, and the emission band covers a red light region of 630nm-730nm and a near-infrared region of 1500nm-1600nm. The near-infrared region has strong emission and thermal stability. In addition, the red and near-infrared emission rare earth-based fluorescent powder has low biological toxicity.

Description

Technical Field

[0001] This invention relates to a rare-earth-based phosphor that emits red and near-infrared light, belonging to the field of luminescent materials technology. Background Technology

[0002] Upconversion luminescence is the phenomenon of high-energy photon emission obtained from low-energy photon excitation. Upconversion materials can emit visible light under near-infrared light excitation, and therefore have attracted much attention recently. Compared with commonly used organic fluorescent materials and quantum dots, rare-earth upconversion luminescent materials have the characteristics of long luminescence lifetime, excellent photostability, strong penetration, and no background fluorescence. Therefore, rare-earth ion upconversion luminescent materials are used in various applications. In improving the color purity of displays in bioimaging and photodynamic therapy, monochromatic emission of upconversion luminescent materials is required. Especially in biomedicine, because short-wavelength light penetrates only a short depth into the skin, while long-wavelength light can penetrate deep into the skin, the red region and the near-infrared region are generally considered the "optical window" of biological tissues. Therefore, adjusting the excitation peak and emission peak to the "optical window" is essential for imaging deep tissues with fluorescent labeling. Achieving single red light emission remains an area of ​​research, and the preparation of upconversion luminescent materials with strong red emission has always been a challenging problem.

[0003] Compared to visible light and near-infrared I (NIR-I, 800–1000 nm), near-infrared II (NIR-II, 1000–1700 nm) fluorescence imaging techniques offer deeper penetration, higher resolution, and a higher signal-to-noise ratio within living tissues due to the low absorption and scattering by biological tissues and near-zero autofluorescence background noise. These techniques have been used for multiplex imaging within living tissues. However, most upconversion luminescent materials have emission peak wavelengths below 600 nm, are toxic, and exhibit reduced luminescence intensity at relatively high temperatures, posing limitations for research in the biomedical field. Therefore, this invention aims to find an upconversion luminescent material capable of emitting red light and near-infrared light above 600 nm, possessing high emission intensity and luminescence efficiency, while also exhibiting stability at higher temperatures. Summary of the Invention

[0004] To overcome the problems in the prior art, unlike general upconversion luminescence systems which exhibit multi-band emission in visible light, this invention uses Er... 3+ Ions, as the matrix material, exhibit red light emission in a single band of visible light, and also have strong emission in the near-infrared II region.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A rare-earth-based phosphor emitting red and near-infrared light, with the chemical formula Bi₂Er (1-x) O4Cl:xB; where 0.01≤x≤0.1; and element B is one of Li, Na, or K.

[0007] Rare earth-based phosphors emitting red and near-infrared light were prepared by a high-temperature solid-state method.

[0008] As a preferred embodiment of the present invention, the high-temperature solid-state method specifically includes: according to the chemical formula Bi2Er (1-x) O4Cl:xB raw materials are weighed, ground and mixed to obtain a raw material mixture, and then calcined to obtain rare earth-based phosphors emitting red and near-infrared light.

[0009] In a preferred embodiment of the present invention, the raw materials are bismuth salt, erbium salt, chlorine source and compound B; the compound B is lithium salt, sodium salt or potassium salt.

[0010] In a preferred embodiment of the present invention, the chlorine source is NH4Cl, and the molar ratio of NH4Cl to bismuth oxide is 1:1.2. The bismuth salt is an oxide, halide, carbonate, or nitrate of bismuth; the erbium salt is an oxide, halide, carbonate, or nitrate of erbium; the lithium salt is an oxide, halide, carbonate, or nitrate of lithium; the sodium salt is an oxide, halide, carbonate, or nitrate of sodium; and the potassium salt is an oxide, halide, carbonate, or nitrate of potassium.

[0011] In a preferred embodiment of the present invention, the calcination temperature is 700-900℃, the time is 12-24h, and the heating rate is 1-15℃ / min.

[0012] As a preferred embodiment of the present invention, the rare earth-based phosphor that emits red light and near-infrared light has visible light single-band red light emission and near-infrared II emission.

[0013] The beneficial effects of this invention: This invention successfully prepares Er using a high-temperature solid-state method. 3+ Ions are used as matrix materials, and alkali metals are added to modulate the crystal field, among which Er 3+ It acts as both a sensitizing ion and a luminescent center ion. Unlike typical upconversion luminescence systems that exhibit multi-band emission in the visible light spectrum, the rare-earth-based phosphor of this invention, which emits red and near-infrared light, exhibits a single-band red light emission in the visible light spectrum, with a 3.2-fold increase in luminescence and a wide emission range, covering the red light region of 630nm-730nm and the near-infrared II region of 1500nm-1600nm. Furthermore, it exhibits strong emission in the near-infrared II region and demonstrates thermal stability in this region, maintaining stable luminescence at certain temperatures. Additionally, the rare-earth-based phosphor with red and near-infrared emission exhibits low biotoxicity. Attached Figure Description

[0014] Figure 1 The images show a comparison of the XRD patterns of the materials prepared in Example 1 and Comparative Example 3.

[0015] Figure 2 The images show SEM images of the materials prepared in Example 1 and Comparative Example 3; (a) is an SEM image of the material prepared in Comparative Example 3, and (b) is an SEM image of the material prepared in Example 1.

[0016] Figure 3 The emission spectra of the materials prepared in Example 1 and Comparative Example 3 under 980nm laser irradiation are shown in Figure 1; (a) is the emission spectrum of the material prepared in Comparative Example 3 under 980nm laser irradiation, and (b) is the emission spectrum of the material prepared in Example 1 under 980nm laser irradiation.

[0017] Figure 4 The images show a comparison of the XRD patterns of the materials prepared in Example 1, Example 2, and Comparative Example 1.

[0018] Figure 5 The emission spectra of the materials prepared in Examples 1, 2 and Comparative Example 1 under 980nm laser irradiation are shown; (a) is the emission spectrum in the visible light region, and (b) is the emission spectrum in the near-infrared II region.

[0019] Figure 6 The image shows the near-infrared II temperature-varying emission spectrum of the sample prepared in Example 1.

[0020] Figure 7 The temperature sensitivity graphs are for the samples prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0022] All chemical reagents not described in the embodiments and comparative examples of this invention were commercially available analytical grade reagents used in the experiments.

[0023] Example 1

[0024] The compound formula of the rare-earth-based phosphor emitting red and near-infrared light described in this embodiment is Bi2Er. 0.99 O4Cl: 0.01K.

[0025] According to the chemical formula Bi2Er 0.99With a stoichiometric ratio of O4Cl:0.01K, accurately weigh Bi2O3, Er2O3, NH4Cl and K2CO3 and mix them together, with the ratio of NH4Cl to bismuth oxide being 1:1.2 to obtain a mixture. After grinding and mixing the mixture, calcine it at 850℃ for 12 hours, and then cool it down to obtain the calcined product. After crushing, grinding, classifying, and sieving the obtained calcined product, a rare earth-based phosphor emitting red light and near-infrared light can be obtained.

[0026] according to Figure 1 It can be seen that both Example 1 and Comparative Example 3 successfully obtained Bi2Er. 0.99 O4Cl: a 0.01K material, but the material obtained in Example 1 has higher crystallinity. Additionally, according to... Figure 2 It can be seen that the material prepared in Example 1 is a blocky, stacked material with a relatively large size. The material prepared by the hydrothermal method in Comparative Example 3 is a sheet-like material with a relatively small size.

[0027] according to Figure 3 It can be seen that the material prepared in Example 1 exhibits single-band red light emission in the visible light region, while the material prepared in Comparative Example 3 exhibits both green and red emission in the visible light region.

[0028] like Figure 5 As shown, the rare earth-based phosphor with red and near-infrared emission prepared in Example 1 can achieve single-band visible red light emission and near-infrared II emission under 980nm laser excitation. The emission range is relatively wide, covering the red light region of 630nm-730nm and the near-infrared II region of 1500nm-1600nm.

[0029] like Figure 6 As shown, with increasing temperature, the red and near-infrared emitting rare-earth-based phosphor prepared in Example 1 exhibits significantly enhanced emission in the near-infrared II region. This indicates that the red and near-infrared emitting rare-earth-based phosphor prepared in this invention is advantageous for use in high-temperature environments.

[0030] Example 2

[0031] The compound formula of the rare-earth-based phosphor emitting red and near-infrared light described in this embodiment is Bi2Er. 0.97 O4Cl: 0.03K.

[0032] According to the chemical formula Bi2Er 0.97With a stoichiometric ratio of O4Cl:0.03K, Bi2O3, Er2O3, NH4Cl and K2CO3 are accurately weighed and mixed, with the ratio of NH4Cl to bismuth oxide being 1:1.2, to obtain a mixture. The mixture is then ground and calcined at 900℃ for 16 hours, and the calcined product is obtained after cooling. The calcined product is then subjected to post-treatment such as crushing, grinding, grading, and sieving to obtain rare earth-based phosphors that emit red and near-infrared light.

[0033] according to Figure 4 It can be seen that Bi2Er was successfully obtained in Example 2. 0.99 O4Cl: 0.03K material.

[0034] like Figure 5 As shown, the rare-earth-based phosphor prepared in Example 2, which emits red and near-infrared light, can achieve single-band red light emission in the visible light region and near-infrared II emission in the near-infrared region when excited by a 980nm laser. The emission range is wide, covering the red light region of 630nm-730nm and the near-infrared II region of 1500nm-1600nm. Compared to Comparative Example 1, the material prepared in Example 2 shows a 3.2-fold increase in emission intensity in the visible light region and a 2-fold increase in emission intensity in the near-infrared II region.

[0035] Example 3

[0036] The compound formula of the rare-earth-based phosphor emitting red and near-infrared light described in this embodiment is Bi2Er. 0.9 O4Cl: 0.1Na.

[0037] According to the chemical formula Bi2Er 0.9 The stoichiometric ratio of O4Cl:0.1Na was used to accurately weigh Bi2O3, Er2O3, NH4Cl, and Na2CO3 and mix them together, with the ratio of NH4Cl to bismuth oxide being 1:1.2. The mixture was then ground and calcined at 700℃ for 24 hours, and the calcined product was obtained after cooling. The calcined product was then subjected to post-treatment such as crushing, grinding, grading, and sieving to obtain rare earth-based phosphors emitting red and near-infrared light.

[0038] The rare-earth-based phosphor with red and near-infrared emission prepared in Example 3 can achieve single-band visible red light emission and near-infrared II emission under 980nm laser excitation. The emission range is relatively wide, covering the red light region of 630nm-730nm and the near-infrared II region of 1500nm-1600nm.

[0039] Comparative Example 1

[0040] A method for preparing Bi2ErO4Cl material, comprising:

[0041] Bi₂O₃, Er₂O₃, and NH₄Cl were accurately weighed and mixed according to the stoichiometric ratio of the chemical formula Bi₂ErO₄Cl, with the ratio of NH₄Cl to bismuth oxide being 1:1.2, to obtain a mixture. The mixture was then ground and homogenized, and calcined at 850℃ for 12 hours. After cooling, the calcined product was obtained. The calcined product was then subjected to post-treatment such as crushing, grinding, grading, and sieving to obtain Bi₂ErO₄Cl.

[0042] according to Figure 4 It can be seen that Bi2ErO4Cl material was successfully obtained in Comparative Example 1.

[0043] like Figure 5 As shown, the Bi₂ErO₄Cl rare-earth-based phosphor prepared in Comparative Example 1 can achieve single-band visible red light emission and near-infrared II emission under 980nm laser excitation, with a wide emission range, covering the 630nm-730nm red light region and the 1500nm-1600nm near-infrared II region. However, as... Figure 7 As shown, the Bi₂ErO₄Cl material exhibits the highest temperature sensitivity of 1.87 × 10⁻⁶ under 980 nm laser excitation. -3 K -1 The Bi2Er prepared in Example 2 0.97 The highest value of O4Cl at 0.03K is 2.83 × 10⁻⁶. -3 K -1 It is 1.5 times better than Bi2ErO4Cl material.

[0044] Comparative Example 2

[0045] The compound formula of the rare-earth-based phosphor emitting red and near-infrared light described in this comparative example is Bi₂Yb. 0.99 O4Cl: 0.01K.

[0046] According to the chemical formula Bi₂Yb 0.99 With a stoichiometric ratio of O4Cl:0.01K, Bi2O3, Yb2O3, NH4Cl and K2CO3 are accurately weighed and mixed, with the ratio of NH4Cl to bismuth oxide being 1:1.2, to obtain a mixture. The mixture is then ground and calcined at 850℃ for 12 hours, and the calcined product is obtained after cooling. The calcined product is then subjected to post-treatment such as crushing, grinding, grading, and sieving to obtain rare earth-based phosphors that emit red and near-infrared light.

[0047] Bi2Yb prepared in Comparative Example 2 0.99 O4Cl: The material at 0.01K does not exhibit luminescence when excited by a 980nm laser.

[0048] Comparative Example 3

[0049] The rare earth-based phosphor described in this embodiment has the compound formula Bi2Er. 0.99 O4Cl: 0.01K.

[0050] Bi2Er 0.99 The preparation methods of O4Cl:0.01K phosphor include:

[0051] (1) Weigh 1.9402g Bi(NO3)3 and 0.0027g K2CO3 into a 100ml beaker, add 15-20ml of deionized water into the beaker, and stir for 10 minutes to dissolve them completely.

[0052] (2) Add 3.96 ml of 0.5 mol / L Er(NO3)3 solution and stir for 10 min to mix it thoroughly. The solution is pinkish-white and opaque. Then add 20 ml of saturated NaCl solution and stir for 10 min. The solution is pinkish and transparent. Finally, add 0.3 mol / L NaOH solution to adjust the pH to 11 and stir for 10 min to mix it thoroughly to obtain the mixed solution.

[0053] (3) Transfer the mixture to the liner of a 100ml reaction vessel, place it in an oven and keep it at 180℃ for 24h, cool it to room temperature, wash the reacted sample with deionized water and anhydrous ethanol, centrifuge, and dry it at 70℃ for 12h to obtain Bi2Er. 0.99 O4Cl:0.01K phosphor.

[0054] like Figure 3 As shown, under 980nm laser excitation, the material prepared in Comparative Example 3 exhibits both green and red upconversion luminescence.

[0055] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A rare-earth-based phosphor emitting red and near-infrared light, characterized in that: The chemical formula is Bi2Er (1-x) O4Cl:xB; where 0.01≤x≤0.1; and element B is one of Li, Na, or K. Rare earth-based phosphors emitting red and near-infrared light were prepared by a high-temperature solid-state method.

2. The rare-earth-based phosphor emitting red and near-infrared light according to claim 1, characterized in that: The high-temperature solid-state method specifically includes: according to the general chemical formula Bi2Er (1-x) O4Cl:xB raw materials are weighed, ground and mixed to obtain a raw material mixture, and then calcined to obtain rare earth-based phosphors emitting red and near-infrared light.

3. The rare-earth-based phosphor emitting red and near-infrared light according to claim 2, characterized in that: The raw materials are bismuth salt, erbium salt, chlorine source and compound B; the compound B is lithium salt, sodium salt or potassium salt.

4. The rare-earth-based phosphor emitting red and near-infrared light according to claim 3, characterized in that: The chlorine source is NH4Cl, and the molar ratio of NH4Cl to bismuth oxide is 1:1.

2.

5. The rare-earth-based phosphor emitting red and near-infrared light according to claim 2, characterized in that: The calcination temperature is 700–900℃, the time is 12–24 h, and the heating rate is 1–15℃ / min.

6. The rare-earth-based phosphor emitting red and near-infrared light according to claim 1, characterized in that: The rare-earth-based phosphor that emits red and near-infrared light has visible single-band red light emission and near-infrared II emission.

Images