Rare-earth-based fluorescent powder capable of emitting red light and near-infrared light

Abstract

The invention discloses rare earth-based fluorescent powder capable of emitting red light and near-infrared light, and belongs to the technical field of luminescent materials. The rare earth-based fluorescent powder capable of emitting red light and near infrared is prepared by adopting a high-temperature solid-phase method, and the chemical formula is Bi2Er (1-x) O4Cl: xB, wherein x is not less than 0.01 and not more than 0.1; and the B element is one of Li, Na and K elements. Er < 3 + > ions serve as a matrix material, alkali metal is added to regulate and control a crystal field, and Er < 3 + > serves as sensitizing ions and also serves as luminescence center ions. Different from a common up-conversion luminescence system with multiband emission in visible light, the rare-earth-based fluorescent powder with red light and near-infrared emission has red light emission in a single band in visible light, luminescence is enhanced by 3.2 times, the emission range is wide, and an emission band covers a red light area of 630-730 nm and a near-infrared second area of 1500-1600 nm. The material has strong emission in a near-infrared second region and has thermal stability. In addition, the red light and near infrared emission rare earth-based fluorescent powder has low biotoxicity.

Description

Technical Field

[0001] The invention relates to a rare earth-based fluorescent powder emitting red light and near infrared light, belonging to the technical field of luminescent materials. Background Art

[0002] Upconversion luminescence is a phenomenon in which low-energy photons are excited to obtain high-energy photon emission. Upconversion materials can obtain visible light emission under near-infrared light excitation, so they 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, upconversion luminescent materials of rare earth ions are used in various applications. In bioimaging and photodynamic therapy to improve the color purity of displays, upconversion luminescent materials are required to achieve monochromatic emission. Especially in biomedicine, since the short-wavelength light below penetrates the skin to a small depth, and the long-wavelength light can penetrate deep into the skin, the red region and the near-infrared region are generally considered to be the "optical window" of biological tissues. Therefore, adjusting the excitation peak and emission peak to the "optical window" is essential for deep tissue imaging of fluorescent labels. Achieving single red light emission is still a direction that needs to be worked on, and the preparation of upconversion luminescent materials with strong red emission has always been a challenging problem.

[0003] Compared with visible light and near infrared region I (NIR-I, 800-1000nm), near infrared region II (NIR-II, 1000-1700nm) fluorescence imaging technology has deep penetration ability, high resolution and signal-to-noise ratio in vivo due to its low absorption and scattering by biological tissues, and near-zero autofluorescence background noise, and has been used for multiple imaging in living tissues. However, the emission peak wavelength of most up-conversion luminescent materials is below 600nm, or they are toxic, and the luminescence intensity is weakened at relatively high temperatures, which has certain constraints on research in the biomedical field. Therefore, the present invention needs to find an up-conversion luminescent material that can emit red light and near-infrared light at a wavelength above 600nm, and has a high emission intensity and luminescence efficiency, and at the same time needs to have a certain stability in a high temperature environment. Summary of the invention

[0004] In order to overcome the problems in the background technology, unlike the general up-conversion luminescent system which has multi-band emission in the visible light, the present invention uses Er 3+ As the matrix material, the ions have a single-band red light emission in the visible light, and at the same time have strong emission in the near-infrared region.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions:

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

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

[0008] As a preferred embodiment of the present invention, the high temperature solid phase method specifically comprises: according to the chemical formula Bi2Er (1-x) O4Cl:xB weigh the raw materials, grind and mix them to obtain a raw material mixture, and then calcine them to obtain red and near-infrared emitting rare earth-based phosphors.

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

[0010] As 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 bismuth oxide, halide, carbonate or nitrate; the erbium salt is erbium oxide, halide, carbonate or nitrate; the lithium salt is lithium oxide, halide, carbonate or nitrate; the sodium salt is sodium oxide, halide, carbonate or nitrate; the potassium salt is potassium oxide, halide, carbonate or nitrate.

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

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

[0013] Beneficial effects of the present invention: The present invention successfully prepares Er by using a high temperature solid phase method 3+ Ions are used as matrix materials, and alkali metals are added to regulate the crystal field. 3+ It acts as both a sensitizing ion and a luminescent center ion. Unlike general up-conversion luminescent systems that have multi-band emission in visible light, the rare earth-based phosphors emitting red light and near-infrared light of the present invention have a single-band red light emission in visible light, with luminescence enhancement of 3.2 times and a wide emission range. The emission band covers the red light region of 630nm-730nm and the near-infrared region II of 1500nm-1600nm. It has strong emission in the near-infrared region II, and the emission in the near-infrared region II is thermally stable, and can maintain stable luminescence at a certain temperature. In addition, the rare earth-based phosphors emitting red light and near-infrared light have low biological toxicity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The XRD comparison diagram of the materials prepared in Example 1 and Comparative Example 3.

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

[0016] Figure 3 These are emission spectra of the materials prepared in Example 1 and Comparative Example 3 under 980nm laser irradiation; (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 This is a comparison chart of XRD of materials prepared in Example 1, Example 2 and Comparative Example 1.

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

[0019] Figure 6 This is the near-infrared second-zone variable temperature emission spectrum of the sample prepared in Example 1.

[0020] Figure 7 The samples prepared in Example 1 and Comparative Example 1 are the sensitivity factor diagrams to temperature. DETAILED DESCRIPTION

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

[0022] All chemical reagents not specified in the examples and comparative examples of the present invention were commercially available analytically pure for experiments.

[0023] Example 1

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

[0025] According to the chemical formula Bi2Er 0.99Bi2O3, Er2O3, NH4Cl and K2CO3 are accurately weighed and mixed in a stoichiometric ratio of 1:1.2 to obtain a mixture; the mixture is ground and mixed, and then calcined at 850°C for 12h, and a calcined product is obtained after cooling; the calcined product is post-processed by crushing, grinding, grading, screening and washing to obtain a rare earth-based phosphor emitting red light and near-infrared light.

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

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

[0029] like Figure 6 As shown, with the increase of temperature, the emission of the red light and near-infrared emitting rare earth-based phosphor prepared in Example 1 in the near-infrared second region is significantly enhanced. It can be seen that the red light and near-infrared emitting rare earth-based phosphor prepared in the present invention is advantageous for use in high temperature environments.

[0030] Example 2

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

[0032] According to the chemical formula Bi2Er 0.97Bi2O3, Er2O3, NH4Cl and K2CO3 are accurately weighed and mixed in a stoichiometric ratio of 1:1.2 to obtain a mixture; the mixture is ground and mixed, and then calcined at 900°C for 16 hours, and a calcined product is obtained after cooling; the calcined product is post-processed by crushing, grinding, grading, screening and washing to obtain a rare earth-based phosphor emitting red light and near-infrared light.

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

[0034] like Figure 5 As shown, the red and near-infrared emitting rare earth-based phosphor prepared in Example 2 can realize visible single-band red light emission and near-infrared region II emission under 980nm laser excitation, with a wide emission range, and the emission band covers the red light region of 630nm-730nm and the near-infrared region II of 1500nm-1600nm. Compared with Comparative Example 1, the emission intensity of Example 2 in the visible light region is increased by 3.2 times, and the emission intensity of Example 2 in the near-infrared region II is increased by 2 times.

[0035] Example 3

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

[0037] According to the chemical formula Bi2Er 0.9 O4Cl:0.1Na. Bi2O3, Er2O3, NH4Cl and Na2CO3 are accurately weighed and mixed, and the ratio of NH4Cl to bismuth oxide is 1:1.2 to obtain a mixture; the mixture is ground and mixed, and then calcined at 700°C for 24 hours, and a calcined product is obtained after cooling; the calcined product is post-processed by crushing, grinding, grading, screening and washing to obtain red and near-infrared emitting rare earth-based phosphors.

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

[0039] Comparative Example 1

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

[0041] According to the stoichiometric ratio of the chemical formula Bi2ErO4Cl, Bi2O3, Er2O3 and NH4Cl are accurately weighed and mixed, and the ratio of NH4Cl to bismuth oxide is 1:1.2 to obtain a mixture; the mixture is ground and mixed, and then calcined at 850°C for 12 hours, and a calcined product is obtained after cooling; the obtained calcined product is post-processed by crushing, grinding, grading, screening and washing to obtain Bi2ErO4Cl.

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

[0043] like Figure 5 As shown in FIG. 1 , the Bi2ErO4Cl rare earth-based phosphor prepared in Comparative Example 1 can realize visible light single-band red light emission and near-infrared second region emission under 980nm laser excitation, and the emission range is relatively wide, with the emission band covering the red light region of 630nm-730nm and the near-infrared second region of 1500nm-1600nm. Figure 7 As shown in Figure 2, the temperature sensitivity of Bi2ErO4Cl material under 980nm laser excitation is as high as 1.87×10 -3 K -1 , while the Bi2Er prepared in Example 2 0.97 O4Cl: 0.03K, the highest is 2.83×10 -3 K -1 , which is 1.5 times higher than that of Bi2ErO4Cl material.

[0044] Comparative Example 2

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

[0046] According to the chemical formula Bi2Yb 0.99 Bi2O3, Yb2O3, NH4Cl and K2CO3 are accurately weighed and mixed in a stoichiometric ratio of 1:1.2 to obtain a mixture; the mixture is ground and mixed, and then calcined at 850°C for 12h, and a calcined product is obtained after cooling; the calcined product is post-processed by crushing, grinding, grading, screening and washing to obtain a rare earth-based phosphor emitting red light and near-infrared light.

[0047] Comparative Example 2 Bi2Yb 0.99 O4Cl: 0.01K material does not emit light under 980nm laser excitation.

[0048] Comparative Example 3

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

[0050] oeLh 0.99 The preparation method of O4Cl:0.01K phosphor includes:

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

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

[0053] (3) The mixed solution was transferred to a 100 ml reactor liner, placed in an oven at 180 °C for 24 h, cooled to room temperature, and the reacted sample was washed with deionized water and anhydrous ethanol, centrifuged, and dried at 70 °C for 12 h to obtain Bi2Er 0.99 O4Cl: 0.01K phosphor.

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

[0055] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than 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 in form and details without departing from the scope defined by the claims of the present invention.

Claims

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

2. The red and near-infrared emitting rare earth-based phosphor according to claim 1, characterized in that: The high temperature solid phase method specifically includes: according to the chemical formula Bi2Er (1-x) O4Cl:xB weigh the raw materials, grind and mix them to obtain a raw material mixture, and then calcine them to obtain red and near-infrared emitting rare earth-based phosphors.

3. The red and near-infrared emitting rare earth-based phosphor according to claim 1, characterized in that: The raw materials are bismuth salt, erbium salt, chlorine source and B compound; the B compound is lithium salt, sodium salt or potassium salt.

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

2.

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

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

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