Rare earth doped lithium yttrium silicate up-conversion luminescent material and preparation method thereof

Abstract

The invention relates to the field of luminescent materials, in particular to a rare earth doped lithium yttrium silicate up-conversion luminescent material and a preparation method thereof, the structure of the up-conversion luminescent material is Li (Y1-xErx) 9 (SiO4) 6O2, x = 0.005-0.03; under the irradiation of a 980nm laser, the up-conversion luminescent material can generate intense red light with the central wavelength of 660nm for emission; the up-conversion luminescent material is prepared by weighing corresponding lithium carbonate, silicon dioxide, yttrium oxide and erbium oxide as raw materials according to a molar ratio of Li, Si, Y and Er of 1: 6: 9-9x: 9x. The up-conversion luminescent material has the beneficial effects that high-quality intense red light with the wavelength of 660 nm can be generated under laser with the wavelength of 980 nm, the limitation that the spectrum of irradiation light must be 660-950 nm is broken through, and a novel up-conversion luminescent material is provided for the field of biomedicine; and the synthesis method is simple and convenient to operate, simple in process, high in controllability and short in preparation period.

Description

Technical Field

[0001] The invention relates to the technical field of luminescent materials, in particular to a rare earth doped lithium yttrium silicate up-conversion luminescent material and a preparation method thereof. Background Art

[0002] Upconversion luminescence is an anti-Stokes process characterized by the conversion of low-energy light into high-energy light, usually involving a nonlinear optical process in which two or more long-wavelength photons are converted into one short-wavelength photon. In recent years, rare-earth-doped upconversion materials have shown extensive application potential in a variety of fields, such as colorful display technology, optical anti-counterfeiting, optical temperature sensors, and sensitized solar cells, due to their stable physicochemical properties, narrow emission bands, and background-free fluorescence. Compared with traditional organic dyes (such as rhodamine-B) and quantum dot materials (such as cadmium sulfide, cadmium selenide, and cadmium telluride quantum dots), rare-earth-doped upconversion materials show more outstanding physicochemical stability, low toxicity, and long-wavelength excitation capabilities. These advantages have made the research of rare-earth-doped upconversion materials in the biomedical field increasingly concerned.

[0003] Because Er 3+ Ions have a rich energy level structure, which contains high-energy upconversion photons, which will have a certain impact on biological cells. Therefore, in the prior art, in order to achieve precise biological treatment and biological imaging in biological applications, in order to obtain strong red light emission, the method of doping rare earth ions into upconversion materials is adopted; and the spectrum of upconversion materials doped with rare earth ions is generally limited to a specific "biological window" (650-950nm laser).

[0004] However, through research and development, our team discovered that the up-conversion material formed by mixing the corresponding substances in a specific ratio can produce strong red light even if it is not within the specific "biological window" (650-950nm laser). Specifically, it can produce strong red light emission with a central wavelength of 660nm. This phenomenon shows that the newly synthesized up-conversion material can also be used in biological treatment and biological imaging, thus providing a new material in the biomedical field (breaking the requirement that the illumination spectrum of general up-conversion materials must be limited to the "biological window" (650-950nm laser) when used).

[0005] In addition, the team borrowed the idea of ​​"high-temperature solid-phase synthesis of silicates" when synthesizing the new upconversion materials, and the borrowed idea is feasible; this makes the synthesis of the new upconversion materials simpler, more controllable, and with a shorter synthesis cycle than the general upconversion material synthesis method. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a rare earth doped lithium yttrium silicate upconversion luminescent material and a preparation method thereof, breaking the limitation that the irradiation spectrum of the upconversion material must be within the "biological window" of 650-950nm, and solving the technical problems of the general upconversion material such as complex preparation process, poor controllability, low repeatability and expensive raw material cost.

[0007] The object of the present invention is achieved by the following technical solutions: In the first aspect, a rare earth doped lithium yttrium silicate upconversion luminescent material is provided, wherein the structure of the upconversion luminescent material is Li(Y 1-x Er x ) 9 (SiO 4 ) 6 O 2 , where x = 0.005-0.03;

[0008] The up-conversion luminescent material can generate strong red light emission with 660nm as the central wavelength under the irradiation of 980nm laser.

[0009] Furthermore, the up-conversion luminescent material is the corresponding lithium carbonate, silicon dioxide, yttrium oxide and erbium oxide as raw materials, wherein the elements Li, Si, Y and Er are weighed in a molar ratio of 1:6:9-9x:9x; wherein x=0.005-0.03.

[0010] In a second aspect, a method for preparing a rare earth-doped lithium yttrium silicate upconversion luminescent material is provided, comprising the following steps:

[0011] Step 1: Weigh corresponding lithium carbonate, silicon dioxide, yttrium oxide and erbium oxide as raw materials in a molar ratio of 1:6:9-9x:9x of the elements Li, Si, Y and Er, wherein x=0.005-0.03;

[0012] Step 2: Pour the raw materials weighed in step 1 into a container, add anhydrous ethanol, and stir thoroughly to obtain a uniform suspension;

[0013] Step 3: The suspension is allowed to stand until the clear liquid and the precipitate are separated, and then dried to completely evaporate the anhydrous ethanol in the container to obtain a powder raw material;

[0014] Step 4: Press the powdered raw material obtained in step 3 into a disc-shaped sample;

[0015] Step 5: Place the disc-shaped sample obtained in step 4 into a furnace, raise the temperature to 1250°C to 1350°C for sintering; after sintering, naturally cool to room temperature, take out the sample, grind it into powder, and obtain a rare earth-doped lithium yttrium silicate up-conversion red light emitting material.

[0016] Furthermore, in step 2, the concentration of the suspension is 0.1-0.2 g of the raw material compound per ml of anhydrous ethanol. Preferably, the container used is a 50 mL beaker, and a magnetic stirrer is used for stirring.

[0017] Furthermore, in step 3, the drying temperature is 50°C to 70°C, and the drying time is 10 to 12 hours. The drying temperature of 50°C to 70°C can prevent the anhydrous ethanol from boiling and causing the suspension to splash out, thereby avoiding the loss of raw materials and imbalance of the ratio. The drying time of 10 to 12 hours can ensure that the anhydrous ethanol in the raw material is completely evaporated.

[0018] Furthermore, in the step three, the standing time is 30 to 40 minutes.

[0019] Furthermore, in step 5, the temperature is kept within the range of 1250°C to 1350°C for 3 to 5 hours to ensure that the oxides of the components can fully react chemically to obtain the desired target product. Preferably, the furnace used is a high-temperature muffle furnace, and the sintering time is preferably 4 hours.

[0020] The present invention has the following advantages:

[0021] (1) A new upconversion luminescent material was synthesized, and the upconversion luminescent material broke the limitation that the spectrum must be between 650-950nm when irradiated by laser;

[0022] It should be noted that, in general up-conversion luminescent materials, when used in biotherapy and bio-imaging, the spectrum during laser irradiation is limited to the "biological window" of 650-950nm (that is, only under this spectrum can the up-conversion luminescent material emit strong red light, and the strong red light under such circumstances can meet the requirements of biotherapy and bio-imaging);

[0023] However, this scheme has developed a new up-conversion luminescent material (structural formula is Li(Y 1-x Er x ) 9 (SiO 4 ) 6 O 2 A new up-conversion luminescent material, x = 0.005-0.03), which can also emit strong red light under the irradiation of 980nm near-infrared laser, and the emitted red light is a strong red light with 660nm as the central wavelength, which can also meet the requirements of biological treatment and biological imaging; thus breaking the traditional condition that up-conversion luminescent materials must be irradiated with 680-950nm (biological window) laser; providing a new up-conversion luminescent material in the biomedical field;

[0024] (2) The method of synthesizing new upconversion luminescent materials is simple to operate, simple in process, highly controllable and has a short preparation cycle;

[0025] In the synthesis of silicates, high temperature solid phase method, combustion method and coprecipitation method are adopted;

[0026] This scheme also borrows the "synthesis method of silicates using a high-temperature solid-phase method" in the synthesis of up-conversion luminescent materials, and finds that it is feasible; due to the advantages of the high-temperature solid-phase method such as easy operation, simple process, high controllability and short preparation cycle, the high-temperature solid-phase method is applied to the synthesis of new up-conversion luminescent materials, providing an efficient and reliable approach (during the synthesis of this scheme: first, the raw materials such as lithium carbonate, silicon dioxide, yttrium oxide, and erbium oxide need to be mechanically stirred to ensure that they are evenly mixed; then, the mixture is dried and further ground into powder; then, the powder is pressed into sheets for subsequent high-temperature calcination. After the high-temperature calcination process in a muffle furnace, the target product can finally be obtained). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Li(Y 1-x Er x ) 9 (SiO 4 ) 6 O 2 (x=0.005, 0.01, 0.02, 0.03) X-ray diffraction spectra of powder samples.

[0028] Figure 2 Li(Y 1-x Er x ) 9 (SiO 4 ) 6 O 2 Up-conversion luminescence spectra of the samples (x=0.005, 0.01, 0.02, 0.03).

[0029] Figure 3 The Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 X-ray diffraction spectrum of powder sample.

[0030] Figure 4 The Li(Y 0.98 Er 0.02 ) 9 (SiO 4 )6 O 2 Spectrum of the powder sample under excitation by 980nm near-infrared laser.

[0031] Figure 5 The Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 X-ray diffraction spectrum of powder sample.

[0032] Figure 6 The Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 Spectrum of the powder sample under excitation by 980nm near-infrared laser.

[0033] Figure 7 Li(Y) synthesized in Example 3 0.97 Er 0.03 ) 9 (SiO 4 ) 6 O 2 X-ray diffraction spectrum of powder sample.

[0034] Figure 8 Li(Y) synthesized in Example 3 0.97 Er 0.03 ) 9 (SiO 4 ) 6 O 2 Spectrum of the powder sample under excitation by 980nm near-infrared laser. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the first aspect, the present embodiment discloses a rare earth doped lithium yttrium silicate upconversion luminescent material, the structural formula of the upconversion luminescent material is: Li(Y 1-x Er x ) 9 (SiO 4 ) 6 O 2 , wherein x = 0.005-0.03. In addition, the up-conversion luminescent material is the elements Li, Si, Y, Er in a molar ratio of 1:6:9-9x:9x. The corresponding lithium carbonate, silicon dioxide, yttrium oxide and erbium oxide are weighed as raw materials.

[0038] In a second aspect, this embodiment discloses a method for preparing a rare earth-doped lithium yttrium silicate upconversion luminescent material, comprising the following steps:

[0039] Step 1: lithium carbonate, silicon dioxide, yttrium oxide and erbium oxide are weighed as raw materials according to the molar ratio of Li, Si, Y and Er of 1:6:9-9x:9x; wherein x=0.005-0.03;

[0040] Step 2: Pour the raw materials weighed in step 1 into a clean 50 mL beaker, add anhydrous ethanol, and stir thoroughly with a magnetic stirrer to obtain a uniform suspension; the concentration of the obtained suspension is 0.1-0.2 g of the raw material compound per ml of anhydrous ethanol;

[0041] Step 3: let the suspension stand until the clear liquid and the precipitate are separated, and let stand for 30-40 minutes; dry the beaker to completely evaporate the anhydrous ethanol, and the drying temperature should be set between 50-70°C to avoid the anhydrous ethanol from boiling and causing the suspension to splash out, resulting in loss of raw materials and imbalance of the ratio. The drying time is set to 10-12 hours to ensure that the anhydrous ethanol in the raw material is completely evaporated; then obtain the powder raw material;

[0042] Step 4: Press the uniform raw material dried in step 3 into a round sheet;

[0043] Step 5: Place the disc-shaped sample pressed in step 4 into a high-temperature muffle furnace, raise the temperature to 1250°C-1350°C and keep it warm for 3-5 hours to ensure that the oxides of each component can fully react chemically. After naturally cooling to room temperature, take out the sample, grind it into powder, and obtain a rare earth-doped lithium yttrium silicate up-conversion red light emitting material.

[0044] The rare earth-doped lithium yttrium silicate upconversion luminescent material disclosed above is applied in the fields of anti-counterfeiting, biotherapy, or bioimaging.

[0045] By way of example, specific examples are given below.

[0046] Example 1

[0047] In this example, Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 The sample was prepared as follows:

[0048] According to the molar ratio of Li, Si, Y, and Er of 1:6:8.82:0.18, the mass of 0.00042 mol of lithium carbonate, 0.00499 mol of silicon dioxide, 0.00367 mol of yttrium oxide, and 0.00007 mol of erbium oxide was calculated and weighed accurately. Put all the raw materials into a 50 mL beaker, add 30 mL of anhydrous ethanol as a dispersing solvent, stir with a magnetic stirrer to mix the raw materials thoroughly, and let it stand for 30 minutes to separate them. Put the beaker in an oven, set the temperature to 60 ° C, and dry for 12 hours to completely evaporate the anhydrous ethanol in the raw materials. Cool to room temperature, take out the beaker, divide the mixed dry precursor into 6 parts, and use a manual tablet press to press the divided precursor into discs, where the pressure is 25 MPa for 10 minutes to ensure that the precursor is pressed into the required sheet. The pressed precursor sheet was placed in a muffle furnace, and the heating curve was set at a heating rate of 10 °C / min. The temperature was raised to 1350 °C and maintained for 4 hours to allow the precursor to fully react to generate Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 After the furnace is naturally cooled to room temperature, the sample is taken out and ground into powder using an agate grinding cup to obtain a rare earth doped lithium yttrium silicate up-conversion red light emitting material.

[0049] Figure 3 The X-ray diffraction pattern of Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 Compared with LiY 9 (SiO 4 ) 6 O 2 (PDF card number is 98-028-1545) diffraction spectrum is consistent, indicating that the sintered product Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 It is a single-phase LiY with a hexagonal phase9 (SiO 4 ) 6 O 2 , while also indicating that rare earth Er 3+ Ions were successfully incorporated into LiY 9 (SiO 4 ) 6 O 2 In the crystal, the crystal structure is not changed.

[0050] Depend on Figure 4 The spectrum of the Er prepared by the present invention under the near-infrared 980nm laser excitation shows that 2 O 3 Doped LiY 9 (SiO 4 ) 6 O 2 After being excited, the powder sample can emit up-conversion red light, and the red light emission intensity is the strongest. The corresponding red light emission center wavelength is 660nm.

[0051] Example 2

[0052] The composition ratio is exactly the same as that in Example 1. When x = 0.02, that is, Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 According to Example 1, Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 The steps of the sample are to change the sintering step of Example 1 from 1350°C for 4 hours to 1250°C for 4 hours, and the other steps remain unchanged, in order to verify the repeatability of the present invention at different temperatures.

[0053] Figure 5 The X-ray diffraction pattern shows that the diffraction peaks of the sample completely correspond to those of the standard card, that is, the obtained Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 The phase of the sample is consistent with LiY 9 (SiO 4 ) 6 O 2 (PDF card number is 98-028-1545), indicating that the product is a single-phase LiY also with a hexagonal phase 9 (SiO4 ) 6 O 2 .

[0054] Depend on Figure 6 The spectrum of Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 The sample has the maximum red light emission intensity at a red light wavelength of 660 nm, which is higher than that of Li(Y 0.98 Er 0.02 ) 9 (SiO 4 ) 6 O 2 The red light emission intensity of the samples is basically the same for both, which indicates that they have the same physical phase and little difference in upconversion luminescence ability.

[0055] Example 3

[0056] In this example, Li(Y 0.97 Er 0.03 ) 9 (SiO 4 ) 6 O 2 According to the method of Example 1, Li (Y 0.97 Er 0.03 ) 9 (SiO 4 ) 6 O 2 Up-conversion red light emitting material, at this time x = 0.03, the only difference is the weight of yttrium oxide and erbium oxide, specifically: the content of yttrium oxide is adjusted from 0.00367mol to 0.00363mol; the content of erbium oxide is adjusted from 0.00007mol to 0.00011mol, and the other steps remain unchanged. Finally, Li(Y 0.97 Er 0.03 ) 9 (SiO 4 ) 6 O 2 Up-conversion red light emitting material. The purpose is to verify the stability of the present invention in regulating raw material composition and manufacturing process and the change of up-conversion luminescence after regulating and reducing a certain amount of rare earth erbium oxide, compared with Example 1.

[0057] Figure 7 The X-ray diffraction spectrum of Li(Y 0.97 Er0.03 ) 9 (SiO 4 ) 6 O 2 The crystal structure of the upconversion red light emitting material conforms to LiY 9 (SiO 4 ) 6 O 2 (PDF card number is 98-028-1545).

[0058] Depend on Figure 2 and Figure 8 From the luminescence spectrum, we can see that Li(Y 0.97 Er 0.03 ) 9 (SiO 4 ) 6 O 2 The powder sample was excited by a near-infrared 980nm laser, and the red light wavelength was 660nm with the maximum red light emission intensity. Compared with Example 1, there was a certain decrease, which verified that the increase in the amount of erbium ion doping in this example, although the physical phase remained unchanged, caused fluorescence quenching due to the high concentration of doping.

[0059] The above embodiments only express preferred implementation modes, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. A rare earth doped lithium yttrium silicate upconversion luminescent material, characterized in that: The structure of the up-conversion luminescent material is Li(Y 1-x Er x )9(SiO4)6O2, wherein x=0.005-0.03; The up-conversion luminescent material can generate strong red light emission with 660nm as the central wavelength under the irradiation of 980nm laser.

2. The rare earth doped lithium yttrium silicate upconversion luminescent material according to claim 1, characterized in that: The up-conversion luminescent material is composed of the elements Li, Si, Y and Er in a molar ratio of 1:6:9-9x:9x, and corresponding lithium carbonate, silicon dioxide, yttrium oxide and erbium oxide are weighed as raw materials; wherein x=0.005-0.

03.

3. A method for preparing a rare earth doped lithium yttrium silicate upconversion luminescent material as claimed in claim 1 or 2, characterized in that: The following steps are involved: Step 1: Weigh corresponding lithium carbonate, silicon dioxide, yttrium oxide and erbium oxide as raw materials in a molar ratio of 1:6:9-9x:9x of the elements Li, Si, Y and Er, wherein x=0.005-0.03; Step 2: Pour the raw materials weighed in step 1 into a container, add anhydrous ethanol, and stir thoroughly to obtain a uniform suspension; Step 3: The suspension is allowed to stand until the clear liquid and the precipitate are separated, and then dried to completely evaporate the anhydrous ethanol in the container to obtain a powder raw material; Step 4: Press the powdered raw material obtained in step 3 into a disc-shaped sample; Step 5: Place the disc-shaped sample obtained in step 4 into a furnace, raise the temperature to 1250°C to 1350°C for sintering; after sintering, naturally cool to room temperature, take out the sample, grind it into powder, and obtain a rare earth-doped lithium yttrium silicate up-conversion red light emitting material.

4. The method for preparing a rare earth doped lithium yttrium silicate upconversion luminescent material according to claim 3, characterized in that: In the step 2, the concentration of the suspension is 0.1-0.2 g of the raw material compound per ml of anhydrous ethanol.

5. The method for preparing a rare earth doped lithium yttrium silicate upconversion luminescent material according to claim 3, characterized in that: In the step 3, the drying temperature is 50° C. to 70° C., and the drying time is 10 hours to 12 hours.

6. The method for preparing a rare earth doped lithium yttrium silicate upconversion luminescent material according to claim 3, characterized in that: In the step 3, the standing time is 30 to 40 minutes.

7. The method for preparing a rare earth doped lithium yttrium silicate upconversion luminescent material according to claim 3, characterized in that: In the step 5, the temperature is kept within the range of 1250° C. to 1350° C. for 3 to 5 hours.

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