A three-layer core-shell structure rare earth up-conversion luminescent material, a preparation method and application thereof

Abstract

This invention provides a three-layer core-shell structured rare-earth upconversion luminescent material, its preparation method, and its application, relating to the field of luminescent material technology. This invention provides a three-layer core-shell structured rare-earth upconversion luminescent material with NaYF4:Er 3+ With NaYF4:Yb as the core 3+ The core-shell structure consists of an intermediate shell and a NaYF4 outer shell. This novel three-layer core-shell structure reduces surface defects and solves the problem of easy quenching. It exhibits strong single-band red light emission performance, and its upconversion luminescence performance is significantly improved compared to existing materials. It demonstrates excellent luminescence performance and good biological stability, and can be applied in fields such as biomedicine and infrared detection, providing a new material for further expanding its application in the field of luminescence.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, specifically to a three-layer core-shell structured rare-earth upconversion luminescent material, its preparation method, and its application. Background Technology

[0002] Rare-earth ion-doped upconversion micro / nano-luminescent materials have attracted widespread attention from researchers due to their unique luminescence properties, such as large Stokes shifts and narrow-band emission. In recent years, researchers have employed various methods, including ion co-doping techniques and the construction of core-shell structures, to enhance and control the upconversion luminescence intensity and spectral characteristics of these materials. For example, core-shell structures such as NaYF4:Gd / Tm / Er@CdTe, NaYF4:Er / Yb / Gd@NaGdF4, and NaYF4:Er / Yb@NaGdF4 have been reported. However, the presence of surface defects in these luminescent materials leads to their quenching tendency. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a three-layer core-shell structured rare-earth upconversion luminescent material, its preparation method, and its application. The three-layer core-shell structured rare-earth upconversion luminescent material provided by this invention can reduce surface defects and is less prone to quenching.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a three-layer core-shell structured rare-earth upconversion luminescent material, having a core-middle-shell-outer shell structure, with NaYF4:Er 3+ With NaYF4:Yb as the core 3+ It has an intermediate shell and an outer shell of NaYF4.

[0006] Preferably, the NaYF4:Er 3+ and NaYF4:Yb 3+ The molar content of Er in the medium is 1-10%.

[0007] Preferably, the NaYF4:Er 3+ and NaYF4:Yb 3+ The molar content of Yb in the medium is 10-19%.

[0008] Preferably, the core has a thickness of 60–70 nm, the intermediate shell has a thickness of 5–10 nm, and the outer shell has a thickness of 5–10 nm.

[0009] This invention also provides a method for preparing the three-layer core-shell structured rare-earth upconversion luminescent material described in the above technical solution, comprising the following steps:

[0010] (1) Add NaOH aqueous solution, oleic acid, ethanol, yttrium source, ytterbium source, NaF and NaYF4:Er 3+ Nanomaterials are mixed and subjected to a solvothermal reaction in NaYF4:Er 3+ NaYF4:Yb is formed on the surface of nanomaterials 3+ Layer, to obtain NaYF4:Er 3+ @NaYF4:Yb 3+ ;

[0011] (2) Add NaOH aqueous solution, oleic acid, ethanol, yttrium source, NaF and NaYF4:Er 3+ @NaYF4:Yb 3+ Mix and undergo a solvothermal reaction in NaYF4:Er 3+ @NaYF4:Yb 3+ A NaYF4 layer is formed on the surface to obtain the three-layer core-shell structured rare-earth upconversion luminescent material.

[0012] Preferably, in step (1), the NaF and NaYF4:Er 3+ The molar ratio of nanomaterials is 1:1 to 2;

[0013] The molar ratio of NaOH in the NaF and NaOH aqueous solution is 1:0.4-6; the concentration of the NaOH aqueous solution is 0.2-0.5 g / mL.

[0014] The molar ratio of NaF to yttrium in the yttrium source is 1:0.1-2; the yttrium source includes yttrium oxide and / or yttrium salt.

[0015] The molar ratio of ytterbium in the NaF and ytterbium source is 1:0.02 to 0.5; the ytterbium source includes ytterbium oxide and / or ytterbium salt.

[0016] The molar ratio of NaF to the volume of ethanol is 1 mmol: 1.25–2 mL;

[0017] The molar ratio of NaF to the volume of oleic acid is 1 mmol: 2.5–5 mL;

[0018] The solvothermal reaction is carried out at a temperature of 180–200°C for 8–10 hours and at a pressure of 2–3 MPa.

[0019] Preferably, in step (2), the NaF and NaYF4:Er 3+ @NaYF4:Yb 3+ The molar ratio is 1:1 to 2;

[0020] The molar ratio of NaOH in the NaF and NaOH aqueous solution is 1:0.4-6; the concentration of the NaOH aqueous solution is 0.2-0.5 g / mL.

[0021] The molar ratio of NaF to yttrium in the yttrium source is 1:0.1-2; the yttrium source includes yttrium oxide and / or yttrium salt.

[0022] The molar ratio of NaF to the volume of ethanol is 1 mmol: 1.25–2 mL;

[0023] The molar ratio of NaF to the volume of oleic acid is 1 mmol: 2.5–5 mL;

[0024] The solvothermal reaction is carried out at a temperature of 180–200°C for 8–10 hours and at a pressure of 2–3 MPa.

[0025] Preferably, the NaYF4:Er 3+ The preparation method of nanomaterials includes the following steps:

[0026] A solvothermal reaction was carried out with NaOH aqueous solution, oleic acid, ethanol, yttrium source, erbium source, and NaF to obtain NaYF4:Er 3+ Nanomaterials.

[0027] Preferably, the molar ratio of NaOH in the NaF and NaOH aqueous solution is 1:0.4-6; and the concentration of the NaOH aqueous solution is 0.2-0.5 g / mL.

[0028] The molar ratio of NaF to yttrium in the yttrium source is 1:0.1-2; the yttrium source includes yttrium oxide and / or yttrium salt.

[0029] The molar ratio of NaF to erbium in the erbium source is 1:0.004 to 0.1; the erbium source includes erbium oxide and / or erbium salt.

[0030] The molar ratio of NaF to the volume of ethanol is 1 mmol: 1.25–2 mL;

[0031] The molar ratio of NaF to the volume of oleic acid is 1 mmol: 2.5–5 mL;

[0032] The solvothermal reaction is carried out at a temperature of 180–200°C for 8–10 hours and at a pressure of 2–3 MPa.

[0033] This invention also provides the application of the three-layer core-shell structure rare earth upconversion luminescent material described in the above technical solution or the three-layer core-shell structure rare earth upconversion luminescent material prepared by the preparation method described in the above technical solution in infrared detection or in the preparation of biomedical materials.

[0034] This invention provides a three-layer core-shell structured rare-earth upconversion luminescent material (denoted as NaYF4:Er). 3+ @NaYF4:Yb 3 + @NaYF4), has a core-intermediate-shell-outer shell structure, with NaYF4:Er 3+ With NaYF4:Yb as the core 3+ The intermediate shell is NaYF4, and the outer shell is NaYF4. This invention uses NaYF4:Er... 3+ Nucleus and NaYF4:Yb 3+ The intermediate shell acts as a sensitizing layer, utilizing the active NaYF4:Yb 3+ Intermediate shell and core NaYF4:Er 3+ The organic combination of Yb in the sensitization layer 3+ Er ions into the host lattice 3+ Interfacial energy transfer between them further improves Er 3+ The red and green light emission intensities of the ions are influenced by the outer shell NaYF4, which reduces surface defects. This novel three-layer core-shell structure reduces surface defects, solves the problem of easy quenching, and exhibits strong single-band red light emission. The upconversion luminescence performance is significantly improved compared to existing materials, providing a new material for further expanding its applications in the field of luminescence. The three-layer core-shell rare-earth upconversion luminescent material provided by this invention exhibits excellent luminescence performance and good biological stability, and can be applied in fields such as biomedicine and infrared detection.

[0035] This invention explores the optimal enhancement structure system and ion doping concentration by effectively comparing the upconversion emission spectral intensities of different structures. Attached Figure Description

[0036] Figure 1 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ Transmission electron microscope image of @NaYF4;

[0037] Figure 2 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ Transmission electron microscope image;

[0038] Figure 3 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ Transmission electron microscope image of @NaYF4;

[0039] Figure 4NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ Upconversion luminescence spectrum of @NaYF4;

[0040] Figure 5 NaYF4:Er prepared in Examples 1-6 3+ @NaYF4:Yb 3+ Upconversion luminescence spectrum of @NaYF4;

[0041] Figure 6 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ @NaYF4 and NaYF4:Er@NaYF4:Yb and NaYF4:Er prepared in Comparative Example 1 3+ / Yb 3+ Upconversion luminescence spectrum of nanoparticles;

[0042] Figure 7 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ Quantum yield plot of @NaYF4;

[0043] Figure 8 NaYF4:Er prepared for Comparative Example 1 3+ / Yb 3+ Quantum yield graph;

[0044] Figure 9 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ @NaYF4 and NaYF4:Er@NaYF4:Yb and NaYF4:Er prepared in Comparative Example 1 3+ / Yb 3+ XRD pattern of nanoparticles. Detailed Implementation

[0045] This invention provides a three-layer core-shell structured rare-earth upconversion luminescent material, having a core-middle-shell-outer shell structure, with NaYF4:Er 3+ With NaYF4:Yb as the core 3+ It has an intermediate shell and an outer shell of NaYF4.

[0046] In this invention, the NaYF4:Er 3+ and NaYF4:Yb 3+ The molar content of Er element is preferably 1 to 10, and in specific embodiments it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0047] In this invention, the NaYF4:Er 3+ and NaYF4:Yb 3+ The molar content of Yb is preferably 10-19%, and in specific embodiments it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0048] In this invention, the NaYF4:Er 3+ and NaYF4:Yb 3+ The total molar content of Er and Yb elements is preferably 20%.

[0049] In this invention, the thickness of the core is preferably 60-75 nm, and in specific embodiments it can be 60 nm, 62 nm, 65 nm, 68 nm or 70 nm.

[0050] In this invention, the thickness of the intermediate shell is preferably 5-10 nm, and in specific embodiments it can be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm. In this invention, the mass ratio of the core to the intermediate shell is preferably 10-15:1, and in specific embodiments it can be 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1.

[0051] In this invention, the thickness of the outer shell layer is 5–10 nm, and in specific embodiments it can be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm. In this invention, the mass ratio of the core to the intermediate shell layer is preferably 10–15:1, and in specific embodiments it can be 10:1, 11:1, 12:1, 13:1, 14:1, or 15:1.

[0052] In this invention, the three-layer core-shell structured rare-earth upconversion luminescent material is preferably a nanorod structure.

[0053] This invention also provides a method for preparing the three-layer core-shell structured rare-earth upconversion luminescent material described in the above technical solution, comprising the following steps:

[0054] (1) Add NaOH aqueous solution, oleic acid, ethanol, yttrium source, ytterbium source, NaF and NaYF4:Er 3+ Nanomaterials are mixed and subjected to a solvothermal reaction in NaYF4:Er 3+ NaYF4:Yb is formed on the surface of nanomaterials 3+ Layer, to obtain NaYF4:Er 3+ @NaYF4:Yb 3+ ;

[0055] (2) Add NaOH aqueous solution, oleic acid, ethanol, yttrium source, NaF and NaYF4:Er 3+ @NaYF4:Yb 3+ Mix and undergo a solvothermal reaction in NaYF4:Er 3+ @NaYF4:Yb 3+ A NaYF4 layer is formed on the surface to obtain the three-layer core-shell structured rare-earth upconversion luminescent material.

[0056] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0057] The following section will first discuss NaYF4:Er 3+ The preparation methods of nanomaterials are described in detail.

[0058] In this invention, the NaYF4:Er 3+ The preferred method for preparing nanomaterials includes the following steps: reacting NaOH aqueous solution, oleic acid, ethanol, yttrium source, erbium source, and NaF in a solvothermal reaction to obtain NaYF4:Er 3+ Nanomaterials.

[0059] In this invention, the NaYF4:Er 3+ Nanomaterials preferably include NaYF4:Er 3+ Nanorods.

[0060] In this invention, the preferred molar ratio of NaF to NaOH in the aqueous NaOH solution is 1:0.4 to 6, and in specific embodiments it can be 1:0.4, 1:1, 1:1.5, 1:1.875, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, or 1:6. In this invention, the preferred concentration of the aqueous NaOH solution is 0.2 to 0.5 g / mL, and in specific embodiments it can be 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, or 0.5 g / mL.

[0061] In this invention, the molar ratio of NaF to yttrium in the yttrium source is preferably 1:0.1 to 2, and in specific embodiments it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2. In this invention, the yttrium source preferably includes yttrium oxide and / or yttrium salt; the yttrium oxide is preferably Y₂O₃; the yttrium salt preferably includes one or more of YF₃, YF₄, and Y(NO₃)·6H₂O.

[0062] In this invention, the molar ratio of NaF to erbium in the erbium source is preferably 1:0.004 to 0.1, and in specific embodiments it can be 1:0.004, 1:0.005, 1:0.008, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, or 1:0.1. In this invention, the erbium source preferably includes erbium oxide and / or erbium salt; the erbium oxide is preferably Er₂O₃; the erbium salt preferably includes one or more of ErF₃, ErF₄, and Er(NO₃)·5H₂O.

[0063] In this invention, the preferred ratio of the amount of NaF to the volume of ethanol is 1 mmol: 1.25 to 2 mL. In specific embodiments, it can be 1 mmol: 1.25 mL, 1 mmol: 1.3 mL, 1 mmol: 1.4 mL, 1 mmol: 1.5 mL, 1 mmol: 1.6 mL, 1 mmol: 1.7 mL, 1 mmol: 1.8 mL, 1 mmol: 1.9 mL, or 1 mmol: 2 mL.

[0064] In this invention, the preferred ratio of the amount of NaF to the volume of oleic acid is 1 mmol: 2.5 to 5 mL. In specific embodiments, it can be 1 mmol: 2.5 mL, 1 mmol: 3 mL, 1 mmol: 3.5 mL, 1 mmol: 4 mL, 1 mmol: 4.5 mL or 1 mmol: 5 mL.

[0065] In this invention, the mixing preferably includes: first stirring and mixing ethanol, oleic acid, and an aqueous NaOH solution to obtain a mixed solution; and second stirring and mixing the mixed solution with a yttrium source, an erbium source, and NaF to obtain a gel-like mixture. In this invention, the first stirring and mixing time is preferably 30–60 min, and in specific embodiments, it can be 30 min, 40 min, 50 min, or 60 min. In this invention, the second stirring and mixing time is preferably 30–60 min, and in specific embodiments, it can be 30 min, 40 min, 50 min, or 60 min. In this invention, the mixing temperature is preferably room temperature.

[0066] In this invention, the temperature of the solvothermal reaction is preferably 180–200°C, and in specific embodiments it can be 180°C, 185°C, 190°C, 195°C, or 200°C; the time of the solvothermal reaction is preferably 8–10 h, and in specific embodiments it can be 8 h, 8.5 h, 9 h, 9.5 h, or 10 h; the pressure of the solvothermal reaction is preferably 2–3 MPa, and in specific embodiments it can be 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, or 3 MPa; the solvothermal reaction is preferably carried out in a stainless steel high-pressure reactor.

[0067] After the solvothermal reaction is completed, the present invention preferably further includes: performing solid-liquid separation on the reaction system obtained from the solvothermal reaction, washing the obtained solid component with ethanol and drying it to obtain NaYF4:Er 3+ Nanomaterials. In this invention, the number of ethanol washing cycles is preferably 3 to 5, and in specific embodiments, it can be 3, 4, or 5 times. In this invention, the drying temperature is preferably 60 to 80°C, and in specific embodiments, it can be 60°C, 65°C, 70°C, 75°C, or 80°C; the drying time is preferably 6 to 8 hours, and in specific embodiments, it can be 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours.

[0068] This invention utilizes NaOH aqueous solution, oleic acid, ethanol, yttrium source, ytterbium source, NaF, and NaYF4:Er 3+ Nanomaterials are mixed and subjected to a solvothermal reaction in NaYF4:Er 3+ NaYF4:Yb is formed on the surface of nanomaterials 3+ Layer, to obtain NaYF4:Er 3+ @NaYF4:Yb 3+ .

[0069] In this invention, the NaF and NaYF4:Er 3+ The preferred molar ratio of the nanomaterials is 1:1 to 2, and in specific embodiments it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.

[0070] In this invention, the preferred molar ratio of NaF to NaOH in the aqueous NaOH solution is 1:0.4 to 6, and in specific embodiments it can be 1:0.4, 1:1, 1:1.5, 1:1.875, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, or 1:6. In this invention, the preferred concentration of the aqueous NaOH solution is 0.2 to 0.5 g / mL, and in specific embodiments it can be 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, or 0.5 g / mL.

[0071] In this invention, the molar ratio of NaF to yttrium in the yttrium source is preferably 1:0.1 to 2, and in specific embodiments it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2. In this invention, the yttrium source preferably includes yttrium oxide and / or yttrium salt; the yttrium oxide is preferably Y₂O₃; the yttrium salt preferably includes YF₃, YF₄, and / or Y(NO₃)·6H₂O.

[0072] In this invention, the molar ratio of NaF to ytterbium in the ytterbium source is preferably 1:0.02 to 0.5, and in specific embodiments it can be 1:0.02, 1:0.04, 1:0.045, 1:0.05, 1:0.8, 1:0.1, 1:0.2, 1:0.3, 1:0.4, or 1:0.5. In this invention, the ytterbium source preferably includes one or more of ytterbium oxide, ytterbium fluoride, and ytterbium salt; the ytterbium oxide is preferably Yb₂O₃; the ytterbium salt preferably includes YbF₃ and / or Yb(NO₃)·5H₂O.

[0073] In this invention, the preferred ratio of the amount of NaF to the volume of ethanol is 1 mmol: 1.25 to 2 mL. In specific embodiments, it can be 1 mmol: 1.25 mL, 1 mmol: 1.3 mL, 1 mmol: 1.4 mL, 1 mmol: 1.5 mL, 1 mmol: 1.6 mL, 1 mmol: 1.7 mL, 1 mmol: 1.8 mL, 1 mmol: 1.9 mL, or 1 mmol: 2 mL.

[0074] In this invention, the preferred ratio of the amount of NaF to the volume of oleic acid is 1 mmol: 2.5 to 5 mL. In specific embodiments, it can be 1 mmol: 2.5 mL, 1 mmol: 3 mL, 1 mmol: 3.5 mL, 1 mmol: 4 mL, 1 mmol: 4.5 mL or 1 mmol: 5 mL.

[0075] In this invention, the temperature of the solvothermal reaction is preferably 180–200°C, and in specific embodiments it can be 180°C, 185°C, 190°C, 195°C, or 200°C; the time of the solvothermal reaction is preferably 8–10 h, and in specific embodiments it can be 8 h, 8.5 h, 9 h, 9.5 h, or 10 h; the pressure of the solvothermal reaction is preferably 2–3 MPa, and in specific embodiments it can be 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, or 3 MPa; the solvothermal reaction is preferably carried out in a stainless steel high-pressure reactor.

[0076] In this invention, the mixing preferably includes: a third stirring and mixing of ethanol, oleic acid, and an aqueous NaOH solution to obtain a mixture; a fourth stirring and mixing of the mixture with a yttrium source, a ytterbium source, and NaF; and then mixing with NaYF4:Er. 3+ The nanomaterials are stirred and mixed a fifth time to obtain a gel-like mixture. In this invention, the third stirring and mixing time is preferably 30-60 minutes, and in specific embodiments, it can be 30 minutes, 40 minutes, 50 minutes, or 60 minutes. In this invention, the fourth stirring and mixing time is preferably 30-60 minutes, and in specific embodiments, it can be 30 minutes, 40 minutes, 50 minutes, or 60 minutes. In this invention, the mixing temperature is preferably room temperature.

[0077] After the solvothermal reaction is completed, the present invention preferably further includes: performing solid-liquid separation on the reaction system obtained from the solvothermal reaction, washing the obtained solid component with ethanol and drying it to obtain NaYF4:Er 3+ @NaYF4:Yb 3+ In this invention, the ethanol washing is preferably performed three times. In this invention, the drying temperature is preferably 80°C; the drying time is preferably 6 hours.

[0078] We obtained NaYF4:Er 3+ @NaYF4:Yb 3+ Subsequently, this invention uses NaOH aqueous solution, oleic acid, ethanol, yttrium source, NaF and NaYF4:Er 3+ @NaYF4:Yb 3+ Mix and undergo a solvothermal reaction in NaYF4:Er 3+ @NaYF4:Yb 3+A NaYF4 layer is formed on the surface to obtain the three-layer core-shell structured rare-earth upconversion luminescent material.

[0079] In this invention, the NaF and NaYF4:Er 3+ @NaYF4:Yb 3+ The preferred molar ratio is 1:1 to 2, and in specific embodiments it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2;

[0080] In this invention, the preferred molar ratio of NaF to NaOH in the aqueous NaOH solution is 1:0.4 to 6, and in specific embodiments it can be 1:0.4, 1:1, 1:1.5, 1:1.875, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, or 1:6. In this invention, the preferred concentration of the aqueous NaOH solution is 0.2 to 0.5 g / mL, and in specific embodiments it can be 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, or 0.5 g / mL.

[0081] In this invention, the molar ratio of NaF to yttrium in the yttrium source is preferably 1:0.1 to 2, and in specific embodiments it can be 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2. In this invention, the yttrium source preferably includes yttrium oxide and / or yttrium salt; the yttrium oxide is preferably Y₂O₃; the yttrium salt preferably includes one or more of YF₃, YF₄, and Y(NO₃)·6H₂O.

[0082] In this invention, the preferred ratio of the amount of NaF to the volume of ethanol is 1 mmol: 1.25 to 2 mL. In specific embodiments, it can be 1 mmol: 1.25 mL, 1 mmol: 1.3 mL, 1 mmol: 1.4 mL, 1 mmol: 1.5 mL, 1 mmol: 1.6 mL, 1 mmol: 1.7 mL, 1 mmol: 1.8 mL, 1 mmol: 1.9 mL, or 1 mmol: 2 mL.

[0083] In this invention, the preferred ratio of the amount of NaF to the volume of oleic acid is 1 mmol: 2.5 to 5 mL. In specific embodiments, it can be 1 mmol: 2.5 mL, 1 mmol: 3 mL, 1 mmol: 3.5 mL, 1 mmol: 4 mL, 1 mmol: 4.5 mL or 1 mmol: 5 mL.

[0084] In this invention, the mixing preferably includes: a sixth stirring and mixing of ethanol, oleic acid, and an aqueous NaOH solution to obtain a mixture; a seventh stirring and mixing of the mixture with a yttrium source and NaF; and then mixing with NaYF4:Er. 3+ @NaYF4:Yb 3+ The eighth stirring and mixing step yields a gel-like mixture. In this invention, the sixth stirring and mixing time is preferably 30-60 minutes, and in specific embodiments, it can be 30 minutes, 40 minutes, 50 minutes, or 60 minutes. In this invention, the seventh stirring and mixing time is preferably 30-60 minutes, and in specific embodiments, it can be 30 minutes, 40 minutes, 50 minutes, or 60 minutes. In this invention, the eighth stirring and mixing time is preferably 30-60 minutes, and in specific embodiments, it can be 30 minutes, 40 minutes, 50 minutes, or 60 minutes. In this invention, the mixing temperature is preferably room temperature.

[0085] In this invention, the temperature of the solvothermal reaction is preferably 180–200°C, and in specific embodiments it can be 180°C, 185°C, 190°C, 195°C, or 200°C; the time of the solvothermal reaction is preferably 8–10 h, and in specific embodiments it can be 8 h, 8.5 h, 9 h, 9.5 h, or 10 h; the pressure of the solvothermal reaction is preferably 2–3 MPa, and in specific embodiments it can be 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, or 3 MPa; the solvothermal reaction is preferably carried out in a stainless steel high-pressure reactor.

[0086] After completing the solvothermal reaction, the present invention preferably further includes: performing solid-liquid separation on the reaction system obtained from the solvothermal reaction, washing the obtained solid component with ethanol and then drying it to obtain a three-layer core-shell structured rare-earth upconversion luminescent material. In the present invention, the ethanol washing is preferably performed three times. In the present invention, the drying temperature is preferably 80°C; the drying time is preferably 6 hours.

[0087] This invention also provides the application of the three-layer core-shell structured rare-earth upconversion luminescent material described in the above-described technical solutions, or the three-layer core-shell structured rare-earth upconversion luminescent material prepared by the above-described preparation methods, in infrared detection or the preparation of biomedical materials. The three-layer core-shell structured rare-earth upconversion luminescent material provided by this invention exhibits excellent luminescent properties and good biological stability, and can be applied in fields such as biomedicine and infrared detection. The three-layer core-shell structured rare-earth upconversion luminescent material provided by this invention provides important experimental reference for related research on constructing materials with excellent single-band red light emission, and provides a new approach for further broadening the single-band red light emission of rare-earth fluorides.

[0088] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of the three-layer core-shell structured rare-earth upconversion luminescent material, its preparation method, and its applications, should not be construed as limiting the scope of protection of the present invention.

[0089] In the following examples and comparative examples, the purity of YNO3·6H2O, ErNO3·6H2O, and Yb(NO3)3·5H2O was 99.9%, and the purity of other raw materials was above analytical grade.

[0090] Example 1

[0091] (1) NaYF4:Er 3+ Preparation of nanorods

[0092] At room temperature, 10 mL of ethanol and 20 mL of oleic acid were added to 3 mL of 0.2 g / mL NaOH aqueous solution and stirred for 30 min to obtain a transparent mixture. Then, 1.6 mmol Y(NO3)3·6H2O, 0.04 mmol Er(NO3)3·5H2O, and 8 mmol NaF were added and stirred for 30 min. The resulting gel-like mixture was transferred to a stainless steel high-pressure reactor and heated at 160 °C for 10 h to separate the solid and liquid phases. The resulting solid component was washed three times with ethanol and dried at 80 °C for 6 h to obtain NaYF4:Er 3+ Nanorods.

[0093] (2) Preparation of NaYF4:Er@NaYF4:Yb with nano-core-shell structure

[0094] At room temperature, 10 mL of ethanol and 20 mL of oleic acid were added to 3 mL of 0.2 g / mL NaOH aqueous solution and stirred for 30 min to obtain a transparent mixture. Then, 1.6 mmol Y(NO3)3·6H2O, 0.36 mmol Yb(NO3)3·5H2O, and 8 mmol NaF were added and stirred for 30 min. Finally, NaYF4:Er prepared in step (1) was added. 3+Nanorods were stirred for another 30 minutes. The resulting gel-like mixture was then transferred to a stainless steel high-pressure reactor and heated at 160°C for 10 hours. Solid-liquid separation was performed, and the resulting solid component was washed three times with ethanol and dried at 80°C for 6 hours to obtain NaYF4:Er@NaYF4:Yb with a nano-core-shell structure.

[0095] (3) Rare earth conversion nanoluminescent materials with a three-layer core-shell structure (NaYF4:Er) 3+ @NaYF4:Yb 3+ Preparation of @NaYF4)

[0096] At room temperature, 10 mL of ethanol and 20 mL of oleic acid were added to 3 mL of 0.2 g / mL NaOH aqueous solution and stirred for 30 min to obtain a transparent mixture. 1.6 mmol Y(NO3)3·6H2O and 8 mmol NaF were added and stirred for 30 min. Then, NaYF4:Er@NaYF4:Yb prepared in step (1) was added and stirred for another 30 min. The resulting gel-like mixture was transferred to a stainless steel high-pressure reactor and heated at 160 °C for 10 h to separate the solid and liquid phases. The obtained solid component was washed three times with ethanol and dried at 80 °C for 6 h to obtain NaYF4:Er with a core-middle shell-outer shell structure. 3+ @NaYF4:Yb 3+ @NaYF4 (i.e., NaYF4:0.02Er) 3+ @NaYF4:0.18Yb 3+ @NaYF4, 0.02 means Er 3+ The molar percentage of Yb in the core and intermediate shell is 2%, and 0.18 represents Yb. 3+ The molar percentage of the core and intermediate shell is 18%.

[0097] Example 2

[0098] NaYF4:Er was prepared according to the method in Example 1. 3+ @NaYF4:Yb 3+ @NaYF4 differs from Example 1 only in that the amount of Er(NO3)3·5H2O is 0.02 mmol and the amount of Yb(NO3)3·5H2O is 0.38 mmol, resulting in NaYF4:0.01Er 3 + @NaYF4:0.19Yb 3+ @NaYF4.

[0099] Example 3

[0100] NaYF4:Er was prepared according to the method in Example 1. 3+ @NaYF4:Yb3+ @NaYF4 differs from Example 1 only in that the amount of Er(NO3)3·5H2O is 0.08 mmol and the amount of Yb(NO3)3·5H2O is 0.32 mmol, resulting in NaYF4:0.04Er 3 + @NaYF4:0.16Yb 3+ @NaYF4.

[0101] Example 4

[0102] NaYF4:Er was prepared according to the method in Example 1. 3+ @NaYF4:Yb 3+ @NaYF4 differs from Example 1 only in that the amount of Er(NO3)3·5H2O is 0.12 mmol and the amount of Yb(NO3)3·5H2O is 0.28 mmol, resulting in NaYF4:0.06Er 3 + @NaYF4:0.14Yb 3+ @NaYF4.

[0103] Example 5

[0104] NaYF4:Er was prepared according to the method in Example 1. 3+ @NaYF4:Yb 3+ @NaYF4 differs from Example 1 only in that the amount of Er(NO3)3·5H2O is 0.2 mmol, and the amount of Yb(NO3)3·5H2O is 0.2 mmol, resulting in NaYF4:0.1Er 3+ @NaYF4:0.1Yb 3+ @NaYF4.

[0105] Comparative Example 1

[0106] NaYF4:Er without core-shell structure 3+ / Yb 3+ Preparation of nanoparticles

[0107] At room temperature, 10 mL of ethanol and 20 mL of oleic acid were added to 3 mL of 0.2 g / mL NaOH aqueous solution and stirred for 30 min to obtain a transparent mixture. Then, 1.6 mmol Y(NO3)3·6H2O, 0.04 mmol Er(NO3)3·5H2O, 0.36 mmol Yb(NO3)3·5H2O, and 8 mmol NaF were added and stirred for 30 min. The resulting gel-like mixture was transferred to a stainless steel high-pressure reactor and heated at 160 °C for 10 h to separate the solid and liquid phases. The resulting solid component was washed three times with ethanol and dried at 80 °C for 6 h to obtain core-shell-free NaYF4:Er 3+ / Yb 3+ (NaYF4:0.02Er 3+ / 0.18Yb 3+ Nanoparticles.

[0108] Figures 1-3 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ The transmission electron microscope image of @NaYF4 shows that NaYF4:Er 3+ @NaYF4:Yb 3+ @NaYF4 exhibits a nanorod-like structure; NaYF4:Er 3+ @NaYF4:Yb 3+ The thickness of the NaYF4 rod is approximately 75nm, and the core is NaYF4:Er. 3+ The thickness is approximately 65 nm, with the middle layer being NaYF4:Yb. 3+ The thickness of the outer layer is approximately 5 nm, and the thickness of the outer shell layer NaYF4 is approximately 5 nm.

[0109] Using an external 980nm laser as the light source, the NaYF4:Er prepared in Example 1 was subjected to [further treatment]. 3+ , NaYF4:Er@NaYF4:Yb and NaYF4:Er 3+ @NaYF4:Yb 3+ Fluorescence emission spectroscopy was performed on @NaYF4.

[0110] Figure 4 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ The upconversion emission spectrum of NaYF4 shows that NaYF4:Er 3+ @NaYF4:Yb 3+ In @NaYF4, Er emits green light in the 510–560 nm range, and the energy level transition at 530 nm is... 2 H 11 / 2 - 4 I15 / 2 , the energy level transition corresponding to 540 nm is 4 S 3 / 2 - 4 I 15 / 2 , and the red emission is at 635 - 680 nm, with the corresponding energy level transition being 4 F 9 / 2 - 4 I 15 / 2 .

[0111] Figure 5 The up - conversion luminescence spectra of NaYF4:Er 3+ @NaYF4:Yb 3+ @NaYF4 prepared in Examples 1 - 6, where the total molar mass ratio of Er 3+ and Yb 3+ is 20% and remains constant all the time ， When Er 3+ is 0.02, its proportion is 10%, and when Er 3+ is 0.1, its proportion is 50%; it can be seen that in NaYF4:Er 3+ @NaYF4:Yb 3+ @NaYF4, when the content of Er 3+ ions increases from 10% to 50%, its up - conversion luminescence intensities at red and green lights are significantly much greater than those of NaYF4:Er 3+ / Yb 3+ , and even when the content of Er 3+ increases to 50%, no obvious concentration quenching occurs.

[0112] Figure 6 The up - conversion luminescence spectra of NaYF4:Er 3+ @NaYF4:Yb 3+ @NaYF4 prepared in Example 1, NaYF4:Er 3+ @NaYF4:Yb 3+ and the up - conversion luminescence spectra of NaYF4:Er 3+ / Yb 3+ nanoparticles prepared in Comparative Example 1. It can be seen that the up - conversion luminescence intensity of NaYF4:Er 3+ @NaYF4:Yb 3 + @NaYF4 is greater than that of NaYF4:Er 3+ @NaYF4:Yb 3+ , because the outermost NaYF4 effectively reduces surface defects or non - radiative energy transfer between rare - earth ions and surface functional groups of NaYF4:Er 3+ @NaYF4:Yb 3+ nanorods. NaYF4:Er3+ @NaYF4:Yb 3+ The upconversion luminescence intensity is higher than that of NaYF4:Er 3+ / Yb 3+ Nanoparticles, primarily attributed to NaYF4:Er 3+ @NaYF4:Yb 3+ Yb in nanorods 3+ To Er 3+ Energy transfer at the interface.

[0113] Figure 7 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ Fluorescence quantum yield plot of @NaYF4 Figure 8 NaYF4:Er prepared for Comparative Example 1 3+ / Yb 3+ The fluorescence quantum yield diagrams of the nanoparticles, as shown in Figures 7 and 8, reveal distinct green (approximately 517–563 nm) and red (approximately 640–675 nm) regions under 980 nm laser excitation. The quantum yield is calculated as the integral region of the emitted light divided by the integral region of the excitation light. NaYF4:Er 3+ @NaYF4:Yb 3+ The fluorescence quantum yield of @NaYF4 was 4.26%. ， NaYF4:Er 3+ / Yb 3+ The fluorescence quantum yield of the nanoparticles was 1.82%.

[0114] Figure 9 NaYF4:Er prepared in Example 1 3+ @NaYF4:Yb 3+ @NaYF4 and NaYF4:Er@NaYF4:Yb and NaYF4:Er prepared in Comparative Example 1 3+ / Yb 3+ The XRD pattern of the nanoparticles shows that NaYF4:Er 3+ @NaYF4:Yb 3+ @NaYF4 and NaYF4:Er 3+ @NaYF4:Yb 3+ NaYF4:Er prepared in Comparative Example 1 3+ / Yb 3+ The main diffraction peaks of the nanoparticles are consistent and correspond one-to-one with the crystal phase of the hexagonal NaYF4 standard card JCPDS NO28-1192, which indirectly proves the successful synthesis of NaYF4:Er 3 + @NaYF4:Yb 3+@NaYF4、NaYF4:Er 3+ @NaYF4:Yb 3+ and NaYF4:Er 3+ / Yb 3+ Nanoparticles.

[0115] 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 three-layer core-shell structured rare-earth upconversion luminescent material, having a core-middle-shell-outer shell structure, with NaYF4:Er 3+ With NaYF4:Yb as the core 3+ It has an intermediate shell and a NaYF4 outer shell. The NaYF4:Er 3+ NaYF4:Er 3+ Nanorods; The NaYF4:Er 3+ and NaYF4:Yb 3+ The molar content of Er element in the medium is 1-10%; The NaYF4:Er 3+ and NaYF4:Yb 3+ The molar content of Yb in the medium is 10~19%.

2. The three-layer core-shell structured rare-earth upconversion luminescent material according to claim 1, characterized in that, The core has a thickness of 60-70 nm, the intermediate shell has a thickness of 5-10 nm, and the outer shell has a thickness of 5-10 nm.

3. A method for preparing the three-layer core-shell structured rare-earth upconversion luminescent material according to any one of claims 1 to 2, comprising the following steps: (1) Add NaOH aqueous solution, oleic acid, ethanol, yttrium source, ytterbium source, NaF and NaYF4:Er 3+ Nanomaterials are mixed and subjected to a solvothermal reaction in NaYF4:Er 3+ NaYF4:Yb is formed on the surface of nanoparticles 3+ Layer, to obtain NaYF4:Er 3+ @NaYF4:Yb 3+ ; (2) Add NaOH aqueous solution, oleic acid, ethanol, yttrium source, NaF and NaYF4:Er 3+ @NaYF4:Yb 3+ Mix and undergo a solvothermal reaction in NaYF4:Er 3+ @NaYF4:Yb 3+ A NaYF4 layer is formed on the surface to obtain the three-layer core-shell structured rare-earth upconversion luminescent material.

4. The preparation method according to claim 3, characterized in that, In step (1), the NaF and NaYF4:Er 3+ The molar ratio of nanomaterials is 1:1~2; The molar ratio of NaOH in the NaF and NaOH aqueous solution is 1:0.4~6; the concentration of the NaOH aqueous solution is 0.2~0.5 g / mL; The molar ratio of NaF to yttrium in the yttrium source is 1:0.1~2; the yttrium source includes yttrium oxide and / or yttrium salt; The molar ratio of ytterbium in the NaF and ytterbium source is 1:0.02~0.5; the ytterbium source includes ytterbium oxide and / or ytterbium salt; The molar ratio of NaF to the volume of ethanol is 1 mmol: 1.25~2 mL; The molar ratio of NaF to the volume of oleic acid is 1 mmol: 2.5~5 mL; The solvothermal reaction is carried out at a temperature of 180-200℃ for 8-10 hours and at a pressure of 2-3 MPa.

5. The preparation method according to claim 3, characterized in that, In step (2), the NaF and NaYF4:Er 3+ @NaYF4:Yb 3+ The molar ratio is 1:1~2; The molar ratio of NaOH in the NaF and NaOH aqueous solution is 1:0.4~6; the concentration of the NaOH aqueous solution is 0.2~0.5 g / mL; The molar ratio of NaF to yttrium in the yttrium source is 1:0.1~2; the yttrium source includes yttrium oxide and / or yttrium salt; The molar ratio of NaF to the volume of ethanol is 1 mmol: 1.25~2 mL; The molar ratio of NaF to the volume of oleic acid is 1 mmol: 2.5~5 mL; The solvothermal reaction is carried out at a temperature of 180-200℃ for 8-10 hours and at a pressure of 2-3 MPa.

6. The preparation method according to claim 3 or 4, characterized in that, The NaYF4:Er 3+ The preparation method of nanomaterials includes the following steps: A solvothermal reaction was carried out with NaOH aqueous solution, oleic acid, ethanol, yttrium source, erbium source, and NaF to obtain NaYF4:Er 3+ Nanomaterials.

7. The preparation method according to claim 6, characterized in that, The molar ratio of NaOH in the NaF and NaOH aqueous solution is 1:0.4~6; the concentration of the NaOH aqueous solution is 0.2~0.5 g / mL; The molar ratio of NaF to yttrium in the yttrium source is 1:0.1~2; the yttrium source includes yttrium oxide and / or yttrium salt; The molar ratio of NaF to erbium in the erbium source is 1:0.004~0.1; the erbium source includes erbium oxide and / or erbium salt; The molar ratio of NaF to the volume of ethanol is 1 mmol: 1.25~2 mL; The molar ratio of NaF to the volume of oleic acid is 1 mmol: 2.5~5 mL; The solvothermal reaction is carried out at a temperature of 180-200℃ for 8-10 hours and at a pressure of 2-3 MPa.

8. The application of the three-layer core-shell structured rare earth upconversion luminescent material according to any one of claims 1 to 2 or the three-layer core-shell structured rare earth upconversion luminescent material prepared by the preparation method according to any one of claims 3 to 7 in infrared detection or preparation of biomedical materials.

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