NaYF4 type luminescent material as well as preparation method and application thereof

Abstract

The invention discloses a NaYF4 type luminescent material as well as a preparation method and application thereof. The preparation method comprises the following steps: reacting a raw material composition in a molten salt medium; wherein the raw material composition comprises a Y source, a Yb source, an Er source and a fluorinating agent, and the molten salt medium comprises nitrite, NaNO3 and KNO3. The preparation method is a one-step method, does not need an organic solvent or a surfactant, is simple and convenient to operate, is strong in red light up-conversion emission, and is suitable for large-scale production and application of a biological imaging system, sensing equipment, a lighting device or energy storage equipment and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a NaYF4 type luminescent material and a preparation method and application thereof. BACKGROUND

[0002] In recent years, rare earth doped upconversion luminescent materials have attracted extensive attention in the fields of biological imaging, therapy, sensing, lighting, solar cells, etc. due to their unique advantage that they can produce long-wavelength emission in the visible region by low-energy near-infrared excitation. In particular, in the field of biomedicine, the characteristics of upconversion luminescence make deep tissue biological imaging unnecessary to have visible autofluorescence from biological components such as tissues and blood, and avoid the phototoxicity related to traditional high-energy ultraviolet / visible light excitation. Among them, fluoride represented by NaYF4 is considered to be one of the most effective matrices for rare earth ion upconversion luminescence because of its high optical transparency and low phonon energy.

[0003] At present, the reported hexagonal (β phase) NaYF4:Yb 3+ ,Er 3+ Most of them are green-based multi-fluorescent emission, and have low biological tissue penetration ability and need high power density excitation. For biomedical applications involving tissue imaging, cubic (α phase) NaYF4:Yb 3+ ,Er 3+ which emits red light is an ideal imaging material, and its excitation and emission are both in the near-infrared biological window (about 650-1000 nm), which has minimal light absorption and scattering of biological tissues, strong penetration ability, and can be functionalized to achieve various applications.

[0004] The existing synthesis methods of α-NaYF4:Yb 3 +,Er 3+ mainly include hydrothermal method, coprecipitation method, etc. These methods all need to combine the use of a large amount of organic surfactants for multi-step reactions, which are prone to environmental hazards, complicated process and difficult to accurately control the reaction conditions, and are not conducive to realize large-scale production. Therefore, it is of great significance to develop a simple and efficient synthesis method of NaYF4 type luminescent material. SUMMARY

[0005] In order to overcome the shortcomings of the existing method for preparing NaYF4 type luminescent material, such as multiple synthesis steps, complicated process, easy phase conversion, product containing organic surface pollutants, and insufficient red light emission efficiency, etc., the present application provides a NaYF4 type luminescent material and a preparation method and application thereof. The preparation method of the present application is simple and controllable, can be free of organic solvents and surfactants, and through condition screening, pure cubic α phase nanocrystals can be stably obtained, and high-intensity red upconversion luminescence performance under 980 nm near-infrared excitation can be exhibited.

[0006] To achieve the object, the present application adopts the following technical solutions:

[0007] The present application provides a preparation method of NaYF4 type luminescent material, which comprises the following steps: reacting raw material composition in molten salt medium to obtain the NaYF4 type luminescent material.

[0008] The raw material composition comprises Y source, Yb source, Er source and fluorination agent, and the molten salt medium comprises nitrite, NaNO3 and KNO3.

[0009] In the present application, preferably, no organic solvent is used in the preparation method.

[0010] The organic solvent generally refers to an organic compound existing as a solvent or complexing agent in the high-temperature reaction stage, such as octadecene (ODE), ethylene glycol (EG), ethylenediaminetetraacetic acid (EDTA), sodium citrate (TSC), but does not include ethanol, acetone and other volatile grinding dispersants used for dispersion or grinding before reaction.

[0011] In the present application, preferably, no surfactant is used in the preparation method.

[0012] The surfactant generally refers to an organic compound used for coating the surface of the luminescent material, controlling the particle size and morphology, such as oleic acid (OA), dodecyl dimethyl benzyl ammonium chloride (DDBAC), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and other commonly used organic surfactants in the art.

[0013] In the present application, the Y source can be a Y-containing compound commonly used in the art. "Y" represents yttrium.

[0014] In some embodiments of the present application, the Y source comprises yttrium nitrate and / or yttrium fluoride, preferably yttrium nitrate, such as Y(NO3)3·6H2O.

[0015] In the present application, the Yb source can be a Yb-containing compound commonly used in the art. "Yb" represents ytterbium.

[0016] In some embodiments of the present application, the Yb source comprises ytterbium nitrate and / or ytterbium fluoride, preferably ytterbium nitrate, such as Yb(NO3)3·5H2O.

[0017] In the present application, the Er source can be an Er-containing compound commonly used in the art. "Er" represents erbium.

[0018] In some embodiments of the present application, the Er source comprises erbium nitrate and / or erbium fluoride, preferably erbium nitrate, such as Er(NO3)3·5H2O.

[0019] In some preferred embodiments of the present application, the source of Y is yttrium nitrate and / or yttrium fluoride, the source of Yb is ytterbium nitrate and / or ytterbium fluoride, and the source of Er is erbium nitrate and / or erbium fluoride.

[0020] In some specific embodiments of the present application, the source of Y is Y(NO3)3-6H2O, the source of Yb is Yb(NO3)3-5H2O, and the source of Er is Er(NO3)3-5H2O.

[0021] In the present application, the fluorinating agent can be a fluorine-containing compound conventionally used in the art.

[0022] In some embodiments of the present application, the fluorinating agent preferably comprises NH4F and / or NaF, more preferably NaF.

[0023] In the present application, the nitrite is preferably KNO2 and / or NaNO2, more preferably NaNO2.

[0024] In some preferred embodiments of the present application, the fluorinating agent is NH4F and / or NaF, and the nitrite is KNO2 and / or NaNO2.

[0025] In some more preferred embodiments of the present application, the fluorinating agent is NaF, and the nitrite is NaNO2.

[0026] In some specific embodiments of the present application, the source of Y is Y(NO3)3-6H2O, the source of Yb is Yb(NO3)3-5H2O, and the source of Er is Er(NO3)3-5H2O, the fluorinating agent is NaF, and the nitrite is NaNO2.

[0027] In the present application, the molar ratio of the source of Y, the source of Yb, the source of Er and the NaF is preferably (0.78-0.8):(0.18-0.2):0.02:(2-8), for example 0.8:0.18:0.02:4.

[0028] In some embodiments of the present application, the molar ratio of the source of Y, the source of Yb, the source of Er and the fluorinating agent is 0.8:0.18:0.02:4.

[0029] In the present application, preferably, the molar fraction of the nitrite in the molten salt medium is 1-50%, preferably 20%-50%, for example 1%, 5%, 10%, 30% or 40%.

[0030] In the present application, preferably, the molar fraction of the NaNO3 in the molten salt medium is 5%-60%, preferably 5%-10%, for example 7%.

[0031] In the present application, preferably, the molar fraction of KNO3 in the molten salt medium is 30%-75%, preferably 40%-75%, for example 53%.

[0032] In the present application, preferably, the molar ratio of the nitrite, NaNO3 and KNO3 is (1-50):(5-60):(30-75), preferably (20-50):(5-10):(40-75), for example 40:7:53.

[0033] In some preferred embodiments of the present application, the molten salt medium is composed of NaNO2, NaNO3 and KNO3. Among them, the molar ratio of NaNO2, NaNO3 and KNO3 is preferably 40:7:53. At this molar ratio, the molten salt medium has the lowest eutectic point.

[0034] In some embodiments of the present application, the molar ratio of the Y source, the Yb source, the Er source and the molten salt medium is preferably (0.78-0.8):(0.18-0.2):0.02:(25-100), preferably 0.8:0.18:0.02:(25-100), for example 0.8:0.18:0.02:25, 0.8:0.18:0.02:75, or 0.8:0.18:0.02:100.

[0035] In some embodiments of the present application, the molar ratio of the Y source, the Yb source, the Er source, the fluorination agent and the molten salt medium is (0.78-0.8):(0.18-0.2):0.02:(2-8):(25-100), preferably 0.8:0.18:0.02:4:(25-100), for example 0.8:0.18:0.02:4:25, 0.8:0.18:0.02:4:75, or 0.8:0.18:0.02:4:100.

[0036] In some specific embodiments of the present application, the molar ratio of the Y source, the Yb source, the Er source, the fluorination agent, NaNO2, NaNO3 and KNO3 is 0.8:0.18:0.02:4:40:7:53.

[0037] In the present application, the reaction is carried out in the molten state of the molten salt medium. The temperature of the reaction is generally not lower than the melting point of the molten salt medium.

[0038] When the molten salt in the molten salt medium is in a specific proportion, the molten salt medium has the lowest eutectic point. The reaction is preferably carried out at the lowest eutectic point.

[0039] In the present application, the temperature of the reaction is preferably 200-400℃, for example 200℃, 300℃ or 400℃.

[0040] In the present application, the reaction is generally carried out in an inert atmosphere. The inert atmosphere can be an atmosphere that does not participate in the reaction of the system, for example an argon atmosphere, as is conventionally understood in the art.

[0041] In the present application, the time of the reaction is preferably more than 1h, more preferably 1-10h, for example 1h, 5h or 10h.

[0042] In the present application, before the heating reaction, an operation of pretreating the raw material composition and the molten salt medium is generally also included.

[0043] In some embodiments of the present application, the pretreatment includes the following steps: after grinding the raw material composition, the molten salt medium and an auxiliary agent, the auxiliary agent is removed.

[0044] The auxiliary agent can be an easily volatile organic solvent, preferably ethanol.

[0045] The amount of the auxiliary agent is 30%-50% of the total mass of the raw material composition and the molten salt medium, preferably 40%.

[0046] In some embodiments of the present application, the grinding time is 15-30min, preferably 30min.

[0047] In some embodiments of the present application, the auxiliary agent is removed by heating to evaporate the auxiliary agent.

[0048] The heating is generally vacuum heating.

[0049] The temperature of the heating can be 70℃.

[0050] In the present application, after the reaction, an operation of post-treatment is generally also included. The post-treatment can be an operation of removing the molten salt medium conventionally in the art.

[0051] In some embodiments of the present application, the post-treatment includes washing, filtering, drying and grinding.

[0052] The washing preferably uses deionized water.

[0053] The filtering is preferably suction filtration.

[0054] The drying is preferably vacuum drying. The temperature of the drying is preferably 60-100℃, for example 60℃. The time of the drying is preferably 12-24h, for example 24h.

[0055] The application further provides the NaYF4 type luminescent material prepared by the method.

[0056] In some embodiments of the application, the average particle size of the NaYF4 type luminescent material is 30-70 nm, for example, 50 nm.

[0057] In some preferred embodiments of the application, the NaYF4 type luminescent material is cubic crystal structure.

[0058] In some preferred embodiments of the application, the average particle size of the NaYF4 type luminescent material is 30-70 nm, and the NaYF4 type luminescent material is pure cubic alpha phase nanocrystal.

[0059] In the application, the NaYF4 type luminescent material is generally up-conversion luminescent material.

[0060] The application further provides the use of the NaYF4 type luminescent material as described above in a biological imaging system, a sensing device, an illumination device or an energy storage device.

[0061] The positive progress effect of the application is that:

[0062] The application uses the molten salt method to prepare the NaYF4 type luminescent material, and the process steps are significantly simplified, and the reaction process is easy to control, so that the organic solvent and the surfactant can be avoided, and the organic pollution on the surface of the product can be avoided. At the same time, the raw material cost of the method is low, the process is simple and environmentally friendly, and the method is easy to scale production, and has significant industrial application value.

[0063] The NaYF4 type luminescent material prepared by the application has significantly improved red up-conversion fluorescence purity and luminescent intensity under 980 nm near-infrared excitation, and is more suitable for deep tissue imaging application.

[0064] In some preferred embodiments, the luminescent material crystal form obtained by the application is pure phase cubic crystal structure, the crystal form is stable, and the particle size is uniform. BRIEF DESCRIPTION OF DRAWINGS

[0065] Figure 1 The XRD pattern of the NaYF4 type luminescent material prepared in Example 1 of the application.

[0066] Figure 2 The XRD pattern of the NaYF4 type luminescent material prepared in Examples 7 and 8 of the application.

[0067] Figure 3 The XRD pattern of the NaYF4 type luminescent material prepared in Examples 9 and 10 of the application.

[0068] Figure 4XRD pattern of NaYF4 type luminescent material prepared for Example 1 of the present application.

[0069] Figure 5 XRD pattern of NaYF4 type luminescent material prepared for Examples 2-6 and Comparative Example 1 of the present application.

[0070] Figure 6 Fluorescence spectrum of NaYF4 type luminescent material prepared for Example 1 of the present application under excitation of 980 nm excitation light.

[0071] Figure 7 Fluorescence spectrum of NaYF4 type luminescent material prepared for Examples 7, 8 of the present application under excitation of 980 nm excitation light.

[0072] Figure 8 Fluorescence spectrum of NaYF4 type luminescent material prepared for Examples 9, 10 of the present application under excitation of 980 nm excitation light.

[0073] Figure 9 Fluorescence spectrum of NaYF4 type luminescent material prepared for Examples 11, 12 of the present application under excitation of 980 nm excitation light.

[0074] Figure 10 TEM pattern of NaYF4 type luminescent material prepared for Example 1 of the present application.

[0075] Figure 11 Fluorescence color coordinates of NaYF4 type luminescent material prepared for Example 1 of the present application. DETAILED DESCRIPTION

[0076] The present application will be further described in detail by way of examples, but the present application is not limited to the scope of the examples.

[0077] Example 1

[0078] Y(NO3)3-6H2O, Yb(NO3)3-5H2O, Er(NO3)3-5H2O, NaF, NaNO2, NaNO3, and KNO3 were weighed in a molar ratio of 0.8:0.18:0.02:4:40:7:53 and pre-mixed;

[0079] The pre-mixed reactant materials were placed in a marquis mortar and ground with an appropriate amount of anhydrous ethanol for about 30 minutes, and then heated in a 70°C vacuum drying oven for a certain period of time to remove the anhydrous ethanol, and the dried materials were transferred to an alumina crucible;

[0080] The alumina crucible was placed in a high-temperature heating furnace in an Ar atmosphere glove box, and the temperature was raised to 400°C at a heating rate of about 10°C / min and reacted for 10 hours. After the reaction was completed, the sample was naturally cooled to room temperature to obtain a crude product;

[0081] The crude product was washed several times with deionized water to remove the molten salt medium and unreacted substances, and then filtered;

[0082] Finally, the filtered product was placed in a vacuum drying oven at 60°C and dried for 24 hours to obtain the final product, namely the NaYF4 type luminescent material NaYF4:Yb 3+ ,Er 3+ .

[0083] Examples 2-6

[0084] In Examples 2-6, the preparation method differs from that of Example 1 only in the composition of the molten salt medium, and the remaining steps and conditions are the same as those of Example 1.

[0085] In Examples 2-6, the molar ratio of Y(NO3)3·6H2O, Yb(NO3)3·5H2O, Er(NO3)3·5H2O, NaF, NaNO2, NaNO3 and KNO3 is 0.8:0.18:0.02:4:x:60-3x / 5:40-2x / 5, where x is 1, 5, 10, 20, 30, respectively. That is, in Examples 2-6, the molar fraction of NaNO2 in the molten salt medium is 1%, 5%, 10%, 20% or 30%, respectively.

[0086] Examples 7 and 8

[0087] In Examples 7 and 8, the preparation method differs from that in Example 1 only in the amount of molten salt medium added, and the remaining steps and conditions are the same as those in Example 1.

[0088] In Examples 7 and 8, the molar ratios of Y(NO₃)₃·6H₂O, Yb(NO₃)₃·5H₂O, Er(NO₃)₃·5H₂O, NaF, NaNO₂, NaNO₃, and KNO₃ are 0.8:0.18:0.02:4:a:b:c. In Example 7, a+b+c=25, and a:b:c is 40:7:53; in Example 8, a+b+c=75, and a:b:c is 40:7:53.

[0089] Examples 9 and 10

[0090] In Examples 9 and 10, the preparation method differs from that in Example 1 only in the reaction temperature, and the remaining steps and conditions are the same as those in Example 1: the reaction temperature in Example 9 is 200°C, and the reaction temperature in Example 10 is 300°C.

[0091] Examples 11 and 12

[0092] In Examples 11 and 12, the preparation method is different from that of Example 1 only in reaction time, and the other steps and conditions are the same as those of Example 1: the reaction time is 5 h in Example 11, and the reaction time is 1 h in Example 12.

[0093] Comparative Example 1

[0094] In Comparative Example 1, the preparation method is different from that of Example 1 only in the composition of the molten salt medium, i.e., NaNO2 is not used in the molten salt medium; and the other steps and conditions are the same as those of Example 1.

[0095] In Comparative Example 1, Y(NO3)3·6H2O, Yb(NO3)3·5H2O, Er(NO3)3·5H2O, NaF, NaNO3 and KNO3 are weighed and pre-mixed in a molar ratio of 0.8:0.18:0.02:4:60:40.

[0096] Effect Example

[0097] 1. X-ray Diffraction Test

[0098] The NaYF4:Yb 3+ ,Er 3+ products prepared in Examples 1-12 and Comparative Example 1 are tested by a D8 advance X-ray diffractometer of Bruker Company, and the obtained spectrum is shown in Figures 1-5 .

[0099] As can be seen from Figures 1-4 , the diffraction peaks of the product are consistent with the standard PDF card diffraction peak positions of cubic phase NaYF4, indicating that the NaYF4:Yb 3+ ,Er 3+ products with cubic crystal structure are successfully prepared in Examples 1-12.

[0100] As can be seen from Figure 5 , when NaNO2 is not added in the molten salt medium, the prepared product is consistent with the standard PDF card diffraction peak positions of hexagonal phase NaYF4, and no other diffraction peaks are observed, indicating that the product obtained at this time is a pure hexagonal phase product. With the gradual increase of the amount of NaNO2 added, the diffraction peaks of cubic phase NaYF4 gradually begin to appear in the product, and a mixed product of cubic phase and hexagonal phase is obtained, and when the amount of NaNO2 added is more than 20% of the total amount of the molten salt, the product is completely converted into a pure cubic phase NaYF4. The above results show the important role of the introduction of NaNO2 in the formation of the target cubic phase structure product.

[0101] 2. Fluorescence Spectrum Test under 980 nm Excitation Light Excitation

[0102] NaYF4:Yb 3+ ,Er 3+ The product was tested by fluorescence spectrum under excitation of 980 nm excitation light by FLS1000 fluorescence spectrometer of Edinburgh Company, and the result is shown in Figures 6-9 It can be seen that the sample has two extremely weak green emissions at 514-534 nm and 534-565 nm, and a relatively strong red emission at 640-680 nm.

[0103] In addition, it can be seen from Figures 7-9 that the upconversion red light intensity of the product gradually increases with the increase of the addition amount of molten salt medium, reaction temperature and reaction time.

[0104] 3. Transmission electron microscopy (TEM) test

[0105] NaYF4:Yb 3+ ,Er 3+ The product was characterized by Tecnai G2F20 S-TWIN transmission electron microscope of FEI Company, and the obtained image is shown in Figure 10 It can be seen from Figure 10 that the product shows about 50 nm spherical or cubic particles with uniform particle size.

[0106] 4. Fluorescence color coordinate test

[0107] NaYF4:Yb 3+ ,Er 3+ The product was converted from upconversion fluorescence spectrum data to color coordinates according to 1931 CIE-XYZ standard colorimetric system, which can more directly reflect the actual color under excitation of 980 nm excitation light, and the result is shown in Figure 11 It can be seen that the product in Example 1 shows relatively pure red light emission.

[0108] Although the specific embodiments of the present application are described above, those skilled in the art should understand that this is only an example, the protection scope of the present application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present application, and these changes and modifications all fall within the protection scope of the present application.

Claims

1. A method for preparing a NaYF4 type luminescent material, characterized in that: It includes the following steps: reacting the raw material composition in a molten salt medium to obtain the NaYF4 type luminescent material; The raw material composition includes a Y source, a Yb source, an Er source and a fluorinating agent, and the molten salt medium includes nitrite, NaNO3 and KNO3.

2. The method for preparing the NaYF4 type luminescent material according to claim 1, characterized in that: No organic solvent is used in the preparation method; And / or, no surfactant is used in the preparation method.

3. The method for preparing the NaYF4 type luminescent material according to claim 1, characterized in that: The preparation method satisfies one or more of the following conditions (1)-(6): (1) The Y source includes yttrium nitrate and / or yttrium fluoride, preferably yttrium nitrate, such as Y(NO3)3·6H2O; (2) The Yb source includes ytterbium nitrate and / or ytterbium fluoride, preferably ytterbium nitrate, such as Yb(NO3)3·5H2O; (3) The Er source includes erbium nitrate and / or erbium fluoride, preferably erbium nitrate, such as Er(NO3)3·5H2O; (4) The fluorinating agent includes NH4F and / or NaF, preferably NaF; (5) the nitrite comprises KNO2 and / or NaNO2, preferably NaNO2; and, (6) The molar ratio of the Y source, the Yb source, the Er source and the fluorinating agent is (0.78-0.8):(0.18-0.2):0.02:(2-8), for example, 0.8:0.18:0.02:

4.

4. The method for preparing the NaYF4 type luminescent material according to claim 1, characterized in that: The molten salt medium satisfies one or more of the following conditions (1)-(4): (1) The molar fraction of the nitrite in the molten salt medium is 1-50%, preferably 20%-50%, for example 1%, 5%, 10%, 30% or 40%; (2) The molar fraction of NaNO3 in the molten salt medium is 5%-60%, preferably 5%-10%, for example 7%; (3) the molar fraction of KNO3 in the molten salt medium is 30%-75%, preferably 40%-75%, for example 53%; and, (4) The molar ratio of the nitrite, NaNO3 and KNO3 is (1-50):(5-60):(30-75), preferably (20-50):(5-10):(40-75), for example, 40:7:

53.

5. The method for preparing the NaYF4 type luminescent material according to claim 1, characterized in that: The molar ratio of the Y source, the Yb source, the Er source and the molten salt medium is (0.78-0.8):(0.18-0.2):0.02:(25-100), preferably 0.8:0.18:0.02:(25-100), for example, 0.8:0.18:0.02:25, 0.8:0.18:0.02:75, or 0.8:0.18:0.02:

100.

6. The method for preparing the NaYF4 type luminescent material according to claim 1, characterized in that: The molar ratio of the Y source, the Yb source, the Er source, the fluorinating agent and the molten salt medium is (0.78-0.8):(0.18-0.2):0.02:(2-8):(25-100), for example, 0.8:0.18:0.02:4:(25-100), for example, 0.8:0.18:0.02:4:25, 0.8:0.18:0.02:4:75, or 0.8:0.18:0.02:4:

100.

7. The method for preparing the NaYF4 type luminescent material according to claim 1, characterized in that: The preparation method satisfies one or more of the following conditions (1)-(5): (1) The reaction temperature is 200°C to 400°C, for example, 200°C, 300°C or 400°C; (2) The reaction is carried out in an inert atmosphere, preferably an argon atmosphere; (3) the reaction time is 1 hour or longer, preferably 1-10 hours, for example 1 hour, 5 hours or 10 hours; and, (4) Before the reaction, the raw material composition and the molten salt medium are pretreated, and the pretreatment preferably includes the following steps: grinding the raw material composition, the molten salt medium and the auxiliary agent, and then removing the auxiliary agent; The amount of the auxiliary agent is preferably 30%-50% of the total mass of "the raw material composition and the molten salt medium", more preferably 40%; Wherein, the auxiliary agent is preferably ethanol; (5) After the reaction, a post-treatment operation is also included, and the post-treatment preferably includes removing the molten salt medium.

8. A NaYF4 type luminescent material, characterized in that The preparation method is as described in any one of claims 1 to 7.

9. The NaYF4 type luminescent material according to claim 8, characterized in that The average particle size of the NaYF4 type luminescent material is 30-70 nm, for example, 50 nm; and / or the NaYF4 type luminescent material has a cubic crystal structure.

10. Use of the NaYF4 type luminescent material according to claim 8 or 9 in a biological imaging system, a sensing device, a lighting device or an energy storage device.

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