A rare earth europium metal complex stress luminescence material, its preparation method and application

Abstract

The present invention discloses a rare earth europium metal complex stress luminescence material, a preparation method thereof and an application thereof, belonging to the technical field of stress luminescence materials. The chemical formula of the rare earth europium metal complex stress luminescence material is Eu(tpfd)3L, wherein tpfd is 4-pyridinecarboxyl trifluoroacetone, and L is 2,2'-bipyridine or 1,10-phenanthroline. The Eu(tpfd)3L is prepared by a solvent evaporation method. This material has strong stress luminescence performance and photoluminescence performance, and has good acid-base stability. This material can not only produce bright red light through the stimulation of mechanical force to realize the visual transformation of force-light, but also be widely applied to many fields such as visual pressure sensing, intelligent anti-counterfeiting, electronic signature, flexible wearable sensing devices or biomedicine. Moreover, the preparation method of the present invention is simple to operate, has low equipment requirements, small reaction energy consumption, high sample yield and good reproducibility.

Description

Technical Field

[0001] The present invention relates to the technical field of stress luminescent materials, and particularly to a rare earth europium metal complex stress luminescent material, a preparation method thereof, and an application thereof. Background Art

[0002] Stress luminescence (ML) materials are materials that can exhibit luminescence phenomena when stimulated by stress. The ways of stress stimulation include, but are not limited to, various forms such as extrusion, grinding, friction, impact, ultrasonic waves, etc., involving the conversion of mechanical energy into visible light. In recent years, a variety of inorganic and organic stress luminescent compounds have been successfully prepared and shown great application prospects in fields such as real-time stress sensors, signature graphics, displays, structural damage monitoring, wearable lighting devices, self-powered displays, mechanical energy collection and conversion, and bioimaging devices.

[0003] Currently reported stress luminescent materials include three categories: organic, inorganic, and organic-inorganic hybrid materials. Among them, organic stress luminescent materials have complex and cumbersome synthesis processes, broadened emission wavelengths, instability, and easily collapsible structures; inorganic stress luminescent materials have problems such as a single type of material, mainly sulfur-based systems and inorganic oxide systems, poor biocompatibility, low luminescence intensity, and easy quenching after moisture absorption, increasing environmental limitations in practical applications. In addition, the existing stress luminescent materials also have the following problems: (1) The self-structure problems of stress luminescent powders lead to poor luminescence performance, and there are few stress luminescent materials that exhibit strong luminescence brightness at room temperature; (2) The preparation conditions of inorganic stress luminescent materials are usually relatively harsh, requiring anhydrous and oxygen-free conditions, and the reaction temperature is usually several hundred or even thousands of degrees Celsius. Problems such as long reaction time, high reaction energy consumption, high equipment requirements, and high costs limit the large-scale production of such materials.

[0004] In summary, the types of materials with relatively high stress luminescence intensity are still relatively few at present. Therefore, it is very necessary to develop and design new high-intensity stress luminescent materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a rare earth europium metal complex stress luminescent material, a preparation method thereof, and an application thereof to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention: A rare earth europium metal complex stress luminescent material with the chemical formula Eu(tpfd)3L, where tpfd is 4-pyridinecarboxyl trifluoroacetone, and L is 2,2'-bipyridine or 1,10-phenanthroline.

[0008] In the above rare earth europium metal complex, 4-pyridinecarboxyl trifluoroacetone is used as the main ligand, and 2,2'-bipyridine or 1,10-phenanthroline is used as the auxiliary ligand.

[0009] Further, Eu in Eu(tpfd)3L is +3 valence.

[0010] Further, the stress luminescence is specifically mechanical stress luminescence, and the rare earth europium metal complex stress luminescence material generates bright red light through mechanical force stimulation, thereby realizing the visualization transformation of force-light.

[0011] Further, the rare earth europium metal complex stress luminescence material simultaneously has stress luminescence performance and photoluminescence performance.

[0012] The second technical solution of the present invention: The preparation method of the above rare earth europium metal complex stress luminescence material uses 2,2'-bipyridine or 1,10-phenanthroline, 4-pyridinecarboxyl trifluoroacetone and europium salt as raw materials, and prepares the rare earth europium metal complex stress luminescence material by the solvent evaporation method.

[0013] Further, the solvent evaporation method specifically includes the following steps:

[0014] Mix 2,2'-bipyridine or 1,10-phenanthroline, solvent and europium salt, carry out the first stirring reaction, then add 4-pyridinecarboxyl trifluoroacetone, carry out the second stirring reaction, and after the reaction is completed, filter and stand to obtain the rare earth europium metal complex stress luminescence material.

[0015] The reaction must be carried out in the above reaction sequence to obtain the target product. Changing the reaction sequence, such as adding the main ligand and the auxiliary ligand together (i.e., carrying out one stirring reaction), or adding the main ligand first (i.e., mixing the main ligand with the solvent and europium salt) to carry out the first stirring reaction, and then adding the auxiliary ligand to carry out the second stirring reaction, cannot obtain the target product.

[0016] Further, the europium salt is europium chloride, specifically EuCl3·6H2O; the solvent is a mixed solution of triethylamine and absolute ethanol.

[0017] Further, the volume ratio of triethylamine to absolute ethanol is 8:50000.

[0018] Further, the first stirring reaction is carried out at room temperature, and the reaction time is 24-72 hours; the second stirring reaction is carried out at room temperature, and the reaction time is 2-10 hours.

[0019] Further, the room temperature specifically refers to 20-30 °C.

[0020] Further, on a molar ratio basis, 2,2'-bipyridine or 1,10-phenanthroline: europium salt: 4-pyridinecarboxyl trifluoroacetone = 2:1:3.

[0021] Further, the dosage ratio of the 2,2'-bipyridine or 1,10-phenanthroline to the solvent is 0.2 mmol: 25 mL.

[0022] Further, the specific operation of mixing the 2,2'-bipyridine or 1,10-phenanthroline, the solvent and the europium salt is as follows: add the 2,2'-bipyridine or 1,10-phenanthroline to the solvent, stir at room temperature for 10 - 30 minutes, and then add the europium salt.

[0023] Further, the time for standing still at room temperature is two weeks (14 days), and the purpose of standing still at room temperature is to slowly volatilize the solvent.

[0024] The third technical solution of the present invention: the application of the above-mentioned rare earth europium metal complex stress luminescent material in the fields of visual pressure sensing, intelligent anti-counterfeiting, electronic signature, flexible wearable sensing device or biomedicine.

[0025] Further, the application method is as follows: compound the rare earth europium metal complex stress luminescent material with an organic polymer material to prepare a transparent composite film; attach the composite film to the surface of the component to be measured, apply mechanical external force, and convert the stress received by the component to be measured into light emission under the action of the mechanical external force. Through this process, high-brightness stress-light direct energy conversion can be achieved, the visualization of pressure sensing can be realized, and the applications in the fields of intelligent anti-counterfeiting, electronic signature, flexible wearable sensing device or biomedicine can be realized.

[0026] Further, the organic polymer material includes polyethylene terephthalate (PET) or polydimethylsiloxane (PDMS).

[0027] The present invention discloses the following technical effects:

[0028] (1) The rare earth europium metal complex stress luminescent material of the present invention uses 4-pyridinecarboxyl trifluoroacetone as the main ligand and 2,2'-bipyridine or 1,10-phenanthroline as the auxiliary ligand. 4-pyridinecarboxyl trifluoroacetone and the auxiliary ligand effectively sensitize the luminescence of the central Eu(III) ion through the "antenna effect", so that the material can emit strong narrow-band red light emission only under the action of stress without light illumination. The stress luminescence peak is located near 617 nm. The stress luminescence performance of this material is excellent. Not only can a strong red luminescence phenomenon be observed in the dark, but also a visible bright red luminescence can be seen under bright natural light.

[0029] (2) Compared with the traditional high-temperature solid-phase preparation method of stress-luminescent materials, the preparation method of the rare-earth europium metal complex stress-luminescent material disclosed in the present invention has the advantages of simple process, mild and easy-to-control conditions, low equipment requirements, low reaction energy consumption, being green and environmentally friendly without pollution, high material yield, stable properties (with good acid-base stability), good reproducibility, good crystallinity, high purity, and being easy for industrial production.

[0030] (3) For the stress-luminescent material of the present invention, within a certain range, the stress-luminescence intensity of the material is proportional to the magnitude of the applied mechanical force, enabling the visualization of pressure sensing and being applicable to various intelligent sensing fields, such as visual pressure sensing, intelligent anti-counterfeiting, electronic signature, flexible wearable sensing devices, or biomedical fields. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is a three-dimensional stacking diagram of the crystal structure of the rare-earth europium metal complex stress-luminescent material prepared in Example 1. In the figure, gray represents C atoms, red represents O atoms, dark blue represents N atoms, green represents F atoms, and sky blue represents Eu atoms;

[0033] Figure 2 It is a three-dimensional stacking diagram of the crystal structure of the rare-earth europium metal complex stress-luminescent material prepared in Example 2. In the figure, gray represents C atoms, red represents O atoms, dark blue represents N atoms, green represents F atoms, and sky blue represents Eu atoms;

[0034] Figure 3 It is the X-ray powder diffraction pattern (PXRD) of the rare-earth europium metal complex stress-luminescent material prepared in Example 1 and the theoretical X-ray powder diffraction pattern of this material;

[0035] Figure 4 It is the X-ray powder diffraction pattern (PXRD) of the rare-earth europium metal complex stress-luminescent material prepared in Example 2 and the theoretical X-ray powder diffraction pattern of this material;

[0036] Figure 5 It is the photoluminescence excitation-emission spectrum of the rare-earth europium metal complex stress-luminescent material prepared in Example 1;

[0037] Figure 6Photograph of the stress luminescence of the rare earth europium metal complex stress luminescence material prepared in Example 1 under mechanical force in the dark;

[0038] Figure 7 Photograph of the stress luminescence of the rare earth europium metal complex stress luminescence material prepared in Example 1 under mechanical force in bright light;

[0039] Figure 8 X-ray powder diffraction pattern (PXRD) of the rare earth europium metal complex stress luminescence material prepared in Example 1 after being soaked for 72 hours under different pH conditions;

[0040] Figure 9 Stress luminescence spectrum of the rare earth europium metal complex stress luminescence material prepared in Example 1 under different mechanical forces;

[0041] Figure 10 Linear fitting graph of the luminescence intensity of the rare earth europium metal complex stress luminescence material prepared in Example 1 under different mechanical forces;

[0042] Figure 11 Stress luminescence spectrum of the rare earth europium metal complex stress luminescence material prepared in Example 2 under different mechanical forces;

[0043] Figure 12 Handwritten luminescence graph of the stress luminescence signature anti-counterfeiting film prepared by wrapping the rare earth europium metal complex stress luminescence material with a PET film in Application Example 2;

[0044] Figure 13 Photographs of the samples prepared in Comparative Example 1 and Comparative Example 2 under stress. Detailed implementation manners

[0045] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0046] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0047] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention has been described only in terms of preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to those documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0048] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the description of the present invention, which will be apparent to those skilled in the art. Other embodiments obtained from the description of the present invention will be apparent to those skilled in the art. The description and examples of the present invention are merely illustrative.

[0049] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0050] The preparation method of 4-pyridinecarboxyltrifluoroacetone (structural formula is ) used in the following examples and comparative examples is as follows: Add 3 g (0.056 mol) of sodium methoxide to 30 mL of anhydrous ether, and while stirring, add 7.2 mL (0.06 mol) of ethyl trifluoroacetate diluted with 30 mL of anhydrous ether, and then slowly add dropwise 6.6 mL (0.06 mol) of 4-acetylpyridine diluted with 30 mL of anhydrous ether. The mixed system is refluxed at 45 °C for 5 hours; after the reaction is completed, add water to dissolve the obtained solid, and extract it multiple times with anhydrous ether; the aqueous phase is acidified with dilute hydrochloric acid (concentration is 10 wt%), and a yellow solid powder is precipitated, and recrystallized with ethanol-water (volume ratio 1:10) to obtain yellow transparent 4-pyridinecarboxyltrifluoroacetone crystals.

[0051] The other raw materials such as 2,2'-bipyridine (structural formula is ), 1,10-phenanthroline (structural formula is ) used in the following examples and comparative examples are all ordinary commercially available products.

[0052] The room temperature involved in the following examples and comparative examples specifically refers to 20 - 30 °C.

[0053] Example 1

[0054] 2,2'-Bipyridine (0.312 g, 0.2 mmol) was added to a mixed solvent composed of 0.004 mL of triethylamine and 25 mL of absolute ethanol, and the mixture was stirred at room temperature for 30 minutes. Then, EuCl3·6H2O (0.0366 g, 0.1 mmol) was added, and the mixture was stirred at room temperature for 48 hours. After that, 4-pyridinecarboxyl trifluoroacetone (0.0656 g, 0.3 mmol) was added. The mixed system was stirred at room temperature in a semi-closed beaker for 4 hours and then filtered. The filtrate was sealed and left to stand to slowly evaporate the solvent. After two weeks, the Eu(tpfd)3L sample was obtained (the three-dimensional packing diagram of its crystal structure is as shown in Figure 1 ), the purity of the sample was 99%, and the yield was 54%.

[0055] Example 2

[0056] 1,10-Phenanthroline (0.396 g, 0.2 mmol) was added to a mixed solvent composed of 0.004 mL of triethylamine and 25 mL of absolute ethanol, and the mixture was stirred at room temperature for 30 minutes. Then, EuCl3·6H2O (0.0366 g, 0.1 mmol) was added, and the mixture was stirred at room temperature for 48 hours. After that, 4-pyridinecarboxyl trifluoroacetone (0.0656 g, 0.3 mmol) was added. The mixed system was stirred at room temperature in a semi-closed beaker for 4 hours and then filtered. The filtrate was sealed and left to stand to slowly evaporate the solvent. After two weeks, the Eu(tpfd)3L sample was obtained (the three-dimensional packing diagram of its crystal structure is as shown in Figure 2 ), the purity of the sample was 99%, and the yield was 52%.

[0057] Comparative Example 1

[0058] Same as Example 1, except that 2,2'-bipyridine was replaced with an equimolar amount of 4,4'-bipyridine.

[0059] Comparative Example 2

[0060] Same as Example 1, except that 4-pyridinecarboxyl trifluoroacetone was replaced with an equimolar amount of benzoyl trifluoroacetone (the structural formula is as shown in ).

[0061] Application Example 1

[0062] 10 g of polydimethylsiloxane was thoroughly mixed with 10 g of Eu(tpfd)3L prepared in Example 1 to obtain a mixture. Then, the mixture was transferred to a 3×3 cm square mold and dried in an oven at 80 °C for 5 hours to achieve curing and defoaming, and a transparent composite film was obtained.

[0063] Application Example 2

[0064] Transfer the Eu(tpfd)3L prepared in Example 1 of 5G to a 3×3 cm square mold. Subsequently, wrap the Eu(tpfd)3L with a PET film and perform thermoforming on the wrapped film using a laminator to obtain a transparent composite film, which serves as a stress-luminescent signature anti-counterfeiting film.

[0065] Test Example

[0066] Figure 3 The X-ray powder diffraction pattern (PXRD) of the rare-earth europium metal complex stress-luminescent material prepared in Example 1 and the theoretical X-ray powder diffraction pattern of this material prove the successful synthesis of the rare-earth europium metal complex stress-luminescent material. Moreover, it can also be seen from this that all the diffraction peaks of the material prepared in Example 1 are consistent with the simulated crystal data, indicating that this material has a very high purity.

[0067] Figure 4 The X-ray powder diffraction pattern (PXRD) of the rare-earth europium metal complex stress-luminescent material prepared in Example 2 and the theoretical X-ray powder diffraction pattern of this material prove the successful synthesis of the rare-earth europium metal complex stress-luminescent material. Moreover, it can also be seen from this that all the diffraction peaks of the material prepared in Example 2 are consistent with the simulated crystal data, indicating that this material has a very high purity.

[0068] Figure 5 The photoluminescence excitation-emission spectrum of the rare-earth europium metal complex stress-luminescent material prepared in Example 1 shows that the material prepared in Example 1 has an excitation spectrum covering the ultraviolet region and extending into the visible light region, and the characteristic transition peaks of Eu 3+ ions 5 D0→ 7 F j are observed.

[0069] Figure 6 The stress-luminescence photo of the rare-earth europium metal complex stress-luminescent material prepared in Example 1 under mechanical force in the dark condition (only applying mechanical force without light excitation) shows that the material produces bright red light under the stimulation of mechanical force.

[0070] Figure 7 The stress-luminescence photo of the rare-earth europium metal complex stress-luminescent material prepared in Example 1 under mechanical force in bright light (only applying mechanical force without light excitation) shows that the material produces bright red light visible to the naked eye under the stimulation of mechanical force in bright natural light.

[0071] Figure 8X-ray powder diffraction pattern (PXRD) of the rare earth europium metal complex stress luminescence material prepared in Example 1 after soaking at room temperature for 72 hours under different pH conditions. It can be seen that the diffraction peaks of the material remain consistent after soaking treatment in different pH solutions, indicating that the material has good acid and alkali resistance stability.

[0072] Figure 9 Stress luminescence spectrum of the rare earth europium metal complex stress luminescence material prepared in Example 1 under different mechanical forces. It can be seen that the stress luminescence peak of the material is located near 617 nm, and the stress luminescence intensity of the material increases with the increase of mechanical force.

[0073] Figure 10 Linear fitting diagram of the luminescence intensity of the rare earth europium metal complex stress luminescence material prepared in Example 1 under different mechanical forces. It can be seen that within a certain range, the stress luminescence intensity of the material has a good linear relationship with the magnitude of the applied mechanical force, and the correlation coefficient R 2 = 0.99673.

[0074] Figure 11 Stress luminescence spectrum of the rare earth europium metal complex stress luminescence material prepared in Example 2 under different mechanical forces. It can be seen that the stress luminescence peak of the material is located near 617 nm, and the stress luminescence intensity of the material increases with the increase of mechanical force.

[0075] Figure 12 Handwritten luminescence diagram of the stress luminescence signature anti-counterfeiting film prepared by wrapping the rare earth europium metal complex stress luminescence material with a PET film in Application Example 2. It can be seen that a strong red luminescence phenomenon can be observed under dark conditions after handwriting a signature on the anti-counterfeiting film.

[0076] Figure 13 Photos of the samples prepared in Comparative Example 1 and Comparative Example 2 under stress. It can be seen that there is no stress luminescence phenomenon in the samples prepared in Comparative Example 1 and Comparative Example 2.

[0077] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A rare earth europium metal complex stress luminescent material, characterized in that: The chemical formula is Eu(tpfd)3L, wherein tpfd is 4-pyridinecarbonyltrifluoroacetone, and L is 2,2'-bipyridine or 1,10-phenanthroline.

2. The method for preparing the rare earth europium metal complex stress luminescent material according to claim 1, characterized in that: The rare earth europium metal complex stress luminescent material is prepared by a solvent volatilization method using 2,2'-bipyridine or 1,10-phenanthroline, 4-pyridinecarbonyl trifluoroacetone and europium salt as raw materials; The solvent volatilization method specifically comprises the following steps: Mixing 2,2'-bipyridine or 1,10-phenanthroline, a solvent and a europium salt, performing a first stirring reaction, then adding 4-pyridinecarbonyltrifluoroacetone, performing a second stirring reaction, filtering after the reaction is completed, and standing at room temperature to obtain the rare earth europium metal complex stress luminescent material; The first stirring reaction is carried out at room temperature for 24-72 hours; the second stirring reaction is carried out at room temperature for 2-10 hours.

3. The method for preparing the rare earth europium metal complex stress luminescent material according to claim 2, characterized in that: The europium salt is europium chloride; and the solvent is a mixed solution of triethylamine and anhydrous ethanol.

4. The method for preparing the rare earth europium metal complex stress luminescent material according to claim 3, characterized in that: The volume ratio of the triethylamine to anhydrous ethanol is 8:50000.

5. The method for preparing the rare earth europium metal complex stress luminescent material according to claim 2, characterized in that: In terms of molar ratio, 2,2'-bipyridine or 1,10-phenanthroline: europium salt: 4-picolinyltrifluoroacetone = 2:1:

3.

6. The method for preparing the rare earth europium metal complex stress luminescent material according to claim 2, characterized in that: The usage ratio of the 2,2'-bipyridine or 1,10-phenanthroline to the solvent is 0.2 mmol:25 mL.

7. The method for preparing the rare earth europium metal complex stress luminescent material according to claim 2, characterized in that: The room temperature standing time is two weeks.

8. Application of the rare earth europium metal complex stress luminescent material as claimed in claim 1 in visual pressure sensing, intelligent anti-counterfeiting, electronic signature, flexible wearable sensing equipment or biomedical field.

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