Lignin-based long-afterglow luminescent material as well as preparation method and application thereof

Abstract

The invention belongs to the field of luminescent materials, and provides a lignin-based long-afterglow luminescent material as well as a preparation method and application thereof. The preparation method of the long-afterglow luminescent material comprises the following steps: uniformly grinding urea, boric acid and lignosulfonate, placing the obtained solid mixture in an open beaker for heating treatment, naturally cooling to room temperature after the reaction is completed, and grinding to obtain the long-afterglow luminescent material. The obtained long-afterglow luminescent material powder can emit yellow green afterglow after being excited and removed by ultraviolet light, the average attenuation life of the long-afterglow luminescent material powder can reach 1200 ms or above, the macroscopic afterglow emission time can reach 10 s or above, and the long-afterglow luminescent material powder is convenient to prepare, low in raw material cost and environmentally friendly. The obtained long-afterglow luminescent material has important application in the fields of information encryption, biochemical sensing and the like.

Description

Technical Field

[0001] The present invention belongs to the field of luminescent materials, and particularly relates to a lignin-based long afterglow luminescent material, a preparation method thereof, and an application thereof. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and it is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Long-life room-temperature phosphorescent materials have important application values in the fields of multicolor display, information encryption, optoelectronics, photocatalysis, and bioimaging. Traditional room-temperature phosphorescent materials often require doping with metal elements, while the synthesis strategy of pure organic room-temperature phosphorescence involves complex process steps and toxic compounds. There is a practical need to prepare room-temperature phosphorescent materials using non-toxic natural biomass resources. At present, common preparation methods for room-temperature phosphorescent materials include host-guest systems, crystallization engineering, exogenous heavy atom doping, and framework systems. Restricting the non-radiative transitions of chromophores with a rigid matrix is a prerequisite for effectively obtaining phosphorescence. Heteroatoms such as boron, nitrogen, sulfur, or halogens are also favorable factors for promoting the generation of phosphorescence. The simultaneous use of multiple methods can effectively promote the spin coupling process and the conversion of excitons from the singlet state to the triplet state, resulting in a photoluminescence phenomenon.

[0004] As a by-product of the pulp and paper industry and biorefining, the annual output of industrial lignin is about 50 million tons, but more than 90% is used as fuel for low-value utilization, wasting a large amount of biomass raw materials. Lignin is the only naturally renewable aromatic polymer, containing a large number of oxygen-containing groups, and is an ideal precursor for preparing various photoluminescent materials. It has been proven that lignin can produce aggregation-induced emission fluorescence through the clustering of carbonyl groups and the intramolecular spin restriction effect. However, there is little research on lignin-based room-temperature phosphorescent materials, and the room-temperature phosphorescent materials directly prepared from lignin generally have problems such as short phosphorescence lifetimes and low luminescence intensities. The method of preparing room-temperature phosphorescent materials by converting lignin into carbon dots or carbon quantum dots and then embedding them in a matrix for restriction is relatively cumbersome and energy-consuming, which greatly limits the application of lignin in the field of luminescent materials. There are huge challenges in simply and greenly preparing lignin-based long afterglow luminescent materials. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a lignin-based long afterglow luminescent material, a preparation method thereof, and an application thereof. The long afterglow luminescent material of the present invention has a relatively long lifetime, a relatively high phosphorescence quantum efficiency, a relatively low cost of the precursor, and is green and environmentally friendly.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect of the present invention, a lignin-based long afterglow luminescent material is provided, comprising: lignin nanoparticles and an amorphous matrix; The lignin nanoparticles are uniformly dispersed and embedded in the amorphous matrix.

[0007] Research has found that: lignosulfonate, as an industrial lignin that simultaneously has the characteristic groups of lignin and sulfonic acid groups, self-dopes atomic sulfur atoms to promote the spin coupling process, can synergistically promote the generation of phosphorescence with the host-guest system, and has predictable application potential.

[0008] In some embodiments, the amorphous matrix is formed by the reaction of urea and boric acid at a preset temperature.

[0009] In the second aspect of the present invention, a preparation method of a lignin-based long afterglow luminescent material is provided, comprising: Mixing lignosulfonate, urea, and boric acid uniformly to obtain a mixture; Heating the mixture to the preset temperature for reaction, collecting the reaction product, and physically processing it to the preset particle size to obtain the lignin-based long afterglow luminescent material.

[0010] In some embodiments, the lignosulfonate is sodium lignosulfonate.

[0011] In some embodiments, the ratio of the lignosulfonate to the "total mass of urea and boric acid" is (1 - 20):450.

[0012] In some embodiments, the mass ratio of urea to boric acid is (0.5 - 2):1.

[0013] In some embodiments, the preset temperature is 200°C - 210°C.

[0014] In some embodiments, the reaction time is 0.5 - 3 hours.

[0015] In some embodiments, the physical processing method is grinding.

[0016] In the third aspect of the present invention, the above-mentioned lignin-based long afterglow luminescent material is provided for use in the fields of anti-counterfeiting and information encryption.

[0017] Advantages of the present invention (1) The lignin-based long afterglow luminescent material provided by the present invention can emit green phosphorescence distinguishable by the naked eye after the excitation of ultraviolet excitation light is turned off, and the emission wavelength is 528 nm. The average decay lifetime of the lignin-based long afterglow luminescent material can reach more than 1249.7 ms in a room-temperature air environment, and the afterglow luminescence time distinguishable by the naked eye can reach more than 10 s in a room-temperature air environment; (2) The preparation process of the lignin-based long afterglow luminescent material provided by the present invention is simple and rapid, without complex processes, expensive equipment, and stringent operating environments. The raw materials used are inexpensive and readily available industrial raw materials and sustainable resources, and the preparation cost is relatively low. (3) The lignin-based long afterglow luminescent material provided by the present invention has great potential application value in the fields of information encryption, anti-counterfeiting, sensing, multicolor display, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0019] Figure 1 UV-visible absorption spectra of the long afterglow luminescent materials and room temperature phosphorescent materials prepared in Examples 1-3 and Comparative Examples 1-3.

[0020] Figure 2 Phosphorescence emission spectra of the long afterglow luminescent materials and room temperature phosphorescent materials prepared in Examples 1-3 and Comparative Examples 1-3.

[0021] Figure 3 Transmission electron microscope image of the long afterglow luminescent material prepared in Example 2.

[0022] Figure 4 Phosphorescence time-resolved spectrum of the long afterglow luminescent material prepared in Example 1.

[0023] Figure 5 Phosphorescence time-resolved spectrum of the long afterglow luminescent material prepared in Example 2.

[0024] Figure 6 Phosphorescence time-resolved spectrum of the long afterglow luminescent material prepared in Example 3.

[0025] Figure 7 Phosphorescence time-resolved spectrum of the room temperature phosphorescent material prepared in Comparative Example 1.

[0026] Figure 8 Phosphorescence time-resolved spectrum of the room temperature phosphorescent material prepared in Comparative Example 2.

[0027] Figure 9 Phosphorescence time-resolved spectrum of the room temperature phosphorescent material prepared in Comparative Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0029] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are interpretations rather than limitations of the present invention.

[0030] In the following examples and comparative examples, all test methods are common methods in the industry and will not be specifically described here.

[0031] Example 1 A preparation method of a long afterglow luminescent material based on lignin, comprising the following steps: Grind 1125 mg of urea, 1125 mg of boric acid and 15 mg of lignosulfonate evenly to obtain a reactant to be reacted. Place the obtained reactant to be reacted in a beaker for one-step heat treatment (200 °C, 1 h); after the reaction is completed, naturally cool to room temperature, and grind the obtained product to obtain a long afterglow luminescent material.

[0032] The ultraviolet-visible spectrum of the long afterglow luminescent material prepared in this example, in which lignin nanoparticles are uniformly dispersed and embedded in an amorphous matrix, is as Figure 1 shown. As can be seen from Figure 1 , the maximum absorption wavelength is 390 nm.

[0033] The phosphorescence emission spectrum of the long afterglow luminescent material prepared in this example, in which lignin nanoparticles are uniformly dispersed and embedded in an amorphous matrix, is as Figure 2 shown, and the maximum emission wavelength is 528 nm.

[0034] The phosphorescence time-resolved spectrum of the long afterglow luminescent material prepared in this example, in which lignin nanoparticles are uniformly dispersed and embedded in an amorphous matrix, is as Figure 4 shown, and the data fitting result shows that the phosphorescence decay lifetime reaches 1249.7 ms.

[0035] Example 2 A preparation method of a long afterglow luminescent material based on lignin, comprising the following steps: Grind 1500 mg of urea, 750 mg of boric acid and 15 mg of lignosulfonate evenly to obtain a reactant to be reacted. Place the obtained reactant to be reacted in a beaker for one-step heat treatment (200 °C, 1 h); after the reaction is completed, naturally cool to room temperature, and grind the obtained product to obtain a long afterglow luminescent material.

[0036] The ultraviolet-visible spectrum of the long afterglow luminescent material prepared in this example, in which lignin nanoparticles are uniformly dispersed and embedded in an amorphous matrix, is as Figure 1 shown. As can be seen from Figure 1 , the maximum absorption wavelength is 390 nm.

[0037] The phosphorescence emission spectrum of the long-afterglow luminescent material in which the lignin nanoparticles prepared in this example are uniformly dispersed and embedded in the amorphous matrix is as follows Figure 2 shown, and the maximum emission wavelength is 528 nm.

[0038] The phosphorescence time-resolved spectrum of the long-afterglow luminescent material in which the lignin nanoparticles prepared in this example are uniformly dispersed and embedded in the amorphous matrix is as follows Figure 5 shown, and the data fitting result shows that the phosphorescence decay lifetime reaches 1256.99 ms.

[0039] The transmission electron micrograph of the long-afterglow luminescent material in which the lignin nanoparticles prepared in this example are uniformly dispersed and embedded in the amorphous matrix is as follows Figure 3 shown. It can be seen from Figure 3 that the lignin nanoparticles are uniformly dispersed and embedded in the amorphous matrix.

[0040] Example 3 A preparation method of a long-afterglow luminescent material based on lignin, comprising the following steps: 750 mg of urea, 1500 mg of boric acid and 15 mg of lignosulfonate are ground evenly to obtain a reactant to be reacted. The obtained reactant to be reacted is placed in a beaker for one-step heat treatment (200 °C, 1 h); after the reaction is completed, it is naturally cooled to room temperature, and the obtained product is ground to obtain a long-afterglow luminescent material.

[0041] The ultraviolet-visible spectrum of the long-afterglow luminescent material in which the lignin nanoparticles prepared in this example are uniformly dispersed and embedded in the amorphous matrix is as follows Figure 1 shown. It can be seen from Figure 1 that the maximum absorption wavelength is 390 nm.

[0042] The phosphorescence emission spectrum of the long-afterglow luminescent material in which the lignin nanoparticles prepared in this example are uniformly dispersed and embedded in the amorphous matrix is as follows Figure 2 shown, and the maximum emission wavelength is 528 nm.

[0043] The phosphorescence time-resolved spectrum of the long-afterglow luminescent material in which the lignin nanoparticles prepared in this example are uniformly dispersed and embedded in the amorphous matrix is as follows Figure 6 shown, and the data fitting result shows that the phosphorescence decay lifetime reaches 1327.24 ms.

[0044] Comparative Example 1 A preparation method of a room-temperature phosphorescent material, comprising the following steps: Grind 1125 mg of urea and 1125 mg of boric acid evenly to obtain the reactants to be used. Place the obtained reactants to be used in a beaker for one-step heat treatment (200 °C, 1 h); after the reaction is completed, naturally cool to room temperature, and grind the obtained product to obtain a room-temperature phosphorescent material.

[0045] The ultraviolet-visible absorption spectrum of the room-temperature phosphorescent material prepared in this comparative example is as Figure 1 shown, without an absorption peak at 390 nm.

[0046] The phosphorescence emission spectrum of the room-temperature phosphorescent material prepared in this comparative example is as Figure 2 shown, and the emission intensity is much lower than that of the room-temperature phosphorescent material prepared in Example 1.

[0047] The phosphorescence time-resolved spectrum of the room-temperature phosphorescent material prepared in this comparative example is as Figure 7 shown, and the data fitting result shows that the phosphorescence decay lifetime is 539.33 ms, which is far less than that of the long-afterglow luminescent material prepared in Example 1.

[0048] Comparative Example 2 A preparation method of a room-temperature phosphorescent material includes the following steps: Grind 1500 mg of urea and 750 mg of boric acid evenly to obtain the reactants to be used. Place the obtained reactants to be used in a beaker for one-step heat treatment (200 °C, 1 h); after the reaction is completed, naturally cool to room temperature, and grind the obtained product to obtain a room-temperature phosphorescent material.

[0049] The ultraviolet-visible absorption spectrum of the room-temperature phosphorescent material prepared in this comparative example is as Figure 1 shown, without an absorption peak at 390 nm.

[0050] The phosphorescence emission spectrum of the room-temperature phosphorescent material prepared in this comparative example is as Figure 2 shown, and the emission intensity is much lower than that of the long-afterglow luminescent material prepared in Example 2.

[0051] The phosphorescence time-resolved spectrum of the room-temperature phosphorescent material prepared in this comparative example is as Figure 8 shown, and the data fitting result shows that the phosphorescence decay lifetime is 322.04 ms, which is far less than that of the long-afterglow luminescent material prepared in Example 2.

[0052] Comparative Example 3 A preparation method of a room-temperature phosphorescent material includes the following steps: Grind 750 mg of urea and 1500 mg of boric acid evenly to obtain the reactants to be used. Place the obtained reactants to be used in a beaker for one-step heat treatment (200 °C, 1 h); after the reaction is completed, naturally cool to room temperature, and grind the obtained product to obtain a room-temperature phosphorescent material.

[0053] The UV-Vis absorption spectrum of the room-temperature phosphorescent material prepared in this comparative example is as follows Figure 1 shown, without an absorption peak at 390 nm.

[0054] The phosphorescence emission spectrum of the room-temperature phosphorescent material prepared in this comparative example is as follows Figure 2 shown, and the emission intensity is much lower than that of the long-afterglow luminescent material prepared in Example 3.

[0055] The phosphorescence time-resolved spectrum of the room-temperature phosphorescent material prepared in this comparative example is as follows Figure 9 shown, and the data fitting result shows that the phosphorescence decay lifetime is 593.82 ms, which is far inferior to the long-afterglow luminescent material prepared in Example 3.

[0056] Comparative Example 4 The difference from Example 2 is that alkali lignin is used.

[0057] After the 365 nm UV excitation is turned off, the visible room-temperature phosphorescence emission time of the room-temperature phosphorescent material prepared in this comparative example is about 5 s, which is far inferior to the long-afterglow luminescent material prepared in Example 2.

[0058] Comparative Example 5 The difference from Example 2 is that sulfite lignin is used.

[0059] After the 365 nm UV excitation is turned off, the visible room-temperature phosphorescence emission time of the room-temperature phosphorescent material prepared in this comparative example is about 4.5 s, which is far inferior to the long-afterglow luminescent material prepared in Example 2.

[0060] From the comparison of Example 2, Comparative Examples 4 and 5, it can be seen that compared with sulfite lignin and alkali lignin, the luminescent material prepared with lignosulfonate has a longer afterglow emission time, which can reach more than 10 s in a room-temperature air environment.

[0061] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lignin-based long afterglow luminescent material, characterized in that: include: Lignin nanoparticles and amorphous matrices; The lignin nanoparticles are uniformly dispersed and embedded in the amorphous matrix.

2. The lignin-based long afterglow luminescent material according to claim 1, characterized in that: The amorphous matrix is ​​formed by reacting urea and boric acid at a preset temperature.

3. A method for preparing a lignin-based long afterglow luminescent material, characterized in that: include: mixing lignin sulfonate, urea and boric acid uniformly to obtain a mixture; The mixture is heated to a preset temperature to react, and the reaction product is collected and physically processed to a preset particle size to obtain a lignin-based long afterglow luminescent material.

4. The method for preparing the lignin-based long afterglow luminescent material according to claim 3, characterized in that: The lignin sulfonate is sodium lignin sulfonate.

5. The method for preparing the lignin-based long afterglow luminescent material according to claim 3, characterized in that: The ratio of the lignin sulfonate to the "total mass of urea and boric acid" is (1-20):

450.

6. The method for preparing the lignin-based long afterglow luminescent material according to claim 1, characterized in that: The mass ratio of urea to boric acid is (0.5-2):

1.

7. The method for preparing the lignin-based long afterglow luminescent material according to claim 1, characterized in that: The preset temperature is 200°C-210°C.

8. The method for preparing the lignin-based long afterglow luminescent material according to claim 1, characterized in that: The reaction time is 0.5-3 hours.

9. The method for preparing the lignin-based long afterglow luminescent material according to claim 1, characterized in that: The physical processing method is grinding.

10. Use of the lignin-based long afterglow luminescent material according to claim 1 or 2 in the fields of anti-counterfeiting and information encryption.

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