Long-life room-temperature phosphorescent material based on natural polysaccharide and preparation method of long-life room-temperature phosphorescent material

Abstract

The invention belongs to the field of phosphorescent materials, and provides a long-life room-temperature phosphorescent material based on natural polysaccharide and a preparation method thereof. The preparation method of the long-life room-temperature phosphorescent material comprises the following steps: uniformly grinding boric acid, urea and natural polysaccharide molecules, placing the obtained solid mixture in a beaker for heating treatment, naturally cooling to room temperature after the reaction is completed, and grinding to obtain the long-life room-temperature phosphorescent material. After the long-life room-temperature phosphorescent material powder disclosed by the invention is excited and removed by ultraviolet light, cyan, green or yellow green afterglow can be obtained according to different added polysaccharides, the average decay life of the room-temperature phosphorescent material can reach 582.86-1046.28 ms under room-temperature and air conditions, the afterglow luminescence time visible to naked eyes can reach 5-11s, and the afterglow luminescence time can reach 582.86-1046.28 ms under room-temperature and air conditions. And the preparation and post-treatment processes are convenient, and the raw materials are low in cost and environment-friendly. The obtained long-life room-temperature phosphorescent material has important application in the fields of information encryption, multi-color display and the like.

Description

Technical Field

[0001] The invention belongs to the field of phosphorescent materials, and in particular relates to a long-life room temperature phosphorescent material based on natural polysaccharide and a preparation method thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] In recent years, photoluminescent materials, including fluorescent and phosphorescent materials, have become a research hotspot. Compared with fluorescent materials, room temperature phosphorescent (RTP) materials have broad application prospects in information encryption, information anti-counterfeiting, bio-imaging, sensors, etc. due to their long decay lifetime, large Stokes shift, and no background fluorescence interference. However, so far, traditional room temperature phosphorescent materials often focus on heavy metals and inorganic systems, which may be cytotoxic; while pure organic room temperature phosphorescent materials often require complex and time-consuming synthesis processes. The preparation of environmentally friendly room temperature phosphorescent materials in a simple and low-energy way is a promising research direction.

[0004] The key point of room temperature phosphorescence is to promote the intersystem crossing process of singlet excitons to triplet excitons and inhibit the non-radiative transition process of triplet excitons. The method that can simultaneously provide heteroatoms containing lone pairs of electrons to promote the intersystem crossing process and rigid matrix to restrict the non-radiative transition process is an effective way to prepare room temperature phosphorescent materials. Compared with the lengthy and uncontrollable carbon dot synthesis process required by the heteroatom-doped carbon dot-matrix confinement system, the one-step heat treatment in situ preparation of room temperature phosphorescent materials is more favored. As an economical, green and renewable biomass resource, natural polysaccharides such as cellulose have been widely used as rigid matrices to restrict the non-radiative transition of chromophores to prepare room temperature phosphorescent materials. Although cellulose and starch polysaccharides themselves have weak room temperature phosphorescent properties, their luminescent properties are poor. Therefore, the preparation of room temperature phosphorescent materials using polysaccharides as chromophores has always been mainly based on modification and preparation of carbon dots. The reaction steps are relatively complicated and subject to many restrictions. Therefore, the search for a polysaccharide-based room temperature phosphorescent material that is easy to prepare and has a long life has attracted the attention of many researchers. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a long-life room temperature phosphorescent material based on natural polysaccharides. The present invention is the first to prepare a long-life room temperature phosphorescent material using polysaccharides as chromophores. Not only is the phosphorescence quantum efficiency high, but the preparation method is simple, the precursor cost is low, and it is green and environmentally friendly.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: The first aspect of the present invention provides a method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides, comprising: Grind urea, boric acid and polysaccharide solids evenly to obtain a reactant; The reactant is subjected to a one-step heat treatment, and after the reaction is completed, the reactant is cooled, the product is collected, and ground to obtain a long-life room temperature phosphorescent material; Wherein, the polysaccharide is selected from at least one of microcrystalline cellulose, sodium carboxymethyl cellulose, α-cellulose, corn starch, chitin and chitosan.

[0007] In some embodiments, the mass ratio of urea to boric acid is 2:1-1.5.

[0008] In some embodiments, the ratio of the polysaccharide to the total mass of urea and boric acid is 1-1.5:45.

[0009] In some embodiments, the temperature of the one-step heat treatment is 200-240°C.

[0010] In some embodiments, the one-step heat treatment lasts for 40-60 minutes.

[0011] The second aspect of the present invention provides a long-life room temperature phosphorescent material based on natural polysaccharides prepared by the above method.

[0012] In some embodiments, the average decay lifetime of the long-life room temperature phosphorescent material is 582.86 ms-1046.28 ms in a room temperature air environment, and the resolution time for the naked eye is 5-11 s.

[0013] In some embodiments, the long-life room temperature phosphorescent material has an emission peak at 478-530 nm under an excitation wavelength of 300-360 nm.

[0014] In some embodiments, when the polysaccharide is microcrystalline cellulose nanoparticles, the optimal excitation wavelength is 310 nm and the optimal emission wavelength is 478 nm; In some embodiments, when the polysaccharide is sodium carboxymethyl cellulose, the optimal excitation wavelength is 360 nm and the optimal emission wavelength is 530 nm; In some embodiments, when the polysaccharide is α-cellulose, the optimal excitation wavelength is 318 nm and the optimal emission wavelength is 490 nm; In some embodiments, when the polysaccharide is corn starch, the optimal excitation wavelength is 340 nm and the optimal emission wavelength is 530 nm; In some embodiments, when the polysaccharide is chitin, the optimal excitation wavelength is 300 nm and the optimal emission wavelength is 503 nm.

[0015] The third aspect of the present invention provides the application of the above-mentioned long-life room temperature phosphorescent material based on natural polysaccharide in the fields of information encryption, anti-counterfeiting, sensing, and multi-color display.

[0016] Beneficial effects of the present invention (1) The polysaccharide-based long-lifetime room temperature phosphorescent material provided by the present invention can emit multi-color phosphorescence that can be distinguished by the naked eye after the ultraviolet excitation light is turned off. The phosphorescence color ranges from cyan to yellow-green, and the maximum emission range is from 478nm to 530nm. Moreover, the emission wavelength and life span can be adjusted only by changing the added polysaccharide. The average decay life of the multi-color polysaccharide-based long-lifetime room temperature phosphorescent material can reach 582.86ms-1046.28ms in a room temperature air environment, and the afterglow luminescence time that can be distinguished by the naked eye can reach 5-11s in a room temperature air environment; (2) The preparation process of the polysaccharide-based long-life room temperature phosphorescent material provided by the present invention is simple and rapid, does not require complicated processes, expensive equipment and harsh operating environment, and uses cheap and readily available industrial raw materials and sustainable resources, so the preparation cost is low; (3) The polysaccharide-based long-life room temperature phosphorescent material provided by the present invention has great potential application value in the fields of information encryption, anti-counterfeiting, sensing, multi-color display, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 The optimal phosphorescence excitation and emission spectra of the MCC-UB composite room temperature phosphorescent material prepared in Example 1.

[0019] Figure 2 The optimal phosphorescence excitation and emission spectra of the CMC-UB composite room temperature phosphorescent material prepared in Example 2.

[0020] Figure 3 The optimal phosphorescence excitation and emission spectra of the α-cel-UB composite room temperature phosphorescent material prepared in Example 3.

[0021] Figure 4 The optimal phosphorescence excitation and emission spectra of the Sta-UB composite room temperature phosphorescent material prepared in Example 4.

[0022] Figure 5 The optimal phosphorescence excitation and emission spectra of the Chi-UB composite room temperature phosphorescent material prepared in Example 5.

[0023] Figure 6 The optimal phosphorescence excitation and emission spectra of the Cts-UB composite room temperature phosphorescent material prepared in Example 6.

[0024] Figure 7 This is the phosphorescence time-resolved spectrum of the polysaccharide-UB material prepared in Examples 1-6 under the optimal emission conditions.

[0025] Figure 8 This is a phosphorescence emission spectrum of the MCC-UB composite room temperature phosphorescent material prepared in Example 1 under different excitation lights.

[0026] Fig. 9 Transmission electron microscope images of the room temperature phosphorescent material prepared in Example 1 (a) and the room temperature phosphorescent material prepared in Comparative Example 1 (b).

[0027] Fig.10 These are the effects diagrams for information encryption applications, with real digital photos of the "8888" pattern composed of MCC powder and four polysaccharide-UB powders taken at different times after the 365nm ultraviolet light was turned off. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are exemplary and are 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 meanings as those commonly understood by those skilled in the art 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 intended to explain the present invention rather than to limit it.

[0030] The test methods in the following examples and comparative examples are all commonly used methods in the industry and are not specifically described here.

[0031] Example 1 A method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides comprises the following steps: Grind 1500 mg of urea, 750 mg of boric acid and 50 mg of microcrystalline cellulose evenly to obtain a reactant, and place the reactant in a beaker for a one-step heat treatment (200°C, 40 min). After the reaction is completed, cool naturally to room temperature, grind the product to obtain a long-life room temperature phosphorescent material.

[0032] The optimal phosphorescence excitation and emission spectra of the composite long-life room temperature phosphorescent material in which the microcrystalline cellulose nanoparticles prepared in this example are uniformly dispersed and embedded in an amorphous matrix are as follows: Figure 1 As shown, from Figure 1 It can be seen that the optimal excitation wavelength is 310nm and the optimal emission wavelength is 478nm.

[0033] The phosphorescence time-resolved spectrum of the composite long-lifetime room temperature phosphorescent material in which the microcrystalline cellulose nanoparticles prepared in this example are uniformly dispersed and embedded in an amorphous matrix is ​​shown in FIG. Figure 7 As shown in middle a, the data fitting results show that the phosphorescence decay lifetime reaches 695.38ms.

[0034] The phosphorescence emission spectra of the composite long-life room temperature phosphorescent material in which the microcrystalline cellulose nanoparticles prepared in this example are uniformly dispersed and embedded in an amorphous matrix at different excitation wavelengths are as follows: Figure 8 As shown, from Figure 8 It can be seen that the phosphorescence emission peak of MCC-UB slightly red-shifts with the increase of excitation wavelength, and 310nm is the optimal excitation wavelength.

[0035] The transmission electron microscopy image of the composite long-life room temperature phosphorescent material in which the microcrystalline cellulose nanoparticles prepared in this example are uniformly dispersed and embedded in an amorphous matrix is ​​shown in FIG. Fig. 9 As shown in a, from Fig. 9 As can be seen in (a), the MCC nanoparticles are uniformly dispersed and embedded in the amorphous matrix.

[0036] Example 2 A method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides comprises the following steps: Grind 1500 mg of urea, 750 mg of boric acid and 50 mg of sodium carboxymethyl cellulose evenly to obtain a reactant, and place the reactant in a beaker for a one-step heat treatment (200°C, 40 min). After the reaction is completed, cool naturally to room temperature, grind the product to obtain a long-life room temperature phosphorescent material.

[0037] The optimal phosphorescence excitation and emission spectra of the long-life room temperature phosphorescent material prepared in this embodiment are as follows: Figure 2 As shown, from Figure 2 It can be seen that the optimal excitation wavelength is 360nm and the optimal emission wavelength is 530nm.

[0038] The phosphorescence time-resolved spectrum of the composite long-lifetime room temperature phosphorescent material in which sodium carboxymethyl cellulose nanoparticles are uniformly dispersed and embedded in an amorphous matrix is ​​shown in FIG. Figure 7 As shown in middle b, the data fitting results show that the phosphorescence decay lifetime reaches 582.86ms.

[0039] Example 3 A method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides comprises the following steps: 1500 mg of urea, 750 mg of boric acid and 50 mg of α-cellulose were ground evenly to obtain the reactants to be used. The obtained reactants to be used were placed in a beaker for one-step heat treatment (200 °C, 40 min); after the reaction was completed, it was naturally cooled to room temperature, and the obtained product was ground to obtain a long-lived room temperature phosphorescent material.

[0040] The best phosphorescence excitation and emission spectra of the long-lived room temperature phosphorescent material prepared in this example are as Figure 3 shown. It can be seen from Figure 3 that the best excitation wavelength is 318 nm and the best emission wavelength is 490 nm.

[0041] The phosphorescence time-resolved spectrum of the composite long-lived room temperature phosphorescent material with α-cellulose nanoparticles uniformly dispersed and embedded in the amorphous matrix prepared in this example is as Figure 7 shown in c. The data fitting results show that the phosphorescence decay lifetime reaches 777.72 ms.

[0042] Example 4 A preparation method of a long-lived room temperature phosphorescent material based on natural polysaccharides, including the following steps: 1500 mg of urea, 750 mg of boric acid and 50 mg of corn starch were ground evenly to obtain the reactants to be used. The obtained reactants to be used were placed in a beaker for one-step heat treatment (200 °C, 40 min); after the reaction was completed, it was naturally cooled to room temperature, and the obtained product was ground to obtain a long-lived room temperature phosphorescent material.

[0043] The best phosphorescence excitation and emission spectra of the long-lived room temperature phosphorescent material prepared in this example are as Figure 4 shown. It can be seen from Figure 4 that the best excitation wavelength is 340 nm and the best emission wavelength is 530 nm.

[0044] The phosphorescence time-resolved spectrum of the composite long-lived room temperature phosphorescent material with corn starch nanoparticles uniformly dispersed and embedded in the amorphous matrix prepared in this example is as Figure 7 shown in d. The data fitting results show that the phosphorescence decay lifetime reaches 639.9 ms.

[0045] Example 5 A preparation method of a long-lived room temperature phosphorescent material based on natural polysaccharides, including the following steps: 1500 mg of urea, 750 mg of boric acid and 50 mg of chitin were ground evenly to obtain the reactants to be used. The obtained reactants to be used were placed in a beaker for one-step heat treatment (200 °C, 40 min); after the reaction was completed, it was naturally cooled to room temperature, and the obtained product was ground to obtain a long-lived room temperature phosphorescent material.

[0046] The optimal phosphorescence excitation and emission spectra of the long-life room temperature phosphorescent material prepared in this embodiment are as follows: Figure 5 As shown, from Figure 3 It can be seen that the optimal excitation wavelength is 340nm and the optimal emission wavelength is 510nm.

[0047] The phosphorescence time-resolved spectrum of the composite long-life room temperature phosphorescent material in which chitosan nanoparticles are uniformly dispersed and embedded in an amorphous matrix is ​​shown in FIG. Figure 7 As shown in middle e, the data fitting results show that the phosphorescence decay lifetime reaches 1046.28ms.

[0048] Example 6 A method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides comprises the following steps: Grind 1500 mg of urea, 750 mg of boric acid and 50 mg of chitosan evenly to obtain a reactant, and place the reactant in a beaker for a one-step heat treatment (200°C, 40 min); after the reaction is completed, cool naturally to room temperature, grind the product to obtain a long-life room temperature phosphorescent material.

[0049] The optimal phosphorescence excitation and emission spectra of the long-life room temperature phosphorescent material prepared in this embodiment are as follows: Figure 6 As shown, from Figure 6 It can be seen that the optimal excitation wavelength is 300nm and the optimal emission wavelength is 503nm.

[0050] The phosphorescence time-resolved spectrum of the composite long-lifetime room temperature phosphorescent material in which chitosan nanoparticles are uniformly dispersed and embedded in an amorphous matrix is ​​shown in FIG. Figure 7 As shown in middle f, the data fitting results show that the phosphorescence decay lifetime reaches 657.65ms.

[0051] Example 7 Fig.10 This is the effect diagram of information encryption application. MCC-UB, α-cel-UB, Chi-UB, and CMC-UB powders are used to coat parts 9, 5, 2, and 7 of the "8888" pattern respectively, and MCC powder is used to coat the other parts of the "8888" pattern. The real digital photos are taken at different times after the 365nm ultraviolet light is turned off.

[0052] Comparative Example 1 A method for preparing a room temperature phosphorescent material comprises the following steps: Grind 1500 mg of urea and 750 mg of boric acid evenly to obtain a reactant, place the reactant in a beaker and perform a heat treatment (200°C, 40 min); after the reaction is completed, cool naturally to room temperature, grind the product to obtain a room temperature phosphorescent material.

[0053] The phosphorescence intensity of the room temperature phosphorescent material obtained in this comparative example is much lower than that of the long-life room temperature phosphorescent material obtained in Examples 1-6; and the phosphorescence time of the room temperature phosphorescent material under room temperature is about 4s, which is lower than that of the long-life room temperature phosphorescent material obtained in Examples 1-6.

[0054] In this comparative example, only urea and boric acid are used as raw materials to prepare a room temperature phosphorescent material. The transmission electron microscope image of the room temperature phosphorescent material is as follows: Fig. 9 As shown in b, there are no MCC nanoparticles, only an amorphous matrix.

[0055] Comparative Example 2 The difference from Example 1 is that sodium alginate is used instead of microcrystalline cellulose. The specific preparation method comprises: Grind 1500 mg of urea, 750 mg of boric acid and 50 mg of sodium alginate evenly to obtain a reactant, and place the reactant in a beaker for a one-step heat treatment (200°C, 40 min). After the reaction is completed, cool naturally to room temperature, and grind the product to obtain a final product.

[0056] The test results show that the material is carbonized and has no room temperature phosphorescence emission phenomenon.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides, characterized in that: include: Grind urea, boric acid and polysaccharide solids evenly to obtain a reactant; The reactant is subjected to a one-step heat treatment, and after the reaction is completed, the reactant is cooled, the product is collected, and ground to obtain a long-life room temperature phosphorescent material; Wherein, the polysaccharide is selected from at least one of microcrystalline cellulose, sodium carboxymethyl cellulose, α-cellulose, corn starch, chitin and chitosan.

2. The method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides according to claim 1, characterized in that: The mass ratio of the urea to the boric acid is 2:1-1.

5.

3. The method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides according to claim 1, characterized in that: The ratio of the polysaccharide to the total mass of urea and boric acid is 1-1.5:

45.

4. The method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides according to claim 1, characterized in that: The temperature of the one-step heat treatment is 200-240°C.

5. The method for preparing a long-life room temperature phosphorescent material based on natural polysaccharides according to claim 1, characterized in that: The time of the one-step heat treatment is 40-60 minutes.

6. A natural polysaccharide-based long-life room temperature phosphorescent material prepared by the method described in any one of claims 1 to 5.

7. The long-life room temperature phosphorescent material based on natural polysaccharide according to claim 6, characterized in that: The average decay lifetime of the long-life room temperature phosphorescent material is 582.86ms-1046.28ms in a room temperature air environment, and the resolution time of the naked eye is 5-11s.

8. The long-life room temperature phosphorescent material based on natural polysaccharide according to claim 6, characterized in that: The long-life room temperature phosphorescent material has an emission peak at 478-530 nm under an excitation wavelength of 300-360 nm.

9. The long-life room temperature phosphorescent material based on natural polysaccharide according to claim 6, characterized in that: When the polysaccharide is microcrystalline cellulose nanoparticles, the optimal excitation wavelength is 310 nm and the optimal emission wavelength is 478 nm; Or, when the polysaccharide is sodium carboxymethyl cellulose, the optimal excitation wavelength is 360 nm and the optimal emission wavelength is 530 nm; Or, when the polysaccharide is α-cellulose, the optimal excitation wavelength is 318 nm and the optimal emission wavelength is 490 nm; Or, when the polysaccharide is corn starch, the optimal excitation wavelength is 340 nm and the optimal emission wavelength is 530 nm; Or, when the polysaccharide is chitin, the optimal excitation wavelength is 300 nm and the optimal emission wavelength is 503 nm.

10. Application of the long-life room temperature phosphorescent material based on natural polysaccharides according to any one of claims 6 to 9 in the fields of information encryption, anti-counterfeiting, sensing, and multi-color display.

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