Preparation method of long-lasting transparent wood and long-lasting transparent wood prepared therefrom

Abstract

This invention aims to recycle light and other energy sources using natural materials. It proposes a novel method for preparing transparent, color-adjustable, luminescent wood. By confining the luminescent molecules with a rigid polymer, the long-lasting luminescence of the phosphorescent molecules is achieved. This method involves filling the treated wood with PMMA, a material with room-temperature phosphorescence properties. To address performance limitations such as the lack of adjustable color for long-lasting luminescence, a blend of multiple luminescent molecules is used to achieve multi-color tunable long-lasting luminescence wood, and to construct long-lasting white light materials.

Description

Technical Field

[0001] The invention belongs to the field of luminescent materials, and in particular relates to a preparation method of long-afterglow transparent wood and the prepared long-afterglow transparent wood. Background Art

[0002] As human society continues to develop, people are increasingly aware of the importance of addressing future energy crises and strengthening environmental protection. The concept of green and sustainable development has become a core pillar of future development in the materials industry. Natural wood, as a renewable resource and the most widely used natural material in the construction industry, has long garnered significant attention within the industry. Wood is highly biodegradable and readily available. However, as living organisms, plants have long been limited by limitations such as size, defects, and the need to balance life. Their performance has long been unable to meet modern demands, limiting their application to traditional fields such as architecture and furniture.

[0003] Improving the functions and performance of natural materials and expanding their modern applications will play an important role in promoting the sustainable development of society. Functionalization of wood is one of the main methods to improve the properties of materials. Wood is a porous structure composed of longitudinally arranged cells. Due to the scattering of light by the porous structure and the absorption of light by lignin and other materials inside the wood, natural wood is opaque. In recent years, people have prepared transparent wood by delignifying and then filling the porous structure with polymer materials with similar refractive indices. The huge potential of transparent wood in building materials, solar energy materials, new energy storage materials, etc. has successfully attracted people's attention.

[0004] Fluorescent transparent wood has been developed by adding fluorescent molecules and quantum dots to transparent wood. However, this type of material is limited by the need for continuous excitation from an excitation light source. Therefore, long-lasting room-temperature phosphorescent transparent wood plays an important role in the application of optical materials and devices.

[0005] Room temperature phosphorescence (RTP) was first reported in the 1960s. With the continuous deepening of research, people have realized the application potential of RTP. The triplet excited state photons and electrons involved in RTP have great potential in many fields of technology, and ultra-long RTP is also of great significance for information security and biomedical applications. Currently, the most common RTP materials are mostly inorganic phosphorescent materials, but they still have many inherent disadvantages, such as the scarcity and high toxicity of rare metal resources, complex and harsh preparation conditions, and the lack of economic practicality of most materials. In comparison, organic materials have many advantages such as good processability, biocompatibility, low cost, and abundant sources. Therefore, pure organic light-emitting bodies with long-lasting room temperature phosphorescence have attracted widespread attention in recent years.

[0006] Several approaches exist to achieve room-temperature phosphorescence (RTP) in organic materials, such as through weak intermolecular hydrogen bonding to produce a time-dependent afterglow color or by leveraging the interaction of multiple molecules to achieve time-dependent afterglow color. Generally speaking, achieving persistent RTP in organic materials often involves two approaches: first, introducing carbonyl groups, heteroatoms, heavy atoms, or other functional groups to enhance the interaction between the phosphorescent molecules and the organic matrix, promoting intersystem crossing. Alternatively, phosphorescence can be enhanced by suppressing the nonradiative relaxation process during phosphorescence emission. For most organic polymers, amorphous regions often exhibit a quenching effect on phosphorescence at room temperature. Some research has developed amorphous RTP systems, primarily by creating a rigid environment through intermolecular interactions to suppress nonradiative relaxation and enhance phosphorescence. However, currently available systems require sophisticated molecular design and complex preparation processes. In most cases, a simpler interaction system leads to a more stable, easily processable, and commercially viable organic RTP material.

[0007] Therefore, there is an urgent need in the prior art to provide transparent wood made of organic phosphorescent materials with stable luminous properties and easy processing. Summary of the Invention

[0008] In view of the shortcomings of the prior art described above, the purpose of the present invention is to achieve the reuse of light and other energy sources based on natural materials. A new method for preparing transparent luminous wood with adjustable afterglow color is proposed. By using rigid polymers to restrict luminescent molecules, long-lasting luminescence of phosphorescent molecules is achieved. By filling PMMA material with room-temperature phosphorescent properties into treated wood, multi-color adjustable long-lasting glow wood is achieved by mixing multiple luminescent molecules to address performance defects such as the non-adjustable long-lasting glow color, and the construction of white light long-lasting glow materials is realized, which is used to solve the problems in the prior art.

[0009] To achieve the above-mentioned object and other related objects, the present invention provides a method for preparing long-lasting transparent wood, characterized in that the preparation method comprises the following steps: (1) cutting natural wood into wood chips; (2) removing lignin from the wood chips of step (1); (3) prepolymerizing methyl methacrylate (MMA) doped with phosphorescent small molecules, wherein the phosphorescent small molecules are selected from one or more of naphthalene, pyrene, carbazole, or phenanthrene, and quenching the reaction after the prepolymerization is completed; and (4) completely immersing the wood chips from which the lignin is removed in step (2) in the prepolymerized methyl methacrylate prepared in step (3), and polymerizing under heating conditions to obtain long-lasting transparent wood.

[0010] The design of wood transparency is achieved by removing the lignin from the wood (through delignification). The main remaining substances are cellulose and hemicellulose complexes. The average refractive index of these components is n≈1.53. When the interior of the wood fiber is infiltrated and filled with polymethyl methacrylate (PMMA, n≈1.49), a polymer with a similar refractive index, it becomes transparent.

[0011] MMA with phosphorescent small molecules (naphthalene, pyrene, carbazole, phenanthrene, etc.) added thereto was pre-polymerized in different flasks to reach a certain viscosity and the reaction was quenched. The delignified wood was completely immersed in the viscous pre-polymerized MMA solution and vacuum-filled. Finally, the filled wood was taken out and placed in an 80°C oven for post-polymerization to obtain transparent long-lasting glow wood. The samples were named Nap@PMMA@wood, Pyr@PMMA@wood, Cz@PMMA@wood, and Phe@PMMA@wood. As certain embodiments of the present invention, the natural wood in step (1) was selected from balsa wood.

[0012] The four molecules of naphthalene, pyrene, carbazole and phenanthrene correspond to phosphorescence of different wavelengths respectively. By doping the above four molecules respectively, phosphorescence emission of green light, red light and blue light is obtained. By mixing and doping different phosphorescent molecules in any proportion, different multi-color luminescence such as yellow light and white light can be obtained.

[0013] As certain embodiments of the present invention, the size of the wood chips is 1 μm to 10 cm.

[0014] The size of the wood chips is selected from 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 150 μm, 200 μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 600μm, 650μm, 700μm, 750μm, 800μm, 850μm, 900μm, 1mm, 2mm, 3mm, 4mm, 5mm , 6mm, 7mm, 8mm, 9mm, 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, 8 00mm, 900mm, 1cm, 1.5cm, 2cm, 2.5cm, 3cm, 3.5cm, 4cm, 4.5cm, 5cm, 5.5cm, 6cm, 6.5cm, 7cm, 7.5cm, 8cm, 8.5cm, 9cm, 9.5cm, 10cm.

[0015] As certain embodiments of the present invention, the wood chips in step (1) are wood chips with a volume size of 2cm*2cm*1mm.

[0016] As certain embodiments of the present invention, the wood chips in step (1) are dried. As certain embodiments of the present invention, the wood chips in step (1) are dried at 100° C. for 24 hours.

[0017] In certain embodiments of the present invention, the lignin is removed by acidolysis using an oxidizing acid in step (2). In certain embodiments of the present invention, the oxidizing acid is selected from sodium chlorite. In certain embodiments of the present invention, the oxidizing acid in step (2) is dissolved in an acidic buffer solution.

[0018] As certain embodiments of the present invention, the pH of the acidic buffer solution in step (2) is 4.0.

[0019] As certain embodiments of the present invention, the acidic buffer solution in step (2) is an acetic acid buffer solution.

[0020] As certain embodiments of the present invention, in step (2), the concentration of sodium chlorite in the acetate buffer solution is 1% w / v;

[0021] In certain embodiments of the present invention, the volume ratio of the oxidizing acid to the wood chips in step (2) is between 100:1 and 30:1. In certain embodiments of the present invention, the volume ratio of the oxidizing acid solution to the wood chips is 40:1. The volume ratio of the oxidizing acid to the wood chips in step (2) is selected from 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1, 95:1, and 100:1.

[0022] As certain embodiments of the present invention, the oxidative acid hydrolysis for removing lignin in step (2) is carried out at 60°C-95°C for 6-12 hours. As certain embodiments of the present invention, the oxidative acid hydrolysis for removing lignin in step (2) is carried out at 80°C for 8 hours.

[0023] The reaction temperature for removing lignin by oxidative acid hydrolysis in step (2) is selected from 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, and 95°C.

[0024] The reaction time for the oxidative acid hydrolysis to remove lignin in step (2) is selected from 6, 7, 8, 9, 10, 11, and 12 hours.

[0025] As certain embodiments of the present invention, in the prepolymerization described in step (3), in the prepolymerization described in step (3), the polymerization initiator is benzoyl peroxide, lauroyl peroxide, isopropyl benzene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, diisopropyl benzene peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyvalerate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, azobisisobutyronitrile (AIBN), benzoyl peroxide / sucrose, tert-butyl hydroperoxide / rongalite, tert-butyl hydroperoxide / sodium metabisulfite, or benzoyl peroxide / N,N-dimethylaniline. Ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / bleaching agent, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / / N,N-diethylaniline, benzoyl peroxide / ferrous pyrophosphate, potassium persulfate / silver nitrate, persulfate / thiol, cumene hydroperoxide / ferrous chloride, potassium persulfate / ferrous chloride, hydrogen peroxide / ferrous chloride, cumene hydroperoxide / tetraethyleneimine.

[0026] As certain embodiments of the present invention, in the prepolymerization described in step (3), the polymerization initiator is azobisisobutyronitrile.

[0027] As certain embodiments of the present invention, the concentration of the phosphorescent small molecule in methyl methacrylate in step (3) is 0.00025 mg / mL-0.08 mg / mL, and the concentration of the polymerization initiator in methyl methacrylate is 0.2-1.8% w / v.

[0028] The concentration of the phosphorescent small molecule in methyl methacrylate in step (3) is selected from 0.00025, 0.00026, 0.00027, 0.00028, 0.00029, 0.0003, 0.0004, 0.0005, 0.0006, 0.0007, 0.0008, 0.0009, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08 mg / mL.

[0029] The concentration of the polymerization initiator in methyl methacrylate is selected from 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8% w / v.

[0030] As certain embodiments of the present invention, the concentration of the phosphorescent small molecule in step (3) is 0.02 mg / mL and the concentration of AIBN is 0.6% w / v.

[0031] As certain embodiments of the present invention, the prepolymerization reaction conditions in step (3) are 70°C-85°C for 15-50 minutes to obtain prepolymerized methyl methacrylate. As certain embodiments of the present invention, the prepolymerization reaction conditions in step (3) are 80°C for 25 minutes.

[0032] The prepolymerization reaction temperature in the step (3) is selected from 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, ℃.

[0033] The prepolymerization reaction time in the step (3) is selected from 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, and 50 minutes.

[0034] As certain embodiments of the present invention, the reaction system is sufficiently cooled after the prepolymerization reaction in step (3) to quench the reaction; preferably, the reaction system is quenched in an ice-water mixture.

[0035] As certain embodiments of the present invention, the quenched reaction system in step (3) is subjected to defoaming treatment. As certain embodiments of the present invention, in step (3), the quenched reaction system is allowed to stand for defoaming at room temperature or is ultrasonically defoamed at low temperature.

[0036] As certain embodiments of the present invention, in step (4), the wood chips from which lignin has been removed are removed from the prepolymerized methyl methacrylate and the vacuum treatment is maintained for 30 minutes under vacuum conditions.

[0037] As certain embodiments of the present invention, the wood chips from which lignin has been removed in step (4) are taken out from the pre-polymerized methyl methacrylate and treated in vacuum for more than two times.

[0038] As certain embodiments of the present invention, in step (4), the wood chips from which lignin has been removed are taken out from the pre-polymerized methyl methacrylate and treated in vacuum three times.

[0039] As certain embodiments of the present invention, in step (4), the vacuum-treated wood chips are sandwiched between glass sheets and heated for polymerization.

[0040] As certain embodiments of the present invention, in step (4), the glass sheet is wrapped with aluminum foil.

[0041] As certain embodiments of the present invention, in step (4), the heating temperature is 80° C. and the heating time is 4 hours.

[0042] As certain embodiments of the present invention, the oxidative acid hydrolysis to remove lignin in step (2) is carried out under stirring conditions.

[0043] As certain embodiments of the present invention, after the oxidative acid hydrolysis reaction for removing lignin in step (2) is completed, the wood chips from which the lignin has been removed are washed with deionized water, and then the wood chips from which the lignin has been removed are washed with ethanol having a concentration of 99% v / v or above, and then the wood chips from which the lignin has been removed are washed with a mixed solution of ethanol and acetone in a volume ratio of 1:1, and then the wood chips from which the lignin has been removed are washed with acetone, and after washing, the wood chips from which the lignin has been removed are stored in acetone.

[0044] As certain embodiments of the present invention, the washing with ethanol at a concentration of 99% v / v or above, the washing with a mixed solution of ethanol and acetone, and the washing with acetone in step (2) are repeated three times respectively.

[0045] As certain embodiments of the present invention, the phosphorescent small molecule in step (3) is selected from carbazole, pyrene, and naphthalene, wherein the ratio of carbazole, pyrene, and naphthalene is 50:1:2.

[0046] As certain embodiments of the present invention, the ratio of carbazole, pyrene and naphthalene is 0:1:1.

[0047] As certain embodiments of the present invention, the ratio of carbazole, pyrene and naphthalene is 0:1:2.

[0048] By selecting phosphorescent small molecules and adjusting the ratio of different phosphorescent small molecules, long-afterglow wood with afterglow of white light, red light and yellow light can be obtained respectively.

[0049] The present application also provides long afterglow wood prepared by the preparation method.

[0050] As described above, the method for preparing long-lasting transparent wood and the long-lasting transparent wood prepared therefrom of the present invention have the following characteristics:

[0051] Beneficial effects:

[0052] 1.Higher transparency

[0053] PMMA is inherently highly transparent and is an excellent polymer material. The refractive index of PMMA is similar to that of delignified cell wall components, meeting the requirements for wood transparency treatment and enabling the production of high-quality transparent wood. References indicate that transparent wood consists of a delignified cellulose skeleton filled with polymer materials. Wood transparency treatment technology is already largely mature, providing a good foundation for optical functionalization. This also allows for the inherent excellent properties of room-temperature phosphorescent polymers to be fully utilized. The resulting material boasts a transmittance exceeding 80%, far exceeding that of pristine wood.

[0054] 2. Long afterglow

[0055] While PMMA provides a transparent environment, it acts as a rigid molecular chain to wrap around the phosphorescent molecules. Under the action of the rigid environment provided by the PMMA chain, the competition for triplet state transitions of the phosphorescent molecules is greatly reduced, allowing the phosphorescent molecules to exhibit strong phosphorescent properties even under room temperature conditions through ultraviolet light irradiation. The inventors selected four simple small molecules: naphthalene, carbazole, pyrene, and phenanthrene as luminescence sources. These three molecules have two advantages. First, they have a simple structure and are not prone to other uncontrollable chemical reactions during the polymerization reaction of the matrix (PMMA) that would change the energy level and affect phosphorescent emission. Second, the triplet energy level emission ranges of naphthalene, carbazole, and pyrene are within the visible light range and have some differences. Their phosphorescent signal ranges are within the green, blue, and red wavelength ranges, respectively, which can achieve multi-color phosphorescent emission. This also provides more operational possibilities during the color mixing experiment.

[0056] After ultraviolet excitation, the transparent wood samples doped with naphthalene, carbazole, and pyrene respectively emitted bright green, blue, and red afterglows, with the afterglow lasting for nearly ten seconds. In the chromaticity spectrum, it can be seen that the three sample luminescence points marked in the figure are consistent with the emission colors observed by the naked eye. The afterglow wavelengths of the three samples are respectively concentrated in the red, green, and blue regions shown in the chromaticity diagram between 400nm-550nm, 450nm-600nm, and 550nm-700nm. We found that the chromatographic performance of only three phosphorescent molecules encompasses the wavelength range from 400nm to 700nm, almost achieving coverage of the visible light region (visible light wavelength range 380-780nm). The inventors tested the afterglow lifetime of the samples with these three different afterglow colors, and the phosphorescence lifetimes were 0.95, 0.51, and 0.38s, respectively.

[0057] 3. Long afterglow color control

[0058] Using a PMMA system doped with phosphorescent molecules, three simple small molecules—naphthalene, carbazole, and pyrene—were selected as luminescent materials. The PMMA samples, after polymerization, exhibited green, blue, and red light under UV excitation, respectively, without significantly affecting the transparency and refractive index of the PMMA. These molecules lack distinct surface functional groups and exhibit simple interactions. The color mixing of these molecules follows the principle of additive color mixing, allowing for the long-lasting glow to be controlled by adjusting the ratio of the three molecules.

[0059] After achieving long-lasting three-color emission from transparent wood, researchers then adjusted the concentrations of different small molecules according to their ratios to create samples with time-varying afterglow colors. They also attempted to produce samples that emit white light. This tunable emission color is possible thanks to the selectivity and long triplet lifetime of the fluorescent molecules.

[0060] 4.Excellent mechanical properties

[0061] Lignin in wood enables it to maintain exceptional rigidity, supporting the plant's weight. The combination of regularly arranged micron-sized fiber channels and polymer fillers largely preserves the wood's inherent mechanical properties. This method preserves the wood's original pore structure, maximizing its mechanical properties. However, after removing the lignin, its mechanical properties change. The elastic modulus of original wood is approximately 386 MPa, while after delignification, it decreases to 0.37 MPa. Although mechanical properties decrease after delignification, they still compare favorably to current long-lasting luminescent materials.

[0062] 5. In terms of composition, the main material required for the preparation of this method is natural wood, so it has the advantages of a wide range of raw material sources, pure natural, pollution-free, and biodegradable.

[0063] 6. The method of the present invention has a simple operation process, requires few equipment, is energy-saving and efficient, and the prepared material has the ability to be scaled up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 Shown is the experimental design principle diagram of the present invention;

[0065] Figure 2 Shown is a schematic diagram of the experimental process of the present invention;

[0066] Figure 3(a) a picture of a log with transverse and longitudinal fiber structures of the present invention, (b) a picture of delignified wood with transverse and longitudinal fiber structures, (c) a picture of PMMA-filled transparent wood with transverse and longitudinal fiber structures, (d) a SEM picture of a log with transverse and longitudinal fiber structures, (e) a SEM picture of delignified wood with transverse and longitudinal fiber structures, and (f) a SEM picture of PMMA-filled transparent wood with transverse and longitudinal fiber structures;

[0067] Figure 4 Shown is the transmission spectrum of Nap@PMMA@wood of the present invention;

[0068] Figure 5 Shown are (a) afterglow images of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood under 275nm ultraviolet excitation of the present invention, (b) phosphorescence spectra of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood, (c) chromaticity diagram corresponding to the phosphorescence emission spectra of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood samples, and (d) a comparison diagram of phosphorescence lifetime decay curves of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood;

[0069] Figure 6 Shown are (a) the afterglow image of Nap / Cz / Pyr@PMMA@wood of the present invention under 275nm ultraviolet light excitation, (b) the phosphorescence spectrum of Nap / Cz / Pyr@PMMA@wood changing with time, and (c) the chromaticity diagram corresponding to the phosphorescence emission spectrum of the Nap / Cz / Pyr@PMMA@wood sample changing with time. DETAILED DESCRIPTION

[0070] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0071] It should be understood that the terms used in the examples of the present invention are intended to describe specific embodiments and are not intended to limit the scope of protection of the present invention. In the present specification and claims, unless otherwise expressly indicated, the singular forms "a," "an," and "the" include the plural forms. When numerical ranges are given in the examples, it should be understood that unless otherwise indicated, both endpoints of each numerical range and any value between the two endpoints may be used.

[0072] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. In addition to the specific methods, devices, and materials used in the examples, any prior art methods, devices, and materials similar or equivalent to those in the examples may be used to implement the present invention, based on the knowledge of the prior art by those skilled in the art and the disclosure of this invention.

[0073] Unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in the present invention all adopt conventional methods and techniques in this technical field and conventional techniques in related fields.

[0074] Example 1: Preparation of long afterglow luminous wood and schematic diagram of its principle:

[0075] This embodiment describes the entire process of preparing long afterglow luminous wood. The schematic diagram of the process is shown in FIG. Figure 2 .

[0076] Reagent pretreatment:

[0077] Naphthalene, pyrene, carbazole, phenanthrene, and AIBN were purified by recrystallization. Polymerization inhibitors in MMA were removed by filtration through basic alumina (Chemicals were purchased commercially and used without further purification unless otherwise stated.)

[0078] Delignification treatment:

[0079] The purchased balsa wood was cut horizontally and vertically into 1cm*1cm*1.5mm wood chips. The size of the cut wood can be adjusted according to the needs. An acidic buffer solution with a pH of 4.6 was prepared with acetic acid. A corresponding amount of sodium chlorite was dissolved in the acidic buffer solution to obtain a 1wt% sodium chlorite-acetic acid buffer solution.

[0080] Preparation of delignified wood

[0081] First, take a number of cut wood samples and take them out after drying at 100°C for 24 hours. The dried samples are placed in a prepared 1wt% sodium chlorite-acetic acid buffer solution. Heat the container in which the wood is soaked in an 80°C water bath for 8 hours. During the water bath heating, the solution is always kept in a stirring and flowing state to ensure that the wood is in full contact with the solution, but do not stir it too violently, otherwise it will easily damage the wood structure and form cracks, affecting subsequent experiments. Let the reacted system stand in the air and cool to room temperature. Wash the reacted wood with deionized water for more than three times, then replace the deionized water with ethanol with a purity of more than 99%, and then replace the ethanol solution with a 1:1 (volume ratio) mixed solution of ethanol and acetone, and finally replace it with acetone solution (gradual infiltration to achieve a better replacement effect). Repeat the above steps three times. Finally, store the delignined wood in acetone. Complete the delignification process.

[0082] Figure 3 (a) A photo of a log showing transverse and longitudinal fiber structures, and (b) a photo of delignification showing transverse and longitudinal fiber structures.

[0083] MMA Pre-Poly:

[0084] The phosphorescence spectra of four molecules, naphthalene, pyrene, carbazole, and phenanthrene, were referenced, and the corresponding phosphorescent chromophore (0.02 mg / mL) was selected according to the expected final phosphorescence color. The selected phosphor and AIBN (0.6%) were added to MMA. The mixture was degassed by freeze-thaw cycles and then prepolymerized at 80°C for 25 minutes. The reaction vessel was placed in an ice-water mixture to fully cool and quench the reaction. After the reaction was quenched, it was allowed to stand at room temperature for defoaming. If the viscosity is too high to be completely defoamed by standing alone, ultrasonic defoaming can be performed at low temperature. The prepolymerized MMA after defoaming was transferred to a mold that can hold delignification.

[0085] Figure 3 (c) is a picture of PMMA-filled transparent wood with transverse and longitudinal fiber structures, (d) is a SEM picture of logs with transverse and longitudinal fiber structures, (e) is a SEM picture of delignified wood with transverse and longitudinal fiber structures, and (f) is a SEM picture of PMMA-filled transparent wood with transverse and longitudinal fiber structures.

[0086] Polymer filling:

[0087] Completely submerge the delignified wood in pre-polymerized MMA, transfer it to a vacuum chamber, and maintain the vacuum for 30 minutes. Repeat the vacuum treatment three times to ensure full penetration of the MMA. The MMA-filled wood is then sandwiched between glass sheets wrapped in aluminum foil. (The aluminum foil serves to facilitate demolding after polymerization.) Finally, the sample is heated in an oven at 80°C for at least 4 hours to complete post-polymerization.

[0088] Example 2 Detection of polymerized long-lasting luminescent wood

[0089] The long afterglow luminescent wood prepared in Example 1 was tested:

[0090] Transmission spectra were collected using an Agilent Technologies Cary 5000 UV-visible-near-infrared spectrophotometer equipped with an integrating sphere accessory. Figure 4 The transmittance spectra of the original untreated wood and Nap@PMMA@wood of the present invention are shown, confirming that the transmittance of transparent wood is as high as over 80%.

[0091] The long-lasting-glow photophysical test of wood was carried out using a HORIBA Fluorolog-3 fluorescence spectrometer with an excitation wavelength of 275 nm and a CCD detector. Figure 5 Shown are (a) afterglow images of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood under 275nm ultraviolet excitation of the present invention, (b) phosphorescence spectra of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood, (c) chromaticity diagram corresponding to the phosphorescence emission spectra of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood samples, and (d) a comparison diagram of phosphorescence lifetime decay curves of Nap@PMMA@wood, Cz@PMMA@wood, and Pyr@PMMA@wood;

[0092] Figure 5 The phosphorescence spectrum, chromaticity diagram and lifetime spectrum prove that long-afterglow wood with the addition of different phosphorescent molecules can achieve bright multi-color luminescence and long-life phosphorescence emission.

[0093] Figure 6 Shown are (a) the afterglow image of Nap / Cz / Pyr@PMMA@wood of the present invention under 275nm ultraviolet light excitation, (b) the phosphorescence spectrum of Nap / Cz / Pyr@PMMA@wood changing with time, and (c) the chromaticity diagram corresponding to the phosphorescence emission spectrum of the Nap / Cz / Pyr@PMMA@wood sample changing with time. Figure 6 It is proved that by doping Nap / Cz / Pyr@PMMA@wood samples with multiple phosphorescent molecules at the same time in a certain proportion, long-afterglow wood with near-white light emission can be prepared, and the afterglow color can change over time.

[0094] The preparation method of this application uses organic molecules as phosphorescent chromophores, which can effectively improve transparency compared to inorganic particles. The transparency of this patent can be as high as 80%. In addition, this method does not contain heavy atoms (metals, halogen elements) and has the characteristics of high uniformity, easy processing, and low cost. By mixing the phosphorescent chromophores in different proportions, it is possible to prepare samples of various afterglow colors. By selecting phosphorescent small molecules such as carbazole, pyrene, and naphthalene, where the ratio of carbazole, pyrene, and naphthalene is 50:1:2, transparent wood with a white afterglow can be obtained; when the ratio of carbazole, pyrene, and naphthalene is adjusted to 0:1:1, transparent wood with a red afterglow can be obtained; when the ratio of carbazole, pyrene, and naphthalene is adjusted to 0:1:2, long-lasting yellow afterglow wood can be obtained.

[0095] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing long afterglow transparent wood, characterized in that: The preparation method comprises the following steps: (1) Cutting natural wood into wood chips; (2) removing lignin from the wood chips of step (1); (3) prepolymerizing methyl methacrylate doped with a phosphorescent small molecule, wherein the phosphorescent small molecule is selected from carbazole, pyrene, and naphthalene, wherein the ratio of carbazole, pyrene, and naphthalene is 50:1:2, or the ratio of carbazole, pyrene, and naphthalene is 0:1:1, or the ratio of carbazole, pyrene, and naphthalene is 0:1:2, and quenching the reaction after the prepolymerization is completed; (4) The wood chips from which lignin has been removed in step (2) are completely immersed in the prepolymerized methyl methacrylate prepared in step (3), and polymerized under heating conditions to obtain long-lasting transparent wood.

2. The preparation method according to claim 1, characterized in that The natural wood in step (1) is balsa wood; Or the size of the wood chip is 2cm*2cm*1mm; Or the wood chips are dried; the wood chips are dried at 100° C. for 24 hours.

3. The preparation method according to claim 1, characterized in that In step (2), oxidizing acid is used to remove lignin by acid hydrolysis; the oxidizing acid is sodium chlorite; The oxidizing acid is dissolved in an acidic buffer solution; The pH of the acidic buffer solution is 4.0; the acidic buffer solution is an acetate buffer solution; the concentration of sodium chlorite in the acetate buffer solution is 1% w / v; The volume ratio of the oxidative acid hydrolysis solution to the wood chips is between 100:1 and 30:1; The lignin removal reaction conditions are 60° C.-95° C. for 6-12 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that In the prepolymerization described in step (3), the polymerization initiator is benzoyl peroxide, lauroyl peroxide, isopropyl benzene hydroperoxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, diisopropyl benzene peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyvalerate, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, azobisisobutyronitrile, benzoyl peroxide / sucrose, tert-butyl hydroperoxide / rongalite, tert-butyl hydroperoxide / sodium metabisulfite, benzoyl peroxide / N,N- dimethylaniline, ammonium persulfate / sodium bisulfite, potassium persulfate / sodium bisulfite, hydrogen peroxide / tartaric acid, hydrogen peroxide / diaobaikai, ammonium persulfate / ferrous sulfate, hydrogen peroxide / ferrous sulfate, benzoyl peroxide / N,N-diethylaniline, benzoyl peroxide / ferrous pyrophosphate, potassium persulfate / silver nitrate, persulfate / thiol, cumene hydroperoxide / ferrous chloride, potassium persulfate / ferrous chloride, hydrogen peroxide / ferrous chloride, cumene hydroperoxide / tetraethyleneimine; or the prepolymerization reaction conditions are 70° C.-85° C. for 15-50 minutes to obtain prepolymerized methyl methacrylate; or after the prepolymerization reaction, the reaction system is sufficiently cooled to quench the reaction; the reaction system is quenched in an ice-water mixture; Or the quenched reaction system is subjected to defoaming treatment; the quenched reaction system is allowed to stand for defoaming at room temperature or is subjected to ultrasonic defoaming at low temperature.

5. The preparation method according to claim 4, characterized in that The polymerization initiator is azobisisobutyronitrile; the concentration of the phosphorescent small molecule in methyl methacrylate is 0.00025 mg / mL-0.08 mg / mL, and the concentration of the polymerization initiator in methyl methacrylate is 0.2% w / v-0.8% w / v; the concentration of the phosphorescent small molecule is 0.02 mg / mL and the concentration of azobisisobutyronitrile is 0.6% w / v; Alternatively, the prepolymerization reaction condition is 80° C. for 25 minutes.

6. The preparation method according to any one of claims 1 to 3, characterized in that In the step (4), the wood chips from which lignin has been removed are taken out from the prepolymerized methyl methacrylate and the vacuum treatment is maintained for 30 minutes under vacuum conditions; the wood chips from which lignin has been removed are taken out from the prepolymerized methyl methacrylate and treated in vacuum for more than two times; as well as The vacuum-treated wood chips were sandwiched between glass sheets and heated for polymerization; the glass sheets were wrapped with aluminum foil; the heating temperature was 80° C. and the heating time was 4 hours.

7. The preparation method according to claim 6, characterized in that The delignined wood chips were removed from the prepolymerized methyl methacrylate and treated three times in vacuum.

8. The preparation method according to claim 3, characterized in that The oxidative acid decomposition to remove lignin in step (2) is carried out under stirring conditions. After the oxidative acid hydrolysis reaction to remove lignin is completed, the wood chips from which lignin has been removed are washed with deionized water, and then washed with ethanol at a concentration of 99% v / v or above, and then washed with a mixed solution of ethanol and acetone in a volume ratio of 1:1, and then washed with acetone. After washing, the wood chips from which lignin has been removed are stored in acetone.

9. The preparation method according to claim 8, characterized in that The washing with ethanol at a concentration of 99% v / v or higher, the washing with a mixed solution of ethanol and acetone, and the washing with acetone were repeated three times respectively.

10. Long afterglow wood prepared according to the method for preparing long afterglow transparent wood according to any one of claims 1 to 9.

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