A photo-luminescent color-changing material, and a method of making and using the same

Abstract

The present application relates to a kind of photo luminescence color-changing materials and its preparation and application, the material is terephthalic acid or dimethyl terephthalate or its derivative crystal, its structure general formula is as follows: Wherein R1 It is CH3, CH2CH3, CH (CH3) 2 Or H, R2 It is OH or NH2. A series of p binary aromatic acid ester compound is obtained by simple synthesis step or commercial approach, and cultivate single crystal. Compared with prior art, the preparation method of the present application is simple, and luminescence color-changing is not dependent on single molecule photochemical reaction, but utilizes external light stimulation to promote the molecular rearrangement in crystal lattice, realizes the photo luminescence color-changing of material from blue light to purple light, and then to orange light. By adjusting substituent group, the luminescence color-changing range and response time of material can be flexibly regulated. The photo luminescence color-changing of such material is reversible after grinding or heating, and can be reused after solvent fumigation or cooling, so it can be prepared into anti-fake ink for screen printing, and also can be added into hydrogel to prepare flexible rewritable information storage material.

Description

Technical Field

[0001] This invention belongs to the field of material preparation and luminescent materials, specifically relating to the application of crystals of terephthalic acid or dimethyl terephthalate or their derivatives as photoluminescent color-changing materials, their preparation methods, and their applications in information storage, anti-counterfeiting encryption, etc. Background Technology

[0002] Stimulus-responsive luminescent materials exhibit photophysical properties that change in response to various external stimuli, thus possessing programmability and showing great potential in information storage, anti-counterfeiting encryption, bioimaging, and sensing detection. Among various external stimuli, light stimulation can conveniently and rapidly control and drive molecules, exhibiting superior spatiotemporal precision. However, most existing photoluminescent color-changing materials rely on chemical changes, that is, using external light stimulation to induce changes in the molecular chemical structure, thereby modulating their photophysical properties. These materials often require certain specific photoisomeric molecular building blocks (such as spiropyran, diarylene, azobenzene, etc.), making the synthesis steps cumbersome and unfavorable for on-demand molecular design. Furthermore, the photochemical change process is generally accompanied by a change in the material's appearance color, which greatly limits their application in information encryption and other fields. In recent years, research on regulating the photophysical properties of materials by altering molecular aggregation patterns has become increasingly common; for example, polymorphs of the same compound often exhibit different intrinsic luminescence. Inducing the aggregation of the same type of molecules into different aggregates allows for effective control of the photophysical properties of materials without complex synthetic processes, simplifying molecular design difficulties and providing new ideas for designing novel photoluminescent color-changing materials. However, current methods for obtaining materials with different aggregate states are still mainly limited to starting from discrete molecules and directly cultivating target aggregates (e.g., cultivating single crystals using solvents of different polarities), making it difficult to achieve spontaneous stimulated conversion between aggregates. Furthermore, due to the constant molecular structure, it is difficult for different aggregates to produce significant differences in emission color. Therefore, developing intelligent photoluminescent color-changing materials that are easy to synthesize and have a wide color-changing range, without relying on photochemical reactions, remains a significant challenge. Summary of the Invention

[0003] The purpose of this invention is to overcome the defects of the prior art by providing a class of photoluminescent color-changing materials that are simple in structure, easy to synthesize, and have a wide range of light emission and color change, as well as their preparation and application.

[0004] This invention develops a class of organic photoluminescent color-changing materials with simple structure, easy synthesis, and a wide range of luminescence and color change, which can be further applied to information storage and encryption. Addressing the shortcomings of existing technologies, this invention develops a crystal of terephthalic acid or dimethyl terephthalate or its derivatives as an organic photoluminescent color-changing material. Utilizing the weak but widespread electronic interactions between molecules in the aggregated state, the molecules in the crystal lattice undergo a minute rearrangement under external light stimulation. The periodically distributed electronic interactions in the crystal lattice amplify this minute rearrangement, causing the rearranged aggregates to emit light in the long-wavelength region, ultimately resulting in photoluminescence ranging from blue to purple, and then to orange-red, under external light stimulation. By adjusting the substituents, its derivatives exhibit different ranges of photoluminescent color-changing phenomena. The material's appearance color remains unchanged before and after the luminescence color change. Furthermore, the photoluminescence and color-changing phenomenon of this type of material is reversible after grinding or heating, and it can be reused after solvent fumigation or cooling; this material can be made into anti-counterfeiting ink for screen printing, or it can be added to hydrogel to prepare a flexible rewritable material.

[0005] The objective of this invention can be achieved through the following technical solution: a photoluminescent color-changing material, wherein the material is a crystal of terephthalic acid or dimethyl terephthalate or its derivatives, and its general structural formula is as follows:

[0006]

[0007] Where R1 is CH3, CH2CH3, CH(CH3)2 or H, and R2 is OH or NH2.

[0008] Furthermore, the derivatives of dimethyl terephthalate (DMTPA) include diethyl terephthalate (DETPA), diisopropyl terephthalate (DiPTPA), monomethyl terephthalate (MMTPA), dimethyl 2,6-naphthalenedicarboxylate, methyl 4-(aminocarbonyl)benzoate, and other para- or similar para-substituted diaromatic esters.

[0009] The present invention also provides a method for preparing a photoluminescent color-changing material, wherein the material is grown into single crystals by cooling its hot saturated solution, or crystals are obtained by slowly evaporating its dimethyl sulfoxide solution.

[0010] Furthermore, the derivatives of dimethyl terephthalate (DMTPA) are dimethyl terephthalate (DMTPA), diethyl terephthalate (DETPA), or diisopropyl terephthalate (DiPTPA), synthesized by reacting terephthaloyl chloride with the corresponding monohydric alcohol, as shown in the following reaction formula:

[0011]

[0012] Wherein, R3 = CH3, CH2CH3 or CH(CH3)2.

[0013] Specifically, at room temperature, triethylamine, dichloromethane, and the corresponding monohydric alcohol were added to the reactor, respectively. Terephthaloyl chloride was dissolved in dichloromethane and added dropwise to the reactor under nitrogen protection in an ice-water bath. After the system returned to room temperature, the reaction was monitored using thin-layer chromatography. Once the reaction was complete, pure water was added to quench the reaction. The organic phase was collected after washing several times with saturated brine, dried overnight with anhydrous magnesium sulfate, filtered, washed, and rotary evaporated to obtain the crude product. The crude product was then separated and purified using column chromatography, dried under vacuum, and the corresponding diaromatic ester was obtained. The corresponding single crystals were obtained by cooling the hot saturated solution.

[0014] Furthermore, the photoluminescent color-changing material is commercially available monomethyl terephthalate (MMTPA), dimethyl 2,6-naphthalenedicarboxylate, or methyl 4-(aminocarbonyl)benzoate, which is grown into single crystals by cooling its hot saturated solution.

[0015] Furthermore, the terephthalic acid (TPA) crystals are obtained by slowly evaporating a dimethyl sulfoxide solution of commercially available TPA.

[0016] Specifically, terephthalic acid (TPA), monomethyl terephthalate (MMTPA), dimethyl 2,6-naphthalenedicarboxylate, and methyl 4-(aminocarbonyl)benzoate are commercially available and require purification by column chromatography or multiple recrystallizations. MMTPA and dimethyl 2,6-naphthalenedicarboxylate are purified by column chromatography, TPA by reversed-phase column chromatography, and methyl 4-(aminocarbonyl)benzoate by multiple recrystallizations. Except for terephthalic acid, all are purified by cooling the purified product and then heating the resulting saturated solution to obtain their corresponding single crystals. Powdered terephthalic acid crystals are obtained by slowly evaporating its dimethyl sulfoxide solution.

[0017] Furthermore, the crystals of terephthalic acid or dimethyl terephthalate or their derivatives are used as photoluminescent color-changing materials.

[0018] Furthermore, the photoluminescent color-changing behavior of the crystals of terephthalic acid or dimethyl terephthalate or their derivatives is reversible.

[0019] Furthermore, the crystals of terephthalic acid or dimethyl terephthalate or their derivatives are prepared into anti-counterfeiting ink for screen printing. Specifically, terephthalic acid and dimethyl terephthalate and their derivatives are dissolved in ethyl acetate to prepare a concentrated solution with a mass concentration of 5-10 mg / mL, which is then uniformly mixed with commercially available aloe vera gel (volume ratio: 5:1 to 10:1) and combined with screen printing for anti-counterfeiting patterns and text on soft and hard substrates.

[0020] Furthermore, the crystals of terephthalic acid or dimethyl terephthalate or their derivatives are combined with a hydrogel to prepare a flexible material suitable for information storage. Specifically, acrylamide and N,N'-methylenebisacrylamide are dissolved in pure water. Crystals of terephthalic acid or dimethyl terephthalate or their derivatives are ground into fine, fluffy crystals and added to the solution. Finally, ammonium persulfate is added as an initiator. The mass ratio of acrylamide to dimethyl terephthalate is 80:1, and only trace amounts of N,N'-methylenebisacrylamide and ammonium persulfate are required, with a mass ratio of approximately 1:500 to acrylamide. The mixture is stirred at room temperature until the crystals are uniformly dispersed in the system. The mixture is poured into a mold and heated at 50-70°C until the system solidifies to obtain the target hydrogel, which is then prepared as a rewritable flexible material for information storage and erasure.

[0021] The prepared crystals of terephthalic acid or dimethyl terephthalate or their derivatives exhibit photoluminescent color-changing properties, with their photoluminescence altering under external light stimulation. This photoluminescent color-changing phenomenon can be recovered by heating or grinding the material, and it can be reused after cooling to room temperature or fumigating with a solvent. This material can be used to prepare anti-counterfeiting inks, or it can be added to hydrogels to prepare flexible rewritable materials.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention relates to terephthalic acid, dimethyl terephthalate, or their derivatives, which are pure organic luminescent materials that exhibit photoluminescence color change without relying on photochemical reactions. They possess a simple structure and are easy to synthesize. The intrinsic luminescence of dimethyl terephthalate changes from deep blue to violet light, and further to orange-red light, exhibiting a wide color change range under external light stimulation. In the aggregated state, moderately strong electronic interactions exist between molecules, allowing for minute displacements and rearrangements under external light stimulation while maintaining a regular molecular arrangement. These periodically widespread electronic interactions amplify these minute rearrangements, thereby altering the intrinsic emission of the aggregates and ultimately achieving the photoluminescence color change phenomenon. By replacing different functional groups, the color change range and response time of the material can be adjusted to meet the flexible needs of different scenarios. The photoluminescence color change phenomenon of this material is reversible after heating or grinding, proving its reusability. Terephthalic acid or dimethyl terephthalate or its derivatives can be combined with other matrices to prepare anti-counterfeiting inks for screen printing on both hard and soft substrates; they can also be used as photosensitizers to dope hydrogels and develop flexible information storage materials. Attached Figure Description

[0024] Figure 1The seven compounds are DMTPA, DETPA, DiPTPA, MMTPA, TPA, dimethyl 2,6-naphthalenedicarboxylate, and methyl 4-(aminocarbonyl)benzoate. 1 H NMR spectrum.

[0025] Figure 2 The seven compounds are DMTPA, DETPA, DiPTPA, MMTPA, TPA, dimethyl 2,6-naphthalenedicarboxylate, and methyl 4-(aminocarbonyl)benzoate. 13 C10 NMR spectrum.

[0026] Figure 3 The UV-Vis absorption spectra of DMTPA crystals before and after irradiation with 312nm UV light for different times are shown.

[0027] Figure 4 The images show the luminescence and emission spectra of the DMTPA crystal before and after irradiation with 312nm ultraviolet light for different times, with an excitation wavelength of 312nm.

[0028] Figure 5 The images show the luminescence and emission spectra of DETPA, DiPTPA, and dimethyl 2,6-naphthalenedicarboxylate crystals before and after irradiation with 312 nm ultraviolet light for different times. The excitation wavelength was 312 nm.

[0029] Figure 6 The images show the luminescence and emission spectra of MMTPA and TPA crystals before and after irradiation with 312nm ultraviolet light for different times, with an excitation wavelength of 312nm.

[0030] Figure 7 Phosphorescence emission spectra (delay = 1 ms) and lifetime diagrams of MMTPA and TPA crystals before and after irradiation with 312 nm ultraviolet light for different times are shown.

[0031] Figure 8 Photographs, emission spectra, and color coordinate diagrams of methyl 4-(aminocarbonyl)benzoate crystals before and after irradiation with 312 nm ultraviolet light for different times are shown. The excitation wavelength is 312 nm.

[0032] Figure 9 To prepare anti-counterfeiting ink for DMTPA and use it for screen printing of luminescent photographic patterns.

[0033] Figure 10 Luminescent photograph of DMTPA-doped hydrogel for use in rewritable flexible information storage materials. Detailed Implementation

[0034] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0035] In the examples below, dimethyl terephthalate (DMTPA), diethyl terephthalate (DETPA), and diisopropyl terephthalate (DiPTPA) were obtained by reacting terephthaloyl chloride with methanol, ethanol, or isopropanol at room temperature, and the corresponding crystals were obtained by cooling their hot saturated solutions after column chromatography purification. Monomethyl terephthalate (MMTPA), terephthalic acid (TPA), dimethyl 2,6-naphthalenedicarboxylate, and methyl 4-(aminocarbonyl)benzoate are commercially available products. Monomethyl terephthalate (MMTPA) and dimethyl 2,6-naphthalenedicarboxylate were purified by column chromatography, terephthalic acid (TPA) was purified by reversed-phase column chromatography, and methyl 4-(aminocarbonyl)benzoate was purified by multiple recrystallizations. Except for terephthalic acid, their crystals were obtained by cooling a hot saturated solution, while the powdered crystals of terephthalic acid (TPA) were obtained by slowly evaporating its dimethyl sulfoxide solution.

[0036] The purpose of column chromatography or multiple crystallization purification is to eliminate the influence of impurities that may be present in the material itself on luminescence.

[0037] Example 1:

[0038] Crystalline DMTPA was prepared by the following method:

[0039] 1.7 mL of triethylamine, 0.49 mL of methanol, and 10 mL of dichloromethane were placed in a 50 mL round-bottom flask and cooled to 0 °C in an ice-water bath. 2.03 g of terephthaloyl chloride was dissolved in 5 mL of dichloromethane and added dropwise to the flask. After the addition was complete, the mixture was allowed to return to room temperature and reacted for 2 hours. After the reaction was complete, 10 mL of pure water was added to quench the reaction. The organic phase was separated, washed three times with saturated brine, and dried overnight with anhydrous magnesium sulfate. The mixture was filtered, the filter cake was washed, and the filtrate was rotary evaporated to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: n-hexane / ethyl acetate). The product was dried overnight in a vacuum oven at 40 °C to obtain 1.82 g of white solid powder, with a yield of 93.8%. Finally, colorless needle-like crystals of DMTPA were obtained by cooling its hot saturated ethyl acetate solution.

[0040] 1 H NMR (500MHz, CDCl3) δ8.10 (s, 4H), 3.94 (s, 6H). For example Figure 1 ;

[0041] 13 C NMR (126MHz, DMSO-d6) δ 166.42, 134.04, 129.69, 52.57. (e.g.) Figure 2 .

[0042] Crystalline DMTPA exhibits photoluminescence color change at room temperature, and the external light wavelengths that can drive its photoluminescence color change include, but are not limited to, 254, 312, and 330 nm.

[0043] Figure 3 The figures show the UV-Vis absorption spectra of crystalline DMTPA before and after irradiation with 312nm UV light for different durations. As can be seen from the figures, the intensity of the absorption peak at 350nm increases after exposure to external light, and this increase intensities increases with the duration of irradiation, corresponding to enhanced intermolecular electronic interactions. No new peaks appear in the visible light region, indicating that its appearance color remains unchanged before and after photoluminescence color change.

[0044] Figure 4 The images show the intrinsic luminescence and emission spectra of crystalline DMTPA after excitation with 312nm ultraviolet light for different times. As can be seen from the figures, with increasing excitation time, the blue emission peak at 420nm gradually decreases, while the orange-red emission peaks at 595, 650, and 725nm significantly increase, resulting in a wide color gamut emission color change phenomenon in crystalline DMTPA, transitioning from deep blue to violet and then to orange-red.

[0045] Example 2:

[0046] Crystalline DETPA was prepared by the following method:

[0047] 1.7 mL of triethylamine, 0.70 mL of ethanol, and 10 mL of dichloromethane were placed in a 50 mL round-bottom flask and cooled to 0 °C in an ice-water bath. 2.03 g of terephthaloyl chloride was dissolved in 5 mL of dichloromethane and added dropwise to the flask. After the addition was complete, the mixture was allowed to return to room temperature and reacted for 2 hours. After the reaction was complete, 10 mL of pure water was added to quench the reaction. The organic phase was separated, washed three times with saturated brine, and dried overnight with anhydrous magnesium sulfate. The mixture was filtered, the filter cake was washed, and the filtrate was rotary evaporated to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: n-hexane / ethyl acetate). The product was dried overnight in a vacuum oven at 40 °C to obtain 2.06 g of white solid powder, with a yield of 92.7%. Finally, colorless needle-like crystals of DETPA were obtained by cooling its hot saturated ethyl acetate solution.

[0048] 1H NMR (500MHz, CDCl3) δ8.10 (s, 4H), 4.40 (q, J = 7.1Hz, 4H), 1.41 (t, J = 7.1Hz, 6H). For example Figure 1 ;

[0049] 13 C NMR (126MHz, DMSO-d6) δ 165.98, 134.30, 129.59, 61.53, 14.41. (e.g.) Figure 2 .

[0050] Example 3:

[0051] Crystalline DiPTPA is prepared as follows:

[0052] 1.7 mL of triethylamine, 0.92 mL of isopropanol, and 10 mL of dichloromethane were placed in a 50 mL round-bottom flask and cooled to 0 °C in an ice-water bath. 2.03 g of terephthaloyl chloride was dissolved in 5 mL of dichloromethane and added dropwise to the flask. After the addition was complete, the mixture was allowed to return to room temperature and reacted for 2 hours. After the reaction was complete, 10 mL of pure water was added to quench the reaction. The organic phase was separated, washed three times with saturated brine, and dried overnight with anhydrous magnesium sulfate. The mixture was filtered, the filter cake was washed, and the filtrate was rotary evaporated to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: n-hexane / ethyl acetate). The product was dried overnight in a vacuum oven at 40 °C to obtain 2.38 g of white solid powder, with a yield of 95.2%. Finally, colorless needle-like crystals of DiPTPA were obtained by cooling its hot saturated ethyl acetate solution.

[0053] 1 H NMR (500MHz, CDCl3) δ8.05 (s, 4H), 5.16 (sep, J = 6.2Hz, 2H), 1.33 (d, J = 6.3Hz, 12H). For example Figure 1 ;

[0054] 13 C NMR (126MHz, DMSO-d6) δ 164.48, 133.98, 129.31, 68.77, 21.56. (e.g.) Figure 2 .

[0055] Example 4:

[0056] Commercially available dimethyl 2,6-naphthalenedicarboxylate was purified by silica gel column chromatography (eluent: n-hexane / ethyl acetate), and the product was dried overnight in a vacuum oven at 40°C. Colorless flaky crystals of dimethyl 2,6-naphthalenedicarboxylate were obtained by cooling its hot saturated ethyl acetate solution.

[0057] 1H NMR (500MHz, CDCl3) δ8.63 (s, 2H), 8.12 (d, J = 8.5Hz, 2H), 8.00 (d, J = 8.6Hz, 2H), 4.00 (s, J = 1.2Hz, 6H). For example Figure 1 ;

[0058] 13 C NMR (126MHz, DMSO-d6) δ 167.00, 134.73, 130.80, 129.73, 129.66, 126.16, 52.58. (e.g.) Figure 2 .

[0059] The crystalline DETPA, DiPTPA and dimethyl 2,6-naphthalenedicarboxylate prepared in Examples 2-4 exhibit photoluminescence color change at room temperature. The external light wavelengths that can drive their photoluminescence color change include, but are not limited to, 254, 312 and 330 nm.

[0060] Figure 5 The intrinsic luminescence images and spectra of crystalline DETPA, DiPTPA, and dimethyl 2,6-naphthalenedicarboxylate (DMTPA) after excitation with 312 nm UV light for different durations are shown. The three compounds exhibit different photoluminescent color-changing characteristics. The emission spectrum of DETPA in the figure shows that under 312 nm UV stimulation, the blue emission peak at 440 nm of crystalline DETPA decreases, while the orange-red emission peaks at 605, 665, and 730 nm significantly increase. The corresponding luminescence images show that as the stimulation time increases from 0 to 10 min, the emission color of crystalline DETPA gradually changes from deep blue to purple, and this color-changing range is narrower than that of crystalline DMTPA. Unlike crystalline DMTPA, because the emission in the blue region at 440 nm of crystalline DETPA still accounts for a considerable proportion after the photoluminescence color change, crystalline DETPA exhibits purple luminescence after the color change. Crystalline DiPTPA, under 312 nm UV stimulation, only showed a decrease in the blue emission peak at 420 nm, without the appearance of a new peak in the orange-red region, corresponding to a photoluminescence transition from sky blue to deep blue. Luminescence images showed that as the stimulation time increased from 0 to 10 min, the intrinsic luminescence of crystalline DiPTPA gradually weakened, without a redshift. This is because the isopropyl group in crystalline DiPTPA has significant steric hindrance and lacks effective spatial electron delocalization, thus hindering the generation of new aggregates in response to external light stimulation. Under 312 nm UV stimulation, crystalline dimethyl 2,6-naphthalenedicarboxylate also exhibited a photoluminescence color change from deep purple to purplish-red, but the stimulation response time was significantly prolonged (see [link to relevant documentation]). Figure 5Even after 20 minutes of stimulation with 312 nm ultraviolet light, the luminescence color change of crystalline 2,6-naphthalenedicarboxylate (DMTPA), DETPA, and DiPTPA remained relatively insignificant, and the color change range was significantly narrower compared to DMTPA, DETPA, and DiPTPA. The intensity of the new peak appearing in the long-wavelength region was also weaker. This is because the π-π interactions between molecules in crystalline 2,6-naphthalenedicarboxylate are too strong, weakening the molecules' ability to rearrange in response to external light stimulation, thus resulting in a narrower luminescence color change range and a longer response time.

[0061] Therefore, the photoluminescent color-changing properties of dimethyl terephthalate derivatives can be adjusted by replacing the substituent groups.

[0062] Example 5:

[0063] Commercially available MMTPA was purified by silica gel column chromatography (eluent: dichloromethane / ethyl acetate), and the product was dried overnight in a vacuum oven at 40°C. Colorless needle-like MMTPA crystals were obtained by cooling its hot saturated ethyl acetate / methanol solution.

[0064] 1 H NMR (500MHz, CDCl3) δ13.34 (s, 1H), 8.05 (d, J = 2.4Hz, 4H), 3.88 (s, 3H). Such as Figure 1 ;

[0065] 13 C NMR (126MHz, DMSO-d6) δ 166.57, 165.62, 134.82, 133.17, 129.61, 129.36, 52.46. (e.g.) Figure 2 .

[0066] Example 6:

[0067] Commercially available TPA was purified by C18 reversed-phase column chromatography (eluent: water / methanol), and the product was dried overnight in a vacuum oven at 40°C. White crystalline powder TPA was obtained by slowly evaporating its dimethyl sulfoxide solution.

[0068] 1 H NMR (500MHz, CDCl3) δ13.29 (s, 2H), 8.04 (s, 4H). Such as Figure 1 ;

[0069] 13 C NMR (126MHz, DMSO-d6) δ 167.14, 134.90, 129.92. (e.g.) Figure 2 .

[0070] Example 7:

[0071] Colorless needle-like crystals were obtained by cooling a hot saturated ethyl acetate solution of commercially available methyl 4-(aminocarbonyl)benzoate. This recrystallization process was repeated multiple times to obtain purified colorless needle-like crystals of methyl 4-(aminocarbonyl)benzoate.

[0072] 1 H NMR (500MHz, CDCl3) δ8.14(s,1H),8.05–7.95(m,4H),7.56(s,1H),3.88(s,3H). Such as Figure 1 ;

[0073] 13 C NMR (126MHz, DMSO-d6) δ 167.03, 165.75, 138.44, 131.80, 129.07, 127.83, 52.37. (e.g.) Figure 2 The crystalline MMTPA, TPA, and methyl 4-(aminocarbonyl)benzoate obtained in Examples 5-7 exhibit photoluminescence color change at room temperature. The external light wavelengths that can drive their photoluminescence color change include, but are not limited to, 254, 312, and 330 nm.

[0074] Figure 6 Images and emission spectra of crystalline MMTPA and TPA after excitation with 312 nm ultraviolet light for different times are shown. Figure 7 The delayed emission spectra of crystalline MMTPA and TPA after excitation with 312 nm ultraviolet light for different times and the time-resolved spectra of the phosphorescence lifetimes of each emission peak after photoluminescence color change are shown. Figure 8 The emission spectra, photographs, and corresponding color coordinates of crystalline methyl 4-(aminocarbonyl)benzoate after excitation with 312 nm UV light for different times are shown. The three compounds exhibit different photoluminescent color-changing characteristics. From... Figure 6 As can be seen in b, under 312nm ultraviolet light stimulation, the emission peaks of crystalline MMTPA at 430 and 530nm decrease, while the orange-red emission peaks at 600, 655 and 720nm increase. Figure 6 The corresponding photoluminescence, as shown in Figure a, changes from deep blue at 0 seconds to bluish-violet at 60 seconds, and further to magenta at 600 seconds, with increasing stimulation time. Furthermore, due to the strong hydrogen bonding interactions between MMTPA molecules, the triplet excitons are effectively stabilized, resulting in a photochromic room-temperature phosphorescence phenomenon after excitation cessation, changing from cyan at 0 seconds to green at 60 seconds, and then further to yellow at 600 seconds, with increasing stimulation time. This is... Figure 7 This can be confirmed by the delayed emission spectrum of crystalline MMTPA shown in Figure a. With increasing stimulation time, the peak at 420 nm decreases significantly, while the peak at 520 nm decreases less, causing the latter to gradually become the dominant peak. Correspondingly, as shown in Figure a... Figure 7As shown in b, each emission peak of crystalline MMTPA has a long lifetime, verifying its room-temperature phosphorescence properties that are visible to the naked eye. Figure 6 The emission spectrum of crystalline TPA shown in c remains almost unchanged before and after stimulation with 312nm ultraviolet light; correspondingly, its luminescence always remains as shown in the figure. Figure 6 The deep blue color shown in Figure a is due to the excessively strong hydrogen bonds between TPA molecules, which severely hinder the molecules' ability to rearrange themselves. Even after prolonged light stimulation, only a very weak luminescence and color change can be produced; however, as shown in Figure a... Figure 6 As shown in Figure a, its yellow-green room-temperature phosphorescence is extremely prominent, and the corresponding spectrum is as follows: Figure 7 As shown in c. Figure 7 Phosphorescence lifetime tests on crystalline TPA showed that its phosphorescence lifetime was significantly longer than that of crystalline MMTPA. This is because the strong hydrogen bonding between TPA molecules strongly suppressed non-radiative transitions such as vibrational and rotational transitions, thereby promoting triplet emission and stabilizing triplet excitons, thus extending the phosphorescence lifetime. The luminescence-color-changing behavior of crystalline methyl 4-(aminocarbonyl)benzoate under 312 nm UV excitation is as follows... Figure 8 As shown, as the stimulation time is extended from 0 to 10 min and even 20 min, the emission peak at 520 nm gradually decreases, while the peaks at 593, 651 and 720 nm appear and increase, and the corresponding emission color changes from dark blue when the stimulation time is 0 min to purple when the stimulation time is 20 min.

[0075] Therefore, the photoluminescence and room temperature phosphorescence properties of dimethyl terephthalate derivatives can be comprehensively regulated by appropriately introducing intermolecular hydrogen bonds.

[0076] The products obtained in the above embodiments can be used to prepare anti-counterfeiting inks for screen printing, or they can be combined with hydrogels to prepare flexible materials that can be used for information storage. The following detailed application examples illustrate this:

[0077] Application Example 1:

[0078] Application of anti-counterfeiting ink.

[0079] The products obtained in the above embodiments can be used to prepare anti-counterfeiting inks. Taking the DMTPA obtained in Example 1 as an example, it is dissolved in ethyl acetate to prepare a concentrated solution with a mass concentration of 10 mg / mL, and then mixed evenly with commercially available aloe vera gel (volume ratio: 10:1). This solution can be combined with screen printing for anti-counterfeiting patterns and text on soft and hard substrates.

[0080] Figure 9The pattern shown is obtained by screen printing on commercially available filter paper, with the aforementioned anti-counterfeiting ink used on the right half of the pattern. Under natural light, the pattern on the filter paper is almost invisible; under 312nm ultraviolet light excitation, it exhibits a butterfly-like luminescent pattern. With prolonged exposure to light, the left half maintains its blue luminescence, while the right half displays a color-changing luminescence that transitions from blue to purple and then to red. These phenomena can be used as a basis for anti-counterfeiting applications.

[0081] Application Example 2:

[0082] Applications of flexible, rewritable hydrogels for information storage.

[0083] The products obtained in the above embodiments can be incorporated into hydrogels to prepare rewritable flexible materials for information storage and erasure. Taking the DMTPA obtained in Example 1 as an example, the preparation process is as follows:

[0084] Dissolve 2.4 g of acrylamide and 4 mg of N,N'-methylenebisacrylamide in 6 mL of pure water. Grind 30 mg of DMTPA crystals into fine, fluffy crystals and add them to the solution. Finally, add 8 mg of ammonium persulfate as an initiator. Stir at room temperature for 10 min to uniformly disperse the DMTPA crystals. Pour the mixture into a circular mold and heat at 60 °C for 20 min to obtain the target hydrogel.

[0085] Figure 10 a is a schematic diagram illustrating the writing, erasing, and recycling of information into the hydrogel. Figure 10 Photograph b shows an example of the hydrogel's application in information storage and erasure. A mask is placed over it, and after 5 minutes of light stimulation, the desired information can be written using the photoluminescence color-changing phenomenon of DMTPA. Removing the mask allows the information to be read under 312nm ultraviolet light excitation. Continued light stimulation causes the hydrogel to glow entirely red, allowing the original information to be erased. Sealing the hydrogel and heating it at 80°C for 10 minutes restores its blue glow, allowing for reuse. The hydrogel's appearance remains unchanged throughout the writing, erasing, and recycling processes. Combined with its flexibility and self-adhesive properties, this information storage hydrogel is adaptable to various scenarios and has broad application prospects.

[0086] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An application of a photoluminescent color-changing material, characterized in that, Crystals of terephthalic acid or dimethyl terephthalate or their derivatives are used as photoluminescent color-changing materials, wherein the crystals of terephthalic acid or dimethyl terephthalate or their derivatives have the following general structural formula: Where R1 is CH3, CH2CH3, CH(CH3)2 or H, and R2 is OH or NH2.

2. The application of the photoluminescent color-changing material according to claim 1, characterized in that, The derivatives of dimethyl terephthalate (DMTPA) include diethyl terephthalate (DETPA), diisopropyl terephthalate (DiPTPA), monomethyl terephthalate (MMTPA), dimethyl 2,6-naphthalenedicarboxylate, or methyl 4-(aminocarbonyl)benzoate.

3. The application of the photoluminescent color-changing material according to claim 1, characterized in that, The material is grown into single crystals by cooling its hot saturated solution, or crystals are obtained by slowly evaporating its dimethyl sulfoxide solution.

4. The application of the photoluminescent color-changing material according to claim 3, characterized in that, The material described is dimethyl terephthalate (DMTPA), diethyl terephthalate (DETPA), or diisopropyl terephthalate (DiPTPA), synthesized by reacting terephthaloyl chloride with the corresponding monohydric alcohol, as shown in the following reaction formula: Wherein, R3 = CH3, CH2CH3 or CH(CH3)2.

5. The application of the photoluminescent color-changing material according to claim 3, characterized in that, The material described is commercially available monomethyl terephthalate (MMTPA), dimethyl 2,6-naphthalenedicarboxylate, or methyl 4-(aminocarbonyl)benzoate, which are grown into single crystals by cooling their hot saturated solutions.

6. The application of the photoluminescent color-changing material according to claim 3, characterized in that, The material is terephthalic acid (TPA), whose crystals are obtained by slowly evaporating its dimethyl sulfoxide solution.

7. The application of the photoluminescent color-changing material according to claim 6, characterized in that, The photoluminescent color-changing behavior of the crystals of terephthalic acid or dimethyl terephthalate or their derivatives is reversible.

8. The application of the photoluminescent color-changing material according to claim 7, characterized in that, The crystals of terephthalic acid or dimethyl terephthalate or their derivatives are used to prepare anti-counterfeiting ink for screen printing.

9. The application of the photoluminescent color-changing material according to claim 7, characterized in that, The crystals of terephthalic acid or dimethyl terephthalate or their derivatives are combined with hydrogels to prepare a flexible material that can be used for information storage.

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