Dynamic thermochromic luminescent material and method

Abstract

The present invention discloses a dynamic thermochromic luminescent material and method. The dynamic thermochromic luminescent material is obtained by inducing coordination interaction between a cholesterol derivative dispersed in an organic solvent and ZnCl2. The method comprises: dispersing the cholesterol derivative in the organic solvent, ultrasonically treating the mixture to obtain a clear and transparent solution, adding ZnCl2 in an amount of 0.1-1.5 molar equivalents of the cholesterol derivative to the solution, and ultrasonically cleaning the solution in an ultrasonic cleaner to obtain a series of dynamic thermochromic luminescent materials H1 with cyan-green fluorescence; taking the dynamic thermochromic luminescent material H1 and subjecting it to the following heat treatment: constant-temperature heating at 50-80°C for about 15-25s, and then immediately placing the solution in an ultrasonic cleaner filled with ice water and ultrasonicating the solution to obtain a dynamic thermochromic luminescent material H2 with blue fluorescence. In summary, the present invention provides a switchable luminescent material responsive to temperature stimulation. The material and method of the present invention can be applied to information encryption.

Description

Technical Field

[0001] The present invention relates to the field of material technology, in particular to a dynamic thermochromic luminescent material and method. Background Art

[0002] With the rapid development of the information age, information security has become increasingly crucial. Protecting information more securely is becoming a crucial issue in modern society. Furthermore, secure information storage is crucial to my country's national security and livelihoods. Photoluminescent soft materials have been widely used in sensors, displays, and organic light-emitting diodes (OLEDs), and have garnered significant attention in security applications such as information storage, data recording, and encryption. However, the information directly recorded in these materials is typically visible under ambient light or ultraviolet light, and these security labels are easily mimicked, hindering their practical application in protecting confidential information. Consequently, stimuli-responsive luminescent materials—intelligent luminescent materials that can sense and respond to ambient stimuli—have emerged. Stimuli-responsive luminescent materials are emerging as smart materials that have recently attracted increasing attention in the fields of sensing and imaging due to their tunable optical, physicochemical, and structural properties, as well as their ability to respond to specific stimuli. In response to external stimuli, such as light, temperature, pH, and redox reactions, these luminescent switchable materials undergo structural and excited-state changes, resulting in significant macroscopic changes in color and / or luminescence. These color and / or luminescence variations can be exploited to achieve secure information storage. Stimuli-responsive luminescent materials that rely on the continuous addition of chemicals have long been developed for information encryption and decryption. However, because these methods require invasive stimulation, consumers without professional chemical knowledge may find it difficult to process the encoded information by adding chemicals. Therefore, there is a great need to develop alternative switchable luminescent materials with confidential encryption properties that can be easily operated in a non-invasive manner, where the security code is initially invisible and becomes visible under specific external stimuli. In this way, reversible information encryption and decryption can be achieved. Temperature is an attractive external stimulus because it provides simple, non-invasive, high-precision control of the operation. In addition, many stimuli-responsive luminescent materials have defects such as the inability to erase information or high cost when used for information encryption, and they are not reusable, which also limits their wider application. Therefore, the invention of a new type of information encryption material that is simple, low-cost, automatically erasable and recyclable has considerable practical significance and application prospects. Summary of the Invention

[0003] In response to the above problems, the present invention provides a dynamic thermochromic luminescent material and method, including a switchable luminescent material that responds to temperature stimulation. The material and method of the present invention can be applied to information encryption.

[0004] To achieve this object, the present invention provides the following technical solutions:

[0005] The first aspect of the present invention provides a dynamic thermochromic luminescent material, which is obtained by inducing coordination interaction between a cholesterol derivative dispersed in an organic solvent and ZnCl2.

[0006] Preferably, the cholesterol derivative has the structural formula of Formula I:

[0007]

[0008] Preferably, the organic solvent comprises p-xylene and ethanol. Further preferably, the volume ratio of xylene to ethanol is about 8:2 to 2:8; further preferably, the volume ratio of xylene to ethanol is 1:1.

[0009] Preferably, the molar concentration of the cholesterol derivative is 2 to 30 mM. More preferably, the molar concentration of the cholesterol derivative is 16.37 mM.

[0010] Preferably, the molar equivalent of ZnCl2 is 0.1 to 1.5 equivalents.

[0011] The second aspect of the present invention provides a method for producing a dynamic thermochromic luminescent material, comprising the following steps:

[0012] A cholesterol derivative is dispersed in an organic solvent, and the mixture is sonicated to obtain a clear and transparent solution. 0.1-1.5 molar equivalents of ZnCl2 of the cholesterol derivative of formula I are added thereto, and the mixture is sonicated uniformly in an ultrasonic cleaner to obtain a series of cyan-green fluorescent dynamic thermochromic luminescent materials H1.

[0013] Take the dynamic thermochromic luminescent material H1 and perform the following heat treatment on it: heat it at a constant temperature of 50-80°C for about 15-25s and then immediately place it in an ultrasonic cleaner filled with ice water for ultrasonication to obtain the blue fluorescent dynamic thermochromic luminescent material H2.

[0014] Preferably, material H2 can be reversibly converted into material H1 after standing for 30 minutes to 1 hour.

[0015] Preferably, the cholesterol derivative has the structural formula of Formula I:

[0016]

[0017] Preferably, the synthesis route of the cholesterol derivatives is:

[0018]

[0019] Preferably, the treatment is performed by constant temperature heating at 70° C. for 20 seconds.

[0020] A third aspect of the present invention provides a method for repeated decryption and encryption, comprising the following steps:

[0021] S1. Take the material H1 sample described in the present invention and write encrypted information on a blank high-temperature and corrosion-resistant orifice plate;

[0022] S2. Heat the plate encrypted in step S1 at a constant temperature of 50-80°C for 15-25 seconds, and then immediately place it in an ultrasonic cleaner filled with ice water to perform ultrasonic cleaning to decrypt the information.

[0023] S3, placing the plate under 365nm ultraviolet light to read the encrypted information;

[0024] S4, the well plate after decryption in step S3 is allowed to stand at room temperature for 30 min-1 h, and then placed under a 365 nm ultraviolet lamp again, and the decrypted information is encrypted again, that is, the H2 of the present invention can be reversibly restored to the material H1 of the present invention;

[0025] S5. Repeat the above steps.

[0026] Compared with the prior art, the beneficial effects and significant improvements of the technical solution of the present invention are:

[0027] 1. The present invention utilizes cholesterol derivatives and ZnCl2 to induce chiral transfer of cholesterol zinc complexes through simple coordination interactions, thereby obtaining a supramolecular assembly system stimuli-responsive material with thermoluminescent switching;

[0028] 2. Based on the two different luminescence characteristics exhibited by the circularly polarized luminescent material obtained by adding different equivalents of ZnCl2 when subjected to heat treatment operations, a dynamic and recyclable information encryption-decryption technology can be realized based on this. At the same time, this information encryption technology can be spontaneously erased in a relatively short period of time when information is erased, which has certain application prospects in multi-level information encryption and anti-counterfeiting.

[0029] 3. The materials involved in this technology have the advantages of high sensitivity, higher safety, stability, low cost, visualization, easy operation and recyclability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the embodiments of the present invention.

[0031] Figure 1 This is a macroscopic photograph of the assembly formed by the pyridine-imine functionalized cholesterol derivative and ZnCl2 according to Example 2 of the present invention;

[0032] Figure 2 This is a scanning electron microscope image of material H1 of Example 2 of the present invention;

[0033] Figure 3 This is a scanning electron microscope image of H2 in Example 3 of the present invention;

[0034] Figure 4 This is a circularly polarized luminescence spectrum diagram of H1 in Example 2 of the present invention;

[0035] Figure 5 This is a circularly polarized luminescence spectrum of H2 in Example 3 of the present invention;

[0036] Figure 6 The fluorescence spectra of H1 and H2 in embodiments 2 and 3 of the present invention are shown;

[0037] Figure 7 This is an example of using the material H1 of Example 4 of the present invention as the only starting material in information encryption-decryption and self-erasure. DETAILED DESCRIPTION

[0038] Example 1 Preparation of Cholesterol Derivative Ligand of Formula I

[0039] The synthetic route of formula I is as follows:

[0040]

[0041] The specific synthesis steps of formula I are:

[0042] 1.1. Prepare 4-[(2-pyridylmethylene)amino]phenol by referring to the method described in Zhang, Q. et al., Recyclable palladium(II)imino-pyridine complex immobilized on mesoporous silica as a highly active and recoverable catalyst for Suzuki–Miyaura coupling reactions in aqueous medium, Tetrahedron 2013, 69(2), 447-454;

[0043] 1.2. 4-[(2-Pyridylmethylene)amino]phenol (1 g, 5.04 mmol) was dissolved in 20 ml of a mixed solvent of dry dichloromethane and triethylamine (0.6 ml). The mixture was added dropwise into 80 ml of dichloromethane solution containing triethylamine (0.72 mL, 5.2 mmol) and cholesterol carbonyl chloride (3.0 g, 6.7 mmol). The mixture was stirred at 0°C for about 10 minutes.

[0044] 1.3. Transfer the mixture to room temperature and continue stirring for 3 hours, then remove the solvent by rotary evaporation. Purify the crude product by flash silica gel column chromatography (ethyl acetate / dichloromethane, V / V, 1 / 10) to obtain Formula I in a yield of 85%.

[0045] The structural characterization data of Formula I are as follows:

[0046] 1 H NMR (300MHz, CDCl3) δ8.74(d,J=4.3Hz,1H),8.62(s,1H),8.22(d,J=7.9Hz,1H),7.84(td,J=7.8 ,1.6Hz,1H),7.40(ddd,J=7.4,4.8,1.1Hz,1H),7.36-7.30(m,2H),7.28-7.23(m,2H),5.45(d,J= 4.8Hz,1H),4.71-4.52(m,1H),2.59-2.42(m,2H),2.12-1.69(m,6H),1.63-1.48(m,7H),1.40-1 .09(m,10H),1.09-0.99(m,6H),0.94(d,J=6.5Hz,3H),0.89(dd,J=6.6,1.1Hz,6H),0.71(s,3H).

[0047] 13C NMR (150MHz, CDCl3) δ160.95,154.62,153.17,150.03,149.95,148.75,139. 31,136.89,125.42,123.42,122.29,122.16,122.04,79.17,56.87,56.31,50 .16,42.50,39.89,39.70,38.13,37.02,36.74,36.37,35.98,32.10,32.02,28.42,28.21,27.83,24.47,24.02,23.03,22.77,21.24,19.48,18.91,12.06.

[0048] HRMS(MALDI-TOF):m / z calcd.for C40H54N2O3[M] + :611.4213,found:611.1422.

[0049] Example 2 Supramolecular material H1 formed by assembling cholesterol derivative ligand Ⅰ with ZnCl2

[0050] In a clean sample vial, 3 mg (16.37 mmol) of the organic small molecule represented by Formula I was weighed. 150 μL of p-xylene and ethanol solvents were pipetted into the sample vial to completely dissolve the mixture. A high-concentration mother solution of ZnCl2 in methanol was prepared and completely dissolved in the methanol by sonication. The amount of ZnCl2 mother solution required to add different molar equivalents of ZnCl2 was calculated. The corresponding volume of ZnCl2 mother solution was pipetted into the sample vial containing 3 mg of the organic small molecule represented by Formula I to prepare an assembly of 0.1-1.5 equivalents of the corresponding cholesteryl zinc complex, which is the dynamic thermochromic luminescent material H1.

[0051] H1 exhibits cyan fluorescence emission, and its macroscopic photograph, scanning electron microscope image, circularly polarized luminescence spectrum and fluorescence spectrum are shown in Figure 1 , 2, 4, 6. Figure 1 It was observed that H1 was white and viscous in macroscopic view, and its microscopic appearance was as follows Figure 2 The spiral ribbon with left-handedness is shown in the figure. H1 shows cyan emission. Its emission fluorescence spectrum is shown in the figure below. Figure 6 As shown, the precise emission position is located near 478nm. Figure 4 The circularly polarized luminescence spectrum shown shows the excited-state supramolecular chirality of material H1, and the emission position is similar to the results of the fluorescence spectrometer.

[0052] Example 3 Dynamic thermochromic luminescent material H2 formed by assembling dynamic thermochromic luminescent material H1

[0053] The dynamic thermochromic luminescent material H1 prepared in Example 2 was subjected to the following heat treatment process: the sample bottle was heated at 70°C for 15-20 seconds, then immediately placed in an ultrasonic cleaner filled with ice water and sonicated for approximately 30 seconds. This yielded the blue fluorescent dynamic thermochromic luminescent material H2. After standing for 1 hour, material H2 reversibly returned to H1. The ultrasonic cleaner power was 150W.

[0054] The scanning electron microscope image, circularly polarized luminescence spectrum and fluorescence spectrum of material H2 are as follows: Figure 3 、 5 , 6. Figure 1 It was observed that H2 was light yellow and viscous in macroscopic form, and its microscopic appearance was as follows: Figure 3 The main morphology shown is micron sphere, H2 shows blue emission, and its emission fluorescence spectrum is as follows Figure 6 As shown, the precise emission position is located near 458nm. Figure 5 The circularly polarized luminescence spectrum shown shows the excited state supramolecular chirality of the material H2, and the emission position is similar to the results of the fluorescence spectrometer.

[0055] Example 4: Supramolecular Materials in Information Encryption Experiments

[0056] Combined with attachment Figure 7 , explaining the actual operation process of supramolecular materials formed by the assembly of cholesterol derivative ligands and ZnCl2 in information encryption. The specific steps are as follows:

[0057] 4.1. Two inks are used, respectively, of a dynamic thermochromic luminescent material H1 obtained by adding less than 0.5 molar equivalents of ZnCl2 and a dynamic thermochromic luminescent material H1 obtained by adding more than 0.7 molar equivalents of ZnCl2. In this example, the two inks are 0.3 molar equivalents and 0.8 molar equivalents of material H1.

[0058] 4.2. Prepare a blank high-temperature-resistant and corrosion-resistant well plate with a sealing lid. The information array is 5×8. Use a pipette to extract 0.8 molar equivalents of material H1 sample and write the encrypted information: 963 in the blank high-temperature-resistant and corrosion-resistant well plate for information encryption. Add 20 μL of sample evenly to each well. Fill the blank wells in the array except for the encrypted information with 0.3 molar equivalents of material H1. The added amount remains consistent. Then seal the well plate.

[0059] 4.3. Heat the sealed plate at 70°C for 15-20 seconds and then immediately place it in an ultrasonic cleaner filled with ice water for about 20 seconds to decrypt the information. Then, read the encrypted information by placing the plate under a 365nm ultraviolet lamp. The information emitted by the blue light is visible: Figure 7 As shown, 963 is the encrypted information read;

[0060] 4.4 After the decryption process described in step 3, the plate is left at room temperature for about 1 hour. Then, when it is placed under a 365nm ultraviolet lamp again, the decrypted information will be encrypted again. That is, the blue fluorescent material H2 can be reversibly restored to the cyan-green material H1. Figure 7 As shown, the encrypted information 963 is not visible under the 365nm ultraviolet light at this time, and the heat treatment process described in step 3 can be implemented again to perform multiple repeated decryption-encryption processes.

[0061] The applicant declares that, in the description of the above specification:

[0062] The descriptions of terms such as "this embodiment", "an embodiment of the present invention", "as shown in...", "further", "a further improved technical sub-scheme", etc., mean that the specific features, structures, materials or characteristics described in the embodiment or example are included in at least one embodiment or example of the present invention; in this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials or characteristics described may be combined or combined in an appropriate manner in any one or more embodiments or examples; in addition, a person of ordinary skill in the art may combine or combine different embodiments or examples and features of different embodiments or examples described in this specification without causing any contradiction.

[0063] Finally, it should be noted that:

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same.

[0065] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. Non-essential improvements, adjustments or replacements made by those skilled in the art based on the contents of this specification are all within the scope of protection required by the present invention.

Claims

1. A dynamic thermochromic luminescent material, characterized in that: The dynamic thermochromic luminescent material is prepared by the following method: A cholesterol derivative is dispersed in an organic solvent, and the mixture is sonicated to obtain a clear and transparent solution. 0.1-1.5 molar equivalents of ZnCl2 of the cholesterol derivative of formula I are added thereto, and the mixture is sonicated uniformly in an ultrasonic cleaner to obtain a series of cyan-green fluorescent dynamic thermochromic luminescent materials H1. Take the dynamic thermochromic luminescent material H1 and perform the following heat treatment: heat it at a constant temperature of 50-80°C for 15-25 seconds and then immediately place it in an ultrasonic cleaner filled with ice water for ultrasonication to obtain the blue fluorescent dynamic thermochromic luminescent material H2; The structural formula of the cholesterol derivative is Formula I: The organic solvent includes p-xylene and ethanol, and the volume ratio of p-xylene to ethanol is 8:2 to 2:

8.

2. The dynamic thermochromic luminescent material according to claim 1, wherein: The molar concentration of the cholesterol derivative is 2-30 mM.

3. A method for preparing a dynamic thermochromic luminescent material, characterized in that: include: A cholesterol derivative is dispersed in an organic solvent, and the mixture is sonicated to obtain a clear and transparent solution. 0.1-1.5 molar equivalents of ZnCl2 of the cholesterol derivative of formula I are added thereto, and the mixture is sonicated uniformly in an ultrasonic cleaner to obtain a series of cyan-green fluorescent dynamic thermochromic luminescent materials H1. Take the dynamic thermochromic luminescent material H1 and perform the following heat treatment: heat it at a constant temperature of 50-80°C for 15-25 seconds and then immediately place it in an ultrasonic cleaner filled with ice water for ultrasonication to obtain the blue fluorescent dynamic thermochromic luminescent material H2; The structural formula of the cholesterol derivative is Formula I: The organic solvent includes p-xylene and ethanol, and the volume ratio of p-xylene to ethanol is 8:2 to 2:

8.

4. The method for preparing a dynamic thermochromic luminescent material according to claim 3, wherein: Material H2 can be reversibly converted into material H1 after standing for 30 minutes to 1 hour.

5. The method for preparing a dynamic thermochromic luminescent material according to claim 3, wherein: The synthetic route of the cholesterol derivatives is:

6. A method for repeated decryption and encryption, characterized in that: The following steps are involved: S1. Take a sample of material H1 as described in any one of claims 3 to 5 and write encrypted information on a blank high-temperature and corrosion-resistant orifice plate; S2. Heat the plate encrypted in step S1 at a constant temperature of 50-80°C for 15-25 seconds, and then immediately place it in an ultrasonic cleaner filled with ice water to perform ultrasonic cleaning to decrypt the information. S3, placing the plate under 365nm ultraviolet light to read the encrypted information; S4, the well plate after decryption in step S2 is allowed to stand at room temperature for 30 min-1 h, and then placed under a 365 nm ultraviolet lamp again. The decrypted information will be encrypted again, that is, H2 described in any one of claims 3-5 can be reversibly restored to H1 described in any one of claims 3-5; S5. Repeat the above steps.

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