Thermochromic Copper-Iodine Organic Hybrid Luminescent Materials and Their Preparation Methods

Abstract

The present disclosure discloses a thermochromic copper iodide organic hybrid luminescent material and a preparation method thereof. The chemical formula of the thermochromic copper iodide organic hybrid luminescent material is Cu4I6C 18 H 30 N4; The preparation method includes the following steps: preparing 4-dimethylamino-1-ethylpyridinium iodide; reacting a methanol solution containing 4-dimethylamino-1-ethylpyridinium iodide with a potassium iodide solution containing cuprous iodide to obtain solid M; centrifuging, washing, and drying solid M to obtain the thermochromic copper iodide organic hybrid luminescent material. Single crystals of the thermochromic copper iodide organic hybrid luminescent material are prepared by the slow diffusion method. The thermochromic copper iodide organic hybrid luminescent material of the present disclosure has the characteristics of high fluorescence quantum yield, high stability, and thermochromism.

Description

Technical Field

[0001] The present disclosure relates to the technical field of the preparation of thermochromic luminescent materials, and particularly relates to a thermochromic copper iodine organic hybrid luminescent material and a preparation method thereof. Background Art

[0002] Thermochromic luminescent materials are widely used in the fields of temperature indication, anti-counterfeiting technology, chemical sensors, etc. due to the property that their luminescence properties change with temperature. Compared with traditional thermometers, thermochromic luminescent materials have the advantages of visualization, non-contact measurement, fast response speed, and being unaffected by electric or magnetic fields when applied to temperature indication, and are very suitable for temperature indication in extreme environments, such as being used as coatings for aerospace equipment.

[0003] At present, most thermochromic luminescent materials are based on rare earth elements. Their synthesis process is complex, requires extremely high temperatures, has a high synthesis cost, and it is often the luminescence intensity rather than the peak position that responds to temperature, which leads to the accuracy of temperature indication being easily affected by other factors such as the intensity of the excitation light that affect the peak intensity. And considering the potential supply crisis of rare earth elements and their negative impacts on the environment and human body, it is necessary to develop new thermochromic luminescent materials. Summary of the Invention

[0004] In view of this, the main purpose of the present disclosure is to provide a thermochromic copper iodine organic hybrid luminescent material and a preparation method thereof, in order to at least partially solve at least one of the above-mentioned technical problems.

[0005] To achieve the above object, as an embodiment of one aspect of the present disclosure, a thermochromic copper iodine organic hybrid luminescent material is provided. The chemical formula of the thermochromic copper iodine organic hybrid luminescent material is Cu4I6C 18 H 30 N4.

[0006] As an embodiment of another aspect of the present disclosure, a method for preparing the above-mentioned thermochromic copper iodine organic hybrid luminescent material is provided, including the following steps: preparing 4-dimethylamino-1-ethylpyridinium iodide; reacting a methanol solution containing the above-mentioned 4-dimethylamino-1-ethylpyridinium iodide with a potassium iodide solution containing cuprous iodide to obtain a solid M; centrifuging, washing, and drying the above-mentioned solid M to obtain the above-mentioned thermochromic copper iodine organic hybrid luminescent material.

[0007] As an embodiment of still another aspect of the present disclosure, a method for preparing single crystals of the above-mentioned thermochromic copper iodine organic hybrid luminescent material is provided, including the following steps: preparing 4-dimethylamino-1-ethylpyridinium iodide; injecting a first volume of acetonitrile into a potassium iodide solution of cuprous iodide at a first rate using a needle to obtain a mixture C; injecting a 4-dimethylamino-1-ethylpyridinium iodide solution onto the acetonitrile layer of the mixture C at the first rate using a needle to obtain a system D; and allowing the system D to stand to obtain single crystals of the above-mentioned thermochromic copper iodine organic hybrid luminescent material.

[0008] The high fluorescence quantum yield of the thermochromic copper iodine organic hybrid luminescent material provided in the above embodiment of the present disclosure at 25 °C is due to the heavy atom effect of iodine atoms in the copper iodine cluster and the formation of a relatively rigid structure by ligand stacking, which inhibits non-radiative transitions; the high stability against oxygen, heat, and ultraviolet light is due to the ionic copper iodine hybrid cluster, and the stable electrostatic interaction between the copper iodine inorganic core and the organic ligand; the thermochromism is due to the change in the structure of the copper iodine cluster with temperature, resulting in a change in the emission energy level. Since the above-mentioned thermochromic copper iodine organic hybrid luminescent material exhibits the property of reversible change in emission wavelength and intensity with temperature, it can be used as a phosphor for preparing thermochromic LED devices to indicate the temperature in extreme environments, and can also be applied to fields such as anti-counterfeiting and chemical sensors. Description of the Drawings

[0009] Figure 1 1H NMR spectrum of 4-dimethylamino-1-ethylpyridinium iodide prepared according to an exemplary embodiment of the present disclosure;

[0010] Figure 2 1 is a comparison diagram of the Cu4I6C 18 H 30 N4 luminescent material under natural light (left) and ultraviolet light (right) prepared according to an exemplary embodiment of the present disclosure;

[0011] Figure 3 1 is a comparison diagram of the Cu4I6C 18 H 30 N4 luminescent material and the simulated XRD of the single crystal prepared according to an exemplary embodiment of the present disclosure;

[0012] Figure 4 1 is a variable-temperature emission spectrum diagram of the Cu4I6C 18 H 30 N4 luminescent material under excitation by a 365 nm light source prepared according to an exemplary embodiment of the present disclosure;

[0013] Figure 5 1 is a comparison diagram of the Cu4I6C 18 H30 Thermogravimetric curve of N4 luminescent material in nitrogen atmosphere;

[0014] Figure 6 Cu4I6C prepared according to an exemplary embodiment of the present disclosure 18 H 30 Photothermal stability diagram of the luminescence properties of N4 luminescent material. Detailed implementation manners

[0015] To make the objectives, technical solutions and advantages of the present disclosure clearer and more understandable, the following further elaborates on the present disclosure in detail with reference to specific embodiments and the accompanying drawings.

[0016] Organic-inorganic hybrid clusters based on copper iodide are emerging luminescent materials, which have the advantages of low preparation cost, high luminescence efficiency and good stability, meeting the advantages of sustainable development. Therefore, it is valuable to develop thermochromic luminescent materials based on copper iodide that have double responses of peak position and peak intensity to temperature.

[0017] According to the general inventive concept of one aspect of the present disclosure, a thermochromic copper iodide organic hybrid luminescent material is provided, and the chemical formula of the thermochromic copper iodide organic hybrid luminescent material is Cu4I6C 18 H 30 N4.

[0018] The high fluorescence quantum yield of the thermochromic copper iodide organic hybrid luminescent material provided by the embodiments of the present disclosure at 25 °C is due to the heavy atom effect of iodine atoms in the copper iodide cluster and the relatively rigid structure formed by ligand stacking, which inhibits non-radiative transitions; the high stability to oxygen, heat and ultraviolet light is due to the ionic copper iodide hybrid cluster, and the stable electrostatic interaction between the copper iodide inorganic core and the organic ligand; the thermochromism is due to the change of the structure of the copper iodide cluster with temperature, and the emission energy level also changes accordingly. Due to the above-mentioned property that the emission wavelength and intensity of the thermochromic copper iodide organic hybrid luminescent material change reversibly with temperature, it can be used as a phosphor to prepare thermochromic LED devices to indicate the temperature in extreme environments, and can also be applied to fields such as anti-counterfeiting and chemical sensors.

[0019] According to the embodiments of the present disclosure, the thermochromic copper iodide organic hybrid luminescent material includes an inorganic core and an organic part; wherein, the inorganic core is one-dimensional [Cu4I6] 2- , and the organic part is 4-dimethylamino-1-ethylpyridinium ion.

[0020] In some embodiments of the present disclosure, under the excitation of a room-temperature ultraviolet light source, the thermochromic copper-iodine organic hybrid luminescent material can have a fluorescence quantum yield of 100% for emitting yellow light, and has excellent photothermal stability. Its emission spectrum has a sensitive and reversible response to temperature. From 10K to 200K, its emission peak is around 450nm blue light emission, and as the temperature increases, the luminescence efficiency decreases; from 200K to 225K, it has dual emission peaks at 450nm and 580nm, that is, white light emission; from 250K to 300K, its emission peak is around 580nm, that is, yellow light emission, and as the temperature increases, the luminescence efficiency increases.

[0021] In some embodiments of the present disclosure, the excitation light wavelength range of the thermochromic copper-iodine organic hybrid luminescent material at 25°C is below 460nm, the emission wavelength range is 460nm - 750nm, and the emission peak is located around 580nm. At 25°C, under the excitation of a 360nm wavelength, the fluorescence quantum yield is 99.5%.

[0022] In some embodiments of the present disclosure, for the thermochromic copper-iodine organic hybrid luminescent material from a temperature of 10K to 300K, the emission peak position changes from 450nm below 10K to 580nm below 300K, that is, the luminescence color changes from blue light to white light and then to yellow light as the temperature increases, and this thermochromic process is reversible.

[0023] According to an embodiment of the present disclosure, there is also provided a method for preparing the thermochromic copper-iodine organic hybrid luminescent material as described above, including the following steps: preparing 4-dimethylamino-1-ethylpyridinium iodide; reacting a methanol solution containing 4-dimethylamino-1-ethylpyridinium iodide with a potassium iodide solution containing cuprous iodide to obtain solid M; centrifuging, washing, and drying solid M to obtain the copper-iodine organic hybrid luminescent material.

[0024] The method for preparing the thermochromic copper-iodine organic hybrid luminescent material provided by the embodiments of the present disclosure has low cost, a simple process, high repeatability, and is easy to promote on a large scale.

[0025] In some embodiments of the present disclosure, the molar mass ratio M of 4-dimethylamino-1-ethylpyridinium iodide to cuprous iodide is ≥1:1. For example, the molar mass ratio of 4-dimethylamino-1-ethylpyridinium iodide to cuprous iodide is 2:1, 3:1, 4:1, 6:1, 7:1, 9:1, 15:1, 18:1, 20:1, 23:1, 25:1.

[0026] According to an embodiment of the present disclosure, the steps for preparing 4-dimethylamino-1-ethylpyridinium iodide include: in an inert atmosphere, reacting an acetonitrile solution containing 4-dimethylaminopyridine and iodoethane to obtain solution A, and obtaining solid B after rotary evaporation of solution A; performing recrystallization on solid B to obtain solid C; and drying solid C to obtain 4-dimethylamino-1-ethylpyridinium iodide.

[0027] According to an embodiment of the present disclosure, the reaction conditions for the acetonitrile solution containing 4-dimethylaminopyridine and iodoethane include: the temperature is T≥80°C, and the time is 24h to 48h; the temperature during the recrystallization process of solid B is 20°C to 45°C; the solvent used in the recrystallization process of solid B is any one of the two combinations of methanol and ether, methanol and ethyl acetate; the drying conditions for solid C are: the temperature is 70°C to 85°C, and the time is 20h to 35h. For example, the reaction temperature of the acetonitrile solution containing 4-dimethylaminopyridine and iodoethane is 80°C, 80.5°C, 81°C, and the time is 24h, 25h, 30h, 35h, 40h, 43h, 45h; the temperature during the recrystallization process of solid B is 23°C, 25°C, 28°C, 30°C, 32°C, 35°C, 40°C, 43°C; the drying temperature of solid C is 72°C, 75°C, 78°C, 80°C, 82°C, 85°C, and the time is 22h, 25h, 28h, 30h, 32h, 34h.

[0028] In some embodiments of the present disclosure, the molar ratio N of 4-dimethylaminopyridine to iodoethane in the acetonitrile solution containing 4-dimethylaminopyridine and iodoethane ranges from 1:1 to 1:1.5. For example, the molar ratio of 4-dimethylaminopyridine to iodoethane is 1:1.1, 1:1.15, 1:2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, 1:1.49.

[0029] In some embodiments of the present disclosure, the process of recrystallizing solid B is: dissolving solid B in a small amount of methanol, and then adding an excessive amount of poor solvent ether or ethyl acetate for precipitation. To ensure the purity of solid C, the number of repetitions of the recrystallization process is ≥2. For example, the number of times of the recrystallization process is 3 times, 4 times, 5 times.

[0030] In some embodiments of the present disclosure, the drug dosage or concentration for preparing 4-dimethylamino-1-ethylpyridinium iodide is: 4-dimethylamino-1-ethylpyridinium iodide (278mg), methanol (1mL), copper(I) iodide (380mg), copper(I) iodide (380mg), potassium iodide solution (1g / mL, 4mL).

[0031] According to the embodiments of the present disclosure, the reaction conditions for preparing solid M are as follows: the temperature is 20°C to 30°C, and the time is 20 h to 25 h. For example, the temperature for preparing solid M is 22°C, 25°C, 28°C, 29°C, and the time is 22 h, 23 h, 24 h. The solvents used in the centrifugal washing process of solid M are successively potassium iodide solution at 1 g / mL, water, and ethanol; the drying conditions for solid M are: the temperature is 30°C to 50°C, and the time is 20 h to 40 h. For example, the drying temperature of solid M is 32°C, 35°C, 40°C, 45°C, 48°C, and the time is 22 h, 25 h, 30 h, 35 h, 38 h.

[0032] According to the embodiments of the present disclosure, a method for preparing a single crystal of the above-mentioned thermochromic copper iodine organic hybrid luminescent material is also provided, including the following steps: preparing 4-dimethylamino-1-ethylpyridinium iodide; injecting a first volume of acetonitrile into a potassium iodide solution of cuprous iodide at a first rate with a syringe to obtain a mixture C; injecting a 4-dimethylamino-1-ethylpyridinium iodide solution onto the acetonitrile layer of the mixture C at the first rate with a syringe to obtain a system D; allowing the system D to stand to obtain a single crystal of the thermochromic copper iodine organic hybrid luminescent material.

[0033] In some embodiments of the present disclosure, the dosages of the drugs in the method for preparing a single crystal of the above-mentioned thermochromic copper iodine organic hybrid luminescent material are as follows: cuprous iodide (190 mg), potassium iodide solution (1 g / mL, 2 mL), acetonitrile (2 mL), 4-dimethylamino-1-ethylpyridinium iodide (139 mg), methanol or chloroform (0.5 mL).

[0034] According to the embodiments of the present disclosure, the first rate is 0.5 mL / min to 5 mL / min; the first volume is 1 mL to 30 mL; the solvent of the 4-dimethylamino-1-ethylpyridinium iodide solution is any one of methanol and chloroform. For example, the first rate is 0.8 mL / min, 1 mL / min, 1.2 mL / min, 1.5 mL / min, 2.0 mL / min, 2.3 mL / min, 2.5 mL / min, 3.2 mL / min, 3.5 mL / min, 3.8 mL / min, 4.2 mL / min, 4.5 mL / min, 4.8 mL / min; the first volume is 2 mL, 5 mL, 10 mL, 15 mL, 20 mL, 25 mL, 28 mL.

[0035] According to the embodiments of the present disclosure, the solution layers of the system D are successively a potassium iodide solution of cuprous iodide, acetonitrile, and a 4-dimethylamino-1-ethylpyridinium iodide solution in order from bottom to top.

[0036] According to an embodiment of the present disclosure, the standing conditions of system D: the temperature is 20°C to 35°C, and the time is 20 h to 30 h. For example, the standing temperature of system D is 22°C, 25°C, 28°C, 32°C, and the time is 22 h, 25 h, 28 h.

[0037] The present disclosure will be further illustrated by the following examples. In the following detailed description, for the sake of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is obvious that one or more embodiments can also be implemented without these specific details. Moreover, without conflict, the details in the following embodiments can be combined arbitrarily into other feasible embodiments.

[0038] Example

[0039] In the following examples, unless otherwise specified, the materials, reagents, detection instruments, etc. used can be obtained from commercial channels.

[0040] Preparation of Cu4I6C 18 H 30 The raw materials and solvents for preparing the Cu4I6CHN4 luminescent material include: cuprous iodide (Aladdin, 99.95%), potassium iodide (Sinopharm Chemical Reagent Co., Ltd., analytical pure), 4-dimethylaminopyridine (Aladdin, 99%), iodoethane (Aladdin, 99%), acetonitrile (Sinopharm Chemical Reagent Co., Ltd., analytical pure), methanol (Sinopharm Chemical Reagent Co., Ltd., analytical pure), diethyl ether (Sinopharm Chemical Reagent Co., Ltd., analytical pure), ethanol (Sinopharm Chemical Reagent Co., Ltd., analytical pure), chloroform (Sinopharm Chemical Reagent Co., Ltd., analytical pure).

[0041] Cu4I6C 18 H 30 Preparation of Cu4I6CHN4 Luminescent Material

[0042] S1: Preparation of ligand 4-dimethylamino-1-ethylpyridinium iodide

[0043] (1) Under the protection of nitrogen, 10 mmol of 4-dimethylaminopyridine, 12 mmol of iodoethane and 10 mL of acetonitrile were added to a 50 mL Schlenk tube, the tube mouth was sealed, and after stirring and refluxing at 80°C for 36 hours, solution A was obtained. After rotary evaporation of solution A, solid B was obtained;

[0044] (2) At 25°C, the solid B obtained in (1) was recrystallized using two solvents of methanol and diethyl ether, and the recrystallized solution was filtered to obtain solid C;

[0045] (3) After drying the solid C obtained in (2) in an oven at 80°C for 24 h, the product 4-dimethylamino-1-ethylpyridinium iodide was obtained;

[0046] (4) The product 4-dimethylamino-1-ethylpyridinium iodide was dissolved in deuterated dimethyl sulfoxide, and then the nuclear magnetic resonance hydrogen spectrum of the obtained solution was measured. The test results are as Figure 1 shown.

[0047] As Figure 1 shown, it indicates that the product 4-dimethylamino-1-ethylpyridinium iodide has high purity.

[0048] S2: 1 mmol of 4-dimethylamino-1-ethylpyridinium iodide ligand was dissolved in 1 mL of methanol, and 2 mmol of copper(I) iodide was dissolved in 4 mL of 1 g / mL potassium iodide solution. The above two solutions were mixed, and the mixed solution was stirred and reacted at 25 °C for 24 h to obtain solid M;

[0049] S3: The above solid M was centrifuged successively with 1 g / mL potassium iodide solution, deionized water, and ethanol at 4000 r / min for 3 min, and then placed in an oven at 40 °C to dry for 24 h to obtain the Cu4I6C 18 H 30 N4 luminescent material;

[0050] S4: The Cu4I6C 18 H 30 N4 luminescent material obtained in S3 was compared under natural light and ultraviolet light. The results are as Figure 2 shown.

[0051] As Figure 2 shown, the yellow color of the Cu4I6C 18 H 30 N4 luminescent material under ultraviolet light irradiation is deeper than that of the Cu4I6C 18 H 30 N4 luminescent material under natural light irradiation.

[0052] S5: The emission spectrum of the Cu4I6C 18 H 30 N4 luminescent material obtained in S3 was measured with a fluorescence spectrometer (Hamamatsu absolute PL yield spectrometer C11347). The emission conditions under different excitation lights are listed in Table 1.

[0053] As shown in Table 1, as the excitation wavelength increases from 340 nm to 450 nm, the quantum yield decreases from 102.2% to 23.8%. Thus, it can be seen that ultraviolet light excitation can reach a fluorescence quantum yield of 100%.

[0054] Table 1

[0055]

[0056] S6: Use an X-ray diffractometer (X-PERTPRO powder X-ray diffractometer) to perform X-ray diffraction (XRD) on the Cu4I6C 18 H 30 N4 luminescent material obtained in S3. The comparison between the obtained XRD pattern and the XRD pattern simulated by single crystal is as Figure 3 shown.

[0057] As Figure 3 shown, since the diffraction peaks of the XRD pattern of the Cu4I6C 18 H 30 N4 luminescent material and the XRD pattern simulated by single crystal are almost identical, it can be seen that the Cu4I6C 18 H 30 N4 luminescent material powder prepared in S3 has a high purity.

[0058] S7: Use a steady-state / transient fluorescence spectrometer (Fluorolog-3-Tau and deltaflex) to measure the temperature-dependent emission spectrum of the Cu4I6C 18 H 30 N4 luminescent material obtained in S3. The temperature-dependent emission spectrum from 10 K to 300 K under 365 nm light source excitation is as Figure 4 shown.

[0059] As Figure 4 shown, for the Cu4I6C 18 H 30 N4 luminescent material obtained in S3, from 10 K to 200 K, its emission peak is around 450 nm blue light emission. As the temperature increases, the luminescence efficiency decreases; from 200 K to 225 K, it has dual emission peaks at 450 nm and 580 nm, that is, white light emission; from 250 K to 300 K, its emission peak is around 580 nm, that is, yellow light emission. As the temperature increases, the luminescence efficiency increases. Thus, it can be seen that the Cu4I6C 18 H 30 N4 luminescent material exhibits obvious thermochromic properties.

[0060] As Figure 4 shown, for the Cu4I6C 18 H 30 N4 luminescent material obtained in S3, from a temperature of 10 K to 300 K, the emission peak position changes from 450 nm below 10 K to 580 nm below 300 K, that is, the emission color changes from blue light to white light and then to yellow light as the temperature increases. This thermochromic process is reversible.

[0061] S8: Use a Q5000IR thermal gravimetric analyzer to test the thermal decomposition temperature of the Cu4I6C 18 H 30 N4 luminescent material obtained in S3. The thermogravimetric analysis graph is as Figure 5 shown.

[0062] As Figure 5 shown, the thermal decomposition temperature of the Cu4I6C 18 H 30 N4 luminescent material obtained in S3 is as high as 309.93 °C, indicating that the luminescent material has good thermal stability.

[0063] S9: Expose the Cu4I6C 18 H 30 N4 luminescent material obtained in S3 to air at 80 °C, 100 °C, and 120 °C for 72 h, and measure the luminescence efficiency of the Cu4I6C 18 H 30 N4 luminescent material every 12 h. The results are as Figure 6 shown.

[0064] As Figure 6 shown, the Cu4I6C 18 H 30 N4 luminescent material obtained in S3 is exposed to air at 80 °C, 100 °C, and 120 °C for 72 h, and the luminescence efficiency remains basically unchanged, indicating that the Cu4I6C 18 H 30 N4 luminescent material obtained in S3 has no strict requirements for the use environment.

[0065] S10: Irradiate the Cu4I6C 18 H 30 N4 luminescent material obtained in S3 with a 365 nm light source in a nitrogen atmosphere for 72 h, and measure the luminescence efficiency of the Cu4I6C 18 H 30 N4 luminescent material every 12 h. The results are as Figure 6 shown.

[0066] As Figure 6 shown, the Cu4I6C 18 H 30 N4 luminescent material obtained in S3 is irradiated with a 365 nm light source in a nitrogen atmosphere for 72 h, and the luminescence efficiency remains basically unchanged, showing excellent optical stability.

[0067] S11: Under the excitation of a 365 nm light source, treat the Cu4I6C 18 H 30For the N4 luminescent material, during the process of recovering from 77 K to 300 K, the changes in its chromaticity coordinates (CIE), relative color temperature (CCT), and relative color rendering index (CRI) measured with a luminance meter (SpectraScan PR670) are listed in Table 2.

[0068] As shown in Table 2, for Cu4I6C obtained from S3 18 H 30 During the process of heating the N4 luminescent material from 77 K to 300 K, the emitted light changes from blue to white and finally to yellow. It can be seen from Table 2 that for Cu4I6C obtained from S3 18 H 30 The N4 luminescent material has different relative color temperatures and relative color rendering indices at different temperatures.

[0069] Table 2

[0070]

[0071] Cu4I6C 18 H 30 Preparation of single crystal of N4 luminescent material

[0072] S1: Prepare the ligand 4-dimethylamino-1-ethylpyridinium iodide

[0073] The preparation steps are the same as S1 in "Preparation of 18 H 30 Cu4I6C N4 luminescent material".

[0074] S2: Inject 2 mL of acetonitrile into the potassium iodide solution of cuprous iodide at a rate of 1 mL / min with a syringe to obtain mixture C; among them, in the potassium iodide solution of cuprous iodide, the concentration of cuprous iodide is 1 mmol, and the concentration of potassium iodide is 1 g / mL;

[0075] S3: Inject 0.5 mL of a chloroform solution of 4-dimethylamino-1-ethylpyridinium iodide with a concentration of 1 mmol / mL into the acetonitrile layer of mixture C at a rate of 1 mL / min with a syringe to obtain system D;

[0076] S4: Let system D stand at 25 °C for 24 h to obtain a single crystal of a thermochromic copper-iodine organic hybrid luminescent material.

[0077] S5: Use a four-circle single-crystal diffractometer (Rigaku Oxford diffraction Gemini S Ultradiffractometer) to measure the crystallographic data of the Cu4I6C 18 H 30 N4 luminescent material single crystal obtained in S4, and the results are listed in Table 3.

[0078] As shown in Table 3, the Cu4I6C obtained in S4 18 H 30 Relevant information on the unit cell parameters of the single crystal of the H4N4 luminescent material and properties such as the predicted density.

[0079] Table 3

[0080]

[0081] The high fluorescence quantum yield of the thermochromic copper iodide organic hybrid luminescent material provided by the embodiments of the present disclosure at 25°C is due to the heavy atom effect of iodine atoms in the copper iodide cluster and the relatively rigid structure formed by ligand stacking, which inhibits non-radiative transitions; the high stability against oxygen, heat, and ultraviolet light is due to the ionic copper iodide hybrid cluster, and the stable electrostatic interaction between the copper iodide inorganic core and the organic ligand; the thermochromism is due to the change in the structure of the copper iodide cluster with temperature, and thus the emission energy level changes. The above-mentioned thermochromic copper iodide organic hybrid luminescent material can be used as a phosphor to prepare thermochromic LED devices to indicate the temperature in extreme environments, and can also be applied to fields such as anti-counterfeiting and chemical sensors.

[0082] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present disclosure. It should be understood that the above are only specific embodiments of the present disclosure and do not limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A thermochromic copper-iodine organic hybrid luminescent material, characterized in that The chemical formula of the thermochromic copper iodine organic hybrid luminescent material is Cu4I6C 18 H 30 N4, which consists of a one-dimensional [Cu4I6] 2- inorganic core and 4-dimethylamino-1-ethylpyridinium cation ligands; the thermochromic copper-iodine organic hybrid luminescent material exhibits a reversible emission transition from blue light to white light and then to yellow light in the temperature range of 10K to 300K, and the emission spectrum contains a double peak of 450nm and 580nm in the temperature range of 200 - 225K, achieving white light emission; the fluorescence quantum yield of the thermochromic copper-iodine organic hybrid luminescent material is 99.5% under excitation at 25 °C and a wavelength of 360nm; The crystal system of the single crystal of the thermochromic copper iodine organic hybrid luminescent material is monoclinic, the space group is P21 / c, and the crystal axis lengths are respectively: a = 8.8326(5) Å, b = 18.6933(12) Å, c = 19.4424(16) Å. The interaxial angles of the unit cell are respectively: α = 90°, β = 99.089(6)°, γ = 90°, and the unit cell volume is 3169.8(4) Å 3 , and each unit cell contains 4 molecules.

2. A method for preparing a single crystal of the thermochromic copper-iodine organic hybrid luminescent material according to claim 1, comprising the following steps: Preparing 4-dimethylamino-1-ethylpyridinium iodide, including: in an inert atmosphere, reacting an acetonitrile solution containing 4-dimethylaminopyridine and iodoethane to obtain solution A, rotary evaporating solution A to obtain solid B, recrystallizing solid B to obtain solid C, and drying solid C to obtain the 4-dimethylamino-1-ethylpyridinium iodide; Injecting a first volume of acetonitrile into a potassium iodide solution of cuprous iodide at a first rate using a syringe to obtain mixture C; Injecting a 4-dimethylamino-1-ethylpyridinium iodide solution onto the acetonitrile layer of mixture C at a first rate using a syringe to obtain system D; Allowing system D to stand to obtain the single crystal of the thermochromic copper-iodine organic hybrid luminescent material.

3. The method for preparing a single crystal of the thermochromic copper-iodine organic hybrid luminescent material according to claim 2, characterized in that the reaction conditions of the acetonitrile solution containing 4-dimethylaminopyridine and iodoethane include: the temperature is T≥80 °C, and the time is 24 h - 48 h; the temperature during the recrystallization process of solid B is 20 °C - 45 °C; the solvent used in the recrystallization process of solid B is any one of two combinations: methanol and ether, methanol and ethyl acetate; the drying conditions of solid C: the temperature is 70 °C - 85 °C, and the time is 20 h - 35 h.

4. The method for preparing a single crystal of the thermochromic copper-iodine organic hybrid luminescent material according to claim 2, characterized in that the first rate is 0.5 mL / min - 5 mL / min; the first volume is 1 mL - 30 mL; the solvent of the 4-dimethylamino-1-ethylpyridinium iodide solution is any one of methanol and chloroform.

5. The method for preparing a single crystal of the thermochromic copper-iodine organic hybrid luminescent material according to claim 2, characterized in that the solution layers of system D are, in order from bottom to top, a potassium iodide solution of cuprous iodide, acetonitrile, and a 4-dimethylamino-1-ethylpyridinium iodide solution.

6. The method for preparing a single crystal of the thermochromic copper-iodine organic hybrid luminescent material according to claim 2, characterized in that the standing conditions of system D: the temperature is 20 °C - 35 °C, and the time is 20 h - 30 h.

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