A thermochromic luminescent material and a preparation method thereof

Abstract

The present invention belongs to the technical field of luminescent materials, and specifically discloses a thermochromic luminescent material and a preparation method thereof. The material with thermochromic luminescent properties has a chemical formula of (C 11 H 26 N)2Cu2I4. It has obvious thermochromic luminescent characteristics. At room temperature, it exhibits blue light emission under the excitation of 365 nm ultraviolet light, while when the temperature rises to 100 °C, it will exhibit warm white light emission under the excitation of 365 nm ultraviolet light, and can be especially used as a thermochromic luminescent material. Moreover, the preparation process of this material is simple, low in cost, and good in repeatability.

Description

Technical field

[0001] The present invention belongs to the technical field of luminescent materials, and more specifically, relates to a kind of thermochromic luminescent material and its preparation method. Background technique

[0002] Luminescent materials are closely related to human daily life and have been widely used in the fields of lighting and display, medical imaging, non-destructive testing, information anti-counterfeiting, etc. Among them, stimulus-responsive luminescent materials refer to a class of intelligent materials whose optical properties such as emission peak position, intensity, color, etc. change correspondingly under external environmental stimuli (such as heat, light, electricity, pressure, solvent, humidity, etc.). Because they have broad application prospects in the fields of fluorescence sensing, anti-counterfeiting, optical switches, optical storage, invisible inks and biological imaging, etc., they have received extensive attention from scientific researchers.

[0003] Among various different types of stimulation methods, "heat" has the advantages of low cost, rich sources, strong controllability, simple and convenient operation, and is related to an important physical and chemical parameter - temperature. These characteristics make thermochromic luminescent materials have important practical application value. For example, temperature indicating materials for intracellular and environmental use can quickly and sensitively detect temperature; anti-counterfeiting materials for commodities can facilitate consumers to quickly identify authenticity; thermoresponsive fluorescent color-changing clothing or ornaments can meet consumers' psychology of seeking novelty. And with the improvement of material properties, it is also expected to be applied to a series of high-end application fields, such as thermal control information display, ultra-sensitive fluorescent thermometers, high-spatial-resolution thermal imaging, etc. Therefore, developing new thermochromic luminescent materials has important scientific research significance and practical application value. Summary of the invention

[0004] Aiming at the above defects or improvement requirements of the prior art, the purpose of the present invention is to provide a kind of thermochromic luminescent material and its preparation method. The chemical formula of this material is (C 11 H 26 N)2Cu2I4, which has obvious thermochromic luminescent characteristics. It shows blue light emission under the excitation of 365nm ultraviolet light at room temperature, while when the temperature rises to 100 °C, it will show warm white light emission under the excitation of 365nm ultraviolet light, and can be especially used as a thermochromic luminescent material; moreover, the preparation process of this material is simple, low in cost and good in repeatability.

[0005] To achieve the above purpose, according to one aspect of the present invention, a material with thermochromic luminescent properties is provided, characterized in that the chemical formula of the material is (C 11 H 26 N)2Cu2I4.

[0006] As a further preference of the present invention, the (C 11 H26 (C 11 H 26 N)2Cu2I4 is a crystal material with a zero-dimensional crystal structure; the zero-dimensional crystal structure is composed of [Cu2I4] 2- dimers surrounded by organic cations [C 11 H 26 N] + to form a zero-dimensional crystal structure.

[0007] As a further preference of the present invention, the (C 11 H 26 N)2Cu2I4 is specifically a single crystal of (C 11 H 26 N)2Cu2I4; when it is at room temperature, it can emit blue light under the excitation of 365 nm ultraviolet light; when it is at 100 °C, it can emit warm white light under the excitation of 365 nm ultraviolet light;

[0008] Or, the (C 11 H 26 N)2Cu2I4 is specifically nanocrystals of (C 11 H 26 N)2Cu2I4; when it is at room temperature, it can emit blue light under the excitation of 365 nm ultraviolet light; when it is at 100 °C, it can emit warm white light under the excitation of 365 nm ultraviolet light.

[0009] According to another aspect of the present invention, the present invention provides the application of (C 11 H 26 N)2Cu2I4 material as a thermochromic luminescent material; characterized in that when the ambient temperature changes, the luminescent color of the material will change.

[0010] As a further preference of the present invention, when the (C 11 H 26 N)2Cu2I4 material is at room temperature, it can emit blue light under the excitation of 365 nm ultraviolet light;

[0011] When the (C 11 H 26 N)2Cu2I4 material is at 100 °C, it can emit warm white light under the excitation of 365 nm ultraviolet light;

[0012] Preferably, when the ambient temperature of the (C 11 H 26 N)2Cu2I4 material drops from 100 °C to room temperature, it can recover from emitting warm white light to emitting blue light under the excitation of 365 nm ultraviolet light.

[0013] As a further preference of the present invention, specifically, the thermochromic luminescent material is applied to fluorescence temperature measurement, thermal imaging or temperature sensing.

[0014] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned material, which is specifically (C 11 H 26 N)2Cu2I4 single crystal, and is characterized in that the preparation method includes the following steps:

[0015] (1) Weigh C 11 H 26 NI and CuI according to a molar ratio of 1:1 to prepare the raw materials C 11 H 26 NI and CuI. Then, add H3PO2 and C 11 H 26 NI and CuI into the organic solvent N,N-dimethylformamide (DMF), and obtain a precursor solution after ultrasonic treatment;

[0016] (2) Filter the precursor solution obtained in the step (1), take the filtrate and place it in a container, and let the solvent in the filtrate volatilize by standing, so that (C 11 H 26 N)2Cu2I4 single crystal precipitates and grows; when the standing time reaches the preset time, take out the grown (C 11 H 26 N)2Cu2I4 single crystal.

[0017] As a further preference of the present invention, in the step (1), calculated by (C 11 H 26 N)2Cu2I4, the concentration of the precursor solution is 1.28 - 1.67 mol / L.

[0018] According to still another aspect of the present invention, the present invention provides a method for preparing the above-mentioned material, which is specifically (C 11 H 26 N)2Cu2I4 nanocrystal, and is characterized in that the preparation method includes the following steps:

[0019] (1) Weigh C 11 H 26 NI and CuI according to a molar ratio of 1:1 to prepare the raw materials C 11 H 26 NI and CuI. Then, add H3PO2 and C 11 H 26 NI and CuI into the organic solvent N,N-dimethylformamide (DMF), and obtain a precursor solution after ultrasonic treatment;

[0020] (2) Inject the precursor solution obtained in the step (1) into an antisolvent system composed of toluene and oleic acid under stirring conditions, where the volume ratio of toluene to oleic acid is 10 to 15, and (C 11 H 26 N)2Cu2I4 nanocrystals can be precipitated.

[0021] As a further preference of the present invention, calculated by (C 11 H 26 N)2Cu2I4, the concentration of the precursor solution is 0.49 to 0.97 mol / L.

[0022] Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved:

[0023] (1) The thermochromic luminescent material (C 11 H 26 N)2Cu2I4 provided by the present invention (such as, (C 11 H 26 N)2Cu2I4 single crystal, (C 11 H 26 N)2Cu2I4 nanocrystals, etc.), shows blue light emission under the excitation of 365 nm ultraviolet light at room temperature, while when the temperature rises to 100 °C, it will show warm white light emission (color coordinates are (0.36, 0.41), color temperature is 4719 K) under the excitation of 365 nm ultraviolet light, having obvious thermochromic luminescent characteristics. And, (C 11 H 26 N)2Cu2I4 material also shows efficient blue light emission characteristics at room temperature. For example, at room temperature, under the excitation of 365 nm ultraviolet light, the fluorescence quantum yields (PLQY) of (C 11 H 26 N)2Cu2I4 single crystal and nanocrystals are as high as 91.4% and 66.7% respectively. In addition, the thermochromic luminescent phenomenon of this material takes the comparison between 100 °C and room temperature conditions as an example, and does not mean that it only shows at 100 °C; for example, when the temperature continuously rises from room temperature to 86 °C, with the increase of temperature, the emission color of the material gradually changes from blue light to warm white light emission; and when the temperature continues to rise from 86 °C to above 100 °C (of course, the temperature cannot exceed the melting point of the material), with the increase of temperature, the material still shows warm white light emission; when the temperature is lower than room temperature, the luminescent characteristics of the material are basically the same as those under room temperature conditions.

[0024] Furthermore, the reason for showing efficient blue light emission characteristics is that the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 crystal in the present invention (such as, (C 11 H26 N)2Cu2I4 single crystals and (C 11 H 26 N)2Cu2I4 nanocrystals), which have a unique zero-dimensional crystal structure, and the [Cu2I4] 2- dimers are separated from each other and surrounded by organic cations [C 11 H 26 N] + to form a zero-dimensional crystal structure. The electron-hole pairs generated by photoexcitation are confined within the [Cu2I4] 2- dimers, showing a strong quantum confinement effect, and thus having a very high luminescence efficiency.

[0025] (2) Currently, most phosphors and perovskite luminescent materials rarely exhibit thermochromic luminescence properties. Different from these phosphors and perovskite luminescent materials, the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 in the present invention emits blue light under 365 nm ultraviolet light excitation at room temperature; when the temperature is raised to 100 °C, it turns into warm white light emission; when the temperature is cooled back to room temperature, it returns to blue light emission (that is, the thermochromic luminescence property in the present invention is reversible). Therefore, the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 single crystals and nanocrystals can be especially applied to the fields of fluorescence temperature measurement, thermal imaging, and temperature sensing.

[0026] (3) The thermochromic luminescent material (C 11 H 26 N)2Cu2I4 in the present invention, such as (C 11 H 26 N)2Cu2I4 single crystals and (C 11 H 26 N)2Cu2I4 nanocrystals, can be prepared by the room-temperature solvent evaporation method and the ligand-assisted reprecipitation method respectively. The preparation process is simple, low-cost, and has good repeatability. Compared with the complex high-temperature sintering process required for phosphors in the prior art, which is costly, the present invention can prepare high-quality (C 11 H 26 N)2Cu2I4 single crystals and nanocrystals by using a low-cost room-temperature solution process. This preparation process is simple and convenient to operate, has good repeatability, requires very low equipment requirements, and can be synthesized in large quantities at room temperature, showing great commercial application prospects.

[0027] (4) In addition, different from the fact that most current commercial phosphors rely on rare earth elements and perovskite luminescent materials contain heavy metal elements such as lead, the (C 11 H 26The (C₂H₅NH)₂Cu₂I₄ material belongs to copper-based halides. By utilizing copper elements with abundant reserves in the earth's crust and being environmentally friendly, a thermochromic luminescent material can be prepared, which has the characteristics of low cost, environmental friendliness, and non-toxicity.

[0028] In summary, the copper-based halide thermochromic luminescent material (C 11 H 26 ₂H₅NH)₂Cu₂I₄ in the present invention has excellent luminescent properties and novel thermochromic luminescent characteristics, enabling the (C 11 H 26 ₂H₅NH)₂Cu₂I₄ material to have good application prospects in the fields of luminescent materials and stimulus-responsive fluorescent materials. Brief Description of the Drawings

[0029] Figure 1 It is a schematic diagram of the crystal structures of the thermochromic luminescent material (C 11 H 26 ₂H₅NH)₂Cu₂I₄ single crystal and nanocrystal prepared in the present invention. As can be seen from Figure 1 it, the crystal structures of the (C 11 H 26 ₂H₅NH)₂Cu₂I₄ single crystal and nanocrystal are zero-dimensional crystal structures formed by [Cu₂I₄] 2- dimers surrounded by organic cations [C 11 H 26 ₂H₅NH] + , where the [Cu₂I₄] 2- dimer is composed of two [CuI₃] 2- triangles connected by sharing edges (the specific parameters of this crystal structure are shown in Table 1 later).

[0030] Figure 2 It is the simulated XRD and powder XRD patterns of the thermochromic luminescent material (C 11 H 26 ₂H₅NH)₂Cu₂I₄ single crystal prepared in Example 1. As can be seen from the figure, the two match very well, indicating that the prepared single crystal has a high phase purity (wherein, the simulated XRD of the (C 11 H 26 ₂H₅NH)₂Cu₂I₄ single crystal is a standard card obtained through single crystal structure analysis, while the powder XRD is obtained by grinding the (C 11 H 26 ₂H₅NH)₂Cu₂I₄ single crystal into powder for testing).

[0031] Figure 3 It is the thermochromic luminescent material (C 11 H 26Emission and excitation spectra of (C₆H₅N)₂Cu₂I₄ single crystal; in the figure, the emission peak is located at 495 nm, the full width at half maximum is 99 nm, the peak of the excitation spectrum is 338 nm, and the Stokes shift is 158 nm.

[0032] Figure 4 is the thermochromic luminescent material (C 11 H 26 Transmission electron microscope image of (C₆H₅N)₂Cu₂I₄ nanocrystals prepared in Example 4. The nanocrystals are quasi-spherical with an average particle size of about 4.52 nm.

[0033] Figure 5 is the thermochromic luminescent material (C 11 H 26 Simulated XRD and XRD patterns of (C₆H₅N)₂Cu₂I₄ nanocrystals prepared in Example 5. It can be seen from the figure that the two match well, indicating that the prepared nanocrystals are of pure phase.

[0034] Figure 6 is the thermochromic luminescent material (C 11 H 26 Emission and excitation spectra of (C₆H₅N)₂Cu₂I₄ nanocrystals prepared in Example 6; in the figure, the emission peak is located at 487 nm, the full width at half maximum is 91 nm, the peak of the excitation spectrum is 335 nm, and the Stokes shift is 153 nm.

[0035] Figure 7 is the thermochromic luminescent material (C 11 H 26 Luminescence photographs of (C₆H₅N)₂Cu₂I₄ single crystal prepared in Example 3 under 365 nm ultraviolet light excitation as the temperature gradually increases from 25 °C to 113 °C; among them, Figure 7 (a) in corresponds to 25 °C, Figure 7 (b) in corresponds to 81 °C, Figure 7 (c) in corresponds to 86 °C, Figure 7 (d) in corresponds to 113 °C.

[0036] Figure 8 are the thermochromic luminescent materials (C 11 H 26 (C₆H₅N)₂Cu₂I₄ single crystal and (C 11 H 26 Photographs of (C₆H₅N)₂Cu₂I₄ nanocrystals prepared in Examples 1 and 4 under natural light, at room temperature under 365 nm ultraviolet light irradiation, and at 100 °C under 365 nm ultraviolet light irradiation; among them, Figure 8 (a) in corresponds to (C 11 H 26 (C₆H₅N)₂Cu₂I₄ single crystal, Figure 8in (b) corresponds to C 11 H 26 N)2Cu2I4 nanocrystals. At room temperature, (C 11 H 26 N)2Cu2I4 single crystals and nanocrystals emit blue light; when the temperature is raised to 100 °C, (C 11 H 26 N)2Cu2I4 single crystals and nanocrystals transform into warm white light emission; when the temperature is cooled back to room temperature, it returns to blue light emission.

[0037] Figure 9 is the normalized emission spectra of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 single crystal prepared in Example 1 emitting blue light at room temperature and warm white light at 100 °C.

[0038] Figure 10 For the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 single crystal prepared in Example 1, the color coordinates of the blue light emission at room temperature are (0.18, 0.30), and the color coordinates of the warm white light emission when the temperature is heated to 100 °C are (0.36, 0.41). Detailed implementation mode

[0039] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further details the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] The thermochromic luminescent material (C 11 H 26 N)2Cu2I4 in the present invention, taking the preparation of single crystal materials as an example, can be obtained by slowly evaporating the saturated solution of the precursor to allow the compound to crystallize and grow to obtain (C 11 H 26 N)2Cu2I4 single crystals, which is a low-cost room-temperature solution process; if it is necessary to prepare (C 11 H 26 N)2Cu2I4 nanocrystals, it can be prepared by ligand-assisted reprecipitation at room temperature, which is also a low-cost room-temperature solution process.

[0041] The following are specific examples:

[0042] Example 1

[0043] In this example, the thermochromic luminescent material (C 11H 26 Preparation method of (C

[0044] (1) Weigh and mix 1 mmol C 11 H 26 NI (CAS No.: 15066 - 80 - 5, purchased from Aladdin Chemical Reagent Network) and 1 mmol CuI in a freezing tube, and then inject 700 μL of organic solvent DMF and 80 μL of H3PO2 (50 wt.% in H2O) into it. Ultrasonically dissolve the above mixture to obtain a clear precursor solution (the reason for using H3PO2 in this step is to inhibit the oxidation of Cu + . In addition, the dosage of H3PO2 can be flexibly adjusted according to the actual situation. For example, the volume ratio of H3PO2 to the organic solvent can be 1:14 - 1:9);

[0045] (2) Filter the reaction precursor solution obtained in step (1) through a 0.22 μm filter head into a glass bottle, and place the glass bottle in a fume hood;

[0046] (3) Let the filtered precursor solution obtained in step (2) stand in the fume hood for 3 days, and the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 single crystal will precipitate and grow;

[0047] (4) Rinse the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 single crystal obtained in step (3) with n - hexane and air - dry it naturally to obtain a clean thermochromic luminescent material (C 11 H 26 N)2Cu2I4 single crystal.

[0048] Example 2

[0049] In this example, the preparation method of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 single crystal is as follows:

[0050] (1) Weigh and mix 1.3 mmol C 11 H 26 NI and 1.3 mmol CuI in a freezing tube, and then inject 700 μL of organic solvent DMF and 80 μL of H3PO2 (50 wt.% in H2O) into it. Ultrasonically dissolve the above mixture to obtain a clear precursor solution;

[0051] (2) Filter the reaction precursor solution obtained in step (1) into a glass bottle using a 0.22 μm filter head, and place the glass bottle statically in a fume hood;

[0052] (3) Let the filtered precursor solution obtained in step (2) stand in the fume hood for 5 days, and single crystals of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 will precipitate and grow;

[0053] (4) Rinse the single crystals of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 obtained in step (3) with n-hexane and air-dry naturally to obtain clean single crystals of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4.

[0054] The crystals obtained in this example are similar to those in Example 1, and their appearances are all colorless, transparent, and crystal clear.

[0055] Example 3

[0056] The preparation method of single crystals of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 in this example is as follows:

[0057] (1) Weigh and mix 1 mmol of C 11 H 26 NI and 1 mmol of CuI in a freezing tube, and then inject 700 μL of the organic solvent DMF and 50 μL of H3PO2 (50 wt.% in H2O) into it. Ultrasonically dissolve the above mixture to obtain a clear precursor solution;

[0058] (2) Filter the reaction precursor solution obtained in step (1) into a glass bottle using a 0.22 μm filter head, and place the glass bottle statically in a fume hood;

[0059] (3) Let the filtered precursor solution obtained in step (2) stand in the fume hood for 3 days, and single crystals of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 will precipitate and grow;

[0060] (4) Rinse the single crystals of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 obtained in step (3) with n-hexane and air-dry naturally to obtain clean single crystals of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4.

[0061] The crystals obtained in this example are similar to those in Example 1, with a colorless, transparent, and crystal-clear appearance.

[0062] Example 4

[0063] In this example, a preparation method of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 nanocrystals is as follows:

[0064] (1) Weigh and mix 1 mmol of C 11 H 26 NI and 1 mmol of CuI in a freezing tube, and then inject 2000 μL of the organic solvent DMF and 60 μL of H3PO2 (50 wt.% in H2O) into it. Ultrasonically dissolve the above mixture to obtain a clear precursor solution (of course, the dosage of H3PO2 can also be flexibly adjusted according to the actual situation. For example, the volume ratio of H3PO2 to the organic solvent can be 1:33 - 1:19);

[0065] (2) Measure 500 μL of the reaction precursor solution obtained in step (1) and quickly inject it into an antisolvent system composed of 5 mL of toluene and 500 μL of oleic acid under vigorous stirring (where oleic acid is used as a ligand, and its dosage can also be flexibly adjusted according to the actual situation). After injection, the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 nanocrystals will precipitate soon;

[0066] (3) Centrifuge the stock solution obtained in step (2) directly at a speed of 7000 rpm for 3 min. After centrifugation, pour off the supernatant and take the precipitate as the (C 11 H 26 N)2Cu2I4 nanocrystal powder.

[0067] Example 5

[0068] In this example, a preparation method of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 nanocrystals is as follows:

[0069] (1) Weigh and mix 2 mmol of C 11 H 26 NI and 2 mmol of CuI in a freezing tube, and then inject 2000 μL of the organic solvent DMF and 60 μL of H3PO2 (50 wt.% in H2O) into it. Ultrasonically dissolve the above mixture to obtain a clear precursor solution;

[0070] (2) Measure 500 μL of the precursor solution obtained in step (1), and quickly inject it into an anti-solvent system composed of 7.5 mL of toluene and 500 μL of oleic acid under vigorous stirring. After injection, the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 nanocrystals will precipitate soon;

[0071] (3) Centrifuge the stock solution obtained in step (2) directly at a rotational speed of 7000 rpm for 3 min. After centrifugation, pour off the supernatant and take the precipitate, which is the (C 11 H 26 N)2Cu2I4 nanocrystal powder.

[0072] Example 6

[0073] In this example, the preparation method of the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 nanocrystals is as follows:

[0074] (1) Weigh and mix 1 mmol of C 11 H 26 NI and 1 mmol of CuI in a freezing tube, and then inject 1900 μL of organic solvent DMF and 100 μL of H3PO2 (50 wt.% in H2O) into it. Ultrasonically dissolve the above mixture to obtain a clear precursor solution;

[0075] (2) Measure 500 μL of the reaction precursor solution obtained in step (1), and quickly inject it into an anti-solvent system composed of 5 mL of toluene and 500 μL of oleic acid under vigorous stirring. After injection, the thermochromic luminescent material (C 11 H 26 N)2Cu2I4 nanocrystals will precipitate soon;

[0076] (3) Centrifuge the stock solution obtained in step (2) directly at a rotational speed of 7000 rpm for 3 min. After centrifugation, pour off the supernatant and take the precipitate, which is the (C 11 H 26 N)2Cu2I4 nanocrystal powder.

[0077] The thermochromic luminescent materials (C 11 H 26 N)2Cu2I4 single crystals and nanocrystals obtained in Examples 1 - 6 of the present invention emit blue light under 365 nm ultraviolet light excitation at room temperature, and their PLQYs are 91.4% and 66.7% respectively. Specifically:

[0078] (C 11 H 26(C₃H₆N)₂Cu₂I₄ single crystal emits blue light under 365 nm ultraviolet light excitation at room temperature. The emission peak is located at 495 nm, the full width at half maximum is 99 nm, and the PLQY is as high as 91.4%, showing strong blue light emission characteristics (as Figure 3 shown).

[0079] (C 11 H 26 N)₂Cu₂I₄ nanocrystals emit blue light under 365 nm ultraviolet light excitation at room temperature. The emission peak is located at 487 nm, the full width at half maximum is 91 nm, and its PLQY is 66.7%, also showing good blue light emission characteristics.

[0080] (C 11 H 26 N)₂Cu₂I₄ crystal belongs to the monoclinic system, and the space group is P2₁ / n; both its single crystal and nanocrystals have a unique zero-dimensional crystal structure, and the [Cu₂I₄] 2- dimer is surrounded by organic cations [C 11 H 26 N] + to form a zero-dimensional crystal structure (as Figure 1 shown). The structural parameters of the (C 11 H 26 N)₂Cu₂I₄ crystal are shown in Table 1 below, and the crystal structure data was obtained through single crystal structure analysis.

[0081] Table 1: Structural parameters of (C 11 H 26 N)₂Cu₂I₄ crystal

[0082]

[0083]

[0084] At room temperature, (C 11 H 26 N)₂Cu₂I₄ single crystal and nanocrystals emit blue light under ultraviolet light excitation. When the temperature rises to 100 °C, they emit warm white light, showing novel thermochromic luminescence characteristics, as Figure 7 and Figure 8 shown. Taking the (C 11 H 26 N)₂Cu₂I₄ single crystal as an example, the (C 11 H 26 N)₂Cu₂I₄ single crystal prepared in Example 3 was excited by 365 nm ultraviolet light, and the environmental temperature was adjusted so that the temperature gradually increased from 25 °C to 113 °C. The luminescence effect was detected once every 1 °C increase in temperature. The results are as follows: When the temperature gradually increased from 25 °C to 86 °C, (C 11 H 26The luminescence color of (C₆H₅N)₂Cu₂I₄ single crystal gradually changes from blue light emission to warm white light emission; when the temperature continues to rise from 86 °C to 113 °C, it still remains warm white light emission (as Figure 7 shown).

[0085] Moreover, the thermochromic luminescence phenomenon of (C 11 H 26 ₆H₅N)₂Cu₂I₄ material is reversible. When the temperature is raised to 100 °C, it shows the characteristics of warm white light emission. When the temperature is cooled to room temperature, it will return to blue light emission again.

[0086] All kinds of chemical reagents used in the above embodiments are commercially available products. In addition, the preparation methods in the above embodiments are only examples, and various parameter conditions can be flexibly adjusted according to the actual situation. For example, the concentration of the precursor solution can be lower or higher (for example, it can reach a supersaturated state), the standing time can also be adjusted according to the crystal growth situation, and the amounts of organic solvents such as toluene, oleic acid, DMF, H₃PO₂, etc. can also be flexibly adjusted. Room temperature in the present invention means 25 °C ± 3 °C.

[0087] It is easy for those skilled in the art to understand that the above description is only the preferred embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. (C 11 H 26 N)2Cu2I4 material's application as a thermochromic luminescent material, characterized in that, When the ambient temperature changes, the luminescent color of the material will change; the (C 11 H 26 N)2Cu2I4 material is a (C 11 H 26 N)2Cu2I4 single crystal or a (C 11 H 26 N)2Cu2I4 nanocrystal; When the (C 11 H 26 N)2Cu2I4 material is at room temperature, it can emit blue light under 365 nm ultraviolet light excitation; and when the (C 11 H 26 N)2Cu2I4 material is a (C 11 H 26 N)2Cu2I4 single crystal, the emission peak is at 495 nm; when the (C 11 H 26 N)2Cu2I4 material is a (C 11 H 26 N)2Cu2I4 nanocrystal, the emission peak is at 487 nm; When the (C 11 H 26 N)2Cu2I4 material is at 100 °C, it can emit warm white light under the excitation of 365 nm ultraviolet light; When the (C 11 H 26 N)2Cu2I4 material is a (C 11 H 26 N)2Cu2I4 single crystal, it is prepared by a preparation method including the following steps: (1) Weigh C 11 H 26 NI and CuI as raw materials according to a molar ratio of 1:1 to prepare C 11 H 26 NI and CuI. Then, add H3PO2 and C 11 H 26 NI and CuI into the organic solvent N,N-dimethylformamide (DMF), and obtain a precursor solution after ultrasonic treatment; wherein, the C 11 H 26 NI is ethyltri-n-propylammonium iodide; (2) Filter the precursor solution obtained in the step (1), take the filtrate and place it in a container, and let it stand to volatilize the solvent in the filtrate, so that the single crystal of (C 11 H 26 N)2Cu2I4 precipitates and grows; when the standing time reaches the preset time, take out the grown single crystal of (C 11 H 26 N)2Cu2I4; When the (C 11 H 26 N)2Cu2I4 material is (C 11 H 26 N)2Cu2I4 nanocrystals, it is prepared by a preparation method including the following steps: (1) Weigh C 11 H 26 NI and CuI to prepare raw material C in a molar ratio of 1:1 11 H 26 NI and CuI. Then, add H3PO2 and C 11 H 26 NI and CuI to the organic solvent N,N-dimethylformamide (DMF), and obtain a precursor solution after ultrasonic treatment; wherein, the C 11 H 26 NI is ethyltri-n-propylammonium iodide; (2) Inject the precursor solution obtained in the step (1) into an antisolvent system composed of toluene and oleic acid under stirring conditions, where the volume ratio of toluene to oleic acid is 10 to 15, and (C 11 H 26 N)2Cu2I4 nanocrystals can be precipitated.

2. The application according to claim 1, characterized in that, When the ambient temperature of the (C 11 H 26 N)2Cu2I4 material drops from 100 °C to room temperature, it can recover from emitting warm white light to emitting blue light under the excitation of 365 nm ultraviolet light.

3. The application according to claim 1, characterized in that Specifically, the thermochromic luminescent material is applied to fluorescence temperature measurement, thermal imaging or temperature sensing.

4. The application according to claim 1, wherein The (C 11 H 26 N)2Cu2I4 material is (C 11 H 26 N)2Cu2I4 single crystal, in the step (1), calculated by (C 11 H 26 N)2Cu2I4, the concentration of the precursor solution is 1.28 - 1.67 mol / L.

5. The application according to claim 1, wherein The (C 11 H 26 N)2Cu2I4 material is (C 11 H 26 N)2Cu2I4 nanocrystals, and calculated by (C 11 H 26 N)2Cu2I4, the concentration of the precursor solution is 0.49 to 0.97 mol / L.

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