A photochromic crystalline material, its preparation method and application

Abstract

The present invention provides a photochromic crystalline material, a preparation method thereof and an application thereof, belonging to the technical field of crystalline materials. The crystalline material has a chemical formula shown in Formula I: {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n Formula I. The photochromic crystalline material provided by the present invention has a selective recognition effect on lights of different wavelengths, can quickly and sensitively detect lights of different wavelengths and show color differences distinguishable by the naked eye. The color of the crystalline material changes with the change of the illumination time, and the fluorescence intensity can be regulated by the illumination time. The results of the examples show that the photochromic crystalline material provided by the present invention changes from colorless to pink, purple and blue respectively under the illumination of 320 nm, 340 nm and 360 nm. Due to the fast light response rate, obvious color change and short fading time of the photochromic crystalline material, it can be applied to the anti-counterfeiting field.

Description

Technical Field

[0001] The present invention relates to the technical field of crystalline materials, and particularly to a photochromic crystalline material, a preparation method thereof, and an application thereof. Background Art

[0002] Responsive color-changing materials undergo reversible color changes under external stimuli such as heat, light, pressure, and electricity. Photochromic materials have been proven to be the most common responsive materials and have potential applications in many fields, such as decoration, displays, memories, switches, photography, sensors, and other fields. Many existing photochromic materials are coordination polymers formed by self-assembly of viologen ligands and metal inorganic building units. However, they can only change from one color to another under the stimulation of different wavelengths of external light, and often fluorescence quenching occurs during the photochromic process, and the performance is relatively single. Summary of the Invention

[0003] The purpose of the present invention is to provide a photochromic crystalline material, a preparation method thereof, and an application thereof. The photochromic crystalline material provided by the present invention can display different colors after being irradiated with light of different wavelengths, so as to selectively identify light of different wavelengths.

[0004] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0005] The present invention provides a photochromic crystalline material having a chemical formula shown in Formula I:

[0006] {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n Formula I;

[0007] In the said Formula I, CPbpy is N-(2-carboxyethyl)-4,4'-bipyridinium cation, and n is the number of repeating units.

[0008] Preferably, the photochromic crystalline material belongs to the triclinic system, space group P-1, α = 77.727(4)°, β = 78.575(3)°, γ = 85.792(4)°, Z = 2,

[0009] The present invention provides a preparation method of the photochromic crystalline material according to the above technical solution, including:

[0010] Mixing N-(2-carboxyethyl)-4,4'-bipyridinium chloride, cadmium nitrate, water, and an organic solvent, and then carrying out a volatilization reaction to obtain the photochromic crystalline material.

[0011] Preferably, the molar ratio of N-(2-carboxyethyl)-4,4'-bipyridinium chloride to cadmium nitrate is 1:(1-3).

[0012] Preferably, the organic solvent includes N,N-dimethylformamide.

[0013] Preferably, the volume ratio of water to the organic solvent is 1:(0.5-1.5).

[0014] Preferably, the mass ratio of cadmium nitrate to the total mass of water and the organic solvent is 1:(77-81).

[0015] Preferably, the temperature of the evaporation reaction is 10-30 °C.

[0016] Preferably, the time of the evaporation reaction is 50-70 days.

[0017] The present invention also provides the application of the photochromic crystalline material described in the above technical solution or the photochromic crystalline material prepared according to the preparation method described in the above technical solution in the fields of detection, fluorescence regulation and anti-counterfeiting.

[0018] The present invention provides a photochromic crystalline material with the chemical formula shown in Formula I: {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n Formula I; in Formula I, CPbpy is N-(2-carboxyethyl)-4,4'-bipyridinium cation, and n is the number of repeating units. One repeating unit of the photochromic crystalline material provided by the present invention contains one Cd(II), two CPbpy ligands, one Cl, one nitrate ion and three free water molecules. Lights with different wavelengths have different energies. When irradiating this photochromic crystalline material, internal electron transfer occurs, which may cause a change in the valence state of cadmium ions, so that this photochromic crystalline material has a selective recognition effect on lights with different wavelengths, can quickly and sensitively detect lights with different wavelengths and show color differences distinguishable by the naked eye. The color of the crystalline material changes with the change of the illumination time, and the fluorescence intensity can be regulated by the illumination time. The results of the examples show that the photochromic crystalline material provided by the present invention changes from colorless to pink, purple and blue under illumination at 320 nm, 340 nm and 360 nm respectively, and the contrast of the fluorescence intensity before and after illumination is as high as 31 times. Description of the Drawings

[0019] Figure 1 It is the coordination environment diagram of the photochromic crystalline material in Example 1 of the present invention;

[0020] Figure 2 It is the PXRD spectrum of the photochromic crystalline material in Example 1 of the present invention measured by single crystal theoretical simulation and experiment;

[0021] Figure 3 This is the photoluminescence spectrum of the photochromic crystalline material of Example 1 of the present invention;

[0022] Figure 4 This is the photoluminescence lifetime spectrum of the photochromic crystalline material of Example 1 of the present invention;

[0023] Figure 5 This is the diagram showing that the photochromic crystalline material of Example 1 of the present invention displays different colors when detecting light of different wavelengths;

[0024] Figure 6 This is the diagram showing the change of the color of the photochromic crystalline material of Example 1 of the present invention with the illumination time;

[0025] Figure 7 This is the time-dependent photoluminescence spectrum of the photochromic crystalline material of Example 1 of the present invention;

[0026] Figure 8 This is the schematic diagram of the anti-counterfeiting application of the photochromic crystalline material of Example 1 of the present invention. Detailed implementation manners

[0027] The present invention provides a photochromic crystalline material having a chemical formula as shown in Formula I:

[0028] {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n Formula I;

[0029] In the said Formula I, CPbpy is N-(2-carboxyethyl)-4,4'-bipyridinium cation, and n is the number of repeating units.

[0030] In the present invention, the photochromic crystalline material belongs to the triclinic system, space group P-1; the unit cell parameters of the photochromic crystalline material are: α = 77.727(4)°, β = 78.575(3)°, γ = 85.792(4)°, Z = 2,

[0031] The present invention provides a preparation method of the photochromic crystalline material according to the above technical solution, including:

[0032] Mix N-(2-carboxyethyl)-4,4'-bipyridinium chloride, cadmium nitrate, water and an organic solvent, and then carry out a volatilization reaction to obtain the photochromic crystalline material.

[0033] Unless otherwise specified, the present invention has no special limitation on the sources of the various raw materials, and commercially available products or products prepared by conventional preparation methods well-known to those skilled in the art can be used.

[0034] In the present invention, the molar ratio of N-(2-carboxyethyl)-4,4'-bipyridinium chloride to cadmium nitrate is preferably 1:(1-3), more preferably 1:(1-2). By limiting the molar ratio of N-(2-carboxyethyl)-4,4'-bipyridinium chloride to cadmium nitrate within the above range, the present invention can enable the two to react fully and prevent the occurrence of excessive side reactions, thereby improving the purity, crystallinity and yield of the crystalline material. In the examples of the present invention, the preparation method of N-(2-carboxyethyl)-4,4'-bipyridinium chloride is preferably as follows: Weigh 4,4'-bipyridine (6.25 g, 40 mmol) and 3-chloropropionic acid (3.25 g, 30 mmol) respectively in 20 mL of DMF. After fully dissolving, transfer them to a 50 mL round-bottom flask, and stir the reaction at a constant temperature of 100 °C for 12 h. A light yellow precipitate is generated during the reaction. After the reaction is completed, let it cool naturally, filter and collect the precipitate, wash the precipitate with ether and perform suction filtration, and finally obtain N-(2-carboxyethyl)-4,4'-bipyridinium chloride through vacuum drying.

[0035] In the present invention, the organic solvent preferably includes N,N-dimethylformamide; the volume ratio of water to the organic solvent is preferably 1:(0.5-1.5), more preferably 1:1. In the present invention, water is both a solvent and a mineralizing agent, with high uniformity and good dispersibility. It can reduce the reaction temperature and dissolve the raw materials fully without agglomeration, thereby improving the crystallinity of the crystalline material after the reaction; the use of a mixed solvent is to adjust the solubility and reaction rate. The reactants are soluble in water, so water is added to dissolve the reactants fully and make the reaction system a homogeneous system. However, the evaporation rate of water is relatively fast. Therefore, an organic solvent is added to delay the solvent evaporation rate to ensure the normal progress of the reaction. By limiting the composition of the solvent and the ratio of each component within the above range, the present invention can enable the reaction to proceed fully and completely.

[0036] In the present invention, the mass ratio of cadmium nitrate to the total mass of water and the organic solvent is preferably 1:(77-81), more preferably 1:(78-80), and most preferably 1:79. By limiting the mass ratio of cadmium nitrate to the total mass of water and the organic solvent within the above range, the present invention can enable each raw material to be fully dissolved and the reaction to proceed fully.

[0037] The present invention has no special limitation on the mixing of N-(2-carboxyethyl)-4,4'-bipyridinium chloride, cadmium nitrate, water and the organic solvent, and the technical scheme of material mixing well-known to those skilled in the art can be adopted.

[0038] In the present invention, the temperature of the volatilization reaction is preferably 10 - 30 °C, more preferably 15 - 25 °C; the time of the volatilization reaction is preferably 50 - 70 days, more preferably 55 - 65 days. By limiting the temperature and time of the volatilization reaction within the above ranges, the present invention can enable the full reaction of each raw material, prevent the occurrence of excessive side reactions, and improve the purity, crystallinity and yield of the crystalline material. In the present invention, during the volatilization reaction, cadmium nitrate and N-(2-carboxyethyl)-4,4'-bipyridinium chloride undergo a coordination reaction to form {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n .

[0039] After the volatilization reaction is completed, the present invention preferably performs post-treatment on the volatilized product to obtain a photochromic crystalline material. In the present invention, the post-treatment preferably includes filtration and washing performed in sequence. The present invention has no special limitation on the operations of the filtration and washing, and the technical solutions of filtration and washing well-known to those skilled in the art can be adopted.

[0040] The present invention also provides the application of the photochromic crystalline material described in the above technical solution or the photochromic crystalline material prepared according to the preparation method described in the above technical solution in the fields of detection, fluorescence regulation and anti-counterfeiting.

[0041] The present invention has no special limitation on the application of the photochromic crystalline material in the fields of detection, fluorescence regulation and anti-counterfeiting, and the technical solutions of the application of the photochromic crystalline material in the fields of detection, fluorescence regulation and anti-counterfeiting well-known to those skilled in the art can be adopted.

[0042] In the present invention, the photochromic crystalline material shows different colors under the irradiation of light with different wavelengths, so it can be used to detect light sources with different wavelengths; the fluorescence intensity changes with the different illumination time, so it can be used for fluorescence regulation; the light response rate is fast, the color change is obvious, and the fading time is short, so it can be used for anti-counterfeiting.

[0043] Next, the technical solutions in the present invention will be described clearly and completely in conjunction with the examples in the present invention. Obviously, the described examples are only a part of the examples of the present invention, rather than all the examples. Based on the examples in the present invention, all other examples obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0044] Example 1

[0045] The photochromic crystalline material in this example has the chemical formula shown in Formula I: {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} nFormula I; in the formula I, CPbpy is N-(2-carboxyethyl)-4,4'-bipyridinium cation;

[0046] The preparation method is as follows: Mix water and N,N-dimethylformamide in a volume ratio of 1:1 to obtain a mixed solvent, and then mix N-(2-carboxyethyl)-4,4'-bipyridinium chloride, cadmium nitrate and the mixed solvent (the molar ratio of N-(2-carboxyethyl)-4,4'-bipyridinium chloride to cadmium nitrate is 1:2, and the mass ratio of cadmium nitrate to the mixed solvent is 1:79). Carry out a volatilization reaction at 20 °C for 60 days. After the reaction is completed, filter and wash to obtain the photochromic crystalline material.

[0047] The photochromic crystalline material prepared in Example 1 was scanned and tested on a Rigaku Pilatus CCD single crystal diffractometer. The parameters of the scanning test were as follows: Mo target, Kα radiation source (λ = 0.07107 nm), test temperature 293 K, and the structure was analyzed by Olex2.

[0048] The results of single crystal X-ray diffraction analysis show that:

[0049] The structural formula of the crystalline material is {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n , belonging to the triclinic system, P-1 space group, α = 77.727(4)°, β = 78.575(3)°, γ = 85.792(4)°, Z = 2,

[0050] The photochromic crystalline material {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} prepared in Example 1 n The coordination environment diagram is as Figure 1 shown. It can be seen from Figure 1 that the crystalline material prepared in Example 1 contains one Cd(II), two CPbpy ligands, one Cl, one nitrate and three free water molecules. Cd(II) is connected to one Cl, three O atoms and two N atoms from the CPbpy ligand.

[0051] The powder X-ray diffraction (PXRD) phase analysis of the photochromic crystalline material prepared in Example 1 after grinding was carried out on a Bruker D8 Advance X-ray diffractometer in Germany. The parameters of the scanning test were as follows: Cu target, Kα radiation source (λ = 0.154184 nm). The PXRD spectra of the photochromic crystalline material prepared in Example 1 obtained by single crystal data simulation and experiment are as Figure 2 shown. It can be seen from Figure 2It can be seen that the PXRD spectra of the photochromic crystalline material prepared in Example 1 obtained by single crystal data simulation and experimental measurement are highly consistent, proving that the samples prepared in Example 1 are all of high purity and high crystallinity.

[0052] Application Example 1

[0053] The photoluminescence performance of the photochromic crystalline material prepared in Example 1 was tested, and the specific steps are as follows:

[0054] The photochromic crystalline material prepared in Example 1 was ground evenly to obtain a sample to be tested. The photoluminescence performance of the sample to be tested was measured. Using the Xe lamp of Edinburgh FL920 40W, the light with a wavelength of 320 nm was used as the excitation light source to irradiate the sample to be tested, and the photoluminescence spectrum of the photochromic crystalline material prepared in Example 1 was obtained as Figure 3 shown. As can be seen from Figure 3 it, the photochromic crystalline material prepared in Example 1 can be excited by the light with a wavelength of 320 nm, and the position of the emission peak is at 485 nm.

[0055] The photoluminescence lifetime was measured, and the results are as Figure 4 shown. As can be seen from Figure 4 it, the photoluminescence lifetime of the {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n crystalline material is 6.17 ns, and the lifetime is at the ns level, indicating that the luminescence of this material is fluorescence emission.

[0056] Application Example 2

[0057] The photodetection performance of the photochromic crystalline material prepared in Example 1 for light of different wavelengths was tested, and the specific steps are as follows:

[0058] Using the Xe lamp of Edinburgh FL920 40W, the light with wavelengths of 320 nm, 340 nm, and 360 nm were respectively used to irradiate the sample. The crystal sample was ground evenly for the light irradiation test, and the results are as Figure 5 shown. As can be seen from Figure 5 it, the crystalline material changes from colorless to pink, purple, and blue under the light irradiation at 320 nm, 340 nm, and 360 nm respectively, indicating that this material has the ability to detect light of different wavelengths.

[0059] Application Example 3

[0060] The test on the change of the color of the photochromic crystalline material prepared in Example 1 with the change of the light irradiation time was carried out, and the specific steps are as follows:

[0061] The crystal powder sample was irradiated with a Xe lamp for the light irradiation test, and the results are as Figure 6 shown. As can be seen fromFigure 6 It can be seen that as the illumination time increases, the color of the photochromic crystalline material changes from colorless to blue, pink, and yellow in sequence, showing blue after 5 s, pink after 30 s, and yellow after 15 min.

[0062] Application Example 4

[0063] In-situ time-dependent photoluminescence test of the photochromic crystalline material prepared in Example 1 was carried out as follows:

[0064] Using an Edinburgh FL920 40W Xe lamp, light with a wavelength of 320 nm was used as the light source to irradiate the sample. The crystal sample was ground evenly for time-dependent photoluminescence spectrum test, and the results are as Figure 7 shown. Figure 7 In-situ time-dependent photoluminescence spectrum shows that for the crystalline material {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n as the illumination time increases, the fluorescence intensity gradually increases, indicating that the material has the ability of fluorescence regulation. The fluorescence intensities at 0, 20, 40, 60, 80, and 100 min are 1.12×10 4 , 8.54×10 4 , 2.38×10 5 , 3.03×10 5 , 3.47×10 5 .

[0065] Application Example 5

[0066] Anti-counterfeiting application of the photochromic crystalline material prepared in Example 1 was carried out as follows:

[0067] The crystalline material ground into powder was dispersed in ethanol, and ultrasonic treatment was carried out for 30 min to obtain a uniformly dispersed suspension. The suspension was dropped onto filter paper with a dropper and placed in a room-temperature environment away from light to dry until the surface of the filter paper was completely dry. A customized template was covered on the surface of the filter paper. After irradiation with a Xe lamp (300W, distance 10 cm) for 1 min, the pattern was clearly distinguishable ( Figure 8 ), and this material can be applied to anti-counterfeiting.

[0068] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A photochromic crystalline material having the chemical formula shown in Formula I: {[Cd(CPbpy)2Cl]·(NO3)(H2O)3} n Formula I; In the said Formula I, CPbpy is N-(2-carboxyethyl)-4,4'-bipyridinium cation, and n is the number of repeating units; The preparation method of the said photochromic crystalline material includes: Mix N-(2-carboxyethyl)-4,4'-bipyridinium chloride, cadmium nitrate, water and an organic solvent, and then carry out a volatilization reaction to obtain the photochromic crystalline material; The molar ratio of the said N-(2-carboxyethyl)-4,4'-bipyridinium chloride to cadmium nitrate is 1:(1-3); the said organic solvent includes N,N-dimethylformamide; the volume ratio of water to the organic solvent is 1:(0.5-1.5); the mass ratio of cadmium nitrate to the total mass of water and the organic solvent is 1:(77-81); the temperature of the said volatilization reaction is 10-30 °C; the time of the said volatilization reaction is 50-70 days.

2. The photochromic crystalline material according to claim 1, wherein The photochromic crystalline material belongs to the triclinic system, space group P-1, α = 77.727(4)°, β = 78.575(3)°, γ = 85.792(4)°, Z = 2, 3. The preparation method of the photochromic crystalline material according to claim 1 or 2, includes: Mix N-(2-carboxyethyl)-4,4'-bipyridinium chloride, cadmium nitrate, water and an organic solvent, and then carry out a volatilization reaction to obtain the photochromic crystalline material; The molar ratio of the said N-(2-carboxyethyl)-4,4'-bipyridinium chloride to cadmium nitrate is 1:(1-3); the said organic solvent includes N,N-dimethylformamide; the volume ratio of water to the organic solvent is 1:(0.5-1.5); the mass ratio of cadmium nitrate to the total mass of water and the organic solvent is 1:(77-81); the temperature of the said volatilization reaction is 10-30 °C; the time of the said volatilization reaction is 50-70 days.

4. The application of the photochromic crystalline material according to claim 1 or 2 in the fields of detection, fluorescence regulation or anti-counterfeiting.

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