MOF-based photo-thermal dual-response material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of color-changing materials, and particularly relates to an MOF-based photo-thermal dual-response material and a preparation method and application thereof.The chemical formula of the MOF-based photo-thermal dual-response material is 3-BP-Cd-MOF, the MOF-based photo-thermal dual-response material comprises an object 3-propargyl bromide and a subject Cd-MOF material, the Cd-MOF material is of a three-dimensional porous structure, and the 3-propargyl bromide is fixed in a one-dimensional pore channel of the Cd-MOF material through C = C-H... O hydrogen-bond interaction; adjacent 3-propargyl bromide molecules are connected to form a guest molecular chain through the action of a C-Br.... pi halogen bond. The system has thermochromism and photochromic performance, and has potential application value in the aspects of overtemperature indication, information encryption, anti-counterfeiting technology and intelligent temperature control materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of color-changing materials, and specifically relates to a MOF-based photothermal dual-response material and a preparation method and application thereof. Background Art

[0002] Color-changing materials have the property of reversibly switching between two stable states with different colors and electronic / molecular structures. This color change can be regulated by external stimuli, such as light, temperature, pH, redox, and pressure. Among various stimuli-responsive materials, photochromic and thermochromic materials have attracted great attention in the field of smart materials due to their potential applications in protection, decoration, display, storage, switching, photography, etc. Some common organic photochromic molecules (such as azobenzene, spiropyran and spirooxazine, diarylethenes and fulgide) and diarylethene coordination compounds achieve color changes through molecular structure isomerization, such as cis-trans or ring opening-closing. However, viologen compounds and viologen-based metal organic frameworks (MOFs) and some other composite systems cause their photochromism through electron transfer (ET).

[0003] So far, most photochromic compounds caused by isomerization or ET processes will only undergo thermochromic fading as the temperature increases. And those materials that have both photochromic and thermochromic properties are rare. If a material has both thermochromic and photochromic properties, it is expected to have a wider range of applications. For example, it is well known that sunlight helps humans use vitamin D to promote bone growth and helps plants to photosynthesize. But if exposed to sunlight for a long time, it may cause the body temperature of animals and plants to rise, leading to heat stroke or sunburn. This color-changing material with dual functions of thermochromism and photochromism will have potential application value in smart temperature control materials, which allow more sunlight to enter in a light-colored state, change color as the temperature rises, and issue an over-temperature indication at higher temperatures (such as 50°C), but such research has not yet been reported. Summary of the invention

[0004] The purpose of the present invention is to provide a MOF-based photothermal dual-response material and its preparation method and application, so as to overcome the shortcomings of the prior art and construct a new host-guest system 3-BP@Cd-MOF using Cd-MOF and 3-bromopropyne. The system has dual color-changing properties of thermochromism and photofading, and has potential application value in over-temperature indication, information encryption, anti-counterfeiting technology and intelligent temperature control materials.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] In the first aspect, the present invention provides a MOF-based photothermal dual-response material, named 3-BP@Cd-MOF, including a guest 3-bromopropyne and a host Cd-MOF material. The Cd-MOF material is a three-dimensional porous structure, and the 3-bromopropyne is fixed in the one-dimensional channel of the Cd-MOF material through C≡C–H···O hydrogen bonding; adjacent 3-bromopropyne molecules are connected into a guest molecule chain through C–Br···π halogen bonding.

[0007] The Cd-MOF material is ([CdL2(ClO4)2]·2CH2Cl2), where L is 4-amino-3,5-di(4-pyridine-3-phenyl)-1,2,4-triazole), and a stable Cd-MOF with nanopores ([CdL2(ClO4)2]·H2O) is obtained by losing a guest dichloromethane molecule at 150°C.

[0008] The inventive concept adopted by the present invention is: Cd-MOF is a highly stable MOF material with a three-dimensional porous structure formed by Cd(ClO4)2 and 4-amino-3,5-bis(4-pyridyl-3-phenyl)-1,2,4-triazole (the preparation method can refer to the synthesis and photocatalytic hydrogen production of photosensitive Cd-MOF and fluorescence recognition research of Pt-based supramolecules [D], Han Congcong, Shandong Normal University, 2022 or the self-assembly chemistry and property research based on five-membered heterocyclic bridged organic ligands and fluorescent organic ligands [D], Liu Qikui, Shandong Normal University, 2010) and can adsorb propyne molecules in its one-dimensional pores through host-guest C≡C–H···O hydrogen bond interactions, where the close contact between CH3 and the adjacent alkynyl groups is determined to be

[0009] The present invention uses 3-bromopropyne (3-BP) instead of propyne to introduce a guest molecular chain that can be connected by halogen bonds (C–Br···π) into the Cd-MOF pores. Bromine atoms easily generate free radicals under light stimulation. More importantly, Cd-MOF produces a guest-promoted long-lived charge separation state and characteristic absorption covering the visible light region through a thermally induced ET process. Therefore, in the present invention, a new host-guest system 3-BP@Cd-MOF is constructed using Cd-MOF and 3-bromopropyne. The system has dual color-changing properties of thermochromism and photofading, and has potential application value in over-temperature indication, information encryption, anti-counterfeiting technology and intelligent temperature control materials.

[0010] In some other embodiments, the Cd-MOF material is [CdL2(ClO4)2]·H2O, where L is 4-amino-3,5-di(4-pyridine-3-phenyl)-1,2,4-triazole).

[0011] In some other embodiments, the MOF-based photothermal dual-response material has the following response characteristics:

[0012] Under heating conditions of 45-55℃, the thermochromic response changes from colorless to blue, and the response time is 20min-8h;

[0013] Under cold light irradiation, the photofading response fades from blue to colorless, and the response time is 2-3 minutes;

[0014] Under heating conditions of 90-110℃, it responds to thermochromic changes from blue or colorless to brown, and the response time is 0.5-1h;

[0015] Under cold light irradiation, the color will fade from brown to orange and cannot be restored to blue or colorless. The response time is 12-24 hours.

[0016] Under heating conditions of 90-110℃, it responds thermochromically, changing from orange to brown, and the response time is 0.5-1h.

[0017] In some other embodiments, the 3-BP@Cd-MOF can maintain a blue color stably for more than one month under sealed light-proof conditions.

[0018] In a second aspect, the present invention provides a method for preparing the MOF-based photothermal dual-responsive material described in the first aspect, wherein the activated Cd-MOF crystal and 3-bromopropyne are sealed and heated to obtain a blue or brown MOF-based photothermal dual-responsive material.

[0019] In some other embodiments, when the heating temperature is 45-55° C. and the heating time is 1-10 h, a blue MOF-based photothermal dual-response material is obtained;

[0020] When the heating temperature is 90-110°C and the heating time is 0.5-1h, a brown MOF-based photothermal dual-response material is obtained.

[0021] In some other embodiments, the activation method of the Cd-MOF crystals is to activate the colorless Cd-MOF crystals at 100-150° C. for 2-5 hours.

[0022] In a third aspect, the present invention provides applications of the MOF-based photothermal dual-response material described in the first aspect in over-temperature indication, information encryption, anti-counterfeiting technology, and intelligent temperature control materials.

[0023] In a fourth aspect, the present invention provides a 3-BP@Cd-MOF doped polyvinylidene fluoride film, comprising a matrix material and a filler material uniformly dispersed in the matrix material;

[0024] The matrix material is polyvinylidene fluoride; the filling material is the MOF-based photothermal dual-response smart material described in the first aspect.

[0025] In some other embodiments, the 3-BP@Cd-MOF doped PVDF film has the following response characteristics:

[0026] Under heating conditions of 45-55℃, it responds to thermochromism and turns to purple, and the response time is 5-8min;

[0027] Under cold light irradiation, the photofading response fades from purple to colorless, and the response time is 2-3 minutes;

[0028] Under heating conditions of 45-55℃, the thermochromic response changes from colorless to purple, and the response time is 5-8min;

[0029] Under heating conditions of 90-110℃, the thermochromic response changes from purple to brown, and the response time is 0.5-1h;

[0030] Under cold light irradiation, the photofading response fades from brown to orange, and the response time is 12-24h;

[0031] Under heating conditions of 90-110℃, it responds thermochromically, changing from orange to brown, and the response time is 0.5-1h.

[0032] Beneficial effects of the present invention:

[0033] (1) The present invention creatively constructs a new host-guest system 3-BP@Cd-MOF by combining Cd-MOF and 3-bromopropyne. The system has dual color-changing properties of thermochromism and photochromism, and has potential application value in over-temperature indication, information encryption, anti-counterfeiting technology and intelligent temperature control materials.

[0034] (2) The host-guest system 3-BP@Cd-MOF in the present invention exhibits very strong visible light absorption in the range of 400-800 nm. The 3-BP@Cd-MOF-Blue crystals are kept in airtight and light-free conditions and can be stable for at least one month.

[0035] (3) The preparation method of the host-guest system 3-BP@Cd-MOF of the present invention is simple, easy, economical and non-toxic. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1The color response of Cd-MOF and 3-BP@Cd-MOF crystals under light and heat stimulation in the embodiment of the present invention;

[0038] Figure 2 The performance characterization diagrams of solid-state 3-BP@Cd-MOF-Blue, 3-BP@Cd-MOF-Colorless, 3-BP@Cd-MOF-Brown, 3-BP@Cd-MOF-Light Orange and Cd-MOF in the embodiments of the present invention are shown in Figure 1, where (a) is the Fourier transform infrared spectrum, (b) is the UV-visible spectrum, (c) is the EPR spectrum, and (d) is the fluorescence emission spectrum (λ ex =315 nm), (e)-(h) are X-ray photoelectron spectroscopy (XPS);

[0039] Figure 3 The crystal structure, hydrogen bonding and C–Br…π halogen bonding diagrams of the 3-BP@Cd-MOF host-guest system in the embodiment of the present invention, where (A) is the crystal structure and (B) is the hydrogen bonding C≡C–H…O(ClO4 - )(pink dashed line), N(amino)–H...Br(3-BP)(blue-green dashed line), Cpyridyl–H...O(ClO4 - )(green dashed line) and N(amino)–H…O(ClO4 - )(orange dashed line), (C) is the halogen bond effect C–Br…π;

[0040] Figure 4 This is a photograph of the color response of the 3-BP@Cd-MOF-doped PVDF film under the stimulation of heat and light in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The reagents and materials used in the present invention are all common commercial products and can be purchased in the market.

[0042] The present invention will be further described below in conjunction with embodiments:

[0043] Example 1

[0044] (1) Construction and color response of 3-BP@Cd-MOF materials

[0045] First, the colorless Cd-MOF crystals were activated at 403K for 3 hours, and then the activated Cd-MOF crystals and 3-bromopropyne (3-BP) were sealed in a vial and placed in an oven (50°C). After about 8 hours, the color turned blue to obtain blue crystals (3-BP@Cd-MOF-Blue). Figure 1As shown. When 3-BP@Cd-MOF-Blue crystals were exposed to cold light (5W, the wavelength of the cold light source was mainly concentrated in the visible light region, that is, from about 400 nanometers (blue light) to 700 nanometers (red light)), obvious photochromic phenomenon occurred, and the blue color quickly faded to almost colorless within 2-3 minutes, obtaining colorless crystals (3-BP@Cd-MOF-Colorless). If the 3-BP@Cd-MOF-Blue crystals are kept in airtight and lightless conditions, the 3-BP@Cd-MOF-Blue crystals can be stable for at least one month. When the nearly colorless 3-BP@Cd-MOF-Colorless crystals were heated at 50°C for 20 minutes, the blue color was restored. Further experiments showed that when heated at a higher temperature (100°C, about 1 hour), both 3-BP@Cd-MOF-Blue crystals and 3-BP@Cd-MOF-Colorless crystals turned brown, obtaining brown crystals (3-BP@Cd-MOF-Brown). When 3-BP@Cd-MOF-Brown crystals are exposed to cold light (5W), they can only slowly fade to light orange, that is, light orange crystals (3-BP@Cd-MOF-Light Orange) and cannot be restored to blue or colorless; orange crystals (3-BP@Cd-MOF-Light Orange) turn brown when heated at 100°C for about 1 hour. The study found that when 3-BP@Cd-MOF-Blue crystals and 3-BP@Cd-MOF-Colorless crystals are placed in a 3-BP atmosphere, the effect of turning brown is more significant.

[0046] (2) Structural characterization of 3-BP@Cd-MOF color-changing materials

[0047] The performance of 3-BP@Cd-MOF-Blue, 3-BP@Cd-MOF-Colorless, 3-BP@Cd-MOF-Brown, 3-BP@Cd-MOF-Light Orange and Cd-MOF were characterized. Figure 2 As shown, (a) is the Fourier transform infrared spectrum, (b) is the UV-visible spectrum, (c) is the EPR spectrum, and (d) is the fluorescence emission spectrum (λ ex =315nm), (e)-(h) are X-ray photoelectron spectroscopy (XPS). Fourier transform infrared (FT-IR) spectroscopy analysis ( Figure 2 a) Analysis shows that after Cd-MOF captures 3-BP, the Cd-MOF-induced ions at about 3258 (C–H) and 2125 (C≡C) cm -1 The characteristic absorption peak is located at 1606cm -1 The C=N stretching vibration absorption peaks are split into 1636 and 1606 cm-1 The two peaks reflect the strong host-guest interaction and its effect on the ligand heterocycle.

[0048] Solid-state UV-Vis absorption spectroscopy ( Figure 2 b) shows that compared with Cd-MOF, the blue 3-BP@Cd-MOF-Blue exhibits visible light absorption with maximum absorption at 580nm and 625nm, and the brown 3-BP@Cd-MOF-Brown exhibits very strong visible light absorption in the range of 400-800nm. After irradiation with cold light (5W), both blue and brown crystalline materials fade to colorless and light orange. Among them, the colorless 3-BP@Cd-MOF-Colorless shows very weak absorption near 620nm, while the light orange 3-BP@Cd-MOF-Light shows strong absorption in the range of 350-600nm, with a maximum absorption of around 400nm. The light absorption characteristics of all host-guest systems are consistent with their color response.

[0049] Electron paramagnetic resonance (EPR) spectroscopy ( Figure 2 c) The study showed that no free radical signal was observed for the Cd-MOF sample, while the blue 3-BP@Cd-MOF-Blue showed a weak free radical signal at g=2.0050. As the color deepened, the brown 3-BP@Cd-MOF-Brown showed a strong free radical signal. Such an EPR signal can last for at least one month under sealed conditions and in the dark. However, when the color changes from blue to colorless and from brown to light orange after cold light irradiation, this EPR signal will also weaken accordingly. These research results show that 3-BP@Cd-MOF generates free radicals on the MOF framework by heating, and new free radicals are generated after cold light irradiation, partially quenching the original host free radicals.

[0050] Solid-state fluorescence emission spectroscopy ( Figure 2 d) The study shows that the fluorescence emission of blue and brown 3-BP@Cd-MOF crystal materials is greatly quenched, indicating the generation of free radicals in the main framework. The fluorescence emission of colorless and light orange crystals is restored to varying degrees, indicating that the newly generated free radicals partially quench the original free radicals and restore the fluorescence emission. This is consistent with the results of the EPR study.

[0051] In order to gain a deeper understanding of the changes in the valence state of bromine before and after heating and light irradiation, the color-changing materials were tested by X-ray photoelectron spectroscopy (XPS). In 3-BP@Cd-MOF-Blue and 3-BP@Cd-MOF-Brown, the Br3d binding energy peaks are located at 68.44, 67.49 eV and 67.81, 66.86 eV, respectively, corresponding to the CH2-Br( Figure 2 e-2f). The shift of the Br3d peak to lower binding energy in the brown system is also attributed to the increase in electron cloud density on the skeleton. 3 / 2 and Br3d 5 / 2 The peaks shifted toward higher binding energies in both photobleaching systems, indicating an overall decrease in the electron cloud density on the guest molecule. In addition, 3-BP@Cd-MOF-Colorless and 3-BP@Cd-MOF-Light Orange had two obvious satellite peaks at 70.43 and 69.48 eV and 70.19 and 69.14 eV, respectively. This result indicates that the valence state of some Br elements in the photobleaching system becomes higher, indicating the generation of guest Br radicals after light-induced fading. This result is very consistent with the results of EPR and solid-state fluorescence emission experiments.

[0052] (3) Crystal structure analysis and mechanism

[0053] In order to elucidate the mechanism of thermal-induced discoloration and light-induced fading of host-guest materials, single crystal X-ray diffraction analysis was performed on four new host-guest MOFs, namely 3-BP@Cd-MOF-Blue, 3-BP@Cd-MOF-Colorless, 3-BP@Cd-MOF-Brown and 3-BP@Cd-MOF-Light Orange. Figure 3 A). Single crystal structure analysis shows that all 3-BP@Cd-MOF host-guest systems have the same P41212 or P43212 space group and tetragonal system as Cd-MOF. Specifically: 3-BP@Cd-MOF-Blue is P41212V: a: b: c: 3-BP@Cd-MOF-Colorless is P43212,V: a: b: ,c: 3-BP@Cd-MOF-Brown is P43212, V: a: b: c: 3-BP@Cd-MOF-Light Orange is P43212, V: a: b: c:

[0054] like Figure 3 As shown in B, 3-BP molecules pass through C≡C–H…O(ClO4- ) Hydrogen bonding interactions Fixed in the 1D pores of the skeleton. There are two arrangement directions of 3-BP guest molecules in the 1D pores. Among them, the arrangement direction of 3-BP guest molecules that affects the photothermal dual response characteristics is: there is an N–H…Br hydrogen bond interaction between the propargyl Br and the amino group of the ligand For the blue, colorless, brown, and light orange host–guest complexes, the short contacts between Br atoms and alkynyl groups in adjacent guest molecules were determined to be 2.8197, 2.8164, 2.9197, and (Based on H2CC≡C…Br distance), the C–Br…C bond angle is 174-175° close to 180°, and it can be considered that there is a C–Br…π halogen bond between the guest molecules ( Figure 3 C).

[0055] Based on the above experimental results, it is inferred that the thermochromic and photofading mechanisms of the 3-BP@Cd-MOF host-guest system should be: under heating conditions, ClO4 - The anion undergoes electron transfer to the organic linker of the framework and generates a host radical on the MOF framework, C≡C–H…O(ClO4 - ), C pyridyl –H…O(ClO4 - ) and N(amino)–H…O(ClO4 - )Hydrogen bonding interactions promote the occurrence of this electron transfer. As the temperature increases, more host radicals are generated on the framework, as evidenced by the greatly enhanced EPR signal of the brown system. Under light conditions, the guest 3-BP molecules connected by halogen bonds are excited to produce Br radicals, which interact with the MOF framework through N–H…Br hydrogen bonds and partially quench the host radicals. The abundant hydrogen bonding and halogen bonding in the 3-BP@Cd-MOF system leads to its unique light- and heat-induced dual-functional color-changing properties.

[0056] Preparation of dual-responsive PVDF films

[0057] (4) Application

[0058] 3-BP@Cd-MOF-Blue doped PVDF film was prepared using polyvinylidene fluoride (PVDF) as the matrix. The film showed purple after drying at 50°C. After irradiation with a cold light source (5W), the purple film can quickly turn into a colorless film, and the colorless film can be restored to a purple film by heating at 50°C. However, if the purple film is heated at 100°C for 1 hour, it will show a darker color - brown. This color change with temperature property makes it show application value in over-temperature warning. The brown film can slowly fade to light orange under cold light irradiation, and can return to brown after heating treatment. This unique thermochromic and photofading properties make 3-BP@Cd-MOF crystal materials have potential application value in information encryption and anti-counterfeiting technology.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that 3-bromopropyne (3-BP) is replaced by propyne or 3-chloropropyne, and the other preparation methods are the same as those in Example 1. The study found that there is no color change in the Cd-MOF crystal adsorbed with propyne. The Cd-MOF crystal adsorbed with chloropropyne has no obvious color change under the same adsorption conditions as Example 1, that is, it does not have the photothermal dual response characteristics.

[0061] Comparative Example 2

[0062] Different from Example 1, the Cd-MOF crystal is replaced with a Cu-MOF crystal, and the other preparation methods are the same as those in Example 1. Among them, the preparation method of Cu-MOF crystal (molecular formula is ([CuL2(ClO4)2]·H2O), L is 4-amino-3,5-di(4-pyridine-3-phenyl)-1,2,4-triazole) is different from the preparation method of Cd-MOF crystal in that Cu(ClO4)2 is used to replace Cd(ClO4)2, and the other preparation methods are the same as Cd-MOF crystal. The study found that the 3-bromopropyne or 3-chloropropyne crystal material after Cu-MOF adsorption has no color change caused by light and heat. It may be that the weak interaction between Cu-MOF and propyne or 3-chloropropyne is not conducive to the main free radicals that respond to electron transfer, resulting in discoloration.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A MOF-based photothermal dual-response material, characterized in that: The invention is named 3-BP@Cd-MOF, and includes a guest 3-bromopropyne and a main Cd-MOF material. The Cd-MOF material is a three-dimensional porous structure. The 3-bromopropyne is fixed in the one-dimensional pores of the Cd-MOF material through C≡C–H···O hydrogen bonds; adjacent 3-bromopropyne molecules are connected into a guest molecule chain through C–Br···π halogen bonds.

2. The MOF-based photothermal dual-response material according to claim 1, characterized in that: The Cd-MOF material is [CdL2(ClO4)2]·H2O, where L is 4-amino-3,5-di(4-pyridine-3-phenyl)-1,2,4-triazole).

3. The MOF-based photothermal dual-response material according to claim 1, characterized in that: The MOF-based photothermal dual-response material has the following response characteristics: Under heating conditions of 45-55℃, the thermochromic response changes from colorless to blue, and the response time is 20min-8h; Under cold light irradiation, the photofading response fades from blue to colorless, and the response time is 2-3 minutes; Under heating conditions of 90-110℃, it responds to thermochromic changes from blue or colorless to brown, and the response time is 0.5-1h; Under cold light irradiation, the color will fade from brown to orange and cannot be restored to blue or colorless. The response time is 12-24 hours. Under heating conditions of 90-110℃, it responds thermochromically, changing from orange to brown, and the response time is 0.5-1h.

4. The MOF-based photothermal dual-response material according to claim 1, characterized in that: The 3-BP@Cd-MOF can maintain a blue color stably for more than one month under sealed and light-proof conditions.

5. A method for preparing the MOF-based photothermal dual-response material according to any one of claims 1 to 4, characterized in that: After the activated Cd-MOF crystals and 3-bromopropyne are sealed and heated, a blue or brown MOF-based photothermal dual-responsive material is obtained.

6. The method for preparing the MOF-based photothermal dual-response material according to claim 5, characterized in that: When the heating temperature is 45-55°C and the heating time is 1-10h, a blue MOF-based photothermal dual-response material is obtained; When the heating temperature is 90-110°C and the heating time is 0.5-1h, a brown MOF-based photothermal dual-response material is obtained.

7. The method for preparing the MOF-based photothermal dual-response material according to claim 5, characterized in that: The activation method of the Cd-MOF crystal is to activate the colorless Cd-MOF crystal at 100-150° C. for 2-5 hours.

8. An application of the MOF-based photothermal dual-response material according to any one of claims 1 to 4 in over-temperature indication, information encryption, anti-counterfeiting technology and intelligent temperature control materials.

9. A 3-BP@Cd-MOF doped polyvinylidene fluoride film, characterized in that: comprising a matrix material and a filler material uniformly dispersed in the matrix material; The matrix material is polyvinylidene fluoride; the filling material is the MOF-based photothermal dual-response smart material according to any one of claims 1 to 4.

10. The 3-BP@Cd-MOF doped PVDF film according to claim 9, characterized in that: The 3-BP@Cd-MOF doped PVDF film has the following response characteristics: Under heating conditions of 45-55℃, it responds to thermochromism and turns to purple, and the response time is 5-8min; Under cold light irradiation, the photofading response fades from purple to colorless, and the response time is 2-3 minutes; Under heating conditions of 45-55℃, the thermochromic response changes from colorless to purple, and the response time is 5-8min; Under heating conditions of 90-110℃, the thermochromic response changes from purple to brown, and the response time is 0.5-1h; Under cold light irradiation, the photofading response fades from brown to orange, and the response time is 12-24h; Under heating conditions of 90-110℃, it responds thermochromically, changing from orange to brown, and the response time is 0.5-1h.

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