Preparation and application of salicylaldehyde Schiff base solid-state dual-mode optical switch based on full visible light control

Abstract

The present invention discloses a preparation and application of a salicylaldehyde Schiff base solid-state dual-mode optical switch based on full visible light regulation, wherein the molecular formula is as shown in Formula I, wherein the salicylaldehyde Schiff base provides the fluorescence properties and light response potential of the material, and the introduction of a large-volume 1,8-naphthalene diimide structure at the para position of its hydroxyl group can weaken the close packing of molecules in the solid state, increase the intermolecular spacing, and facilitate the photoisomerization behavior of the molecules, thereby making the rapid light response in the solid state possible. The salicylaldehyde Schiff base provided by the present invention not only shows a fast and reversible response, but also shows a significant change in the dual-mode of its own reflection color and fluorescence color, and the "on"-"off" process of this type of optical switch molecule can be regulated by two wavelengths of visible light, which greatly reduces the damage to the environment and personnel. Therefore, the material has a good application prospect in the fields of new generation optical switches, reversible erasing of optical information and anti-counterfeiting, information encryption, etc.

Description

Technical Field

[0001] This article involves the preparation and application of salicylaldehyde Schiff base solid-state dual-mode optical switch based on full visible light regulation, which belongs to the technical field of organic solid-state optical switch materials. Background Art

[0002] Photoswitch molecules are a class of molecules whose structure or properties can undergo reversible changes under light irradiation. They have very important applications in the fields of materials science and optoelectronics. These molecules usually exhibit two or more different electronic states or conformations, which can transform into each other under external light stimulation, thereby achieving controllable functional changes. Compared with other stimulation methods, light stimulation response has the advantages of precision, non-contact, pollution-free and remote operation, which makes photoswitch molecules have broad application potential in information storage, transmission, processing, biomedical imaging, drug delivery and catalysis.

[0003] Commonly used photoswitch molecules can be roughly divided into two categories, one is based on the cis-trans isomerism of double bonds (such as azo, olefins, etc.), and the other is based on the switch ring of molecules (such as spiropyran, diarylethenes, etc.). With the iteration and development of technology, people's pursuit of photoswitch materials is no longer limited to the mutual switching between two states in a single mode. The realization of multiple modes of coexistence of photoswitch (such as fluorescence mode and self-reflection color mode) has become a new development direction. The hydroxyl group of salicylaldehyde Schiff base derivatives can form an intramolecular hydrogen bond with the nitrogen atom of Schiff base, which effectively increases the conjugated plane of the molecule and has the property of aggregation induced fluorescence emission (AIE). When it is excited, the hydrogen atom on the hydroxyl group in the enol structure can be transferred to the nitrogen atom of Schiff base through the intramolecular proton, thereby converting the enol structure to the keto structure, and an excited state intramolecular proton transfer process occurs. Compared with the original structure, the fluorescence emission wavelength of the keto structure is red-shifted, which can effectively avoid overlap with the excitation light source and has better anti-interference ability; at the same time, the keto structure can further undergo cis-trans isomerization, resulting in further changes in the fluorescence color and its own color, showing great potential in the field of multi-fluorescence wavelength emission and photochromism.

[0004] Although many dual-mode optical switch materials have been developed, most of these materials have photoresponsive properties only in solution state, and the close packing of molecules in the solid state greatly hinders their free movement. This will cause many fluorescent materials to produce aggregation-induced quenching in the solid state, which is an important problem that solid-state dual-mode optical switch molecules need to overcome. In addition, most optical switch materials require ultraviolet light to achieve stimulus response, which not only has the disadvantages of high energy consumption and large damage (photoside reactions), resulting in impaired stability of optical switch molecules (accumulation of byproducts, decreased reversibility of photoisomerization), but also long-term use will cause damage to the environment and personnel, greatly limiting its practical application. Therefore, how to rationally design the molecular structure to achieve optical switch molecules with multiple characteristics such as fast visible light response in the solid state, dual-mode optical switching and aggregation-induced fluorescence emission is still a huge challenge facing this field. Summary of the invention

[0005] Technical problem: In order to solve the above problems, the present invention provides a method for preparing a salicylaldehyde Schiff base solid-state dual-mode optical switch based on full visible light regulation. This optical switch molecule can not only realize rapid reversible conversion of two states in the solid state, with fast response speed and good reversibility, but also can simultaneously realize dual-mode color changes of the material's own color and fluorescent color.

[0006] The second object of the present invention is to provide a fast and reversible method for erasing optical information, which realizes real-time writing and erasing of optical information through light regulation of appropriate wavelength.

[0007] The third object of the present invention is to provide an information encryption and anti-counterfeiting method based on the optical switch material, which achieves information encryption and anti-counterfeiting effects by giving multi-channel fluorescent coding symbols with different colors.

[0008] Technical solution: A salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation has a molecular structure shown in Formula I:

[0009]

[0010] The optical switch molecule has a natural light reflection mode and a fluorescence mode under ultraviolet light; in the solid state, its own color and fluorescence color red-shift as the light irradiation time increases; the forward "on" and reverse "off" processes of the optical switch can be achieved by irradiation with two visible light sources of different wavelengths.

[0011] The wavelength of one light source used by the optical switch molecule is any wavelength between 254nm and 480nm or between 600nm and 750nm, and the wavelength of the other light source is any wavelength between 490nm and 580nm; the irradiation time of the light source of the optical switch molecule is 0 to 60s.

[0012] A method for preparing the salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation, comprising the following steps:

[0013] 1) Preparation of intermediate NDI-P:

[0014] The reaction equation is as follows:

[0015]

[0016] 2) Preparation of intermediate NDI-PA:

[0017] The reaction equation is as follows:

[0018]

[0019] 3) Preparation of photoswitch molecule NDI-PI:

[0020] The reaction equation is as follows:

[0021]

[0022] Step 1) the molar ratio of 1,8-naphthalene dicarboxylic anhydride NTCDA, para-substituted amine AP, and anhydrous DMF is 1:1:80-120; Step 2) the molar ratio of intermediate NDI-P, urotropine HMTA, and TFA is 1:1-5:50-100; Step 3) the molar ratio of intermediate NDI-PA, amine, and anhydrous ethanol is 1:1-2:80-120.

[0023] The application of the salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation in the field of optical information erasure.

[0024] The application comprises the following steps:

[0025] 1) Material preparation: Spread the dry solid powder of the switch molecule on any flat solid substrate surface at room temperature;

[0026] 2) Writing of optical information: Use a low-power handheld point light source with a suitable wavelength to write optical information on the powder. At this time, the optical information is directly retained on the surface of the material. The color of the powder itself and the fluorescent color after writing are orange, and the color of the unwritten powder is yellow, and the fluorescent color is green or yellow;

[0027] 3) Optical information erasure: Use the first wavelength of light to irradiate the powder for a certain period of time. At this time, the surface color and fluorescent color of the powder itself are both orange, and no information or pattern remains;

[0028] 4) Reverse writing of optical information: Switch to the second wavelength low-power handheld point light source to reversely write optical information on the powder. At this time, the optical information is directly retained on the surface of the material. The reflected color of the powder after writing is yellow, and the fluorescent color is green or yellow. The reflected and fluorescent colors of the unwritten powder are both orange.

[0029] 5) Optical information reverse erasure: Use the second wavelength light to irradiate for a certain period of time to make all the powders return to the initial state. At this time, the reflective color of the powder surface is yellow, and the fluorescent color is green or orange. No information or pattern remains.

[0030] The application of the salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation in the field of information encryption and anti-counterfeiting.

[0031] Beneficial effects:

[0032] The optical switch molecule of the present invention comprises salicylaldehyde Schiff base and 1,8-naphthalene diimide group, the former endows the material with AIE property and photoresponse potential of enol and keto isomers, the latter can not only weaken the stacking effect of molecules in the solid state, increase the free volume, and facilitate the isomerization of molecules in the solid state, making fast photoresponse possible, while the overlap of the absorption wavelength of the naphthalene diimide fluorophore and the keto isomer can cleverly realize energy transfer, providing the possibility of generating multiple fluorescence emissions. The optical switch prepared by the present invention can realize reversible photochromism in solid-state dual mode, has the advantages of good fatigue resistance, stable properties, high sensitivity, fast response speed, full visible light wavelength response, etc., and has good application prospects in the field of solid-state optical switch materials.

[0033] The present invention also discloses a method for instantaneous optical information erasing based on the optical switch material, which utilizes the wide wavelength responsiveness and excellent fatigue resistance of the optical switch molecules to realize the loading and erasing of optical information by switching to light signals of different wavelengths. Compared with other technologies, the present invention has fast information writing speed, high sensitivity, good contrast, and reverse writing. At the same time, the damage of ultraviolet rays to the environment and personnel can be greatly reduced through the regulation of visible light cycles, and has good potential for instantaneous optical information erasing.

[0034] The present invention also discloses an application in the encryption and anti-counterfeiting of optical information. By assigning different coding symbols to the multi-channel fluorescent colors of optical switch molecules, different information can be displayed conveniently and quickly to achieve encryption and anti-counterfeiting. Compared with traditional binary coding, the molecular display coding of the present invention has the advantages of simple operation, high difficulty in deciphering, and the ability to achieve read-and-burn, etc., and has high application value in the field of information encryption and anti-counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1This is a graph showing the intensity changes of the diffuse reflectance spectrum of the solid powder of the optical switch molecule NDI-PI-1 at 489 nm when irradiated with light of different wavelengths for the same time in Example 2.

[0036] Figure 2 The diffuse reflectance spectra of the solid powder of the optical switch molecule NDI-PI-1 in Example 3 under irradiation with light of 405 nm wavelength for different time periods.

[0037] Figure 3 The diffuse reflectance spectra of the solid powder of the optical switch molecule NDI-PI-1 in Example 3 under 520 nm wavelength light irradiation for different time periods.

[0038] Figure 4 This is a cycle diagram of the ultraviolet-visible diffuse reflectance spectrum of the solid powder of the optical switch molecule NDI-PI-1 in Example 3 at 489 nm under alternate irradiation with light of 405 nm and 520 nm.

[0039] Figure 5 The fluorescence spectra of the solid powder of the optical switch molecule NDI-PI-1 in Example 3 under irradiation with light of 405 nm wavelength for different time periods.

[0040] Figure 6 This is the application of the optical switch molecule NDI-PI-1 in Example 4 in the reversible erasing of transient optical information.

[0041] Figure 7 This is the application of the optical switch molecule NDI-PI-1 in Example 5 in information encryption and anti-counterfeiting.

[0042] Figure 8 The UV-visible diffuse reflectance spectrum and fluorescence spectrum of the solid powder of the optical switch molecule NDI-PI-1 in Example 3 at 489 nm under alternate irradiation with light of 405 nm and 520 nm. DETAILED DESCRIPTION

[0043] In order to better understand the content of the present invention, the present invention is further described in combination with specific embodiments, including the synthesis and application examples of optical switch molecules. The embodiments are only for illustration and not for limitation. The actual implementation method includes but is not limited to the following embodiments. Other embodiments obtained by those skilled in the art without making creative changes also belong to the protection scope of the present invention.

[0044] A salicylaldehyde Schiff base solid-state dual-mode optical switch molecule was designed and synthesized. The molecular structure is as follows:

[0045]

[0046] The present invention discloses a method for preparing a salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation, comprising the following steps:

[0047] 1) Preparation of intermediate NDI-P:

[0048] Add 1,8-naphthalene dicarboxylic anhydride NTCDA, 4-substituted phenol AP and anhydrous DMF into a round-bottom flask and stir overnight at 80°C. After the reaction is completed, cool to room temperature, add deionized water to precipitate, and filter, wash and dry to obtain a white powder, which is the intermediate NDI-P.

[0049] 2) Preparation of intermediate NDI-PA:

[0050] The intermediate NDI-P, urotropine HTMA and TFA were added to a round-bottom flask, refluxed and stirred for 8 hours under nitrogen protection, 4M HCl was added to the flask and refluxed and stirred for 4 hours, cooled to room temperature, filtered, washed with water and dried to obtain a light yellow crude product, and separated by dichloromethane / petroleum ether column chromatography to obtain a white intermediate NDI-PA.

[0051] 3) Preparation of photoswitch molecule NDI-PI:

[0052] The intermediate NDI-PA, amine and ethanol were added to a round-bottom flask and refluxed with stirring for 4-7 hours in the presence of a catalytic amount of acetic acid. After the reaction was completed, the mixture was cooled to room temperature and filtered, washed thoroughly and dried to obtain a yellow solid, which was the target photoswitch molecule NDI-PI.

[0053] 4) Photochromic behavior of dual-mode optical switch:

[0054] The dual modes of the optical switch molecules of the present invention refer to the reflection mode of the material itself under natural light and the fluorescence mode under ultraviolet light.

[0055] The solid powder of the prepared photoswitch molecule NDI-PI is spread on the surface of any solid matrix. In the initial state, the powder color is yellow and the fluorescent color is green or yellow. When irradiated with light of a suitable wavelength, it can be observed that the color of the powder itself and the fluorescent color gradually turn into orange-red; after switching to another wavelength of light irradiation, the powder color and the fluorescent color return to the initial state. That is to say, in the solid state, the color and fluorescent color of the photoswitch molecule of the present invention red-shift as the light irradiation time increases. The above-mentioned fully visible light-regulated photoswitch molecule means that the forward ("on") and reverse ("off") processes of the photoswitch can be achieved by irradiation with two visible light sources of different wavelengths.

[0056] As an optimization, in step 1), the molar ratio of 1,8-naphthalene dicarboxylic anhydride NTCDA, 4-substituted phenol AP, and anhydrous DMF is 1:1:(80-120).

[0057] As an optimization, the molar ratio of the intermediate NDI-P, hexamethylenetetramine HTMA, and TFA in step 2) is 1:(1-5):(50-100).

[0058] As an optimization, the molar ratio of the intermediate NDI-PA, amine and anhydrous ethanol in step 3) is 1:(1-2):(80-120).

[0059] As an optimization, the first light irradiation wavelength used in step 4) can be any wavelength between 254nm and 480nm or between 600nm and 750nm, and the other light irradiation wavelength can be any wavelength between 490nm and 580nm.

[0060] As an optimization, the light irradiation time used in step 4) is 0 to 60 s.

[0061] As an optimization, the fluorescence excitation wavelength used in step 4) can be any wavelength between 250 and 480 nm, preferably any wavelength between 320 and 450 nm, and more preferably any wavelength between 380 and 420 nm.

[0062] The present invention also discloses a method for reversibly writing and erasing instantaneous optical information, comprising the following steps:

[0063] 1) Material preparation: Spread the dry solid powder described in this patent on any flat solid substrate surface at room temperature.

[0064] 2) Writing of optical information: Use a low-power handheld point light source with a suitable wavelength to write optical information on the powder. At this time, the optical information can be directly retained on the surface of the material. The color of the powder itself and the fluorescent color after writing are orange, and the color of the unwritten powder is yellow, and the fluorescent color is green or yellow.

[0065] 3) Optical information erasure: Use the first wavelength of light to irradiate the powder for a certain period of time. At this time, the surface color and fluorescent color of the powder itself are both orange, and no information or pattern remains.

[0066] 4) Reverse writing of optical information: Switch to the second wavelength low-power handheld point light source to reversely write optical information on the powder. At this time, the optical information can be directly retained on the surface of the material. The reflection color of the powder after writing is yellow, and the fluorescent color is green or yellow. The reflection and fluorescent colors of the unwritten powder are both orange.

[0067] 5) Optical information reverse erasure: Use the second wavelength light to irradiate for a certain period of time to make all the powders return to the initial state. At this time, the reflective color of the powder surface is yellow, and the fluorescent color is green or orange. No information or pattern remains.

[0068] As an optimization, the wavelength of the point light source used in step 2) can be any wavelength between 254nm and 480nm or between 600nm and 750nm, wherein the visible light wavelength range is preferred, and the 405nm to 450nm wavelength range is more preferred.

[0069] As an optimization, the optical information erasing light source used in step 3) can be any wavelength between 254nm and 480nm or between 600nm and 750nm, wherein the visible light wavelength range is preferred, and the 405nm to 450nm wavelength range is more preferred.

[0070] As an optimization, the wavelength of the point light source used in step 4) is any wavelength between 490 and 580 nm.

[0071] As an optimization, the optical information reverse erasing light source used in step 5) is any wavelength between 490 and 580 nm.

[0072] The present invention also discloses an optical information encryption and anti-counterfeiting application based on the optical switch material in this patent, comprising the following steps:

[0073] 1) Password design: Assign different password symbols to the fluorescence of "green", "yellow" and "orange".

[0074] 2) Information encryption: Expose the powder to light at a certain wavelength for different periods of time to obtain "green", "yellow" and "orange" fluorescent powders. Arrange and combine the coding method in step 1) to obtain the corresponding password information. In the fluorescence mode, only by knowing the coding design method can the information be correctly extracted, thereby realizing information encryption.

[0075] 3) Information clearing: The powder prepared in the previous step is irradiated by a light source of a certain wavelength, and all fluorescence is changed to a single color, thereby achieving information clearing.

[0076] As an optimization, the encoding method in step 1) can be any three-dimensional encoding such as Morse code, ternary encoding, etc.

[0077] As an optimization, the wavelength of the light source used in step 2) can be any wavelength between 254nm and 480nm or between 600nm and 750nm, wherein the wavelength range of 405nm to 450nm in the visible light wavelength range is preferred.

[0078] As an optimization, the wavelength of the light source used in step 3) can be any wavelength between 254 nm and 750 nm, wherein the wavelength range of 405 nm to 450 nm in the visible light wavelength range is preferred.

[0079] Embodiment 1:

[0080] This embodiment is an example of one of the preparation methods of photoswitch molecules. Other photoswitch molecules can be prepared according to this method. It should be pointed out that the molecular synthesis method is not unique, and such photoswitch molecules prepared according to other synthesis methods are also within the protection scope of the present invention.

[0081] 1) Preparation of intermediate NDI-P:

[0082] Add 1.98 g 1,8-naphthalene dicarboxylic anhydride NTCDA and 1.23 g p-hydroxybenzylamine AP into a round-bottom flask, stir overnight at 80°C in 70 mL DMF, cool to room temperature after the reaction is completed, pour into water, filter, wash with water, and dry to obtain a white powder, which is the intermediate NDI-P. The reaction equation is as follows:

[0083]

[0084] The H NMR spectrum data of the prepared intermediate NDI-P are: 1 H NMR (600MHz, DMSO) δ9.34 (s, 1H), 8.52 (dd, J = 7.3, 0.8Hz, 2H), 8.49–8.47 (m, 2H ),7.91–7.86(m,2H),7.22(d,J=8.5Hz,2H),6.69(d,J=8.6Hz,2H),5.15(s,2H).

[0085] 2) Preparation of intermediate NDI-PA:

[0086] 1.51 g of the intermediate NDI-P and 1.40 g of urotropine HTMA were placed in a round-bottom flask, 35 mL of trifluoroacetic acid was added under nitrogen protection, and the mixture was refluxed and stirred for 8 h. Subsequently, 60 mL of 4M HCl was added to the flask and refluxed and stirred for 4 h. After the reaction was completed, the system was cooled to room temperature, and a light yellow crude product was obtained after filtration, washing with water, and drying. The white intermediate NDI-PA (petroleum ether: dichloromethane = 1:2) was obtained by column chromatography purification. The reaction equation is as follows:

[0087]

[0088] The H NMR spectrum data of the prepared intermediate NDI-PA are: 1 HNMR (600MHz, DMSO) δ10.66(s,1H),10.17(s,1H),8.47(dd,J=25.5,7.8Hz,4H),7.85(t,J=7.7 Hz,2H),7.64(d,J=2.3Hz,1H),7.55(dd,J=8.6,2.4Hz,1H),6.91(d,J=8.6Hz,1H),5.15(s,2H).

[0089] 3) Preparation of photoswitch molecule NDI-PI-1:

[0090] Take 0.33 g of the intermediate NDI-PA in a round-bottom flask, add 35 mL of ethanol solution containing 0.11 g of benzylamine under nitrogen protection, add a catalytic amount of acetic acid, reflux and stir for 4 hours, cool to room temperature after the reaction is completed, filter, wash thoroughly, and dry to obtain a yellow powder, which is the target product NDI-PI-1. The reaction equation is as follows:

[0091]

[0092] The H NMR spectrum data of the prepared optical switch molecule NDI-PI-1 are: 1 H NMR (600MHz, DMSO) δ13.40(s,1H),8.70(s,1H),8.54(dd,J=7.2,2.7Hz,2H),8.50(dd,J=8.2,2.7Hz,2H),7.90(td,J=8.1, 3.6Hz,2H),7.51(s,1H),7.42(d,J=8.5Hz,1H),7.37–7.25(m,5H),6.84(dd,J=8.5,3.5Hz,1H),5.21(s,2H),4.76(s,2H).

[0093] Embodiment 2:

[0094] This example is a test of the multi-wavelength light response performance of the optical switch molecule NDI-PI-1 prepared in Example 1.

[0095] The reversible isomerization behavior of NDI-PI-1 under different wavelengths of light in the solid state was studied by using UV-visible diffuse reflectance spectroscopy. The main peak of the diffuse reflectance spectrum was 425nm in the initial state. After irradiation with different wavelengths of light between 280-480nm or 600-750nm, the keto peak at 489nm increased rapidly, indicating that photoisomerization behavior occurred in the solid state. Figure 1 As shown, the light response sensitivity tested under different wavelengths of light irradiation for the same time is 405nm, 420nm, 450nm, 365nm, 475nm, 600nm, and 650nm from strong to weak.

[0096] After the optical switch molecule NDI-PI-1 is converted into a keto structure by light irradiation, it can be restored to its initial state by switching to 490nm to 580nm visible light irradiation, among which the best optimized wavelength is 520nm.

[0097] Embodiment 3:

[0098] This example is about the AIE properties and dual-mode photoswitch performance of the photoswitch molecule NDI-PI-1 described in Example 1.

[0099] The fully dried solid powder of the optical switch molecule NDI-PI-1 was spread on any plane. At this time, the powder color was light yellow and emitted green fluorescence when excited, showing AIE characteristics. When irradiated with 405nm visible light for 0 to 45s, the powder color gradually changed from light yellow to orange-red. The fluorescence color gradually changed from green to yellow and finally to orange. After continuous irradiation with 520nm green light for 45s, the powder reflection color and fluorescence color can be completely restored. Therefore, the optical switch molecule NDI-PI-1 has excellent AIE properties and reversible dual-mode photochromic properties in the solid state.

[0100] The reversible photoisomerization behavior of the solid powder of the photoswitch molecule NDI-PI-1 under light irradiation of different wavelengths was studied by UV-visible diffuse reflectance spectroscopy. Figure 2 It can be seen from the diffuse reflectance spectrum that the intensity of the absorption peak at 489nm increases rapidly under different irradiation times of the 405nm light source. Figure 3 As shown in Figure 2, when the irradiation is switched to 520nm ultraviolet light, the intensity of the absorption peak at this position decreases rapidly, which further verifies the bidirectional photoisomerization process of the molecule. The optical switch molecule exhibits good cycling performance. Figure 4 It can be seen that by continuously switching between 405nm and 520nm light sources, the diffuse reflectance spectrum of the optical switch molecule did not show any decrease after 10 cycles, showing excellent fatigue resistance.

[0101] The fluorescence changes of the solid powder of optical switch molecules under the irradiation of light of different wavelengths were studied by fluorescence spectrometer. Figure 5 It can be seen from the fluorescence spectrum that in the initial state, the molecule exhibits fluorescence emission at 515nm. After irradiation with a 405nm light source for 6s, the fluorescence emission peak at 515nm gradually weakens and turns into yellow fluorescence emission with a wavelength of 540nm. When the 405nm light source continues to irradiate, the fluorescence emission peak at 510nm completely disappears, the fluorescence intensity at 540nm weakens, and finally turns into orange fluorescence at 580nm, showing excellent dynamic regulation characteristics of solid-state multi-channel fluorescence. Figure 8 The UV-visible diffuse reflectance spectrum and fluorescence spectrum of the solid powder of the optical switch molecule NDI-PI-1 in Example 3 at 489 nm under alternate irradiation with light of 405 nm and 520 nm.

[0102] Embodiment 4:

[0103] This embodiment is an application of the optical switch molecule NDI-PI-1 in the instantaneous reversible erasing of optical information.

[0104] Optical switch molecules can respond quickly under multi-wavelength light, and by rationally switching the wavelength of light, rapid writing and erasing of optical information in dual modes can be achieved.

[0105] like Figure 6 As shown, the solid powder of the optical switch material NDI-PI-1 used in Example 1 is spread on a plane. At the beginning, the color of the material itself is yellow, and the fluorescent color is green. The SEU letters can be quickly written on the surface of the material using a 405nm handheld point light source. An orange letter pattern is displayed on the yellow powder under a fluorescent lamp. The pattern can also be retained in the fluorescent mode. Continue to use the 405nm light source to completely cover the optical information SEU; when switching to a 520nm green handheld point light source to write new information RM letters, the letter pattern itself is yellow in color and green in fluorescent color; continue to use 520nm green light to irradiate for 45s, the new information RM is erased, and the powder color and fluorescent color can be completely restored to the initial state. Therefore, the optical switch molecule NDI-PI-1 has good multi-wavelength optical information repeated writing and erasing performance and can be reused.

[0106] Embodiment 5:

[0107] This example shows the potential application of the optical switch molecule NDI-PI-1 in information encryption and anti-counterfeiting. Figure 7 As shown. The encryption effect is set by using the fluorescent colors of the three channels of "green", "yellow" and "orange". The encryption methods include but are not limited to Morse code and ternary coding system. The encryption anti-counterfeiting effect of ternary coding is shown here. The optical switch molecule NDI-PI-1 is irradiated under a 405nm light source for a certain period of time to obtain "green", "yellow" and "orange" fluorescent powders. Different fluorescent colors correspond to the codes of "0", "1" and "2" respectively. "10002", "2120" and "10011" corresponding to "S", "E" and "U" can be displayed through fluorescent colors. This kind of fluorescent information is completely realized by a single molecule, so it has very good application prospects in information encryption and anti-counterfeiting.

[0108] Embodiment 6:

[0109] This example is carried out according to the preparation method of the optical switch molecule NDI-PI-1 prepared in Example 1, except that the benzylamine in step 3 is replaced by n-butylaniline, and the prepared optical switch molecule is labeled as the optical switch molecule NDI-PI-2. Its molecular structure is as follows:

[0110]

[0111] The H NMR spectrum data of the prepared optical switch molecule NDI-PI-2 are: 1H NMR (600MHz, DMSO-d6) δ13.22(s,3H),8.93(s,1H),8.51(dd,4H),7.95–7.86(m,2H),7.66(d,J=2.2Hz,1H),7.48(dd,J=8.5,2.2Hz,1H),7.32( d,J=8.3Hz,2H),7.24(d,J=8.3Hz,2H),6.92(d,J=8.5Hz,1H),5.23(s,2 H),2.61–2.56(m,2H),1.55(m,2H),1.29(m,2H),0.89(t,J=7.4Hz,3H).

[0112] Embodiment 7:

[0113] This embodiment is the AIE properties and dual-mode optical switch performance of embodiment 6.

[0114] After being fully dried, the solid powder of the optical switch molecule NDI-PI-2 is yellow in color and emits yellow fluorescence when excited, showing AIE characteristics. When irradiated with ultraviolet light for 0 to 45 seconds, the powder color gradually changes from yellow to orange-red, and the fluorescence color gradually changes from yellow to orange after continuous irradiation with ultraviolet light for 45 seconds. After continuous irradiation with 520nm green light for 45 seconds, the powder reflection color and fluorescence color can be completely restored. Therefore, the optical switch molecule NDI-PI-2 has excellent AIE properties and reversible dual-mode optical switching properties in the solid state.

[0115] Embodiment 8:

[0116] This example is carried out according to the preparation method of the optical switch molecule NDI-PI-2 prepared in Example 6, except that the p-hydroxybenzylamine in step 1 is replaced by p-hydroxyaniline. The prepared optical switch molecule is labeled as the optical switch molecule NDI-PI-3, and its molecular structure is as follows:

[0117]

[0118] The H NMR spectrum data of the prepared optical switch molecule NDI-PI-3 are as follows: 1H NMR (600MHz, DMSO-d6) δ13.35(s,1H),8.96(s,1H),8.52(d,J=7.7Hz,4H),7.91(t,J=7.7Hz,2H),7.67(d,J=2.5Hz,1H),7.43(dd,J=8.6,2.5Hz,1H),7 .36(d,J=8.3Hz,2H),7.29(d,J=8.4Hz,2H),7.11(d,J=8.6Hz,1H),2.61(t, J=7.6Hz,2H),1.61–1.52(m,2H),1.35–1.26(m,2H),0.90(t,J=7.4Hz,3H).

[0119] Embodiment 9:

[0120] This embodiment is the AIE properties and dual-mode optical switch performance of Example 8.

[0121] After being fully dried, the solid powder of the optical switch molecule NDI-PI-3 is yellow in color and emits yellow fluorescence when excited, showing AIE characteristics. When irradiated with ultraviolet light for 0 to 45 seconds under a fluorescent lamp, the powder color gradually changes from yellow to red, and the fluorescence color gradually changes from yellow to red after continuous irradiation with ultraviolet light for 45 seconds. When irradiated with 520nm green light for 45 seconds, the powder reflection color and fluorescence color can be completely restored. Therefore, the optical switch molecule NDI-PI-3 has excellent AIE properties and reversible dual-mode optical switching properties in the solid state.

[0122] Based on the above embodiments, the salicylaldehyde Schiff base molecules prepared by the present invention can produce the property of rapid full visible light response in the solid state, can realize the dual-mode switch of the material reflection mode and fluorescence mode, and have the advantages of good stability, fast response speed, multi-wavelength response, full visible light regulation, etc., and have good application prospects in the field of solid-state optical switch materials. In addition, due to the sensitive light response ability and recycling performance, this optical switch material can realize instantaneous optical information loading and erasure, showing the advantages of fast erasing speed, dual-mode display, good contrast, and reverse writing. The molecule also shows the potential for encryption and anti-counterfeiting applications of optical information. The color difference of the material before and after the light response and the color range are used to design the method of weakening and enhancing optical information. The acquired image shows obvious characteristics of optical information weakening under red filtering, realizing the encryption of optical information. After removing the filtering, the optical information is restored and displayed, and the signal is enhanced when switching to green filtering, thereby realizing the encryption and anti-counterfeiting of optical information.

[0123] The present invention provides a new solution for the technical field of organic solid-state optical switch materials. Technicians in this field can make several modifications and changes without departing from the principles of the present invention, and these changes are also within the protection scope of the claims of the present invention.

Claims

1. Salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation, characterized in that: It has a molecular structure shown in Formula I:

2. The salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation according to claim 1, characterized in that: The optical switch molecule has a natural light reflection mode and a fluorescence mode under ultraviolet light; in the solid state, its own color and fluorescence color red-shift as the light irradiation time increases; the forward "on" and reverse "off" processes of the optical switch can be achieved by irradiation with two visible light sources of different wavelengths.

3. The salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation according to claim 2, characterized in that: The wavelength of one light source used by the optical switch molecule is any wavelength between 254nm and 480nm or between 600nm and 750nm, and the wavelength of the other light source is any wavelength between 490nm and 580nm; the irradiation time of the light source of the optical switch molecule is 0 to 60s.

4. A method for preparing a salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation according to any one of claims 1 to 3, characterized in that the steps include: 1) Preparation of intermediate NDI-P: The reaction equation is as follows: 2) Preparation of intermediate NDI-PA: The reaction equation is as follows: 3) Preparation of photoswitch molecule NDI-PI: The reaction equation is as follows:

5. The method for preparing a salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation according to claim 4, characterized in that: Step 1) the molar ratio of 1,8-naphthalene dicarboxylic anhydride NTCDA, para-substituted amine AP, and anhydrous DMF is 1:1:80-120; Step 2) the molar ratio of intermediate NDI-P, urotropine HMTA, and TFA is 1:1-5:50-100; Step 3) the molar ratio of intermediate NDI-PA, amine, and anhydrous ethanol is 1:1-2:80-120.

6. Application of the salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation according to any one of claims 1 to 3 in the field of optical information erasure.

7. The use according to claim 6, characterized in that: The following steps are involved: 1) Material preparation: Spread the dry solid powder of the switch molecule on any flat solid substrate surface at room temperature; 2) Writing of optical information: Use a low-power handheld point light source with a suitable wavelength to write optical information on the powder. At this time, the optical information is directly retained on the surface of the material. The color of the powder itself and the fluorescent color after writing are orange, and the color of the unwritten powder is yellow, and the fluorescent color is green or yellow; 3) Optical information erasure: Use the first wavelength of light to irradiate the powder for a certain period of time. At this time, the surface color and fluorescent color of the powder itself are both orange, and no information or pattern remains; 4) Reverse writing of optical information: Switch to the second wavelength low-power handheld point light source to reversely write optical information on the powder. At this time, the optical information is directly retained on the surface of the material. The reflected color of the powder after writing is yellow, and the fluorescent color is green or yellow. The reflected and fluorescent colors of the unwritten powder are both orange. 5) Optical information reverse erasure: Use the second wavelength light to irradiate for a certain period of time to make all the powders return to the initial state. At this time, the reflective color of the powder surface is yellow, and the fluorescent color is green or orange. No information or pattern remains.

8. Application of the salicylaldehyde Schiff base solid-state dual-mode optical switch molecule based on full visible light regulation according to any one of claims 1 to 3 in the field of information encryption and anti-counterfeiting.

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