A Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal and its application as an electrochromic material

Abstract

The application discloses a Zn(NDI-H) film@anodic aluminum oxide photonic crystal and an application of the Zn(NDI-H) film@anodic aluminum oxide photonic crystal as an electrochromic material. The electrochromic material is composed of a Zn(NDI-H) film and an anodic aluminum oxide photonic crystal, the Zn(NDI-H) film is grown on a FTO conductive surface, the Zn(NDI-H) film is arranged in close connection with the anodic aluminum oxide photonic crystal, a conductive liquid is arranged between the Zn(NDI-H) film and the anodic aluminum oxide photonic crystal, and the structural color of the anodic aluminum oxide photonic crystal is ochre. Voltages are applied to both ends of the Zn(NDI-H) film@anodic aluminum oxide photonic crystal, and the Zn(NDI-H) film and the anodic aluminum oxide photonic crystal realize synergic color development; when the voltage is switched from -4.5 V to -5.5 V, the whole device presents a color change from light yellow to light green.

Description

Technical Field

[0001] This invention belongs to the field of electrochromic material preparation, and specifically relates to the use of a Zn(NDI-H) thin film and anodized aluminum oxide photonic crystal color-changing material. Background Technology

[0002] Traditional visible light camouflage techniques involve coating physical surfaces with camouflage patterns that match the background color, thereby minimizing the visible contrast in brightness and chromaticity between the target and the background. While easy to implement, this method is limited to situations where the target is stationary or moving slowly, and it also has low color resolution, making it easily detectable and tracked by modern high-resolution detectors. Therefore, developing intelligent camouflage materials that can actively blend into the background, especially typical background variations such as forests, deserts, and shallow waters, is of great significance.

[0003] Photonic crystals are artificial microstructures formed by periodically arranging dielectric materials with different refractive indices as basic units. By fine-tuning the structure, the photonic bandgap can be controlled, thereby regulating the material's color. Flexible coordination polymers are materials that combine flexibility and potential porosity, formed by connecting organic ligands with metals (or metal clusters) as nodes through a specific topological structure. Due to the diversity of coordination modes, the flexibility of ligand design, and the tunability of electrical properties, coordination polymers have shown superior performance in electrochromic applications. However, current reports on photonic crystals in visible light multi-background fusion stealth materials and technologies are mostly in the early stages of theoretical and experimental exploration. How to combine electrochromic coordination polymers with photonic crystals remains a challenge. The mechanism of synergistic color change between electrochromic coordination polymers and photonic crystals is not fully understood, and precise color control remains a significant problem. Summary of the Invention

[0004] To overcome the problem of the limited color variation of Zn(NDI-H), this invention provides a Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal and its application in electrochromism.

[0005] The technical solution to achieve the purpose of this invention is: a Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal, wherein the electrochromic material is composed of a Zn(NDI-H) thin film and an anodic aluminum oxide photonic crystal, the Zn(NDI-H) thin film is grown on an FTO conductive surface, the Zn(NDI-H) thin film and the anodic aluminum oxide photonic crystal are bonded together, and a conductive liquid is placed between the two, and the anodic aluminum oxide photonic crystal has a yellowish-brown structural color.

[0006] Preferably, the conductive liquid is a 0.1 M DMF solution of TBA·PF6.

[0007] Preferably, the Zn(NDI-H) thin film and the anodic aluminum oxide photonic crystal are bonded together by external force.

[0008] The preparation method of the above-mentioned Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal includes the following steps:

[0009] Step 1: Ultrasonic cleaning and electrochemical polishing of the aluminum sheet;

[0010] Step 2: The aluminum sheet obtained in Step 1 is used to prepare anodized aluminum photonic crystals with a structural color of yellowish-brown using a periodic variable current method;

[0011] Step 3: Dissolve ligand H2NDI-H and Zn(NO3)2·6H2O in DMF, vertically place them into the FTO substrate, slowly heat to 130 °C for about 30 minutes, and let stand at 130 °C for a period of time;

[0012] Step 4: After the reaction is complete, the substrate is removed, immersed in DMF and ultrasonically treated to remove loose powder, and then the film on the non-conductive surface of the substrate is wiped off to obtain a Zn(NDI-H) film grown on the conductive surface of FTO.

[0013] Step 5: Add an appropriate amount of conductive liquid to the surface of the anodic aluminum oxide photonic crystal, and then use external force to attach the Zn(NDI-H) film grown on the FTO conductive surface to the anodic aluminum oxide photonic crystal, wherein the Zn(NDI-H) film is in contact with the anodic aluminum oxide photonic crystal.

[0014] Preferably, in step 1, the electrochemical polishing voltage is 21 V and the electrochemical polishing temperature is 0~5 ℃.

[0015] Preferably, in step 2, when preparing the anodic aluminum oxide photonic crystal using the periodic variable current method, the waveform of the periodic current density is as follows: within one period of 1100 seconds, t 1 Time current density is j 1 =1.12 mA / cm 2 , t 2 Time current density is j 2 =0.28 mA / cm 2 , t 1 and t 2 The ratio is 1:4; the number of cycles is 145, the oxidation time of the last cycle is 85% of that of the first cycle, and the oxidation time of each cycle decreases by 0.1%; the electrolyte is 0.5 M sulfuric acid; the electrolysis (oxidation) temperature is 0~5℃.

[0016] Preferably, in step 3, the size of the FTO substrate is 2×1 cm. 2 .

[0017] Preferably, in step 3, the mixture is left to stand at 130 °C for 3 to 4 hours.

[0018] The aforementioned Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal is used as an electrochromic material. When a voltage of 0 to -5.5 V is applied across the Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal, the material exhibits a color change from the structural color (brown) of the anodic aluminum oxide photonic crystal itself to pale yellow when the voltage is switched from 0 V to -4.5 V; when the voltage is switched from -4.5 V to -5.5 V, the material exhibits a color change from pale yellow to pale green.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] (1) Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal is used for the first time in electrochromic materials. It is composed of Zn(NDI-H) thin film and anodic aluminum oxide photonic crystal. The Zn(NDI-H) thin film grows an FTO conductive surface. The Zn(NDI-H) thin film is in contact with the anodic aluminum oxide photonic crystal and a conductive liquid is placed between them. The anodic aluminum oxide photonic crystal has a yellowish-brown structural color.

[0021] (2) When a voltage is applied across the Zn(NDI-H) thin film and the anodic aluminum oxide photonic crystal, the Zn(NDI-H) thin film and the anodic aluminum oxide photonic crystal achieve synergistic color development. When the voltage is switched to -4.5 V, the entire device exhibits a predominantly pale yellow color; when the voltage is switched to -5.5 V, the entire device exhibits a predominantly pale green color. Attached Figure Description

[0022] Figure 1 This is a photograph of the yellowish-brown anodic aluminum oxide photonic crystal prepared in Example 1.

[0023] Figure 2 The 1H NMR spectrum of H2NDI-H prepared in Example 1.

[0024] Figure 3 The image shows the X-ray diffraction pattern of the Zn(NDI-H) thin film on the FTO substrate described in Example 1.

[0025] Figure 4 The color change of the Zn(NDI-H) thin film in the conductive liquid described in Example 1 with voltage.

[0026] Figure 5Cyclic voltammogram (25 cycles) of Zn(NDI-H) thin film on FTO substrate described in Example 1.

[0027] Figure 6 The color change of the FTO / Zn(NDI-H) thin film / FTO sandwich structure described in Example 1 with voltage.

[0028] Figure 7 The color change of the FTO / Zn(NDI-H) thin film / conductive solution / anodic aluminum oxide photonic crystal sandwich structure described in Example 1 is a coordinated change with voltage. Detailed Implementation

[0029] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0030] The inventors originally planned to directly grow a Zn(NDI-H) thin film on an anodic aluminum oxide photonic crystal, integrating the Zn(NDI-H) film and the anodic aluminum oxide photonic crystal, and then study their synergistic color-changing behavior by applying a voltage. However, during the experiment, it was found that after the Zn(NDI-H) film and the anodic aluminum oxide photonic crystal were integrated, the presence of the aluminum substrate prevented current from flowing through the Zn(NDI-H) film, thus failing to achieve the synergistic color development induced by electrochromism. Therefore, the strategy was changed, and an FTO / Zn(NDI-H) film / conductive solution / anodic aluminum oxide photonic crystal sandwich structure was constructed, and a voltage was applied to induce its synergistic color-changing behavior. Example 1

[0031] Aluminum sheets with a purity of 99.99% were ultrasonically cleaned for 5 min each in acetone and anhydrous ethanol solutions to remove oil. Electrochemical polishing was then performed on the aluminum sheets at 0–5 °C using a 4:1 (v / v) ethanol / perchloric acid solution as the polishing solution, with a polishing voltage of 21 V. The polishing was also performed at 0–5 °C in a 0.5 M sulfuric acid electrolyte at a voltage of 1.12 mA / cm². 2 After 2 hours of current density oxidation, the aluminum sheet was oxidized using a periodic current. The waveform of the periodic current density is as follows: within one cycle, t 1 Time current density is j 1 =1.12mA / cm 2 , t 2 Time current density is j 2 =0.28 mA / cm 2 , t 1 and t 2The ratio is 1:4. Anodizing for 145 cycles yields an anodized aluminum photonic crystal. During the anodizing process, a gradual compensation measure is used to control bandgap drift. Specifically, the oxidation cycle time is not a fixed value but gradually decreases. The oxidation time of the last cycle is 85% of the first cycle, meaning the oxidation time decreases by 0.1% for each cycle. Using this periodic variable current method, an anodized aluminum photonic crystal with a yellowish-brown structural color is obtained, such as... Figure 1 As shown.

[0032] In a dry 100 ml flask, add 0.86 g of 1,4,5,8-naphthalenetetracarboxylic anhydride, 0.75 g of 3,5-dimethyl-1H-pyrazole-4-amine, and 50 ml of anhydrous DMF. Heat the reaction mixture at 150 °C under nitrogen atmosphere with rapid stirring for 12 hours. After the reaction is complete, cool the flask to room temperature and pour the solution into 150 ml of stirred diethyl ether. Filter to separate the precipitated solid and recrystallize from DMF / ether / H₂O (10 ml:15 ml:5 ml). Filter the product and dry under vacuum at 70 °C to obtain H₂NDI-H, whose 1H NMR spectrum is shown below. Figure 2 As shown.

[0033] In a 100 ml screw-cap flask, dissolve 118 mg of ligand H2NDI-H and 86 mg of Zn(NO3)2·6H2O in 60 ml of DMF. Place a clean 2×1 cm... 2 The FTO substrate was placed in a screw-cap container and immersed below the solution surface. The screw-cap container was then immersed in an oil bath and slowly heated to 130 °C for approximately 30 minutes under a nitrogen atmosphere, maintaining this temperature for 3.5 hours. After the reaction, the mixture was cooled to room temperature, the substrate was removed, and cleaned with acetone to remove loose powder. The substrate was then immersed in a vial containing 20 ml of DMF and sonicated for approximately 1 minute. After sonication, the film was cleaned with acetone to remove residual powder. The substrate was removed, and the film adhering to the non-conductive surface of the FTO plate was carefully wiped with a cotton swab moistened with 1 M HCl solution (before spectroelectrochemical measurements). After cleaning with ethanol and acetone, the film was vacuum dried at 70 °C, yielding a Zn(NDI-H) electrochromic film on the FTO conductive substrate. Its X-ray diffraction pattern is shown below. Figure 3 As shown

[0034] In a DMF solution containing 0.1 M TBA·PF6, an FTO film was used as the working electrode, a platinum mesh as the counter electrode, and an Ag / Ag (acetonitrile) electrode was used. +The Zn(NDI-H) film was used as a reference electrode for cyclic voltammetry (CV) measurements. During the cycling process, the Zn(NDI-H) film changed from nearly transparent colorless to pale yellow, and then to dark brown. The color change was rapid and reversible. Figure 4 As shown. Notably, the Zn(NDI-H) film also exhibits excellent electrochemical cycling stability; at a scan rate of 100 mV / s, the peak current observed over 25 cycles did not decrease, as shown. Figure 5 As shown.

[0035] An FTO / Zn(NDI-H) thin film / FTO sandwich structure was constructed, with the FTO / Zn(NDI-H) thin film serving as the working electrode and blank FTO as the counter electrode. One drop of 0.1 M TBA·PF6 DMF solution was added to the blank FTO as a conductive liquid. The FTO / Zn(NDI-H) thin film was then placed on top and clamped, ensuring contact between the Zn(NDI-H) thin film and the blank FTO. When energized, the device changed from nearly transparent and colorless to pale yellow when the voltage switched from 0 V to -2.7 V; when the voltage switched from -2.7 V to -3.0 V, the device appeared dark brown. Figure 6 As shown.

[0036] A sandwich structure of FTO / Zn(NDI-H) thin film / conductive solution / anodic aluminum oxide photonic crystal was constructed. The FTO / Zn(NDI-H) thin film served as the working electrode, and the anodic aluminum oxide photonic crystal served as the counter electrode. One drop of 0.1 M TBA·PF6 DMF solution was dropped onto the anodic aluminum oxide photonic crystal as the conductive liquid. The FTO / Zn(NDI-H) thin film was then placed on top and clamped, bringing the Zn(NDI-H) thin film into contact with the anodic aluminum oxide photonic crystal. At 0 V, the Zn(NDI-H) thin film was transparent, and the entire device exhibited the structural color of the anodic aluminum oxide photonic crystal itself. Upon energization, the Zn(NDI-H) thin film and the anodic aluminum oxide photonic crystal achieved synergistic color development. When the voltage switched to -4.5 V, the entire device exhibited a predominantly pale yellow color; when the voltage switched to -5.5 V, the entire device exhibited a predominantly pale green color, such as... Figure 7 As shown.

[0037] The above results demonstrate that electrochromism using a single coordination polymer is feasible. Zn(NDI-H) possesses advantages such as good redox reversibility and high porosity, but its single color change limits its application in electrochromic applications.

Claims

1. A Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal, characterized in that, The electrochromic material is composed of a Zn(NDI-H) thin film and an anodic aluminum oxide photonic crystal, the Zn(NDI-H) thin film is grown on an FTO conductive surface, the Zn(NDI-H) thin film is arranged in close contact with the anodic aluminum oxide photonic crystal, and a conductive liquid is arranged between the two, and the structural color of the anodic aluminum oxide photonic crystal is khaki.

2. The Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal of claim 1, wherein, The conductive liquid is a DMF solution of TBA·PF6 with a concentration of 0.1 M.

3. The Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal of claim 1, wherein, The Zn(NDI-H) thin film and the anodic aluminum oxide photonic crystal are arranged in close contact by external force.

4. A method for preparing Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal, characterized in that, The method comprises the following steps: Step 1: ultrasonic cleaning and electrochemical polishing of an aluminum sheet; Step 2: using a periodic variable current method to prepare an anodic aluminum oxide photonic crystal with a structural color of khaki on the aluminum sheet obtained in step 1; Step 3: dissolving ligand H2NDI-H and Zn(NO3)2·6H2O in DMF, vertically placing the FTO substrate, slowly heating to about 130 DEG C for about 30 minutes, and standing at 130 DEG C for a period of time; Step 4: after the reaction is completed, the substrate is taken out, immersed in DMF for ultrasonic treatment to remove the loose powder, and the thin film on the non-conductive surface of the substrate is wiped off, to obtain a Zn(NDI-H) thin film grown on the FTO conductive surface; Step 5: adding an appropriate amount of conductive liquid on the surface of the anodic aluminum oxide photonic crystal, and arranging the Zn(NDI-H) thin film grown on the FTO conductive surface in close contact with the anodic aluminum oxide photonic crystal by external force, wherein the Zn(NDI-H) thin film is in contact with the anodic aluminum oxide photonic crystal.

5. The method of claim 4, wherein, In step 1, the electrochemical polishing voltage is 21 V, and the electrochemical polishing temperature is 0-5 DEG C.

6. The method of claim 4, wherein, In step 2, the waveform of the periodic current density in the preparation of anodic aluminum oxide photonic crystal by the periodic current method is as follows: in a period of 1100 seconds, t 1 The time current density is j 1 = 1.12 mA / cm 2 , t 2 The time current density is j 2 = 0.28 mA / cm 2 , t 1 And the ratio of t 2 is 1:

4. The number of cycles is 145, and the oxidation time of the last cycle is 85% of the first cycle, and the oxidation time of each cycle decreases by 0.1% each time; The electrolyte is 0.5 M sulfuric acid, and the electrolysis (oxidation) temperature is 0-5 DEG C.

7. The method of claim 4, wherein, In step 3, the size of the FTO substrate was 2 x 1 cm 2 .

8. The method of claim 4, wherein, In step 3, the standing time at 130 DEG C is 3-4 hours.

9. Use of the Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal as an electrochromic material according to any one of claims 1-3.

10. Use according to claim 9, characterized in that, When a voltage is applied to both ends of the Zn(NDI-H) thin film@anodic aluminum oxide photonic crystal and the voltage is switched from -4.5 V to -5.5 V, the material exhibits a color change from light yellow to light green.

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