Chlorophyll copper-doped anhydrous guanine crystal sheet and preparation method and application thereof

Abstract

This invention relates to a copper-doped anhydrous guanine crystal sheet, its preparation method, and its application, belonging to the field of spectral camouflage and stealth materials. Specifically, it relates to a method for synthesizing copper-doped guanine crystals. In this invention, copper-doped chlorophyll is used as the functional molecule, and organic small molecule uric acid and high molecular weight polymer (P(VP-co-VA)) are used as additives to regulate the synthesis of green guanine microsheets that preferentially expose the (100) crystal facet with the optimal refractive index. The guanine crystal microsheets prepared by this invention have high reflectivity and specific visible light absorption in the 200-2500 nm range, while also having the effect of weakening polarized light. Embedding the pigment molecules into the crystal lattice achieves a good stabilizing effect on copper-doped chlorophyll, making it a novel camouflage material with high reflectivity and excellent stability.

Description

Technical Field

[0001] This invention relates to a chlorophyll copper-doped anhydrous guanine crystal sheet, its preparation method and application, belonging to the field of spectral stealth camouflage materials. Background Technology

[0002] By altering the original characteristics of an object, its true information can be concealed, thus achieving effective concealment and camouflage. However, with the continuous advancement and development of reconnaissance and surveillance technologies in modern warfare, such as hyperspectral imaging and polarization detection, existing camouflage methods are no longer sufficient to meet the demands of warfare. With the rapid development of hyperspectral imaging technology, analyzing the high-resolution reflectance spectrum of targets in the visible-near-infrared band (400-2500nm) and comparing it with the background, achieving a spectral resolution of 5-10nm, has become widely used in the military field. To achieve better camouflage, the camouflaged target must have highly similar spectral characteristics to the ground background. Therefore, the development of hyperspectral biomimetic materials that are "of the same color and spectrum" as the background has become a research hotspot in the field of optical stealth camouflage. For ground targets, green vegetation is the most widely used background. Designing green camouflage materials to simulate the reflectance spectrum of green vegetation against the green background of ground military targets can counter hyperspectral imaging technology and achieve stealth camouflage effects in the visible to infrared light bands.

[0003] The reflectance spectral characteristics of green vegetation in the 380-780nm visible light region are mainly influenced by the absorption of chlorophyll molecular orbitals. Its unique conjugated large π system gives it strong selective absorption of red light (approximately 680nm) and blue-violet light (approximately 330-450nm), while its absorption of green light is minimal. Therefore, the reflectance spectrum of green vegetation exhibits a green reflectance peak at 550nm. The simplest and most effective way to accurately simulate the spectral characteristics of green vegetation is to directly use chlorophyll, the exact same coloring "pigment" as green leaves. Chlorophyll has poor light and weather resistance. Although there are many research reports on chlorophyll-mimicking camouflage materials, problems such as material instability, easy dehydration, and poor near-infrared reflectance spectral consistency remain common. After leaving the plant, chlorophyll is easily decomposed and loses its green reflectance peak under the influence of light, temperature, pH, and oxygen. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a chlorophyll copper-doped anhydrous guanine crystal sheet, its preparation method, and its application.

[0005] The technical solution of this invention is:

[0006] A copper-doped anhydrous guanine crystal sheet, wherein the anhydrous guanine crystal is a guanine microsheet with an exposed high refractive index (100) plane;

[0007] The method for preparing guanine is as follows:

[0008] The first step is to prepare a sodium salt solution of guanine. The specific method is as follows: prepare a solution using industrial anhydrous guanine powder and sodium hydroxide. The molar ratio of guanine to sodium hydroxide is 1:(3-5). For example, dissolve 0.1M (M represents mol / L) guanine in 0.4M sodium hydroxide. The concentration of guanine in the resulting solution is 0.05-0.2M, and the concentration of sodium hydroxide is 0.3-0.5M.

[0009] The second step is to prepare the dispersion. The specific method is as follows: formamide, polymer additive, small molecule additive, water, and copper chlorophyllin are prepared into a dispersion according to a set ratio. The polymer additive is a copolymer based on vinylpyrrolidone, namely vinyl acetate and N-vinylpyrrolidone (P(VP-co-VA)). The small molecule additive is uric acid. The ratio of formamide, small molecule additive, polymer additive, water, and copper chlorophyllin is 10:(0.1-20):(1-50):1.5:(1-50).

[0010] The third step is to add the sodium salt solution prepared in the first step to the dispersion prepared in the second step. The volume ratio of the solution is sodium salt solution: dispersion = 1:20. After mixing evenly, let it stand at 40°C for 10-12 hours to obtain a pearly green guanine micron flake dispersion.

[0011] The fourth step involves subjecting the dispersion to multiple centrifugation and washing processes to obtain anhydrous guanine micron-sized crystal flakes.

[0012] An application of copper-doped anhydrous guanine crystal sheets is described, which are applied to the surfaces of military trucks, camouflage nets, etc. The anhydrous guanine sheets with high reflectivity, low polarization, and specific visible light absorption are coated on the surfaces of military items and camouflage nets to achieve effects such as simulating the hyperspectral polarization camouflage of green vegetation.

[0013] Compared with existing technologies, the beneficial effects of the present invention are as follows:

[0014] (1) The chlorophyll copper-doped anhydrous guanine crystal sheets synthesized in this invention have good morphological stability and solubility, and do not change when dispersed in water or ethanol for several months.

[0015] (2) The chlorophyll copper-doped anhydrous guanine crystal sheets synthesized in this invention have good color stability and show no obvious color change when dispersed in water or vacuum dried for several months.

[0016] (3) The anhydrous guanine crystal sheet doped with chlorophyll copper synthesized in this invention uses chlorophyll copper as an additive to embed chlorophyll copper molecules into the guanine crystal lattice. Therefore, the stability of chlorophyll copper molecules is improved due to being wrapped by the lattice, and the product exhibits a bright green appearance.

[0017] (4) In this invention, a high molecular polymer is used as a morphology regulator to artificially synthesize anhydrous guanine crystal sheets with copper doped chlorophyll on a specific exposed surface. These micron sheets are mostly elongated hexagonal. The presence of the polymer makes the crystal preferentially expose the (100) crystal plane with the best refractive index. The crystal form is a mixture of α and β.

[0018] (5) The length of the copper-doped anhydrous guanine crystal microsheets synthesized in this invention is 5-10 μm.

[0019] (6) The chlorophyll copper-doped anhydrous guanine crystal sheets synthesized in this invention have good dispersibility in water or other solvents. The dispersion has obvious pearlescent color and bright green color. It has strong selective absorption of red light (about 680 nm) and blue-violet light (about 330-450 nm) in the visible light region.

[0020] (7) The chlorophyll copper-doped anhydrous guanine crystal sheets synthesized in this invention generally exhibit high reflectivity in the 200-2000 nm range.

[0021] (8) The chlorophyll copper-doped anhydrous guanine crystal sheet synthesized in this invention has a weakening effect on incident horizontally polarized light and vertically polarized light, and the weakening effect is enhanced compared to industrial guanine. Attached Figure Description

[0022] Figure 1 Macroscopic image of anhydrous guanine microsheets doped with copper chlorophyll;

[0023] Figure 2 SEM image of anhydrous guanine microsheets doped with copper chlorophyll;

[0024] Figure 3 XRD pattern of anhydrous guanine microsheets doped with copper chlorophyll;

[0025] Figure 4 The diffuse reflectance spectrum of anhydrous guanine microsheets doped with copper chlorophyll;

[0026] Figure 5 The UV-Vis absorption spectrum of anhydrous guanine micron flakes doped with copper chlorophyll.

[0027] Figure 6The polarization results are for copper-doped anhydrous guanine microsheets; (a)(b)(c) are copper-doped guanine synthesized in the example, and (d)(e)(f) are industrial guanine.

[0028] Figure 7 The results show the stability of chlorophyll copper-doped anhydrous guanine microsheets. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Example

[0031] A method for preparing chlorophyll copper-doped anhydrous guanine crystal sheets, the specific steps of which include:

[0032] The first step is to prepare a sodium hydroxide solution of guanine. The specific method is as follows: mix guanine powder and sodium hydroxide solution to obtain a solution with a guanine concentration of 0.1M and a sodium hydroxide concentration of 0.4M.

[0033] The second step is to prepare the dispersion. The specific method is as follows: prepare a dispersion by mixing 10ml of formamide, 0.1mg of P(VP-co-VA), 0.1mg of uric acid, 1.5ml of water, and 1mg of copper chlorophyllin.

[0034] The third step involves adding the prepared sodium hydroxide solution of guanine to the prepared dispersion, mixing, and then allowing it to stand at 60°C for 24 hours to obtain a pearlescent green guanine nanosheet dispersion. The dispersion is then subjected to a centrifugation-washing process to obtain guanine micron-sized crystal flakes.

[0035] Figure 1 The images show an aqueous dispersion and a coating of chlorophyll copper-doped anhydrous guanine crystal sheets in this embodiment, displaying a bright pearlescent color and a vivid green.

[0036] Figure 2 This is a SEM image of the copper-doped anhydrous guanine crystal sheet in this embodiment, showing a hexagonal plate-like morphology;

[0037] Figure 3 XRD of chlorophyll copper-doped anhydrous guanine crystal sheets; the crystals exhibit a mixed α and β morphology.

[0038] Figure 4 The diffuse reflectance spectrum of anhydrous guanine crystal sheets doped with copper chlorophyll shows high reflectance over a wide wavelength range of 200-2500 nm.

[0039] Figure 5The UV-Vis absorption spectrum of anhydrous guanine crystal flakes doped with copper chlorophyll is shown. The doped crystals exhibit strong characteristic absorption of red and blue-violet light.

[0040] Figure 6 The polarization results of copper-doped anhydrous guanine crystal sheets show that, compared with industrial guanine, the synthesized copper-doped guanine exhibits enhanced polarization reduction effect.

[0041] Figure 7 The image shows the stability results of anhydrous guanine crystal sheets doped with copper chlorophyllin. Even after prolonged photothermal treatment, the copper chlorophyllin molecules in the crystals still exhibit high stability.

[0042] An application of copper-doped anhydrous guanine crystal flakes: The obtained copper-doped anhydrous guanine micron flake crystals are used as pearlescent pigments in coatings, paints, and rubber, and coated on the surface of military items and camouflage nets to simulate the hyperspectral polarization of green vegetation to achieve a camouflage effect.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention. The scope of protection of the present invention should be determined by the claims.

Claims

1. A chlorophyll copper-doped anhydrous guanine microsheet, characterized in that: The anhydrous guanine microsheet is a mixture of α and β phases, preferentially exposing the high refractive index (100) surface, with chlorophyll copper molecules embedded in the lattice of the anhydrous guanine crystal; the chlorophyll copper-doped anhydrous guanine microsheet has a weakening effect on incident horizontally and vertically polarized light. The anhydrous guanine microsheets are prepared using industrial anhydrous guanine as raw material according to the following method: The first step is to prepare a sodium salt solution of guanine; The second step is to prepare a dispersion. The specific method is to mix and dissolve formamide, polymer additives, small molecule additives, water and copper chlorophyllin in a certain proportion to prepare a dispersion. The third step is to add the sodium guanine salt solution prepared in the first step to the dispersion prepared in the second step, and stir to mix thoroughly to obtain a mixture. The fourth step involves allowing the mixture obtained in the third step to stand at 60°C for 24 hours to obtain a dispersion of chlorophyll copper-doped guanine micron-sized crystals. The fifth step involves repeatedly centrifuging and washing the guanine micron flake dispersion obtained in the fourth step to obtain chlorophyll copper-doped guanine crystal micron flakes.

2. The chlorophyll copper-doped anhydrous guanine microsheet according to claim 1, characterized in that: In the first step, the method for preparing the sodium salt solution of guanine is as follows: it is prepared using industrial anhydrous guanine powder and sodium hydroxide aqueous solution.

3. The chlorophyll copper-doped anhydrous guanine microsheet according to claim 2, characterized in that: The molar ratio of guanine to sodium hydroxide is 1:(3-5), and the concentration of guanine in the resulting solution is 0.05-0.2M, and the concentration of sodium hydroxide is 0.3-0.5M.

4. A chlorophyll copper-doped anhydrous guanine microsheet according to any one of claims 1-3, characterized in that: In the second step, the polymeric additive is a vinylpyrrolidone-based polymer, a copolymer of vinyl acetate and N-vinylpyrrolidone (P(VP-co-VA)); the small molecule additive is uric acid.

5. A chlorophyll copper-doped anhydrous guanine microsheet according to claim 1, characterized in that: In the third step, when the sodium salt solution of guanine is mixed with the dispersion, the ratio of formamide, small molecule additive, high molecule additive and copper chlorophyll is 10:(0.1-20):(1-50):(1-50), and the temperature is RT~60℃.

6. The application of the chlorophyll copper-doped anhydrous guanine microsheet according to any one of claims 1 to 5, characterized in that: The obtained chlorophyll copper-doped anhydrous guanine micron flake crystals were used as pearlescent pigments in coatings, paints, and rubber, and coated on the surface of military items and camouflage nets to simulate the hyperspectral polarization of green vegetation for camouflage effect.

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