Ultraviolet response type photochromic Bi2WO6 nano material, composite film and ceramic material

Abstract

The invention belongs to the technical field of photochromic materials, relates to a Bi2WO6 nano material for photochromism under ultraviolet radiation, an organic / inorganic composite film and a ceramic material, and further discloses a preparation method and a detection method of the Bi2WO6 nano material. According to the invention, a Bi2WO6 nano material is prepared by a hydrothermal method, and a composite membrane and a ceramic material are respectively prepared by spin coating and pressing. The Bi2WO6 nano material, the composite film and the ceramic material disclosed by the invention have relatively good ultraviolet photochromic performance and relatively high photochromic stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of photochromic materials, and relates to a Bi2WO6 nanomaterial for photochromic change under ultraviolet irradiation, an organic / inorganic composite film, and a ceramic material, and further discloses a preparation method and a detection method thereof. Background Art

[0002] Photochromic materials refer to a series of materials that can change color under specific lighting conditions. Generally speaking, photochromism mainly focuses on the reversible color change process, that is, the color can change under certain lighting conditions, and can be reversibly converted to the initial state under other specific conditions (such as light, heat, redox, etc.). Since this reversible color change process can achieve various functions such as display, storage, printing, anti-counterfeiting and encryption, related materials have long been widely concerned by researchers. In particular, in recent years, the application of photochromic soft materials such as gels and functional films in information storage, inkless printing and erasable paper has attracted the interest of many scientific researchers.

[0003] At present, photochromic units mainly include organic color-changing units represented by azobenzene, diarylethenes or spiropyran, and inorganic color-changing units represented by inorganic materials such as polyoxometalates (POM) and transition metal oxides. These two major types of color-changing units each have their own advantages and disadvantages in terms of performance: photochromic materials based on organic color-changing units have fast response speeds and diverse colors, but their stability is still insufficient; while photochromic materials based on inorganic color-changing units have good stability and can withstand multiple cycles of color change and fading, but their response speed is slow and their colors are relatively single. Although inorganic materials have certain advantages over organic materials in terms of stability, many inorganic color-changing units based on metal oxides such as tungsten trioxide have poor solubility and are difficult to disperse well, which limits their application in composite materials.

[0004] In recent years, Bismuth Tungstate (Bi2WO6) has attracted widespread attention from domestic and foreign scholars as a new, high-performance visible light responsive optoelectronic material with the characteristics of non-toxicity, high chemical stability and low cost. Specifically, Bismuth Tungstate has a typical Aurivillius phase, composed of [Bi2O2] 2+ and [WO4] 2- The perovskite layer is connected by oxygen corners and forms a layered structure alternating along the c-axis. The basic unit is [BiO] + -[WO4] 2- -[BiO] +The sandwich structure has infinite channels, which is beneficial to the migration of photo-generated carriers. Under the action of light, electrons in the valence band of the Bi2WO6 material jump to the conduction band on the premise of meeting certain selection rules, forming photo-generated electrons and photo-generated holes in the valence band and conduction band respectively. Some of the photo-generated electrons and photo-generated holes recombine again on the surface and inside of the Bi2WO6 material, and the other part of the photo-generated electrons diffuse to the surface of the Bi2WO6 material and participate in the surface redox reaction process, resulting in the phenomenon of photochromism. In addition, this photochromic reaction of the Bi2WO6 material is reversible. When the light stops, since the photo-generated electrons on the surface of the Bi2WO6 material are exhausted, and the unreacted photo-generated electrons and holes recombine again, the Bi2WO6 material returns to its original color. In recent years, the products developed based on the Bi2WO6 material have been continuously updated, which can not only cope with the changes in various working environments, but also have gradually received extensive research by scientists. Summary of the Invention

[0005] To this end, the technical problem to be solved by the present invention is to provide an ultraviolet-responsive photochromic Bi2WO6 nanomaterial, which can undergo photochromism under ultraviolet irradiation, and further disclose its preparation method;

[0006] The second technical problem to be solved by the present invention is to provide an organic / inorganic composite film with ultraviolet-responsive photochromism, and further disclose its preparation method;

[0007] The third technical problem to be solved by the present invention is to provide a ceramic material with ultraviolet-responsive photochromism, and further disclose its preparation method.

[0008] To solve the above technical problems, the preparation method of an ultraviolet-responsive photochromic Bi2WO6 nanomaterial described in the present invention includes the steps of hydrothermal synthesis reaction using tungstate and bismuth source materials as raw materials in the presence of a surfactant, and collecting the reactants for drying.

[0009] Specifically, the preparation method of the ultraviolet-responsive photochromic Bi2WO6 nanomaterial:

[0010] The tungstate includes at least one of ammonium paratungstate or calcium tungstate; and / or,

[0011] The bismuth source material includes at least one of bismuth nitrate, bismuth chloride or bismuth sulfate; and / or,

[0012] The surfactant includes at least one of cetyltrimethylammonium bromide or polyvinylpyrrolidone;

[0013] Preferably, the molar ratio of the tungstate, surfactant and bismuth source material is 0.1-0.2:0.8-1:1.5-2.5;

[0014] Preferably, the temperature of the hydrothermal synthesis reaction is 120-160 °C, and the reaction time is 10-40 h;

[0015] Preferably, the drying method includes oven drying, freeze drying and spray drying.

[0016] The present invention also discloses an ultraviolet-responsive photochromic Bi2WO6 nanomaterial prepared by the method.

[0017] A method for preparing an ultraviolet-responsive photochromic composite film, comprising the steps of uniformly mixing Bi2WO6 nanomaterial and a crosslinking agent, and coating the mixture on the surface of a substrate;

[0018] Preferably, the Bi2WO6 nanomaterial includes the ultraviolet-responsive photochromic Bi2WO6 nanomaterial, or the ultraviolet-responsive photochromic Bi2WO6 nanomaterial is prepared according to the method described in 2.

[0019] Specifically, for the method for preparing the ultraviolet-responsive photochromic composite film, the crosslinking agent includes PVA;

[0020] Preferably, the mass ratio of the Bi2WO6 nanomaterial to the PVA is 1:2-4;

[0021] Preferably, the substrate includes an FTO glass substrate, an ITO glass substrate and a ceramic substrate;

[0022] Preferably, the coating method in the coating step includes spin coating;

[0023] Preferably, the rotation speed of the spin coating step is 1000-2000 r / min, and the spin coating time is 1-3 s.

[0024] The present invention also discloses an ultraviolet-responsive photochromic composite film prepared according to the method.

[0025] The present invention also discloses a method for preparing an ultraviolet-responsive photochromic ceramic material, including the steps of pressing Bi2WO6 nanomaterial into a mold, and high-temperature sintering the pressed green body;

[0026] Preferably, the Bi2WO6 nanomaterial includes the ultraviolet-responsive photochromic Bi2WO6 nanomaterial, or the ultraviolet-responsive photochromic Bi2WO6 nanomaterial is prepared according to the method.

[0027] Specifically, the preparation method of the ultraviolet-responsive photochromic ceramic material:

[0028] The pressure in the pressing and forming step is 4 - 12 MPa, and the pressure holding time is 1 - 10 min; and / or,

[0029] The temperature in the high-temperature sintering step is 850 - 900 °C, and the sintering time is 20 - 30 h.

[0030] The present invention also discloses an ultraviolet-responsive photochromic ceramic material prepared according to the above method.

[0031] The present invention also discloses the use of the above method for preparing the ultraviolet-responsive photochromic Bi2WO6 nanomaterial or the ultraviolet-responsive photochromic Bi2WO6 nanomaterial for preparing ultraviolet-responsive photochromic products.

[0032] The preparation method of the Bi2WO6 nanomaterial of the present invention uses tungstate and bismuth source materials as raw materials to prepare Bi2WO6 nanomaterials by a hydrothermal method. The Bi2WO6 nanomaterials have photochromic properties under ultraviolet light, and the Bi2WO6 nanomaterials have an ultrathin powder structure. The photochromic properties of the Bi2WO6 nanomaterials have high stability and can be used to prepare downstream products such as photochromic films and photochromic ceramic materials.

[0033] The ultraviolet-responsive photochromic composite film of the present invention is prepared by uniformly dispersing the Bi2WO6 nanomaterials in a cross-linking agent such as PVA and using a coating method including spin coating. The formed organic / inorganic composite film enhances the photochromic properties of the Bi2WO6 nanomaterials. The formed organic-inorganic composite film has the photochromic ability under ultraviolet irradiation and can maintain no fading for 12 h at room temperature.

[0034] The ultraviolet-responsive photochromic composite film of the present invention uses the common synthetic polymer material polyvinyl alcohol (PVA) as the coating matrix. Due to its good solubility and film-forming properties, it can effectively protect and stabilize the photochromic material and extend its service life. The ultraviolet-responsive photochromic composite film of the present invention has a gentle gradient of pore size change in the composite film prepared by spin coating, more uniform dispersion of the material, and better photochromic properties.

[0035] The ultraviolet-responsive photochromic ceramic material of the present invention is formed by pressing and shaping the Bi2WO6 nanomaterials. The ceramic material has the photochromic ability under ultraviolet irradiation, can maintain no fading for 12 h at room temperature, and has stable photochromic properties. The ceramic material of the present invention has characteristics such as high melting point, high hardness, high wear resistance, and oxidation resistance, and can better cope with different working environments.

[0036] When the ultraviolet-responsive photochromic composite film and the ultraviolet-responsive photochromic ceramic material of the present invention are subjected to ultraviolet performance detection, by controlling the irradiation conditions of the incident light and observing whether the colors of the composite film and the ceramic sheet change, it can be detected whether there is ultraviolet light in the incident light. For the composite film and the ceramic material of the present invention, under the full spectrum, the colors of the film to be tested and the ceramic sheet to be tested change from white to black, while the film to be tested and the ceramic sheet to be tested under the irradiation of a xenon lamp with an ultraviolet cut-off filter do not change in color, which fully proves that the prepared composite film and ceramic material have the ability of photochromism under ultraviolet irradiation. More importantly, after the film to be tested and the ceramic sheet to be tested that have undergone photochromism are placed at room temperature for 1 h, it can be observed that the colors of the film to be tested and the ceramic sheet to be tested change from black back to white, indicating the reversibility of the local photochromism of the composite film and the ceramic material.

[0037] The ultraviolet-responsive photochromic composite film and the ultraviolet-responsive photochromic ceramic material of the present invention have good structural stability, not only have good acid and alkali resistance and photochromic properties, especially under the influence of nanoscale particles and uniform surface dispersion, their photochromic properties can be maintained for a long time, and are applicable to various optical devices or ultraviolet prevention devices, and the photochromic cycle stability is remarkable and the service life is long. Description of the Drawings

[0038] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to the specific embodiments of the present invention in combination with the drawings, wherein,

[0039] Figure 1 XRD pattern of the Bi2WO6 nanomaterial prepared in Example 1;

[0040] Figure 2 Pre-detection results of the Bi2WO6 nanomaterial prepared in Example 1;

[0041] [[ID=2X]] Figure 3 Comparison diagram of the bismuth tungstate ceramic sheet prepared in Example 7 before and after illumination (full spectrum), the left side is before illumination and the right side is after illumination;

[0042] Figure 4 Comparison diagram of the bismuth tungstate ceramic sheet prepared in Example 7 before and after illumination (visible light), the left side is before illumination and the right side is after illumination;

[0043] Figure 5 Ultraviolet-visible absorption spectrum detection results of the Bi2WO6 ceramic sheet prepared in Example 7 before and after illumination;

[0044] Figure 6The photochromic reversibility test curve results of the Bi2WO6 ceramic sheet prepared in Example 7;

[0045] Figure 7 This is a comparison of the Bi2WO6 composite film prepared in Example 4 before and after illumination (full spectrum), with the left side showing before illumination and the right side showing after illumination;

[0046] Figure 8 This is a comparison of the ceramic sheet prepared in Example 10 before and after irradiation (visible light), with the left side showing before irradiation and the right side showing after irradiation;

[0047] Figure 9 This is a comparison diagram of the ceramic sheet prepared in Example 11 before and after irradiation (visible light), with the left side being before irradiation and the right side being after irradiation. DETAILED DESCRIPTION

[0048] In the following embodiments of the present invention, an ultrathin Bi2WO6 nanopowder is prepared based on a hydrothermal synthesis method by selecting suitable raw materials, and an organic-inorganic composite film is prepared by fully mixing the Bi2WO6 nanomaterial with PVA by spin coating, and a ceramic material is prepared by pressing the Bi2WO6 nanomaterial into sheets and then sintering them at high temperature to form porcelain, further expanding the products in the field of ultraviolet-responsive photochromism.

[0049] Example 1

[0050] In this embodiment, the Bi2WO6 ultrathin nanopowder is prepared.

[0051] First, 380 mg of ammonium paratungstate ((NH4) 10 (H2W 12 O 42 Dissolve 320 mg of cetyltrimethylammonium bromide (CTAB) in deionized water, stir thoroughly until completely dissolved, and let stand for 30 minutes before use. Add 972 mg of bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) to the solution and stir continuously for 1 hour to form a milky white suspension.

[0052] The suspension was transferred to a 100 mL polytetrafluoroethylene-lined autoclave, sealed in a stainless steel jacket, and incubated at 140°C for 24 hours. After the incubation period, the autoclave was cooled to room temperature, centrifuged, and washed several times with deionized water and ethanol to collect the precipitate. The precipitate was then dried in a forced air drying oven at 60°C for 10 hours to obtain the desired Bi2WO6 ultrathin nanosheet powder.

[0053] The XRD pattern of the Bi2WO6 nanomaterial prepared in this embodiment is shown in the attached figure. Figure 1 As shown, it can be seen that the product synthesized in this embodiment is accurate.

[0054] Example 2

[0055] In this example, the Bi2WO6 ultrathin nanometer powder was prepared.

[0056] First, 380 mg of ammonium paratungstate ((NH4) 10 (H2W 12 O 42 )·4H2O) and 320 mg of cetyltrimethylammonium bromide (CTAB) were dissolved in deionized water, and stirred thoroughly until completely dissolved, then left standing for 30 min for later use. Separately, 927 mg of bismuth nitrate pentahydrate (Bi(NO3)3·5H2O) was added to the above solution, and after continuous stirring for 1 h, a milky white suspension was formed.

[0057] The suspension was transferred to the inner lining of a 100 mL polytetrafluoroethylene high-pressure hydrothermal autoclave and sealed in a stainless steel sleeve, and kept at 120 °C for reaction for 30 h. After the heat preservation ended, when the autoclave cooled to room temperature, it was centrifuged and washed several times with deionized water and ethanol, and the precipitate was collected. The above precipitate was placed in a blast drying oven and dried at 50 °C for 12 h to obtain the required Bi2WO6 ultrathin nanosheet powder.

[0058] Example 3

[0059] In this example, the Bi2WO6 ultrathin nanometer powder was prepared.

[0060] First, 380 mg of ammonium paratungstate ((NH4) 10 (H2W 12 O 42 )·4H2O) and 280 mg of cetyltrimethylammonium bromide were dissolved in deionized water, and stirred thoroughly until completely dissolved, then left standing for 30 min for later use. Separately, 600 mg of bismuth chloride (BiCl3) was added to the above solution, and after continuous stirring for 1 h, a milky white suspension was formed.

[0061] The suspension was transferred to the inner lining of a 100 mL polytetrafluoroethylene high-pressure hydrothermal autoclave and sealed in a stainless steel sleeve, and kept at 140 °C for reaction for 20 h. After the heat preservation ended, when the autoclave cooled to room temperature, it was centrifuged and washed several times with deionized water and ethanol, and the precipitate was collected. The above precipitate was placed in a freeze dryer and dried for 8 h to obtain the required Bi2WO6 ultrathin nanosheet powder.

[0062] Example 4

[0063] In this example, the required ultraviolet-responsive photochromic composite film was prepared based on the Bi2WO6 nanomaterial prepared in Example 1.

[0064] Take 3 g of polytetrafluoroethylene (PVA) and add it to 100 mL of deionized water. Stir it in a water bath at 80 °C until the PVA is completely dissolved. After the obtained solution is cooled to room temperature, a PVA crosslinking agent is obtained.

[0065] Cut 4 pieces of 8*8 mm FTO glass substrates and ultrasonically clean them several times with distilled water and ethanol solution respectively. Place them in a blast drying oven and dry them at 60 °C for later use.

[0066] Add 500 mg of Bi2WO6 nanomaterial to 5 mL of the PVA crosslinking agent, stir well, and then ultrasonically treat it with deionized water for 30 min to obtain a milky white transparent solution, which is the spin coating solution.

[0067] Fix the treated FTO glass substrates on a spin coater, and use a 100 μL pipette gun to evenly drop the spin coating solution on the FTO glass substrates.

[0068] Turn on the spin coater and spin coat at a speed of 1500 r / min for 2 s to obtain the product.

[0069] Example 5

[0070] This example is based on the Bi2WO6 nanomaterial prepared in Example 2 to prepare the required ultraviolet-responsive photochromic composite film.

[0071] Take 3 g of polytetrafluoroethylene (PVA) and add it to 100 mL of deionized water. Stir it in a water bath at 80 °C until the PVA is completely dissolved. After the obtained solution is cooled to room temperature, a PVA crosslinking agent is obtained.

[0072] Cut 4 pieces of 8*8 mm FTO glass substrates and ultrasonically clean them several times with distilled water and ethanol solution respectively. Place them in a blast drying oven and dry them at 60 °C for later use.

[0073] Add 750 mg of Bi2WO6 nanomaterial to 5 mL of the PVA crosslinking agent, stir well, and then ultrasonically treat it with deionized water for 30 min to obtain a milky white transparent solution, which is the spin coating solution.

[0074] Fix the treated FTO glass substrates on a spin coater, and use a 100 μL pipette gun to evenly drop the spin coating solution on the FTO glass substrates.

[0075] Turn on the spin coater and spin coat at a speed of 1000 r / min for 3 s to obtain the product.

[0076] Example 6

[0077] This example is based on the Bi2WO6 nanomaterial prepared in Example 3 to prepare the required ultraviolet-responsive photochromic composite film.

[0078] 5 g of polyvinylidene fluoride (PVDF) was added to 100 mL of deionized water and stirred in a water bath at 80° C. until the PVDF was completely dissolved. The resulting solution was cooled to room temperature to obtain a PVDF crosslinker.

[0079] Four 8*8 mm ITO glass substrates were cut and ultrasonically cleaned several times with distilled water and ethanol solution respectively, and dried at 60° C. in a forced air drying oven for later use.

[0080] 300 mg of Bi2WO6 nanomaterials were added to 5 mL of PVA crosslinker and stirred thoroughly, and then ultrasonically treated with deionized water for 30 min to obtain a milky white transparent solution, which was the spin coating solution.

[0081] The treated ITO glass substrate was fixed on a spin coater, and the spin coating liquid was evenly dropped on the ITO glass substrate using a 100 μL pipette.

[0082] Turn on the spin coater and spin coat at a speed of 2000 r / min for 1 s.

[0083] Example 7

[0084] This embodiment prepares the required ultraviolet-responsive photochromic ceramic sheet based on the Bi2WO6 nanomaterial prepared in Example 1.

[0085] A 0.75g sample of Bi2WO6 powder was weighed and pressed into a sheet at 10MPa for 2 minutes. The resulting nanosheet was placed in a crucible filled with alumina powder and sintered in a muffle furnace at 900°C for 24 hours to produce a Bi2WO6 ceramic sheet.

[0086] Example 8

[0087] This embodiment prepares the required ultraviolet-responsive photochromic ceramic sheet based on the Bi2WO6 nanomaterial prepared in Example 2.

[0088] A 1g sample of Bi2WO6 powder was weighed and pressed into a sheet at 8MPa for 3 minutes. The resulting nanosheet was placed in a crucible filled with alumina powder and sintered in a muffle furnace at 850°C for 30 hours to produce a Bi2WO6 ceramic sheet.

[0089] Example 9

[0090] This embodiment prepares the required ultraviolet-responsive photochromic ceramic sheet based on the Bi2WO6 nanomaterial prepared in Example 3.

[0091] Weigh 1 g of the Bi2WO6 powder sample and press it into a tablet under the conditions of 12 MPa pressure and holding pressure for 1 min. Put the obtained nanosheet into a crucible filled with alumina powder and sinter it in a muffle furnace at 870 °C for 20 h to obtain a Bi2WO6 ceramic sheet.

[0092] Example 10

[0093] The preparation method of the Bi2WO6 nanomaterial described in this example is the same as that in Example 1, except that sodium tungstate is selected as the tungstate.

[0094] Based on the Bi2WO6 nanomaterial prepared above, the color-changing film is prepared according to the method in Example 4.

[0095] Based on the Bi2WO6 nanomaterial prepared above, the ceramic product is prepared according to the method in Example 7.

[0096] Example 11

[0097] The preparation method of the Bi2WO6 nanomaterial described in this example is the same as that in Example 1, except that sodium dodecyl sulfate is selected as the surfactant.

[0098] Based on the Bi2WO6 nanomaterial prepared above, the color-changing film is prepared according to the method in Example 4.

[0099] Based on the Bi2WO6 nanomaterial prepared above, the ceramic product is prepared according to the method in Example 7.

[0100] Experimental Example

[0101] 1. Preliminary detection of the photochromism of Bi2WO6 nanomaterial under ultraviolet irradiation

[0102] Take 25 mg of Bi2WO6 nanometer powder material (Example 1) and add it to 30 mL of ethylene glycol solution, stir and mix, and ultrasonically treat the above solution with distilled water for 30 min. Place the above solution in a quartz sealed reactor and vacuum treat it for 10 minutes.

[0103] Irradiate it with a 300 w full-spectrum xenon lamp (CEL-HXF300) for 20 minutes respectively. The preliminary detection results of the Bi2WO6 nanomaterial are as shown in the appendix Figure 2 as follows.

[0104] Under the full-spectrum irradiation, the solution changes from milky white to black, while under the irradiation of the xenon lamp with an ultraviolet cut-off filter, the color of the solution does not change. It shows that the Bi2WO6 nanomaterial prepared by the present invention has the ability of photochromism under ultraviolet irradiation.

[0105] 2. Detection of the photochromic ceramic sheet of Bi2WO6 nanomaterial under ultraviolet irradiation

[0106] Take the Bi2WO6 ceramic sheet prepared in Example 7, and evenly drop ethylene glycol solution with a 100 μL pipette. After standing for 5 min, it is recorded as the ceramic sheet to be tested.

[0107] Place the ceramic sheet to be tested on a 90 mL drying dish, and irradiate it with a 300 w full-spectrum xenon lamp (CEL-HXF300) for 20 minutes. The detection results of the photochromic ceramic sheet of Bi2WO6 nanomaterial are as shown in the appendix Figures 3-4 as follows.

[0108] As shown in the appendix Figure 3 as the result shows, after turning off the xenon lamp, it can be seen that the color of the ceramic sheet to be tested changes from white to black under the full spectrum. And as Figure 4 shown, the ceramic sheet to be tested under the irradiation of the xenon lamp with an ultraviolet cut-off filter does not change color. It shows that the Bi2WO6 ceramic sheet prepared by the present invention has the ability of photochromism under ultraviolet irradiation.

[0109] In this experimental example, the detection results of the ultraviolet-visible absorption spectrum of the Bi2WO6 ceramic sheet before and after light irradiation are as shown in the appendix Figure 5 as follows. After light irradiation, due to the color change of the material, the light absorption of the Bi2WO6 ceramic sheet in the infrared band is significantly enhanced.

[0110] Furthermore, after the photochromic ceramic sheet to be tested that has already undergone photochromism is placed at room temperature for 1 h, it can be observed that the color of the ceramic sheet to be tested changes from black back to white again, indicating the reversibility of photochromism.

[0111] In this experimental example, the test curve results of the photochromic reversibility of the Bi2WO6 ceramic sheet are as shown in the appendix Figure 6 as follows. The ceramic sheet still has the property of light color change after multiple light irradiations and fade-outs, indicating that the material we prepared has the characteristic of reusable.

[0112] 3. Detection of the photochromic film of Bi2WO6 nanomaterial under ultraviolet irradiation

[0113] Take an FTO glass sheet loaded with a photochromic film of Bi2WO6 nanomaterial (Example 7), and evenly drop ethylene glycol solution with a 100 μL pipette. After standing for 5 min, it is recorded as the film to be tested.

[0114] Place the film to be tested on a 90 mL drying dish, and irradiate it with a full-spectrum xenon lamp and a xenon lamp with an ultraviolet cut-off filter for 20 minutes. The detection results of the photochromic film of Bi2WO6 nanomaterial are as shown in the appendix Figure 7 .

[0115] After turning off the xenon lamp, it can be seen that the color of the film to be measured under the full spectrum changes from white to black. In addition, the color of the film to be measured under the irradiation of the xenon lamp with an ultraviolet cut-off filter does not change. It shows that the prepared PVA / Bi2WO6 nanomaterial film has the ability of photochromism under ultraviolet irradiation.

[0116] Furthermore, after placing the film to be measured that has undergone photochromism at room temperature for 1 h, it can be observed that the color of the film to be measured changes from black back to white again, indicating the reversibility of photochromism.

[0117] 4. Detection of Bi2WO6 nanomaterial photochromic ceramic chips under ultraviolet irradiation

[0118] According to the operation methods of Experimental Example 2 above, the ceramic materials prepared in Examples 10 and 11 were respectively taken for color change detection, and the results are shown in the appendix Figure 8 and 9 as shown.

[0119] It can be seen that, for example, in the scheme of Example 10, sodium tungstate is used as the raw material to prepare the required Bi2WO6 nanomaterial, and the color change effect of the prepared ceramic material is not obvious. While in the scheme of Example 11, sodium dodecyl sulfate is used as the surfactant to prepare the required Bi2WO6 nanomaterial, and the color change effect of the prepared ceramic material is uneven.

[0120] In summary, the preparation method of the Bi2WO6 nanomaterial of the present invention uses tungstate and bismuth source materials as raw materials to prepare Bi2WO6 nanomaterials by hydrothermal method. The Bi2WO6 nanomaterials have photochromic properties under ultraviolet light, and the Bi2WO6 nanomaterials have an ultra-thin powder structure. The photochromic properties of the Bi2WO6 nanomaterials have high stability and can be used to prepare downstream products such as photochromic films and photochromic ceramic materials.

[0121] The ultraviolet-responsive photochromic composite film and the ultraviolet-responsive photochromic ceramic material of the present invention have the ability of photochromism under ultraviolet irradiation, and can remain unfaded at room temperature for 12 h, have stable photochromic properties, and have high application performance.

[0122] Obviously, the above embodiments are only examples clearly described and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A preparation method of an ultraviolet-responsive photochromic Bi2WO6 nanomaterial, characterized in that, It includes the steps of using tungstate and bismuth source materials as raw materials to conduct a hydrothermal synthesis reaction in the presence of a surfactant, and collecting the reactants for drying.

2. The method for preparing the ultraviolet-responsive photochromic Bi2WO6 nanomaterial according to claim 1, wherein: The tungstate includes at least one of ammonium paratungstate or calcium tungstate; and / or, The bismuth source material includes at least one of bismuth nitrate, bismuth chloride or bismuth sulfate; and / or, The surfactant includes at least one of cetyltrimethylammonium bromide or polyvinylpyrrolidone; Preferably, the molar ratio of the tungstate, surfactant and bismuth source material is 0.1-0.2:0.8-1:1.5-2.5; Preferably, the temperature of the hydrothermal synthesis reaction is 120-160 °C, and the reaction time is 10-40 h; Preferably, the drying method includes oven drying, freeze drying and spray drying.

3. An ultraviolet-responsive photochromic Bi2WO6 nanomaterial prepared by the method according to claim 1 or 2.

4. A method for preparing an ultraviolet-responsive photochromic composite film, characterized in that, It includes the step of uniformly mixing the Bi2WO6 nanomaterial with a crosslinking agent, and the step of coating the mixed solution on the surface of the substrate; Preferably, the Bi2WO6 nanomaterial includes the ultraviolet-responsive photochromic Bi2WO6 nanomaterial according to claim 3, or the ultraviolet-responsive photochromic Bi2WO6 nanomaterial is prepared by the method according to claim 1 or 2.

5. The preparation method of the ultraviolet-responsive photochromic composite film according to claim 4, characterized in that, The crosslinking agent includes PVA; Preferably, the mass ratio of the Bi2WO6 nanomaterial to the PVA is 1:2-4; Preferably, the substrate includes an FTO glass substrate, an ITO glass substrate and a ceramic substrate; Preferably, the coating method of the coating step includes spin coating; Preferably, the rotation speed of the spin coating step is 1000-2000 r / min, and the spin coating time is 1-3 s.

6. An ultraviolet-responsive photochromic composite film prepared by the method according to claim 4 or 5.

7. A preparation method of an ultraviolet-responsive photochromic ceramic material, characterized in that, It includes the step of compacting the Bi2WO6 nanomaterial, and the step of performing high-temperature sintering on the compacted green body; Preferably, the Bi2WO6 nanomaterial includes the ultraviolet-responsive photochromic Bi2WO6 nanomaterial according to claim 3, or the ultraviolet-responsive photochromic Bi2WO6 nanomaterial is prepared by the method according to claim 1 or 2.

8. The method for preparing the ultraviolet-responsive photochromic ceramic material according to claim 7, wherein: The pressure of the compacting step is 4-Intensity 12 MPa, and the pressure holding time is 1-10 min; and / or, The temperature of the high-temperature sintering step is 850-900 °C, and the sintering time is 20-30 h.

9. An ultraviolet-responsive photochromic ceramic material prepared by the method according to claim 7 or 8.

10. The use of the ultraviolet-responsive photochromic Bi2WO6 nanomaterial prepared by the method according to claim 1 or 2 or the ultraviolet-responsive photochromic Bi2WO6 nanomaterial according to claim 3 for preparing an ultraviolet-responsive photochromic product.

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