Bimetallic co-doped layered oxide thin films, methods of preparation, and holographic encryption applications

Abstract

The application provides a double-metal co-doped laminated oxide film, which comprises: a mesoporous TiO2 film on a glass substrate; Au-Ag blended nanoparticles deposited on the mesoporous TiO2 film; amorphous TaO x x is a positive number; a silver film on the amorphous TaO x x is a positive number; a silver film on the amorphous TaO The application also provides an encrypted holographic storage method, which comprises: performing one-time exposure on a first region and two-time exposure on a second region of the double-metal co-doped laminated oxide film by using a pulse laser; holographic storage; NaCl solution brushing; and reading the first region or the second region for holographic storage data. The laminated oxide film is simple in preparation process and easy to operate, and an encrypted holographic storage method is creatively provided; the film can also be used in the field of color printing, and the application range and field of the metal and TiO2 composite film are widened.

Description

Technical Field

[0001] This invention relates to the field of optical data storage and encryption technology, specifically to bimetallic co-doped multilayer oxide thin films, their preparation methods, and holographic encryption applications. Background Technology

[0002] Holographic technology can record and reproduce all the information of an object, allowing observers to obtain the outline and depth information of a real object without the naked eye. Therefore, it has broad application prospects in entertainment, education, medical care, and especially in the field of information anti-counterfeiting, and has received widespread attention from the industry.

[0003] At the same time, with the development of the digital industry, people's demand for personal information security is becoming increasingly strong, and information privacy protection is receiving more and more attention in modern society. Data encryption is crucial for information protection, and the development of new encryption technologies has become a key force in promoting the progress of the information society.

[0004] Therefore, realizing holographic and encryption technologies within the same system is particularly important. In recent years, composite thin films of metals and TiO2 have gradually achieved stable and rapid holographic storage. However, due to their limited photoelectric properties, their application scope is difficult to expand, and there is currently no research on encrypted storage applications of this system. In view of this, it is necessary to design a composite thin film capable of encrypted holographic storage, its preparation method, and a holographic encrypted storage method based on it. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a bimetallic co-doped multilayer oxide thin film, its preparation method, and its holographic encryption application.

[0006] The technical solution adopted by this invention to solve the technical problem is as follows:

[0007] In a first aspect, the present invention provides a bimetallic co-doped multilayer oxide thin film, comprising:

[0008] Glass substrate;

[0009] Mesoporous TiO2 film located on the glass substrate;

[0010] Au-Ag blend nanoparticles deposited on mesoporous TiO2 films;

[0011] Amorphous TaO on Au-Ag blend nanoparticles x Thin film layer, where x is a positive number;

[0012] Located in the amorphous TaO x The silver film on the thin film layer.

[0013] In a preferred embodiment, the amorphous TaO xThe thickness of the thin film layer is 35–45 nm; the thickness of the silver film is 15–20 nm.

[0014] In a second aspect, the present invention provides a method for preparing a bimetallic co-doped multilayer oxide thin film as described in the first aspect, comprising:

[0015] S1. A layer of TiO2 paste is coated on a glass substrate by screen printing, and then subjected to thermal annealing to remove organic components, thereby obtaining the mesoporous TiO2 film.

[0016] S2. A layer of gold nanoparticles is deposited on the surface of the mesoporous TiO2 film by magnetron sputtering;

[0017] S3. Immerse the TiO2 film with gold nanoparticles deposited in silver nitrate solution and irradiate it with ultraviolet light to achieve the deposition of silver nanoparticles and form the Au-Ag blended nanoparticle layer.

[0018] S4. Using a Czochralski (C-P) apparatus, amorphous TaO is coated onto the Au-Ag blend nanoparticle layer via a C-P coating method. x The amorphous TaO was obtained by heat treatment of the layer. x Thin film layer;

[0019] S5, in the amorphous TaO x A continuous silver film is magnetron sputtered onto the thin film layer.

[0020] In a preferred embodiment, the specific process of S1 is as follows: placing a glass substrate under the screen of a screen printing machine, scraping a layer of TiO2 slurry onto the upper surface of the glass substrate with a scraper, and then placing the glass substrate in a muffle furnace for annealing to remove the polymer in the TiO2 slurry to obtain the mesoporous TiO2 film.

[0021] The specific process of S2 is as follows: open the argon main valve of the gas cylinder, adjust the pressure reducing valve to make the output gas pressure 0.035-0.045 MPa, load the gold target, and use tweezers to place the mesoporous TiO2 film obtained in S1 into a magnetron sputtering instrument to sputter gold, deposit a layer of gold nanoparticles on the surface of the mesoporous TiO2 film, and obtain a mesoporous TiO2 film with gold nanoparticles deposited.

[0022] The specific process of S3 is as follows: the mesoporous TiO2 film with gold nanoparticles deposited is immersed in a 0.5 mol / L silver nitrate solution, the liquid level of the silver nitrate solution is higher than the mesoporous TiO2 film with gold nanoparticles deposited in it, and ultraviolet light is irradiated for 5 minutes to achieve the deposition of silver nanoparticles and obtain the Au-Ag blend nanoparticles.

[0023] The specific process of S4 is as follows: the Au-Ag blended nanoparticles obtained in S3 are placed in TaO.x TaO was prepared on Au-Ag blended nanoparticle layers via dip-coating in a precursor sol. x During the thin film dipping process, the glass substrate rises and falls at a speed of 0.35 cm / s, and is immersed in TaO. x The precursor sol was applied for 6 seconds, and after impregnation, it was suspended vertically to the ground for 3 minutes, followed by heat treatment at 160°C for 30 minutes.

[0024] The specific process of S5 is as follows: open the argon main valve of the gas cylinder, adjust the pressure reducing valve to make the output gas pressure 0.035-0.045 MPa, load the silver target, use tweezers to place the film obtained in S4 into the magnetron sputtering instrument, sputter silver to obtain a continuous silver film, and the preparation of the bimetallic co-doped multilayer oxide film is completed.

[0025] In a preferred embodiment, annealing the glass substrate in a muffle furnace specifically involves: annealing the glass substrate in a muffle furnace at 500°C for 1 hour; sputtering gold for 5 seconds; sputtering silver for 20 seconds; and using a magnetron sputtering current of 30 mA.

[0026] Thirdly, the present invention provides the application of a bimetallic co-doped multilayer oxide thin film as described in the first aspect as an encrypted holographic storage material.

[0027] Fourthly, the present invention provides an encrypted holographic storage method, comprising:

[0028] Obtain a bimetallic co-doped multilayer oxide thin film as described in the first aspect;

[0029] The N first regions and M second regions on the bimetallic co-doped multilayer oxide film are exposed once using a pulsed laser, and the first and second regions do not overlap. N and M are both integers greater than 0.

[0030] The information to be encrypted and stored is divided into M parts, and holographically stored in M ​​second regions in a one-to-one correspondence, while interference information is stored in the first regions; or the information to be encrypted and stored is divided into N parts, and holographically stored in N first regions in a one-to-one correspondence, while interference information is stored in the second regions.

[0031] The first region and the second region are distinguished by brushing the bimetallic co-doped multilayer oxide film with NaCl solution. The first region and the second region after brushing with NaCl solution have different colors.

[0032] Read data from the first region or the second region for holographic storage;

[0033] The information read from the first region or the second region will be spliced ​​together.

[0034] In a preferred embodiment, the first region and the second region have the same shape.

[0035] In a preferred embodiment, the pulsed laser is an infrared laser with a power of 10W, a laser moving linear speed of 1000mm / s, a spacing of 0.1mm between two adjacent laser lines, and a pulse repetition frequency of 20kHz.

[0036] The beneficial effects of this invention are:

[0037] This invention provides "silver film, amorphous TaO" x The preparation process of the "thickened oxide film consisting of thin film layer, Au-Ag blended nanoparticle layer, and mesoporous TiO2 film" is simple and easy to operate. The thickened oxide film was obtained by combining screen printing, dip-coating, magnetron sputtering, ultraviolet deposition and high temperature annealing.

[0038] This invention integrates pulsed laser processing, NaCl solution brushing, and continuous laser holographic recording to achieve information steganography and holographic reconstruction of specific points using stacked oxide thin films. This invention proposes an encrypted holographic storage method based on the thin film of this invention, which realizes encrypted holographic storage and encrypted information acquisition. Attached Figure Description

[0039] Figure 1 This is a structural diagram of a bimetallic co-doped multilayer oxide thin film.

[0040] Figure 2 This is a flowchart illustrating the preparation process of a bimetallic co-doped multilayer oxide thin film.

[0041] Figure 3 These are scanning electron microscope images before and after applying NaCl solution to the surface of a silver film using a brush.

[0042] Figure 4 This is a scanning electron microscope image of the silver film after a second low-energy-density exposure.

[0043] Figure 5 The absorption spectra of the silver film on the outermost surface of the stacked oxide film after one and two low-energy-density exposures before and after brush coating with NaCl solution are shown.

[0044] Figure 6 This is an example of a physical object obtained by combining pulsed laser processing and NaCl solution brushing.

[0045] Figure 7 The absorption spectra of the Au-Ag co-doped system before and after the introduction of Au particles.

[0046] Figure 8 A schematic diagram illustrating how to achieve address hiding and reproduction of real information.

[0047] Figure 9 Scanning electron microscope images and color maps of silver films after pulsed laser treatment with one to three exposures.

[0048] Figure 10 This is a schematic diagram showing different thin film colors achieved without laser irradiation. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0050] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0052] Example 1

[0053] This embodiment provides a bimetallic co-doped multilayer oxide thin film, such as... Figure 1 It includes: a glass substrate; a mesoporous TiO2 film 2 on the glass substrate 1; Au-Ag blend nanoparticles 3 deposited on the mesoporous TiO2 film 2; and amorphous TaO2 on the Au-Ag blend nanoparticles 3. x Thin film layer; located in the amorphous TaO x Silver film 5 on thin film layer 4; x is a positive number.

[0054] Understandably, the oxidation state of tantalum can be +3, +4, or +5, and the corresponding tantalum oxides can be tantalum dioxide (x = 2), tantalum trioxide (x = 3 / 2), tantalum pentoxide (x = 5 / 2), or amorphous TaO. x Thin film layer 4 may include some or all of tantalum dioxide, tantalum trioxide, and tantalum pentoxide. Since +5 is the most common valence of tantalum, amorphous TaO... x Thin film layer 4 typically includes tantalum pentoxide. In addition, +3 valence is also common, so it is very likely to include tantalum trioxide.

[0055] Understandably, if the Au-Ag blended nanoparticles 3 fail to completely cover the upper surface of the mesoporous TiO2 film 2, then the amorphous TaO... xThe thin film layer 4 can cover the area on the upper surface of the mesoporous TiO2 thin film 2 that is not covered by the Au-Ag blended nanoparticles 3.

[0056] Example 2

[0057] This embodiment provides a method for preparing a bimetallic co-doped multilayer oxide thin film, such as... Figure 2 It includes the following steps:

[0058] S1. A TiO2 film is prepared on a glass substrate 1 by screen printing. The TiO2 film is then subjected to thermal annealing to obtain a mesoporous TiO2 film 2.

[0059] The annealing process specifically involves annealing at 500°C for 1 hour.

[0060] The specific process of S1 is as follows: Take a clean glass substrate 1, take TiO2 slurry, place the glass substrate 1 under the screen of a screen printing machine, coat the TiO2 slurry on the screen, and scrape a layer of TiO2 slurry onto the glass substrate 1 with a scraper to obtain a TiO2 slurry film. Then, place the TiO2 slurry film in a muffle furnace and anneal at 500°C for 1 hour to remove the polymer in the TiO2 slurry and obtain a mesoporous TiO2 film 2.

[0061] S2. A layer of gold nanoparticles is deposited on the surface of a mesoporous TiO2 thin film 2 by magnetron sputtering.

[0062] The specific process of S2 is as follows: open the main valve of the argon gas cylinder, adjust the pressure reducing valve to make the output gas pressure 0.035-0.045 MPa, load the gold target, and use tweezers to place the mesoporous TiO2 film 2 obtained in S1 into the magnetron sputtering instrument, run the program to sputter gold, and in this embodiment, the specific time is selected as 5s. A layer of gold nanoparticles is deposited on the surface of the mesoporous TiO2 film 2 to obtain a mesoporous TiO2 film with gold nanoparticles deposited.

[0063] S3. Immerse the mesoporous TiO2 film with gold nanoparticles deposited in silver nitrate solution, and irradiate the mesoporous TiO2 film with gold nanoparticles deposited and the silver nitrate solution with ultraviolet light. Silver nanoparticles are deposited on the film to obtain Au-Ag blended nanoparticles 3, that is, the mesoporous TiO2 film with Au-Ag blended nanoparticles 3 deposited is obtained.

[0064] The specific process of S3 is as follows: Weigh 4.25g of silver nitrate (AgNO3) solid particles, dissolve them in 49mL of pure water, stir, and after stirring evenly, add 1mL of anhydrous ethanol, and after stirring evenly, obtain a 0.5mol / L silver nitrate solution; place the film obtained in S2 horizontally in a petri dish, pour the silver nitrate solution into the petri dish, and make sure that the film obtained in S2 is completely immersed in the silver nitrate solution; irradiate the mesoporous TiO2 film with gold nanoparticles deposited and the silver nitrate solution immersed in the film with ultraviolet light to achieve the deposition of silver nanoparticles on the film surface; after 5min of deposition, Au-Ag blended nanoparticles 3 are obtained.

[0065] S4. Amorphous TaO was coated onto the Au-Ag blend nanoparticle layer using a Czochralski method. x A layer (approximately 40 nm thick) was heat-treated to obtain amorphous TaO. x Thin film layer 4;

[0066] The heat treatment was performed for 30 minutes at a temperature of 160℃.

[0067] The amorphous TaO x The thickness of thin film layer 4 is 35-45 nm, and in this embodiment it is 40 nm.

[0068] The specific process of S4 is as follows: Take the thin film prepared in S3, and place the thin film in TaO. x Specifically, tantalum pentoxide precursor sol was used in the precursor sol, and TaO was prepared on a glass substrate 1Au-Ag blend nanoparticle layer by dip-coating method. x During the thin film dip-coating process, the rising and falling speeds of the glass substrate 1 are both 0.35 cm / s, and the immersion speed of the TaO film is... x The precursor sol was applied for 6 seconds. After impregnation, the film was suspended vertically for 3 minutes (perpendicular to the ground). Then, the film was removed and placed in a muffle furnace for heat treatment at 160°C for 30 minutes.

[0069] S5, in amorphous TaO x A continuous silver film 5 is magnetron sputtered on the thin film layer 4.

[0070] The thickness of the silver film 5 is 15-20 nm, and in this embodiment, the thickness of the silver film 5 is 17 nm.

[0071] The sputtering conditions are as follows: magnetron sputtering current is 30mA, and sputtering interval is 20s.

[0072] The specific process of S5 is as follows:

[0073] Open the argon main valve of the gas cylinder, adjust the pressure reducing valve to bring the output gas pressure to 0.035-0.045 MPa, load the silver target, and use tweezers to place the thin film obtained in S4 into the magnetron sputtering instrument. Run the program to sputter silver for 20 seconds on amorphous TaO. x A layer of silver nanoparticles is deposited on the surface of thin film layer 4 to obtain continuous silver film 5. Thus, the preparation of a bimetallic co-doped stacked oxide thin film is completed.

[0074] This preparation method combines screen printing and high-temperature annealing to obtain mesoporous oxide films, and uses magnetron sputtering combined with ultraviolet irradiation to obtain all metal parts. The preparation process is simple and easy to operate.

[0075] Example 3

[0076] This embodiment provides a bimetallic co-doped multilayer oxide thin film that can be used as an encrypted holographic storage material and applied in the field of encrypted holographic storage.

[0077] Typically, laser processing relies on the transient thermal energy and focusing position of the laser beam. When the silver film 5 is irradiated with an infrared laser (1064 nm, 100 ns pulse width), the film is heated due to the collective resonance mode of the interconnected silver nanoparticles constituting the film. The silver film 5 melts, and silver atoms in the film migrate to form large particles. However, the instantaneous thermal energy of the laser beam has limited ability to fine-tune the morphology of metal nanoparticles. In contrast, chemical solution reactions are relatively slow and moderate processes, and their ability to adjust particle size and spacing is closely related to reaction time and solution concentration. Furthermore, by using continuous lasers, including continuous lasers of different wavelengths or polarization states, plasmon resonance of the Au-Ag noble metal in the interlayer can be induced by coherent light, and photogenerated electrons can transfer to the oxide under the drive of the electric field at the upper and lower interfaces, thus allowing for the manipulation of metal nanoparticles of different shapes and sizes. By combining the three methods, through the integrated application of laser processing and NaCl solution brushing, the method utilizes the characteristic that the outermost silver film 5 will produce two regions with different effects from the NaCl solution after a second low-energy-density exposure, as well as the characteristic that continuous laser of a specific wavelength and polarization state will only selectively photo-oxidize Au-Ag nanoparticles of specific size and shape in the intermediate interlayer, thus realizing an information processing method capable of holographic encryption.

[0078] Example 4

[0079] This embodiment provides an encrypted holographic storage method, which includes:

[0080] Obtain a bimetallic co-doped multilayer oxide thin film as described in any of the above embodiments;

[0081] The N first regions on the bimetallic co-doped multilayer oxide film are exposed once using a pulsed laser, and the M second regions on the bimetallic co-doped multilayer oxide film are exposed twice using a pulsed laser. The first regions and the second regions do not overlap, and N and M are both integers greater than 0.

[0082] Holographic storage is performed in the first and second regions: the information to be encrypted is divided into M parts and holographically stored in M ​​second regions in a one-to-one correspondence, while interference information is stored in the first region; or the information to be encrypted is divided into N parts and holographically stored in N first regions in a one-to-one correspondence, while interference information is stored in the second region.

[0083] The first region and the second region are distinguished by brushing the bimetallic co-doped multilayer oxide film with NaCl solution. The first region and the second region after brushing with NaCl solution have different colors.

[0084] Read data from the first region or the second region for holographic storage;

[0085] The information read from the first region or the second region will be spliced ​​together.

[0086] In this embodiment, the first region and the second region have the same shape.

[0087] In this embodiment, the pulsed laser is an infrared laser with a power of 10W, a laser linear velocity of 1000mm / s, a spacing of 0.1mm between two adjacent laser trajectories, and a pulse repetition frequency of 20kHz. This laser irradiation parameter and method will be referred to as low-energy-density exposure below.

[0088] In this embodiment, both the first and second regions are circular. When the circular region is exposed by laser, the laser emitter moves to illuminate the entire circular region line by line to fill it. The distance between two adjacent lines (i.e., the trajectories of two adjacent laser lines) at the center point of the laser scan is 0.1 mm, which is called the line spacing.

[0089] In this embodiment, the information that needs to be encrypted and stored is divided into M parts and stored in M ​​second regions in a one-to-one correspondence. According to the M parts of information that need to be encrypted and stored, interference information is stored in all first regions. The content of the interference information is used to interfere with the splicing of the information after it is read from the information that needs to be encrypted and stored.

[0090] In one specific embodiment, an image is divided into M parts, each corresponding to one of M second regions. After reading the holographic storage data of the M second regions, the holographic storage data of the M second regions are combined to obtain the complete image.

[0091] Similarly, other images (without limiting the number of images) are divided into N parts, each corresponding to one of the N first regions. After reading the N first regions and storing the data holographically, the N holographic data of the first regions are combined to obtain the complete image.

[0092] The above method will be explained in detail below:

[0093] After holographic storage in the first and second regions, the microstructure of the outermost silver film 5 of the stacked structure was characterized by SEM before and after brushing with NaCl solution. The particle size and spacing of the silver nanoparticles were also statistically analyzed. Figure 3 As shown, Figure 3 (a), Figure 3 (b) Scanning electron microscope images before and after brush coating, respectively. After brush coating, the average particle size of the silver nanoparticles was 42.8 nm, and the average gap was 41.5 nm. It can be seen that after brush coating, the originally tightly packed silver particles became silver nanoparticles with a certain spacing.

[0094] After pulsed laser treatment of the multilayer oxide film, brushing with NaCl solution causes the film's color to continue changing. Steganography utilizes the characteristic that silver film 5, after a second low-energy-density exposure, produces two regions with different effects from the NaCl solution. The surface of the multilayer film after the second low-energy-density exposure was characterized using SEM, such as... Figure 4 As shown, Figure 4 The left side shows the product before painting. Figure 4 The right side of the arrow shows the microstructure after brush coating. Two regions can be observed on the film: one is a crescent-shaped region with small silver nanoparticles, averaging only 11.8 nm in diameter; the other is a non-crescent-shaped region with larger silver nanoparticles, averaging 43.3 nm in diameter. In both regions, the silver is composed of silver nanoparticles, exhibiting strong localized surface plasmon resonance (LSPR) absorption. The absorption spectra of the bimetallic co-doped multilayer oxide film after primary and secondary low-energy-density exposures were measured using a UV-Vis spectrophotometer. Figure 5 As shown, it can be observed that the absorption spectra of the multilayer oxide film after the first and second low-energy-density exposures are very similar. This is reflected in the physical image as the areas exposed by the first and second low-energy-density exposures appearing to be essentially the same color, making them indistinguishable. This achieves information steganography, as shown in the image. Figure 6 As shown, Figure 6The image shows the thin film after being brushed with NaCl solution. A single low-energy-density exposure was used to expose the letter 'N', followed by a second low-energy-density exposure to expose the consecutive letters 'ENU'. Before the NaCl solution was applied, it was impossible to distinguish which letter was exposed during the first and second low-energy-density exposures. After the application, the color difference identified the letter 'N' as the area of ​​the first low-energy-density exposure, and 'ENU' as the second low-energy-density exposure. The other areas were areas that did not undergo any low-energy-density exposure. However, after brushing the outermost Ag film of the multilayer structure with NaCl solution, SEM characterization revealed that small particles in crescent-shaped regions tended to aggregate into disordered silver clumps, accompanied by a decrease in LSPR absorption. Particles in non-crescent-shaped regions showed little change. Figure 4 The two smaller images on the far right are shown. This is reflected in the actual image as a significant color difference between the primary low-energy-density exposure area and the secondary exposure area, making them easily distinguishable. This demonstrates the successful reproduction of the holographic reconstruction area, as shown below. Figure 6 As shown.

[0095] Because the center position of the plasmonic absorption line shifts with changes in particle size, shape, and environmental refractive index, when metal particles of different sizes and shapes are aggregated, the absorption band is composed of multiple superimposed bands. If a laser of a certain frequency is used to irradiate the metal particle mixture, only the free electrons of the metal particles corresponding to the resonance frequency will oscillate collectively. When the resonant frequency laser induces photochemical changes in the metal particles, weakening or even eliminating their inherent absorption centers, a depression will appear at the resonance frequency of the entire absorption band, which can be called a "plasmonic spectral hole." The wider the absorption band and the narrower the hole, the more information can be stored per unit area. After introducing Au particles, the absorption band of the Au-Ag co-doped system broadens, such as... Figure 7 As shown, this is beneficial for multi-wavelength holographic spectroscopy hole burning. The stacked oxide thin film constructed in this invention consists of an encrypted addressing layer and a multi-frequency holographic recording layer, using amorphous TaO. xThin film layer 4 and silver film 5 together serve as the encrypted addressing layer, while mesoporous TiO2 film 2 and Au-Ag blended nanoparticles 3 together serve as the multi-frequency holographic recording layer. In the encrypted addressing layer, pulsed lasers irradiate nine circular regions. Three of these regions are selected as the second region for secondary irradiation, while the remaining six are selected as the first region for primary irradiation. At this stage, the naked eye cannot distinguish between these nine circular regions. In the multi-frequency holographic recording layer, lasers are used to record nine different holographic information points in each of the nine circular regions. However, only the three regions that have undergone secondary irradiation record the information we need; the other six record interference information. Therefore, when reading the holographic information with continuous lasers, nine seemingly random pieces of information (H11 to H33, nine small images) will be read, making it impossible to determine the true information. However, after applying NaCl solution to the outermost silver film 5 of the multilayer structure using a brush, the colors of the first and second regions will be significantly different. This allows us to distinguish the three points that were previously irradiated twice by the pulsed laser, thus obtaining three pieces of true information (H12, H23, H31). Figure 8 As shown.

[0096] Example 5

[0097] This embodiment provides an application of a bimetallic co-doped multilayer oxide film as a color printing material, that is, a bimetallic co-doped multilayer oxide film used in the field of color printing.

[0098] The color saturation of the multilayer oxide film increased with increasing high energy density exposure times. The microstructure of the bimetallic co-doped multilayer oxide films after pulsed laser treatment with different high energy density exposure times was characterized using a Quanta 250FEG XL-30 scanning electron microscope (SEM). The particle size and density of the topmost silver nanoparticles were also statistically analyzed. The measurement results are shown below. Figure 9 As shown, Figure 9 (a), Figure 9 (b), Figure 9 (c) The exposure times were one, two, and three, respectively. After one, two, and three high-energy-density exposures, the average particle sizes of the silver nanoparticles were 9.3 nm, 12.4 nm, and 19.0 nm, respectively, and the densities were 4.6 × 10⁻⁶. 11 / cm 2 3.0×10 11 / cm 2 and 1.0×10 11 / cm 2 . Figure 9 The colors of the stacked oxide films after one, two, and three high-energy-density exposures are also shown, such as... Figure 9The middle arrow indicates the color of the thin film after high-energy-density exposure. The high-energy-density exposure was performed by irradiating the bimetallic co-doped multilayer oxide thin film with a power of 10W infrared pulsed laser. The laser moving linear velocity was 100mm / s, the distance between the two laser tracks was 0.05mm, and the pulse repetition frequency was 20kHz.

[0099] It can be observed that as the number of high-energy-density exposures increases, the average size increases while the particle density decreases. This indicates that the thermal radiation energy received from the pulsed laser has a cumulative effect on the formation of silver nanoparticles. Due to insufficient thermal energy, a single high-energy-density exposure only produces densely distributed small-sized particles at the center of the exposed area. Repeated processing leads to the melting of these small silver nanoparticles, which then re-aggregate into larger silver nanoparticles. It should be noted that, unlike high-energy-density exposure, if the exposure energy density is reduced, the color hardly changes after repeated printing, which is the information steganography described in Examples 3 and 4 above.

[0100] Example 6

[0101] This embodiment provides a color printing method, including:

[0102] Obtain a bimetallic co-doped multilayer oxide thin film as described in any of the above embodiments;

[0103] Color printing is achieved by irradiating the bimetallic co-doped multilayer oxide film with pulsed laser; the number of exposures is selected according to the pre-printed color, as well as the power of the pulsed laser, the laser moving linear velocity, the spacing between two adjacent laser trajectories, and the pulse repetition frequency for each exposure.

[0104] The pulsed laser energy for color printing is higher than that for encrypted holographic storage. Generally, within a certain range, the higher the energy of the thin film, the deeper the color of the color print.

[0105] For example, the bimetallic co-doped multilayer oxide film is irradiated with an infrared pulsed laser with a power of not less than 10W, the laser moving linear speed is not less than 100mm / s, the distance between the two laser trajectories is not more than 0.05mm, and the pulse repetition frequency is not less than 20kHz.

[0106] Figure 10 The different colors achieved by a single exposure using different laser irradiation parameters are all achieved using 1064nm infrared pulsed laser. Figure 10 (a) The film is yellow after being irradiated by color printing pulse light. The laser power is 5W, the laser moving linear speed is 800mm / s, the distance between the two laser tracks is 0.06mm, and the pulse repetition frequency is 20kHz. Figure 10(b) The color is light brick red, the laser power is 20W, the laser moving linear speed is 800mm / s, the distance between the two laser tracks is 0.06mm, and the pulse repetition frequency is 20kHz. Figure 10 (c) The color is beige, the laser power is 10W, the laser moving linear speed is 800mm / s, the distance between the two laser tracks is 0.03mm, and the pulse repetition frequency is 20kHz. Figure 10 (d) is purple, the laser power is 10W, the laser moving linear speed is 100mm / s, the distance between the two laser tracks is 0.06mm, and the pulse repetition frequency is 20kHz.

[0107] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0108] In summary, this invention provides a bimetallic co-doped layered oxide thin film, a method for preparing the thin film, its application in encrypted holographic storage materials and the encrypted holographic storage method based on the thin film, and its application in color printing materials and the color printing method based on the thin film. The layered oxide thin film of this invention is a composite thin film based on metal and TiO2, which simultaneously possesses gold and silver metal nanoparticles, exhibiting good pore-burning effect in multi-wavelength holographic spectroscopy. Mesoporous TiO2 film 2 and Au-Ag blended nanoparticles 3 together serve as a multi-frequency holographic recording layer, while amorphous TaO2... x Thin film layer 4 and silver film 5 together serve as an encrypted addressing layer, which can be used for encrypted holographic storage and color printing, expanding the application range of metal and TiO2 composite thin films and creatively realizing encrypted holographic storage.

[0109] Typically, pulsed laser processing relies on the transient thermal energy and focusing position of the focused laser beam, but the instantaneous thermal energy of the laser beam has limited ability to fine-tune the morphology of metal nanoparticles. Conversely, chemical solution reactions are relatively slow and moderate processes, and the ability to adjust the size and spacing of the outer Ag particles is closely related to the reaction time and solution concentration. Furthermore, continuous lasers of different wavelengths can also be used to control Au-Ag nanoparticles of different shapes and sizes. This invention creatively proposes an encrypted holographic storage method by comprehensively applying pulsed laser processing, NaCl solution brushing, and continuous laser holographic recording. This encrypted holographic storage method achieves information steganography and holographic reconstruction at specific points.

[0110] Specifically, this invention utilizes the unique LSPR-based absorption characteristics of nanoscale metal particles. Optical absorption and scattering at specific frequencies result from the electric vector resonance of free electrons within the metal particles with the incident light, and the resonance frequency is closely related to the size and shape of the metal nanoparticles. Adjusting the particle spacing and dielectric environment produces different reflected colors over a fairly wide range. The readily available chemical solution is used in holographic information reading as a means of information decryption. Furthermore, the thin film of this invention, as an oxide semiconductor thin film, is an effective optical interference medium layer and can also serve as a metal plasmon hot electron transfer layer and a layer for regulating the deposition and distribution of metal particles. This not only affects color information printing but also forms a metal / semiconductor Schottky interface, constructing a photon gating barrier for spectral hole burning, which is beneficial for multi-frequency holographic spectral hole burning. In the multilayer oxide thin film, pulsed laser processing is used as the addressing unit for steganography, and chemical solution is used for brushing to determine the effective holographic unit address and output effective information. This achieves high-security holographic encryption, which is beneficial for the encrypted steganography of massive amounts of information and will open up a new field for secure big data transmission.

[0111] In addition, the multilayer oxide film of the present invention can also be used in the field of color printing, which broadens the application scope and field of metal + TiO2 system composite films.

[0112] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make further changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A bimetallic co-doped multilayer oxide thin film, characterized in that, include: Glass substrate; Mesoporous TiO2 film located on the glass substrate; Au-Ag blend nanoparticles deposited on mesoporous TiO2 films; Amorphous TaO on Au-Ag blend nanoparticles x Thin film layer, where x is a positive number; Located in the amorphous TaO x The silver film on the thin film layer.

2. The bimetallic co-doped multilayer oxide thin film as described in claim 1, characterized in that, The amorphous TaO x The thickness of the thin film layer is 35–45 nm; the thickness of the silver film is 15–20 nm.

3. The bimetallic co-doped multilayer oxide thin film as described in claim 1, characterized in that, The amorphous TaO x The thickness of the thin film layer is 40 nm, and the thickness of the silver film is 17 nm.

4. A method for preparing a bimetallic co-doped multilayer oxide thin film as described in any one of claims 1 to 3, characterized in that, include: S1. A layer of TiO2 paste is coated on a glass substrate by screen printing, and then subjected to thermal annealing to remove organic components, thereby obtaining the mesoporous TiO2 film. S2. A layer of gold nanoparticles is deposited on the surface of the mesoporous TiO2 film by magnetron sputtering; S3. Immerse the TiO2 film with gold nanoparticles deposited in silver nitrate solution and irradiate it with ultraviolet light to achieve the deposition of silver nanoparticles and form the Au-Ag blended nanoparticle layer. S4. Using a Czochralski (C-P) apparatus, amorphous TaO is coated onto the Au-Ag blend nanoparticle layer via a C-P coating method. x The amorphous TaO was obtained by heat treatment of the layer. x Thin film layer; S5, in the amorphous TaO x A continuous silver film is sputtered onto the thin film layer using magnetron sputtering.

5. The method for preparing a bimetallic co-doped multilayer oxide thin film as described in claim 4, characterized in that, The specific process of S1 is as follows: the glass substrate is placed under the screen of the screen printing machine, and a layer of TiO2 slurry is scraped onto the upper surface of the glass substrate by a scraper. Then the glass substrate is placed in a muffle furnace for annealing to remove the polymer in the TiO2 slurry and obtain the mesoporous TiO2 film. The specific process of S2 is as follows: open the argon main valve of the gas cylinder, adjust the pressure reducing valve to make the output gas pressure 0.035-0.045MPa, load the gold target, place the mesoporous TiO2 film obtained in S1 in the magnetron sputtering instrument, sputter gold, deposit a layer of gold nanoparticles on the surface of the mesoporous TiO2 film, and obtain a mesoporous TiO2 film with gold nanoparticles deposited. The specific process of S3 is as follows: the mesoporous TiO2 film with gold nanoparticles deposited is immersed in a 0.5 mol / L silver nitrate solution, the liquid level of the silver nitrate solution is higher than the mesoporous TiO2 film with gold nanoparticles deposited in it, and ultraviolet light is irradiated for 5 minutes to achieve the deposition of silver nanoparticles and obtain the Au-Ag blend nanoparticles. The specific process of S4 is as follows: the Au-Ag blended nanoparticles obtained in S3 are placed in TaO. x TaO was prepared on Au-Ag blended nanoparticle layers via dip-coating in a precursor sol. x During the thin film dipping process, the glass substrate rises and falls at a speed of 0.35 cm / s, and is immersed in TaO. x The precursor sol was applied for 6 seconds, and after impregnation, it was suspended vertically to the ground for 3 minutes, followed by heat treatment at 160°C for 30 minutes. The specific process of S5 is as follows: open the argon main valve of the gas cylinder, adjust the pressure reducing valve to make the output gas pressure 0.035-0.045MPa, load the silver target, use tweezers to place the film obtained in S4 into the magnetron sputtering instrument, sputter silver to obtain a continuous silver film, and the preparation of the bimetallic co-doped multilayer oxide film is completed.

6. The method for preparing a bimetallic co-doped multilayer oxide thin film as described in claim 5, characterized in that, The glass substrate is annealed in a muffle furnace by placing it in a muffle furnace at 500°C for 1 hour; the gold sputtering time is 5 seconds; the silver sputtering time is 20 seconds; and the magnetron sputtering current is 30 mA.

7. The application of a bimetallic co-doped multilayer oxide thin film as described in any one of claims 1 to 3, characterized in that, Applications as encrypted holographic storage materials.

8. A method for encrypted holographic storage, characterized in that, include: Obtain a bimetallic co-doped multilayer oxide thin film as described in any one of claims 1 to 3; The N first regions and M second regions on the bimetallic co-doped multilayer oxide film are exposed once using a pulsed laser, and the first and second regions do not overlap. N and M are both integers greater than 0. The information that needs to be encrypted and stored is divided into M parts, and holographically stored in M ​​second regions in a one-to-one correspondence. Interference information is stored in the first region. Alternatively, the information that needs to be encrypted and stored can be divided into N parts and stored one-to-one in the N first areas, while the interference information is stored in the second area. The first region and the second region are distinguished by brushing the bimetallic co-doped multilayer oxide film with NaCl solution. The first region and the second region after brushing with NaCl solution have different colors. Read data from the first region or the second region for holographic storage; The information read from the first region or the second region will be spliced ​​together.

9. The encrypted holographic storage method as described in claim 8, characterized in that, The first region and the second region have the same shape.

10. The encrypted holographic storage method as described in claim 8, characterized in that, The pulsed laser is an infrared laser with a power of 10W, a laser moving linear speed of 1000mm / s, a spacing of 0.1mm between two adjacent laser lines, and a pulse repetition frequency of 20kHz.

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