A method for constructing a full-gamut and color-changing afterglow-manipulating all-inorganic perovskite and its application in information security.

Abstract

This invention belongs to the field of luminescent materials technology, specifically relating to a class of all-inorganic perovskites possessing long-lasting luminescence, tunable full-color gamut emission at different temperatures, long afterglow with color change, and wavelength dependence of reverse excitation, along with its preparation method and information security applications. The specific operation of this method involves using a hydrothermal method to dope with cesium chloride, cadmium chloride, cesium bromide, and cadmium bromide to obtain an all-inorganic perovskite material exhibiting color change, long afterglow, and long-lasting luminescence. The advantages of this invention are that the obtained perovskite displays color-change and long afterglow characteristics; this invention achieves ultra-long afterglow, full color gamut, and controllable afterglow color-change time in all-inorganic perovskite materials, providing a feasible solution for the design and synthesis of such functional materials and their high-level information encryption applications.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology, and specifically relates to a class of all-inorganic perovskites that combine long-lasting emission, full-color gamut adjustable emission color at different temperatures, long afterglow with color change, and wavelength dependence of reverse excitation, as well as their preparation method and information security applications. Background Technology

[0002] Long-lasting light emission (LPL) has garnered significant attention due to its unique applications in numerous fields, including high-contrast molecular imaging, photodynamic therapy, data encryption, and information storage. Frontier Economics Consulting predicted that by 2022, the global economic value of counterfeiting losses would reach $2.3 trillion, with combined negative impacts estimated at $4.2 trillion. Therefore, developing advanced security and anti-counterfeiting technologies is crucial. Currently, most anti-counterfeiting materials are developed based on fluorescent dyes, but these materials have the potential to be easily cloned and cannot meet the huge market demand. In recent years, long-persistence materials have been widely developed, and based on their time / spatiotemporal discrimination capabilities, they are expected to become a new generation of advanced anti-counterfeiting technologies. For example, US Patent No. 20220204838 applies long-persistence materials to the field of information security. However, persistence times exceeding minutes pose a significant challenge in this field. In this context, it has become apparent that relying solely on long persistence cannot significantly improve the load capacity of anti-counterfeiting information. Therefore, another important breakthrough comes from the emergence of color-changing long-afterglow materials. These materials not only enhance the complexity of anti-counterfeiting and the amount of information carried by utilizing color changes on both temporal and spatial scales, but also use visually intuitive changes to further eliminate traditional, easily cloned fluorescent dyes. For example, US Patent No. 20230014229 states that color-changing effects can improve anti-counterfeiting capabilities and recognizability. However, the research and development of color-changing long-afterglow materials is still in its early stages. Most room-temperature phosphorescent materials typically exhibit monochromatic long-afterglow characteristics, so they will not be discussed further. The design concepts for color-changing long-afterglow materials are mainly divided into two categories: 1) Organic multi-component doping, such as doping different fluorescent dyes into long-afterglow materials to form a host-guest doping mode. However, these materials still cannot escape dependence on fluorescent dyes, and problems such as color crossing and cumbersome dye molecule synthesis remain prominent, hindering the achievement of high-level information security. 2) Single-component materials. These materials have broken free from dependence on fluorescent dyes and have become more flexible and less prone to cloning. Currently, very few reports have been made on such materials. In addition, luminescent materials with reverse excitation wavelength dependence can meet the requirement of adjustable emission wavelength under different excitation light, which helps to improve optical performance.

[0003] Therefore, we are committed to developing a material that does not rely on fluorescent dyes and can achieve long-lasting emission, full-gamut tunable emission color at different temperatures, and color-changing long afterglow. We utilize bromide ions to dope pure inorganic CsCdCl3 perovskite, forming CsCdCl3:x%Br type compounds. The design concept of these compounds is that introducing bromine doping into the inorganic framework disrupts the original symmetry, thereby further forming new trap states and luminescent centers, making it possible to construct color-changing long-afterglow materials and providing opportunities for the field of multi-layered information encryption. This patent, guided by the functions of long-lasting emission, full-gamut tunable emission color at different temperatures, and color-changing long afterglow, constructs a type of color-changing long-afterglow all-inorganic perovskite for application in the field of information security based on a host-guest doping strategy. By doping pure inorganic CsCdCl3 perovskite with tin ions, CsCdCl3:x%Sn type compounds are formed. The design concept for these compounds is that introducing tin doping into a fully inorganic framework disrupts the original symmetry, thereby forming new trapped states and achieving ultralong afterglow. The 5S... 2 Electronic properties lead to wavelength-dependent luminescence properties resulting from reverse excitation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a type of all-inorganic perovskite that combines long-lasting emission, full-gamut adjustable emission color at different temperatures, long afterglow with color change, and wavelength dependence of reverse excitation, as well as its information security applications. This provides new ideas and feasible solutions for the design and synthesis of novel anti-counterfeiting functional materials with high information load capacity and high security level.

[0005] This invention utilizes bromide ions to dope pure inorganic CsCdCl3 perovskite to form a CsCdCl3:x%Br type compound, resulting in a type of all-inorganic perovskite that combines long-lasting luminescence, full-gamut adjustable luminescence color at different temperatures, controllable color change, and long afterglow.

[0006] This invention utilizes tin ions to dope pure inorganic perovskite CsCdCl3 to form CsCdCl3:x%Sn type compounds, resulting in a class of all-inorganic perovskite that combines long-term luminescence and wavelength dependence of reverse excitation.

[0007] The specific preparation process of the complex described in this invention is as follows: (1) Dissolve 4× (1-x) mmol of CsCl, 4× (1-x) mmol of CdCl2, 4×x mmol of CsBr and 4×x mmol of CdBr2 in a 20 mL mixed solution of hydrochloric acid and hydrobromic acid with a molar ratio of (1-x) / x, and then put the solution into a polytetrafluoroethylene reactor.

[0008] (2) Dissolve 4 mmol CsCl, 4×(1-x) mmol CdCl2 and 4×x mmol SnCl2 in 20 mL of hydrochloric acid.

[0009] (3) The reaction vessel of step (1) (2) is kept at 180°C for 12 hours, and then gradually cooled to room temperature to obtain the CsCdCl3:x%Br and CsCdCl3:x%Sn all-inorganic perovskite materials of the present invention.

[0010] (4) The crystal obtained in step (2) is washed with isopropanol, filtered, and dried at room temperature to prepare an inorganic perovskite with the characteristics of long-lasting emission, full-color gamut adjustable emission color at different temperatures, and controllable color change and long afterglow.

[0011] (5) The CsCdCl3:x%Br compound selected in step (1) was exposed to ultraviolet light and emitted cyano green fluorescence. After the ultraviolet lamp was turned off, the afterglow changed from cyano green to orange red.

[0012] (6) The CsCdCl3:x%Br compound selected in step (1) shows that the color-changing time valve of its color-changing afterglow can be adjusted as the value of x changes.

[0013] (7) The CsCdCl3:x%Br compound in step (1) exhibits the characteristic of full color gamut temperature dependence in the visible light region.

[0014] The materials prepared above were characterized as follows: 1. X-ray single-crystal diffraction data show that the main structure of the selected CsCdCl3:x%Br and CsCdCl3:x%Sn all-inorganic perovskite materials, CsCdCl3, is as follows: its lattice is P 63 The space group is / mmc. This three-dimensional asymmetric element is composed of [CdCl6]. 4- It is composed of octahedrons, with two shared triangular faces forming [Cd₂Cl₉]. 5- in C 3v Symmetrical, then with the other six [CdCl6] 4- Octahedral connections form angle-sharing D 3d symmetry.

[0015] 2. Scanning electron microscope (SEM) images show Br - or Sn 2+ The doped CsCdCl3 crystals exhibit a typical spindle shape, and the EDS elemental composition (Cs, Cd, Cl, Br, or Sn) shows a uniform distribution in the elemental mapping image, proving that Br... - or Sn 2+ Ion doping was successful.

[0016] 3. The CsCdCl3 host exhibits an emission wavelength of 595 nm under 254 nm excitation, but its lifetime and quantum yield are both very low. Compared to the original CsCdCl3 crystal, the prepared CsCdCl3:x%Br (x = 0.2-15) crystal shows a large, broad peak from 350 nm to 800 nm with a light emission center at 482 nm. Delayed-wave spectroscopy reveals that with increasing Br doping concentration, the large emission peak between 350 nm and 800 nm is a recombination of the emission peaks at 482 and 595 nm. Furthermore, the quantum yield is as high as 84.47%, and the afterglow delay time reaches 2000 s.

[0017] 4. Under 254 nm ultraviolet light excitation, as Sn... 2+ As the ion doping concentration increased from 1% to 10%, the main emission peak of CsCdCl3:x%Sn at 595 nm was enhanced, and the PLQY reached a maximum of 65.71% with a 2000-second afterglow. Subsequently, at an excitation wavelength of 282 nm, with the increase of Sn... 2+ With the increase of ions, there is a significant enhancement of the emission peak at 565 nm, accompanied by an afterglow of 1000 seconds.

[0018] Advantages of this invention: (1) The afterglow material with a time of more than one minute can be synthesized by wet method at a low temperature of 180℃. Compared with the traditional pure inorganic long afterglow material which requires a synthesis condition of 1000℃, it has the characteristics of significantly reducing energy consumption and improving production safety.

[0019] (2) The CsCdCl3:x%Br is the first to realize that the color-changing time valve of its color-changing afterglow can be adjusted as the value of x changes.

[0020] (3) The CsCdCl3:x%Br exhibits the characteristic of full color gamut temperature dependence in the visible light region.

[0021] (4) Both CsCdCl3:x%Br and CsCdCl3:x%Sn exhibited afterglow times exceeding 2000 seconds.

[0022] (5) Both CsCdCl3:x%Br and CsCdCl3:x%Sn exhibit high luminescence quantum yield.

[0023] (6) The CsCdCl3:x%Sn exhibits reverse excitation wavelength dependence at room temperature.

[0024] (7) The material described in this invention has the characteristics of rich color change, large information capacity, and difficulty in cloning and substitution, and can be used in the field of high-level multi-level information encryption technology. Attached Figure Description

[0025] Figure 1 SEM images of (a) CsCdCl3 crystal structure, (b) CsCdCl3:0.8%Br and (c) CsCdCl3:10%Sn, and their corresponding elemental mapping diagrams of Cs, Cd, Cl, Br and Sn.

[0026] Figure 2 (a) Delayed emission (td = 1 ms) spectra of CsCdCl3:x%Br and (b) CsCdCl3:x%Sn under 254 nm excitation. (c) Emission lifetime curves of CsCdCl3:x%Br and (d) CsCdCl3:x%Sn. (e) Three-dimensional time-resolved spectrum of CsCdCl3:0.8%Br under 254 nm excitation. (f) Delayed emission spectrum of CsCdCl3:10%Sn at 297 K.

[0027] Figure 3 (a) Afterglow photographs of CsCdCl3:x%Br, (x = 0), C (x = 0.2%), D (x = 0.5%), E (x = 0.8%), F (x = 1), G (x = 3), H (x = 5), J (x = 10), and K (x = 15). CIE coordinate plots of CsCdCl3:0.8%Br in temperature response (b) c) and (c) delayed modes. (d) Change in emission color of CsCdCl3:0.8%Br with temperature by turning a 254 nm UV lamp on / off. (e) Afterglow photographs of CsCdCl3:x%Sn, L (x=1), M (x=3), O (x=5), S (x=10), and T (x=15).

[0028] Figure 4(a) Anti-counterfeiting patterns of CsCdCl3:x%Br and CsCdCl3:x%Sn sample powders under 254 nm irradiation, and (b) the corresponding afterglow patterns after excitation was stopped at 1 s, (c) 3 s, and (d) 120 s. (e) QR code images of CsCdCl3:x%Br and CsCdCl3:x%Sn under a 254 nm UV lamp, and afterglow imaging at different time intervals. (f) Schematic diagram of the QR code encryption / decryption process. (g) The QR code image includes CsCdCl3:x%Br and CsCdCl3:x%Sn, with values ​​of A (0%Br), C (0.2%Br), D (0.5%Br), E (0.8%Br), F (1%Br), g (3%Br), H (5%Br), J (10%Br), H (15%Br), L (1%Sn), M (3%Sn), O (5%Sn), S (10%Sn), and T (15%Sn), respectively. (h) The afterglow imaging QR code is converted from binary to decimal after 18 seconds. Detailed Implementation

[0029] The present invention will be further illustrated below by way of examples, but is not limited to these examples. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available. Example 1

[0030] (1) Dissolve 4* (1-x) mmol of CsCl, 4* (1-x) mmol of CdCl2, 4*x mmol of CsBr and 4*x mmol of CdBr2 in a 20 mL mixed solution of hydrochloric acid and hydrobromic acid with a molar ratio of (1-x) / x, and then put the solution into a polytetrafluoroethylene reactor.

[0031] (2) Dissolve 4 mmol CsCl, 4*(1-x) mmol CdCl2 and 4*x mmol SnCl2 in 20 mL of hydrochloric acid.

[0032] (3) The reactor of Example 1 (1) was kept at 180°C for 12 hours and then gradually cooled to room temperature to obtain the CsCdCl3:x%Br all-inorganic perovskite material of the present invention.

[0033] (4) The reactor of Example 1 (2) was kept at 180°C for 12 hours and then gradually cooled to room temperature to obtain the CsCdCl3:x%Sn all-inorganic perovskite material of the present invention.

[0034] X-ray single-crystal diffraction data show that the main structure of the selected CsCdCl3:x%Br and CsCdCl3:x%Sn all-inorganic perovskite materials, CsCdCl3, is as follows: its lattice is P 63 The space group is / mmc. This three-dimensional asymmetric element is composed of [CdCl6]. 4- It is composed of octahedrons, with two shared triangular faces forming [Cd₂Cl₉]. 5- in C 3v Symmetrical, then with the other six [CdCl6] 4- Octahedral connections form angle-sharing D 3d symmetry( Figure 1 a).

[0035] Scanning electron microscope (SEM) images show Br - or Sn 2+ The doped CsCdCl3 crystals exhibit a typical spindle shape, and the EDS elemental composition (Cs, Cd, Cl, Br, or Sn) shows a uniform distribution in the elemental mapping image, proving that Br... - or Sn 2+ Ion doping was successful. Figure 1 (b and c).

[0036] The CsCdCl3 host exhibits an emission wavelength of 595 nm at an excitation wavelength of 254 nm, but its lifetime and quantum yield are both very low. Compared with the original CsCdCl3 crystal, the prepared CsCdCl3:x%Br (x = 0.2-15) crystals show a broad peak from 350 nm to 800 nm with a light emission center at 482 nm. Figure 2 (a) Delayed spectroscopy shows that, with increasing Br doping concentration, the large emission peak between 350 nm and 800 nm is a composite of the emission peaks at 482 and 595 nm. Figure 2 Furthermore, the quantum yield is as high as 84.47% and the afterglow lifetime reaches 2000s (e). Figure 2 c), and exhibits time-controlled color-changing afterglow depending on the bromine concentration ( Figure 3 a) and full-gamut color temperature-dependent luminescence ( Figure 3 (b to d).

[0037] Under 254 nm ultraviolet light excitation, as Sn 2+ As the ion doping concentration increased from 1% to 10%, the main emission peak of CsCdCl3:x%Sn at 595 nm was enhanced. Figure 2 b), and PLQY can reach up to 65.71% and 2000 seconds of orange-red afterglow ( Figure 2 d and Figure 3e). Subsequently, at an excitation wavelength of 282 nm, as Sn 2+ With the increase of ions, there is a significant enhancement of the emission peak at 565 nm, accompanied by a 1000-second afterglow. Therefore, as the excitation wavelength changes from 250 nm to 310 nm, the emission peak exhibits a reversible blue shift excitation property. Figure 2 f). Example 2

[0038] The above-mentioned crystalline product was used to prepare an anti-counterfeiting pattern. When exposed to 254 nm ultraviolet light, it displayed "I". BNU 8888 (BNU: Beijing Normal University) Figure 4 a), and two other error messages that were individually interpreted as orange-red or cyan channels. After the UV lamp stopped for 1 second, the subsequent error message was interpreted as "I "BNU 2083", and two other error messages ( Figure 4 (b). Then an error message appeared. Finally, the orange-red anti-counterfeiting pattern revealed "I Information from BNU 2023 ( Figure 4 , d). The entire process can be viewed as a 5D anti-counterfeiting technology, which surpasses traditional afterglow materials due to its time-gated color change increased by Br doping engineering. Example 3

[0039] Furthermore, by filling the QR code slots with a series of synthetic perovskites, the change in the afterglow color of each region is defined as requiring a 1-bit shift (+1) in the binary system. After excitation with a 254 nm ultraviolet lamp, the QR code displays orange-red and cyan, which translates to "000" in binary. With a delay of 0.5 seconds, binary codes "011", "110", and "101" are formed. After 1 second, they become "11010", "10110", and "10101". After 18 seconds, security codes "1161, 1764, 1508, 1481, 1175, and 1179" are generated through binary and decimal conversion. Figure 4 (e). The final lock code is "1508". It's worth noting that maximum information load capacity is achieved when the binary numbers at all time points are interchangeable. Therefore, leveraging the advantages of these perovskite time / space / color and color-gated four-layer resolutions holds promise for playing a highly efficient role in advanced, high-security anti-counterfeiting systems.

Claims

1. The construction of full-gamut and color-changing long-afterglow inorganic perovskites and their application in information security, characterized in that, The preparation steps are as follows: 1) Dissolve 4×(1-x) mmol of CsCl, 4×(1-x) mmol of CdCl2, 4×x mmol of CsBr, and 4×x mmol of CdBr2 in a 20 mL mixed solution with a hydrochloric acid to hydrobromic acid molar ratio of (1-x) / x, and load the solution into a polytetrafluoroethylene reactor. 2) Dissolve 4 mmol of CsCl, 4×(1-x) mmol of CdCl2, and 4×x mmol of SnCl2 in 20 mL of hydrochloric acid. 3) Keep the reactor from steps (1) and (2) at 180°C for 12 hours, and then gradually cool it to room temperature to obtain the CsCdCl3:x%Br and CsCdCl3:x%Sn all-inorganic perovskite materials of the present invention.

2. The preparation method according to claim 1, characterized in that, The obtained CsCdCl3:x%Br and CsCdCl3:x%Sn all-inorganic perovskite materials have a main structure of CsCdCl3 with a lattice group of P63 / mmc. This three-dimensional asymmetric unit cell consists of [CdCl6]. 4- It is composed of octahedrons, with two shared triangular faces forming [Cd2Cl9]. 5- in C 3v Symmetrical, then with the other six [CdCl6] 4- Octahedral connections form angle-sharing D 3d symmetry.

3. The preparation method according to claim 1, characterized in that, The obtained CsCdCl3:x%Br material exhibited properties such as color change and long afterglow after the ultraviolet lamp was turned off.

4. The preparation method according to claim 1, characterized in that, The obtained CsCdCl3:x%Br color-changing long afterglow material exhibits a large-scale, controllable color-changing range from cyano green to orange-red.

5. The obtained CsCdCl3:x%Br and CsCdCl3:x%Sn materials exhibited persistent luminescence for over 2000 seconds.

6. The obtained CsCdCl3:x%Br color-changing long afterglow material exhibits temperature-dependent full-gamut luminescence characteristics.

7. Both the obtained CsCdCl3:x%Br and CsCdCl3:x%Sn materials exhibit high luminescence quantum yields.

8. The obtained CsCdCl3:x%Sn exhibits a reverse excitation wavelength dependence at room temperature.

9. The preparation method according to claim 1, characterized in that, The compounds that were synthesized belong to an improved wet synthesis method.

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