WO2019041505A1

WO2019041505A1 - Fluorescent perovskite nanocrystal and confidential information security application thereof

Info

Publication number: WO2019041505A1
Application number: PCT/CN2017/108306
Authority: WO
Inventors: 李良; 张从阳
Original assignee: 李良
Priority date: 2017-09-01
Filing date: 2017-10-30
Publication date: 2019-03-07
Also published as: CN109423278A; CN109423278B

Abstract

A method for preparing a fluorescent perovskite nanocrystal and an application thereof for confidential information storage and protection. A cationic halogenated salt solution for use in synthesis of perovskite is added to a metal organic framework dispersion, to directly convert a metal organic framework part into a fluorescent perovskite nanocrystal, and uniformly disperse the fluorescent perovskite nanocrystal in the metal organic framework crystal, thereby providing desirable fluorescence performance. The method has broad applicability. The synthesis method for a perovskite nanocrystal can be directly used in storage and protection of confidential information. Compared with the prior art, the operation process is simple and repeatable, and the metal organic framework material and recorded information thereof are highly secure. The fluorescent perovskite nanocrystal has no absorption in the visible light range, has fluorescent properties, and is invisible to the naked eye. The perovskite nanocrystal has good fluorescent properties, allowing it to be directly applicable to the field of confidential information storage and protection.

Description

Preparation method of fluorescent perovskite nanocrystals and its application in confidential information security

Technical field

The invention belongs to the technical field of semiconductor nano material preparation, in particular to a preparation method for reproducibly synthesizing perovskite nanocrystals through a metal organic framework and its application in confidential information storage and protection.

Background technique

Intelligent fluorescent materials with stimulating response have a wide range of uses in information security and other fields. This kind of material generally regulates the arrangement mode of molecules by external stimuli (such as light, electricity, heat, mechanical force, etc.), thereby achieving the purpose of changing the fluorescent signal of the material. Fluorescent materials currently used in this field include various organics, metal complexes, inorganic quantum dots, upconverting nanoparticles, and the like. However, these materials still have many shortcomings, such as poor fluorescence performance, high cost, and complicated synthesis and cleaning processes. In addition, their strong light absorption and photoluminescence properties in the visible light range determine that the recorded information can be visually recognized under sunlight or ultraviolet light, which limits its application in the storage and protection of confidential information. Therefore, how to obtain high-performance, low-cost and safe (invisible to the naked eye) intelligent fluorescent materials and systems is still a big challenge.

The metal halide perovskite crystal material has a structure of the ABX3 type, and A and B represent different cations, and combine with the anion X to form a CaTiO3 type lattice structure. Wherein A is generally a monovalent cation; B is a metal ion; and X is a type of Cl-, Br-, or I-. Metal halide perovskite materials have been rapidly developed in the photovoltaic field due to their good semiconductor properties (high mobility, long carrier diffusion length, low defect density), and are currently based on metal halide perovskite materials. The solar cell photoelectric conversion efficiency has exceeded 20%. At the same time, metal halide perovskite materials have also shown good application prospects in the field of optical display. As a direct bandgap semiconductor, metal halide Perovskite nanocrystals (or quantum dots) have outstanding features such as low cost, solution preparation, easy processing, color adjustment, high quantum yield, and narrow fluorescence peaks. They have become a new type of fluorescent material. It has broad application prospects in the field of optoelectronic devices such as light-emitting diodes, lasers, and illumination. Based on the above advantages, fluorescent metal halide perovskite nanocrystals also have the possibility of application in the field of information security. Recently, Wang et al. (Adv. Mater. 2016, 28, 10637-10643) reported the phase of a metal halide perovskite material under low power (≈5mW cm-2) short wavelength (325nm) photoexcitation. The phenomenon of transition (from two-dimensional to three-dimensional) and the resulting change in fluorescent color, and preliminary verification of its application possibilities in the recording and preservation of multi-color fluorescent patterns, displays, and optical information. However, this method and material still cannot meet the needs of storage and protection of confidential information. Because of the ink used to record information, the two-dimensional perovskite material itself still has blue fluorescent characteristics, resulting in the information recorded by it in the light. In the case of excitation, it can still be recognized by the naked eye; secondly, this photoinduced phase transformation process cannot be repeated, and its practical application is limited. At present, there have been no reports on the application of fluorescent perovskite nanocrystals in the field of confidential information storage and protection. Therefore, the development of a new type of intelligent fluorescent materials and systems based on perovskite has important application value.

The metal organic skeleton (MOF) is a crystalline porous material having a regular pore or pore structure which is interconnected by an inorganic metal center and an organic functional group through coordinate bonds. Metal organic framework materials have great potential in adsorption, separation, catalysis and sensing because of their large specific surface area, easy synthesis, structural diversity and modification. The present invention synthesizes high-fluorescence-efficiency perovskite nanocrystals by a method that can be directly converted from MOF materials. In this method, we also utilize the safety of a specific MOF material (no absorption and fluorescence characteristics in the visible range). , can not be recognized by the naked eye) and the fluorescent properties of perovskite materials, to achieve its application in the field of confidential information storage.

Summary of the invention

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for reproducibly synthesizing fluorescent perovskite nanocrystals and the application of storage and protection of confidential information in order to overcome the drawbacks of the prior art described above.

The object of the present invention can be achieved by the following technical solutions:

One of the objects of the present invention is to provide a method for preparing a fluorescent perovskite nanocrystal. The synthesis process of metal halide perovskite nanocrystals by directly converting MOF materials containing specific metals makes the conversion process extremely simple, can achieve reversible transformation, and is versatile.

The above synthesis method is suitable for the preparation of a perovskite nanocrystalline powder and a perovskite nanocrystalline film. Specifically, the method for converting the above repeatable MOF material into a metal halide perovskite nanocrystal comprises the following steps:

(1) Dispersing the MOF material in the solvent I to prepare a suspension having a concentration of 0.5 to 25 g/L; the MOF material described in the step (1) is synthesized by conventional room temperature stirring or solvothermal method, and organic in the MOF material. The ligand is a carboxylic acid ligand or an imidazole ligand; the MOF material is Zn-MOF, Hg-MOF, Pb-MOF, Sn-MOF, Ge-MOF, Si-MOF, Ga-MOF, Bi-MOF, One of In-MOF, Mn-MOF, Cu-MOF;

The solvent I is selected from any one of toluene, chlorobenzene, chloroform, n-hexane, cyclohexane, ethyl acetate or diethyl ether, preferably toluene and n-hexane.

(2) Dissolving the cationic halogenated salt in the solvent II, and completely dissolving it to obtain a cationic halogenated salt solution having a concentration of 0.05 to 25 g/L; and the cationic halogenated salt described in the step (2) is MA+, FA+, Cs+, One or more mixed systems in Rb+; the metal used is one or more mixed systems of zinc, mercury, lead, tin, antimony, silicon, gallium, indium, manganese or copper, and the halogen used is chlorine, bromine, One or more mixed systems of iodine;

The solvent II is selected from the group consisting of methanol, ethanol, isopropanol, butanol, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, acetonitrile or acetone, preferably butanol.

(3) adding the cationic halogenated salt solution obtained in the step (2) to the suspension obtained in the step (1), stirring continuously for 5 to 300 seconds, and the obtained dispersion is filtered or centrifuged, and dried to obtain calcium embedded in the MOF. Titanium ore nanocrystalline powder.

Dispersing the perovskite nanocrystalline powder embedded in the MOF prepared in the step (3) into the solvent III, stirring continuously until the fluorescence of the perovskite nanocrystal completely disappears, and then filtering or centrifuging the non-fluorescent powder, Drying, the obtained non-fluorescent powder can be directly reused for the process of converting and synthesizing perovskite nanocrystals, thereby enabling multiple repeated transformations. The solvent III is one of water, methanol, ethanol, acetone, DMF, DMSO, preferably methanol.

In addition, the second object of the present invention is to propose an application based on the above-described rapid reproducible synthesis of perovskite nanocrystals by MOF in the storage and protection of confidential information.

The specific application method includes the following steps:

(1) Preparation of the precursor solution: the metal salt and the organic ligand constituting the MOF material are added to the solvent II, and then the volume ratio of 5-20:1-15 ethanol and ethylene glycol is continuously added, and the mixture is ultrasonicated or stirred. The method is completely dissolved to obtain a MOF precursor liquid; the metal salt is one of zinc, mercury, lead, tin, antimony, silicon, gallium, indium, manganese or copper nitrate, acetate or halogenated salt. The organic ligand may be a carboxylic acid ligand or an imidazole ligand. The mass ratio of the metal salt to the organic ligand is from 0.5 to 5: 0.1 to 2.

(2) Storage and encryption of confidential information: the precursor liquid is printed onto the substrate by printing technology, and dried and cleaned to obtain a substrate having information recorded by the MOF crystal, that is, a process of storing confidential information; the printing technique is concave Traditional printing methods and printing with printing, lithography, screen printing or embossing The non-printing method represented by ink; due to the security of a specific MOF material, the information recorded by it cannot be recognized by ordinary decryption methods, which provides practical application possibilities for the storage and protection of confidential information.

(3) Decryption of confidential information: The above-mentioned information-recorded substrate is treated with a cationic halogenated salt to complete the conversion of MOF to perovskite nanocrystals, and the fluorescent signal generated in this process can be easily detected, that is, The process of decrypting the information recorded by the MOF; the cationic halogenated salt is treated by one of solution immersion, solution spray or gas phase contact reaction.

(4) Repeated encryption and decryption process of confidential information: The above-mentioned decrypted substrate is treated with solvent III to completely quench the generated fluorescent signal, that is, the re-encryption process of confidential information.

The non-fluorescent substrate obtained in the step (4) repeats steps (3) and (4) again, and the fluorescence can be generated and quenched again, that is, the process of multiple encryption and decryption of confidential information.

Compared with the prior art, the present invention has the following advantages:

1) In the present invention, perovskite nanocrystals are cheaper and have superior fluorescence performance than other smart fluorescent materials.

2) Compared with the conventional synthesis method, the synthesis process of the fluorescent perovskite nanocrystal in the invention is simple, rapid and repeatable.

3) In the present invention, MOF-perovskite nanocrystals are constructed as an intelligent fluorescent system for storing and protecting confidential information. The use of safe MOF materials can encrypt confidential information, making it unrecognizable by the naked eye, increasing the security of information. In addition, the conversion synthesis of fluorescent nano-crystals with excellent performance realizes the decryption of confidential information. The confidential information encryption and decryption process described above can be repeated multiple times.

DRAWINGS

Figure 1 is a photograph of the prepared Pb-MOF powder;

2 is a photograph of a prepared MAPbBr3 nanocrystalline powder embedded in MOF under a fluorescent lamp (left) and an ultraviolet lamp (right);

Figure 3 is a TEM photograph of a prepared MAPbBr3 nanocrystal embedded in MOF;

4 is a fluorescence spectrum of the prepared MAPbBr3 nanocrystal embedded in MOF;

5 is a fluorescence spectrum diagram of a CsPbBr3 nanocrystalline powder embedded in MOF;

Figure 6 is a fluorescence spectrum of a mixed halogen perovskite (MAPbIxBr3-x-yCly) nanocrystal;

Figure 7 is a photograph of a formulated Pb-MOF precursor solution;

Figure 8 is a photograph of the entire process of repeated encryption and decryption of a synthetic perovskite nanocrystal based on MOF.

Detailed ways

Example 1

Synthesis of lead methylamino bromide (MAPbBr3) nanocrystals based on Pb-MOF

(1) Synthesis of Pb-MOF: 90 mL of 1,3,5-H3BTC aqueous solution (0.01 M) and 10 mL of Pb(NO3)2 aqueous solution (0.09 M) were mixed and continuously stirred for 30 min, and the obtained powder was deionized water and methanol. Washed three times separately and finally vacuum dried at 150 ° C for 12 h;

(2) Synthesis of MAPbBr3 nanocrystals: 200 mg of the synthesized Pb-MOF powder was dispersed in 10 mL of n-hexane to form a suspension, which was uniformly dispersed by stirring. 10 mg of aminobrominated salt (MABr) was dissolved in 1 mL of n-butanol and sonicated to completely dissolve. 0.5 mL of the above MABr solution was quickly added to the Pb-MOF suspension and stirred for 30 s, and then the above dispersion was filtered or centrifuged, and once unwashed with butanol to remove unreacted MABr, the MOF was embedded. MAPbBr3 nanocrystalline powder. The Pb-MOF prepared in this example is shown in Figure 1, and the Pb-MOF powder is White; the photo of MAPbBr3 nanocrystalline powder embedded in MOF is shown in Fig. 2. It can be seen that after conversion, the powder is bright yellow and emits bright green light under ultraviolet light. The TEM morphology and fluorescence spectrum are shown in Fig. 3 and 4 are shown. As can be seen from the figure, the MAPbBr3 nanocrystals of about 10 nm are uniformly dispersed in Pb-MOF, and have a narrow fluorescence peak with a half width of 25 nm at 527 nm. This indicates that high-fluorescence properties of perovskite nanocrystals can be rapidly synthesized by this simple method.

Example 2

Synthesis of lead bromine (CsPbBr3) nanocrystals based on Pb-MOF conversion

(1) Synthesis of Pb-MOF: the same as the preparation method in Example 1;

(2) Synthesis of CsPbBr3 nanocrystals: similar to the preparation method in Example 1, except that the solvent of Pb-MOF dispersion was selected to be toluene, and 10 mg of cesium bromide (CsBr) was dissolved in the preparation of the cationic halogenated salt solution for the conversion reaction. In 1 mL of methanol. The fluorescence spectra of the CsPbBr3 nanocrystalline powders embedded in the MOF prepared in this example are shown in Fig. 5, and the fluorescence emission wavelength is 529 nm, which indicates that the method has good versatility.

Example 3

Conversion Synthesis of Mixed Halogen Perovskite (MAPbIxBr3-x-yCly) Nanocrystals Based on Pb-MOF

(1) Synthesis of Pb-MOF: the same as the preparation method in Example 1;

(2) Synthesis of MAPbIxBr3-x nanocrystals: similar to the preparation method in Example 1, except that the preparation of the cationic halogenated salt solution used for the conversion reaction was different. For x=0, y=3, 10 mg of MAC1 was dissolved in 1 mL of n-butanol; for x=0, y=1, 2.32 mg of MACl and 7.68 mg of MABr were dissolved in 1 mL of n-butanol; for x=0, y=2, 5.47 mg MACl and 4.53 mg MABr were dissolved in 1 mL n-butanol; for x=1, y=0, 4.15 mg MAI and 5.85 mg MABr Dissolved in 1 mL of n-butanol, for x = 2, y = 0, 7.40 mg of MAI and 2.60 mg of MABr were dissolved in 1 mL of n-butanol. The fluorescence spectrum of the mixed halogen perovskite (MAPbIxBr3-x-yCly) nanocrystals is shown in Fig. 6. As the halogen changes from Cl to I, the fluorescence emission wavelength can be adjusted from 406 nm to 746 nm, indicating The method of synthesizing fluorescent perovskite nanocrystals can cover almost the entire visible range.

Example 4

Synthesis Process Based on Example 1 and Its Application in Confidential Information Storage and Protection

(1) Preparation of Pb-MOF precursor solution: 2.15 g of Pb(NO3)2 and 0.58 g of 1,3,5-H3BTC were added to 5 mL of DMSO, and then 11.25 mL of ethanol and 7.5 mL of ethylene glycol were continuously added thereto. The MOF precursor liquid is obtained by completely dissolving it by ultrasonication or stirring. Its photo is shown in Figure 7;

(2) Storage and encryption of confidential information: 5 mL of the above Pb-MOF precursor solution was added to an empty ink cartridge of an ink jet printer. The Pb-MOF precursor liquid was then printed onto the parchment by ink jet printing, then immersed and washed with an alcohol solvent and dried again to obtain a substrate having information recorded in the MOF crystal. Due to the security of a particular MOF material, the information it records cannot be identified by ordinary decryption methods and can be directly used for the storage of certain confidential information;

(3) Decryption of confidential information: The butanol solution of MABr was sprayed to treat the above-mentioned recorded parchment substrate, thereby completing the rapid transition of MOF to perovskite nanocrystals. The fluorescent signal generated in this process can be easily detected, that is, the process of decrypting the information recorded by the MOF can be realized;

(4) Repeated encryption and decryption process of confidential information: the above-mentioned decrypted parchment substrate is soaked with methanol, and after a period of time, the fluorescence signal of the perovskite nanocrystal is completely quenched, that is, The re-encryption process of confidential information is realized. Then, the non-fluorescent substrate is again processed by the methods of steps (2) and (3), and the fluorescence can be generated and quenched again. The whole process is as shown in 8, thereby realizing the process of repeated encryption and decryption of confidential information. This shows that the present invention is well suited for use in the storage and protection of confidential information.

Example 5

Synthesis of non-toxic perovskite nanocrystals based on Sn-MOF conversion, including the following steps:

(1) Dispersing the MOF material in toluene to prepare a suspension having a concentration of 0.5 g/L; wherein the MOF material is a 2D or 3D MOF, and the metal salt and the organic ligand are synthesized by a conventional room temperature stirring method, organic The ligand is a carboxylic acid ligand, the metal salt is Sn, and the MOF material is Sn-MOF;

(2) dissolving the cationic halogenated salt in the solvent II, and completely dissolving it to obtain a cationic halogenated salt solution having a concentration of 0.05 g/L; the cationic halogenated salt is a FA+ system (ie, a mercapto halide); The metal used is tin and the halogen used is chlorine; the solvent II is selected from methanol.

(3) adding the cationic halogenated salt solution obtained in the step (2) to the suspension obtained in the step (1), stirring continuously for 5 to 300 seconds, and the obtained dispersion is filtered or centrifuged, and dried to obtain calcium embedded in the MOF. Titanium ore nanocrystalline powder. The cationic halogenated salt solution obtained in the step (2) and the suspension obtained in the step (1) are used in an amount such that the mass ratio of the finally obtained fluorescent perovskite nanocrystal MOF to ABX3 is 1:0.1.

(4) Dispersing the perovskite nanocrystalline powder embedded in the MOF prepared in the step (3) into methanol, stirring continuously until the fluorescence of the perovskite nanocrystal completely disappears, and then filtering the non-fluorescent powder or After centrifugation and drying, the obtained non-fluorescent powder can be directly reused for the process of converting and synthesizing the perovskite nanocrystals, thereby enabling multiple repeated transformations.

The application of the rapid reproducible synthesis of perovskite nanocrystals by MOF in the storage and protection of confidential information will be based on the above. The specific application method includes the following steps:

(1) Preparation of the precursor solution: the metal salt and the organic ligand constituting the MOF material are added to the solvent II methanol, and then the volume ratio of 5:1 ethanol and ethylene glycol is continuously added, and the mixture is ultrasonicated or stirred. Completely dissolved to obtain a MOF precursor liquid; the metal salt is zinc. The organic ligand may be a carboxylic acid ligand. The mass ratio of the metal salt to the organic ligand is 0.5:0.1.

(2) Storage and encryption of confidential information: The precursor liquid is printed on the substrate by printing technology, dried, and then immersed and washed with an alcohol solvent and dried again to obtain a substrate having information recorded by the MOF crystal, that is, confidential information. The process of storage; the printing technique is a conventional gravure method; due to the security of a particular MOF material, the information recorded by it cannot be recognized by ordinary decryption methods, which provides for the storage and protection of confidential information. The possibility of practical application.

(3) Decryption of confidential information: The above-mentioned information-recorded substrate is treated with a cationic halogenated salt to complete the conversion of MOF to perovskite nanocrystals, and the fluorescent signal generated in this process can be easily detected, that is, The process of decrypting information recorded by MOF; the way in which the cationic halogenated salt is treated is solution soaking.

(5) The non-fluorescent substrate obtained in the step (4) is repeated steps (3) and (4) again, and the fluorescence can be generated and quenched again, that is, the process of multiple encryption and decryption of the confidential information.

Example 6

Conversion of non-toxic perovskite nanocrystals based on Bi-MOF conversion, including the following steps:

(1) Dispersing the MOF material in the solvent I chlorobenzene to prepare a suspension having a concentration of 25 g/L; the MOF material described in the step (1) is a 2D or 3D MOF, which is synthesized by a conventional solvothermal method. The organic ligand in the MOF material is an imidazole ligand; the MOF material is Bi-MOF;

(2) The cationic halogenated salt is dissolved in N,N-dimethylformamide, and completely dissolved by ultrasonication to obtain a cationic halogenated salt solution having a concentration of 2.5 g/L; the cationic halogenated salt is a Rb+ system; The halogen used is iodine;

(3) adding the cationic halogenated salt solution obtained in the step (2) to the suspension obtained in the step (1), stirring continuously for 5 to 300 seconds, and the obtained dispersion is filtered or centrifuged, and dried to obtain calcium embedded in the MOF. Titanium ore nanocrystalline powder. The cationic halogenated salt solution obtained in the step (2) and the suspension obtained in the step (1) are used in an amount such that the mass ratio of the finally obtained fluorescent perovskite nanocrystal MOF to ABX3 is 50:0.1.

(4) Dispersing the perovskite nanocrystalline powder embedded in the MOF prepared in the step (3) into the solvent IIIDMF, stirring continuously until the fluorescence of the perovskite nanocrystal completely disappears, and then filtering the non-fluorescent powder. Alternatively, by centrifugation and drying, the obtained non-fluorescent powder can be directly used again for the process of converting and synthesizing the perovskite nanocrystals, thereby enabling multiple repeated transformations.

(1) Preparation of the precursor solution: the metal salt and the organic ligand constituting the MOF material are added to the solvent II, and then the volume ratio of 20:15 ethanol and ethylene glycol is continuously added, and the mixture is completely ultrasonicated or stirred. The MOF precursor liquid is dissolved; the metal salt is ruthenium, and the organic ligand may be an imidazole ligand. The mass ratio of the metal salt to the organic ligand is 5:2.

(2) Storage and encryption of confidential information: The precursor liquid is printed on the substrate by printing technology, dried, and then immersed and washed with an alcohol solvent and dried again to obtain a substrate having information recorded by the MOF crystal, that is, confidential information. The process of storage; the printing technique is an inkjet printing method; due to the security of a particular MOF material, the information recorded by it cannot be recognized by ordinary decryption methods, which provides for the storage and protection of confidential information. The possibility of practical application.

(3) Decryption of confidential information: The above-mentioned information-recorded substrate is treated with a cationic halogenated salt to complete the conversion of MOF to perovskite nanocrystals, and the fluorescent signal generated in this process can be easily detected, that is, The process in which the information recorded by the MOF is decrypted; the way in which the cationic halogenated salt is treated is one of the gas phase contact reactions.

(4) Repeated encryption and decryption process of confidential information: The above-mentioned decrypted substrate is treated with solvent IIIDMF to completely quench the generated fluorescent signal, that is, the re-encryption process of confidential information.

It should be emphasized that the above-described embodiments of the present disclosure are only a part of the embodiments of the present disclosure, and may be explained only for the purpose of clearly understanding the principles of the disclosure, without departing from the spirit and principle of the disclosure. Many variations and modifications of the above-described embodiments of the present disclosure are intended to be included within the scope of the present disclosure.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Therefore, any modification, equivalent replacement, and improvement made by using the contents of the specification and drawings of the present invention should be included in Within the scope of protection of the present invention.

Claims

A method for preparing a fluorescent perovskite nanocrystal, characterized in that the method comprises the following steps:

(1) dispersing the MOF material in the solvent I to prepare a suspension having a concentration of 0.5 to 25 g/L;

(2) dissolving the cationic halogenated salt in the solvent II, and completely dissolving it by ultrasonication to obtain a cationic halogenated salt solution having a concentration of 0.05 to 25 g/L;

(3) adding the cationic halogenated salt solution obtained in the step (2) to the suspension obtained in the step (1), stirring continuously for 5 to 300 seconds, and the obtained dispersion is filtered or centrifuged, and dried to obtain calcium embedded in the MOF. Titanium ore nanocrystalline powder.
The method for preparing a fluorescent perovskite nanocrystal according to claim 1, wherein the MOF material in the step (1) is synthesized by a conventional room temperature stirring or a solvothermal method, and the organic ligand in the MOF material is a carboxyl group. Acid ligand or imidazole ligand; the MOF material is Zn-MOF, Hg-MOF, Pb-MOF, Sn-MOF, Ge-MOF, Si-MOF, Ga-MOF, In-MOF, Bi-MOF, One of Mn-MOF and Cu-MOF; the solvent I is selected from any one of toluene, chlorobenzene, chloroform, n-hexane, cyclohexane, ethyl acetate or diethyl ether.
The method for preparing a fluorescent perovskite nanocrystal according to claim 1, wherein the cationic halogenated salt in the step (2) is one or more mixed systems of MA+, FA+, Cs+, and Rb+; The halogen is one or more mixed systems of chlorine, bromine and iodine; the solvent II is selected from the group consisting of methanol, ethanol, isopropanol, butanol, N,N-dimethylformamide, dimethyl sulfoxide One of tetrahydrofuran, acetonitrile or acetone.
The method for preparing a fluorescent perovskite nanocrystal according to claim 1, wherein the perovskite nanocrystalline powder embedded in the MOF obtained in the step (3) is dispersed in the solvent III, and continuously stirred. Until the fluorescence of the perovskite nanocrystals completely disappears, then the non-fluorescent powder is filtered or centrifuged and dried, and the obtained non-fluorescent powder can be directly reused for the process of converting and synthesizing the perovskite nanocrystals, thereby enabling multiple repetitions. Conversion.
The method for preparing a fluorescent perovskite nanocrystal according to claim 4, wherein the solvent III is one of water, methanol, ethanol, acetone, DMF, and DMSO.
The invention relates to the application of a fluorescent perovskite nanocrystal in the safety of confidential information, characterized in that the fluorescent perovskite nanocrystal is prepared by the preparation method of the fluorescent perovskite nanocrystal according to claim 1, and the fluorescent calcium is realized. Titanium ore nanocrystals are used in the storage and protection of confidential information.
The use of the fluorescent perovskite nanocrystal according to claim 6 in the security of confidential information, characterized in that the specific application method comprises the following steps:

(1) preparation of the precursor solution: the metal salt and the organic ligand constituting the MOF material are added to the solvent II, and then the ethanol and the ethylene glycol are continuously added, and completely dissolved by ultrasonication or stirring to obtain the MOF precursor liquid;

(2) Storage and encryption of confidential information: the precursor liquid is printed onto the substrate by printing technology, and dried and cleaned to obtain a substrate having information recorded by the MOF crystal, that is, a process of storing confidential information;

(3) Decryption of confidential information: the substrate on which the information is recorded is treated with a cationic halogenated salt to complete the conversion of MOF to the perovskite nanocrystal, that is, the information recorded by the MOF is decrypted;

(4) Repeated encryption and decryption process of confidential information: The above-mentioned decrypted substrate is treated with solvent III to completely quench the generated fluorescent signal, that is, the re-encryption process of confidential information.
The use of the fluorescent perovskite nanocrystal according to claim 7 for confidential information security, characterized in that the non-fluorescent substrate obtained in the step (4) is repeated again in steps (3) and (4), and can be regenerated and quenched. De-excitation, the process of multiple encryption and decryption of confidential information.
The use of the fluorescent perovskite nanocrystal according to claim 8 in the security of confidential information, characterized in that the printing technique described in the step (2) is conventionally gravure, lithographic, screen printing or embossing. The printing method and the non-printing method represented by inkjet; the method of treating the cationic halogenated salt in the step (3) is one of solution immersion, solution spray or gas phase contact reaction.