Perovskite fluorescent material, preparation method and reversible luminescence color changing method

Abstract

The present invention discloses a perovskite fluorescent material, a preparation method and a reversible luminescence color change method, which belong to the field of optical anti-counterfeiting technology. The preparation method comprises the following steps: mixing a DMF solution of PbBr2 with a molecular sieve MCM-41 evenly, standing and calcining; then adding a CsBr aqueous alcohol solution, drying and calcining, and taking out at high temperature to obtain a CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material. The present invention adopts a two-step synthesis method to synthesize CsPbBr3 / Cs4PbBr6 perovskite quantum dots in the pores of the molecular sieve MCM-41. The CsPbBr3 / Cs4PbBr6@MCM-41 composite material can enhance the reversible luminescence intensity and reversible luminescence repeatability.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical anti-counterfeiting, and specifically relates to a perovskite fluorescent material, a preparation method and a reversible luminescence color changing method. Background Art

[0002] Stimuli-responsive luminescent materials are materials that can reversibly switch their luminescence intensity and color by exposure to external stimuli such as light, heat, pressure, moisture, and other chemical environments. Due to their desirable functions in these potential applications, they have attracted increasing attention in the field of industrial technology. (For example, daylight-changing glasses, smart windows, data encryption, and optical anti-counterfeiting) In recent years, lead halide perovskites have become fascinating stimuli-responsive luminescent materials due to their low formation energy and excellent optical properties. They are easy to prepare and prone to change and degradation, and are more likely to undergo reversible chemical and structural transformations under the stimulation of light, heat, pressure, water, and chemical environments.

[0003] Synthesizing CsPbBr3 in porous materials was originally another method to improve the stability of perovskites. Currently, the materials reported include zeolites, porous SiO2, porous Al2O3, porous glass, etc. Since the perovskite crystals in porous materials are not completely isolated from the external environment, composite materials are often used for external environmental stimulus-responsive materials. In recent years, composite materials such as CsPbBr3@mesoporous SiO2 and EMT-CsPbBr3 have been used in various aspects of optical anti-counterfeiting. However, problems with stimulus-responsive luminescent materials include poor sensitivity, poor reversibility and repeatability, a single application scenario, a long response time, poor controllability, and poor color tunability.

[0004] Patent CN109987625B discloses a method for achieving reversible transformation of halogen perovskite nanocrystals, in which CsPbX3 nanocrystals are prepared within the pores of a mesoporous support. The method utilizes water mist and drying to achieve reversible transformation of CsPbX3 nanocrystals to CsPb2X5 nanocrystals, achieving controllable transformation conditions and rapid transformation speed. However, the resulting material suffers from poor cyclic stability during reversible transformation. Summary of the Invention

[0005] In response to the shortcomings of the above-mentioned prior art, the present invention provides a perovskite fluorescent material, a preparation method and a reversible luminescence color change method. The present invention adopts a two-step synthesis method to synthesize CsPbBr3 / Cs4PbBr6 perovskite quantum dots in the molecular sieve MCM-41. The CsPbBr3 / Cs4PbBr6@MCM-41 composite material can enhance the reversible luminescence intensity and reversible luminescence cycle stability.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a perovskite fluorescent material comprises the following steps:

[0008] (1) PbBr2 DMF solution and molecular sieve MCM-41 were mixed evenly, allowed to stand for 10-30 min and then calcined;

[0009] (2) Then, a CsBr aqueous alcohol solution was added, the powder was ground until dry, calcined, and taken out at high temperature to obtain a CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material.

[0010] As a preferred embodiment of the present invention, the concentration of PbBr2 in the PbBr2 DMF solution is 0.025M; the mass volume ratio of molecular sieve MCM-41 to the PbBr2 DMF solution is 0.1g:800μl.

[0011] As a preferred embodiment of the present invention, the concentration of CsBr in the CsBr hydroalcoholic solution is 0.1 M, the volume ratio of water to alcohol is 1.5:6.5; and the mass volume ratio of molecular sieve MCM-41 to the CsBr hydroalcoholic solution is 0.1 g:800 μl.

[0012] As a preferred embodiment of the present invention, the molecular sieve MCM-41 has a pore size of 2.5 nm and a particle size of 1-2 microns.

[0013] As a preferred embodiment of the present invention, in the step (1), the calcination temperature is 200° C. and the calcination time is 20-60 min.

[0014] As a preferred embodiment of the present invention, in the step (2), the calcination temperature is 200° C. and the calcination time is 20-60 min.

[0015] The present invention also claims protection for the perovskite fluorescent material prepared by the method for preparing the perovskite fluorescent material.

[0016] As a preferred embodiment of the present invention, the perovskite fluorescent material is CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material, and CsPbBr3 / Cs4PbBr6 is loaded in the pores of the molecular sieve MCM-41.

[0017] As a preferred embodiment of the present invention, the average particle size of the CsPbBr3 / Cs4PbBr6 is 3.4nm-3.6nm.

[0018] The present invention also claims protection for the reversible luminescence method of the perovskite fluorescent material, comprising: under 365nm excitation, the perovskite fluorescent material emits blue light, then adding water, the material converts the blue light into green light, and after heating to remove the water, it converts to blue light emission.

[0019] When water is added to the perovskite fluorescent material under 365nm ultraviolet light excitation, the CsPbBr3 / Cs4PbBr6 nanocrystals in the perovskite fluorescent material are converted into CsPbBr3 nanocrystals. After heating to remove water, the CsPbBr3 nanocrystals are further converted into CsPbBr3 / Cs4PbBr6 nanocrystals, which significantly improves the cyclic stability of the reversible luminescence of the perovskite fluorescent material.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the present invention adopts a two-step synthesis method to synthesize CsPbBr3 / Cs4PbBr6 perovskite quantum dots in the pores of the molecular sieve MCM-41, and utilizes the synergistic effect of CsPbBr3 and Cs4PbBr6, as well as the special structure of the pores of the molecular sieve MCM-41, so that the CsPbBr3 / Cs4PbBr6@MCM-41 composite material has strong reversible luminescence intensity and reversible luminescence cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the XRD spectrum of the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in Example 1.

[0022] Figure 2 This is the BET test of the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material and molecular sieve MCM-41 prepared in Example 1 using a fully automatic specific surface area and porosity analyzer.

[0023] Figure 3 TEM image and grain size statistics of the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in Example 1.

[0024] Figure 4 TEM image and grain size statistics of the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in Example 1 after adding water.

[0025] Figure 5 The normalized photoluminescence fluorescence spectrum of the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in Example 1 in its original state; adding water at room temperature under a 365nm xenon lamp; and removing the water by heating under a 365nm xenon lamp as the excitation light source.

[0026] Figure 6 The CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in Example 1 was added with water at room temperature and restored to its CIE1931 color coordinates under a xenon lamp with a wavelength of 365 nm as an excitation light source.

[0027] Figure 7 This is a recovery cycle diagram of the reversible luminescence change of the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in Example 1 at room temperature under a 365nm xenon lamp.

[0028] Figure 8 The CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in Example 1 is used for optical anti-counterfeiting applications in humidity sensing and information encryption through stamping and screen printing respectively.

[0029] In the figure, Initial state is the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material in its original state; wetting discolcration is the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material after adding water; heating recovery is the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material after heating to remove water. DETAILED DESCRIPTION

[0030] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0031] The purity of the raw materials PbBr2 and CsBr used in the examples and comparative examples of the present invention both reached 99.99%, and the purity of DMF reached 99.9%.

[0032] Example 1

[0033] A method for preparing a perovskite fluorescent material comprises the following steps:

[0034] (1) 800 μl of a 0.025 M PbBr2 solution in DMF was added dropwise to 0.1 g of molecular sieve MCM-41 (the pore size of the molecular sieve MCM-41 was 2.5 nm and the particle size was 1-2 μm), allowed to stand for 20 min, mixed with a pestle, and then calcined in a muffle furnace at 200°C for 30 min.

[0035] (2) Then add 800 μl of 0.1 M CsBr hydroalcohol solution (the volume ratio of water to alcohol is 1.5:6.5), grind until the powder is dry, put it into a corundum crucible, and burn it in a muffle furnace at 200 ° C for 30 minutes. Take it out at high temperature to obtain CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material.

[0036] The reversible luminescence method of the prepared CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material includes: under 365nm excitation, the perovskite fluorescent material emits blue light, then water is added, the material changes from blue light to green light, and after heating to remove water, it turns to blue light emission.

[0037] according to Figure 1 It can be seen that the present invention successfully synthesized the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material. It can be seen that before water is added, the perovskite fluorescent material is composed of MCM-41 and CsPbBr3 / Cs4PbBr6 nanocrystals; after adding water, the CsPbBr3 / Cs4PbBr6 nanocrystals are converted into CsPbBr3 nanocrystals, and after heating to remove water, the CsPbBr3 nanocrystals are converted into CsPbBr3 / Cs4PbBr6 nanocrystals.

[0038] pass Figure 2 It can be seen that the untreated molecular sieve MCM-41 and the successfully synthesized CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material were subjected to fully automatic specific surface area and porosity analyzer BET tests using the American Quantachrome Autosorb IQ3. The results showed that about 1 / 3 of the pore volume of the molecular sieve MCM-41 was occupied, indicating that CsPbBr3 / Cs4PbBr6 was successfully synthesized in the mesopores of the molecular sieve MCM-41.

[0039] according to Figure 3 and Figure 4 It can be seen that by introducing a small amount of water, the average particle size of the perovskite quantum dots in the molecular sieve changes from 3.44nm to 8.89nm, and the originally evenly distributed perovskite quantum dots also undergo some agglomeration. When heating is used to remove the water, the average particle size of the perovskite quantum dots in the molecular sieve returns to around 3.44nm. Thanks to the size change of the CsPbBr3 perovskite quantum dots in the molecular sieve, the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material achieves reversible luminescence color changes through a water-heating mode.

[0040] according to Figure 5 The present invention uses a Hitachi F-7000 fluorescence spectrophotometer to measure the photoluminescence (PL) spectrum of the perovskite composite fluorescent material before and after water addition and thermal recovery. The xenon lamp light source is selected as 365nm. After water addition, the photoluminescence peak moves from 474nm to 520nm, and can be restored to its initial state of around 470nm after heating. Under the excitation of ultraviolet light with a wavelength of 365nm, the CIE1931 color coordinates of the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material at room temperature after water addition and recovery are shown in the following table. Figure 6, you can clearly see the color change caused by adding water and thermal recovery.

[0041] according to Figure 7 It can be seen that the CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material cyclically emits light and changes color under the "add water-heating" mode five times, and this phenomenon is highly repeatable and tends to be stable after multiple cycles.

[0042] In order to confirm that CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent materials have application value in optical anti-counterfeiting, CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent materials were applied to seals, screen printing, etc. Figure 8 As shown, the carriers are filter paper, glass, PVC, etc. Since the patterns all have the characteristics of light-stimulated reversible hydrochromicity, they have considerable potential and value in the field of optical anti-counterfeiting.

[0043] Example 2

[0044] A method for preparing a perovskite fluorescent material comprises the following steps:

[0045] (1) 800 μl of a 0.025 M PbBr2 solution in DMF was added dropwise to 0.1 g of molecular sieve MCM-41 (the pore size of the molecular sieve MCM-41 was 2.5 nm and the particle size was 1-2 μm), allowed to stand for 10 min, mixed evenly with a pestle, and then calcined in a muffle furnace at 200°C for 20 min.

[0046] (2) Then add 800 μl of 0.1 M CsBr hydroalcohol solution (the volume ratio of water to alcohol is 1.5:6.5), grind until the powder is dry, put it into a corundum crucible, and burn it in a muffle furnace at 200 ° C for 60 minutes. Take it out at high temperature to obtain CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material.

[0047] The reversible luminescence method of the prepared CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material includes: under 365nm excitation, the perovskite fluorescent material emits blue light, then water is added, the material changes from blue light to green light, and after heating to remove water, it turns to blue light emission.

[0048] The CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in this example shifted its photoluminescence peak from 474nm to 520nm after the addition of water under 365nm light irradiation, and recovered to its initial state of approximately 470nm after heating. TEM testing of the sample revealed that the introduction of trace amounts of water caused the average particle size of the perovskite quantum dots within the molecular sieve to change from 3.60nm to 9.01nm, and that the previously uniformly distributed perovskite quantum dots also exhibited some agglomeration. After heating to remove the water, the average particle size of the perovskite quantum dots within the molecular sieve returned to approximately 3.60nm.

[0049] The CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in this example cyclically emits light and changes color under the "add water-heat" mode five times, and this phenomenon is highly repeatable and tends to be stable after multiple cycles.

[0050] Example 3

[0051] A method for preparing a perovskite fluorescent material comprises the following steps:

[0052] (1) 800 μl of a 0.025 M PbBr2 solution in DMF was added dropwise to 0.1 g of molecular sieve MCM-41 (the pore size of the molecular sieve MCM-41 was 2.5 nm and the particle size was 1-2 μm), allowed to stand for 30 min, mixed evenly with a pestle, and then calcined in a muffle furnace at 200°C for 60 min.

[0053] (2) Then add 800 μl of 0.1 M CsBr hydroalcohol solution (the volume ratio of water to alcohol is 1.5:6.5), grind until the powder is dry, put it into a corundum crucible, and burn it in a muffle furnace at 200 ° C for 20 minutes. Take it out at high temperature to obtain CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material.

[0054] The reversible luminescence method of the prepared CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material includes: under 365nm excitation, the perovskite fluorescent material emits blue light, then water is added, the material changes from blue light to green light, and after heating to remove water, it turns to blue light emission.

[0055] The CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in this example shifted its photoluminescence peak from 474nm to 520nm upon addition of water under 365nm light irradiation, and recovered to its initial state of approximately 470nm upon heating. TEM analysis of the sample revealed that the introduction of trace amounts of water shifted the average particle size of the perovskite quantum dots within the molecular sieve from 3.52nm to 8.96nm, and the previously uniformly distributed perovskite quantum dots also exhibited some agglomeration. Upon heating to remove the water, the average particle size of the perovskite quantum dots within the molecular sieve returned to approximately 3.52nm.

[0056] The CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material prepared in this example cyclically emits light and changes color under the "add water-heat" mode five times, and this phenomenon is highly repeatable and tends to be stable after multiple cycles.

[0057] Comparative Example 1

[0058] A method for preparing a perovskite fluorescent material comprises the following steps:

[0059] (1) 800 μl of a 0.025 M PbBr2 solution in DMF was added dropwise to 0.1 g of a molecular sieve mesoporous Al2O3 (pore size of the molecular sieve Al2O3 was 18.84 nm), allowed to stand for 20 min, mixed with a pestle, and then calcined in a muffle furnace at 200°C for 30 min.

[0060] (2) Then, 800 μl of 0.1 M CsBr aqueous alcohol solution (water-alcohol volume ratio of 1.5:6.5) was added, and the powder was ground until dry and placed in a corundum crucible. The powder was fired in a muffle furnace at 200 °C for 30 min and taken out at high temperature to obtain CsPbBr3 / Cs4PbBr6@Al2O3 perovskite fluorescent material.

[0061] The prepared CsPbBr3 / Cs4PbBr6@Al2O3 perovskite fluorescent material cannot exhibit reversible color change luminescence, that is, under 365nm excitation, the perovskite fluorescent material emits green light, and then when water is added, the material still emits green light, and after heating to remove water, it still emits green light.

[0062] Comparative Example 2

[0063] A method for preparing a perovskite fluorescent material comprises the following steps:

[0064] (1) 800 μl of a 0.025 M PbBr2 solution in DMF was added dropwise to 0.1 g of SAPO-34 (pore size 0.4 nm, particle size 1-2 μm), allowed to stand for 20 min, mixed with a pestle, and then calcined in a muffle furnace at 200°C for 30 min.

[0065] (2) Then add 800 μl of 0.1M CsBr hydroalcohol solution (the volume ratio of water to alcohol is 1.5:6.5), grind until the powder is dry, put it into a corundum crucible, and burn it in a muffle furnace at 200 ° C for 30 minutes. Take it out at high temperature to obtain CsPbBr3 / Cs4PbBr6@SAPO-34 perovskite fluorescent material.

[0066] The prepared CsPbBr3 / Cs4PbBr6@SAPO-34 perovskite fluorescent material does not emit light under 365nm excitation and does not exhibit hydrochromic phenomenon.

[0067] Comparative Example 3

[0068] A method for preparing a perovskite fluorescent material comprises the following steps:

[0069] (1) 800 μl of a 0.1 M PbBr2 solution in DMF was added dropwise to 0.1 g of MCM-41 molecular sieve (the pore size of the MCM-41 molecular sieve was 2.5 nm and the particle size was 1-2 μm), allowed to stand for 20 min, mixed with a pestle, and then calcined in a muffle furnace at 200°C for 30 min.

[0070] (2) Then add 800 μl of 0.1 M CsBr hydroalcohol solution (the volume ratio of water to alcohol is 1.5:6.5), grind until the powder is dry, put it into a corundum crucible, and burn it in a muffle furnace at 200 ° C for 30 minutes. Take it out at high temperature to obtain CsPbBr3 / MCM-41 perovskite fluorescent material.

[0071] The reversible luminescence method of the prepared CsPbBr3@MCM-41 perovskite fluorescent material includes: under 365nm excitation, the perovskite fluorescent material emits blue light, then water is added, the material changes from blue light to green light, and then heats to remove water and turns back to blue light.

[0072] The CsPbBr3@MCM-41 perovskite fluorescent material prepared in this comparative example cyclically emits light and changes color under the "add water-heating" mode five times. The repeatability of this phenomenon is poor. After five cycles, the water-induced reversible luminescence intensity is significantly weakened. Moreover, after five cycles, the blue luminescence intensity of the CsPbBr3@MCM-41 perovskite fluorescent material weakens under 365nm excitation, emitting a weak blue light.

[0073] Comparative Example 4

[0074] A method for preparing a perovskite fluorescent material comprises the following steps: ultrasonically mixing 800 μl of a DMF solution containing 0.025 M PbBr2 and 0.1 M CsBr with 0.1 g of a molecular sieve MCM-41 (the molecular sieve MCM-41 has a pore size of 2.5 nm and a particle size of 1-2 μm) for 10 minutes, and then drying at 60°C to obtain a CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material.

[0075] The prepared CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material emits green light under 365nm excitation, and there is no water-induced reversible luminescence color change phenomenon.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a perovskite fluorescent material, characterized in that: The steps include: (1) A PbBr2 DMF solution was mixed evenly with a molecular sieve MCM-41 having a pore size of 2.5 nm and a particle size of 1-2 μm, and the mixture was allowed to stand for 10-30 min and then calcined at 200°C for 20-60 min; the concentration of PbBr2 in the PbBr2 DMF solution was 0.025 M; the mass volume ratio of the molecular sieve MCM-41 to the PbBr2 DMF solution was 0.1 g:800 μl; (2) Then, a CsBr aqueous alcohol solution was added, and the powder was ground until dry, and then calcined at 200°C for 20-60 minutes. The powder was taken out at high temperature to obtain a CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material; the concentration of CsBr in the CsBr aqueous alcohol solution was 0.1M, and the volume ratio of water to alcohol was 1.5:6.5; the mass volume ratio of molecular sieve MCM-41 to the CsBr aqueous alcohol solution was 0.1g:800μl.

2. The perovskite fluorescent material prepared by the preparation method of the perovskite fluorescent material according to claim 1, wherein the perovskite fluorescent material is CsPbBr3 / Cs4PbBr6@MCM-41 perovskite fluorescent material, CsPbBr3 / Cs4PbBr6 is loaded in the pores of the molecular sieve MCM-41; the average particle size of the CsPbBr3 / Cs4PbBr6 is 3.4nm-3.6nm.

3. The reversible luminescence color changing method of the perovskite fluorescent material according to claim 2, characterized in that: include: Under the excitation of 365nm ultraviolet light, the perovskite fluorescent material emits blue light. Then, when water is added, the material changes from blue light to green light. After heating at 50-80℃ to remove water, it turns to blue light emission.

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