CN114989811B - Perovskite quantum dot and preparation method and application thereof - Google Patents

Perovskite quantum dot and preparation method and application thereof Download PDF

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CN114989811B
CN114989811B CN202210758646.0A CN202210758646A CN114989811B CN 114989811 B CN114989811 B CN 114989811B CN 202210758646 A CN202210758646 A CN 202210758646A CN 114989811 B CN114989811 B CN 114989811B
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CN114989811A (en
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田蜜蜜
邢泽咏
李小霞
郑策
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Wuxi Utmolight Technology Co Ltd
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Abstract

The invention relates to perovskite quantum dots, and a preparation method and application thereof. The preparation method comprises the following steps: (1) Mixing cesium halide, lead halide and solvent, heating to obtain CsPbBr X Cl 3‑X X is more than or equal to 0 and less than or equal to 3; (2) Mixing a molecular sieve precursor and a template agent, and sintering to obtain a semi-demolding molecular sieve; (3) Mixing halogen salt, strontium halide and the semi-demoulding molecular sieve obtained in the step (2), and heating to obtain mixed powder; (4) Mixing the phase CsPbBr obtained in step (1) X Cl 3‑X And (3) sintering the mixed powder obtained in the step (3) to obtain the perovskite quantum dot. The invention is realized by mixing the strontium-doped bulk CsPbBr X Cl 3‑X The stable and reversible effect photochromic material is obtained by sintering and depositing in the pore canal of the semi-demoulding molecular sieve. The preparation method is simple, low in cost and easy to realize large-scale mass production.

Description

Perovskite quantum dot and preparation method and application thereof
Technical Field
The invention belongs to the technical field of fluorescent quantum dots, relates to a preparation method of perovskite quantum dots, and particularly relates to perovskite quantum dots, and a preparation method and application thereof.
Background
Fluorescent anti-counterfeiting is a common anti-counterfeiting technology, wherein compared with a laser light source, an ultraviolet light source is safer and has lower cost. Conventionally, laVO is suitable for ultraviolet excitation of luminescent materials, such as lanthanide rare earth ion doped phosphors 4 :Eu 3 + Emits bright red light; laVO (LaVO) 4 :Dy 3+ Simultaneously has yellow light and blue light, and is integrally close toIn white light.
Some photochromic materials do not fluoresce or fluoresce themselves and do not discolor, but only undergo a change in system color after being irradiated by ultraviolet light, which subsequently needs to be recovered by the action of heat or light. In an organic system, the spiropyran and spirooxazine compounds generate heterolytic cleavage on C-O bond or C-N bond in colorless closed-loop molecules under the irradiation of ultraviolet light to form open-loop molecules with larger conjugated structures, so that the molecules are strongly absorbed in a visible light region to be colored, and the reverse reaction is generated under the action of visible light or heat to recover a colorless state (DOI: 10.1021/cr 9800715). Similar phenomena exist in inorganic systems, europium doped BaMgSiO 4 The material of (C) can realize that the system color can be bright pink or bleached under the irradiation of blue light and green light (DOI: 10.1063/1.3509417).
Thus enabling photochromic applications such as: in an organic system, a series of oxidized benzothiophenes replace diarylethenes, the ring-opened isomers of the compounds do not have fluorescence, and the ring-closed isomers after photoisomerization have yellow or green fluorescence (DOI: 10.1021/ja204583 e); in a single organic material system, a novel spiropyran functionalized diylanthracene derivative emits green light under 488nm/950nm light irradiation, changes green fluorescence into red fluorescence under 365/405nm light irradiation, and changes yellow fluorescence into red fluorescence under 800nm light irradiation, which can be reversibly recovered by 524nm light irradiation (DOI: 10.1002/anie.202117158). In an inorganic system, reversible fluorescence regulation and control can also be realized, such as Na with a lanthanide doped layered perovskite structure 0.5 Bi 2.5 Nb 2 O 9 And Na (Na) 0.5 Bi 4.5 Ti 4 O 15 After sunlight or visible light irradiation, the color of the material changes, the fluorescence intensity is reduced, the color and the fluorescence intensity of the material can be recovered after heating, but the fluorescence color of the material does not change all the time (DOI: 10.1021/acsami.5b12262); also materials capable of emitting fluorescence of different wavelengths at different excitation wavelengths, e.g. Bi 3+ Co-doped CaWO 4 :Yb 3+ ，Er 3+ The fluorescent powder has up-conversion and down-conversion dual-mode luminescence property and is excited by 980nm lightThe fluorescent light emitted was green, and the fluorescent light emitted was blue under 254nm excitation (DOI: 10.1016/j. Cej. 2021.132333).
However, when fluorescence of the common lanthanide rare earth ion doped inorganic luminescent material is observed by naked eyes, only a single color can be seen, mixed light can be distinguished by means of professional equipment, optical performance is easy to imitate, and anti-counterfeiting grade is low; in addition, some photochromic schemes are only photochromic materials, which are less distinguishable than the photochromic, and are not friendly to the naked eye, and require specialized equipment to detect the change; in the materials capable of achieving the photochromic effect, the photochromic effect is mostly excited by different light sources, the reverse color change is needed to be added with other lights or heat treatment, the use scene is greatly limited, the preparation scheme of the organic system material is complex, the organic system material is mostly applied in a liquid phase environment, and the commercial popularization is difficult.
Therefore, how to develop a stable and reversible effect photochromic material is a problem to be solved in the technical field of fluorescence anti-counterfeiting.
Disclosure of Invention
In view of the problems existing in the prior art, the invention provides a perovskite quantum dot, a preparation method and application thereof, and a strontium-doped bulk CsPbBr X Cl 3-X The stable and reversible effect photochromic material is obtained by sintering and depositing in the pore canal of the semi-demoulding molecular sieve.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing perovskite quantum dots, the method comprising the steps of:
(1) Mixing cesium halide, lead halide and solvent, heating to obtain CsPbBr X Cl 3-X ，0≤x≤3；
(2) Mixing a molecular sieve precursor and a template agent, and sintering to obtain a semi-demolding molecular sieve;
(3) Mixing halogen salt and the semi-demoulding molecular sieve obtained in the step (2), and heating to obtain mixed powder;
(4) Mixing the phase CsPbBr obtained in step (1) X Cl 3-X And (3) sintering the mixed powder obtained in the step (3) to obtain the perovskite quantum dot.
The invention provides a CsPbBr-based catalyst X Cl 3-X The preparation method of the perovskite quantum dot comprises the steps of mixing a strontium-doped bulk CsPbBr X Cl 3-X Sintering and depositing in the pore canal of the semi-demoulding molecular sieve, and collapsing the pore canal of the molecular sieve to lead CsPbBr in the sintering process X Cl 3-X The perovskite quantum dots are coated in the ultraviolet light continuous irradiation, so that the stable and reversible effect photochromic material is prepared, the positions of the luminescence peaks of the perovskite quantum dots are gradually changed under the continuous irradiation of ultraviolet light, the positions of the luminescence peaks before and after the photochromic are gradually changed from blue light (465-490 nm) to green light of 515nm, the front and back fluorescence changes obviously, and the identification degree is high. The irradiation is re-performed after the ultraviolet light is removed for a few minutes, the previous fluorescence color change process is repeated, the reversibility is good, and the additional light treatment or heat treatment is not needed.
0.ltoreq.x.ltoreq.3, which may be, for example, 0, 0.5, 1, 1.5, 2, 2.5 or 3, but is not limited to the values recited, other values not recited in the numerical range being equally applicable.
Preferably, the solvent of step (1) comprises an organic solvent.
Preferably, the organic solvent comprises an aprotic polar organic solvent.
Preferably, the aprotic polar organic solvent comprises any one or a combination of at least two of dimethyl sulfoxide (DMSO), N-Dimethylformamide (DMF), or N, N-Dimethylacetamide (DMA), typically but not limited to a combination comprising DMSO and DMF, a combination of DMF and DMA, a combination of DMSO and DMA, or a combination of DMF, DMA, and DMSO.
Preferably, the concentration of cesium halide in the solvent in the step (1) is 10-20 mmol/L, for example, 10mmol/L, 12mmol/L, 14mmol/L, 16mmol/L, 18mmol/L or 20mmol/L, but not limited to the recited values, and other non-recited values in the range of values are equally applicable.
Preferably, the concentration of the lead halide in the solvent in the step (1) is 10-20 mmol/L, for example, 10mmol/L, 12mmol/L, 14mmol/L, 16mmol/L, 18mmol/L or 20mmol/L, but not limited to the recited values, and other non-recited values in the range of values are equally applicable.
Preferably, the heating in step (1) is performed until the solvent evaporates.
Preferably, the heating temperature in step (1) is 90 to 120 ℃, for example, 90 ℃, 95 ℃, 100 ℃, 110 ℃, 115 ℃, or 120 ℃, but not limited to the values listed, and other values not listed in the numerical range are equally applicable.
Preferably, the templating agent of step (2) comprises a quaternary ammonium salt.
Preferably, the quaternary ammonium salt comprises cetyltrimethylammonium halide and/or cetyltrimethylphosphine halide.
Preferably, the molar ratio of template to molecular sieve precursor is 1 (60-70), which may be, for example, 1:61, 1:62, 1:64, 1:68 or 1:69, but is not limited to the recited values, as other non-recited values within the range of values are equally applicable.
Preferably, the mixing of step (2) further comprises ammonia.
Preferably, the sintering of step (2) comprises temperature-rising and constant-temperature sintering.
The heating rate is preferably 0.1 to 5 ℃ per minute, and may be, for example, 0.1 ℃ per minute, 0.5 ℃ per minute, 1 ℃ per minute, 2.5 ℃ per minute, 3 ℃ per minute, or 5 ℃ per minute, but the above-mentioned values are not limited thereto, and other values not shown in the numerical range are applicable.
The constant temperature sintering temperature is preferably 550 to 650 ℃, and may be 550 ℃, 570 ℃, 600 ℃, 620 ℃, 650 ℃, for example, but is not limited to the recited values, and other values not recited in the numerical range are equally applicable.
Preferably, the constant temperature sintering time is 30-80% of the total demolding sintering time, for example, 30%, 40%, 50%, 60%, 70% or 80%, but not limited to the recited values, and other non-recited values in the numerical range are equally applicable.
The full demolding sintering time refers to the sintering time required for the template agent to be completely separated from the molecular sieve. The invention controls the separation degree of the template agent and the molecular sieve by shortening the sintering time, and prepares the semi-demoulding molecular sieve.
The semi-demoulding molecular sieve is adopted in the preparation of the perovskite quantum dots, compared with the full-demoulding molecular sieve, the semi-demoulding molecular sieve is a smaller amount of template agent, and the existence of the small amount of template agent is beneficial to passivating the surface defects of crystal lattices and providing a halogen-rich environment at the same time, so that the semi-demoulding molecular sieve is more beneficial to halogen migration.
Preferably, the semi-demoulded molecular sieve of step (2) comprises M41S, more preferably MCM-41.
Preferably, the pore size of the semi-demoulded molecular sieve in step (2) is not more than 20nm, for example, 1nm, 5nm, 8nm, 10nm, 15nm or 20nm, but not limited to the recited values, and other non-recited values in the numerical range are equally applicable, preferably 3 to 10nm.
When the aperture of the semi-demolding molecular sieve is larger than 20nm, the excessive aperture easily causes the raw material to generate non-luminous non-functional phase instead of quantum dots.
Preferably, the molar ratio of the halide salt and the semi-demoulded molecular sieve in step (3) is (0.1 to 0.5): 1, and may be, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1 or 0.5:1, but is not limited to the recited values, and other non-recited values within the numerical range are equally applicable.
Preferably, the halide salt of step (3) comprises strontium halide.
Preferably, the strontium halide of step (3) and the CsPbBr of step (1) X Cl 3-X The molar ratio of (1) to (5) is 1, and may be, for example, 0.1:1, 0.5:1, 1:1, 1.5:1, 3:1, 5:1, but is not limited to the recited values, and other non-recited values within the numerical range are equally applicable.
CsPbBr 3 When Cl element is doped, the tolerance factor of the crystal lattice is reduced, and the crystal lattice becomes unstable, so that atoms with smaller atomic radius than Cs are needed to be added to stabilize the crystal lattice, and strontium element is doped to make the crystal lattice relatively stable, but a large number of defects still exist in the crystal lattice. Under the excitation of ultraviolet light, the quantum dot firstly emits CsPbBr x Cl 3-x The characteristic peak of (C) is then trapped by the defect due to partial excitation electron, a weak electric field is locally formed, the coulomb force causes Pb-Cl bond to break, cl atoms gradually migrate to the crystal boundary, local halogen separation is caused, and CsPbBr is the main component in the crystal lattice x Mainly, the peak was shown to be 515 nm. When the light is lost, the electric field is lost, and the halogen vacancies due to Cl migration are replenished by Cl atoms that migrate due to the large difference in halogen concentration.
Preferably, the mixing of step (3) is performed in a solvent.
Preferably, the solvent comprises water.
Preferably, the heating in step (3) is performed until the solvent evaporates.
Preferably, the heating temperature in step (3) is 90 to 120 ℃, for example, 90 ℃, 95 ℃, 100 ℃, 110 ℃, 115 ℃, or 120 ℃, but not limited to the values listed, and other values not listed in the numerical range are equally applicable.
Preferably, the semi-demolded molecular sieve of step (4) is combined with a bulk CsPbBr X Cl 3-X The molar ratio of (2) is 1 (0.01-0.05), and may be, for example, 1:0.01, 1:0.02, 1:0.03, 1:0.04 or 1:0.05, but is not limited to the recited values, and other non-recited values within the numerical range are equally applicable.
Preferably, the sintering in step (4) comprises heating and maintaining a constant temperature after heating.
Preferably, the elevated temperature includes a first elevated temperature and a second elevated temperature.
Preferably, the sintering of step (4) comprises a first elevated temperature, a first constant temperature, a second elevated temperature, and a second constant temperature.
Preferably, the first temperature is raised at a rate of 5 to 10 ℃ per minute, for example, 5 ℃ per minute, 6 ℃ per minute, 7 ℃ per minute, 8 ℃ per minute, 9 ℃ per minute or 10 ℃ per minute, but the first temperature is not limited to the recited values, and other values not recited in the numerical range are equally applicable.
Preferably, the temperature of the first constant temperature is 50 to 150 ℃ higher than the melting point of the lead halide, for example, 50 ℃, 80 ℃, 100 ℃, 120 ℃ or 150 ℃, but not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the first constant temperature is maintained for 10 to 30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes, but the present invention is not limited to the recited values, and other non-recited values in the range of values are equally applicable.
Preferably, the second temperature is raised at a rate of 10 to 20 ℃ per minute, for example, 10 ℃ per minute, 12 ℃ per minute, 14 ℃ per minute, 16 ℃ per minute, 18 ℃ per minute, or 20 ℃ per minute, but the second temperature is not limited to the recited values, and other values not recited in the numerical range are equally applicable.
Preferably, the second constant temperature is 50 ℃ to 150 ℃ higher than the collapse temperature of the semi-demoulded molecular sieve, for example, 50 ℃, 80 ℃, 100 ℃, 120 ℃ or 150 ℃, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the second constant temperature is maintained for 30 to 50min, for example, 30min, 35min, 40min, 45min or 50min, but not limited to the recited values, and other non-recited values in the range of values are equally applicable.
As a preferred technical scheme of the preparation method according to the first aspect of the present invention, the preparation method comprises the following steps:
(1) Mixing cesium halide, lead halide and organic solvent, heating at 90-120 deg.c to dry the organic solvent to obtain CsPbBr phase X Cl 3-X ，0≤x≤3；
The concentration of cesium halide in the solvent is 10-20 mmol/L; the concentration of the lead halide in the solvent is 10-20 mmol/L;
(2) Mixing a molecular sieve precursor, a template agent and ammonia water, and carrying out constant-temperature sintering at the temperature of 550-650 ℃ at the speed of 0.1-5 ℃/min to obtain a semi-demoulding molecular sieve; the constant-temperature sintering time is 30-80% of the total demoulding sintering time;
the molar ratio of the template agent to the molecular sieve precursor is 1 (60-70); the aperture range of the semi-demoulding molecular sieve is not more than 20nm;
(3) Mixing halogen salt, the semi-demolding molecular sieve obtained in the step (2) and water, and heating to water at the temperature of 90-120 ℃ to evaporate to dryness to obtain mixed powder;
the mol ratio of the halogen salt to the semi-demoulding molecular sieve is (0.1-0.5): 1;
the halogen salt comprises strontium halide, strontium halide and CsPbBr as described in step (1) X Cl 3-X The molar ratio of (1) to (5) is 1;
(4) According to the half-demoulding molecular sieve and the phase CsPbBr X Cl 3-X The molar ratio of (1) (0.01-0.05), and the phase CsPbBr obtained in the step (1) is mixed X Cl 3-X And (3) carrying out first temperature rise and first constant temperature at the speed of 5-10 ℃/min for 10-30 min, and then carrying out second temperature rise and second constant temperature at the speed of 10-20 ℃/min for 30-50 min to obtain the perovskite quantum dot;
the temperature of the first constant temperature is 50-150 ℃ and is higher than the melting point of lead halide; the temperature of the second constant temperature is 50-150 ℃ which is higher than the collapse temperature of the semi-demoulding molecular sieve.
In a second aspect, the present invention provides a perovskite quantum dot, the perovskite quantum dot being obtainable by a method of preparation as described in the first aspect.
In a third aspect, a use of the perovskite quantum dot according to the second aspect for fluorescent anti-counterfeiting.
By the technical scheme, the invention has the following beneficial effects:
(1) The invention provides a CsPbBr-based catalyst X Cl 3-X The preparation method of the perovskite quantum dot comprises the steps of mixing a strontium-doped bulk CsPbBr X Cl 3-X Sintering and depositing in the pore canal of the semi-demoulding molecular sieve, and collapsing the pore canal of the molecular sieve to lead CsPbBr in the sintering process X Cl 3-X Is coated in the fluorescent powder to prepare the stable and reversible-effect photochromic material. The preparation method is simple, low in cost and easy to realize large-scale mass production.
(2) Under the continuous irradiation of ultraviolet light, the perovskite quantum dot prepared by the method provided by the invention has the advantages that the luminescence peak position is gradually changed, the luminescence peak positions before and after the photochromic change are gradually changed from blue light (465-490 nm) to green light of 515nm, the front and back fluorescence change is obvious, and the identification degree is high. Re-irradiation after several minutes after the removal of the ultraviolet light will repeat the previous fluorescence discoloration process, with good reversibility and without additional irradiation or heat treatment.
Drawings
FIG. 1 is a graph of the emission peak of the perovskite quantum dot according to example 1 as a function of ultraviolet light irradiation time.
Detailed Description
The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.
Example 1
The embodiment provides a preparation method of perovskite quantum dots, which comprises the following steps:
(1) Mixing cesium bromide, lead chloride and DMSO, heating at 120deg.C to evaporate solvent to obtain CsPbBrCl 2 ；
The concentration of cesium bromide is 17.5mmol/L; the concentration of the lead chloride is 17.5mmol/L;
(2) Mixing 30mL of tetraethoxysilane, 2.2mmol of hexadecyl trimethyl ammonium bromide and 4.2mL of ammonia water (2.5 wt%), stirring and dissolving in water, performing suction filtration to obtain powder, heating the powder at a speed of 1 ℃/min, and performing constant-temperature sintering for 2 hours at a temperature of 600 ℃ to obtain a semi-demoulding molecular sieve MCM-41;
the constant-temperature sintering time is 50% of the total demoulding sintering time;
the aperture range of the semi-demoulding molecular sieve MCM-41 is 2-5 nm;
(3) Mixing potassium bromide, strontium chloride and the semi-demoulded molecular sieve MCM-41 obtained in the step (2) with water, heating to water at 100 ℃ and evaporating to dryness to obtain mixed powder;
the molar ratio of the potassium bromide to the semi-demoulding molecular sieve MCM-41 is 0.083:1; the mole ratio of the strontium chloride to the semi-demoulding molecular sieve MCM-41 is0.083:1; the strontium chloride and the CsPbBrCl of step (1) 2 The molar ratio of (2) to (1) is 2.3:1;
(4) According to the semi-demoulding molecular sieve MCM-41 and the phase CsPbBrCl 2 The molar ratio of CsPbBrCl obtained in step (1) was mixed at 1:0.035 2 And (3) heating the mixed powder obtained in the step (3) to 600 ℃ at a first heating rate of 5 ℃/min, then heating the mixed powder at a first constant temperature of 20min, heating the mixed powder at a second heating rate of 15 ℃/min to 800 ℃, and heating the mixed powder at a second constant temperature of 40min to obtain the perovskite quantum dot;
the temperature of the first constant temperature is higher than the melting point of lead chloride; the second constant temperature is higher than the collapse temperature of the semi-demoulded molecular sieve.
Under the irradiation of ultraviolet light, the perovskite quantum dots in the embodiment prolong the irradiation time (1 s to 8 s), the visible luminescence of naked eyes changes from blue to green, and the luminescence peak position of the perovskite quantum dots in the luminescence spectrum gradually changes from a wide peak position of 465nm to 490nm to a narrow peak position of 515 nm.
Example 2
The embodiment provides a method for preparing perovskite quantum dots, except that in the step (3), strontium chloride is replaced by a strontium halide mixture with equal molar weight, the strontium halide mixture is strontium chloride and strontium bromide with a molar ratio of 1:1, and the strontium halide mixture and CsPbBrCl in the step (1) 2 The molar ratio of (2) 3:1, the remainder of the process was identical to that of example 1.
The perovskite quantum dots in the embodiment are irradiated by ultraviolet light, so that the irradiation time is prolonged, and the visible luminescence of naked eyes is changed from blue to green.
Example 3
The present example provides a method for preparing perovskite quantum dots, and the process steps are the same as in example 1 except that strontium chloride in step (3) is replaced with equimolar amount of strontium bromide.
The perovskite quantum dots in the embodiment are irradiated by ultraviolet light, so that the irradiation time is prolonged, and the visible luminescence of naked eyes is changed from blue to green.
Example 4
The present embodiment provides a method for preparing perovskite quantum dots, which is different from embodiment 1 only in step (3), specifically as follows:
mixing potassium bromide, strontium chloride and the semi-demoulded molecular sieve MCM-41 obtained in the step (2) with water, heating to water at 100 ℃ and evaporating to dryness to obtain mixed powder;
the molar ratio of the potassium bromide to the semi-demoulding molecular sieve MCM-41 is 0.1632:1; the mole ratio of the strontium chloride to the semi-demoulding molecular sieve MCM-41 is 0.0028:1; the strontium chloride and the CsPbBrCl of step (1) 2 The molar ratio of (2) was 0.08:1.
Strontium halide and CsPbBr as described in step (1) in this example X Cl 3-X The molar ratio of the perovskite quantum dots is not in the preferred range of (0.1-5): 1, the content of strontium halide in the preparation method is reduced, and the prepared perovskite quantum dots have only weak fluorescence color-changing effect under ultraviolet irradiation, are not obvious in color change and are difficult to distinguish by naked eyes.
Example 5
The present embodiment provides a method for preparing perovskite quantum dots, which is different from embodiment 1 only in step (3), specifically as follows:
mixing potassium bromide, strontium chloride and the semi-demoulded molecular sieve MCM-41 obtained in the step (2) with water, heating to water at 100 ℃ and evaporating to dryness to obtain mixed powder;
the molar ratio of the potassium bromide to the semi-demoulding molecular sieve MCM-41 is 0.083:1; the mole ratio of the strontium chloride to the semi-demoulding molecular sieve MCM-41 is 0.182:1; the strontium chloride and the CsPbBrCl of step (1) 2 The molar ratio of (2) was 5.2:1.
Strontium halide and CsPbBr as described in step (1) in this example X Cl 3-X The molar ratio of the perovskite quantum dot is not in the preferred range of (0.1-5): 1, the content of strontium halide in the preparation method is more, the blue fluorescence is immediately converted into green fluorescence under the irradiation of ultraviolet light, the color change process is too fast, and the perovskite quantum dot is difficult to distinguish by naked eyes.
Example 6
This example provides a method for preparing perovskite quantum dots, and the process steps are the same as in example 1, except that strontium chloride in step (3) is replaced with equimolar amount of potassium bromide.
The perovskite quantum dots of the embodiment have no photochromic fluorescence effect under ultraviolet irradiation.
Example 7
The present example provides a method for preparing perovskite quantum dots, and the other process steps are the same as those of example 1, except that the temperature rising rate in step (2) is 7 ℃/min.
In the embodiment, the temperature rising speed is too high, so that the template agent is not combusted sufficiently, part of carbon remains, carbon is wrapped in the molecular sieve and cannot be removed in the preparation process, and the perovskite quantum dot is blackened.
Example 8
The present example provides a method for preparing perovskite quantum dots, and the process steps are the same as those of example 1, except that the constant temperature sintering temperature in step (2) is 500 ℃.
In the embodiment, the constant-temperature sintering temperature is too low, and the residual template agent is too much, so that the subsequent quantum dots entering the molecular sieve are reduced, and the fluorescence of the perovskite quantum dots is weak.
Example 9
The present example provides a method for preparing perovskite quantum dots, and the process steps are the same as those of example 1, except that the constant temperature sintering temperature in step (2) is 700 ℃.
In the embodiment, when the molecular sieve is demoulded, the sintering temperature is too high, so that the molecular sieve collapses in advance, the subsequent quantum dot precursor cannot enter the pore canal of the molecular sieve, and the prepared perovskite quantum dot has no fluorescence.
Example 10
The present example provides a method for preparing perovskite quantum dots, and the remaining process steps are the same as in example 1, except that the constant temperature sintering time in step (2) is 20% of the total demolding sintering time.
In the embodiment, the sintering time is short, so that the residual template agent is excessive, the subsequent quantum dots entering the molecular sieve are reduced, and the fluorescence of the prepared perovskite quantum dots is weak.
Example 11
The present example provides a method for preparing perovskite quantum dots, and the remaining process steps are the same as in example 1, except that the constant temperature sintering time in step (2) is 90% of the total demolding sintering time.
The sintering time of the embodiment is long, the template agent almost has no residue, and the prepared perovskite quantum dot almost cannot observe the fluorescence color change effect.
Example 12
This example provides a method for preparing perovskite quantum dots, which is otherwise identical to example 1, except that the pore size range of the semi-demoulded molecular sieve MCM-41 is 25 nm.
The perovskite quantum dots in the embodiment do not emit light under ultraviolet irradiation, and the perovskite quantum dots are not generated due to the fact that materials are agglomerated due to the fact that the aperture is too large.
Comparative example 1
The comparative example provides a method for preparing perovskite quantum dots, and the rest of the process steps are the same as those of example 1 except that the constant-temperature sintering time in the step (2) is 5 hours, and the obtained total demoulding molecular sieve MCM-41 is obtained.
The perovskite quantum dots of the comparative example have no photochromic fluorescence effect under ultraviolet irradiation.
In conclusion, under the continuous irradiation of ultraviolet light, the perovskite quantum dot prepared by the method has the advantages that the luminescence peak position is gradually changed, the luminescence peak positions before and after the photochromic change are gradually changed from blue light (465-490 nm) to green light of 515nm, and the front and back fluorescence change is obvious and the identification degree is high. The irradiation is re-performed after the ultraviolet light is removed for a few minutes, the previous fluorescence color change process is repeated, the reversibility is good, and the additional light treatment or heat treatment is not needed.
The detailed structural features of the present invention are described in the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be apparent to those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope of the present invention and the scope of the disclosure.

Claims (33)

1. The preparation method of the perovskite quantum dot is characterized by comprising the following steps of:
(1) Mixing cesium halide, lead halide and solvent, heating to obtain CsPbBr X Cl 3-X ，0＜x＜3；
(2) Mixing a molecular sieve precursor and a quaternary ammonium salt template agent, and sintering to obtain a semi-demoulded molecular sieve MCM-41;
(3) Mixing strontium halide with the semi-demoulded molecular sieve MCM-41 obtained in the step (2), and heating to obtain mixed powder;
(4) Mixing the phase CsPbBr obtained in step (1) X Cl 3-X And (3) sintering the mixed powder obtained in the step (3) to obtain the perovskite quantum dot.
2. The method of claim 1, wherein the solvent in step (1) comprises an organic solvent.
3. The method of preparing perovskite quantum dots according to claim 2, wherein the organic solvent comprises an aprotic polar organic solvent.
4. A method of preparing a perovskite quantum dot according to claim 3, wherein the aprotic polar organic solvent comprises any one or a combination of at least two of dimethyl sulfoxide, N-dimethylformamide or N, N-dimethylacetamide.
5. The method for preparing perovskite quantum dots according to claim 1, wherein the concentration of cesium halide in the solvent in the step (1) is 10-20 mmol/L.
6. The method for preparing perovskite quantum dots according to claim 1, wherein the concentration of the lead halide in the solvent in the step (1) is 10-20 mmol/L.
7. The method of claim 1, wherein the heating in step (1) is performed until the solvent evaporates.
8. The method for preparing perovskite quantum dots according to claim 1, wherein the heating temperature in step (1) is 90-120 ℃.
9. The method for preparing perovskite quantum dots according to claim 1, wherein the molar ratio of the template agent to the molecular sieve precursor is 1 (60-70).
10. The method of claim 1, wherein the mixing in step (2) further comprises ammonia.
11. The method of claim 1, wherein the sintering in step (2) comprises temperature-increasing and constant-temperature sintering.
12. The method for preparing perovskite quantum dots according to claim 11, wherein the heating rate is 0.1-5 ℃/min.
13. The method for preparing perovskite quantum dots according to claim 11, wherein the constant temperature sintering temperature is 550-650 ℃.
14. The method for preparing perovskite quantum dots according to claim 11, wherein the constant temperature sintering time is 30-80% of the total demoulding sintering time.
15. The method of claim 1, wherein the semi-demoulded molecular sieve in step (2) has a pore size in the range of not more than 20nm.
16. The method for preparing perovskite quantum dots according to claim 1, wherein the pore size of the semi-demoulded molecular sieve in step (2) is 3-10 nm.
17. The method of claim 1, wherein the molar ratio of strontium halide to semi-releasing molecular sieve in step (3) is (0.1-0.5): 1.
18. The method of claim 1, wherein the strontium halide in step (3) and the CsPbBr in step (1) are used as the quantum dots X Cl 3-X The molar ratio of (1) to (0.1-5): 1.
19. The method of claim 1, wherein the mixing in step (3) is performed in a solvent.
20. The method of claim 19, wherein the solvent comprises water.
21. The method of claim 1, wherein the heating in step (3) is performed until the solvent evaporates.
22. The method for preparing perovskite quantum dots according to claim 1, wherein the heating temperature in step (3) is 90-120 ℃.
23. The method of claim 1, wherein the semi-demoulded molecular sieve of step (4) is combined with a bulk phase CsPbBr X Cl 3-X The molar ratio of (2) is 1 (0.01-0.05).
24. The method of claim 1, wherein the sintering in step (4) comprises heating and maintaining a constant temperature after heating.
25. The method of claim 24, wherein the elevated temperature comprises a first elevated temperature and a second elevated temperature.
26. The method of claim 1, wherein the sintering in step (4) comprises a first elevated temperature, a first constant temperature, a second elevated temperature, and a second constant temperature.
27. The method of claim 26, wherein the first temperature is raised at a rate of 5 to 10 ℃/min.
28. The method of claim 26, wherein the first constant temperature is 50 ℃ to 150 ℃ above the melting point of the lead halide.
29. The method of claim 26, wherein the first constant temperature is for 10 to 30 minutes.
30. The method of claim 26, wherein the second temperature is raised at a rate of 10 to 20 ℃/min.
31. The method of claim 26, wherein the second constant temperature is 50 ℃ to 150 ℃ above the collapse temperature of the semi-demoulded molecular sieve.
32. The method of claim 26, wherein the second constant temperature is for 30-50 min.
33. A method of preparing perovskite quantum dots according to any one of claims 1 to 32, comprising the steps of:
(1) Mixing cesium halide, lead halide and organic solvent, heating at 90-120 deg.c to organicEvaporating the solvent to dryness to obtain a bulk CsPbBr phase X Cl 3-X ，0＜x＜3；
The concentration of cesium halide in the solvent is 10-20 mmol/L; the concentration of the lead halide in the solvent is 10-20 mmol/L;
(2) Mixing a molecular sieve precursor, a template agent and ammonia water, and carrying out constant-temperature sintering at the temperature of 550-650 ℃ at the speed of 0.1-5 ℃/min to obtain a semi-demoulding molecular sieve; the constant-temperature sintering time is 30-80% of the total demoulding sintering time;
the molar ratio of the template agent to the molecular sieve precursor is 1 (60-70); the aperture range of the semi-demoulding molecular sieve is not more than 20nm;
(3) Mixing strontium halide, the semi-demolding molecular sieve obtained in the step (2) and water, and heating to water at the temperature of 90-120 ℃ to evaporate to dryness to obtain mixed powder;
the mole ratio of the strontium halide to the semi-demoulding molecular sieve is (0.1-0.5): 1;
the strontium halide and the CsPbBr of step (1) X Cl 3-X The molar ratio of (1) to (5) is 1;
(4) According to the half-demoulding molecular sieve and the phase CsPbBr X Cl 3-X The molar ratio of (1) (0.01-0.05), and the phase CsPbBr obtained in the step (1) is mixed X Cl 3-X And (3) carrying out first temperature rise and first constant temperature at the speed of 5-10 ℃/min for 10-30 min, and then carrying out second temperature rise and second constant temperature at the speed of 10-20 ℃/min for 30-50 min to obtain the perovskite quantum dot;
the temperature of the first constant temperature is 50-150 ℃ and is higher than the melting point of lead halide; the temperature of the second constant temperature is 50-150 ℃ which is higher than the collapse temperature of the semi-demoulding molecular sieve.
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