A method for regulating the luminescence of lead halide perovskite quantum dots

Abstract

This invention provides a method for regulating the luminescence of lead halide perovskite quantum dots. The method involves adding a coumarin-3-carboxylic acid solution to the lead halide perovskite quantum dot stock solution, mixing thoroughly to obtain a mixed system, and then using light excitation of the mixed system with a wavelength between 400 nm and the cutoff wavelength of the lead halide perovskite quantum dots to quench the luminescence of the quantum dots. Replacing the mixed system with ultraviolet light excitation at a wavelength between 300-375 nm restores the luminescence of the quantum dots. This method can regulate the luminescence of most lead halide perovskite quantum dots, exhibiting high adaptability, which is beneficial for broadening the application of lead halide perovskite quantum dots in information encryption and storage.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot luminescence regulation, specifically including a method for regulating the luminescence of lead halide perovskite quantum dots. Background Technology

[0002] Surface ligand engineering has become a major research hotspot for perovskite quantum dots in recent years. By modifying the ligands anchored to the surface of quantum dots, the photophysical properties of perovskite quantum dots can be effectively tuned, thereby achieving desired application effects. For example, using bidentate ligands can effectively passivate defect states on the surface of quantum dots, prolonging the luminescence lifetime and improving the luminescence quantum efficiency; using polycyclic aromatic hydrocarbon ligands such as rhodamine B, 9-anthracarboxylic acid, and perylenecarboxylic acid can effectively enrich and extract the triplet energy of quantum dots, and has been applied in the fields of triplet annihilation upconversion and sensitized photoreactions; using ligands such as anthraquinone and fullerene can effectively extract electrons from quantum dots, enhancing their photocatalytic performance. Therefore, surface ligand engineering can effectively expand the functionality and application range of perovskite quantum dots.

[0003] Given the significant influence of surface ligands on the luminescence of perovskite quantum dots, it is theoretically feasible to manipulate the luminescence of perovskite quantum dots by anchoring specific organic molecules to the surface and controlling these organic ligands. Literature reports that aromatic organic ligands anchored around perovskite quantum dots typically quench the luminescence of the perovskite quantum dots through triplet energy transfer or electron transfer processes, thereby generating triplet states of organic compounds.

[0004] Lead halide perovskite quantum dots, as an emerging semiconductor quantum dot material, have advantages such as high luminescence quantum efficiency, easily tunable band gap, and simple synthesis methods. However, there are relatively few reports on achieving luminescence quenching and luminescence recovery of lead halide perovskite quantum dots through surface ligands, which has affected their development in information encryption and anti-counterfeiting. Summary of the Invention

[0005] To address the aforementioned problems in existing technologies, the present invention aims to provide a method for controlling the luminescence of lead halide perovskite quantum dots. By adding coumarin-3-carboxylic acid to the lead halide perovskite quantum dot stock solution, the lead halide perovskite quantum dots serve as the luminescence source, and coumarin-3-carboxylic acid acts as the medium for controlling the luminescence of the quantum dots. This allows for the control of the luminescence performance of the lead halide perovskite quantum dots by varying the wavelength of the excitation light.

[0006] To achieve the above objectives, the technical solution adopted by the present invention includes:

[0007] This invention discloses a method for regulating the luminescence of lead halide perovskite quantum dots. A coumarin-3-carboxylic acid solution is added to the lead halide perovskite quantum dot stock solution and mixed evenly to obtain a mixed system. The luminescence of the quantum dots is quenched by photoexcitation of the mixed system with a wavelength between 400 nm and the cutoff wavelength of the lead halide perovskite quantum dots. The luminescence of the quantum dots is restored by replacing the mixed system with ultraviolet light with a wavelength between 300-375 nm.

[0008] This invention proposes for the first time a method for regulating the luminescence of lead halide perovskite quantum dots using coumarin-3-carboxylic acid. Experiments show that when a mixed system of coumarin-3-carboxylic acid and lead halide perovskite quantum dots is excited with light with wavelengths between 400 nm and the cutoff wavelength of lead halide perovskite quantum dots, it is possible to ensure that coumarin-3-carboxylic acid is not excited while the lead halide perovskite quantum dots are excited. This allows coumarin-3-carboxylic acid to act as a surface ligand anchored on the lead halide perovskite quantum dots. Coumarin-3-carboxylic acid can induce the formation of surface ligands on lead halide perovskite quantum dots with different band gaps. By using surface-trapped states, effective quenching of quantum dot luminescence can be achieved without generating triplet compounds. If the mixed system is further excited by ultraviolet light with a wavelength of 300-375 nm, coumarin-3-carboxylic acid undergoes a decarboxylation photochemical reaction and desorbs from the surface of lead halide perovskite quantum dots, thus restoring the luminescence of the quantum dots. Therefore, the controllable luminescence of lead halide perovskite quantum dots can be achieved by using the anchoring of coumarin-3-carboxylic acid and desorption under ultraviolet light. This helps to broaden the application of lead halide perovskite quantum dots in the fields of information encryption and storage.

[0009] Furthermore, the chemical formula of the lead halide perovskite quantum dots is one or more of CsPbBr3, CsPbCl3, CsPbI3, and CsPbBr2Cl.

[0010] Currently reported compounds that can quench the luminescence of lead halide perovskite quantum dots (LHPK) are limited to quenching LHPK quantum dots with specific band gaps. No reports have been made of compounds like the one described in this invention, which can quench the luminescence of various LHPK quantum dots with a wide band gap. This invention utilizes coumarin-3-carboxylic acid to regulate the luminescence of LHPK quantum dots, demonstrating universality and effectiveness for various LHPK quantum dots, including CsPbBr3, CsPbCl3, CsPbI3, and CsPbBr2Cl. Based on this design concept, a hybrid system of coumarin-3-carboxylic acid and LHPK quantum dots can be applied to information encryption and storage. By exciting the hybrid system with different wavelengths, partial information can be revealed or hidden, achieving information encryption and storage.

[0011] Depending on the preparation method and conditions, lead halide perovskite quantum dots with different first exciton absorption peak positions can be obtained. In one specific embodiment, the lead halide perovskite quantum dots are selected from one of CsPbBr3 with a first exciton absorption peak of 455 nm or 503 nm, CsPbI3 with a first exciton absorption peak of 640 nm, and CsPbBr2Cl with a first exciton absorption peak of 480 nm.

[0012] Furthermore, when the wavelength is between 400 nm and the cutoff wavelength of lead halide perovskite quantum dots, coumarin-3-carboxylic acid is anchored on the surface of lead halide perovskite quantum dots to achieve quenching of quantum dot luminescence.

[0013] When the mixed system is re-excited by ultraviolet light with wavelengths in the range of 300-375 nm, coumarin-3-carboxylic acid desorbs from the surface of lead halide perovskite quantum dots to restore the luminescence of the quantum dots.

[0014] When determining the wavelength of ultraviolet light, considering that the maximum absorption wavelength of coumarin-3-carboxylic acid is 375nm, the mixing system was finally selected to be excited by ultraviolet light with a wavelength of 300-375nm, preferably 365nm.

[0015] Furthermore, the dispersing solvent used in the coumarin-3-carboxylic acid solution and the lead halide perovskite quantum dot stock solution is selected from one or more of n-hexane, toluene, and n-heptane; toluene is preferred.

[0016] Furthermore, the concentration of the lead halide perovskite quantum dot stock solution used in preparing the mixed system is 0.5-5 μM; for example, the concentration of the lead halide perovskite quantum dot stock solution used in preparing the mixed system can be 0.5 μM, 1 μM, 1.5 μM, 2 μM, 2.5 μM, 3 μM, 3.5 μM, 4 μM, 4.5 μM, 5 μM, etc., preferably 3-5 μM.

[0017] Furthermore, the concentration of the coumarin-3-carboxylic acid solution used in preparing the mixed system is 0.1-2 mM; for example, the concentration of the coumarin-3-carboxylic acid solution used in preparing the mixed system can be 0.1 mM, 0.2 mM, 0.3 mM, 0.4 mM, 0.5 mM, 0.6 mM, 0.7 mM, 0.8 mM, 0.9 mM, 1 mM, 1.1 mM, 1.2 mM, 1.3 mM, 1.4 mM, 1.5 mM, 1.6 mM, 1.7 mM, 1.8 mM, 1.9 mM, 2 mM, etc., preferably 1-2 mM.

[0018] Furthermore, the concentration ratio of the coumarin-3-carboxylic acid solution to the lead halide perovskite quantum dot stock solution is 200-1000:1; for example, the concentration ratio of the coumarin-3-carboxylic acid solution to the lead halide perovskite quantum dot stock solution can be 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1, etc.

[0019] Furthermore, the volume ratio of the coumarin-3-carboxylic acid solution to the lead halide perovskite quantum dot stock solution is 1:10.

[0020] Furthermore, the molar ratio of coumarin-3-carboxylic acid in the coumarin-3-carboxylic acid solution to lead halide perovskite quantum dots in the lead halide perovskite quantum dot stock solution is 20-100:1; exemplaryly, the molar ratio of coumarin-3-carboxylic acid in the coumarin-3-carboxylic acid solution to lead halide perovskite quantum dots in the lead halide perovskite quantum dot stock solution can be 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, etc.

[0021] Furthermore, the lead halide perovskite quantum dot stock solution is obtained by dispersing lead halide perovskite quantum dots in a dispersion solvent. The preparation process of lead halide perovskite quantum dots can refer to conventional preparation methods in the art. The method used in this invention is as follows:

[0022] Cesium-containing compounds, oleic acid, and octadecene are added to a reactor. After removing water and oxygen, the reactor is placed in an inert atmosphere to completely dissolve the cesium-containing compounds, obtaining a cesium precursor solution. The solution is then kept at a temperature above 100°C for later use.

[0023] Lead halides, zinc halides, oleic acid, oleylamine, and octadecene are added to another reactor. After removing water and oxygen, the mixture is heated to about 100°C to obtain a lead halide precursor solution.

[0024] Add the cesium precursor solution to the lead halide precursor solution, cool rapidly to room temperature after 2-3 minutes, centrifuge, collect the supernatant, then add acetone dropwise to the supernatant, centrifuge, collect the precipitate, and obtain lead halide perovskite quantum dots.

[0025] Furthermore, the lead halide is selected from one of lead chloride, lead bromide, and lead iodide; the zinc halide is selected from one of zinc chloride, zinc bromide, and zinc iodide; the halogen elements contained in the lead halide and the zinc halide are the same.

[0026] Furthermore, the cesium-containing compound is selected from one or more of cesium stearate, cesium carbonate, cesium sulfate, cesium acetate, and cesium oxalate.

[0027] Beneficial effects of this invention:

[0028] This invention provides a method for controlling the luminescence of lead halide perovskite quantum dots. By adding coumarin-3-carboxylic acid to the lead halide perovskite quantum dot stock solution, the luminescence performance of the lead halide perovskite quantum dots can be controlled by changing the excitation wavelength. Specifically, when the mixed system of coumarin-3-carboxylic acid and lead halide perovskite quantum dots is excited with light with a wavelength between 400 nm and the cutoff wavelength of lead halide perovskite quantum dots, coumarin-3-carboxylic acid will act as a surface ligand anchored on the lead halide perovskite quantum dots, effectively quenching the luminescence of the quantum dots by generating defect states, without producing triplet compounds. If the mixed system is then re-excited with ultraviolet light with a wavelength between 300-375 nm, coumarin-3-carboxylic acid will undergo a decarboxylation photochemical reaction and desorb from the surface of the lead halide perovskite quantum dots, thus restoring the luminescence of the quantum dots.

[0029] The method of regulating the luminescence of lead halide perovskite quantum dots using coumarin-3-carboxylic acid in this invention is universal and effective for various lead halide perovskite quantum dots, such as CsPbBr3, CsPbCl3, CsPbI3, and CsPbBr2Cl. This helps to broaden the application of lead halide perovskite quantum dots in the fields of information encryption and storage. Attached Figure Description

[0030] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the quenching and reduction of luminescence from perovskite quantum dots in Example 1 of the present invention.

[0032] Figure 2 The absorption spectra of the quantum dot-C3CA system with different amounts of C3CA added in Example 1 of the present invention are shown.

[0033] Figure 3 The emission spectra of the quantum dot-C3CA system under 430 nm excitation with different amounts of C3CA added in Example 1 of the present invention.

[0034] Figure 4 The absorption spectra of the quantum dot-C3CA system under different illumination times in Example 1 of this invention are obtained by excitation with a 365nm ultraviolet lamp.

[0035] Figure 5 The emission spectra of the quantum dot-C3CA system under different illumination times in Example 1 of the present invention are obtained by excitation with a 365nm ultraviolet lamp.

[0036] Figure 6 The absorption and emission spectra of the quantum dot-C3CA system in Example 1 of this invention before and after excitation by a 254nm ultraviolet lamp are shown.

[0037] Figure 7 The absorption and emission spectra of the quantum dots and the quantum dot-C3CA system in Example 2 of this invention are shown.

[0038] Figure 8 The absorption and emission spectra of the quantum dots and the quantum dot-C3CA system in Example 3 of this invention are shown.

[0039] Figure 9 The absorption and emission spectra of the quantum dots and the quantum dot-C3CA system in Example 4 of this invention are shown.

[0040] Figure 10 This is the absorption and emission spectrum of the quantum dot-C343 system prepared using Example 1 in Comparative Example 1 of the present invention.

[0041] Figure 11 This is the absorption and emission spectrum of the quantum dot-C343 system prepared using Example 2 in Comparative Example 1 of the present invention. Detailed Implementation

[0042] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] In addition, unless otherwise specified, all raw materials used in this invention can be obtained commercially available. Any range described in this invention includes the end value and any value between the end values, as well as any subrange formed by the end value or any value between the end values.

[0044] Example 1

[0045] 0.4 g of cesium carbonate (Cs₂CO₃), 1.75 mL of oleic acid (OA), and 15 mL of octadecene (ODE) were added to a three-necked flask and dehydrated and deoxygenated at 120 °C for 0.5 h. The mixture was then heated to 150 °C under argon protection until all the cesium carbonate powder was completely dissolved, yielding a cesium precursor solution. The temperature of the cesium precursor solution was maintained above 100 °C for later use.

[0046] 0.225 g lead bromide (PbBr2), 0.552 g zinc bromide (ZnBr2), 6 mL oleic acid, 6 mL oleylamine and 15 mL octadecene were added to another three-necked flask and degassed at 120 °C for 0.5 h. Then the temperature was lowered to 100 °C under argon protection to obtain a lead bromide precursor solution, which was kept at 100 °C.

[0047] 1.2 mL of cesium precursor solution was rapidly injected into the lead bromine precursor solution. After 2 min, the three-necked flask was placed in ice water to cool to room temperature. The resulting product was centrifuged at 4500 rpm for 5 min to remove unreacted salts, and the supernatant was collected. After standing for 2 h, the product was centrifuged again at 4500 rpm for 5 min, and the supernatant was collected. Acetone was added dropwise to the supernatant until the solution became turbid. Then, the precipitated perovskite was collected by centrifugation at 7500 rpm for 15 min to obtain CsPbBr3 quantum dots. After drying, the CsPbBr3 quantum dot stock solution (NCs) was obtained.

[0048] The obtained CsPbBr3 quantum dot stock solution was placed in a 1 cm quartz cell. UV-Vis absorption spectroscopy determined that the first exciton absorption peak of the quantum dots was at 503 nm. Based on the absorbance measured by UV-Vis, and according to the Lambert-Beer law, the concentration of the obtained CsPbBr3 quantum dot stock solution was approximately 5 μM.

[0049] A 1 mM solution of coumarin-3-carboxylic acid (C3CA) was prepared using toluene as the solvent. 0-500 μL of the C3CA solution was added to the prepared CsPbBr3 quantum dot stock solution, and the mixture was sonicated until homogeneous. The steady-state absorption spectra of each solution were then measured. Figure 2 ) and emission spectrum ( Figure 3 The C3CA solution was added in amounts of 0 μL, 50 μL, 100 μL, 150 μL, 200 μL, 250 μL, 350 μL, and 500 μL. Steady-state absorption spectra showed that with increasing C3CA content, the system gradually exhibited a characteristic C3CA peak at 340 nm, while the first exciton absorption peak of the quantum dots at 503 nm remained unchanged, indicating good stability of the quantum dot-C3CA system. The emission spectrum of the quantum dot-C3CA system (excitation wavelength of 430 nm) showed that with increasing C3CA content, the luminescence intensity of the quantum dots gradually decreased, indicating that C3CA effectively quenches the luminescence of the quantum dots. Subsequent UV-induced quantum dot luminescence experiments were conducted using a mixture of 200 μL C3CA and 2 mL quantum dots.

[0050] Ultraviolet light-controlled quantum dot luminescence experiment

[0051] The quantum dot-C3CA system was illuminated with a 15W ultraviolet lamp for 0-600s, and its steady-state absorption spectrum was measured. Figure 4 ) and emission spectrum ( Figure 5 The illumination time includes 0s, 30s, 60s, 120s, 180s, and 600s. From the figure, it can be seen that after 365nm illumination, the absorption peak of C3CA at 340nm in the quantum dot-C3CA system decreases, and the luminescence of the quantum dot is restored.

[0052] Since the decarboxylation reaction of C3CA only occurs under ultraviolet light above 300 nm, the 254 nm ultraviolet light used cannot modulate the luminescence of quantum dots. The absorption and emission spectra of the quantum dot-C3CA system after 10 min of 254 nm illumination were measured. Figure 6 This confirms that 254nm does not affect the luminescence of the quantum dot-C3CA system.

[0053] Example 2

[0054] Add 0.25g of cesium carbonate (Cs₂CO₃), 0.9mL of oleic acid (OA), and 9mL of octadecene (ODE) to a 25mL three-necked flask, heat to 120℃ and evacuate for 1 hour, then heat to 150℃ under an Ar atmosphere. After the Cs₂CO₃ is completely dissolved, a cesium precursor solution is obtained. Keep the temperature of the cesium precursor solution above 100℃ for later use.

[0055] In another three-necked flask, add 75 mg lead bromide (PbBr2), 184 mg zinc bromide (ZnBr2), 3 mL OA, 3.5 mL oleylamine, and 5 mL LODE. Heat to 120 °C and evacuate for 1 hour. Then, under argon protection, reduce the temperature to 100 °C to obtain a lead bromide precursor solution and keep warm.

[0056] 0.4 mL of cesium precursor solution was rapidly added to the lead-bromine precursor solution, and the reaction was terminated by placing the solution in an ice-water bath after 100 s. After the reaction was terminated, the solution was poured into a 50 mL centrifuge tube and centrifuged at 4000 rpm for 20 min to remove unreacted salts. After centrifugation, the supernatant was collected, and acetone was added dropwise until the supernatant just became turbid. The amount of acetone required for this step was approximately 3 times the volume of the supernatant (V / V). The turbid supernatant was centrifuged at 7800 rpm for 3 min, and the precipitate was collected to obtain CsPbBr3 quantum dots. The precipitate was dried in a vacuum oven at room temperature for 24 h, and then dispersed in n-hexane or toluene to obtain the CsPbBr3 quantum dot stock solution for later use. Its absorption and emission spectra were then measured. Figure 7 The first exciton absorption peak was confirmed to be located at 455 nm, proving that the quantum dot has a large band gap and a concentration of about 3 μM.

[0057] 200 μL of 2 mM C3CA was added to 2 mL of the prepared CsPbBr3 quantum dot stock solution, and the mixture was sonicated for 5 min to obtain the quantum dot-C3CA system. Its absorption and emission spectra were then measured. Figure 7 The excitation wavelength was 400 nm. The emission spectrum showed that C3CA also significantly quenched CsPbBr3 quantum dots with larger band gaps. Subsequently, the luminescence of the quantum dots was restored using a 15W 365nm ultraviolet lamp.

[0058] Example 3

[0059] Add 0.25g Cs2CO3, 0.98mL OA, and 9m LODE to a 25mL three-necked flask, evacuate at 120℃ for 1h, then raise the temperature to 150℃ to completely dissolve Cs2CO3 to obtain a cesium precursor solution, and keep it above 100℃ for use.

[0060] 0.25 g zinc iodide (ZnI2), 120 mg lead iodide (PbI2), 5 m LODE, 2 m LOAm and 2 mL bis(2,4,4-trimethylpentyl)phosphonic acid (TMMPA) were added to a 50 mL three-necked flask and evacuated at 120 °C for 1 h. Then the temperature was raised to 145 °C under an Ar atmosphere to obtain a lead-iodine precursor solution, which was kept at the temperature.

[0061] Add 0.4 mL of cesium precursor solution to the lead-iodine precursor solution. After reacting for 20 seconds, quickly transfer the three-necked flask to an ice-water bath. Once the reaction has stopped, pour the mixture into a centrifuge tube and centrifuge at 3500 rpm for 15 minutes to remove unreacted salt. Collect the supernatant and add ultra-dry methyl acetate until the supernatant becomes turbid. Collect the precipitate by centrifuging at 7800 rpm for 3 minutes. Disperse the dried quantum dot precipitate in hexane or toluene to obtain a CsPbI3 quantum dot stock solution with a concentration of approximately 5 μM and a first exciton absorption peak at 640 nm. Note that iodine perovskite will precipitate impurities after standing for a period of time; therefore, it is necessary to centrifuge and purify the iodine perovskite before use to remove impurities.

[0062] 200 μL of 2 mM C3CA was added to 2 mL of the prepared CsPbI3 quantum dot stock solution, and the mixture was sonicated for 5 min to obtain the quantum dot-C3CA system. Its absorption and emission spectra were then measured. Figure 8 The excitation wavelength was 500 nm. The emission spectrum revealed a significant quenching effect of C3CA on CsPbI3 quantum dots with a smaller band gap. Subsequently, the recovery of quantum dot luminescence was achieved using a 15W 365nm UV lamp.

[0063] Example 4

[0064] 16 mg Cs₂CO₃, 76 mg lead acetate dihydrate (Pb(CH₃COOH)₂·2H₂O), 0.3 mL OA, 1 mL LOAm, and 5 mL LODE were added to a 25 mL three-necked flask. The mixture was evacuated at 130 °C for 1 h to remove moisture and oxygen. Then, under Ar atmosphere protection, the temperature was raised to 170 °C. After the temperature stabilized, a mixed solution of 0.6 mmol benzoyl chloride and benzoyl bromide (0.2 mmol benzoyl chloride and 0.4 mmol benzoyl bromide) was injected. The three-necked flask was immediately placed in an ice-water bath to terminate the reaction. After the reaction was quenched, 10 mL of toluene was added to the three-necked flask, and the mixture was centrifuged at 4000 rpm for 10 min. The precipitate was collected to obtain CsPbBr₂Cl quantum dots, which were redispersed in toluene to obtain the CsPbBr₂Cl quantum dot stock solution for later use. Steady-state absorption spectroscopy showed that its concentration was approximately 5 μM, and the first exciton absorption peak was at 480 nm.

[0065] 200 μL of 2 mM C3CA was added to 2 mL of the prepared CsPbBr2Cl quantum dot stock solution, and the mixture was sonicated for 5 min to obtain the quantum dot-C3CA system. Its absorption and emission spectra were then measured. Figure 9 The excitation wavelength was 430 nm. The emission spectrum revealed a significant quenching effect of C3CA on CsPbBr2Cl quantum dots with a smaller band gap. Subsequently, the luminescence of the quantum dots was restored using a 15W 365nm UV lamp.

[0066] Comparative Example 1

[0067] The quantum dot-C3CA system enables UV-controlled quantum dot luminescence because C3CA can induce perovskite quantum dots with different band gaps to form surface trap states, thus effectively quenching quantum dot luminescence. Furthermore, C3CA can undergo a decarboxylation photochemical reaction under 365nm UV light, allowing the quantum dots to regain their luminescence. Therefore, C3CA possesses physicochemical properties not found in other dye molecules. 200 μL of 2mM coumarin 343 (C343) was added to the CsPbBr3 quantum dots in Examples 1 and 2, respectively. After sonication for 5 min, their absorption and emission spectra were measured. Figure 10 The absorption and emission spectra of the quantum dot-C343 system obtained by adding coumarin 343 to the CsPbBr3 quantum dots prepared in Example 1 are shown. Figure 11The absorption and emission spectra of the quantum dot-C343 system obtained by adding coumarin 343 to the CsPbBr3 quantum dots prepared in Example 2 were analyzed. It was found that C343 could only quench the luminescence of the quantum dots in Example 2, while the luminescence of the quantum dots in Example 1 could not be quenched. Therefore, C343 cannot quench the luminescence of perovskite quantum dots across the entire bandgap. Furthermore, C343 does not undergo a photochemical reaction under 365 nm light excitation; therefore, even if C343 can quench the CsPbBr3 quantum dots in Example 2, its luminescence cannot be restored by ultraviolet light.

[0068] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for controlling the luminescence of lead halide perovskite quantum dots, characterized in that, Coumarin-3-carboxylic acid solution was added to lead halide perovskite quantum dot stock solution and mixed evenly to obtain a mixed system. The quantum dot luminescence was quenched by photoexcitation of the mixed system with wavelengths between 400 nm and the cutoff wavelength of lead halide perovskite quantum dots. The quantum dot luminescence was restored by replacing the mixed system with ultraviolet light excitation with wavelengths between 300-375 nm. The chemical formula of the lead halide perovskite quantum dots is one or more of CsPbBr3, CsPbCl3, CsPbI3, and CsPbBr2Cl.

2. The method according to claim 1, characterized in that, The lead halide perovskite quantum dots are selected from one of the following: CsPbBr3 with a first exciton absorption peak of 455 nm or 503 nm, CsPbI3 with a first exciton absorption peak of 640 nm, and CsPbBr2Cl with a first exciton absorption peak of 480 nm.

3. The method according to claim 1, characterized in that, When the wavelength is between 400 nm and the cutoff wavelength of lead halide perovskite quantum dots, coumarin-3-carboxylic acid is anchored on the surface of lead halide perovskite quantum dots to achieve quenching of quantum dot luminescence. When the mixed system is re-excited by ultraviolet light with wavelengths in the range of 300-375 nm, coumarin-3-carboxylic acid desorbs from the surface of lead halide perovskite quantum dots to restore the luminescence of the quantum dots.

4. The method according to claim 1, characterized in that, The dispersion solvent used in the coumarin-3-carboxylic acid solution and the lead halide perovskite quantum dot stock solution is selected from one or more of n-hexane, toluene, and n-heptane.

5. The method according to claim 1, characterized in that, The dispersion solvent used in the coumarin-3-carboxylic acid solution and the lead halide perovskite quantum dot stock solution is selected from toluene.

6. The method according to claim 1, characterized in that, The concentration of the lead halide perovskite quantum dot stock solution used in preparing the mixed system is 0.5-5 μM.

7. The method according to claim 1, characterized in that, The concentration of the lead halide perovskite quantum dot stock solution used in preparing the mixed system is 3-5 μM.

8. The method according to claim 1, characterized in that, The concentration of the coumarin-3-carboxylic acid solution used in preparing the mixed system is 0.1-2 mM.

9. The method according to claim 1, characterized in that, The concentration of the coumarin-3-carboxylic acid solution used in preparing the mixed system is 1-2 mM.

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