Preparation method of small-size stable blue light CsPbBr3 quantum dots

Abstract

The invention discloses a preparation method of a small-size stable blue-light CsPbBr3 quantum dot, which comprises the following steps: S1, sequentially adding CsCO, oleic acid and octadecene into a three-neck flask, introducing nitrogen, and reacting at 120 DEG C for 1 hour to obtain cesium oleate; s2, octadecene, PbBr2, NH4Br, oleic acid and oleylamine are sequentially added into a three-neck flask, nitrogen is introduced, the temperature is increased to 120 DEG C from the room temperature in the nitrogen atmosphere so that reactants can be dissolved, then the temperature is adjusted to 25-140 DEG C, after the temperature is stable, a certain amount of cesium oleate at the temperature of 120 DEG C is rapidly injected, after a reaction is conducted for 30-60 s, the three-neck flask is rapidly placed in an ice-water bath to be cooled for 60-120 s, the mixture is taken out of the ice-water bath, and a product is obtained; the preparation method comprises the following steps: adding a mixed solution into normal hexane, stirring, centrifuging at 3500 rpm for 2 minutes, retaining supernatant liquid, adding acetone into the supernatant liquid to obtain turbid liquid, centrifuging the turbid liquid at 3500 rpm for 2 minutes, collecting precipitates, and dispersing the precipitates in the normal hexane to obtain the small-size blue light CsPbBr3 quantum dots. The cost of raw materials is low, a synthesis device is simple, and the fluorescence stability of the obtained CsPbBr3 quantum dots is excellent.

Description

Technical Field

[0001] The present invention belongs to the field of nanotechnology, and in particular relates to a method for preparing small-sized stable blue light CsPbBr3 quantum dots. Background Art

[0002] Lead halide perovskites are considered promising optoelectronic materials due to their excellent optical and electrical properties, such as high color purity, high carrier mobility, tunable emission wavelength, and long carrier diffusion length. All-inorganic lead halide perovskite (CsPbX3, X = Cl, Br, I, Cl / Br, Br / I) quantum dots exhibit excellent optical properties and are widely used in optoelectronic devices such as photodetectors and lasers.

[0003] Blue luminescent materials are essential in many optical applications. In all-inorganic lead halide perovskites, blue light is usually achieved by mixing chlorine (Cl) and bromine (Br) elements in lead-based perovskites, such as CsPbCl x Br 3-x However, under optical or electrical excitation, these mixed Cl and Br perovskites exhibit severe, irreversible phase separation due to halide ion migration, resulting in significant spectral shifts and broadening, which has hindered their commercialization. Single halide (Cl, Br, and I) perovskites can effectively avoid this ion migration, but the intrinsic interband transitions of their bulk materials are not in the blue region. When the size of at least one dimension of CsPbBr3 approaches its exciton Bohr diameter (~7nm), the strong quantum confinement effect of low-dimensional CsPbBr3 can blue-shift the luminescence center by hundreds of millielectronvolts, which is sufficient to tune its interband green emission into the blue region. To meet this demand for blue light, researchers have devoted themselves to the study of low-dimensional CsPbBr3, including nanosheets, nanowires, and quantum dots. Nanosheets and nanowires require control of their size in specific dimensions, which is very difficult. Therefore, the resulting products are usually a mixture of various sizes and morphologies, resulting in severe spectral broadening. Quantum dots have consistent characteristics in all three dimensions, with more uniform size and narrower luminescence spectrum.

[0004] Unlike the rigid crystal structure of traditional quantum dots with covalent bonds (such as InP quantum dots), the main chemical bonds of CsPbBr3 are ionic bonds, which makes its structure soft and has low lattice formation energy. Therefore, the entire nucleation and growth process of CsPbBr3 quantum dots usually occurs on a sub-second time scale, which makes obtaining small quantum dots with a size of less than 7nm a major challenge at present. In addition, as the size decreases, the precise control of the size distribution becomes increasingly difficult, which leads to poor size uniformity, broadening of the luminescence peak, and multi-peak emission. Dong et al. synthesized CsPbBr3 quantum dots with a size of about 4 nm, and the luminescence center was at 467 nm [Dong YT, Qiao T, Kim D, et al. Precise control of quantum confinement in cesium lead halide perovskite quantum dots via thermodynamic equilibrium [J]. Nano Letters, 2018, 18 (6): 3716-3722]; Zhang et al. synthesized CsPbBr3 quantum dots with a size of ~2 nm by introducing cesium dodecylbenzenesulfonate and oleic acid, and with the assistance of oleylamine, the luminescence center was about 449 nm [Zhang HD, Lv Y, Chang YL, et al. Ultra-small-size, Highly efficient and stable CsPbBr3 quantum dots synthesized by using a cesium-dodecyl benzenesulfonic acid solution [J]. Chemical Engineering Journal, 2023, 473: 145213]. However, the small-sized blue-light CsPbBr3 quantum dots obtained by these methods are very unstable. They easily regrow, causing the quantum dot size to increase and the quantum confinement effect to disappear, resulting in rapid and drastic changes in the emission peak position and line width of the fluorescence, usually changing from blue to green within 2 days.

[0005] Therefore, there is an urgent need to overcome the problem of poor fluorescence stability in the existing preparation methods of small-sized blue light CsPbBr3 quantum dots. It is of great significance to develop a reliable method to achieve small-sized, stable fluorescence CsPbBr3 quantum dots with blue light emission (450-490nm). Summary of the Invention

[0006] The present invention aims to overcome the poor fluorescence stability of small-sized blue-emitting CsPbBr3 quantum dots in the prior art. By precisely controlling the size of the CsPbBr3 quantum dots, blue emission is achieved through the strong quantum confinement effect of the small size. Furthermore, the problem of continued growth of small-sized CsPbBr3 quantum dots, which causes their blue emission to quickly transition to green, is addressed. This method provides a method for preparing small, stable blue-emitting CsPbBr3 quantum dots. This method achieves low synthesis temperatures and excellent fluorescence stability.

[0007] The technical solution for achieving the purpose of the present invention is:

[0008] A method for preparing small-sized stable blue light-emitting CsPbBr3 quantum dots comprises the following steps:

[0009] S1: Cs2CO3, oleic acid, and octadecene were added to a three-necked flask in sequence, nitrogen was introduced, and the mixture was reacted at 120°C for 1 hour to obtain cesium oleate. Nitrogen was continued to be introduced into the cesium oleate while maintaining the temperature at 120°C for subsequent reactions.

[0010] S2: Octadecene, PbBr2, NH4Br, oleic acid, and oleylamine are added to a three-necked flask in sequence, nitrogen is introduced, and the temperature is raised from room temperature to 120°C in a nitrogen atmosphere to dissolve the reactants. The temperature is then adjusted to the desired reaction temperature. When the desired reaction temperature stabilizes, a certain amount of cesium oleate from step S1 is rapidly injected to react for 30-60 seconds to obtain a mixture. The three-necked flask containing the mixture is then quickly placed in an ice-water bath (0°C) and cooled for 60-120 seconds. The mixture is removed from the ice-water bath and centrifuged at 3500 rpm for 2 minutes using a centrifuge. The supernatant is retained, and acetone is added to the supernatant to obtain a turbid solution. The turbid solution is centrifuged at 3500 rpm for 2 minutes. The precipitate is collected and dispersed in n-hexane to obtain small-sized stable blue light CsPbBr3 quantum dots.

[0011] The reaction temperature in step S2 is 25-140°C.

[0012] The addition of NH4Br in step S2 can stabilize the fluorescence of small-sized CsPbBr3 quantum dots.

[0013] The amount of NH4Br added in step S2 combined with the reaction temperature can control the size of the CsPbBr3 quantum dots.

[0014] This technical solution has the following beneficial effects:

[0015] (1) The raw material cost is low and the synthesis equipment is simple.

[0016] (2) Small-sized CsPbBr3 quantum dots with stable blue fluorescence can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a synthesis device of an embodiment. Figure 1 In the figure, 1 is a temperature controller; 2 is a thermocouple; 3 is a syringe; 4 is a cesium oleate solution; 5 is a flask; 6 is silicone oil; 7 is a mixed solution (including octadecene, PbBr2, NH4Br, oleic acid, and oleylamine); 8 is a magnetic stirring bar; 9 is a magnetic heating water bath;

[0018] Figure 2 The experimental results of Example 1 are shown. The amount of NH4Br added satisfies the following conditions: the molar ratio of NH4Br to PbBr2 is 8:1, and the reaction temperature is 25°C. Small-sized blue CsPbBr3 quantum dots with a size of 3.65±0.24nm and a fluorescence emission peak centered at 456nm are obtained, with excellent fluorescence stability. (a) Transmission electron microscopy image, (b) Photoluminescence (fluorescence) characteristics, (c) Changes in the fluorescence center position over time, (d) Changes in the fluorescence half-peak width over time;

[0019] Figure 3 The experimental results of Example 2 are shown. The amount of NH4Br added satisfies the following conditions: the molar ratio of NH4Br to PbBr2 is 8:1, and the reaction temperature is 80°C. Small-sized blue CsPbBr3 quantum dots with a size of 4.81±0.32nm and a fluorescence emission peak centered at 471nm are obtained, with excellent fluorescence stability. (a) Transmission electron microscopy image, (b) Photoluminescence (fluorescence) characteristics, (c) Changes in the fluorescence center position over time, (d) Changes in the fluorescence half-peak width over time;

[0020] Figure 4 The experimental results of Example 3 are shown. The amount of NH4Br added satisfies the following conditions: the molar ratio of NH4Br to PbBr2 is 8:1, and the reaction temperature is 140°C. Small-sized CsPbBr3 quantum dots with a size of 6.79±0.25nm and a fluorescence emission peak centered at 492nm are obtained, with excellent fluorescence stability. (a) Transmission electron microscopy image, (b) Photoluminescence (fluorescence) characteristics, (c) Changes in the fluorescence center position over time, (d) Changes in the fluorescence half-peak width over time;

[0021] Figure 5 The experimental results of Example 4 are shown. The amount of NH4Br added satisfies the molar ratio of NH4Br to PbBr2 of 2:1, and the reaction temperature is 80°C. Small-sized CsPbBr3 quantum dots with a size of 6.44±0.27nm and a fluorescence emission peak centered at 483nm are obtained, with excellent fluorescence stability. (a) Transmission electron microscopy image, (b) Photoluminescence (fluorescence) characteristics, (c) Changes in the fluorescence center position over time, (d) Changes in the fluorescence half-peak width over time;

[0022] Figure 6These are the experimental results of Example 5. The amount of NH4Br added satisfied the molar ratio of NH4Br to PbBr2 of 2:1, and the reaction temperature was 140°C. Small CsPbBr3 quantum dots with a size of 7.45±0.14 nm and a fluorescence emission peak centered at 499 nm were obtained, demonstrating excellent fluorescence stability. (a) Transmission electron microscopy image, (b) photoluminescence (fluorescence) characteristics, (c) change in the fluorescence center position over time, and (d) change in the fluorescence half-peak width over time. DETAILED DESCRIPTION

[0023] In order to make the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0024] like Figure 1 As shown, in this example, a synthesis device is used to prepare small-sized stable blue light CsPbBr3 quantum dots, wherein the synthesis device includes: a magnetic heating water bath 9, silicone oil 6 is poured into the magnetic heating water bath 9, and then a three-necked flask 5 containing a mixed solution 7 is placed in the magnetic heating water bath 9. The temperature of the magnetic heating water bath 9 is controlled by a temperature controller 1. The three-necked flask 5 is provided with a thermocouple 2 connected to the temperature controller 1 and a syringe 3 extending into the three-necked flask 5. The syringe 3 is used to inject cesium oleate solution 4 into the three-necked flask 5. The three-necked flask 5 is also provided with a magnetic stirring bar 8 for stirring.

[0025] Example 1:

[0026] S1: Add 0.2 g of Cs2CO3, 2 mL of oleic acid, and 20 mL of octadecene into a three-necked flask in sequence, introduce nitrogen, and react at 120°C for 1 h to obtain cesium oleate. Continue to introduce nitrogen into the cesium oleate and maintain the temperature at 120°C for standby use;

[0027] S2: Octadecene (12.5 mL), PbBr2 (187 mg, 0.5 mmol), NH4Br (391.76 mg, 4 mmol), oleic acid (5 mL), and oleylamine (5 mL) were added sequentially to a three-necked flask. The molar ratio of NH4Br to PbBr2 was 8:1. Nitrogen was introduced and the temperature was raised from room temperature to 120°C under a nitrogen atmosphere to dissolve the reactants. The reaction temperature was then adjusted to 25°C. Once the temperature stabilized, 120°C cesium oleate (1 mL) was rapidly added. After reacting for 60 seconds, the three-necked flask was quickly placed in an ice-water bath and cooled for 90 seconds. The mixture was removed from the ice-water bath and centrifuged at 3500 rpm for 2 minutes, retaining the supernatant. 20 mL of acetone was added to the supernatant to obtain a turbid solution, which was centrifuged at 3500 rpm for 2 min. The precipitate was collected and dispersed in 5 mL of n-hexane to obtain small-sized blue light CsPbBr3 quantum dots with a size of 3.65±0.24 nm and a fluorescence emission peak center at 456 nm.

[0028] Figure 2 is the size of the small-sized blue light CsPbBr3 quantum dots obtained in this embodiment [ Figure 2 (a)], launch center[ Figure 2 (b)], fluorescence stability [ Figure 2 (c)-(d)] Figure 2 As shown in (a), the CsPbBr3 quantum dots prepared in this example are small cubes with a side length of 3.65±0.24nm. Figure 2 (b) The central wavelength of its blue fluorescence emission is 456 nm. Figure 2 (c) shows the stability of the blue fluorescence emission center. The fluorescence emission wavelength did not change much in the first 3 days and only red-shifted by 8 nm after 32 days. Figure 2 (d) shows the stability of the fluorescence emission peak width. The half-peak width remains almost unchanged within the first two days and changes by only 4 nm after 32 days. This figure demonstrates that the size of the CsPbBr3 quantum dots can be controlled by controlling the amount of NH4Br added and the reaction temperature. Furthermore, the addition of NH4Br leads to excellent fluorescence stability.

[0029] Example 2

[0030] S1: Add 0.2g Cs2CO3, 2mL oleic acid, and 20mL octadecene to a three-necked flask, introduce nitrogen, and react at 120°C for 1 hour to obtain cesium oleate. Continue to introduce nitrogen into the cesium oleate and maintain the temperature at 120°C for later use.

[0031] S2: Octadecene (12.5 mL), PbBr2 (187 mg, 0.5 mmol), NH4Br (391.76 mg, 4 mmol), oleic acid (5 mL), and oleylamine (5 mL) were added sequentially to a three-necked flask. The molar ratio of NH4Br to PbBr2 was 8:1. Nitrogen was introduced and the temperature was raised from room temperature to 120°C in a nitrogen atmosphere to dissolve the reactants. The reaction temperature was then adjusted to 80°C. Once the temperature stabilized, cesium oleate (1 mL) at 120°C was rapidly injected. After reacting for 60 seconds, the three-necked flask was quickly placed in an ice-water bath and cooled for 90 seconds. The mixture was removed from the ice-water bath and centrifuged at 3500 rpm for 2 minutes, retaining the supernatant. 20 mL of acetone was added to the supernatant to obtain a turbid solution, which was centrifuged at 3500 rpm for 2 min. The precipitate was collected and dispersed in 5 mL of n-hexane to obtain small-sized blue light CsPbBr3 quantum dots with a size of 4.81±0.32 nm and a fluorescence emission center at 471 nm.

[0032] Figure 3 is the size of the small-sized blue light CsPbBr3 quantum dots obtained in this embodiment [ Figure 3 (a)], Blue Light Emission Center [ Figure 3 (b)], fluorescence stability [ Figure 3 (c)-(d)] Figure 3 As shown in (a), the CsPbBr3 quantum dots prepared in this example are small cubes with a side length of 4.81±0.32nm. Figure 3 (b) shows that the central wavelength of its blue fluorescence emission is 471 nm. Compared with Example 1, the reaction temperature in step S2 was increased by 55°C, the side length of the obtained quantum dots increased by about 1.2 nm, and the fluorescence emission center was red-shifted by 15 nm. Figure 3 (c) indicates the stability of its blue fluorescence emission center, Figure 3 (d) shows the stability of its blue fluorescence emission peak width, which changes very little within 32 days. Figure 3 This shows that under the same amount of NH4Br added, increasing the reaction temperature will increase the size of CsPbBr3 quantum dots, and the addition of NH4Br makes the blue fluorescence extremely stable.

[0033] Example 3

[0034] S1: Add 0.2g Cs2CO3, 2mL oleic acid, and 20mL octadecene to a three-necked flask, introduce nitrogen, and react at 120°C for 1 hour to obtain cesium oleate. Continue to introduce nitrogen into the cesium oleate and maintain the temperature at 120°C for later use.

[0035] S2: Octadecene (12.5 mL), PbBr2 (187 mg, 0.5 mmol), NH4Br (391.76 mg, 4 mmol), oleic acid (5 mL), and oleylamine (5 mL) were added sequentially to a three-necked flask. The molar ratio of NH4Br to PbBr2 was 8:1. Nitrogen was introduced and the temperature was raised from room temperature to 120°C in a nitrogen atmosphere to dissolve the reactants. The reaction temperature was then adjusted to 140°C. Once the temperature stabilized, cesium oleate (1 mL) at 120°C was rapidly injected. After reacting for 60 seconds, the three-necked flask was quickly placed in an ice-water bath and cooled for 90 seconds. The mixture was removed from the ice-water bath and centrifuged at 3500 rpm for 2 minutes, retaining the supernatant. 20 mL of acetone was added to the supernatant to obtain a turbid solution, which was centrifuged at 3500 rpm for 2 min. The precipitate was collected and dispersed in 5 mL of n-hexane to obtain small-sized CsPbBr3 quantum dots with a size of 6.79±0.25 nm and a fluorescence emission peak center at 492 nm.

[0036] Figure 4 is the size of the small-sized CsPbBr3 quantum dots obtained in this embodiment [ Figure 4 (a)], launch center[ Figure 4 (b)], fluorescence stability [ Figure 4 (c)-(d)] Figure 4 As shown in (a), the CsPbBr3 quantum dots prepared in this example are small cubes with a side length of 6.79±0.25nm. Figure 4 (b) shows that the fluorescence emission wavelength is 492 nm. Compared with Example 2, the reaction temperature in step S2 is increased by 60°C, the side length of the obtained quantum dots increases by about 2 nm, and the fluorescence emission center is red-shifted by 21 nm. Figure 4 (c) indicates the stability of its fluorescence emission center, Figure 4 (d) shows the stability of its fluorescence emission peak width, which remains almost unchanged within 32 days. Figure 4 It is further shown that under the same amount of NH4Br added, increasing the reaction temperature will increase the size of CsPbBr3 quantum dots, and the addition of NH4Br makes its fluorescence stability excellent.

[0037] Example 4

[0038] S1: Add 0.2g Cs2CO3, 2mL oleic acid, and 20mL octadecene to a three-necked flask, introduce nitrogen, and react at 120°C for 1 hour to obtain cesium oleate. Continue to introduce nitrogen into the cesium oleate and maintain the temperature at 120°C for later use.

[0039] S2: Octadecene (12.5 mL), PbBr2 (187 mg, 0.5 mmol), NH4Br (97.94 mg, 1 mmol), oleic acid (5 mL), and oleylamine (5 mL) were added sequentially to a three-necked flask. The molar ratio of NH4Br to PbBr2 was 2:1. Nitrogen was introduced and the temperature was raised from room temperature to 120°C in a nitrogen atmosphere to dissolve the reactants. The reaction temperature was then adjusted to 80°C. Once the temperature stabilized, cesium oleate (1 mL) at 120°C was rapidly injected. After reacting for 60 seconds, the three-necked flask was quickly placed in an ice-water bath and cooled for 90 seconds. The mixture was removed from the ice-water bath and centrifuged at 3500 rpm for 2 minutes, retaining the supernatant. 20 mL of acetone was added to the supernatant to obtain a turbid solution, which was centrifuged at 3500 rpm for 2 min. The precipitate was collected and dispersed in 5 mL of n-hexane to obtain small-sized CsPbBr3 quantum dots with a size of 6.44±0.27 nm and a fluorescence emission peak center at 483 nm.

[0040] Figure 5 is the size of the small-sized CsPbBr3 quantum dots obtained in this embodiment [ Figure 5 (a)], launch center[ Figure 5 (b)], fluorescence stability [ Figure 5 (c)-(d)] Figure 5 As shown in (a), the CsPbBr3 quantum dots prepared in this example are small cubes with a side length of 6.44±0.27nm. Figure 5 (b) shows that its fluorescence emission wavelength is 483 nm. Compared with Example 1, the amount of NH4Br added in step S2 is reduced to 1 / 4, and the temperature remains unchanged. The side length of the obtained quantum dots increases by about 3 nm, and its fluorescence emission center red-shifts by 27 nm. Figure 5 (c) indicates the stability of its fluorescence emission center, Figure 5 (d) shows the stability of its fluorescence emission peak width. The fluorescence center wavelength only red-shifted by 4nm within 32 days, and the half-peak width remained almost unchanged. Figure 5 This indicates that when the reaction temperature remains unchanged and the amount of NH4Br added is reduced, the size of CsPbBr3 quantum dots will increase, and the addition of NH4Br makes their fluorescence stability extremely good.

[0041] Example 5

[0042] S1: Add 0.2g Cs2CO3, 2mL oleic acid, and 20mL octadecene to a three-necked flask, introduce nitrogen, and react at 120°C for 1 hour to obtain cesium oleate. Continue to introduce nitrogen into the cesium oleate and maintain the temperature at 120°C for later use.

[0043] S2: Octadecene (12.5 mL), PbBr2 (187 mg, 0.5 mmol), NH4Br (97.94 mg, 1 mmol), oleic acid (5 mL), and oleylamine (5 mL) were added sequentially to a three-necked flask. The molar ratio of NH4Br to PbBr2 was 2:1. Nitrogen was introduced and the temperature was raised from room temperature to 120°C in a nitrogen atmosphere to dissolve the reactants. The reaction temperature was then adjusted to 140°C. Once the temperature stabilized, cesium oleate (1 mL) at 120°C was rapidly injected. After reacting for 60 seconds, the three-necked flask was quickly placed in an ice-water bath and cooled for 90 seconds. The mixture was removed from the ice-water bath and centrifuged at 3500 rpm for 2 minutes, retaining the supernatant. 20 mL of acetone was added to the supernatant to obtain a turbid solution, which was centrifuged at 3500 rpm for 2 min. The precipitate was collected and dispersed in 5 mL of n-hexane to obtain small-sized CsPbBr3 quantum dots with a size of 7.45±0.14 nm and a fluorescence emission peak center at 499 nm.

[0044] Figure 6 is the size of the small-sized CsPbBr3 quantum dots obtained in this embodiment [ Figure 6 (a)], launch center[ Figure 6 (b)], fluorescence stability [ Figure 6 (c)-(d)] Figure 6 As shown in (a), the CsPbBr3 quantum dots prepared in this example are small cubes with a side length of 7.45±0.14nm. Figure 6 (b) shows that the fluorescence emission wavelength is 499 nm. Compared with Example 4, the reaction temperature in S2 was increased by 60°C, the side length of the obtained quantum dots increased by about 1 nm, and the fluorescence emission center was red-shifted by 16 nm. Figure 6 (c) indicates the stability of its fluorescence emission center, Figure 6 (d) shows the stability of its fluorescence emission peak width, which remains almost unchanged within 32 days. Figure 6 It is further shown that under the same amount of NH4Br added, increasing the reaction temperature will increase the size of CsPbBr3 quantum dots, and the addition of NH4Br makes their fluorescence stability excellent.

[0045] The five examples described above demonstrate that the present invention can control the size of quantum dots (3.5-7.4 nm) by adjusting the reaction temperature and the amount of NH4Br added in step S2, thereby regulating the fluorescence emission wavelength (456-499 nm). Furthermore, the addition of NH4Br results in excellent fluorescence stability. This example utilizes low-cost raw materials, simple experimental apparatus, and simple conditions. This overcomes the poor fluorescence stability of small-sized blue-emitting CsPbBr3 quantum dots obtained by existing preparation methods, providing a novel method for preparing small, stable blue-emitting CsPbBr3 quantum dots.

Claims

1. A method for preparing small-sized stable blue light-emitting CsPbBr3 quantum dots, characterized in that: The steps include: S1: Cs2CO3, oleic acid, and octadecene were added to a three-necked flask in sequence, nitrogen was introduced, and the mixture was reacted at 120 °C for 1 h to obtain cesium oleate. Nitrogen was continued to be introduced into the cesium oleate while maintaining the temperature at 120 °C for subsequent reactions. S2: Octadecene, PbBr2, NH4Br, oleic acid, and oleylamine are added to a three-necked flask in sequence, nitrogen is introduced, and the temperature is raised from room temperature to 120°C in a nitrogen atmosphere to dissolve the reactants. The temperature is then adjusted to the desired reaction temperature. When the temperature stabilizes, a certain amount of cesium oleate in step S1 is rapidly injected, and the reaction is carried out for 30-60 seconds to obtain a mixture. The three-necked flask containing the mixture is then rapidly placed in an ice-water bath and cooled for 60-120 seconds. The mixture is removed from the ice-water bath and centrifuged at 3500 rpm for 2 minutes. The supernatant is retained, and acetone is added to the supernatant to obtain a turbid solution. The turbid solution is centrifuged at 3500 rpm for 2 minutes. The precipitate is collected and dispersed in n-hexane to obtain small-sized stable blue light CsPbBr3 quantum dots.

2. The method for preparing small-sized stable blue light-emitting CsPbBr3 quantum dots according to claim 1, characterized in that: The reaction temperature in step S2 is 25-140°C.

3. The method for preparing small-sized stable blue light CsPbBr3 quantum dots according to claim 2, characterized in that: The amount of NH4Br added in step S2 combined with the reaction temperature can control the size of the CsPbBr3 quantum dots.

Images