Method for rapidly detecting bromomethane

Abstract

The invention discloses a method for rapidly detecting bromomethane, which comprises the following steps: firstly, adding a nucleophilic reagent into a bromomethane-containing base solution, and reacting under the condition of ultraviolet radiation to generate free bromide ions; and then introducing CsPbC13 quantum dots for reaction to obtain color change information of the obtained solution or right shift information of a 410-520nm fluorescence peak position of a solution system so as to realize visual detection of bromomethane. The introduced CsPbC13 quantum dots can directly react with bromide ions formed by conversion of bromomethane to induce change of color information of a fluorescent solution or a fluorescence peak position, and an intermediate response medium does not need to be additionally introduced; the corresponding mechanism of the peak position of the corresponding fluorescence emission peak and the fluorescence color is relatively stable, the sensitivity is high, and a new thought can be provided for high-sensitivity detection of bromomethane and other bromo-compounds; and the related detection method is simple, convenient to operate and suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical analysis and detection, and specifically relates to a perovskite quantum dot-mediated visual fluorescence sensing detection method for methyl bromide in tea. Background Art

[0002] Methyl bromide has a strong fumigation and penetration effect. It is often used for fumigation of goods to be stored and perishable items. It is widely used in warehouse disinfection, port quarantine and other fields. Although methyl bromide is highly volatile, residual methyl bromide will remain in food for a long time. Therefore, establishing a method for rapid, accurate and sensitive detection of methyl bromide in tea has important practical value and realistic significance.

[0003] Methyl bromide is an excellent methylating agent, which can react with organic compounds containing active hydrogen in food matrices to generate corresponding methylated products, resulting in the residue of inorganic bromide ions in food. Therefore, the content of bromide ions is sometimes used as an indicator of methyl bromide fumigation residues. Common methods for detecting methyl bromide in foods mainly include titration, photometry, headspace-gas chromatography, gas chromatography-mass spectrometry, etc. However, most of the above methods rely on large and medium-sized instruments, which are time-consuming, expensive, involve complex sample pretreatment processes, and require professional technicians. They cannot quickly, timely, and accurately monitor and evaluate the residue of methyl bromide in tea. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for detecting methyl bromide using perovskite quantum dots in view of the shortcomings of the prior art. First, a nucleophilic reagent is used to react with methyl bromide to form bromide ions, and then CsPbC13 quantum dots are introduced to induce the rightward shift of the fluorescence emission peak position of the solution and the change of the fluorescence color of the solution, thereby realizing the visual detection of methyl bromide. The method has the advantages of simple operation, fast response, high sensitivity, rich color changes, etc., and can realize the rapid, quantitative and visual identification of methyl bromide in base liquids such as tea, and is suitable for promotion and application.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for rapid detection of methyl bromide comprises the following steps: firstly, a nucleophilic reagent is added to a base liquid containing methyl bromide, and a secondary nucleophilic substitution reaction is carried out under ultraviolet irradiation to generate free bromide ions; then, CsPbC13 quantum dots are introduced to react, and color change information of the resulting solution or right shift information of the fluorescence peak position of the solution system at 410 to 520 nm is obtained, so as to realize visual detection of methyl bromide.

[0007] Furthermore, the method for rapid detection of methyl bromide specifically comprises the following steps:

[0008] 1) Add a nucleophile to the base liquid containing methyl bromide to cause the methyl bromide to undergo a secondary nucleophilic substitution reaction (S N 2 reaction) to produce free bromide ions, which are then diluted to obtain bromide ion solutions of different concentrations;

[0009] 2) Mix bromide ion solutions of different concentrations with CsPbC13 quantum dot dispersions to react, obtain the relationship between bromide ion concentration and the color change of the solution before and after the reaction or the right shift of the fluorescence emission peak position, and realize quantitative or semi-quantitative detection of methyl bromide.

[0010] In the above scheme, in step 2), the law of bromide ion concentration and solution color change before and after the reaction is obtained, and the content of methyl bromide in the solution system is judged according to the solution color change, so as to achieve semi-quantitative detection of methyl bromide.

[0011] Furthermore, as the content of methyl bromide (chloride ion) increases, the solution system obtained after the reaction turns purple-blue-green in sequence.

[0012] In the above scheme, in step 2), the relationship between the bromide ion concentration and the color change of the solution before and after the reaction or the right shift information of the fluorescence emission peak is obtained, and a linear regression equation of the right shift information of the fluorescence emission peak in the fluorescence spectrum and the methyl bromide concentration is established to achieve quantitative detection of the methyl bromide content.

[0013] In the above scheme, the fluorescence color change and the information of the rightward shift of the fluorescence emission peak are observed or measured under the condition of ultraviolet light irradiation (320-400nm).

[0014] Furthermore, the fluorescence spectrum measurement conditions are: an emission wavelength of 400-600 nm, an excitation wavelength of 350-420 nm, and a slit width of 10-15 nm.

[0015] Furthermore, the rightward shift information of the fluorescence emission peak position is the change value of the peak position before and after the reaction.

[0016] In the above scheme, the nucleophilic reagent can be selected from amine, thiol or thiourea nucleophilic reagents.

[0017] Furthermore, the nucleophilic agent can be specifically selected from oleylamine, octylamine, hexylamine, 2-mercaptoethanol, 4-mercaptobutanol, thiourea or N-methylthiourea.

[0018] In the above scheme, the base liquid containing methyl bromide can be an organic solvent such as cyclohexane, ethanol, ether or chloroform.

[0019] In the above scheme, the ultraviolet lamp wavelength used in the ultraviolet irradiation conditions is 254-365nm and the power is 15-30W.

[0020] Furthermore, the distance between the irradiation lamp source and the reaction solution ep tube is 10 to 20 cm.

[0021] Furthermore, the detection object methyl bromide of the present invention has a symmetrical molecular structure, and its C-Br bond energy is as high as 293 kJ / mol. The chemical bond is not easy to break under normal conditions, and has high chemical stability. A weak secondary nucleophilic substitution reaction can occur between methyl bromide and a nucleophilic reagent. Further introduction of ultraviolet radiation can effectively reduce the activation energy of the reaction and promote the selectivity of the reaction, so that a thorough secondary nucleophilic substitution reaction occurs between the two, effectively ensuring the conversion effect of methyl bromide and the final detection result.

[0022] In the above scheme, the molar ratio of the introduced methyl bromide to the nucleophilic reagent is 1:1-2.

[0023] In the above scheme, the reaction temperature adopted in the secondary nucleophilic substitution reaction is room temperature, and the reaction time is 20 to 60 seconds.

[0024] In the above scheme, the bromide ion concentration in the bromide ion solution obtained in step 1) is 0.1 to 120 ppb.

[0025] In the above scheme, the concentration of CsPbC13 quantum dots in the CsPbC13 quantum dot dispersion is 1-5mM.

[0026] Furthermore, the solvent used in the CsPbC13 quantum dot dispersion is cyclohexane or the like.

[0027] In the above scheme, the reaction time after adding the CsPbC13 quantum dot dispersion is 5 to 15 minutes.

[0028] In the above scheme, the volume ratio of the CsPbC13 quantum dot solution to the bromide ion solution is 1:1-4.

[0029] In the above scheme, the preparation method of CsPbC13 quantum dots is:

[0030] (1) Weighing Cs salt and OA (oleic acid) and mixing them, heating and dissolving them to prepare a Cs precursor solution; Weighing Pb salt, 1-ODE (1-octadecene), 4-chlorobutyric acid and OAm (oleylamine) and mixing them, heating and dissolving them to prepare a Pb precursor solution;

[0031] (2) The Cs precursor solution is quickly injected into the Pb precursor solution to react, and the reaction solution is quickly cooled by ice bath to obtain a crude product of Cs4PbCl6 NPs, which is then washed to obtain a white Cs4PbCl6 NPs solid;

[0032] (3) dispersing the obtained white Cs4PbCl6 NPs solid in an organic solvent, and rapidly injecting water under oscillating conditions, oscillating, standing (12 to 24 h), centrifuging, removing the bottom phase precipitate, and obtaining CsPbCl3 quantum dots.

[0033] In the above scheme, the Cs salt can be selected from Cs2CO3 or CsCl2, etc.; Pb can be selected from PbCl2, etc.

[0034] In the above scheme, the heating and dissolving temperature is 150-200° C. and the time is 1-2 hours.

[0035] Preferably, in the Cs precursor solution, the concentration of Cs ions is 0.6 to 1 mol / L.

[0036] Preferably, in the Pb precursor solution, the molar ratio of Pb salt, 4-chlorobutyric acid and OAm is 1:55-65:115-125.

[0037] Furthermore, the present invention uses ligands such as 4-chlorobutyric acid to chelate on the surface of CsPbX3 crystals at multiple ends, and anchors one end and provides the surface charge corresponding to the other end on the crystal surface; in addition, the anion and cation groups therein cannot pass Mutual neutralization of acid-base balance or external neutralization can avoid ligand dissociation caused by proton exchange reaction, improve the stability of quantum dots, promote their more stable reaction with bromide ions, and achieve stable and highly sensitive changes in the peak position and color of fluorescence emission peaks.

[0038] Furthermore, in the Pb precursor solution, the Pb ion concentration is 1-10 mM.

[0039] Preferably, the volume ratio of the Cs precursor solution to the Pb precursor solution is 1:20-25.

[0040] Furthermore, the injection time of the Cs precursor solution is 2 to 5 seconds.

[0041] In the above scheme, the organic solvent can be selected from cyclohexane or ethanol.

[0042] In the above scheme, the reaction time of step (2) is 10 to 20 seconds.

[0043] In the above scheme, in step (2), an ice bath is used to rapidly cool the solution to room temperature within 3 to 5 minutes.

[0044] In the above scheme, the shaking rate adopted in the shaking step is 1000-3000 rpm; and the shaking treatment time is 1-3 min.

[0045] Preferably, the volume ratio of cyclohexane and water added in step (3) is 10 to 15:1.

[0046] Furthermore, the water injection time is 2 to 3 seconds.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1) The present invention proposes for the first time that, for methyl bromide to be detected, ultraviolet light catalysis is used to promote nucleophilic reagents to attack C-Br in methyl bromide, and efficiently and thoroughly convert it into bromide ions; then, fluorescent probe CsPbC13 quantum dots with high chemical stability, high photostability and low toxicity are introduced to react with bromide ions in the base liquid, causing the fluorescence emission peak position of CsPbC13 quantum dots to shift to the right and the color of the fluorescent solution to change, thereby realizing efficient and convenient detection of bromine-based compounds such as methyl bromide;

[0049] 2) The CsPbC13 quantum dots introduced in the present invention react directly with the bromide ions formed by the conversion of methyl bromide (without the need to introduce an additional intermediate response medium), inducing changes in the color information of the fluorescent solution or the fluorescence peak position; and the corresponding fluorescence emission peak position and fluorescence color corresponding mechanism are relatively stable and highly sensitive, which can provide a new idea for the high-sensitivity detection of bromine-based compounds such as methyl bromide;

[0050] 3) The present invention can provide a sensitive fluorescence platform for the determination of methyl bromide in tea leaves, which has high accuracy, high sensitivity, and good linear range. Compared with existing detection methods, it avoids the defects of large equipment and long time consumption, and has no excessively high professional requirements for operators. It has wide applicability and great application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The fluorescence spectrum of CsPbC13 quantum dots prepared by the present invention;

[0052] Figure 2 This is a transmission electron microscope image of CsPbC13 quantum dots prepared by the present invention;

[0053] Figure 3 Schematic diagram of the methyl bromide detection method of the present invention.

[0054] Figure 4 This is a fluorescence spectrum diagram of the CsPbC13 quantum dots described in Example 1 of the present invention and after reacting with methyl bromide (CH3Br) and oleylamine (OA) respectively.

[0055] Figure 5The present invention is a graph showing the relationship between the degree of rightward shift of the fluorescence peak position of the CsPbC13 quantum dots described in Example 1 of the present invention after the reaction with CsPbC13 quantum dots, methyl bromide (CH3Br), and oleylamine (OA) (a) and the change in the concentration of methyl bromide; (b) a linear fitting error bar analysis graph in the concentration range of 0.333ppb-0.667ppb, in which the horizontal axis is the concentration of methyl bromide, and the vertical axis is the difference between the fluorescence peak position of the CsPbC13 quantum dots after the addition of methyl bromide and the initial fluorescence peak position of the CsPbC13 quantum dots; (c) a linear fitting error bar analysis graph in the concentration range of 0.067ppb-0.400ppb, in which the horizontal axis is the concentration of methyl bromide, and the vertical axis is the difference between the fluorescence peak position of the CsPbC13 quantum dots after the addition of methyl bromide and the initial fluorescence peak position of the CsPbC13 quantum dots; (d) a graph showing the change in fluorescence color of CsPbC13 quantum dots with methyl bromide concentration. DETAILED DESCRIPTION

[0056] The applicant will further explain the present invention in detail below in conjunction with specific embodiments so that those skilled in the art can more clearly understand the present invention. However, the following content should not be construed as limiting the scope of protection of the claims of the present invention.

[0057] The chemical reagents and solvents used in the examples were of analytical grade.

[0058] The fluorescence spectrum measurement conditions are as follows: the emission wavelength is 400-600nm, the excitation wavelength is 365nm, and the slit width is 10-15nm.

[0059] The method for preparing the CsPbC13 quantum dot dispersion comprises the following steps:

[0060] 1) 0.166 g Cs2CO3 (1.02 mmol) was weighed and mixed with 2 mL OA in a round-bottom flask, and the mixture was incubated in an oil bath at 160° C. for 1 hour to completely dissolve the solid metal salt, thereby preparing a Cs precursor solution; meanwhile, 0.014 g PbCl2 (0.05 mmol) was weighed and mixed with 10 mL 1-ODE, 300 μL CBA (3.04 mmol) and 2.0 mL OAm (6.08 mmol) in a round-bottom flask, and the mixture was incubated in an oil bath at 160° C. for 1 hour to completely dissolve the solid metal salt, thereby preparing a Pb precursor solution;

[0061] 2) 550 μL of Cs precursor solution was quickly injected into the Pb precursor solution, and the reaction was allowed to proceed for about 15 seconds. The reaction solution was quickly cooled by ice bath to obtain a crude product of Cs4PbCl6 NPs. The crude product was washed twice with 1-ODE and n-hexane (9000 rpm, 10 minutes) to obtain a pure white Cs4PbCl6 NPs solid, which was dispersed in 25 ml of cyclohexane.

[0062] 3) 200 μL of deionized water was rapidly injected under vigorous shaking (2000 rpm), and the reaction was shaken for 5 min. The reaction system was kept undisturbed for 12 h under ambient conditions, and then centrifuged at 9500 rpm for 5 min to remove the bottom phase precipitate to obtain a CsPbCl3 dispersion (with a concentration of 2 mM).

[0063] The obtained CsPbCl3 quantum dots (initial peak position at 410nm, see Figure 1 ) were characterized by transmission electron microscopy, and the results showed that the product morphology was uniformly dispersed spherical particles (see Figure 2 ).

[0064] Example 1

[0065] A method for rapidly detecting methyl bromide in tea leaves comprises the following steps:

[0066] 1) Dilute 1.0 ml of methyl bromide in 10 ml of cyclohexane, add 3 ml of oleylamine to the solution, mix well, and react for 40 seconds under an ultraviolet lamp with an excitation wavelength of 365 nm and a power of 20 W to allow the methyl bromide to undergo a secondary nucleophilic substitution reaction (S N 2 reaction) to produce free bromide ions, and then diluting the resulting bromide ion solution to a bromide ion concentration range of 0.1-120 ppb;

[0067] 2) 80ul of bromide ion solutions of different concentrations (concentrations were 0.667ppb, 0.600ppb, 0.500ppb, 0.400ppb, 0.333ppb, 0.267ppb, 0.200ppb, and 0.133ppb, respectively) were mixed with 50ul of CsPbC13 quantum dots to obtain solution II. The solution was reacted at room temperature for 5min. The color change of the solution after adding different concentrations of methyl bromide under ultraviolet light was observed by naked eye, and the relationship between the color change and the bromide ion concentration was constructed to achieve visual detection of different concentrations of methyl bromide.

[0068] The results show that, using the above detection method of the present invention, as the concentration of methyl bromide in the solution system increases, the color change pattern of the solution after the reaction is mainly purple-blue-green in sequence; the content of methyl bromide in the solution system can be judged based on the change in solution color.

[0069] Example 2

[0070] A method for quantitatively detecting methyl bromide based on CsPbC13 quantum dots specifically comprises the following steps:

[0071] 1) Dilute 1.0 ml of methyl bromide in 10 ml of cyclohexane, add 1 ml of oleylamine to the solution, mix well, and react for 60 seconds under an ultraviolet lamp with an excitation wavelength of 365 nm and a power of 20 W to allow the methyl bromide to undergo a secondary nucleophilic substitution reaction (S N 2 reaction) to produce free bromide ions, which were then diluted to obtain bromide ion solutions of different concentrations (0.667 ppb, 0.600 ppb, 0.500 ppb, 0.400 ppb, 0.333 ppb, 0.267 ppb, 0.200 ppb, 0.133 ppb);

[0072] 2) Take 80ul of bromide ion solution of different concentrations and mix it with 50ul of CsPbC13 quantum dot dispersion, react at room temperature for 10min, and then perform fluorescence spectrum measurement under ultraviolet light irradiation conditions and in the range of 400-600nm. The peak position (selected within 410-520nm) of the fluorescence emission peak of CsPbC13 quantum dots before and after the introduction of methyl bromide is measured three times in parallel, and the change value of the peak position is established with the bromide ion concentration (the concentration of methyl bromide is 0.667ppb, 0.600ppb, 0.500ppb, 0.400ppb, 0.333ppb, 0.267ppb, 0.200ppb, 0.133ppb) The linear relationship is achieved to achieve quantitative testing of the methyl bromide content.

[0073] The results show that when methyl bromide is not added, the peak position of the CsPbC13 quantum dot solution is 410nm. Simply adding methyl bromide or oleylamine does not cause the right shift of the fluorescence emission peak of CsPbC13 quantum dots. When methyl bromide reacts with oleylamine to produce free bromide ions, the fluorescence emission peak of CsPbC13 quantum dots will shift to the right. This is because the bromide ions react with the CsPbC13 quantum dots (such as Figure 4 After adding different concentrations of methyl bromide, the peak position of the fluorescence emission peak of CsPbC13 quantum dots ranges from 410 to 520 nm, and the peak position change value of CsPbC13 quantum dots increases with the increase of methyl bromide concentration ( Figure 5 (a)), in different concentration ranges (0.333ppb-0.667ppb( Figure 5 (b)) and 0.067ppb-0.400ppb( Figure 5 (c)) have linear trends, and the linear correlation coefficients between them are 0.997 and 0.992, respectively; the specific identification and quantification of methyl bromide can be achieved.

[0074] Example 3

[0075] A method for visually detecting methyl bromide based on CsPbC13 quantum dots specifically comprises the following steps:

[0076] 1) Dilute 1.0 ml of methyl bromide in 10 ml of cyclohexane, add 1 ml of oleylamine to the solution, mix well, and react for 60 seconds under an ultraviolet lamp with an excitation wavelength of 365 nm and a power of 20 W to allow the methyl bromide to undergo a secondary nucleophilic substitution reaction (S N 2 reaction) to produce free bromide ions, which were diluted to obtain bromide ion solutions of different concentrations (1 ppb, 0.667 ppb, 0.467 ppb, 0.333 ppb, 0.200 ppb, 0.067 ppb, 0.047 ppb, 0.033 ppb, 0.020 ppb, 0.007 ppb);

[0077] 2) Take 600ul of bromide ion solution of different concentrations and 375ul of CsPbC13 quantum dots and mix them in an ep tube, react at room temperature for 10 minutes, and observe the color change of the solution before and after the reaction under ultraviolet light with the naked eye, thereby preliminarily realizing the visual detection of methyl bromide of different concentrations.

[0078] The results show that the CsPbC13 quantum dot solution is purple when no methyl bromide is added. After adding different concentrations of methyl bromide, the color of the CsPbC13 quantum dot solution gradually changes from purple to blue to green ( Figure 5 (d)), wherein when the concentration of methyl bromide is lower than 0.03 ppb, the solution is purple; when the concentration of methyl bromide is between 0.03-0.2 ppb, the solution color changes from purple to blue; when the concentration of methyl bromide exceeds 0.3 ppb, the solution color changes to green. Visual semi-quantitative detection of methyl bromide can be achieved based on the rich fluorescent color changes of the solution.

[0079] Example 4

[0080] A method for rapidly detecting methyl bromide in tea leaves, wherein the obtained CsPbC13 quantum dots are applied to detect methyl bromide in a tea matrix, specifically comprising the following steps:

[0081] 1) Dilute 1.0 ml of methyl bromide in 10 ml of cyclohexane solution of tea leaves (tea leaves do not contain methyl bromide), add 3 ml of oleylamine to the solution, mix well, and react for 20 seconds under an ultraviolet lamp with an excitation wavelength of 254 nm and a power of 20 W to allow methyl bromide to undergo a secondary nucleophilic substitution reaction (S N 2 reaction) to produce free bromide ions, and further diluted to bromide ion concentrations of 0.13 ppb, 0.27 ppb, 0.33 ppb, 0.40 ppb, 0.47 ppb, and 0.67 ppb, respectively;

[0082] 2) Then it was mixed with 50ul of the obtained CsPbC13 quantum dots, reacted at room temperature for 10 minutes, and then the fluorescence spectrum was measured in the range of 400-600nm, and the peak positions of the fluorescence emission peaks of the CsPbC13 quantum dots obtained before and after the introduction of methyl bromide into the cyclohexane solution matrix of tea leaves with different concentrations were respectively measured, and the change value of the peak position was substituted into the linear equation obtained in Example 2, and the predicted value of the model for the methyl bromide concentration in the tea matrix was calculated, and its recovery rate was calculated. The results are shown in Table 1.

[0083] Table 1 Determination results of methyl bromide in tea matrix

[0084]

[0085] The results showed that the recoveries of methyl bromide at 6 different concentrations (0.13 ppb, 0.27 ppb, 0.33 ppb, 0.40 ppb, 0.47 ppb, 0.67 ppb) in tea matrix were maintained between 94% and 103% (as shown in Table 1), which can achieve specific identification and quantification of methyl bromide in tea matrix.

[0086] Comparative Example 1

[0087] A method for rapidly detecting methyl bromide in tea leaves, wherein the specific detection method is substantially the same as that in Example 1, except that CdTe quantum dots, CdS quantum dots, ZnS quantum dots, and carbon quantum dots are used to replace the CsPbC13 quantum dots described in the present invention.

[0088] The results showed that after the room temperature reaction (step 2), no color change of the solution or rightward shift of the fluorescence emission peak was observed under UV light irradiation conditions due to different concentrations of methyl bromide.

[0089] Comparative Example 2

[0090] A method for rapidly detecting methyl bromide in tea leaves, wherein the specific detection method is substantially the same as that in Example 1, the only difference is that the secondary nucleophilic substitution reaction in step 1) does not introduce ultraviolet light irradiation conditions, and the reaction time is extended to 10 to 20 minutes.

[0091] Although the above method can establish the relationship between the color change of the fluorescent solution and the bromide ion concentration, it is impossible to efficiently and completely convert methyl bromide into bromide ions, and it is impossible to effectively detect the actual methyl bromide content. The test result is significantly lower than the actual content of methyl bromide.

[0092] The above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here, so the obvious changes or modifications derived are still within the protection scope of the invention.

Claims

1. A method for rapid detection of methyl bromide, characterized in that: The method comprises the following steps: firstly, a nucleophilic reagent is added to a base liquid containing methyl bromide, and a secondary nucleophilic substitution reaction is carried out under ultraviolet irradiation to generate free bromide ions; then, CsPbC13 quantum dots are introduced to react, and color change information of the obtained solution or right shift information of the fluorescence peak position of the solution system at 410 to 520 nm is obtained, so as to realize visual detection of methyl bromide.

2. The method according to claim 1, characterized in that The right shift information of the fluorescence emission peak position is the change value of the peak position before and after the reaction.

3. The method according to claim 1, characterized in that The nucleophilic reagent is an amine, thiol or thiourea nucleophilic reagent.

4. The method according to claim 1, characterized in that: The ultraviolet lamp used in the ultraviolet irradiation conditions has a wavelength of 254 to 365 nm and a power of 15 to 30 W.

5. The method according to claim 1, characterized in that The molar ratio of the introduced methyl bromide to the nucleophile is 1:1-2.

6. The method according to claim 1, characterized in that The reaction temperature of the secondary nucleophilic substitution reaction is room temperature, and the reaction time is 20 to 60 seconds.

7. The method according to claim 1, characterized in that The preparation method of CsPbC13 quantum dots is as follows: (1) Weighing Cs salt and oleic acid, mixing them, heating and dissolving them to prepare a Cs precursor solution; weighing Pb salt, octadecene, 4-chlorobutyric acid and oleylamine, mixing them, heating and dissolving them to prepare a Pb precursor solution; (2) Rapidly injecting the Cs precursor solution into the Pb precursor solution to react, and rapidly cooling the reaction solution in an ice bath to obtain a crude product of Cs4PbCl6 NPs, which is then washed to obtain a white Cs4PbCl6 NPs solid; (3) dispersing the obtained white Cs4PbCl6 NPs solid in an organic solvent, and rapidly injecting water under oscillating conditions, oscillating, standing, centrifuging, and removing bottom phase precipitates to obtain CsPbCl3 quantum dots.

8. The method according to claim 7, characterized in that The heating and dissolving temperature is 150-200° C. and the time is 1-2 hours.

9. The method according to claim 7, characterized in that: In the Pb precursor solution, the molar ratio of Pb salt, 4-chlorobutyric acid and oleylamine is 1:55-65:115-125.

10. The method according to claim 1, characterized in that The reaction time after the introduction of CsPbC13 quantum dots is 5 to 15 minutes.

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