Chiral lead sulfide quantum dot and preparation method thereof

Abstract

The invention provides a chiral lead sulfide quantum dot and a preparation method thereof.The preparation method of the chiral lead sulfide quantum dot comprises the following steps that S1, a lead precursor solution is provided, and a lead precursor comprises at least one of chiral CsPbBr3 quantum dots and (R-MBA) PbBr3; s2, dissolving sulfur in the organic amine ligand to obtain a sulfur precursor; s3, mixing the lead precursor solution with the sulfur precursor, and stirring and reacting at room temperature to obtain a crude solution; s4, the crude solution is purified, centrifuged and dried, and the chiral lead sulfide quantum dots are obtained. The chiral lead sulfide quantum dot can be rapidly synthesized at room temperature in an air environment, the conditions are mild, the efficiency is high, the cost is low, and the chiral lead sulfide quantum dot is good in dispersity and stable in property.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a chiral lead sulfide quantum dot and its preparation method. Background Technology

[0002] Circularly polarized nanomaterials, as a core component of future displays, have shown great application potential in fields such as encrypted information transmission, 3D imaging, and chiral visualization sensing. Among them, circularly polarized inorganic quantum dots have attracted attention in various fields due to their unique photoluminescence properties, chirality, and circularly polarized emission characteristics. Currently, research on circularly polarized materials mainly focuses on the visible light range, with limited reports on near-infrared (650-1500 nm) circularly polarized luminescent materials. However, near-infrared materials with circularly polarized signals exhibit higher application value in certain specific scenarios. For example, their strong penetrating power has better applications in biomedical diagnosis and treatment that requires precise control of light polarization; their rich information storage capacity holds promise for applications in advanced anti-counterfeiting.

[0003] Perovskite materials are the most widely studied and mature, but due to their limited bandgap, their absorption range is limited to the visible light region, making them unsuitable for design in the near-infrared and short-wave infrared regions. However, lead sulfide (PbS) quantum dots, due to their large absorption range, can cover the short-wave infrared region, thus showing better development prospects in the near-infrared region.

[0004] Lead sulfide colloidal quantum dot materials are generally synthesized using a high-temperature hot-injection method. The classic hot-injection method uses lead oxide (PbO) as the lead source and hexamethyldisilazane ((TMS)₂S) as the sulfur source. However, this sulfur source has strong biotoxicity and is expensive. A more novel cation exchange method uses zinc sulfide (ZnS) nanorods as the sulfur source and lead halide (PbX₂) as the lead source, which can obtain higher quality lead sulfide quantum dots. However, this method has a complex synthesis process, which is not conducive to industrial production. Currently, for circular polarization detection materials, a post-synthesis modification process is generally used. This involves introducing chiral ligands in an alkaline environment, utilizing the chiral ligands to compete for and replace the surface of oil-phase quantum dots to obtain water-dispersible chiral quantum dot materials. This method easily leads to a sharp drop in quantum dot fluorescence intensity, poor material stability, and there are few reports on chiral quantum dot materials in the near-infrared region. Summary of the Invention

[0005] In view of this, the present invention provides a chiral lead sulfide quantum dot and its preparation method, which can be rapidly synthesized at room temperature and in air, under mild, efficient and low-cost conditions, and the chiral lead sulfide quantum dots have good dispersibility and stable properties.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing chiral lead sulfide quantum dots, comprising the following steps: S1. Provide a lead precursor solution, wherein the lead precursor comprises at least one of chiral CsPbBr3 quantum dots and (R-MBA)PbBr3; S2. Sulfur is dissolved in an organic amine ligand to obtain a sulfur precursor; S3. The lead precursor solution and the sulfur precursor are mixed and stirred at room temperature to obtain a crude solution; S4. The crude solution is purified, centrifuged, and dried to obtain chiral lead sulfide quantum dots.

[0007] It should be noted that, in step S1, the chiral CsPbBr3 quantum dots can be CsPbBr3 quantum dots modified with chiral ligands; in step S2, the operation of dissolving sulfur in the organic amine ligand can be that sulfur powder is added to the organic amine ligand, heated and stirred until the sulfur powder dissolves; in step S3, the operation of mixing the lead precursor solution with the sulfur precursor can be that the sulfur precursor is added to the lead precursor solution under stirring conditions; in step S3, the stirring reaction can be carried out under air conditions at room temperature of 20 °C to 25 °C; in step S4, the solvent used for purification includes ethyl acetate.

[0008] Preferably, in step S1, the lead precursor is a chiral CsPbBr3 quantum dot, and the preparation method of the chiral CsPbBr3 quantum dot solution includes the following steps: S111. Dissolve CsPbBr3 quantum dots in a first organic solvent to obtain a CsPbBr3 quantum dot solution; S112. Dissolve R-methylbenzylamine bromide ((R-MBA)Br) in a second organic solvent, sonicate, and centrifuge to obtain an R-methylbenzylamine bromide solution; S113. Mix the CsPbBr3 quantum dot solution with the R-methylbenzylamine bromide solution, sonicate, and centrifuge to obtain a chiral CsPbBr3 quantum dot solution.

[0009] Preferably, in step S111, the CsPbBr3 quantum dots are prepared by a hot-injection method; and / or, In step S111, the first organic solvent includes octane.

[0010] Preferably, in step S112, the second organic solvent includes dimethylformamide (DMF), toluene, and oleic acid (OA); and / or, In step S113, the concentration of the chiral CsPbBr3 quantum dot solution is 0.8 mol / L to 1.2 mol / L.

[0011] Preferably, the lead precursor is (R-MBA)PbBr3, and the preparation method of the (R-MBA)PbBr3 solution includes the following steps: S121. R-methylbenzylamine bromide ((R-MBA)Br) and PbBr2 are dissolved in a third organic solvent to obtain a (R-MBA)PbBr3 solution.

[0012] Preferably, in step S121, the third organic solvent comprises dimethylformamide (DMF); and / or, In step S121, the concentration of the (R-MBA)PbBr3 solution is 0.2 mol / L to 0.4 mol / L.

[0013] Preferably, in step S2, the organic amine ligand includes at least one of oleylamine (OLA) and R-methylbenzylamine (R-MBA).

[0014] Preferably, in step S3, the stirring speed is 300 rpm to 500 rpm and the time is 8 min to 12 min.

[0015] Preferably, in step S3, the molar ratio of the lead precursor to sulfur is (1~1.5):1.

[0016] Secondly, the present invention provides a chiral lead sulfide quantum dot prepared by the aforementioned preparation method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, chiral CsPbBr3 quantum dots or (R-MBA)PbBr3 are used as lead precursors, and sulfur is dissolved in organic amine ligands as sulfur precursors. By stirring the reaction under room temperature and air conditions, chiral lead sulfide (R / S-PbS) quantum dots are rapidly generated. The chiral lead sulfide quantum dots obtained have good dispersibility and high stability, and can be used as circular polarization detection materials in the near-infrared region.

[0018] (2) In this invention, CsPbBr3 quantum dots (chiral CsPbBr3 quantum dots) that are bound to chiral ligands ((R-MBA)Br) or (R-MBA)PbBr3 with a similar structure formed in situ are used as lead precursors. This ensures that the lead source itself has a chiral environment, laying a chemical foundation for the efficient and direct transfer of chirality from molecular precursors to inorganic nanocrystal nuclei. The two precursors are rapidly mixed and reacted at room temperature. Through an "in-situ transformation" or "topological chemical transformation" mechanism, the chiral organic ligand network or chiral environment in the precursor is partially preserved or the asymmetric growth of lead sulfide lattice is guided, thereby efficiently converting molecular chirality into the inherent chirality of nanocrystals.

[0019] (3) In this invention, the synthesis conditions are mild, efficient and low cost; room temperature reaction can greatly reduce energy consumption, simplify equipment requirements and avoid ligand decomposition or chiral racemization problems that may be caused by high temperature; air environment reaction can get rid of dependence on inert atmosphere (such as glove box), significantly reduce operation complexity, equipment cost and process threshold, making the synthesis more universal and scalable; the reaction is fast, which is conducive to the formation of quantum dots with uniform size and few defects, and greatly improves the synthesis efficiency; in addition, the precursor is clear and the conditions are simple, which is conducive to achieving high reproducibility of the synthesis process and consistency of product performance.

[0020] (4) The chiral CsPbBr3 quantum dots prepared by this invention have high-quality chiral optical activity and can exhibit significant circular dichroism signals and / or circularly polarized emission in the near-infrared band (derived from the narrow bandgap characteristics of PbS). Attached Figure Description

[0021] Figure 1 The CD signal data are obtained from chiral lead sulfide quantum dots prepared in Examples 1-4 of this invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0023] Example 1 This embodiment provides a method for preparing chiral lead sulfide quantum dots, including the following steps: A. Preparation of CsPbBr3 quantum dots: Add 0.814 g of Cs2CO3, 40 mL of octadecene (ODE) and 10 mL of oleic acid (OA) to a 250 mL round-bottom three-necked flask. Alternately purge and purge the flask under vacuum and nitrogen atmosphere more than three times. Then raise the temperature to 150 °C until all Cs2CO3 is completely dissolved. After that, lower the temperature to 100 °C and purge for 2 h to remove water and oxygen. When the solution becomes transparent and clear, it means that the Cs source has been successfully prepared. Then store it at 80 °C in a nitrogen atmosphere for later use. 0.276 g PbBr2, 20 mL octadecene (ODE), 3 mL oleic acid (OA), and 3 mL oleylamine (OLA) were added to a flask. The flask was first purged with nitrogen three times at room temperature to thoroughly remove oxygen. Then, under vacuum, the flask was heated to 100 °C. After reaching the specified temperature, the flask was purged under vacuum for 3 h. Then, the flask was transferred to a nitrogen atmosphere and the temperature was set to 180 °C. Once the temperature was reached, 2 mL of the prepared Cs source was rapidly injected into the flask using a syringe. After reacting for 5 s, the heating device was immediately removed, and the flask was placed in ice water for water bath quenching. After cooling to room temperature, the crude solution was removed, and ethyl acetate (crude solution: ethyl acetate = 1:3, volume ratio) was added. The flask was centrifuged at 8000 rpm for 3 min, the supernatant was removed, and 10 mL of n-hexane was added to disperse the precipitate. The precipitate was collected after centrifugation with the same parameters, dried, weighed, and stored in a glove box.

[0024] B. Preparation of sulfur precursor: Weigh 0.32 g of sublimed sulfur powder, add 10 mL of oleylamine (OLA), and stir at 1000 rpm and 60 °C for 3 h until the sulfur powder is completely dissolved to obtain oleylamine sulfur (S-OLA, 1 mmol / mL). C. Preparation of lead precursor solution: Dissolve the CsPbBr3 quantum dots prepared in step A in octane to prepare a 10 mg / mL CsPbBr3 quantum dot solution; dissolve 1464 mg (7.2 mmol) R-methylbenzylamine bromide ((R-MBA)Br) in a 9 mL solution containing 3 mL DMF, 3 mL toluene and 3 mL OA, sonicate for 1 min, and centrifuge at 4000 rpm for 4 min to obtain a clear solution; add the clear solution to 9 mL of the 10 mg / mL CsPbBr3 quantum dot solution, sonicate for 1 min, and centrifuge at 4000 rpm for 4 min, and take the supernatant to obtain the chiral ligand-modified CsPbBr3 quantum dot solution.

[0025] D. Synthesis of chiral lead sulfide quantum dots: Take 8 mL of the chiral ligand-modified CsPbBr3 quantum dot solution prepared in step C and place it in a beaker. Then, at room temperature and 400 rpm, add 1 mL of oleylamine sulfide (S-OLA) prepared in step B and stir for 10 min (the green solution turns dark black). After the reaction is complete, take the crude solution and purify it with ethyl acetate (crude solution: ethyl acetate = 1:3, volume ratio). Centrifuge at 8000 rpm for 3 min, discard the supernatant, dry the precipitate, and obtain chiral lead sulfide quantum dots. Dissolve the chiral lead sulfide quantum dots in 2 mL of deionized water and store at 4 °C for later use.

[0026] Example 2 This embodiment provides a method for preparing chiral lead sulfide quantum dots, including the following steps: A. Preparation of CsPbBr3 quantum dots: Add 0.814 g Cs2CO3, 40 mL octadecene (ODE), and 10 mL oleic acid (OA) to a 250 mL round-bottom three-necked flask. Alternately purge and purge the flask under vacuum and nitrogen atmosphere more than three times. Then raise the temperature to 150 °C until all Cs2CO3 is completely dissolved. After that, lower the temperature to 100 °C and purge for 2 h to remove water and oxygen. When the solution becomes transparent and clear, it means that the Cs source has been successfully prepared. Then store it at 80 °C in a nitrogen atmosphere for later use. 0.276 g PbBr2, 20 mL octadecene (ODE), 3 mL oleic acid (OA), and 3 mL oleylamine (OLA) were added to a flask. The flask was first purged with nitrogen at room temperature three times to thoroughly remove oxygen. Then, under vacuum, the flask was heated to 100 °C and purged for 3 h. The flask was then transferred to a nitrogen atmosphere and heated to 180 °C. Once the temperature was reached, 2 mL of the prepared Cs source was rapidly injected into the flask using a syringe. After reacting for 5 s, the heating device was immediately removed, and the flask was placed in ice water for water bath quenching. After cooling to room temperature, the crude solution was removed, and ethyl acetate (crude solution: ethyl acetate = 1:3, volume ratio) was added. The mixture was centrifuged at 8000 rpm for 3 min, the supernatant was removed, and 10 mL of n-hexane was added to disperse the precipitate. The mixture was centrifuged again using the same parameters, the precipitate was collected, dried, weighed, and stored in a glove box.

[0027] B. Preparation of sulfur precursor: Weigh 0.32 g of sublimed sulfur powder, add 10 mL of R-methylbenzylamine (R-MBA), and stir at 1000 rpm and 60 °C for 3 h until the sulfur powder is completely dissolved to obtain R-methylbenzylamine sulfur (SR-MBA, 1 mmol / mL). C. Preparation of lead precursor solution: Take the CsPbBr3 quantum dots prepared in step A, dissolve them in octane to prepare a 10 mg / mL CsPbBr3 quantum dot solution; dissolve 1464 mg (7.2 mmol) R-methylbenzylamine bromide ((R-MBA)Br) in a 9 mL solution containing 3 mL DMF, 3 mL toluene and 3 mL OA, sonicate for 1 min, centrifuge at 4000 rpm for 4 min to obtain a clear solution; add the clear solution to 9 mL of the 10 mg / mL CsPbBr3 quantum dot solution, sonicate for 1 min, centrifuge at 4000 rpm for 4 min, take the supernatant to obtain the chiral ligand modified CsPbBr3 quantum dot solution.

[0028] D. Synthesis of chiral lead sulfide quantum dots: Take 8 mL of the chiral ligand-modified CsPbBr3 quantum dot solution prepared in step C and place it in a beaker. Then, at room temperature and 400 rpm, add 1 mL of R-methylbenzylamine sulfide (SR-MBA) prepared in step B and stir for 10 min (the green solution turns dark black). After the reaction is complete, take the crude solution and purify it with ethyl acetate (crude solution: ethyl acetate = 1:3, volume ratio). Centrifuge at 8000 rpm for 3 min, discard the supernatant, dry the precipitate, and obtain chiral lead sulfide quantum dots. Dissolve the chiral lead sulfide quantum dots in 2 mL of deionized water and store at 4 ℃ for later use.

[0029] Example 3 This embodiment provides a method for preparing chiral lead sulfide quantum dots, including the following steps: A. Preparation of lead precursor solution: Dissolve R-methylbenzylamine bromide ((R-MBA)Br) and PbBr2 in DMF in an equimolar ratio to obtain (R-MBA)PbBr3 solution, with the concentration controlled at 0.3 mol / L.

[0030] B. Preparation of sulfur precursor: Weigh 0.32 g of sublimed sulfur powder, add 10 mL of oleylamine (OLA), and stir at 1000 rpm and 60 °C for 3 h until the sulfur powder is completely dissolved to obtain oleylamine sulfur (S-OLA, 1 mmol / ml).

[0031] C. Synthesis of chiral lead sulfide quantum dots: Take 8 mL of the (R-MBA)PbBr3 solution prepared in step A and place it in a beaker. Then, at room temperature and 400 rpm, add 1 mL of oleylamine sulfide (S-OLA) prepared in step B and stir for 10 min (the green solution turns dark black). After the reaction is complete, take the crude solution and purify it with ethyl acetate (crude solution: ethyl acetate = 1:3, volume ratio). Centrifuge at 8000 rpm for 3 min, discard the supernatant, dry the precipitate, and obtain chiral lead sulfide quantum dots. Dissolve the chiral lead sulfide quantum dots in 2 mL of deionized water and store at 4 ℃ for later use.

[0032] Example 4 This embodiment provides a method for preparing chiral lead sulfide quantum dots, including the following steps: A. Preparation of lead precursor solution: Dissolve equimolar amounts of R-methylbenzylamine ((R-MBA)Br) and PbBr2 in DMF to obtain (R-MBA)PbBr3 solution, with the concentration controlled at 0.3 mol / L.

[0033] B. Preparation of sulfur precursor: Weigh 0.32 g of sublimed sulfur powder, add 10 mL of R-methylbenzylamine (R-MBA), and stir at 1000 rpm and 60 °C for 3 h until the sulfur powder is completely dissolved to obtain R-methylbenzylamine sulfur (SR-MBA, 1 mmol / mL). C. Synthesis of chiral lead sulfide quantum dots: Take 8 mL of the (R-MBA)PbBr3 solution prepared in step A and place it in a beaker. Then, at room temperature and 400 rpm, add 1 mL of R-methylbenzylamine sulfide (SR-MBA) prepared in step B and stir for 10 min (the green solution turns dark black). After the reaction is complete, take the crude solution and purify it with ethyl acetate (crude solution: ethyl acetate = 1:3, volume ratio). Centrifuge at 8000 rpm for 3 min, discard the supernatant, dry the precipitate, and obtain chiral lead sulfide quantum dots. Dissolve the chiral lead sulfide quantum dots in 2 mL of deionized water and store at 4 ℃ for later use.

[0034] CD signal data of the chiral lead sulfide quantum dots prepared in Examples 1-4 are shown below. Figure 1 ,Depend on Figure 1 It can be seen that the chiral lead sulfide quantum dots prepared in each embodiment have uniform size, absorption peaks at around 1200 nm, and stable chiral signals.

[0035] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0036] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing chiral lead sulfide quantum dots, characterized in that, Includes the following steps: S1. Provide a lead precursor solution, wherein the lead precursor comprises at least one of chiral CsPbBr3 quantum dots and (R-MBA)PbBr3; S2. Sulfur is dissolved in an organic amine ligand to obtain a sulfur precursor; S3. The lead precursor solution and the sulfur precursor are mixed and stirred at room temperature to obtain a crude solution; S4. The crude solution is purified, centrifuged, and dried to obtain chiral lead sulfide quantum dots.

2. The method for preparing chiral lead sulfide quantum dots according to claim 1, characterized in that, In step S1, the lead precursor is chiral CsPbBr3 quantum dots, and the preparation method of the chiral CsPbBr3 quantum dot solution includes the following steps: S111. Dissolve CsPbBr3 quantum dots in a first organic solvent to obtain a CsPbBr3 quantum dot solution; S112. Dissolve R-methylbenzylamine bromide in a second organic solvent, sonicate, and centrifuge to obtain an R-methylbenzylamine bromide solution; S113. Mix the CsPbBr3 quantum dot solution with the R-methylbenzylamine bromide solution, sonicate, and centrifuge to obtain a chiral CsPbBr3 quantum dot solution.

3. The method for preparing chiral lead sulfide quantum dots according to claim 2, characterized in that, In step S111, the CsPbBr3 quantum dots are prepared by thermal injection; and / or, In step S111, the first organic solvent includes octane.

4. The method for preparing chiral lead sulfide quantum dots according to claim 2, characterized in that, In step S112, the second organic solvent includes dimethylformamide, toluene, and oleic acid; and / or, In step S113, the concentration of the chiral CsPbBr3 quantum dot solution is 0.8 mol / L to 1.2 mol / L.

5. The method for preparing chiral lead sulfide quantum dots according to claim 1, characterized in that, The lead precursor is (R-MBA)PbBr3, and the preparation method of the (R-MBA)PbBr3 solution includes the following steps: S121. R-methylbenzylamine bromide and PbBr2 are dissolved in a third organic solvent to obtain (R-MBA)PbBr3 solution.

6. The method for preparing chiral lead sulfide quantum dots according to claim 5, characterized in that, In step S121, the third organic solvent includes dimethylformamide; and / or, In step S121, the concentration of the (R-MBA)PbBr3 solution is 0.2 mol / L to 0.4 mol / L.

7. The method for preparing chiral lead sulfide quantum dots according to claim 1, characterized in that, In step S2, the organic amine ligand includes at least one of oleylamine and R-methylbenzylamine.

8. The method for preparing chiral lead sulfide quantum dots according to claim 1, characterized in that, In step S3, the stirring speed is 300 rpm to 500 rpm and the time is 8 min to 12 min.

9. The method for preparing chiral lead sulfide quantum dots according to claim 1, characterized in that, In step S3, the molar ratio of the lead precursor to sulfur is (1~1.5):

1.

10. A chiral lead sulfide quantum dot prepared by the preparation method according to any one of claims 1 to 9.

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