Methods of making cdse nanocrystals
By employing ligand regulation and stepwise growth methods, combined with in-situ purification steps, CdSe nanocrystals of different sizes were successfully prepared, solving the problem of photoluminescence color control in existing technologies and realizing efficient nanocrystal preparation and application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-19
- Publication Date
- 2026-03-24
AI Technical Summary
Existing technologies struggle to stably prepare CdSe nanocrystals of different sizes, particularly in controlling the photoluminescence color of CdSe nanocrystals.
CdSe nanocrystals were prepared in an oleic acid (OA) and oleylamine (OLA) ligand environment by adjusting the cadmium-selenium ratio and temperature using a ligand-regulated and stepwise growth method. Combined with an in-situ purification step, the size and emission peak of the nanocrystals were controlled.
It achieves wide-range modulation of the emission peak of CdSe nanocrystals, has strong resistance to photobleaching, and has a PL QY of up to 92.94%, making it suitable for in vivo imaging multicolor labeling.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of nanocrystal preparation, specifically to a method for preparing CdSe nanocrystals of different sizes based on ligand regulation and stepwise growth. Background Technology
[0002] Over the past few decades, significant progress has been made in the synthesis chemistry of colloidal semiconductor nanocrystals (quantum dots, QDs) as an important luminescent material, especially binary II-VI semiconductors. Due to their unique photophysical properties, such as size-tunable symmetrical emission, excellent light absorption, and high photoluminescence quantum yield, colloidal semiconductor nanocrystals have become important materials in fields such as light-emitting diodes, solar cells, biomedical labeling, lasers, and single-photon sources.
[0003] CdSe nanocrystals also have wide applications in the cigarette production field. For example, by using fluorescent quantum dots as marker signals, a rapid identification system for cooking fumes has been constructed. Applying this system to the problem of locating and tracing the source of cigarette cooking fumes that sometimes occur in cigarette production can achieve remarkable results. It can not only quickly and accurately determine the location of oil leaks and potential hazards, but also simultaneously locate different types of oil at multiple locations.
[0004] However, preparing high-quality CdSe nanocrystals of different sizes is no easy task.
[0005] The photoelectric properties of colloidal semiconductor nanocrystals are mainly influenced by factors such as size, shape, crystal structure, and surface defects. These factors are primarily controlled by the type of precursor, the choice of surfactant, the molar concentration and ratio of the precursor, and the growth temperature. Because stearic acid is relatively stable, lacks double bonds, and is easily oxidized, cadmium stearate is increasingly chosen as the cadmium precursor. The solution environment of selenium powder is also crucial in the synthesis of CdSe nanocrystals using the single-injection method. Besides the choice of cadmium precursor and the solution environment of selenium powder, the ligand environment is equally important for preparing high-quality CdSe nanocrystals and controlling their size. Regarding the size of CdSe nanocrystals, preparing CdSe nanocrystals with photoluminescence colors within a specific range is quite difficult. Most methods involve epitaxially growing shells such as ZnS, CdS, or ZnSe on the CdSe surface to achieve a certain emission wavelength range for the nanocrystals.
[0006] Therefore, the purpose of this application is to study the influence and role of oleylamine and oleic acid in the growth process of CdSe nanocrystals, and to propose a method for the stable preparation of CdSe nanocrystals of different sizes by combining them with the stepwise growth method. Summary of the Invention
[0007] To overcome the above shortcomings, this invention provides a method for preparing CdSe nanocrystals. This invention, through ligand regulation and stepwise growth, successfully prepares CdSe nanocrystals of different sizes under suitable ligand environments created by OA and OLA, without strict requirements on the cadmium-selenium ratio and temperature during synthesis.
[0008] The technical solution adopted by this invention to solve its technical problem is as follows:
[0009] Methods for preparing CdSe nanocrystals, including
[0010] S1. Selenium powder 0.0473g±0.0001g was dispersed in 1-octadecene 6±0.01mL by ultrasonic dispersion to obtain Se-SUS.
[0011] The operating parameters of the ultrasonic cell disruptor are: ultrasonic time 4±1 seconds, ultrasonic interval 9±1 seconds, and ultrasonic frequency 22±1 times.
[0012] S2. 0.68±0.001g of cadmium stearate and 10±0.01mL of 1-octadecene were placed in a three-necked flask to obtain a Cd precursor mixture. The mixture was bubbled with argon for 5±0.5 minutes and then heated to 250±5℃.
[0013] S3: 1±0.01mL of Se-SUS prepared in S1 was rapidly injected into a three-necked flask at 250±5℃ and grown at 250±5℃ for 10±0.5 minutes to grow small-sized CdSe nanocrystals.
[0014] S4 uses a step-by-step growth method to prepare large-size CdSe nanocrystals;
[0015] 1±0.01 mL of oleic acid was added to the Se-SUS prepared in S1 to obtain Se-OA-SUS. 1.2±0.01 mL of Se-OA-SUS was then rapidly injected into a three-necked flask at 250±5 °C and the growth continued for 10±0.5 min.
[0016] Then, 1.4±0.01 mL of Se-OA-SUS was rapidly injected into a three-necked flask at 250±5℃ and growth continued for 10±0.5 minutes;
[0017] S5. 1±0.01mL of oleylamine was added to a three-necked flask and the reaction was continued at 260±5℃ for 10±0.5 minutes to stabilize the size of CdSe nanocrystals with poor size distribution.
[0018] S6 allows the reaction mixture to be naturally cooled to 50±5℃ for in-situ purification.
[0019] As an improvement to the above technical solution, the in-situ purification step for the CdSe nanocrystals prepared by S6 is as follows:
[0020] At 50±5℃, 0.8±0.01 mL of tributylphosphine, 1.0±0.01 mL of octylamine, 8.0±0.1 mL of n-hexane, and 16.0±0.1 mL of methanol were added to the prepared crude solution of CdSe nanocrystals and stirred for 3±0.5 minutes. After stirring was stopped, the mixture was allowed to stand until the colorless methanol layer and the 1-octadecene-n-hexane layer separated into layers. The lower methanol layer was then removed with a syringe.
[0021] The above in-situ purification process was repeated four times, with only the first and third times adding tributylphosphine and octylamine.
[0022] The beneficial effects of this invention are as follows:
[0023] The method for preparing CdSe nanocrystals based on this invention allows for a relatively wide range of control over the emission peak of CdSe nanocrystals, with an adjustable range of approximately 89 nm, by adjusting the amounts of Se-SUS, OA, and OLA, and by employing a stepwise growth method within the ligand environment created by OA and OLA. During the preparation of CdSe nanocrystals, the introduction of OA can dissolve small-sized nanocrystals, thereby promoting intraparticle maturation and enabling CdSe QDs to grow to larger sizes. OLA plays two roles in the synthesis of CdSe QDs: when the OLA concentration is low, it can promote rapid nucleation of CdSe QDs; when the OLA concentration is high, it will produce a steric hindrance effect, thereby inhibiting the nucleation and growth of CdSe QDs. In other words, introducing OA during the stepwise growth method for preparing CdSe QDs can promote rapid growth of nanocrystals, and adding OLA after the reaction can passivate the surface of CdSe QDs and promote interparticle maturation, thus stabilizing the size.
[0024] Experiments have shown that the four colors of CdSe QDs successfully prepared based on this method have good resistance to photobleaching, and the PL QY reaches up to 92.94%.
[0025] This invention can provide a reference for applications such as multicolor labeling of CdSe QDs in in vivo imaging. Attached Figure Description
[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0027] Figure 1 This is a schematic diagram of the test results for Comparative Test Example 1.
[0028] in, Figure 1 (A) Schematic diagram of absorption spectra of CdSe QDs prepared with different Se-SUS addition amounts; Figure 1 (B) Schematic diagram of emission spectra of CdSe QDs prepared with different Se-SUS addition amounts; Figure 1 (C) Schematic diagram of the first exciton absorption peak and emission peak positions of CdSeQDs prepared with different Se-SUS addition amounts; Figure 1 (D) Schematic diagram of the full width at half maximum (FWHM) and emission peak intensity of CdSeQDs prepared with different Se-SUS addition amounts;
[0029] Figure 2 This is a schematic diagram of the test results for Comparative Test Example 2;
[0030] in, Figure 2 (A) Schematic diagram of absorption spectra of CdSe QDs prepared with different amounts of OA; Figure 2 (B) Schematic diagram of emission spectra of CdSe QDs prepared with different amounts of OA; Figure 2 (C) Schematic diagram of the first exciton absorption peak and emission peak positions of CdSe QDs prepared with different amounts of OA; Figure 2 (D) Schematic diagram of the full width at half maximum (FWHM) of CdSe QDs prepared with different amounts of OA;
[0031] Figure 3 This is a schematic diagram of the test results for Comparative Test Example 3;
[0032] in, Figure 3 (A) Schematic diagram of absorption spectra of CdSe QDs prepared with different amounts of OLA; Figure 3 (B) Schematic diagram of emission spectra of CdSe QDs prepared with different amounts of OLA; Figure 3 (C) Schematic diagram of the first exciton absorption peak and emission peak positions of CdSe QDs prepared with different amounts of OLA; Figure 3 (D) Schematic diagram of the full width at half maximum (FWHM) of CdSe QDs prepared with different amounts of OLA;
[0033] Figure 4 This is a schematic diagram of the test results for Comparative Test Example 4;
[0034] in, Figure 4 (A) is a schematic diagram of the absorption and emission spectra of CdSe QDs prepared by stepwise growth only without the addition of any ligands; Figure 4 (B) is a schematic diagram of the absorption and emission spectra of CdSe QDs prepared by stepwise growth method after adding OA to Se-SUS. Figure 4 (C) is a schematic diagram of the absorption and emission spectra of CdSe QDs prepared by stepwise growth method after adding OLA to Se-SUS; Figure 4(D) is a schematic diagram of the absorption and emission spectra of CdSe QDs prepared by stepwise growth method after adding OA to Se-SUS and then using OLA for size stabilization. Detailed Implementation
[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0036] Comparative Test Example 1
[0037] Effect of selenium (Se, 99.9%) addition on the growth size of CdSe nanocrystals.
[0038] A method for preparing CdSe nanocrystals, comprising:
[0039] S1. Selenium powder 0.0473±0.0001g was dispersed in 1-octadecene 6±0.01mL by ultrasonic dispersion to obtain Se-SUS.
[0040] S2. Cadmium stearate 0.136±0.001g and 1-octadecene 6±0.01mL were placed in a three-necked flask to obtain a Cd precursor mixture. The mixture was bubbled with argon for 5±0.5 minutes and heated to 250±5℃.
[0041] S3: The Se-SUS prepared in S1 was rapidly injected into a three-necked flask at 250±5℃. The Se-SUS addition amounts for each comparative example were 0.6, 0.8, 1.0, 1.2, 1.4, and 1.6±0.01 mL, respectively. CdSe nanocrystals were grown at 250±5℃ for 10±0.5 min.
[0042] S4 allows the reaction mixture to be naturally cooled to 50±5℃ for in-situ purification.
[0043] Theoretically, the energy absorbed when an atom's ground-state electron transitions to the first excited state is represented by the first exciton absorption peak in the absorption spectrum. Changes in the positions of the first exciton absorption peak and the emission peak can reflect changes in the size of nano-quantum dots.
[0044] Depend on Figure 1(AC) shows that with the increase of Se-SUS addition, the first exciton absorption peak of the absorption spectrum and the emission peak of the emission spectrum show a significant redshift trend, indicating that the size of CdSe nanocrystals can be increased by increasing the amount of Se-SUS added. Figure 1 (D) It can be seen that as the amount of Se-SUS added increases, the emission peak intensity decreases sharply, accompanied by a significant broadening trend in the full width at half maximum (FWHM).
[0045] Based on this experimental example, when the size of CdSe-QDs is controlled by adjusting the amount of Se-SUS added, there are two problems: on the one hand, the size control effect is poor, and the adjustable emission peak range is 543~562.5nm; on the other hand, as the emission peak redshifts, the fluorescence intensity decreases and the size distribution deteriorates significantly.
[0046] Comparative Test Example 2
[0047] The effect of oleic acid (OA, 90%) addition in Se-SUS on the growth size of CdSe nanocrystals.
[0048] A method for preparing CdSe nanocrystals, comprising:
[0049] S1. Selenium powder 0.0473±0.0001g was dispersed in 1-octadecene and OA by ultrasonic dispersion to obtain Se-OA-SUS. The addition amounts of 1-octadecene and OA in each comparative example were 6±0.01mL & 0mL, 5±0.01mL & 1±0.01mL, 4±0.01mL & 2±0.01mL, 3±0.01mL & 3±0.01mL, 2±0.01mL & 4±0.01mL, and 1±0.01mL & 5±0.01mL.
[0050] S2. Cadmium stearate 0.136±0.001g and 1-octadecene 6±0.01mL were placed in a three-necked flask to obtain a Cd precursor mixture. The mixture was bubbled with argon for 5±0.5 minutes and heated to 250±5℃.
[0051] S3: 1±0.01mL of Se-OA-SUS prepared in S1 was rapidly injected into a three-necked flask at 250±5℃ and grown at 250±5℃ for 10±0.5 minutes to grow CdSe nanocrystals.
[0052] S4 allows the reaction mixture to be naturally cooled to 50±5℃ for in-situ purification.
[0053] Depend on Figure 2(AC) It can be seen that as the amount of OA added increases from 1 mL to 5 mL, the first exciton absorption peak and emission peak of CdSe nanocrystals both show a significant redshift trend, increasing from 530 nm and 548.5 nm to 586 nm and 604 nm, respectively. The redshift is most pronounced when 2 mL is added, but at the same time... Figure 2 (B) and Figure 2 (D) It can be seen that the fluorescence intensity and the full width at half maximum (FWHM) showed a significant decrease and a widening, respectively.
[0054] The redshift of the first exciton absorption and emission peaks of CdSe nanocrystals is due to the addition of OA, which can dissolve smaller CdSe QDs, promote the intraparticle maturation of Ostwald maturation of CdSe QDs, and enable CdSe nanocrystals to grow to larger sizes. Figure 2 The emission spectrum of (B) was measured by diluting the in-situ purified CdSe QDs to the same factor, and the concentration was below the concentration at which aggregation causes fluorescence quenching. Figure 2 The emission spectrum of (B) can, to some extent, roughly reflect the concentration change trend of the prepared CdSe QDs, therefore we can conclude that:
[0055] As the amount of OA added increases, small-sized CdSe nanocrystals are dissolved by OA, resulting in a decrease in the concentration of CdSe nanocrystals.
[0056] Based on this experimental example, the addition of OA acts as a "ripening agent" for the formation of CdSe QDs. During the growth of CdSe nanocrystals, OA dissolves small-sized crystals, leading to a decrease in the concentration of CdSe QDs. The dissolved monomers are used for the continued growth of CdSe nanocrystals, resulting in larger CdSe QDs. Furthermore, the redshift of the emission peak of CdSe QDs shows an S-curve trend with the amount of OA added.
[0057] Comparative Test Example 3
[0058] Effects of oleylamine (OLA, 90%) and its addition amount on the growth size of CdSe nanocrystals.
[0059] A method for preparing CdSe nanocrystals, comprising:
[0060] S1. Selenium powder 0.0473±0.0001g was dispersed in 1-octadecene and OLA by ultrasonic dispersion to obtain Se-OLA-SUS. The amounts of 1-octadecene and OLA added in each comparative example were 6±0.01mL & 0mL, 5±0.01mL & 1±0.01mL, 4±0.01mL & 2±0.01mL, 3±0.01mL & 3±0.01mL, 2±0.01mL & 4±0.01mL, and 1±0.01mL & 5±0.01mL.
[0061] S2. Cadmium stearate 0.136±0.001g and 1-octadecene 10±0.01mL were placed in a three-necked flask to obtain a Cd precursor mixture. The mixture was bubbled with argon for 5±0.5 minutes and heated to 250±5℃.
[0062] S3: 1±0.01mL of Se-OLA-SUS prepared in S1 was rapidly injected into a three-necked flask at 250±5℃ and grown at 250±5℃ for 10±0.5 minutes to grow CdSe nanocrystals.
[0063] S4 allows the reaction mixture to be naturally cooled to 50±5℃ for in-situ purification.
[0064] Figure 3 (AC) It can be seen that when the amount of OLA added is small (1 mL), the absorption peak and emission peak of the first exciton of CdSe nanocrystals both show a certain degree of blue shift, decreasing from 530 nm and 548.5 nm to 521 nm and 548 nm, respectively. When the amount of OLA added is greater than 2 mL, with the increase of OLA added, the absorption peak and emission peak of the first exciton of CdSe nanocrystals show a red shift trend, increasing from 537 nm and 560.6 nm to 561 nm and 584.4 nm, respectively.
[0065] But at the same time, by Figure 3 (B) and Figure 3 (D) It can be seen that the fluorescence intensity and full width at half maximum (FWHM) are... Figure 2 Similar trends emerged, with both showing significant decreases and widenings.
[0066] When the amount of OLA added is 1 mL, the blue shift of the first exciton absorption peak and emission peak of CdSe nanocrystals is due to the fact that OLA acts as an activator and nucleating agent in the initial nucleation stage of CdSe QDs, which enables CdSe QDs to nucleate rapidly and increases the initial nucleation concentration of CdSe QDs, resulting in a small final size even after subsequent crystal growth.
[0067] As the amount of OLA added continues to increase, the continuous redshift of the first exciton absorption peak and emission peak is due to the introduction of OLA causing a similar steric hindrance effect in the nucleation and growth of CdSe QDs. This results in a lower crystal concentration during the initial nucleation process and slower subsequent growth, with more precursors used for the slow growth of the subsequent crystals, leading to a larger final size of CdSe QDs.
[0068] Based on this experimental example, OLA has two main effects on the synthesis of CdSe QDs depending on the amount added:
[0069] When the amount of OLA added is small, it mainly promotes rapid nucleation, resulting in smaller CdSe QDs. When the amount of OLA added is large, it will produce a steric hindrance effect, reduce the nucleation and growth rate, and result in larger CdSe QDs.
[0070] Comparative Test Example 4
[0071] The above experimental examples have certain limitations in adjusting the size and luminescence performance of CdSe QDs by simply adjusting the amount of Se, OA and OLA added, and the range of adjustable emission peaks is relatively narrow.
[0072] This experimental example will prepare CdSe QDs with larger size and larger emission peak wavelength based on the stepwise growth method.
[0073] Figure 4 (A) shows the absorption and emission spectra of CdSe QDs prepared using only the stepwise growth method without the addition of any ligands. Both the absorption and emission spectra show two independent absorption peaks (575 & 606 nm) and emission peaks (585 & 625.6 nm), indicating that although the stepwise growth method significantly increased the size and redshifted the emission peak positions of the CdSe QDs, a relatively obvious self-nucleation phenomenon occurred during the growth of the CdSe QDs.
[0074] Figure 4 (B) shows the absorption and emission spectra of CdSe QDs prepared by stepwise growth after adding OA to Se-SUS, for comparison. Figure 4 (A) It can be seen that although the self-nucleation phenomenon still exists, the full width at half maximum (FWHM) has significantly broadened. Figure 4 (A) increased from 34.49 nm to 47.16 nm, but the size of CdSe QDs was improved and the emission peak position reached 643.4 nm.
[0075] Figure 4 (C) shows the absorption and emission spectra of CdSe QDs prepared by stepwise growth after adding OLA to Se-SUS. It is easy to see that the results are rather poor. Figure 4 (A) indicates that the size of CdSe QDs was not improved and the full width at half maximum (FWHM) increased significantly. Therefore, OLA is not suitable for improving the size of CdSe QDs when using the stepwise growth method to prepare CdSe QDs.
[0076] Therefore, this application preferably uses OA to promote the intraparticle maturation of CdSe QDs so that they can grow to a larger size, and then OLA is added to the reaction system to passivate and terminate the reaction.
[0077] Figure 4 (D) shows the absorption and emission spectra of CdSe QDs prepared by stepwise growth method after adding OA to Se-SUS and then using OLA for size stabilization. Figure 4 (D) emission peak is relatively Figure 4 (A) A 9nm red shift indicates that OA promotes the growth of CdSe QDs, although Figure 4 (D) emission peak is relatively Figure 4 (B) Blue shifted by 8.8 nm, but Figure 4 (D) has a full width at half maximum (FWHM) that is smaller than that of the peak. Figure 4 (B) The size decreased by 13.75 nm, indicating that the addition of OLA played a good role in passivation and size stabilization.
[0078] Example 1
[0079] Methods for preparing CdSe nanocrystals of different sizes, including
[0080] S1. Selenium powder 0.0473 g was dispersed in 6 mL of 1-octadecene by ultrasonic dispersion to obtain Se-SUS.
[0081] The operating parameters of the ultrasonic cell disruptor are: ultrasonic time 4 seconds, ultrasonic interval 9 seconds, and ultrasonic cycles 22 times.
[0082] S2 0.68 g of cadmium stearate and 10 mL of 1-octadecene were placed in a three-necked flask to obtain a Cd precursor mixture, which was bubbled with argon for 5 minutes and then heated to 250 °C.
[0083] S3: 1 mL of Se-SUS prepared in S1 was rapidly injected into a three-necked flask at 250 °C and grown at 250 °C for 10 minutes to grow small-sized CdSe nanocrystals.
[0084] S4 uses a step-by-step growth method to prepare large-size CdSe nanocrystals;
[0085] 1 mL of oleic acid was added to the Se-SUS prepared in S1 to obtain Se-OA-SUS. 1.2 mL of Se-OA-SUS was then rapidly injected into a three-necked flask at 250 °C and the growth continued for 10 minutes.
[0086] Then, 1.4 mL of Se-OA-SUS was rapidly injected into a three-necked flask at 250 °C and growth continued for 10 minutes.
[0087] S5 Add 1 mL of oleylamine to a three-necked flask and continue the reaction at 260 °C for 10 minutes to stabilize the size of CdSe nanocrystals with poor size distribution;
[0088] S6 allows the reaction mixture to cool naturally to 50°C for in-situ purification:
[0089] At 50°C, 0.8 mL of tributylphosphine, 1.0 mL of octylamine, 8.0 mL of n-hexane, and 16.0 mL of methanol were added to the prepared crude solution of CdSe nanocrystals and stirred for 3 minutes. After stirring was stopped, the mixture was allowed to stand until the colorless methanol layer and the 1-octadecene-n-hexane layer separated into layers. The lower methanol layer was then removed with a syringe.
[0090] The above in-situ purification process was repeated four times, with only the first and third times adding tributylphosphine and octylamine.
[0091] Example 2
[0092] Methods for preparing CdSe nanocrystals of different sizes, including
[0093] S1. Selenium powder 0.0472 g was dispersed in 1-octadecene 6.01 mL using ultrasonic dispersion to achieve good dispersion of selenium in 1-octadecene, thus obtaining Se-SUS;
[0094] The operating parameters of the ultrasonic cell disruptor are: ultrasonic time 5 seconds, ultrasonic interval 10 seconds, and ultrasonic cycles 23 times.
[0095] S2. 0.679 g of cadmium stearate and 10.01 mL of 1-octadecene were placed in a three-necked flask to obtain a Cd precursor mixture. The mixture was bubbled with argon for 5.5 minutes and then heated to 255 °C.
[0096] S3: 1 mL of Se-SUS prepared in S1 was rapidly injected into a three-necked flask at 250 °C and grown at 250 °C for 10 minutes to grow small-sized CdSe nanocrystals.
[0097] S4 uses a step-by-step growth method to prepare large-size CdSe nanocrystals;
[0098] 1 mL of oleic acid was added to the Se-SUS prepared in S1 to obtain Se-OA-SUS. 1.2 mL of Se-OA-SUS was then rapidly injected into a three-necked flask at 250 °C and the growth continued for 10 minutes.
[0099] Then, 1.4 mL of Se-OA-SUS was rapidly injected into a three-necked flask at 250 °C and growth continued for 10 minutes.
[0100] S5 Add 1 mL of oleylamine to a three-necked flask and continue the reaction at 255 °C for 10 minutes to stabilize the size of CdSe nanocrystals with poor size distribution;
[0101] S6 allows the reaction mixture to cool naturally to 55°C for in-situ purification:
[0102] At 55℃, 0.81 mL of tributylphosphine, 1.01 mL of octylamine, 8.1 mL of n-hexane, and 16.1 mL of methanol were added to the prepared crude solution of CdSe nanocrystals and stirred for 3.5 minutes. After stirring was stopped, the mixture was allowed to stand until the colorless methanol layer and the 1-octadecene-n-hexane layer separated into layers. The lower methanol layer was then removed with a syringe.
[0103] The above in-situ purification process was repeated four times, with only the first and third times adding tributylphosphine and octylamine.
[0104] Example 3
[0105] Methods for preparing CdSe nanocrystals of different sizes, including
[0106] S1. Selenium powder 0.0474 g was dispersed in 6 mL of 1-octadecene by ultrasonic dispersion to obtain Se-SUS.
[0107] The operating parameters of the ultrasonic cell disruptor are: ultrasonic time 5 seconds, ultrasonic interval 8 seconds, and ultrasonic cycles 21 times.
[0108] S2 0.681 g of cadmium stearate and 10 mL of 1-octadecene were placed in a three-necked flask to obtain a Cd precursor mixture, which was bubbled with argon for 5.2 minutes and heated to 252 °C.
[0109] S3: 1 mL of Se-SUS prepared in S1 was rapidly injected into a three-necked flask at 255 °C and grown at 255 °C for 10.5 min to grow small-sized CdSe nanocrystals.
[0110] S4 uses a step-by-step growth method to prepare large-size CdSe nanocrystals;
[0111] 1.01 mL of oleic acid was added to the Se-SUS prepared in S1 to obtain Se-OA-SUS. 1.21 mL of Se-OA-SUS was then rapidly injected into a three-necked flask at 255 °C and the growth continued for 10.5 minutes.
[0112] Then, 1.41 mL of Se-OA-SUS was rapidly injected into a three-necked flask at 255 °C and growth continued for 10.5 minutes;
[0113] S5 Add 1 mL of oleylamine to a three-necked flask and continue the reaction at 265 °C for 10.5 minutes to stabilize the size of CdSe nanocrystals with poor size distribution;
[0114] S6 allows the reaction mixture to cool naturally to 55°C for in-situ purification:
[0115] At 55℃, 0.8 mL of tributylphosphine, 1.0 mL of octylamine, 8.1 mL of n-hexane, and 16.1 mL of methanol were added to the prepared crude solution of CdSe nanocrystals and stirred for 3.5 minutes. After stirring was stopped, the mixture was allowed to stand until the colorless methanol layer and the 1-octadecene-n-hexane layer separated into layers. The lower methanol layer was then removed with a syringe.
[0116] The above in-situ purification process was repeated four times, with only the first and third times adding tributylphosphine and octylamine.
[0117] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing CdSe nanocrystals, characterized in that: include S1. Selenium powder 0.0473g±0.0001g was dispersed in 1-octadecene 6±0.01mL by ultrasonic dispersion to obtain Se-SUS. S2. 0.68±0.001g of cadmium stearate and 10±0.01mL of 1-octadecene were placed in a three-necked flask to obtain a Cd precursor mixture. The mixture was bubbled with argon for 5±0.5 minutes and then heated to 250±5℃. S3: 1±0.01mL of Se-SUS prepared in S1 was rapidly injected into a three-necked flask at 250±5℃ and grown at 250±5℃ for 10±0.5 minutes to grow small-sized CdSe nanocrystals. S4 uses a step-by-step growth method to prepare large-size CdSe nanocrystals; 1±0.01 mL of oleic acid was added to the Se-SUS prepared in S1 to obtain Se-OA-SUS. 1.2±0.01 mL of Se-OA-SUS was then rapidly injected into a three-necked flask at 250±5 °C and the growth continued for 10±0.5 min. Then, 1.4±0.01 mL of Se-OA-SUS was rapidly injected into a three-necked flask at 250±5℃ and growth continued for 10±0.5 minutes; S5. 1±0.01mL of oleylamine was added to a three-necked flask and the reaction was continued at 260±5℃ for 10±0.5 minutes to stabilize the size of CdSe nanocrystals with poor size distribution. S6 allows the reaction mixture to be naturally cooled to 50±5℃ for in-situ purification.
2. The method for preparing CdSe nanocrystals according to claim 1, characterized in that: The steps for in-situ purification of the CdSe nanocrystals prepared by S6 are as follows: At 50±5℃, 0.8±0.01 mL of tributylphosphine, 1.0±0.01 mL of octylamine, 8.0±0.1 mL of n-hexane, and 16.0±0.1 mL of methanol were added to the prepared crude solution of CdSe nanocrystals and stirred for 3±0.5 minutes. After stirring was stopped, the mixture was allowed to stand until the colorless methanol layer and the 1-octadecene-n-hexane layer separated into layers. The lower methanol layer was then removed. The above in-situ purification process was repeated four times, with only the first and third times adding tributylphosphine and octylamine.
3. The method for preparing CdSe nanocrystals according to claim 1, characterized in that: The ultrasonic dispersion method described in S1 uses an ultrasonic cell disruptor. The operating parameters of the ultrasonic cell disruptor are: ultrasonic time 4±1 seconds, ultrasonic interval 9±1 seconds, and ultrasonic frequency 22±1 times.