High-quantum-efficiency and high-stability cadmium selenide quantum sheet and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor material synthesis, and particularly relates to a high-quantum-efficiency and high-stability cadmium selenide quantum sheet and a preparation method thereof.The high-quantum-efficiency and high-stability cadmium selenide quantum sheet is obtained after the cadmium selenide quantum sheet is dispersed in a solvent and a Z-type ligand is added into the solvent; the cadmium selenide quantum sheet is a purified cadmium selenide quantum sheet; the Z-type ligand is cadmium caprylate; the quantum chip has the characteristic of high luminescence, the quantum efficiency of the synthesized quantum chip reaches up to 95%, and compared with the prior art, the quantum efficiency of the prepared quantum chip is higher; the quantum chip has the characteristic of long-term stability, and after the synthesized quantum chip is added into the cadmium caprylate ligand, the luminous intensity can be basically kept unchanged for several months; according to the preparation method, synthesis preparation in air can be achieved, and compared with the operation that synthesis preparation needs to be carried out under nitrogen or argon, the preparation method is simpler, and the cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor material synthesis, and in particular is a high-quantum-efficiency and high-stability cadmium selenide quantum sheet and a preparation method thereof. Background Art

[0002] II-VI ultra-thin colloidal semiconductor nanocrystals, such as two-dimensional cadmium selenide (CdSe) quantum sheets, have attracted extensive research attention in recent years due to their unique physical and optical properties due to their one-dimensional quantum confinement effect. Compared with structures such as zero-dimensional quantum dots and one-dimensional quantum rods, two-dimensional quantum sheets exhibit excellent optical properties, including discrete absorption and emission spectra, narrow and sharp fluorescence emission peaks, large absorption cross sections, strong oscillator strength, and long Auger recombination lifetime. Therefore, two-dimensional colloidal quantum sheets are regarded as a high-performance luminescent material, showing great application potential in cutting-edge fields such as light-emitting diodes (LEDs), lasers, solar concentrators, photocatalysis, sensors, self-assembled structures, and bioimaging.

[0003] In the prior art, Benoit Dubertret et al. successfully replaced the original carboxylic acid ligand on the surface of the two-dimensional quantum sheet by introducing X-type dodecanethiol ligand, resulting in a red shift of about 30nm in the absorption spectrum of the quantum sheet, but the quantum yield was reduced to 15%. Mikhail Artemyev et al. found that when X-type hexadecanethiol and hexadecylphosphonic acid ligands were introduced, the fluorescence efficiency dropped significantly. Zeger Hens and his team successfully increased the quantum efficiency of 5ML thick quantum sheets to 55% after introducing Z-type oleic acid cadmium ligands (different from oleic acid used in traditional synthesis) in the later stage of quantum sheet synthesis. In addition, they also pointed out that L-type butylamine can effectively replace Z-type cadmium carboxylate ligands, and the removal of a small amount of Z-type ligands will lead to the generation of intermediate energy levels in the band gap and significantly reduce the photoluminescence quantum yield. Sandrine Ithurria et al. achieved surface passivation of cadmium selenide quantum sheets by halide ligand exchange technology, in which the halide acts as an XL-type ligand, effectively improving the quantum efficiency. Among them, the application of bromide ligands enables the quantum efficiency to reach 70%, which is the highest value of CdSe quantum sheets currently obtained by using ligand passivation technology alone.

[0004] However, there are still some problems in the synthesis of quantum chips in the existing technology:

[0005] 1. General quantum chips need to be synthesized under nitrogen or argon conditions, which is more complicated and costly;

[0006] 2. Generally, the quantum efficiency of quantum chips that are simply passivated with ligands is only about 70%, which will limit its practical application, and the luminescence of quantum chips that are not passivated with ligands is not stable enough.

[0007] Therefore, in order to solve the above problems, a cadmium selenide quantum sheet with high quantum efficiency and high stability and a preparation method thereof are proposed. Summary of the invention

[0008] 1. Technical issues to be resolved

[0009] In view of the deficiencies in the prior art, the present invention provides a cadmium selenide quantum sheet with high quantum efficiency and high stability and a preparation method thereof, so as to solve the problems raised in the background technology.

[0010] (II) Technical solution

[0011] To achieve the above object, the present invention provides the following technical solutions: a cadmium selenide quantum sheet with high quantum efficiency and high stability and a preparation method thereof, wherein the cadmium selenide quantum sheet is dispersed in a solvent, and a Z-type ligand is added thereto to obtain a cadmium selenide quantum sheet with high quantum efficiency and high stability;

[0012] The cadmium selenide quantum flakes are purified cadmium selenide quantum flakes;

[0013] The Z-type ligand is cadmium octanoate.

[0014] Preferably, the mass ratio of cadmium selenide quantum sheets to Z-type ligands is 14-17:10-13;

[0015] The solvent was dichloromethane.

[0016] Preferably, the preparation method of cadmium octoate is:

[0017] Cadmium octanoate was prepared by dissolving 0.6 mmol of cadmium oxide in 3 mL of octanoic acid at 150 degrees Celsius to obtain a clear solution.

[0018] Preferably, the preparation method of the purified cadmium selenide quantum sheet is:

[0019] S1. In an air atmosphere, cadmium oxide, tetradecanoic acid, selenium powder and 1-octadecene are added into a reaction vessel, and the mixture is reacted under stirring to obtain a mixed solution I;

[0020] S2, after the mixed solution I is cooled to room temperature, hydrated cadmium acetate is added thereto, and the reaction is continued under stirring to obtain a mixed solution II;

[0021] S3, slowly cooling the mixed solution II to room temperature, adding oleic acid thereto, shaking, and centrifuging for precipitation;

[0022] S4. Disperse the precipitate in hexane, shake, and centrifuge to precipitate; repeat 3 times to obtain purified cadmium selenide quantum chips.

[0023] Preferably, in step S1, the reaction temperature is 220° C., the stirring speed is 800 r / min, and the stirring time is 3 min.

[0024] Preferably, in step S2, the reaction temperature is 220° C., the stirring speed is 800 r / min, and the stirring time is 15 min.

[0025] Preferably, in steps S3 to S4, the shaking time is 1 min, the centrifugal speed is 5000 rpm, and the centrifugal time is 3 min.

[0026] Preferably, in steps S1 to S3, the mass ratio of cadmium oxide, myristic acid, selenium powder, 1-octadecene, hydrated cadmium acetate and oleic acid added is 13:57:8:450:30:250.

[0027] A high quantum efficiency and high stability cadmium selenide quantum sheet is prepared by using the high quantum efficiency and high stability cadmium selenide quantum sheet and the preparation method thereof as described in any one of the above items.

[0028] Preferably, the quantum efficiency of the cadmium selenide quantum chip is greater than 95%, and the luminous efficiency decreases by no more than 15% after being placed at room temperature for one week.

[0029] (III) Beneficial effects

[0030] Compared with the prior art, the present invention provides a cadmium selenide quantum sheet with high quantum efficiency and high stability and a preparation method thereof, which has the following beneficial effects:

[0031] 1. The invention can realize synthesis and preparation in the air. Compared with the general quantum chips that need to be synthesized and prepared under nitrogen or argon, the preparation method of the invention is simpler and saves costs.

[0032] 2. The invention has high luminescence characteristics, and the quantum efficiency of the synthesized quantum sheet is as high as 95%. Compared with the prior art, the quantum efficiency of the quantum sheet prepared by the present invention is higher.

[0033] 3. The invention has the characteristics of long-term stability. After the synthesized quantum sheet is added with cadmium octanoate ligand, the luminescence intensity can be maintained basically unchanged for several months. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0035] Figure 1 It is a schematic diagram of the preparation process of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Specific examples are given below.

[0038] Embodiment 1:

[0039] See also Figure 1 The present invention provides a cadmium selenide quantum sheet with high quantum efficiency and high stability and a preparation method thereof. After the cadmium selenide quantum sheet is dispersed in a solvent, a Z-type ligand is added thereto to obtain a cadmium selenide quantum sheet with high quantum efficiency and high stability;

[0040] The cadmium selenide quantum flakes are purified cadmium selenide quantum flakes;

[0041] The Z-type ligand is cadmium octanoate;

[0042] The mass ratio of cadmium selenide quantum sheets to Z-type ligands is 17:13;

[0043] The solvent is dichloromethane;

[0044] The preparation method of cadmium octanoate is:

[0045] Cadmium octanoate was prepared by dissolving 0.6 mmol of cadmium oxide in 3 mL of n-octanoic acid at 150°C to obtain a clear solution.

[0046] The preparation method of the purified cadmium selenide quantum sheet is as follows:

[0047] S1. In an air atmosphere, cadmium oxide, tetradecanoic acid, selenium powder and 1-octadecene are added into a reaction vessel, and the mixture is reacted under stirring to obtain a mixed solution I;

[0048] S2, after the mixed solution I is cooled to room temperature, hydrated cadmium acetate is added thereto, and the reaction is continued under stirring to obtain a mixed solution II;

[0049] S3, slowly cooling the mixed solution II to room temperature, adding oleic acid thereto, shaking, and centrifuging for precipitation;

[0050] S4. Disperse the precipitate in hexane, shake, and centrifuge to precipitate; repeat 3 times to obtain purified cadmium selenide quantum chips.

[0051] In the above scheme, in step S1, the reaction temperature is 220°C, the stirring speed is 800r / min, and the stirring time is 3min;

[0052] In step S2, the reaction temperature is 220°C, the stirring speed is 800r / min, and the stirring time is 15min;

[0053] In steps S3 to S4, the shaking time is 1 min, the centrifugal speed is 5000 rpm, and the centrifugal time is 3 min;

[0054] In steps S1 to S3, the added mass ratio of cadmium oxide, tetradecanoic acid, selenium powder, 1-octadecene, hydrated cadmium acetate and oleic acid is: 0.026 g: 0.114 g: 0.016 g: 3.6 g: 0.06 g: 2 g.

[0055] Through the above scheme, a high quantum efficiency and high stability cadmium selenide quantum sheet is prepared, the quantum efficiency of the cadmium selenide quantum sheet is greater than 95%, and the luminous efficiency decreases by no more than 15% after being placed under room temperature for one week.

[0056] Embodiment 2:

[0057] After dispersing the cadmium selenide quantum sheet in a solvent, a Z-type ligand is added thereto, and based on the operation process and the ratio of mass in Example 1, an A-type cadmium selenide quantum sheet is obtained;

[0058] The cadmium selenide quantum flakes are purified cadmium selenide quantum flakes;

[0059] The Z-type ligand is cadmium hexanoate.

[0060] Through the above scheme, an A-type cadmium selenide quantum sheet is prepared, and the quantum efficiency of the cadmium selenide quantum sheet is 90%.

[0061] Embodiment 3:

[0062] After dispersing the cadmium selenide quantum sheet in a solvent, a Z-type ligand is added thereto, and based on the operation process and the ratio of mass in Example 1, a B-type cadmium selenide quantum sheet is obtained;

[0063] The cadmium selenide quantum flakes are purified cadmium selenide quantum flakes;

[0064] The Z-type ligand is cadmium dodecanoate.

[0065] Through the above scheme, a B-type cadmium selenide quantum sheet is prepared, and the quantum efficiency of the cadmium selenide quantum sheet is 85%.

[0066] Embodiment 4:

[0067] After dispersing the cadmium selenide quantum sheet in a solvent, a Z-type ligand is added thereto, and based on the operation process and the ratio of mass in Example 1, a C-type cadmium selenide quantum sheet is obtained;

[0068] The cadmium selenide quantum flakes are purified cadmium selenide quantum flakes;

[0069] The Z-type ligand is cadmium oleate.

[0070] Through the above scheme, a C-type cadmium selenide quantum sheet is prepared, and the quantum efficiency of the cadmium selenide quantum sheet is 65%.

[0071] In the above scheme: the purified cadmium selenide quantum flakes are redispersed and stored in 10mL of dichloromethane [the surface ligand (oleic acid) is reduced after multiple centrifugations, and the luminescence is weakened compared to when it is just synthesized], and cadmium octanoate is added. It is found that it performs excellently in optimizing the performance of quantum flakes. The Z-type ligand can combine with uncoordinated selenium to better passivate the quantum flakes, and successfully increase the photoluminescence quantum yield to as high as 95%, achieving the characteristics of good stability and high luminescence intensity of the quantum flakes; this value represents the highest level of current purified quantum flakes. This discovery provides important guidance for the design and synthesis of high-performance optoelectronic materials, and through the comparison of multiple embodiments, it can be seen that among ligands of equal mass, the quantum flakes prepared by the preparation process involving cadmium octanoate have the highest quantum efficiency.

[0072] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A high quantum efficiency and high stability cadmium selenide quantum sheet and a preparation method thereof, characterized in that: After dispersing the cadmium selenide quantum sheet in a solvent, a Z-type ligand is added thereto to obtain a cadmium selenide quantum sheet with high quantum efficiency and high stability; The cadmium selenide quantum flakes are purified cadmium selenide quantum flakes; The Z-type ligand is cadmium octanoate.

2. A high quantum efficiency and high stability cadmium selenide quantum sheet and a preparation method thereof according to claim 1, characterized in that: The mass ratio of cadmium selenide quantum sheets to Z-type ligands is 14-17:10-13; The solvent was dichloromethane.

3. A high quantum efficiency and high stability cadmium selenide quantum sheet and a preparation method thereof according to claim 1, characterized in that: The preparation method of cadmium octanoate is: Cadmium octanoate was prepared by dissolving 0.6 mmol of cadmium oxide in 3 mL of octanoic acid at 150 degrees Celsius to obtain a clear solution.

4. A high quantum efficiency and high stability cadmium selenide quantum sheet and a preparation method thereof according to claim 1, characterized in that: The preparation method of the purified cadmium selenide quantum sheet is as follows: S1. In an air atmosphere, cadmium oxide, tetradecanoic acid, selenium powder and 1-octadecene are added into a reaction vessel, and the mixture is reacted under stirring to obtain a mixed solution I; S2, after the mixed solution I is cooled to room temperature, hydrated cadmium acetate is added thereto, and the reaction is continued under stirring to obtain a mixed solution II; S3, slowly cooling the mixed solution II to room temperature, adding oleic acid thereto, shaking, and centrifuging for precipitation; S4. Disperse the precipitate in hexane, shake, and centrifuge to precipitate; repeat 3 times to obtain purified cadmium selenide quantum chips.

5. A high quantum efficiency and high stability cadmium selenide quantum sheet and a preparation method thereof according to claim 4, characterized in that: In step S1, the reaction temperature is 220°C, the stirring speed is 800r / min, and the stirring time is 3min.

6. A high quantum efficiency and high stability cadmium selenide quantum sheet and a preparation method thereof according to claim 4, characterized in that: In step S2, the reaction temperature is 220°C, the stirring speed is 800r / min, and the stirring time is 15min.

7. A high quantum efficiency and high stability cadmium selenide quantum sheet and a preparation method thereof according to claim 4, characterized in that: In steps S3 to S4, the shaking time is 1 min, the centrifugal speed is 5000 rpm, and the centrifugal time is 3 min.

8. The high quantum efficiency and high stability cadmium selenide quantum sheet and preparation method thereof according to claim 4, characterized in that: In steps S1 to S3, the mass ratio of cadmium oxide, tetradecanoic acid, selenium powder, 1-octadecene, hydrated cadmium acetate and oleic acid added is 13:57:8:450:30:

250.

9. A high quantum efficiency and high stability cadmium selenide quantum chip, characterized in that: The cadmium selenide quantum sheet with high quantum efficiency and high stability and the preparation method thereof are used as described in any one of claims 1 to 8.

10. The high quantum efficiency and high stability cadmium selenide quantum chip according to claim 9, characterized in that: The quantum efficiency of the cadmium selenide quantum chip is greater than 95%, and the luminous efficiency decreases by no more than 15% after being placed under room temperature for one week.

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