Preparation method of PbS nanocube quantum dots

Abstract

The application discloses a preparation method of PbS nanometer cubic quantum dots, which comprises the following steps of lead precursor preparation, nucleation, continuous injection growth and reaction termination. The method realizes the preparation of highly uniform cubic PbS quantum dots in a one-step synthesis process by fine adjustment of a lead-sulfur ratio, temperature and injection speed. The prepared PbS nanometer cubic quantum dots have clean crystal faces, are suitable for theoretical and experimental research and characterization of ligand strength, and can in-situ control the size of nanometer cubic quantum dots compared with the prior art, so that the problem that the size is not adjustable in the prior art is solved. Meanwhile, the preparation method can obtain the PbS nanometer cubic quantum dots with adjustable size and small size, provides new material selection for application in the fields of photoelectric devices and the like, and lays a foundation for further research on the characteristics and performance of the PbS quantum dots.

Description

Technical Field

[0001] This invention relates to the field of compound semiconductor nanomaterial preparation technology, and more specifically, to a method for preparing cubic PbS quantum dots. Background Technology

[0002] PbS quantum dots are quasi-zero-dimensional nanomaterials with unique physicochemical properties, and can be used in infrared detection, solar cells, near-infrared lasers, etc. Currently, most PbS quantum dots used in optoelectronic devices are spherical, with complex surface crystal planes, and the underlying mechanisms for defect state analysis are unclear. By synthesizing small-sized PbS nanocubes, their clean (100) crystal planes can reduce the complexity of defect state analysis, which is beneficial for elucidating the defect mechanism.

[0003] Previous reports have mentioned the synthesis of PbS nanocubes, but existing methods have yielded PbS nanocubes with relatively large sizes, typically exceeding 10 nm or even larger. However, the strength of the quantum confinement effect is closely related to the size of the quantum dot; large-sized PbS quantum dots exhibit a weak quantum confinement effect. Therefore, synthesizing small-sized and tunable PbS nanocubes is of great significance, as smaller sizes result in stronger quantum confinement effects. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing small-sized PbS nanocube quantum dots to achieve a strong quantum confinement effect and provide clearer crystal planes for the study of defect mechanisms. Furthermore, the nanocubes prepared by this method are more likely to self-assemble into superlattices, and these synthesized PbS nanocubes can achieve a transition from nanoscale to macroscale, thus possessing broader application prospects.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing PbS nanocubic quantum dots includes the following steps:

[0007] (1) Preparation of lead precursor: Weigh PbCl2 and oleylamine into a three-necked flask and stir to mix, wherein the concentration of lead is 0.2-0.4 mol / L; then evacuate the three-necked flask under vacuum and heat the flask;

[0008] (2) Nucleation: Cool the three-necked flask in a water bath, then inject the pre-prepared zinc sulfide quantum dot solution into the three-necked flask and start timing immediately. At this time, the ZnS injection is used for nucleation.

[0009] (3) Continuous injection growth: When the zinc sulfide quantum dot solution in step (2) is injected to the preset time, the injection speed is controlled by the injection pump, and the ZnS quantum dot solution is continuously injected. The temperature and injection time are adjusted, and the injection temperature and the concentration of ZnS quantum dots are changed in stages. The injection lasts for 0.5h-1.5h. The ratio of the amount of S in ZnS to the amount of Pb in the lead precursor should exceed 1.15:1.

[0010] (4) Termination of reaction: After the reaction in step (3) is completed, the mixture is cooled in a water bath. When the temperature drops, hexane and oleic acid are injected to end the reaction. The reaction solution is divided into multiple centrifuge tubes and centrifuged. The supernatant is discarded and the lower precipitate is collected, dissolved in tetrachloroethylene, and centrifuged again. The bottom precipitate is discarded, and acetonitrile is added to precipitate the quantum dots. After drying, the PbS nanocube quantum dots are obtained.

[0011] This invention discloses a method for preparing cubic PbS quantum dots. By precisely controlling the lead-to-sulfur ratio, temperature, and injection speed, highly uniform cubic PbS quantum dots are prepared in a one-step synthesis process. The prepared cubic PbS quantum dots have clean crystal faces, making them suitable for theoretical and experimental research as well as for characterizing ligand strength. Compared with existing methods, the cubic PbS quantum dots obtained by the method of this invention have the following advantages:

[0012] 1. High dimensional uniformity: The reaction conditions are precisely adjusted during the preparation process to achieve highly uniform cubic PbS quantum dots.

[0013] 2. Clean crystal faces: The prepared PbS quantum dots have clean crystal faces, which are suitable for theoretical and experimental research as well as characterization of the strength of surface ligands.

[0014] 3. Adjustable size: Compared with existing methods, the preparation method of the present invention can control the size of nanocubes.

[0015] 4. Enhanced application prospects: The prepared cubic PbS quantum dots have broad application prospects in materials science, optoelectronics and other fields. Attached Figure Description

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be construed as limiting the scope of the invention. Furthermore, unless specifically indicated, the drawings are only schematic representations of the composition or structure of the described objects and may contain exaggerated depictions, and the drawings are not necessarily drawn to scale.

[0017] Figure 1 Absorption spectra of PbS nanocubes of different sizes;

[0018] Figure 2 X-ray diffraction pattern of PbS nanocubes;

[0019] Figure 3 TEM image of PbS nanocubes;

[0020] Figure 4 This is a TEM image of PbS nanocubes. Detailed Implementation

[0021] The following is in conjunction with the appendix Figure 1-4 The present invention will be described in detail below.

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Example 1:

[0024] This embodiment provides a method for preparing PbS nanocube quantum dots, including the following steps:

[0025] (1) Weigh 3.336g of lead chloride and measure 40ml of oleylamine. Place them in a three-necked flask, evacuate the three-necked flask, heat it to 140℃, and keep it for 30min.

[0026] (2) Cool the three-necked flask to 90°C in a water bath and maintain the temperature, then add 0.93 ml of zinc sulfide and start timing immediately;

[0027] (3) When the timer reaches 30 seconds, start injecting zinc sulfide through the injection pump and adjust the temperature, injecting in three stages;

[0028] (4) After the reaction is completed, inject n-hexane at 70°C and add oleic acid at 40°C, and wait for 5 minutes. Then, divide the reaction solution into multiple centrifuge tubes, centrifuge, discard the supernatant and collect the lower precipitate, dissolve it in tetrachloroethylene and centrifuge again, discard the bottom precipitate, add acetonitrile to precipitate the quantum dots, and dry the black solid powder obtained as the prepared PbS nanocube quantum dots.

[0029] Preferably, step (3) involves three stages of injection: injection at 90°C for 30 minutes, injection at 120°C for 50 minutes, and injection at 160°C for 70 minutes.

[0030] Preferably, in the three-stage injection process in step (3), the mass distribution ratio of ZnS in the three stages is 1:5:36, and the volume of ZnS solution used is 24 ml.

[0031] Furthermore, the properties of the obtained PbS nanocubes were characterized as follows: A quantum dot solution was taken, and its optical absorption was measured using a spectrometer. The absorption spectrum is shown below. Figure 1 As shown in -a; the diffraction pattern was tested on an X-ray diffractometer, as shown in... Figure 2 As shown; a small amount of solution is dropped onto a copper grid and imaged under a transmission electron microscope, as shown. Figure 3 As shown, the average diameter is 11.7 nm.

[0032] Example 2:

[0033] This embodiment provides a method for preparing PbS nanocube quantum dots, including the following steps:

[0034] (1) Weigh 3.336g of lead chloride and measure 40ml of oleylamine. Place them in a three-necked reaction flask, evacuate the three-necked flask, heat it to 140℃, and keep it for 30min.

[0035] (2) Cool the three-necked flask to 90°C in a water bath and maintain the temperature, then add 0.93 ml of zinc sulfide and start timing immediately.

[0036] (3) When the timer reaches 30 seconds, start injecting zinc sulfide through the injection pump and adjust the temperature, injecting in three stages;

[0037] (4) After the reaction is complete, inject n-hexane at 70°C and add oleic acid at 40°C, and wait for 5 minutes. Then, divide the reaction solution into multiple centrifuge tubes, centrifuge, discard the supernatant and collect the lower precipitate, dissolve it in tetrachloroethylene, centrifuge again, discard the bottom precipitate, add acetonitrile to precipitate the quantum dots, and dry the black solid powder obtained as the prepared PbS nanocube quantum dots.

[0038] Preferably, step (3) involves three stages of injection: injection at 90°C for 30 minutes, injection at 120°C for 50 minutes, and injection at 160°C for 50 minutes.

[0039] Preferably, in the three-stage injection process in step (3), the mass distribution ratio of ZnS in the three stages is 2:10:9; and the volume of ZnS solution used is 24 ml.

[0040] Furthermore, the properties of the obtained PbS nanocubes were characterized as follows: A quantum dot solution was taken, and its optical absorption was measured using a spectrometer. The absorption spectrum is shown below. Figure 1 As shown in -b; the diffraction pattern was tested on an X-ray diffractometer and compared with... Figure 2Similarly; a small amount of solution is dropped onto a copper grid and imaged under a transmission electron microscope, such as... Figure 4 As shown, the average diameter is 8.6 nm.

[0041] The foregoing has shown and described 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. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing PbS nanocube quantum dots, characterized in that, The method comprises the following steps: (1) Lead precursor preparation: weigh lead chloride and oleylamine and mix them in a three-necked flask, wherein the concentration of lead is 0.2-0.4 mol / L; then vacuumize the three-necked flask, and heat the flask; (2) Nucleation: water-bath cool the three-necked flask, then inject the prepared zinc sulfide quantum dot solution into the three-necked flask, and start timing immediately; at this time, the zinc sulfide injection is used for nucleation; (3) Continuous injection growth: when the zinc sulfide quantum dot solution injection in step (2) reaches the preset time, use a syringe pump to control the injection speed, continuously inject the zinc sulfide quantum dot solution, and adjust the temperature and injection time, and change the injection temperature and the concentration of the zinc sulfide quantum dot solution in stages; (4) Reaction termination: after the reaction in step (3) is completed, water-bath cool, when the temperature is reduced, inject n-hexane and oleic acid to terminate the reaction, divide the reaction liquid into multiple centrifuge tubes, centrifuge, discard the supernatant and collect the precipitate, dissolve the precipitate in tetrachloroethylene, centrifuge again, discard the precipitate, add acetonitrile to precipitate the quantum dots, and dry to obtain the prepared PbS nanocube quantum dots; In step (2), the three-necked flask is water-bath cooled to 70-90℃; In step (3), the injection is kept at 90℃ for 30 min, at 120℃ for 50 min, and at 160℃ for 70 min, respectively; In step (3), the ratio of the amount of substance of S in ZnS to the amount of substance of Pb in the lead precursor should be more than 1.15:1 during the three-stage injection process; In step (3), the amount of substance distribution ratio of ZnS in the three-stage injection process is 1:5:36 or 2:10:

9.

2. The production method according to claim 1, wherein In step (1), the flask is heated to 100-160℃ and kept for 20-60 min.

3. The production method according to claim 1, wherein In step (3), the preset time is 10-90 s.

4. The production method according to claim 1, wherein In step (4), when the temperature is reduced, n-hexane and oleic acid are injected to terminate the reaction; specifically, n-hexane is injected when the temperature is reduced to 70℃, and oleic acid is added when the temperature is reduced to 40℃.

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