PbS quantum dot material and self-coating preparation method thereof

Abstract

The invention provides a PbS quantum dot material, the PbS quantum dot is of a core-shell structure, and the core-shell structure comprises a PbS semiconductor nanocrystal as a core; the PbS semiconductor nanocrystal nucleus grows in a pore channel of the micro / mesoporous template in a confinement manner; the PbS body material shell layer freely grows on the micro / mesoporous template, and the PbS body material shell layer is a continuous lead sulfide material and does not have a quantum confinement effect; the particle size of the PbS quantum dot material is not less than 0.5 [mu] m. Dual self-coating (the micro / mesoporous template and the lead sulfide material shell layer) of the PbS quantum dots is realized through an all-solid-state high-temperature calcination method, erosion of water, oxygen and severe environment conditions is avoided, and finally the lead sulfide quantum dots with high quality, uniform size and good stability are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of PbS quantum dots, and in particular relates to a PbS quantum dot material and a self-coating preparation method thereof. Background Art

[0002] Lead sulfide (PbS) quantum dots are widely used in advanced display devices, lead sulfide quantum dot detectors and lead sulfide quantum dot solar cells due to their adjustable bandgap characteristics. Due to the wide range of light response characteristics, they have great application potential in short-wave detectors and infrared solar cells. In addition, because the lead sulfide quantum dot material is small enough, its size is smaller than the Bohr radius, which produces quantum confinement effects, multi-exciton effects, surface effects and other characteristics. With these properties, its application areas cover optoelectronic fields such as energy storage, photoelectric detection, and infrared imaging.

[0003] Although lead sulfide quantum dots have great application potential, the synthesis and preparation of lead sulfide quantum dots still face many problems that need to be overcome. Liquid phase synthesis is currently the main synthesis method for synthesizing high-quality lead sulfide quantum dots, which can be divided into hot injection method, direct synthesis method, cation exchange method, hydrothermal method (or solvent thermal method), microemulsion synthesis method, etc. However, the size and quality control of PbS quantum dots synthesized by these methods are difficult, and the stability and reproducibility are relatively low. On the other hand, the organic precursors and organic ligands used in the synthesis are not only expensive but also highly biotoxic, which is not conducive to green mass production.

[0004] The existing lead sulfide quantum dot synthesis technology cannot take into account the advantages of environmental friendliness, stable mass production, and good water and oxygen stability. The application of lead sulfide quantum dots in the field of optoelectronics has certain limitations. Therefore, it is very necessary to develop a lead sulfide quantum dot synthesis technology that has good water and oxygen stability, can be repeatedly mass-produced, has simple technology, and does not pollute the environment with organic solvents, so it needs to be improved. Summary of the invention

[0005] The purpose of the present invention is to provide a PbS quantum dot material and a self-coating preparation method thereof, and to achieve double self-coating of PbS quantum dots (micro / mesoporous template and lead sulfide body material shell) through an all-solid-state high-temperature calcination method to protect them from corrosion by water, oxygen and harsh environmental conditions, and ultimately obtain high-quality, uniform-sized and stable lead sulfide quantum dots.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A PbS quantum dot material, wherein the PbS quantum dot is a core-shell structure, and the core-shell structure comprises:

[0008] PbS semiconductor nanocrystals as cores;

[0009] A micro / mesoporous template, wherein the PbS semiconductor nanocrystal core is confined and grown in the pores of the micro / mesoporous template;

[0010] A PbS bulk material shell layer is freely grown on the micro / mesoporous template, wherein the PbS bulk material shell layer is a continuous lead sulfide material and has no quantum confinement effect;

[0011] The particle size of the PbS quantum dot material is not less than 0.5 um.

[0012] Furthermore, the micro / mesoporous template is located between the PbS semiconductor nanocrystal core and the PbS bulk material shell.

[0013] Furthermore, a plurality of discontinuous PbS semiconductor nanocrystals are distributed in the pores of the micro / mesoporous template, and the diameter of at least one of the PbS semiconductor nanocrystals is less than 15 nm. Preferably, the diameter of the PbS semiconductor nanocrystal is 2-5 nm.

[0014] Furthermore, the micro / mesoporous template serves as a growth carrier for the PbS semiconductor nanocrystals and the PbS bulk material shell layer.

[0015] Furthermore, the PbS semiconductor nanocrystals and the PbS bulk material shell are simultaneously generated inside and outside the pores of the micro / mesoporous template.

[0016] Furthermore, the particle size of the PbS quantum dot material ranges from 0.5um to 100um. It should be noted that the PbS quantum dot material in this application refers to PbS quantum dots with a core-shell structure, which includes not only PbS semiconductor nanocrystals, but also double-layer coated micro / mesoporous templates and PbS bulk material shells.

[0017] Further, the micro / mesoporous template is a microporous material and / or a mesoporous material;

[0018] The microporous material is one of microporous molecular sieve, microporous silica, microporous titanium dioxide, microporous alumina, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate or microporous transition metal nitride;

[0019] The mesoporous material is one of mesoporous molecular sieve, mesoporous silica, mesoporous titania, mesoporous alumina, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate or mesoporous transition metal nitride.

[0020] A self-coating preparation method of PbS quantum dot material comprises the following steps:

[0021] Step S1: mixing lead precursor powder and micro / mesoporous template and grinding to obtain mixture A, placing mixture A in a quartz tube and vacuum sealing the tube;

[0022] Step S2: calcining the mixture A encapsulated in the quartz tube in step S1 at a temperature higher than the melting point of the lead precursor powder, and then cooling it to room temperature;

[0023] Step S3: taking out the mixture A after calcination in step S2, mixing it with a sulfur precursor and grinding it to obtain a mixture B, placing the mixture B in a quartz tube and sealing it under vacuum;

[0024] Step S4: calcining the mixture B encapsulated in the quartz tube in step S3 within a temperature range higher than the melting point of the sulfur precursor and lower than the boiling point of the sulfur precursor; after the nucleation and growth of the PbS semiconductor nanocrystals are completed, heating to a temperature higher than the boiling point of the sulfur precursor so that the sulfur source is completely consumed inside and outside the pores of the micro / mesoporous template, and then cooling to room temperature to obtain the PbS quantum dot material.

[0025] In the above, the nucleation and growth of PbS semiconductor nanocrystals can be carried out under heat preservation conditions, so as to provide confined growth of lead sulfide quantum dots in the pores of the micro / mesoporous template and to generate lead sulfide bulk material on the surface of the micro / mesoporous template.

[0026] In the above, the calcining equipment refers to all heating equipment that can achieve controllable heating at 0-1000°C, such as a tubular furnace, a rotary furnace, a rotary kiln, a heating reactor, and the like.

[0027] In the above, the device for placing mixture A and mixture B in a quartz tube and sealing the tube in a vacuum is a quartz tube vacuum packaging device. For example, a rotating vacuum sealing quartz tube device disclosed in Chinese patent No. ZL2019213711508 is a prior art and is only briefly described here.

[0028] Further, the lead precursor powder includes one or more of lead halide, lead acetate, and lead carbonate;

[0029] The sulfur precursor includes at least one of sulfur powder and sulfide salt;

[0030] The molar ratio of the sulfur precursor to the lead precursor is at least 1:1.

[0031] In the above, the PbS quantum dot material is used in a quantum dot diffusion plate, a light-emitting device, a wavelength conversion film, a quantum dot film, a quantum dot light-emitting diode or a quantum dot masterbatch.

[0032] The beneficial effects of the present invention are mainly reflected in:

[0033] (1) The present invention proposes a method of pre-embedding a lead precursor in the pores by using the adsorption effect of a micro / mesoporous template (taking silicon oxide as an example) under vacuum conditions, and then synthesizing lead sulfide quantum dots together with a sulfur precursor. The lead precursor is uniformly attached and pre-embedded inside and outside the pores of the micro / mesoporous template under vacuum and high temperature conditions, and then the molten sulfur precursor is allowed to grow a lead sulfide quantum dot array (PbS semiconductor nanocrystal) in situ in the pores of the micro / mesoporous template under high temperature conditions due to the pore confinement effect, and at the same time, the lead precursor and the sulfur precursor on the outer surface of the pores of the micro / mesoporous template generate a lead sulfide body material shell due to the non-pore confinement effect. It should be emphasized that the lead sulfide body material shell is a continuous, non-nanoscale material, and does not refer to lead sulfide quantum dots. Although both use the same material components, they produce very different technical effects in the present invention.

[0034] For example, since the PbS semiconductor nanocrystals are confined to grow in the pores of the micro / mesoporous template, the size of the PbS semiconductor nanocrystals is smaller than its Bohr radius, thereby generating a quantum confinement effect, which has corresponding quantum dot characteristics. Since the lead sulfide body material is stable in nature, it exhibits good chemical stability under normal conditions. The internal PbS semiconductor nanocrystals are double-coated (micro / mesoporous template pores and lead sulfide body material shell), thereby being protected from erosion by water, oxygen and harsh environmental conditions, and finally obtaining high-quality, uniform-sized, and stable lead sulfide quantum dots.

[0035] (2) The PbS semiconductor nanocrystals and the PbS bulk material shell of the present invention are generated simultaneously inside and outside the pores of the micro / mesoporous template, that is to say: the present invention utilizes the confinement difference between the inner and outer surfaces of the mesoporous silicon oxide to generate PbS semiconductor nanocrystals inside the pores and the PbS bulk material shell outside. Since the lead sulfide bulk material matrix is ​​extremely stable and combined with the protection of the silicon oxide pores to form a double protection mechanism, the lead sulfide quantum dots prepared by this method not only take into account the advantages of the prior art, but also perform better in terms of corrosion in harsh environments such as water, oxygen, acid and alkali. When the nucleation and growth of the PbS semiconductor nanocrystal is completed, its exterior is automatically coated with two layers of shells (PbS semiconductor nanocrystals). This is fundamentally different from the technical solution of nucleation and growth first and then external coating in the prior art.

[0036] (3) The present invention adopts a combination of vacuum packaging technology and all-solid-state high-temperature calcination process, without the use of organic solvents, and can achieve stable mass production while being environmentally friendly. At the same time, the prepared PbS quantum dot material has the advantages of high repeatability, good stability, uniform size distribution, resistance to water, oxygen, acid and alkali corrosion, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The XRD pattern of lead sulfide quantum dots prepared in Example 1 of the present invention;

[0038] Figure 2 This is an absorption spectrum of lead sulfide quantum dots prepared in Example 1 of the present invention;

[0039] Figure 3 This is an absorption spectrum of lead sulfide quantum dots prepared in Example 2 of the present invention;

[0040] Figure 4 This is an absorption spectrum of lead sulfide quantum dots prepared in Example 3 of the present invention;

[0041] Figure 5 This is a particle size distribution diagram of the quantum dots after calcination in Example 3 of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] Embodiment 1:

[0044] A self-coating preparation method of PbS quantum dot material comprises the following steps:

[0045] 0.1 mmol PbCl2 and 278 mg MCM-41 were weighed, ground for 20 min, and mixed evenly, and then placed in a quartz tube. The quartz tube was then sealed under ultra-vacuum conditions using a quartz tube vacuum sealing device.

[0046] In an air atmosphere, the quartz tube was placed in a tube furnace, and the mixed powder was calcined at 510°C for 2h, and then cooled to room temperature.

[0047] Take out the mixed powder, add 0.1mmol sulfur powder, grind evenly, and put it in the quartz tube again. Use the quartz tube vacuum packaging equipment to seal the quartz tube under ultra-vacuum conditions, and then place the quartz tube in a tube furnace in an air atmosphere. Use the tube furnace to slowly raise the temperature to 200℃ for 1h, keep it warm for 4h, then raise the temperature to 490℃, keep it warm for 2h, and cool it down to room temperature after calcination. Perform relevant tests on the samples, such as Figure 1 (XRD), Figure 2 (Absorption spectrum). Figure 1 It can be seen that: lattice diffraction proves that there is no impurity phase, and the prepared lead sulfide quantum dots are pure and highly crystalline.

[0048] Embodiment 2:

[0049] A self-coating preparation method of PbS quantum dot material comprises the following steps:

[0050] 0.1 mmol PbCO3 and 267 mg MCM-41 were weighed, ground for 20 min, mixed evenly, and placed in a quartz tube. The quartz tube was then sealed under ultra-vacuum conditions using a quartz tube vacuum sealing device.

[0051] In an air atmosphere, the quartz tube was placed in a tube furnace, and the mixed powder was calcined at 510°C for 2h, and then cooled to room temperature.

[0052] Take out the mixed powder, add 0.12mmol sulfur powder, grind evenly, and put it in the quartz tube again. Use the quartz tube vacuum packaging equipment to seal the quartz tube under ultra-vacuum conditions. Then, place the quartz tube in a tube furnace in an air atmosphere. Use the tube furnace to slowly raise the temperature to 230℃ for 1h, keep it warm for 4h, then raise the temperature to 490℃, keep it warm for 2h, and cool it to room temperature after calcination. Perform relevant tests on the samples, such as Figure 3 (Absorption spectrum).

[0053] Embodiment 3:

[0054] A self-coating preparation method of PbS quantum dot material comprises the following steps:

[0055] 0.08 mmol PbBr2 and 293.6 mg MCM-41 were weighed, ground for 20 min, and mixed evenly, and then placed in a quartz tube. The quartz tube was then sealed under ultra-vacuum conditions using a quartz tube vacuum sealing device.

[0056] In an air atmosphere, the quartz tube was placed in a tube furnace, and the mixed powder was calcined at 510°C for 2h, and then cooled to room temperature.

[0057] Take out the mixed powder, add 0.15mmol sodium sulfide, grind evenly, and put it in a quartz tube again. Use a quartz tube vacuum packaging device to package the quartz tube under ultra-vacuum conditions. In an air atmosphere, place the quartz tube in a tube furnace and use the tube furnace to slowly raise the temperature to 260℃ for 1h, keep it warm for 4h, then raise the temperature to 490℃, keep it warm for 2h, and cool it to room temperature after calcination. Perform relevant tests on the samples, such as Figure 4 (absorption spectrum), Figure 5 (Particle size distribution).

[0058] Depend on Figure 2-Figure 4 It can be seen that the absorption peak of the PbS quantum dot material increases with the proportion of the sulfur precursor and the temperature, indicating that the lead sulfide quantum dots are growing. This can be used to control the size of the PbS quantum dot material.

[0059] Comparative Example 1:

[0060] The difference from Example 1 is that the order of adding the lead precursor powder and the sulfur precursor is replaced.

[0061] Experimental analysis: Due to the low melting point of sulfur powder, if it is pre-embedded into the micro / mesoporous template channels by vacuum sintering, it will evaporate prematurely during the second calcination, resulting in a decrease in the stability of lead sulfide quantum dots.

[0062] Comparative Example 2:

[0063] The difference from Example 1 is that the PbS quantum dot material is prepared by a solution method, specifically, a preparation method of PbS quantum dots modified with short-chain organic ligands disclosed in Patent No. ZL202410888031.9 is adopted.

[0064] Table 1 shows the performance test results of PbS quantum dot samples obtained from Examples 1-3 of the present invention and Comparative Examples 1-2.

[0065] The blue light irradiation test conditions are: after continuous irradiation with 350mW / cm2 blue light (450nm) for 100 hours, the absorption peak intensity of the PbS quantum dot sample can maintain a proportional value of the initial intensity.

[0066] The water and oxygen stability test conditions are: after being placed in air conditions and 90% humidity for 100 hours, the absorption peak intensity of the PbS quantum dot sample can maintain a proportional value of the initial intensity.

[0067] Table 1: Stability test results of examples and comparative examples

[0068]

[0069] The present invention illustrates the detailed preparation method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed preparation method, that is, it does not mean that the present invention must rely on the above-mentioned products and detailed preparation methods to be implemented. It should be clear to those skilled in the art that any improvement of the present invention, the combination or equivalent replacement of the raw materials of the product of the present invention, all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A PbS quantum dot material, characterized in that: The PbS quantum dots are core-shell structures, and the core-shell structure comprises: PbS semiconductor nanocrystals as cores; A micro / mesoporous template, wherein the PbS semiconductor nanocrystal core is confined and grown in the pores of the micro / mesoporous template; A PbS bulk material shell layer is freely grown on the micro / mesoporous template, wherein the PbS bulk material shell layer is a continuous lead sulfide material and has no quantum confinement effect; The particle size of the PbS quantum dot material is not less than 0.5 um.

2. A PbS quantum dot material according to claim 1, characterized in that: The micro / mesoporous template is located between the PbS semiconductor nanocrystal core and the PbS bulk material shell.

3. A PbS quantum dot material according to claim 1, characterized in that: A plurality of discontinuous PbS semiconductor nanocrystals are distributed in the pores of the micro / mesoporous template, and the diameter of at least one of the PbS semiconductor nanocrystals is less than 15 nm.

4. A PbS quantum dot material according to claim 2, characterized in that: The micro / mesoporous template serves as a growth carrier for the PbS semiconductor nanocrystal and the PbS bulk material shell layer.

5. A PbS quantum dot material according to claim 4, characterized in that: The PbS semiconductor nanocrystals and the PbS bulk material shell are simultaneously generated inside and outside the pores of the micro / mesoporous template.

6. A PbS quantum dot material according to claim 1, characterized in that: The particle size range of the PbS quantum dot material is 0.5um-100um.

7. The PbS quantum dot material according to claim 1, characterized in that: The micro / mesoporous template is a microporous material and / or a mesoporous material; The microporous material is one of microporous molecular sieve, microporous silica, microporous titanium dioxide, microporous alumina, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate or microporous transition metal nitride; The mesoporous material is one of mesoporous molecular sieve, mesoporous silica, mesoporous titania, mesoporous alumina, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate or mesoporous transition metal nitride.

8. A self-coating preparation method for PbS quantum dot material according to any one of claims 1 to 7, characterized in that: The steps include: Step S1: mixing lead precursor powder and micro / mesoporous template and grinding to obtain mixture A, placing mixture A in a quartz tube and vacuum sealing the tube; Step S2: calcining the mixture A encapsulated in the quartz tube in step S1 at a temperature higher than the melting point of the lead precursor powder, and then cooling it to room temperature; Step S3: taking out the mixture A after calcination in step S2, mixing it with a sulfur precursor and grinding it to obtain a mixture B, and placing the mixture B in a quartz tube and sealing it under vacuum; Step S4: calcining the mixture B encapsulated in the quartz tube in step S3 within a temperature range higher than the melting point of the sulfur precursor and lower than the boiling point of the sulfur precursor; After the nucleation and growth of PbS semiconductor nanocrystals are completed, the temperature is raised to a temperature above the boiling point of the sulfur precursor so that the sulfur source is completely consumed inside and outside the pores of the micro / mesoporous template, and then cooled to room temperature to obtain the PbS quantum dot material.

9. The method for preparing a PbS quantum dot material by self-coating according to claim 8, characterized in that: The lead precursor powder includes one or more of lead halide, lead acetate, and lead carbonate; The sulfur precursor includes at least one of sulfur powder and sulfide salt; The molar ratio of the sulfur precursor to the lead precursor is at least 1:

1.

10. A PbS quantum dot material according to any one of claims 1 to 7, characterized in that: The PbS quantum dot material is used in a quantum dot diffusion plate, a light-emitting device, a wavelength conversion film, a quantum dot film, a quantum dot light-emitting diode or a quantum dot masterbatch.

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