Monodisperse lead sulfide quantum dot with adjustable size wide range and preparation method thereof
By using thioacetamide as a sulfur source and a thermal injection method, the reaction conditions were precisely controlled, solving the problems of large-size monodispersity and crystal quality in the synthesis of PbS CQDs. This enabled the preparation of lead sulfide quantum dots with a wide range of tunable sizes, which are suitable for applications such as short-wave infrared photodetectors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING UNIV OF CHEM TECH
- Filing Date
- 2026-01-30
- Publication Date
- 2026-05-12
AI Technical Summary
The lack of an ideal sulfur source that is low in cost, chemically stable and moderately reactive in the existing technology makes it difficult to achieve large-size monodispersity and controllable crystal quality in the synthesis of PbS CQDs, and it is also difficult to regulate its optical properties over a wide size range.
Using thioacetamide as the sulfur source and combining it with the hot injection method, monodisperse lead sulfide quantum dots with a wide range of tunable sizes were prepared by precisely controlling the reaction conditions, including temperature, time and ligand ratio.
Lead sulfide quantum dots with uniform size distribution (deviation ≤11.1%) and stable optical properties were successfully synthesized. Their first exciton absorption peak can be continuously tuned in the wavelength range of 1300-2220nm, making them suitable for short-wave infrared photodetectors and other fields.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor quantum dot technology, specifically relating to monodisperse lead sulfide quantum dots with wide-range size tunability and their preparation method. Technical Background
[0002] Lead sulfide quantum dots (PbS CQDs), as a typical group IV-VI narrow bandgap semiconductor nanomaterial, have shown broad application prospects in cutting-edge fields such as solar cells, photodetectors, bioimaging, and light-emitting diodes due to their significant quantum confinement effect, tunable optical bandgap (0.6-1.6 eV), large exciton Bohr radius (≈18 nm), and excellent near-infrared light absorption and emission characteristics. Therefore, developing high-quality, size-controllable, and monodisperse PbS CQD fabrication technology is of vital importance for promoting the performance improvement and industrial application of related optoelectronic devices.
[0003] Currently, various technical routes have been developed for the synthesis of PbS quantum dots (CQDs), mainly including solvothermal methods, thermal injection methods, atomic layer deposition (ALD), laser etching methods, and microwave-assisted methods. Among them, although atomic layer deposition can achieve atomic-level deposition precision, its process parameters are complex. Different sizes of quantum dots require different deposition conditions, and the deposition rate is relatively slow, which can easily lead to an increase in surface defects of quantum dots and a decrease in optical performance. For example, the literature "Ultra-wideband and flat-gain optical properties of the PbS quantum dots-doped silica fiber" (Opt. Express 27, 37900-37909 (2019)) reported the preparation of PbS thin films using the ALD process. The quantum dot size control range was limited to 3.65-4.45 nm, and the absorption peak was located in the near-infrared region, making it difficult to cover the short-wave infrared band. On the other hand, physical etching techniques such as laser etching, while applicable to specific substrates, generally suffer from problems such as easy aggregation of quantum dots, poor monodispersity, and wide size distribution. For example, as shown in the literature "Preparation and characterization of PbS quantum dots by laser ablation technique in the presence of benzene" (J MaterSci: Mater Electron 35, 30 (2024)), the PbS CQDs obtained by this method have short absorption wavelengths, insufficient size uniformity, and strong dependence on the substrate.
[0004] In contrast, the hot-injection method is more suitable for the large-scale preparation of high-quality PbS CQDs due to its relatively simple process, lower cost, and easier control of reaction conditions. The core of this method lies in the activity of the precursor. A highly active precursor can rapidly release sufficient monomer in the reaction system, quickly raising the monomer concentration to the nucleation threshold, thereby inducing uniform nucleation and laying the foundation for the subsequent controllable growth of quantum dots. During the synthesis of PbS CQDs using the hot-injection method, the chemical state of the lead precursor is relatively stable; therefore, the choice of sulfur source becomes a key factor determining the quantum dot synthesis rate, size distribution, and monodispersity.
[0005] In summary, the synthesis of PbS CQDs in the existing technology still faces two major challenges: (1) the lack of an ideal sulfur source that is low-cost, chemically stable, and moderately reactive, in order to achieve controllable and uniform quantum dot growth; and (2) the controllable preparation of large-size PbS CQDs is difficult, and it is hard to simultaneously ensure their good monodispersity and crystal quality. Therefore, developing a preparation method based on a novel sulfur source, with a simple process, effective size control, and especially capable of synthesizing large-size monodisperse PbS CQDs, has become an urgent technical problem to be solved in this field. Summary of the Invention
[0006] The purpose of this invention is to provide monodisperse lead sulfide quantum dots with a wide range of tunable size and a method for their preparation. The aim is to achieve the controllable preparation of lead sulfide quantum dots with high monodispersity and absorption wavelengths covering the short-wave infrared band within a wide size range (4-10 nm) by selecting a suitable sulfur source and precisely controlling the reaction conditions.
[0007] On the one hand, the present invention provides monodisperse lead sulfide quantum dots with wide-range size tunability, using the following technical solution: Monodisperse lead sulfide quantum dots with a wide range of tunable size, wherein the lead sulfide quantum dots have a size of 4-10 nm, a size distribution deviation of ≤11.1%, and a first exciton absorption peak wavelength of 1300-2220 nm.
[0008] Preferably, the size distribution deviation of the lead sulfide quantum dots is ≤10%, and the wavelength of the first exciton absorption peak of the lead sulfide quantum dots is in the range of 1400-2200 nm.
[0009] On the other hand, the present invention also provides a method for preparing the above-mentioned monodisperse lead sulfide quantum dots with wide-range tunable size, using the following technical solution: A method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range includes the following steps: 1) A sulfur precursor solution was prepared by mixing a sulfur source, 1-octadecene, and a ligand solvent; 2) Mix oleic acid, lead oxide and 1-octadecene, and heat under an inert atmosphere to prepare lead oleate solution; 3) The sulfur precursor solution obtained in step 1) is injected into the lead oleate solution obtained in step 2), and the reaction is heated to obtain a mixed solution of lead sulfide quantum dots. 4) The mixed solution obtained in step 3) is purified to obtain lead sulfide quantum dots.
[0010] Preferably, in step 1), the molar ratio of the sulfur source, 1-octadecene, and ligand solvent is in the range of 1:5:10 to 1:10:5; The sulfur source is at least one of bis(trimethylsilyl) sulfide, thioacetamide, and sulfur powder; The ligand solvent is either trioctylphosphine or oleylamine.
[0011] Preferably, in step 1), the sulfur source is thioacetamide.
[0012] Preferably, in step 2), the molar ratio of lead oxide, oleic acid, and 1-octadecene is in the range of 1:16:36-1:4:48; and the temperature of the heating reaction is 140-160℃.
[0013] Preferably, in step 3), the molar ratio of lead to sulfur in the mixed solution is in the range of 1:4 to 4:1.
[0014] Preferably, in step 3), the heating reaction temperature is 130-170℃ and the reaction time is 2-6 min.
[0015] Preferably, in step 4), the purification process includes mixing the mixed solution obtained in step 3) with the antisolvent, centrifuging, and collecting the precipitate; The antisolvent is a mixed solution of isopropanol and acetone, with a volume ratio of isopropanol to acetone of 2:1.
[0016] Preferably, in step 4), the purification process further includes redissolving the obtained precipitate with a normal solvent; The positive solvent is n-hexane.
[0017] In summary, the present invention has the following beneficial technical effects: 1. By optimizing the selection of sulfur precursors and coordinating the control of multiple parameters, this invention successfully synthesized lead sulfide quantum dots with precisely adjustable size in the range of 4-10 nm and uniform size distribution (deviation ≤11.1%). The first exciton absorption peak can be continuously controlled in a wide wavelength range of 1300-2220 nm. In particular, it has achieved the stable synthesis of large-size quantum dots with absorption wavelengths exceeding 2000 nm.
[0018] 2. This invention selects thioacetamide as the optimal sulfur precursor, which is inexpensive, relatively stable to air and humidity, and has a mild reaction, making the growth process more controllable.
[0019] 3. The lead sulfide quantum dot sol prepared by this invention has a stable Tyndall effect and shows no sedimentation after being stored in air for a week, demonstrating good colloidal stability. Its excellent short-wave infrared absorption characteristics and structural stability can be directly adapted to multiple fields such as short-wave infrared photodetectors, solar cells, bioimaging, and light-emitting diodes, especially meeting the needs of high-end photoelectric detection for long-wavelength absorption quantum dots. Attached Figure Description
[0020] Figure 1 The X-ray diffraction pattern of lead sulfide quantum dots prepared in Example 1 of this invention; Figure 2 This is a TEM image of the lead sulfide quantum dots prepared in Example 1 of the present invention; Figure 3 The image shows the HRTEM image of the lead sulfide quantum dots prepared in Example 1 of this invention. Figure 4 This is a particle size distribution diagram of lead sulfide quantum dots prepared in Example 1 of the present invention; Figure 5 The normalized absorption spectrum of lead sulfide quantum dots prepared in Example 1 of this invention; Figure 6 The image shows a physical picture of the lead sulfide quantum dot sol prepared in Example 1 of this invention and the Tyndall effect. Figure 7 The normalized absorption spectra of lead sulfide quantum dots prepared in Examples 1-5 of this invention are shown. Figure 8 The normalized absorption spectra of lead sulfide quantum dots prepared in Examples 1 and 6-9 of this invention are shown below. Figure 9 The normalized absorption spectra of lead sulfide quantum dots prepared in Examples 1 and 10-11 of this invention are shown below. Figure 10 The image shown is an HRTEM image of lead sulfide quantum dots prepared in Example 10 of this invention. Figure 11 The normalized absorption spectra of lead sulfide quantum dots prepared in Examples 1, 10 and 12-13 of this invention are shown below. Figure 12 The image shown is an HRTEM image of the lead sulfide quantum dots prepared in Example 12 of this invention. Figure 13 This is an HRTEM image of the lead sulfide quantum dots prepared in Example 13 of the present invention. Detailed Implementation
[0021] The following is in conjunction with Examples 1-13 and the appendix to the instruction manual. Figure 1-13 The present invention will be described in further detail below.
[0022] Example Example 1 A method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range includes the following steps: S1. Preparation of sulfur precursor solution: Thioacetamide, oleylamine and 1-octadecene were added sequentially to a three-necked flask. Oxygen and moisture in the three-necked flask were removed using a double-row tube. The mixture was stirred and left to stand, resulting in a homogeneous and transparent solution, which is the sulfur precursor solution. The molar ratio of thioacetamide, oleylamine, and 1-octadecene is 1:7:8. S2. Preparation of lead precursor solution: Under an inert atmosphere, 1-octadecene, lead oxide and oleic acid were added to a reaction vessel. The resulting mixture was placed at 150°C and evacuated for 40±5 min to obtain a colorless and transparent lead oleate solution. The molar ratio of lead oxide, oleic acid and 1-octadecene is 1:16:36. Adjust the amount of 1-octadecene according to the amount of oleic acid added, so that the total volume of the lead precursor solution remains constant at 30 mL. The purpose of vacuuming is not only to remove air and moisture from the reaction vessel and prevent lead oleate from oxidizing and deteriorating, but also to enhance the stability of the reaction system. S3, Synthesis of lead sulfide quantum dots: The temperature was stabilized at 150℃. The sulfur precursor solution obtained in step S1 was rapidly injected into the lead oleate solution obtained in step S2 using a syringe. The lead oleate solution immediately turned blackish-brown upon injection of the sulfur precursor solution, indicating the formation of lead sulfide quantum dots. The temperature was maintained at 150±0.5℃ for 6±0.5 min. The reaction ended when the timer ended. 15 mL of n-hexane was injected to quench the reaction, achieving rapid cooling and reducing the monomer concentration, thus terminating the reaction and obtaining a mixed solution of lead sulfide quantum dots. At this point, the lead-to-sulfur ratio in the lead sulfide quantum dot mixed solution is 2:1; S4. Purification of lead sulfide quantum dots: The lead sulfide quantum dot mixture obtained in step S3 and the antisolvent were added to a centrifuge and rotated at 9000 rpm to remove impurities such as organic solvents. After centrifugation, the supernatant was removed, and the black precipitate obtained was lead sulfide quantum dots (PbS CQDs). During centrifugation, the color of the supernatant after centrifugation can be used to determine whether purification is complete. The more times the supernatant is centrifuged, the clearer it becomes and the purer the quantum dots are. Purification is complete when the supernatant is almost transparent. Usually, repeating this process 1-3 times is sufficient. The precipitate is redissolved in hexane as the positive solvent, and a mixture of isopropanol and acetone in a volume ratio of 2:1 is used as the antisolvent.
[0023] Reference Figure 1 The lead sulfide quantum dots prepared in Example 1 were placed in a vacuum oven and dried at 50°C for 1 hour. The dried powder was then characterized. Figure 1 It is known that the crystal structure of lead sulfide quantum dots belongs to the cubic rock salt structure. The XRD pattern shows that the synthesized PbS CQDs have nine obvious diffraction peaks at 25.72°, 29.88°, 42.88°, 50.78°, 53.32°, 62.36°, 68.70°, 70.92° and 78.74°. By comparing with the standard diffraction peak card of PbS (JCPDS No: 05-0592), the synthesized PbS CQDs have crystal planes of (111), (200), (220), (311), (222), (400), (331), (420) and (422), which are consistent with the international standard PDF card, indicating that high-quality PbS CQDs were obtained by the method of Example 1 of this invention.
[0024] Reference Figure 2 As can be seen from the transmission electron microscope (TEM) image of the PbS CQDs prepared in Example 1 of the present invention, the PbS CQDs have relatively uniform size and good monodispersity, and the size of the synthesized PbS CQDs is 7.5-8.5 nm.
[0025] Reference Figure 3 As can be seen from the high-resolution transmission electron microscope (HRTEM) image of PbS CQDs obtained in Example 1 of this invention and the interplanar spacing measurement results, the lattice fringes of PbS CQDs are clearly defined, and the interplanar spacing measurement results are 0.20 nm and 0.29 nm, which belong to the (220) crystal plane and (200) crystal plane of the PbS cubic structure, respectively.
[0026] Reference Figure 4 The particle size distribution of PbS CQDs obtained in Example 1 of this invention shows that the particle size is mainly concentrated around 8.19±0.04nm, which indirectly proves that the synthesized PbS CQDs have uniform size.
[0027] Reference Figure 5 As can be seen from the normalized absorption spectrum, the first exciton absorption peak of the PbS CQDs prepared in Example 1 is at 1936 nm, indicating that it has potential application value in the field of short-wave infrared photodetectors.
[0028] Reference Figure 6 As can be seen from the photographs of the PbS CQDs sol, the PbS CQDs sol synthesized in Example 1 exhibits a significant Tyndall effect. Furthermore, no sedimentation occurred after being stored in air for one week.
[0029] Example 2 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from Example 1 in that the reaction time in step S3 is 2 ± 0.5 min, while the remaining steps are the same as in Example 1.
[0030] Example 3 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from Example 1 in that the reaction time in step S3 is 3 ± 0.5 min, while the remaining steps are the same as in Example 1.
[0031] Example 4 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from Example 1 in that the reaction time in step S3 is 4 ± 0.5 min, while the remaining steps are the same as in Example 1.
[0032] Example 5 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from Example 1 in that the reaction time in step S3 is 5 ± 0.5 min, while the remaining steps are the same as in Example 1.
[0033] Reference Figure 7 The PbS CQDs prepared in Examples 1-5 showed that the first exciton absorption peak of the quantum dots gradually red-shifted with increasing growth time, indicating that the absorption wavelength gradually increased; this further proves that the size of PbS CQDs can be controlled by adjusting the growth time.
[0034] Example 6 The method for preparing monodisperse lead sulfide quantum dots with a wide size range is different from that in Example 1. In step S2, the molar ratio of oleic acid to lead oxide is 13:1. The amount of 1-octadecene is adjusted according to the amount of oleic acid added so that the total volume of the lead precursor solution remains unchanged at 30 mL. The remaining steps are the same as in Example 1.
[0035] Example 7 The method for preparing monodisperse lead sulfide quantum dots with a wide range of adjustable sizes differs from that in Example 1 in that, in step S2, the molar ratio of oleic acid to lead oxide is 10:1, and the amount of 1-octadecene is adjusted according to the amount of oleic acid added to keep the total volume of the lead precursor solution constant at 30 mL. The remaining steps are the same as in Example 1.
[0036] Example 8 The method for preparing monodisperse lead sulfide quantum dots with a wide range of adjustable sizes differs from Example 1 in that, in step S2, the molar ratio of oleic acid to lead oxide is 7:1, and the amount of 1-octadecene is adjusted according to the amount of oleic acid added to keep the total volume of the lead precursor solution constant at 30 mL. The remaining steps are the same as in Example 1.
[0037] Example 9 The method for preparing monodisperse lead sulfide quantum dots with a wide range of adjustable sizes differs from that in Example 1 in that, in step S2, the molar ratio of oleic acid to lead oxide is 4:1, and the amount of 1-octadecene is adjusted according to the amount of oleic acid added to keep the total volume of the lead precursor solution constant at 30 mL. The remaining steps are the same as in Example 1.
[0038] Reference Figure 8 In Examples 1 and 6-9, the PbS CQDs obtained exhibited a regular red shift in the first exciton absorption peak as the molar ratio of oleic acid to lead oxide increased. This indicates that during quantum dot growth, sufficient ligand supply provides favorable conditions for the size growth of PbS CQDs, thereby enabling the quantum dots to grow sufficiently.
[0039] Example 10 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from that in Example 1 in that the reaction temperature in step S3 is 170°C, while the other steps are the same as in Example 1.
[0040] Reference Figure 10 The high-resolution transmission electron microscopy (HRTEM) images of PbS CQDs prepared in Example 10 of this invention show that the lattice fringes of PbS CQDs are clear and continuous, with no obvious lattice dislocations or defects. The quantum dots are independently dispersed without agglomeration, proving that even at a relatively high reaction temperature of 170°C, using thioacetamide as the sulfur source can still ensure the high crystallinity and excellent monodispersity of the quantum dots. This further proves that thioacetamide is a stable sulfur source suitable for a wide temperature range.
[0041] Example 11 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from that in Example 1 in that the reaction temperature in step S3 is 130°C, while the other steps are the same as in Example 1.
[0042] Reference Figure 9 Based on Example 1, increasing the reaction temperature further red-shifts the absorption peak wavelength to 2210 nm. This indicates that increasing the temperature increases the molecular thermal driving force within the system, promoting further growth of quantum dots. Conversely, at low temperatures, the molecular thermal driving force of quantum dots is insufficient, resulting in uneven growth rates and a shoulder-shaped peak in the absorption spectrum.
[0043] Example 12 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from that in Example 1 in that, in step S1, thioacetamide is replaced with an equal amount of bis(trimethylsilyl) sulfide; oleylamine is replaced with an equal amount of trioctylphosphine; the remaining steps are the same as in Example 1.
[0044] Example 13 The method for preparing monodisperse lead sulfide quantum dots with a wide range of tunable size differs from that in Example 1 in that, in step S1, thioacetamide is replaced with an equal amount of sulfur powder, while the remaining steps are the same as in Example 1.
[0045] Reference Figure 11 In Example 12, when bis(trimethylsilyl) sulfide was used as the sulfur source, the first exciton absorption peak of the obtained PbS CQDs was located at 1588 nm. In Examples 1 and 10, the quantum dots prepared with thioacetamide as the sulfur source had an initial position of 1936 nm for the first exciton absorption peak, and this absorption peak could be red-shifted to 2210 nm by increasing the reaction temperature, demonstrating excellent temperature control characteristics. In Example 13, when sulfur powder was used as the sulfur source, the position of the first exciton absorption peak of the product was also near 2220 nm, which was similar to the absorption peak position of the quantum dots prepared with thioacetamide as the sulfur source under high temperature conditions. However, the absorption peak half-width of the former was significantly wider. This phenomenon indicates that the monodispersity of PbS CQDs prepared with sulfur powder as the sulfur source was poor.
[0046] Reference Figure 12 As can be seen from the high-resolution transmission electron microscope (HRTEM) image of PbS CQDs obtained in Example 12 of this invention, the quantum dots exhibit good dispersion, but slight aggregation occurs in some areas, and the lattice fringes are blurred and have poor continuity in some regions. This proves that when bis(trimethylsilyl) sulfide is used as the sulfur source, the crystal integrity of the quantum dots is weaker than that of the product with thioacetamide as the sulfur source.
[0047] Reference Figure 13 As can be seen from the high-resolution transmission electron microscopy (HRTEM) image of PbS CQDs obtained in Example 13 of this invention, the quantum dot aggregation phenomenon is more obvious. Multiple quantum dots are adhered to each other, with significant size differences, and no clear lattice fringes in some areas. This proves that when sulfur powder is used as the sulfur source, the growth process of quantum dots is difficult to control precisely, resulting in a decrease in dispersibility and crystal quality.
[0048] Furthermore, the comparative data of the PbS CQDs particle size variation coefficient CV, i.e. monodispersity, obtained from Examples 1, 10, and 12-13 are shown in Table 1.
[0049] Table 1. Coefficient of variation of PbS CQDs
[0050] The comparative data in Table 1 show that the PbS CQDs prepared using thioacetamide as the sulfur source exhibit better monodispersity, indicating that the particle size distribution is more concentrated compared to quantum dots prepared using bis(trimethylsilyl) sulfide and sulfur powder as sulfur sources. Furthermore, the monodispersity did not change significantly after increasing the reaction temperature.
[0051] The embodiments shown in this specification are only used to illustrate the technical solutions of the present invention and are intended to help those skilled in the art understand the principles and advantages of the present invention. They do not constitute a limitation on the scope of protection of the present invention. Although the present invention has been specifically described, those skilled in the art can still make any modifications, equivalent substitutions or other reasonable variations to the implementation methods without departing from the spirit and scope of the present invention. All equivalent technical solutions resulting therefrom should be considered within the scope of protection of this patent.
Claims
1. Monodisperse lead sulfide quantum dots with a wide size tunable range, characterized in that, The lead sulfide quantum dots have a size of 4-10 nm and a size distribution deviation of ≤11.1%. The first exciton absorption peak wavelength of the lead sulfide quantum dots is in the range of 1300-2220 nm.
2. The monodisperse lead sulfide quantum dots with wide-range size tunability according to claim 1, characterized in that, The size distribution deviation of the lead sulfide quantum dots is ≤10%, and the wavelength of the first exciton absorption peak of the lead sulfide quantum dots is in the range of 1400-2200nm.
3. A method for preparing monodisperse lead sulfide quantum dots with a wide size range tunable as described in any one of claims 1-2, characterized in that, Includes the following steps: 1) A sulfur precursor solution was prepared by mixing a sulfur source, 1-octadecene, and a ligand solvent; 2) Mix oleic acid, lead oxide and 1-octadecene, and heat under an inert atmosphere to prepare lead oleate solution; 3) The sulfur precursor solution obtained in step 1) is injected into the lead oleate solution obtained in step 2), and the reaction is heated to obtain a mixed solution of lead sulfide quantum dots. 4) The mixed solution obtained in step 3) is purified to obtain lead sulfide quantum dots.
4. The method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range according to claim 3, characterized in that, In step 1), the molar ratio of the sulfur source, 1-octadecene, and ligand solvent is in the range of 1:5:10 to 1:10:5; The sulfur source is at least one of bis(trimethylsilyl) sulfide, thioacetamide, and sulfur powder; The ligand solvent is either trioctylphosphine or oleylamine.
5. The method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range according to claim 4, characterized in that, In step 1), the sulfur source is thioacetamide.
6. The method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range according to claim 3, characterized in that, In step 2), the molar ratio of lead oxide, oleic acid, and 1-octadecene is in the range of 1:16:36-1:4:48; the temperature of the heating reaction is 140-160℃.
7. The method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range according to claim 3, characterized in that, In step 3), the molar ratio of lead to sulfur in the mixed solution is in the range of 1:4 to 4:
1.
8. The method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range according to claim 3, characterized in that, In step 3), the heating reaction temperature is 130-170℃ and the reaction time is 2-6 min.
9. The method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range according to claim 3, characterized in that, In step 4), the purification process includes mixing the mixed solution obtained in step 3) with the antisolvent, centrifuging, and collecting the precipitate; The antisolvent is a mixed solution of isopropanol and acetone, with a volume ratio of isopropanol to acetone of 2:
1.
10. The method for preparing monodisperse lead sulfide quantum dots with a wide size tunable range according to claim 9, characterized in that, In step 4), the purification process further includes redissolving the resulting precipitate with a normal solvent; The positive solvent is n-hexane.