A method for preparing multi-shell coated ZnSe-based blue-violet light quantum dots

Abstract

The invention discloses a method for preparing ZnSe-based blue-violet light quantum dots coated with multiple shells. The method comprises the following steps: injecting a Se precursor solution into a first Zn precursor solution to obtain a ZnSe quantum dot crystal nucleus solution; injecting a second Zn precursor solution into the ZnSe quantum dot crystal nucleus solution, heating up and injecting a first coordination solvent to obtain a ZnSe / 1-layer ZnS quantum dot solution; performing N-1 injection operations on the ZnSe / 1-layer ZnS quantum dot solution, where N=3-5, to obtain a ZnSe / N-layer ZnS quantum dot solution, wherein each injection operation comprises: injecting a third Zn precursor solution into the ZnSe / 1-layer ZnS quantum dot solution; and purifying the ZnSe / N-layer ZnS quantum dot solution for multiple times to obtain ZnSe-based blue-violet light quantum dots.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum dot light-emitting display, and particularly relates to a preparation method of multi-shell-coated ZnSe-based blue-violet quantum dots. Background Art

[0002] Blue light quantum dot light-emitting diodes (QLEDs) are the key to realizing self-luminous full-color quantum dot electroluminescent displays, and blue light quantum dots have become the core materials leading the blue light QLEDs technology. Among blue light quantum dot materials, environmentally friendly indium phosphide (InP) quantum dots have problems of relatively small particle sizes,较多的表面缺陷及表面易氧化的问题,导致InP基QLEDs具有较低的发光效率和较低的单色性,这限制了其实用化进程。

[0003] Therefore, as another type of environmentally friendly binary metal chalcogenide quantum dots have received extensive attention. The binary metal chalcogenide quantum dots are blue light quantum dots, and their general formula is M x E y (M = Zn, Ag or Cu, E = S, Se or Te; 0 < x ≤ 2, 0 < y ≤ 1). Among them, zinc selenide (ZnSe) has a relatively wide band gap ( E g = 2.7 eV), and blue light-emitting ZnSe quantum dots can be synthesized by changing the stoichiometric ratio and controlling the particle size. Therefore, ZnSe has received extensive attention.

[0004] The LaMer model is a widely used model for quantum dot growth, that is, metal precursors and chalcogen element precursors react to form monomers, and then the monomers aggregate into larger nuclei, and then the nuclei grow into quantum dots through monomer "addition". Usually, according to the LaMer model, the nucleation and growth of ZnSe quantum dots is to quickly inject a selenium source into a hot solution with a relatively high nucleation temperature (290~320 °C). However, Ostwald ripening occurs at high temperatures, which will result in a relatively wide particle size distribution of ZnSe quantum dots, affecting the luminous efficiency of ZnSe quantum dots and being not suitable for large-scale industrial production. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of multi-shell-coated ZnSe-based blue-violet quantum dots, and the ZnSe-based blue-violet quantum dots realize the emission of blue-violet light with a wavelength of 400~425 nm under the excitation of a 350 nm wavelength.

[0006] The purpose of the present invention is achieved by the following technical solutions.

[0007] A preparation method of ZnSe-based blue-violet quantum dots includes the following steps:

[0008] Step 1, uniformly mixing a first Zn source and a first non-coordinating solvent, keeping the mixture at 100-150° C. for 5-20 minutes, and then naturally cooling the mixture to 50-60° C. to obtain a first Zn precursor solution, heating the first Zn precursor solution at 50-60° C. to 220-270° C. and keeping the mixture at 5-20 minutes, injecting a Se precursor solution at room temperature of 20-25° C. into the first Zn precursor solution at 220-270° C., and keeping the mixture at 220-270° C. for 5-30 minutes to obtain a ZnSe quantum dot nucleus solution, wherein the Se precursor solution is uniformly obtained by mixing a Se source, dodecanethiol, and a second non-coordinating solvent, and the ratio of the Se element in the Se precursor solution to the Zn element in the first Zn precursor solution is (0.3-0.6):(1-3) in terms of the amount of the substance.

[0009] In step 1, the first Zn source is a mixture of one or both of zinc laurate and zinc stearate, the first non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane, the Se source is Se powder, and the second non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane.

[0010] In step 1, the ratio of the amount of Se element in the Se source, the volume of dodecanethiol and the volume of the second non-coordinating solvent is (0.3-0.6): (0.1-1): (5-12), the unit of the amount of Se element is mmol, and the unit of the volume is mL.

[0011] In step 1, the ratio of the amount of the Zn element in the first Zn source to the volume of the first non-coordinating solvent is (1-3): (3-10), the unit of the amount of the substance is mmol, and the unit of the volume is mL.

[0012] Step 2, cooling the ZnSe quantum dot crystal core solution at 220-270°C to 100-130°C, injecting a second Zn precursor solution at 50-60°C into the ZnSe quantum dot crystal core solution at 100-130°C, then heating it to 140-170°C, injecting the first coordination solvent and keeping it at 140-170°C for 5-30 minutes to obtain a ZnSe / 1-Layer ZnS quantum dot solution, wherein the method for preparing the second Zn precursor solution comprises: uniformly mixing a second Zn source, a second coordination solvent and a third non-coordinating solvent, keeping it at 70-120°C for 5-10 minutes, and then naturally cooling it to 50-60°C to obtain a second Zn precursor solution, wherein the ratio of the Zn element in the first Zn precursor solution to the Zn element in the second Zn precursor solution is 1:(0.3-0.7) in terms of the amount of substance;

[0013] In step 2, the second Zn source is zinc diethyldithiocarbamate, the first coordinating solvent is one of tributylphosphine and trioctylphosphine, the second coordinating solvent is one of n-octylamine and oleylamine, and the third non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane.

[0014] In step 2, the ratio of the amount of the Zn element in the second Zn source, the volume of the second coordinating solvent and the volume of the third non-coordinating solvent is (0.1-0.5): (0.5-2): (3-7), the unit of the amount of the substance is mmol, and the unit of the volume is mL.

[0015] In the step 2, the ratio of the first coordinating solvent to the second coordinating solvent is (1-3): (2-5) by volume.

[0016] Step 3, cooling the ZnSe / 1-Layer ZnS quantum dot solution to 100-130°C, performing N-1 injection operations into the ZnSe / 1-Layer ZnS quantum dot solution at 100-130°C, N=3-5, to obtain a ZnSe / N-Layer ZnS quantum dot solution, each injection operation comprising: injecting a third Zn precursor solution at room temperature of 20-25°C into the ZnSe / 1-Layer ZnS quantum dot solution at 100-130°C, then heating to 220-250°C, and keeping warm for 10-60min, wherein when the number of injection operations is less than or equal to N-2 times, cooling to 100-130°C after each injection operation; when the number of injection operations is equal to N-1 times, cooling to room temperature of 20-25°C using liquid nitrogen or liquid helium within 5-10s after the N-1 injection operation;

[0017] The third Zn precursor solution is obtained by uniformly mixing a third Zn source, an S source and a fourth non-coordinating solvent, and the ratio of the amount of the Zn element in the second Zn precursor solution to the volume of the third Zn precursor solution injected in each injection operation is (0.1-0.5): 1, the unit of the amount of the substance is mmol, and the unit of the volume is mL;

[0018] In step 3, the third Zn source is one of zinc stearate, zinc acetate and zinc laurate, the S source is a mixture of one or more of dodecanethiol, tert-dodecyl mercaptan and octanethiol, and the fourth non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane.

[0019] In step 3, the ratio of the amount of Zn element in the third Zn source, the volume of the S source and the volume of the fourth non-coordinating solvent is (0.3-0.6): (1-2): (5-10), the unit of the amount of Zn is mmol, and the unit of the volume is mL.

[0020] Step 4, purifying the ZnSe / N-Layer ZnS quantum dot solution multiple times to obtain ZnSe-based blue-violet quantum dots.

[0021] In step 4, each purification operation includes: mixing with a first organic solvent or a second organic solvent, centrifuging to obtain a precipitate, and dispersing the precipitate with n-hexane, wherein the first organic solvent is a mixture of at least two of ethanol, isopropanol and acetone, and the second organic solvent is a mixture of at least two of methanol, octane and acetone.

[0022] In step 4, when the first organic solvent is used for purification, the ratio of the ZnSe / N-LayerZnS quantum dot solution to the first organic solvent used for purification is (1-3):(2-7) by volume.

[0023] In step 4, when a second organic solvent is used for purification, the ratio of the ZnSe / N-LayerZnS quantum dot solution to the second organic solvent used for purification is (1-3):(3-6) by volume.

[0024] In step 4, the ratio of the ZnSe / N-Layer ZnS quantum dot solution to the n-hexane used in each purification is (1-3): (2-6) by volume.

[0025] In the above technical solution, the heating rate is 5-10°C / min.

[0026] In the above technical solution, the cooling rate is 10-15°C / min.

[0027] In the above technical solution, steps 1 to 4 are carried out under an inert protective atmosphere or an argon protective atmosphere.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The ZnSe-based blue-violet quantum dots of the present invention have a high relative fluorescence quantum yield of up to 85%, a long fluorescence lifetime, and good luminous efficiency. The ZnSe-based blue-violet quantum dots have a single zinc metal and are non-toxic to heavy metals, providing a basis for environmentally friendly applications. In addition, the ZnSe-based blue-violet quantum dots have a multi-shell structure, which achieves thick layer coating, passivates surface defects, and improves the relative fluorescence quantum yield.

[0030] (2) The preparation method of the present invention realizes the synthesis of ZnSe-based blue-violet quantum dots with a multi-shell structure at a low temperature of 220-270°C, which has significant safety and high efficiency characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a high-resolution transmission electron microscopy (HRTEM) image, wherein (a) is the ZnSe-based blue-violet quantum dots prepared in Comparative Example 1, and (b) is the ZnSe-based blue-violet quantum dots prepared in Example 2;

[0032] Figure 2 The X-ray photoelectron spectroscopy (XPS) diagram of the ZnSe-based blue-violet quantum dots prepared in Example 2, wherein (a) is the Zn 2p spectrum, (b) is the Se 3d spectrum, and (c) is the S 2p spectrum;

[0033] Figure 3 The fluorescence emission spectra (PL) of ZnSe-based blue-violet quantum dots prepared in Examples 1-2, Example 5 and Comparative Examples 1-2 are shown;

[0034] Figure 4 The fluorescence emission spectra of ZnSe-based blue-violet quantum dots prepared in Examples 3-4 and 6-7;

[0035] Figure 5 The transient fluorescence spectra of ZnSe-based blue-violet quantum dots prepared in Example 1 and Comparative Example 1;

[0036] Figure 6 This is a transient fluorescence spectrum of the ZnSe-based blue-violet quantum dots prepared in Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0038] Embodiments 1 to 7

[0039] A method for preparing ZnSe-based blue-violet quantum dots comprises the following steps:

[0040] Step 1, placing a first Zn source and a first non-coordinating solvent in a three-necked flask and mixing them evenly, heating them to 120°C at a rate of 10°C / min under an argon protective atmosphere and keeping them at 120°C for 5 minutes, and then naturally cooling them to 50°C to obtain a first Zn precursor solution, heating the 50°C first Zn precursor solution to T°C at a rate of 10°C / min and keeping them at T°C for 15 minutes, injecting a Se precursor solution at a room temperature of 20-25°C into the first Zn precursor solution at T°C, and keeping them at T°C for 20 minutes to obtain a ZnSe quantum dot nucleus solution, wherein the method for obtaining the Se precursor solution comprises: in an argon protective atmosphere, mixing the Se source, dodecanethiol and the second non-coordinating solvent evenly in a three-necked flask by ultrasonication at a room temperature of 20-25°C for 20 minutes to obtain To a Se precursor solution, the first Zn source is zinc laurate, the first non-coordinating solvent is octadecene, the Se source is Se powder, the second non-coordinating solvent is a mixture of octadecene and hexadecane, the ratio of octadecene in the second non-coordinating solvent to hexadecane in the second non-coordinating solvent is 1.5:1 by volume, the ratio of Se element in the Se precursor solution to Zn element in the first Zn precursor solution is 0.3:2, the ratio of the molar fraction of Zn element in the first Zn source to the volume fraction of the first non-coordinating solvent is 2:5, the ratio of the molar fraction of Se element in the Se source, the volume fraction of dodecanethiol and the volume fraction of the second non-coordinating solvent is 0.3:0.8:6, the unit of the molar fraction is mmol, and the unit of the volume fraction is mL.

[0041] Step 2, cooling the ZnSe quantum dot crystal core solution at T℃ to 100℃ at a rate of 15℃ / min, injecting a second Zn precursor solution at 50℃ into the ZnSe quantum dot crystal core solution at 100℃, then heating it to 150℃ at a rate of 10℃ / min, and then injecting the first coordinating solvent and keeping it at 150℃ for 20min to obtain a ZnSe / 1-Layer ZnS quantum dot solution, wherein the method for preparing the second Zn precursor solution comprises: placing a second Zn source, a second coordinating solvent and a third non-coordinating solvent in a three-necked flask and mixing them evenly, keeping them at 80℃ for 5min in an argon protective atmosphere, and then naturally cooling them to 50℃ to obtain a second Zn precursor solution, wherein the first coordinating solvent is tributylphosphine, the second Zn source is zinc diethyldithiocarbamate, the second coordinating solvent is n-octylamine, and the third non-coordinating solvent is a mixture of octadecene and hexadecane, and the third non-coordinating solvent is 1:100℃, 1:100℃, and 1:100℃. The ratio of octadecene in the first Zn precursor solution to hexadecane in the third non-coordinating solvent is 1:1.5, the ratio of the Zn element in the first Zn precursor solution to the Zn element in the second Zn precursor solution is W, the ratio of the Zn element in the second Zn source, the volume fraction of the second coordinating solvent and the volume fraction of the third non-coordinating solvent is 0.2:1:5, the ratio of the first coordinating solvent to the second coordinating solvent is 2:3.5, the unit of the substance amount is mmol, and the unit of the volume fraction is mL;

[0042] Step 3, the 150 ° C ZnSe / 1-Layer ZnS quantum dot solution is cooled to 100 ° C at a rate of 15 ° C / min, and the 100 ° C ZnSe / 1-Layer ZnS quantum dot solution is injected N-1 times to obtain a ZnSe / N-Layer ZnS quantum dot solution, each injection operation includes: injecting a third Zn precursor solution at a room temperature of 20~25 ° C into the 100 ° C ZnSe / 1-Layer ZnS quantum dot solution, and then heating to 220 ° C at a rate of 10 ° C / min, and keeping warm for 30 minutes, wherein, when the number of injection operations is less than or equal to N-2 times, the temperature is lowered to 100 ° C after each injection operation; when the number of injection operations is equal to N-1 times, liquid nitrogen is used to cool the room temperature of 20~25 ° C within 10 seconds after the N-1 injection operation (ZnSe / N-Layer The ZnS quantum dot solution is in liquid state); wherein the ratio of the amount of the Zn element in the second Zn precursor solution to the volume of the third Zn precursor solution injected in each injection operation is 0.2:1, the unit of the amount of the substance is mmol, and the unit of the volume is mL;

[0043] The method for obtaining a third Zn precursor solution comprises: in an argon protective atmosphere, uniformly mixing a third Zn source, an S source and a fourth non-coordinating solvent by ultrasonication at room temperature of 20-25° C. for 20 minutes to obtain a third Zn precursor solution, wherein the third Zn source is zinc stearate, the fourth non-coordinating solvent is octadecene, the S source is dodecanethiol, the ratio of the amount of substance of the Zn element in the third Zn source, the volume fraction of the S source and the volume fraction of the fourth non-coordinating solvent is 0.4:1.6:7, the unit of the amount of substance is mmol, and the unit of the volume fraction is mL.

[0044] Step 4, purifying 3mL ZnSe / N-Layer ZnS quantum dot solution twice to obtain ZnSe-based blue-violet quantum dots, wherein the two purification operations include: first mixing with an excess of a first organic solvent, centrifuging at a speed of 10000rpm for 10min to obtain a precipitate, dispersing the precipitate with 3mL of n-hexane, and then mixing with a second organic solvent, centrifuging at a speed of 10000rpm for 10min (excess is defined as: coagulation begins to occur after dropwise addition until the generated precipitate no longer increases), obtaining a precipitate, and then dispersing the precipitate with 3mL of n-hexane to obtain a ZnSe-based blue-violet quantum dot spin coating liquid containing ZnSe-based blue-violet quantum dots, wherein the first organic solvent is a mixture of ethanol and acetone, and the ratio of ethanol to acetone is 2:5 by volume, and the second organic solvent is a mixture of methanol and octane, and the ratio of methanol to octane is 1:5 by volume, and the ZnSe / N-Layer The ratio of the ZnS quantum dot solution, the first organic solvent and the second organic solvent is 3:7:6.

[0045] The T, N and W of the ZnSe-based blue-violet quantum dots prepared in Examples 1 to 7 are shown in Table 1.

[0046] Table 1

[0047]

[0048] In the above step 1, a ZnSe quantum dot crystal nucleus is formed;

[0049] In the above step 2, a first ZnS shell layer is formed covering the ZnSe quantum dot crystal core;

[0050] In the above step 3, a second ZnS shell layer is formed each time the implantation operation is performed.

[0051] Comparative Example 1

[0052] A method for preparing ZnSe-based blue-violet quantum dots comprises the following steps: purifying the ZnSe quantum dot nucleus solution in step 1 of embodiment 2 in step 4 of embodiment 2 to obtain ZnSe-based blue-violet quantum dots.

[0053] Comparative Example 2

[0054] A method for preparing ZnSe-based blue-violet quantum dots is basically the same as that of Example 2, except that the T°C of this comparative example is 300°C.

[0055] Comparative Example 3

[0056] A method for preparing ZnSe-based blue-violet quantum dots comprises the following steps:

[0057] Step 1, placing an oleic acid-zinc solution (8 mL) at 150°C in a reaction bottle, slowly injecting a Top-Se solution at room temperature of 20~25°C into the oleic acid-zinc solution (the Top-Se solution is obtained by dissolving 2 mmol Se powder in 2 mL trioctylphosphine at room temperature) to obtain a mixed solution, taking 0.5 mL of the mixed solution every 5 minutes to monitor the fluorescence characteristics, and when the fluorescence emission peak of the mixed solution is at 451 nm, heating the mixed solution to 220°C to obtain a ZnSe crystal nucleus solution, adding an oleic acid-zinc solution (9 mL) at 150°C and octanethiol (0.9 mL) at room temperature of 20~25°C to the ZnSe crystal nucleus solution at 220°C, and keeping the mixture at 220°C for 30 minutes to obtain a ZnSe / ZnS quantum dot solution, wherein the method for obtaining the oleic acid-zinc solution comprises: adding zinc oxide (1.562 g, 19.19 mmol), oleic acid (18 mL) and octadecene (45 The mixture was placed in a three-necked flask and mixed, heated to 120°C under an argon protective atmosphere, then heated at 120°C under vacuum for 30 min, then heated to 310°C under an argon protective atmosphere and kept warm for 10 min to obtain a colorless clear liquid, which was then cooled to 150°C to obtain an oleic acid-zinc solution.

[0058] Step 2, cooling the ZnSe / ZnS quantum dot solution at 220°C to 190°C, adding 3 mL of oleylamine-zinc solution, 4 mL of oleylamine-sulfur solution (the oleylamine-sulfur solution is obtained by dissolving sulfur powder in oleylamine at room temperature, wherein 15 mg of sulfur powder is uniformly dispersed per 1 mL of oleylamine) and a mixed solution of 21 mL of octadecene to the ZnSe / ZnS quantum dot solution at 190°C, injecting 4 mL of oleic acid therein, and keeping the temperature at 190°C for 3 minutes to obtain a ZnSe / ZnS / ZnS quantum dot solution, wherein the method for obtaining the oleylamine-zinc solution comprises: mixing zinc acetate (2.048 g, 11.16 mmol) and oleylamine (40 mL) in a three-necked flask, heating to 120°C in a vacuum atmosphere, obtaining a colorless and clear liquid as the oleylamine-zinc solution, and then cooling to room temperature.

[0059] Step 3, cooling the ZnSe / ZnS / ZnS quantum dot solution at 190° C. to room temperature, adding an excess of a mixture of acetone and hexane (the ratio of acetone to hexane is 2:1 by volume) and centrifuging to purify the ZnSe / ZnS / ZnS quantum dot solution to obtain ZnSe-based blue-violet quantum dots.

[0060] Figure 1 HRTEM images, where (a) is the ZnSe-based blue-violet quantum dots prepared in Comparative Example 1, and (b) is the ZnSe-based blue-violet quantum dots prepared in Example 2. Figure 1 It can be seen that the particle size of the ZnSe-based blue-violet light quantum dots prepared in Comparative Example 1 is 5nm, and the particle size of the ZnSe-based blue-violet light quantum dots prepared in Example 2 is 7nm, and the particles are evenly dispersed. Since the thickness of a layer of ZnS shell is about 0.6nm, its particle size indirectly indicates that the ZnSe quantum dot crystal core is coated with three layers of ZnS shell, namely, one layer of first ZnS shell and two layers of second ZnS shell.

[0061] Figure 2 The XPS spectra of the ZnSe-based blue-violet quantum dots prepared in Example 2 are shown in Figure 2, where (a) is the Zn 2p spectrum, (b) is the Se 3d spectrum, and (c) is the S 2p spectrum. Figure 2 As shown, the XPS spectrum of the ZnSe-based blue-violet quantum dots prepared in Example 2 contains spin-orbit splitting peaks of Zn 2p, Se 3d and S 2p. In summary, it is shown that the ZnSe-based blue-violet quantum dots prepared in Example 2 are successfully prepared.

[0062] The fluorescence emission spectra of the ZnSe-based blue-violet quantum dots prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were tested. The relative fluorescence quantum yields are shown in Table 2. The ZnSe-based blue-violet quantum dots prepared in Comparative Example 3 have no fluorescence emission. The fluorescence emission spectra of the ZnSe-based blue-violet quantum dots prepared in Examples 1 to 7 and Comparative Examples 1 to 2 are shown in Table 2. Figure 3 and Figure 4 As shown by Figure 3 , Figure 4As shown in Table 2, under the excitation of 350nm wavelength, the emission wavelengths of the ZnSe-based blue-violet quantum dots prepared in Examples 1 to 7 and Comparative Examples 1 to 2 are all at 400 to 425nm to emit blue-violet light. In the range of N=1 to 3, as the number of second ZnS shells formed in each injection operation increases, the relative fluorescence emission intensity of the ZnSe-based blue-violet quantum dots increases. When N=5, the relative fluorescence emission intensity of the ZnSe-based blue-violet quantum dots decreases, but its relative fluorescence quantum yield is still at 80%; as the nucleation temperature (T℃) decreases from 300℃ to 220℃, the relative fluorescence emission intensity of the ZnSe-based blue-violet quantum dots decreases, but the relative fluorescence quantum yield is still at 80%. ℃, the relative fluorescence intensity of the ZnSe-based blue-violet light quantum dots is enhanced, while the ZnSe-based blue-violet light quantum dots prepared in Comparative Example 3 have no fluorescence emission, indicating that a high temperature in the range of 290~320℃ is still required in the traditional nucleation reaction; in the range of N=1~3, with the increase of the Zn element content in the second ZnS shell layer, the relative fluorescence intensity of the ZnSe-based blue-violet light quantum dots is also enhanced. Therefore, the relative fluorescence quantum yield of the ZnSe-based blue-violet light quantum dots prepared in Example 2 is the highest, which is 85%, and the half-width of the fluorescence emission peak is 20nm, with high monochromaticity.

[0063] Table 2

[0064]

[0065] The transient fluorescence spectrum of the ZnSe-based blue-violet quantum dots prepared in Examples 1-2 and Comparative Example 1 was tested. The test results are as follows: Figure 5 and Figure 6 As shown, the transient fluorescence spectrum is fitted by the three-exponential function formula to obtain the fluorescence lifetime of each ZnSe-based blue-violet quantum dot. Compared with the ZnSe-based blue-violet quantum dots prepared in Comparative Example 1, with the coating of the first ZnS shell layer, the fluorescence lifetime of the ZnSe-based blue-violet quantum dots prepared in Example 1 is extended from 2.63ns to 25.09ns, indicating that the first ZnS shell layer formed by the second Zn precursor solution improves the surface defects and surface oxidation of the ZnSe quantum dot crystal nucleus, thereby extending its fluorescence lifetime. The fluorescence lifetime of the ZnSe-based blue-violet quantum dots prepared in Example 2 is 33.53ns. Combined with Table 2, it is further explained that the second ZnS shell layer formed by the third Zn precursor solution further passivates the surface defect state of the ZnSe quantum dot crystal nucleus, thereby improving the relative fluorescence quantum yield and luminescence efficiency of the ZnSe-based blue-violet quantum dots.

[0066] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for preparing ZnSe-based blue-violet quantum dots, characterized in that: The following steps are involved: Step 1, uniformly mixing a first Zn source and a first non-coordinating solvent, keeping the mixture at 100-150° C. for 5-20 minutes, and then naturally cooling the mixture to 50-60° C. to obtain a first Zn precursor solution, heating the first Zn precursor solution at 50-60° C. to 220° C. and keeping the mixture at 5-20 minutes, and then injecting a Se precursor solution at 20-25° C., and keeping the mixture at 220° C. for 5-30 minutes to obtain a ZnSe quantum dot nucleus solution, wherein the Se precursor solution is uniformly mixed with a Se source, dodecanethiol, and a second non-coordinating solvent, and the ratio of the Se element in the Se precursor solution to the Zn element in the first Zn precursor solution is (0.3-0.6):(1-3) in terms of the amount of the substance. Step 2, injecting a second Zn precursor solution at 50-60°C into a ZnSe quantum dot nucleus solution at 100-130°C, then heating to 140-170°C, then injecting a first coordination solvent and keeping the temperature at 140-170°C for 5-30 minutes to obtain a ZnSe / 1-Layer ZnS quantum dot solution, wherein the method for preparing the second Zn precursor solution comprises: uniformly mixing a second Zn source, a second coordination solvent and a third non-coordinating solvent, keeping the temperature at 70-120°C for 5-10 minutes, and then naturally cooling the temperature to 50-60°C to obtain a second Zn precursor solution, wherein the ratio of the Zn element in the first Zn precursor solution to the Zn element in the second Zn precursor solution is 1:(0.3-0.7) in terms of the amount of substance; Step 3, performing N-1 injection operations into the ZnSe / 1-Layer ZnS quantum dot solution at 100-130° C., N=3, to obtain a ZnSe / N-Layer ZnS quantum dot solution, each injection operation comprising: injecting a third Zn precursor solution at 20-25° C., then heating to 220-250° C., and keeping warm for 10-60 min, wherein when the number of injection operations is less than or equal to N-2 times, cooling to 100-130° C. after each injection operation; when the number of injection operations is equal to N-1 times, cooling to 20-25° C. using liquid nitrogen or liquid helium within 5-10 seconds after the N-1 injection operation; The third Zn precursor solution is obtained by uniformly mixing a third Zn source, an S source and a fourth non-coordinating solvent, and the ratio of the amount of the Zn element in the second Zn precursor solution to the volume of the third Zn precursor solution injected in each injection operation is (0.1-0.5): 1, the unit of the amount of the substance is mmol, and the unit of the volume is mL; Step 4, purifying the ZnSe / N-Layer ZnS quantum dot solution multiple times to obtain ZnSe-based blue-violet quantum dots; In step 1, the first Zn source is a mixture of one or both of zinc laurate and zinc stearate, the first non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane, and the second non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane; In step 2, the second Zn source is zinc diethyldithiocarbamate, the first coordinating solvent is one of tributylphosphine and trioctylphosphine, the second coordinating solvent is one of n-octylamine and oleylamine, and the third non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane; In step 3, the third Zn source is one of zinc stearate, zinc acetate and zinc laurate, and the fourth non-coordinating solvent is a mixture of one or more of octadecene, hexadecene and hexadecane.

2. The preparation method according to claim 1, characterized in that: The Se source is Se powder, and the S source is a mixture of one or more of dodecanethiol, tert-dodecylthiol and octylthiol.

3. The preparation method according to claim 1, characterized in that: The ratio of the amount of Se element in the Se source, the volume of dodecanethiol and the volume of the second non-coordinating solvent is (0.3-0.6): (0.1-1): (5-12), the unit of the amount of Se element is mmol, and the unit of the volume is mL.

4. The preparation method according to claim 1, characterized in that: The ratio of the amount of the Zn element in the first Zn source to the volume of the first non-coordinating solvent is (1-3): (3-10), the unit of the amount of the substance is mmol, and the unit of the volume is mL.

5. The preparation method according to claim 1, characterized in that: The ratio of the amount of substance of the Zn element in the second Zn source, the volume of the second coordinating solvent and the volume of the third non-coordinating solvent is (0.1-0.5): (0.5-2): (3-7), the unit of the amount of substance is mmol, and the unit of the volume is mL.

6. The preparation method according to claim 1, characterized in that: In terms of volume fractions, the ratio of the first coordinating solvent to the second coordinating solvent is (1-3): (2-5).

7. The preparation method according to claim 1, characterized in that: The ratio of the amount of Zn element in the third Zn source, the volume of the S source and the volume of the fourth non-coordinating solvent is (0.3-0.6): (1-2): (5-10), the unit of the amount of Zn is mmol, and the unit of the volume is mL.

8. The preparation method according to claim 1, characterized in that: Each purification operation includes: mixing with a first organic solvent or a second organic solvent, centrifuging to obtain a precipitate, and dispersing the precipitate with n-hexane, wherein the first organic solvent is a mixture of at least two of ethanol, isopropanol and acetone, and the second organic solvent is a mixture of at least two of methanol, octane and acetone.

9. The preparation method according to claim 8, characterized in that: When the first organic solvent is used for purification, the ratio of the ZnSe / N-Layer ZnS quantum dot solution to the first organic solvent used for purification is (1-3):(2-7) by volume.

10. The preparation method according to claim 8, characterized in that: When the second organic solvent is used for purification, the ratio of the ZnSe / N-Layer ZnS quantum dot solution to the second organic solvent used for purification is (1-3):(3-6) by volume.

Images