Quantum dot and preparation method thereof

Abstract

The invention provides a quantum dot and a preparation method thereof. The quantum dot comprises an AgInGaS core and an AgInGaS shell, the fluorescence half-peak width of the quantum dot is smaller than 40 nm, the fluorescence quantum yield is larger than or equal to 70%, the Ga / In molar ratio in the AgInGaS core is smaller than the Ga / In molar ratio in the AgInGaS shell, the core-shell lattice difference is reduced through the structure, and high quantum yield and narrow fluorescence half-peak width can be achieved.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum dot technology, and in particular to a quantum dot and a preparation method thereof. Background Art

[0002] Among all nanomaterials, semiconductor colloidal quantum dots (CQDs) have attracted widespread attention in the scientific community for their exceptional optical properties, such as high fluorescence quantum yield, wide absorption bandwidth, narrow emission peak, and excellent optical stability. Quantum dot research has become a hot topic in the fields of biomarkers and imaging, light-emitting diodes, and lasers. In particular, in displays (e.g., quantum dot televisions), CQDs offer a wider color gamut and higher color resolution, and have already found practical application. As CQD technology transitions from scientific research to practical applications, concerns are growing about the risks posed by cadmium-containing CQDs to human health and the environment. To this end, the European Union has introduced regulations requiring cadmium content in consumer electronics to be less than 100 ppm. Consequently, the development of high-performance CQDs, particularly InP-based CQDs, has become a research hotspot in both industry and academia. However, InP-based CQDs have relatively low blue light absorption, making them difficult to apply to display applications requiring high blue light absorption, such as AR / VR. Compared to InP-based CQDs, AgInGaS quaternary alloy CQDs exhibit higher blue light absorption and have garnered considerable attention in recent years. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a quantum dot and a preparation method thereof to improve the optical parameters of AgInGaS / AgInGaS quantum dots, such as quantum yield and fluorescence half-maximum width.

[0004] According to a first aspect of the present disclosure, a quantum dot is provided, comprising an AgInGaS core and an AgInGaS shell, wherein the fluorescence half-width of the quantum dot is less than 40 nm, the fluorescence quantum yield is greater than or equal to 70%, and the Ga / In molar ratio in the AgInGaS core is less than the Ga / In molar ratio in the AgInGaS shell.

[0005] Optionally, the quantum dot further includes an InGaS shell outside the AgInGaS shell, and the Ga / In molar ratio in the AgInGaS shell is less than the Ga / In molar ratio in the InGaS shell; preferably, the Ga / In molar ratio in the AgInGaS core is 0.1~0.5, and the Ga / In molar ratio in the AgInGaS shell is 0.5~2; preferably, the Ga / In molar ratio in the InGaS shell is 0.5~2; preferably, the quantum dot further includes a Ga2S3 shell outside the InGaS shell.

[0006] According to a second aspect of the present disclosure, a method for preparing the above-mentioned quantum dots is provided, the method comprising:

[0007] S1: preparing a mixture containing a first indium precursor, a fatty acid, a first gallium precursor, and a non-coordinating solvent in a container; at least one of the first indium precursor and the first gallium precursor does not contain sulfur;

[0008] S2: When the mixture is at a first temperature, injecting a first sulfur precursor into the container and reacting for a first time;

[0009] S3: Continue injecting the first silver precursor into the container and react for a second time;

[0010] S4: injecting a second sulfur precursor into the container at a second temperature and reacting for a third time; the first temperature is less than the second temperature;

[0011] S5: adding a second indium precursor to the container at a third temperature, and dropwise adding a solution containing Ag2S nanoparticles or a solution containing Ag2S nanoparticles and In2S3 nanoparticles; or dropwise adding a solution containing Ag2S nanoparticles and In2S3 nanoparticles to the container at the third temperature, and obtaining AgInGaS / AgInGaS quantum dots after reaction, wherein the size of the nanoparticles is less than 1 nm; or

[0012] S1′: preparing a mixture containing a first indium precursor, a first aliphatic amine, and a first gallium precursor in a container, wherein the first indium precursor and the first gallium precursor both contain sulfur;

[0013] S2': when the mixture is at the first temperature, injecting a first silver precursor into the container and reacting for a second time;

[0014] S3': reacting at the second temperature for a third time; the first temperature < the second temperature;

[0015] S4': at a third temperature, adding a second indium precursor to the container, and dropwise adding a solution containing Ag2S nanoparticles, or a solution containing Ag2S nanoparticles and In2S3 nanoparticles, to obtain AgInGaS / AgInGaS quantum dots after reaction, wherein the size of the nanoparticles is less than 1 nm.

[0016] Optionally, the molar ratio of gallium element to indium element in the mixture is greater than or equal to 5:1; after step S5, step S6 is also included: at a fourth temperature, a solution containing In2S3 nanoparticles is added dropwise to the container to obtain AgInGaS / AgInGaS / InGaS quantum dots after reaction; preferably, the fourth temperature is 150-210°C.

[0017] Optionally, after step S6, step S7 is further included: adding a second gallium precursor to the container, adding a third sulfur precursor dropwise, and reacting at a fifth temperature to obtain AgInGaS / AgInGaS / InGaS / Ga2S3 quantum dots; preferably, the fifth temperature is 250-300°C.

[0018] Optionally, the molar ratio of gallium to indium in the mixture is less than 5:1, and S5 further comprises dropwise adding a solution containing the first fatty acid gallium; and S4' further comprises dropwise adding a solution containing the first fatty acid gallium.

[0019] Optionally, after step S5, step S6 is further included: at a fourth temperature, adding In2S3 nanoparticles and a second fatty acid gallium solution into the container to obtain AgInGaS / AgInGaS / InGaS quantum dots after reaction; preferably, the fourth temperature is 150-210°C.

[0020] Optionally, after step S4', the process further includes S5': adding a third indium precursor containing the S element to the container at a fourth temperature, and obtaining AgInGaS / AgInGaS / InGaS quantum dots after the reaction; preferably, after step S5', the process further includes S6': adding a second gallium precursor to the container, dropwise adding a third sulfur precursor, and obtaining AgInGaS / AgInGaS / InGaS / Ga2S3 quantum dots after the reaction at a fifth temperature; preferably, the fourth temperature is 150-210°C; preferably, the fifth temperature is 250-300°C.

[0021] Optionally, the method for preparing the solution containing Ag2S nanoparticles includes reacting a second silver precursor and a fourth sulfur precursor in a second fatty amine at 40-70°C for a certain time; preferably, the method for preparing the solution containing In2S3 nanoparticles includes reacting a fourth indium precursor, the fatty acid, the non-coordinating solvent and the sulfur-fatty amine at 150-200°C for a certain time.

[0022] Optionally, the first time is 1 to 10 minutes; the second time is 5 to 10 minutes; preferably, the third time is 5 to 30 minutes.

[0023] Optionally, the first temperature is 100-150°C, the second temperature is 150-220°C; and the third temperature is 150-220°C.

[0024] Optionally, S1 includes: mixing the first indium precursor, the fatty acid, the first gallium precursor and the non-coordinating solvent in the container, heating until dissolved, to obtain the mixture; at least one of the first indium precursor and the first gallium precursor is a corresponding fatty acid metal salt; preferably, the fatty acid is oleic acid or a saturated fatty acid containing 8 to 18 carbon atoms.

[0025] Optionally, the first and second sulfur precursors are selected from one or more of 1-octadecene, trialkylphosphinesulfide, sulfur-fatty amine, thiourea and mercaptan.

[0026] Optionally, the first indium precursor and the second indium precursor are independently selected from one or more of fatty acid indium with 2 to 18 carbon atoms, indium halide-fatty amine mixed solution, halogenated indium bis(diethyldithiocarbamate), or indium diethyldithiocarbamate.

[0027] Optionally, the first gallium precursor is selected from one or more of gallium aliphatic acid with 2 to 18 carbon atoms, gallium acetylacetonate-fatty amine, gallium halide-fatty amine solution, gallium halogenate bis(diethyldithiocarbamate), or gallium diethyldithiocarbamate.

[0028] Optionally, the first fatty amine is selected from oleylamine or a saturated fatty amine containing 8 to 18 carbon atoms.

[0029] Optionally, the first silver precursor is selected from one or more of fatty acid silver with 2 to 18 carbon atoms, the fatty acid silver-fatty amine mixed solution, silver halide-fatty amine mixed solution and AgS nanoparticle solution.

[0030] Optionally, the molar ratio between the silver element of the first silver precursor and the indium element of the first indium precursor is (3:1) to (1:3).

[0031] By applying the above technical solution, the structure reduces the core-shell lattice difference and can achieve high quantum yield and narrow fluorescence half-width. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are intended to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the accompanying drawings:

[0033] Figure 1 This is the UV-visible absorption spectrum of Example 1 of the present disclosure.

[0034] Figure 2 is the fluorescence emission spectrum of Example 1 of the present disclosure. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0036] It should be noted that the terms "first", "second" etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described herein. In addition, the terms "comprise" and "have" and their any distortion are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units need not be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or equipment. Below "optional" material includes that this material may or may not exist.

[0037] The inventors believe that the traditional method for synthesizing AgInGaS quaternary alloy quantum dots is to inject an S precursor into Ag, In, and Ga precursors at a certain temperature. This will cause the composition of the AgInGaS quaternary alloy quantum dots to be non-uniform, and nanoparticles such as Ag2S and AgInS2 to coexist. In addition, the fluorescence quantum yield of the AgInGaS alloy quantum dots themselves is low, and the usual method is to coat the surface of the core quantum dots with a Ga2S3 shell. The traditional coating method is to synthesize the AgInGaS quantum dots, purify them, add them to the gallium precursor, and then increase the temperature, inject a sulfur precursor, and coat the shell. However, due to the large lattice mismatch between Ga2S3 and the core, internal defects will be caused, resulting in a low fluorescence quantum yield of the core-shell quantum dots.

[0038] Based on the above analysis, according to the first aspect of the present disclosure, a quantum dot is provided, comprising an AgInGaS core and an AgInGaS shell. The quantum dot has a fluorescence half-width less than 40 nm, a fluorescence quantum yield greater than or equal to 70%, and a Ga / In molar ratio in the AgInGaS core less than that in the AgInGaS shell. This structure avoids the lattice mismatch between the conventional Ga2S3 shell and the AgInGaS core, and the valence band of the AgInGaS core is higher than that of the AgInGaS shell, while the conduction band of the AgInGaS core is lower than that of the AgInGaS shell, thereby improving fluorescence efficiency.

[0039] In some embodiments, the Ga / In molar ratio in the AgInGaS core is 0.1-0.5, and the Ga / In molar ratio in the AgInGaS shell is 0.5-2.

[0040] In some embodiments, the quantum dot further includes an InGaS shell outside an AgInGaS shell. The Ga / In molar ratio in the AgInGaS shell is lower than the Ga / In molar ratio in the InGaS shell. The InGaS shell has a wide energy band, which can inhibit exciton escaping and improve the stability of the quantum dot. In some embodiments, the Ga / In molar ratio in the InGaS shell is 0.5 to 2.

[0041] In some embodiments, the quantum dots further include a Ga2S3 shell outside the InGaS shell to improve the stability of the quantum dots.

[0042] In some embodiments, the fluorescence half-width of the quantum dot is greater than or equal to 30 nm. In some embodiments, the fluorescence quantum yield of the quantum dot is less than or equal to 99%. In some embodiments, the fluorescence quantum yield of the quantum dot is 70-85% or 80-90%. In some embodiments, the fluorescence peak of the quantum dot is 500-600 nm. In some embodiments, the fluorescence peak of the quantum dot is 520-570 nm.

[0043] In some embodiments, the average particle size of the quantum dots is 7 to 15 nm.

[0044] According to the second aspect of the present disclosure, a method for preparing the quantum dots proposed in the present application is provided, the method comprising:

[0045] S1: preparing a mixture containing a first indium precursor, a fatty acid, a first gallium precursor, and a non-coordinating solvent in a container; at least one of the first indium precursor and the first gallium precursor does not contain sulfur;

[0046] S2: When the mixture is at a first temperature, injecting a first sulfur precursor into the container and reacting for a first time;

[0047] S3: Continue injecting the first silver precursor into the container and react for a second time;

[0048] S4: injecting a second sulfur precursor into the container at the second temperature and reacting for a third time; the first temperature is less than the second temperature;

[0049] S5: adding a second indium precursor to the container at a third temperature, and dropwise adding a solution containing Ag2S nanoparticles or a solution containing Ag2S nanoparticles and In2S3 nanoparticles; or dropwise adding a solution containing Ag2S nanoparticles and In2S3 nanoparticles to the container at the third temperature, and obtaining AgInGaS / AgInGaS quantum dots after reaction, wherein the nanoparticle size is less than 1 nm; or

[0050] S1′: preparing a mixture containing a first indium precursor, a first fatty amine, and a first gallium precursor in a container, wherein the first indium precursor and the first gallium precursor both contain sulfur;

[0051] S2': when the mixture is at the first temperature, injecting the first silver precursor into the container and reacting for a second time;

[0052] S3': react at the second temperature for a third time; the first temperature < the second temperature;

[0053] S4': at a third temperature, a second indium precursor is added to the container, and a solution containing Ag2S nanoparticles is added dropwise, or a solution containing Ag2S nanoparticles and In2S3 nanoparticles is added dropwise, to obtain AgInGaS / AgInGaS quantum dots after reaction, and the size of the nanoparticles is less than 1 nm.

[0054] According to the inventors' understanding (this application is not limited by this understanding or theory), S1-S2 is to form In2S3, avoiding the direct addition of silver precursors to form Ag nanoparticles. S3 forms AgInS2, and S4 forms AgInGaS at a higher second temperature. Considering that silver precursors of general compounds are easily decomposed into Ag nanoparticles at high temperatures, S5 uses the dropwise addition of Ag2S nanoparticles with a size less than 1nm as the silver source. Similarly, when the second indium precursor is insufficient, In2S3 can be added as the indium source. S1' to S4' can be explained with reference to the above principles.

[0055] It should be noted that the above-mentioned injection at a certain temperature does not refer to the temperature of the added substance, but refers to the temperature of the contents in the reaction container before the addition. In S5, if the second indium precursor is not added, a solution of In2S3 nanoparticles can be added as the indium source.

[0056] In some embodiments, the method of adding the solution containing Ag2S nanoparticles and In2S3 nanoparticles includes adding a mixed solution containing the two nanoparticles, and may also include adding the solution containing Ag2S nanoparticles and the solution containing In2S3 nanoparticles separately at the same time.

[0057] In some embodiments, the molar ratio of gallium to indium in the mixture is greater than or equal to 5:1. Following step S5, the method further includes step S6: adding a solution containing In2S3 nanoparticles to a container at a fourth temperature to react to produce AgInGaS / AgInGaS / InGaS quantum dots. In some embodiments, the fourth temperature is 150-210°C. Following step S6, the method further includes step S7: adding a second gallium precursor to the container and adding a third sulfur precursor to react at a fifth temperature to produce AgInGaS / AgInGaS / InGaS / Ga2S3 quantum dots. In some embodiments, the fifth temperature is 250-300°C.

[0058] In some embodiments, the molar ratio of gallium to indium in the mixture is less than 5:1, and step S5 further includes dropwise adding a solution of a first fatty acid gallium. That is, S5: at a third temperature, adding a second indium precursor to the container, and dropwise adding a solution containing Ag2S nanoparticles and the first fatty acid gallium, or a solution containing Ag2S nanoparticles, the first fatty acid gallium, and In2S3 nanoparticles; or at a third temperature, dropwise adding a solution containing Ag2S nanoparticles, the first fatty acid gallium, and In2S3 nanoparticles to the container.

[0059] In some embodiments, after step S5, the method further includes step S6: adding a solution containing In2S3 nanoparticles and a second fatty acid gallium solution to a container at a fourth temperature to react and obtain AgInGaS / AgInGaS / InGaS quantum dots. In some embodiments, the fourth temperature is 150-210°C.

[0060] In some embodiments, the first gallium fatty acid and the second gallium fatty acid are independently selected from gallium fatty acids having 2 to 18 carbon atoms.

[0061] In some embodiments, the addition of the second indium precursor and the start of dropwise addition of the solution containing nanoparticles in step S5 occur simultaneously, or the second indium precursor is added first and then the start of dropwise addition of the solution containing nanoparticles.

[0062] In some embodiments, the molar ratio of gallium to indium in the mixture is less than 5:1. Step S4′ further includes dropwise adding a first fatty acid gallium solution, that is, dropwise adding a solution containing Ag2S nanoparticles and the first fatty acid gallium, or dropwise adding a solution containing Ag2S nanoparticles, the first fatty acid gallium, and In2S3 nanoparticles.

[0063] In some embodiments, after step S4', the process further includes step S5': adding a third indium precursor containing the element S to the container at a fourth temperature, reacting to produce AgInGaS / AgInGaS / InGaS quantum dots. In some embodiments, after step S5', the process further includes step S6': adding a second gallium precursor to the container, dropwise adding a third sulfur precursor, and reacting at a fifth temperature to produce AgInGaS / AgInGaS / InGaS / Ga2S3 quantum dots. In some embodiments, the fourth temperature is 150-210°C. In some embodiments, the fifth temperature is 250-300°C.

[0064] In some embodiments, a method for preparing a solution containing Ag2S nanoparticles comprises reacting a second silver precursor and a fourth sulfur precursor in a second fatty amine at 40-70°C for a predetermined time. In some specific embodiments, a silver halide-fatty amine (i.e., the second silver precursor) and oleylamine are mixed and heated to a fixed temperature of 40-70°C, and then the second fatty amine is added and reacted at the fixed temperature for a predetermined time to obtain a solution containing Ag2S nanoparticles.

[0065] In some embodiments, the preparation of the solution containing Ag2S nanoparticles and a first fatty acid gallium comprises: after the Ag2S nanoparticle solution is prepared, adding fatty gallium-oleylamine and mixing.

[0066] In some embodiments, a method for preparing a solution containing In2S3 nanoparticles comprises reacting a fourth indium precursor, a fatty acid, a non-coordinating solvent, and a sulfur-fatty amine at 150-200°C for a predetermined time. In some embodiments, a method for preparing a solution containing In2S3 nanoparticles comprises reacting indium acetate, oleic acid, and a non-coordinating solvent, degassing the solvent, and then adding a sulfur-fatty amine and reacting the mixture at 150-200°C for a predetermined time.

[0067] In some embodiments, the method for preparing a solution containing Ag2S nanoparticles and In2S3 nanoparticles includes mixing the solution containing Ag2S nanoparticles and the solution containing In2S3 nanoparticles. Alternatively, the solution containing Ag2S nanoparticles and the solution containing In2S3 nanoparticles may be added separately without mixing as described above.

[0068] The preparation of the solution containing In2S3 nanoparticles and the first fatty acid gallium includes: after the aforementioned In2S3 nanoparticle solution is prepared, fatty gallium-oleylamine is added and mixed.

[0069] The reaction time and reaction temperature for preparing the nanoparticles must be comprehensively considered to ensure that the size of the nanoparticles is less than 1 nm.

[0070] The dispersant in the solution containing nanoparticles can be one or more of aliphatic amine and a non-coordinating solvent.

[0071] In some embodiments, the second time is greater than or equal to the first time. In some embodiments, the first time is 1 to 10 minutes. In some embodiments, the second time is 5 to 10 minutes. In some embodiments, the third time is 5 to 30 minutes. In some embodiments, the first time is 1 to 10 minutes; the second time is 5 to 10 minutes; and the third time is 5 to 30 minutes.

[0072] In some embodiments, the first temperature is 100-150°C. In some embodiments, the second temperature is 150-220°C. In some embodiments, the third temperature is 250-300°C. In some embodiments, both the second and third temperatures are greater than or equal to 200°C. In some embodiments, the first temperature is 100-150°C, the second temperature is 150-220°C, and the third temperature is 150-220°C.

[0073] In some embodiments, step S1 includes: mixing a first indium precursor, a fatty acid, a first gallium precursor, and a non-coordinating solvent in a container, heating until dissolved, and obtaining a mixture; at least one of the first indium precursor and the first gallium precursor is a corresponding fatty acid metal salt; preferably, the fatty acid is oleic acid or a saturated fatty acid containing 8 to 18 carbon atoms.

[0074] In some embodiments, the mixture in step S1 may further comprise a fatty amine.

[0075] In some embodiments, the mixture in step S1 ′ may further comprise a non-coordinating solvent.

[0076] In some embodiments, the first, second, third, and fourth sulfur precursors are independently selected from one or more of 1-octadecene thiosulfide, trialkylphosphine thiosulfide, sulfur-fatty amine, thiourea, and mercaptan. "1-octadecene thiosulfide" and "sulfur-fatty amine" refer to dispersions of sulfur in 1-octadecene and fatty amine, respectively. In some embodiments, the second sulfur precursor is different from the first sulfur precursor.

[0077] In some embodiments, the first, second, third, and fourth indium precursors are independently selected from one or more of an indium fatty acid having 2 to 18 carbon atoms, an indium halide-fatty amine mixed solution, an indium halogenated bisdiethyldithiocarbamate (e.g., InCl(DDTC)2), or an indium diethyldithiocarbamate. In some embodiments, the first indium precursor comprises two indium-containing compounds. The fluorescence peak position of the quantum dots can be controlled by adjusting the carbon chain length of the indium fatty acid. "Indium halide-oleylamine" refers to a dispersion of indium halide in oleylamine. "Gallium halide-oleylamine" and "Gadium acetylacetonate-oleylamine" will be explained below with reference to this.

[0078] In some embodiments, the first gallium precursor is selected from one or more of a gallium fatty acid with 2 to 18 carbon atoms, a gallium acetylacetonate-oleylamine solution, a gallium halide-oleylamine mixed solution, a gallium halide bis(diethyldithiocarbamate) (e.g., GaCl(DDTC)2), or gallium diethyldithiocarbamate. The fluorescence peak position of the quantum dots is controlled by adjusting the carbon chain length of the gallium fatty acid.

[0079] In some embodiments, the first gallium precursor and the second gallium precursor are independently selected from one or more of a gallium aliphatic with 2 to 18 carbon atoms, gallium acetylacetonate-fatty amine, a gallium halide-fatty amine solution, a gallium halide bis(diethyldithiocarbamate), or a gallium diethyldithiocarbamate.

[0080] In some embodiments, the first and second fatty amines are independently selected from oleylamine or saturated fatty amines containing 8 to 18 carbon atoms. In some embodiments, the fatty amine used in the above reaction or the fatty amine used for dispersion in the precursors (sulfur precursor, indium precursor, silver precursor, and gallium precursor) is selected from oleylamine or saturated fatty amines containing 8 to 18 carbon atoms. Fatty amines can form complexing reactions with metal salts in the precursors, increasing the activity of the precursors and promoting the reaction.

[0081] In some embodiments, in the reaction with gallium diethyldithiocarbamate Ga(DDTC)3 or indium diethyldithiocarbamate In(DDTC)3 as precursor, aliphatic amine can promote the formation of DDTC. - decomposition.

[0082] In some embodiments, the first silver precursor and the second silver precursor are independently selected from one or more of fatty acid silver with 2 to 18 carbon atoms, fatty acid silver-fatty amine mixed solution, silver halide-fatty amine mixed solution and silver sulfide nanoparticle solution.

[0083] In some embodiments, the non-coordinating solvent is a common solvent in the art, such as 1-octadecene, alkane, petrolatum, and the like.

[0084] In some embodiments, the amount ratio of the second sulfur precursor in S4 to the first sulfur precursor in S2 is 5:1 to 1:5.

[0085] In some embodiments, the amount ratio of the first gallium precursor in S1 to the first sulfur precursor in S2 is 5:1 to 20:1.

[0086] In some embodiments, in S7 or S6', the molar ratio of the sulfur element of the third sulfur precursor to all sulfur elements added in the previous steps (S1 to S6, or S1' to S5') is 1:5 to 5:1.

[0087] In some embodiments, the heating in S7 or S6 ' (the fourth temperature is less than the fifth temperature) can be linear, such as the fourth temperature is the temperature of a gradually heated interval, the fifth temperature is the temperature of a gradually heated interval, and the heating starts to calculate the reaction time. In some embodiments, the heating in S7 or S6 ' can be multi-stage, such as the fourth temperature and the fifth temperature are both a constant temperature, and then the reaction time is started after the constant temperature is reached. In some embodiments, when the fourth temperature and the fifth temperature in S7 or S6 ' are both a constant temperature, it is also possible to introduce a fourth time of reaction at the fourth temperature, a fifth time of reaction at the fifth temperature, etc., that is, the number of steps of the temperature curve can be greater than 2.

[0088] In some embodiments, the number of carbon atoms in the fatty acid indium or fatty acid gallium is 2-18.

[0089] In some embodiments, the heating to dissolve in S1 further includes exhausting gas. In some embodiments, the molar ratio of the amount of the fatty acid in S1 to the sum of the amount of the In element of the first indium precursor and the Ga element of the first gallium precursor is greater than 3:1.

[0090] In some embodiments, the fatty acid in S1 is oleic acid or a saturated fatty acid containing 8 to 18 carbon atoms. The fluorescence peak position of the quantum dots can be controlled by adjusting the C chain length of the fatty acid.

[0091] Changing the ratio of silver to indium can adjust the fluorescence peak position. In some embodiments, the molar ratio of the silver element in the first silver precursor to the indium element in the first indium precursor is (3:1) to (1:3).

[0092] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0093] Synthesis of Ag2S nanoparticles solution:

[0094] Take 1mmol silver chloride and 5mL oleylamine in a 25mL three-necked flask, raise the temperature to 50℃, inject 5mL 0.2mmol S-oleylamine solution (1mmol S dissolved in 5mL oleylamine), control the temperature at 50℃ and react for 10min, then stop the reaction.

[0095] Synthesis of Ag2S nanoparticles-gallium oleate solution: Take 1mmol silver chloride and 5mL oleylamine in a 25mL three-necked flask, raise the temperature to 50℃, inject 5mL 0.2mmol / mL S-oleylamine solution (1mmol S dissolved in 5mL oleylamine), control the temperature at 50℃ and react for 10min, add 10mL 0.5mmol / mL gallium oleate-oleylamine solution, stop the reaction and set aside.

[0096] Synthesis of In2S3 nanoparticles solution:

[0097] Take 1mmol indium acetate, 5mmol oleic acid, and 5mL ODE in a 25mL three-necked flask, raise the temperature to 180℃, introduce nitrogen to exhaust for 30min, cool to 150℃, inject 5mL 0.2mmol S-oleylamine solution (1mmol S dissolved in 5mL oleylamine), react for 10min, stop the reaction and set aside.

[0098] Synthesis of In2S3 nanoparticles-gallium oleate solution:

[0099] Take 1mmol indium acetate, 5mmol oleic acid, and 5mL ODE in a 25mL three-necked flask, raise the temperature to 180℃, introduce nitrogen to exhaust for 30min, cool to 150℃, inject 5mL 0.2mmol S-oleylamine solution (1mmol S is dissolved in 5mL oleylamine), react for 10min, add 10mL 0.5mmol / mL gallium oleate-oleylamine solution to stop the reaction and set aside.

[0100] Example 1:

[0101] Weigh 0.4 mmol of indium chloride, 0.1 mmol of In(DDTC)3, 0.6 mol of Ga(DDTC)3, and 40 mL of oleylamine in a 250 mL three-necked flask, raise the temperature to 130°C, inject 0.5 mmol of silver acetate-oleylamine solution (0.5 mmol of silver acetate is dissolved in 2 mL of oleylamine), react for 10 min, raise the temperature to 200°C and react for 20 min, add 1 mL of 0.2 mmol / mL indium oleate-ODE solution, add 2 mL of Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4 mL / h), then add 2 mL of In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4 mL / h), then add 5 mL of 0.2 mmol / mL gallium oleate-ODE solution, raise the temperature to 280°C, inject 0.5 mL of 2 mmol / mL S-TOP solution, react for 30 min, and stop the reaction.

[0102] Example 2:

[0103] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0104] Example 3:

[0105] Weigh 0.5mmol indium acetate, 5mmol gallium acetylacetonate, 20mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0106] Example 4:

[0107] Weigh 0.4 mmol of indium chloride, 0.1 mmol of In(DDTC)3, 0.6 mol of Ga(DDTC)3, and 40 mL of oleylamine in a 250 mL three-necked flask, raise the temperature to 130°C, inject 0.5 mmol of silver acetate-oleylamine solution (0.5 mmol of silver acetate is dissolved in 2 mL of oleylamine), react for 10 min, raise the temperature to 200°C and react for 20 min, add 1 mL of 0.2 mmol / mL indium oleate-ODE solution, add 2 mL of Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4 mL / h), then inject 1 mL of In(DDTC)3-oleylamine suspension (drop rate 4 mL / h), then add 5 mL of 0.2 mmol / mL gallium oleate-ODE solution, raise the temperature to 280°C, inject 0.5 mL of 2 mmol / mL S-TOP solution, react for 30 min, and stop the reaction.

[0108] Example 5:

[0109] Weigh 0.5mmol indium acetate, 2.5mmol gallium acetylacetonate, 15mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate dissolved in 2mL oleylamine), and react.

[0110] 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticle solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticle solution dropwise (drop rate 4mL / h), then add 5mL 0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0111] Example 6:

[0112] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 1mmol silver acetate-oleylamine solution (1mmol silver acetate is dissolved in 4mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL0.2mmol / mL indium oleate-ODE solution, add 2mLAg2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL 0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0113] Example 7:

[0114] Weigh 0.5mmol indium chloride, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, 5ml oleylamine, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0115] Example 8:

[0116] Weigh 0.5mmol indium acetate, 0.3mmol gallium acetylacetonate, 0.3mmolGa(DDTC)3, 5mmol oleic acid, 20gODE, and 20ml oleylamine in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL 0.2mmol / mL gallium oleate-ODE solution was heated to 280℃, and 0.5mL 2mmol / mL S-TOP solution was injected. The reaction was allowed to proceed for 30min and then the reaction was stopped.

[0117] Example 9:

[0118] Weigh 0.2mmol indium acetate, 0.3mmol In(DDTC)3, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, 20g ODE, and 20ml oleylamine in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL 0.2mmol / mL gallium oleate-ODE solution was heated to 280℃, and 0.5mL 2mmol / mL S-TOP solution was injected. The reaction was allowed to proceed for 30min and then the reaction was stopped.

[0119] Example 10:

[0120] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL 0.2mmol / mL Ga(DDTC)3-oleylamine suspension, raise the temperature to 280℃, react for 30min, and stop the reaction.

[0121] Example 11:

[0122] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 1mmol S-oleylamine solution, react for 20min, add 1mL0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL 0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0123] Example 12

[0124] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), and then add 2mL In2S3 nanoparticles-gallium oleate solution (drop rate 4mL / h), then add 5mL0.2mmol / mL gallium oleate-ODE solution, increase the temperature to 280℃, inject 1mL of dodecylmercaptan, react for 30min, and stop the reaction.

[0125] Example 13

[0126] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 5mL 0.1mmol / ml S-ODE solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0127] Example 14:

[0128] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 5mL 0.1mmol / ml S-ODE solution, react for 5min, inject 0.5mmol silver chloride-oleylamine solution (0.5mmol silver chloride is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticles-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0129] Example 15:

[0130] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 5mL 0.1mmol / ml S-ODE solution, react for 5min, inject 0.5mmol silver chloride-oleylamine solution (0.5mmol silver chloride is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, and at the same time, add 2mL Ag2S nanoparticle-gallium oleate solution and 2mL In2S3 nanoparticle-gallium oleate solution (drop rate 4mL / h), then add 2mL In2S3 nanoparticle solution (drop rate 4mL / h), then add 5mL 0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution was added, and the reaction was continued for 30min, and then the reaction was stopped.

[0131] Example 16:

[0132] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 5mL Ag2S nanoparticle solution, react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, add 2mL Ag2S nanoparticle-gallium oleate solution dropwise (drop rate 4mL / h), then add 2mL In2S3 nanoparticle-gallium oleate solution dropwise (drop rate 4mL / h), then add 5mL0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0133] Comparative Example 1:

[0134] Take 0.5mmol silver acetate, 0.4mmol indium chloride, 0.1mmol In(DDTC)3, 0.6mmol Ga(DDTC)3, and 40mL oleylamine, and place them in a 100mL three-necked flask. Raise the temperature to 200℃, react for 20min, cool, purify with acetone and methanol, and dissolve in 5mL octane.

[0135] Weigh 0.2 mmol Ga(DDTC)3, 0.4 mmL gallium chloride, and 20 mL oleylamine into a 100 mL three-necked flask, raise the temperature to 180°C, add core quantum dots, introduce nitrogen to remove octane, raise the temperature to 280°C, react for 30 minutes, and stop the reaction.

[0136] Comparative Example 2:

[0137] Weigh 0.5mmol indium acetate, 0.6mmol gallium acetylacetonate, 5mmol oleic acid, and 40g ODE in a 250mL three-necked flask, raise the temperature to 180℃, exhaust for 30min, cool to 130℃, inject 0.5mmol S-oleylamine solution, react for 5min, inject 0.5mmol silver acetate-oleylamine solution (0.5mmol silver acetate is dissolved in 2mL oleylamine), react for 10min, raise the temperature to 200℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 20min, add 1mL 0.2mmol / mL indium oleate-ODE solution, 1mL0.2mmol / mL silver oleate-ODE solution, 1mL0.5mmol / ml gallium oleate solution, return to temperature, inject 0.5mmol S-oleylamine solution, react for 20min, then 1mL0.2mmol / mL indium oleate-ODE solution, 1mL 0.5mmol / ml-gallium oleate solution, return to temperature, inject 0.5mmol S-oleylamine solution, react for 20min, then add 5mL 0.2mmol / mL gallium oleate-ODE solution, raise the temperature to 280℃, inject 0.5mL 2mmol / mL S-TOP solution, react for 30min, and stop the reaction.

[0138] The quantum dot products obtained in each of the above examples were precipitated by adding ethanol, separated and purified, and dispersed in toluene solvent for integrating sphere testing. Table 1 shows the optical properties of the examples and comparative examples.

[0139] Table 1

[0140]

[0141]

[0142] It can be seen from Table 1 that the embodiment is superior to the comparative example in terms of fluorescence half-peak width and fluorescence quantum dot yield.

[0143] The foregoing description is merely a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure.

Claims

1. A quantum dot, characterized in that The quantum dots include an AgInGaS core and an AgInGaS shell, the fluorescence half-peak width of the quantum dots is less than 40nm, the fluorescence quantum yield is greater than or equal to 70%, and the Ga / In molar ratio in the AgInGaS core is less than the Ga / In molar ratio in the AgInGaS shell.

2. The quantum dot according to claim 1, characterized in that The quantum dot further includes an InGaS shell outside the AgInGaS shell, and the Ga / In molar ratio in the AgInGaS shell is less than the Ga / In molar ratio in the InGaS shell; preferably, the Ga / In molar ratio in the AgInGaS core is 0.1-0.5, and the Ga / In molar ratio in the AgInGaS shell is 0.5-2; preferably, the Ga / In molar ratio in the InGaS shell is 0.5-2; preferably, the quantum dot further includes a Ga2S3 shell outside the InGaS shell.

3. A method for preparing quantum dots according to claim 1 or 2, characterized in that: The preparation method comprises: S1: preparing a mixture containing a first indium precursor, a fatty acid, a first gallium precursor, and a non-coordinating solvent in a container; at least one of the first indium precursor and the first gallium precursor does not contain sulfur; S2: When the mixture is at a first temperature, injecting a first sulfur precursor into the container and reacting for a first time; S3: Continue injecting the first silver precursor into the container and react for a second time; S4: injecting a second sulfur precursor into the container at a second temperature and reacting for a third time; the first temperature is less than the second temperature; S5: adding a second indium precursor to the container at a third temperature, and dropwise adding a solution containing Ag2S nanoparticles or a solution containing Ag2S nanoparticles and In2S3 nanoparticles; or dropwise adding a solution containing Ag2S nanoparticles and In2S3 nanoparticles to the container at the third temperature, and obtaining AgInGaS / AgInGaS quantum dots after reaction, wherein the size of the nanoparticles is less than 1 nm; or S1′: preparing a mixture containing a first indium precursor, a first aliphatic amine, and a first gallium precursor in a container, wherein the first indium precursor and the first gallium precursor both contain sulfur; S2': when the mixture is at the first temperature, injecting a first silver precursor into the container and reacting for a second time; S3': reacting at the second temperature for a third time; the first temperature < the second temperature; S4': at a third temperature, adding a second indium precursor to the container, and dropwise adding a solution containing Ag2S nanoparticles, or a solution containing Ag2S nanoparticles and In2S3 nanoparticles, to obtain AgInGaS / AgInGaS quantum dots after reaction, wherein the size of the nanoparticles is less than 1 nm.

4. The method for preparing quantum dots according to claim 3, wherein: The molar ratio of gallium element to indium element in the mixture is greater than or equal to 5:1; after step S5, step S6 is also included: at a fourth temperature, a solution containing In2S3 nanoparticles is added dropwise to the container to obtain AgInGaS / AgInGaS / InGaS quantum dots after reaction; preferably, the fourth temperature is 150-210°C.

5. The method for preparing quantum dots according to claim 4, wherein: After step S6, step S7 is further included: adding a second gallium precursor into the container and dropwise adding a third sulfur precursor, and reacting at a fifth temperature to obtain AgInGaS / AgInGaS / InGaS / Ga2S3 quantum dots; preferably, the fifth temperature is 250-300°C.

6. The method for preparing quantum dots according to claim 3, wherein: The molar ratio of gallium to indium in the mixture is less than 5:

1. S5 further comprises dropwise adding a solution containing the first fatty acid gallium; S4' further comprises dropwise adding a solution containing the first fatty acid gallium.

7. The method for preparing quantum dots according to claim 6, wherein: After step S5, the method further includes step S6: adding In2S3 nanoparticles and a second fatty acid gallium solution into the container at a fourth temperature to obtain AgInGaS / AgInGaS / InGaS quantum dots after reaction; preferably, the fourth temperature is 150-210°C.

8. The method for preparing quantum dots according to claim 3, wherein: After step S4', the method further includes S5': adding a third indium precursor containing S element to the container at a fourth temperature, and obtaining AgInGaS / AgInGaS / InGaS quantum dots after the reaction; preferably, after step S5', the method further includes S6': adding a second gallium precursor to the container, and dropwise adding a third sulfur precursor, and obtaining AgInGaS / AgInGaS / InGaS / Ga2S3 quantum dots after the reaction at a fifth temperature; preferably, the fourth temperature is 150-210°C; preferably, the fifth temperature is 250-300°C.

9. The method for preparing quantum dots according to claim 3, wherein: The method for preparing the solution containing Ag2S nanoparticles includes reacting a second silver precursor and a fourth sulfur precursor in a second fatty amine at 40-70°C for a certain time; preferably, the method for preparing the solution containing In2S3 nanoparticles includes reacting a fourth indium precursor, the fatty acid, the non-coordinating solvent and the sulfur-fatty amine at 150-200°C for a certain time.

10. The method for preparing quantum dots according to claim 3, characterized in that: The first time is 1 to 10 minutes; the second time is 5 to 10 minutes; preferably, the third time is 5 to 30 minutes.

11. The method for preparing quantum dots according to claim 3, wherein: The first temperature is 100-150°C, the second temperature is 150-220°C; and the third temperature is 150-220°C.

12. The method for preparing quantum dots according to claim 3, wherein: The S1 includes: mixing the first indium precursor, the fatty acid, the first gallium precursor and the non-coordinating solvent in the container, heating until dissolved, to obtain the mixture; at least one of the first indium precursor and the first gallium precursor is a corresponding fatty acid metal salt; preferably, the fatty acid is oleic acid or a saturated fatty acid containing 8 to 18 carbon atoms.

13. The method for preparing quantum dots according to claim 3, characterized in that: The first and second sulfur precursors are selected from one or more of 1-octadecene, trialkylphosphinesulfide, sulfur-fatty amine, thiourea and mercaptan.

14. The method for preparing quantum dots according to claim 3, characterized in that: The first indium precursor and the second indium precursor are independently selected from one or more of fatty acid indium with 2 to 18 carbon atoms, indium halide-fatty amine mixed solution, halogenated bis(diethyldithiocarbamate) indium, or diethyldithiocarbamate indium; preferably, the first gallium precursor is selected from one or more of fatty acid gallium with 2 to 18 carbon atoms, acetylacetonate gallium-fatty amine, gallium halide-fatty amine solution, halogenated bis(diethyldithiocarbamate) indium, or diethyldithiocarbamate gallium; preferably, the first fatty amine is selected from oleylamine or a saturated fatty amine containing 8 to 18 carbon atoms; preferably, the first silver precursor is selected from one or more of fatty acid silver with 2 to 18 carbon atoms, the fatty acid silver-fatty amine mixed solution, the silver halide-fatty amine mixed solution, and the AgS nanoparticle solution; preferably, the molar ratio between the silver element of the first silver precursor and the indium element of the first indium precursor is (3:1) to (1:3).

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