A method for preparing quantum dots, quantum dots prepared thereby and applications thereof

Abstract

A method for preparing quantum dots, wherein the quantum dots are core-shell structures, and the first cationic precursor for forming the quantum dot core is RZnX, wherein R is an aliphatic chain segment or an aromatic chain segment, and X is a halogen atom. The first cationic precursor RZnX for forming the quantum dot core of the present application, wherein one end of the Zn atom in RZnX is connected to R through a covalent bond, and the other end is connected to the halogen atom through an ionic bond, and the activity is moderate, and the quantum dots formed have a narrow particle size distribution, a small half-peak width, and a high quantum yield. In addition, the present invention can also adjust the activity of the first cationic precursor by controlling the chain length of R and / or the type of halogen atom, thereby facilitating the preparation of quantum dots of different wavelengths; in addition, the preparation method of the present application is simple to operate, has a short reaction time, and is highly efficient, and meets the needs of large-scale production of quantum dots.

Description

Technical Field

[0001] The invention belongs to the field of nanotechnology, and in particular relates to a method for preparing quantum dots, quantum dots prepared thereby, and applications thereof. Background Art

[0002] In the prior art, the Zn sources for forming quantum dot cores mainly include halogenated zinc, fatty acid zinc or dialkyl zinc; these Zn sources are either poorly active or too active, resulting in poor particle size distribution of synthesized quantum dot cores or low quantum yield of quantum dots, and are not ideal Zn sources. Therefore, we urgently need to find a new Zn source for preparing quantum dot cores, so as to improve the particle size distribution of quantum dot cores, improve the quantum efficiency of quantum dots, and obtain quantum dots with better performance. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for preparing quantum dots, quantum dots prepared thereby and their applications. The preparation method is simple and convenient, wherein the Zn source forming the quantum dot core has moderate activity, the quantum dots formed have a narrow particle size distribution and a high quantum yield.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] The first object of the present invention is to provide a method for preparing quantum dots, wherein the quantum dots are of a core-shell structure, and the first cationic precursor forming the quantum dot core is RZnX, wherein R is an aliphatic segment or an aromatic segment, and X is a halogen atom.

[0006] Specifically, the number of carbon atoms in the R segment in the RZnX is not greater than 20, and the halogen atom is one of Cl and Br.

[0007] Specifically, forming the quantum dot core further includes a first anion precursor, wherein the first anion precursor is at least one selected from a sulfur precursor, a selenium precursor, and a tellurium precursor;

[0008] Preferably, the molar ratio of the first cationic precursor to the first anionic precursor is 1:(0.5-2).

[0009] Preferably, the step of forming quantum dots is as follows: dissolving the first anion precursor and the first cation precursor in a solvent to obtain a first solution, heating the solution to 180-320° C. in an inert atmosphere to react to obtain the quantum dot core, and then encapsulating the solution to obtain the quantum dot;

[0010] Preferably, the solvent is a coordinating solvent having a boiling point greater than 200°C.

[0011] Specifically, the formation of the quantum dot core also includes a second cation precursor, and the second cation precursor is an indium precursor or a cadmium precursor.

[0012] Preferably, forming the quantum dot core further includes a second anion precursor, and the second anion precursor is at least one selected from a phosphorus precursor, a sulfur precursor, a selenium precursor, and a tellurium precursor.

[0013] Further preferably, the molar ratio of the first cationic precursor to the second cationic precursor is 1:(0.2-5), and the molar ratio of the second cationic precursor to the second anionic precursor is 1:(0.5-2).

[0014] Preferably, the steps of forming quantum dots are as follows: dissolving the first cationic precursor, the second cationic precursor and the second anionic precursor in a solvent to obtain a second solution, heating the solution to 180-320° C. under an inert atmosphere to react to obtain the quantum dot core, and then encapsulating the solution to obtain the quantum dot;

[0015] Preferably, the solvent is a coordinating solvent having a boiling point greater than 200°C.

[0016] The second object of the present invention is to provide a quantum dot prepared by the preparation method described above.

[0017] The third object of the present invention is to provide an application of quantum dots, using the quantum dots as described above for display, lighting or biological marking.

[0018] Compared with the prior art, the present invention has at least the following advantages: the first cationic precursor RZnX used in the present invention to form the quantum dot core, one end of the Zn atom in RZnX is connected to R through a covalent bond, and the other end is connected to the halogen atom through an ionic bond, and the activity is moderate, and the quantum dots formed have a narrow particle size distribution, a small half-peak width, and a high quantum yield. In addition, the present invention can also adjust the activity of the first cationic precursor by controlling the chain length of R and / or the type of halogen atoms, thereby facilitating the preparation of quantum dots of different wavelengths;

[0019] In addition, the preparation method of the present application is easy to operate, has a short reaction time and high efficiency, and meets the needs of large-scale production of quantum dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Attached Figure 1 Absorption spectrum of quantum dots prepared in Example 1;

[0022] Attached Figure 2 The emission spectrum of quantum dots prepared in Example 1;

[0023] Attached Figure 3 Absorption spectrum of quantum dots prepared in Example 6;

[0024] Attached Figure 4 This is the emission spectrum of the quantum dots prepared in Example 6. DETAILED DESCRIPTION

[0025] The following will describe the technical solution in the embodiment in detail in combination with the implementation of the present application. It should be noted that the implementation is only a partial method, not all.

[0026] As stated herein, for example, "at least one (individual)" modifies the entire list of elements when preceding or following a list of elements without modifying the individual elements of the list. If not otherwise defined, all terms (including technical and scientific terms) in the specification may be defined as those skilled in the art generally understand. The terms defined in the commonly used dictionaries should be interpreted as being consistent with their meanings in the context of the relevant art and the present disclosure, and may not be interpreted in an ideal manner or too broadly unless clearly defined. In addition, unless explicitly described to the contrary, the wording "including" and the wording "comprising" when used in this specification indicate the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or their collections. Therefore, the above wording will be understood to mean including the stated elements, but not excluding any other elements.

[0027] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The term "or" means "and / or".

[0028] It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms.

[0029] As used herein, "about" or "approximately" includes the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" may mean that the deviation from the stated value is within one or more standard deviations, or within ±10%, ±5%.

[0030] In order to solve the problem that in the prior art, the Zn sources for forming quantum dot cores are mainly halogenated zinc, fatty acid zinc or dialkyl zinc; these Zn sources are either poorly active or too active, resulting in poor particle size distribution of synthesized quantum dot cores and low quantum yield of quantum dots, and are not ideal Zn sources. The present application provides a method for preparing quantum dots, using a Zn source with moderate activity to prepare quantum dot cores, thereby effectively improving the particle size distribution of quantum dot cores and improving the quantum efficiency of quantum dots.

[0031] Activity refers to the property of reacting quickly or promoting a rapid reaction. In the present invention, the activity of A is greater than that of B, which means that under the same reaction conditions, the energy barrier for A to participate in the reaction is less than the energy barrier for B to participate in the reaction, which can be manifested in one or more of the required reaction time, the required reaction temperature, the amount of raw materials required, etc. The first object of the present invention is to provide a method for preparing quantum dots, the quantum dots are core-shell structures, and the first cationic precursor forming the quantum dot core is RZnX, wherein R is an aliphatic segment or an aromatic segment, and X is a halogen atom. The zinc atom is connected to the R group by a covalent bond, and the R group carries a negatively charged segment, so that Zn exhibits a higher activity; and the halogen atom and the zinc atom are connected by an ionic bond, so that the Zn connected by the ionic bond exhibits a relatively low activity. The combination of the two makes the first cationic precursor RZnX, which forms the quantum dot core in the present application, have moderate activity.

[0032] In order to ensure the solubility and activity of the first cationic precursor, the number of carbon atoms in the R segment of RZnX should not be greater than 20. Since the fewer the number of carbon atoms in RZnX and the shorter the chain length, the higher its activity, in the present application, the activity of the first cationic precursor participating in the reaction can be controlled by simply adjusting the length of the carbon chain in RZnX.

[0033] The halogen atoms in RZnX include at least one of F, Cl, Br or I. Due to factors such as the large difference in the stability of different halogens, such as I is unstable and easily oxidized, and the purchase price of F varies greatly, therefore, in a preferred embodiment, the halogen atoms in RZnX include at least one of Cl and Br.

[0034] In summary, in the present application, the activity of the first cationic precursor RZnX can be simply adjusted by controlling the length of the R segment and / or the type of halogen atoms, thereby facilitating the adjustment of the particle size of the formed quantum dot core, thereby facilitating the adjustment of the luminescent wavelength of the quantum dots and controlling the particle size distribution of the quantum dots.

[0035] The formation of the quantum dot core also includes a first anion precursor, which is at least one selected from a sulfur precursor, a selenium precursor, and a tellurium precursor. In one embodiment of the present invention, the quantum dot core includes but is not limited to one of ZnS, ZnSe, ZnTe, ZnSeS, and ZnTeSe.

[0036] The sulfur precursor includes at least one of elemental sulfur, an organic phosphine complex of sulfur, a fatty amine compound of sulfur, an organic sulfur compound, and an organic thiol compound. Preferably, the sulfur precursor includes at least one of sulfur powder, a tetradecene solution of sulfur, a pentadecene solution of sulfur, a hexadecene solution of sulfur, a heptadecene solution of sulfur, an octadecene solution of sulfur, an n-octylamine solution of sulfur, a tri-n-octylamine solution of sulfur, trioctylphosphine sulfur, tributylphosphine sulfur, 1-octanethiol, 1-dodecanethiol, a mixture of 1-octanethiol and tri-n-octylamine, and a mixture of 1-octanethiol and tributylphosphine.

[0037] The selenium precursor includes at least one of simple selenium, selenium dioxide, organic phosphine complexes of selenium, fatty amine compounds of selenium, organic selenium compounds, and organic selenol compounds. Preferably, the selenium precursor includes at least one of selenium powder, selenium dioxide, trioctylphosphine selenium, tributylphosphine selenium, tetradecene solution of selenium, pentadecene solution of selenium, hexadecene solution of selenium, heptadecene solution of selenium, octadecene solution of selenium, selenol, diselenide, selenoether, selenoester, selenoamide, selenophene, and selenazole.

[0038] The tellurium precursor includes at least one of simple tellurium, an organic phosphine complex of tellurium, a tellurium aliphatic amine compound, an organic tellurium compound, and an organic tellurium alcohol compound. The tellurium precursor includes at least one of tellurium powder, tellurium chloride, a tetradecene solution of tellurium, a pentadecene solution of tellurium, a hexadecene solution of tellurium, a heptadecene solution of tellurium, an octadecene solution of tellurium, an n-octylamine solution of tellurium, trioctylphosphine tellurium, tributylphosphine tellurium, 1-octytellurol, and 1-dodecyltellurol.

[0039] The steps of forming quantum dots are as follows: a first anion precursor and a first cation precursor are dissolved in a solvent to obtain a first solution, and the solution is heated to 180-320° C. in an inert atmosphere to react to obtain a quantum dot core, which is then encapsulated to obtain a quantum dot. The encapsulation of the shell layer is carried out by conventional methods in the prior art.

[0040] In order to make the reaction uniform and sufficient, in a preferred embodiment of the present invention, one of the first anion precursor and the first cationic precursor is dissolved in a solvent to obtain a first solution, and under an inert atmosphere, the temperature is raised to 180-320°C, and the first cationic precursor and the other of the first cationic precursor are added to the first solution to react to obtain a quantum dot core.

[0041] In one embodiment of the present invention, a first anion precursor is dissolved in a solvent to obtain a first solution, and the temperature is raised to 180-320° C. under an inert atmosphere, and a first cationic precursor is added to the first solution for reaction to obtain a quantum dot core.

[0042] In another embodiment of the present invention, a first cationic precursor is dissolved in a solvent to obtain a first solution, and the temperature is raised to 180-320° C. under an inert atmosphere, and a first anionic precursor is added to the first solution for reaction to obtain a quantum dot core.

[0043] In order to make the reaction sufficient, the molar ratio of the first cationic precursor to the first anionic precursor is controlled to be 1:(0.5-2) in the present application.

[0044] The solvent is a coordinating solvent having a boiling point greater than 200°C.

[0045] In some preferred embodiments of the present invention, the solvent includes at least one of C10-C22 alkanes, olefins, halogenated hydrocarbons, aromatic hydrocarbons, ethers, amines, ketones, and esters.

[0046] Specifically, the solvent is a C14-C22 aliphatic hydrocarbon compound, including at least one of tetradecene, pentadecene, hexadecene, heptadecene, octadecene, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, and paraffin oil.

[0047] In another embodiment of the present invention, the formation of the quantum dot core also includes a second cation precursor and a second anion precursor, the second cation precursor is an indium precursor or a cadmium precursor, and the second anion precursor is at least one selected from a phosphorus precursor, a sulfur precursor, a selenium precursor, and a tellurium precursor.

[0048] The indium precursor includes indium acetate, indium chloride, indium carbonate, indium iodide, indium bromide, indium nitrate, indium perchlorate, indium myristate and indium stearate;

[0049] The cadmium precursor includes at least one of cadmium oxide, cadmium chloride, cadmium oxalate, cadmium acetate, cadmium carbonate, cadmium stearate, cadmium acetylacetonate, diethyl cadmium, cadmium myristate, and cadmium oleate;

[0050] The phosphorus precursor is preferably one or more of PH3, tri(trimethylsilyl)phosphine, tri(triethylsilyl)phosphine, tri(triphenylsilyl)phosphine, tri(dimethylamine)phosphine, tri(diethylamine)phosphine, and NaOCP; the selection of sulfur precursors, selenium precursors, and sulfur precursors is the same as above and will not be repeated here.

[0051] Specifically, the quantum dot core is one including but not limited to In(Zn)P, Cd(Zn)S, Cd(Zn)Se, Cd(Zn)Te, Cd(Zn)SeTe, and Cd(Zn)SeS.

[0052] The steps of forming quantum dots are as follows: a first cationic precursor, a second cationic precursor and a second anionic precursor are dissolved in a solvent and mixed to obtain a second solution, and the solution is heated to 180-320° C. in an inert atmosphere to react to obtain a quantum dot core, and then the core is encapsulated to obtain a quantum dot. The shell layer is encapsulated by a conventional method in the prior art.

[0053] In order to make the reaction uniform and sufficient, in a preferred embodiment of the present invention, the first cationic precursor and the second cationic precursor are added to a solvent to form a second solution, and the temperature is raised to 180-320° C. under an inert atmosphere, and the second anionic precursor is added to the second solution to react to obtain quantum dot cores.

[0054] In another preferred embodiment of the present invention, a second anion precursor is added to a solvent to form a second solution, and the temperature is raised to 180-320° C. under an inert atmosphere, and the first cation precursor and the second cation precursor are added to the second solution to react to obtain quantum dot cores.

[0055] In order to make the reaction sufficient, in the present application, the molar ratio of the first cationic precursor to the second cationic precursor is controlled to be 1:(0.2-5), and the molar ratio of the second cationic precursor to the second anionic precursor is controlled to be 1:(0.5-2).

[0056] The solvent is a coordination solvent having a boiling point greater than 200° C. The selection of the solvent is the same as above and will not be repeated here.

[0057] In the present invention, the shell of the quantum dot can be at least one of ZnSe, ZnS, ZnSeS, ZnTe, CdSe, CdSeS, CdTe and CdTeS. The shell of the quantum dot has at least one layer or multiple layers, and the required number of layers can be selected according to actual needs.

[0058] In some preferred embodiments of the present invention, the method for preparing quantum dots further comprises the steps of precipitating and purifying the prepared quantum dots using a purifying agent. These steps are well-known methods in the art and will not be described in detail here.

[0059] In the present application, the preparation process of quantum dots is carried out under an inert gas atmosphere. In some preferred embodiments of the present invention, the inert gas includes at least one of nitrogen and argon.

[0060] In a specific embodiment of the present invention, an application of quantum dots is provided, wherein the quantum dots prepared as above are used for display, lighting or biological labeling.

[0061] The present application will be described in detail below with reference to specific embodiments.

[0062] Embodiment 1: This embodiment provides a method for preparing quantum dots, and the specific steps are as follows:

[0063] 1 ml TOP-Se (2M) was dissolved in 20 ml ODE to obtain the first solution, which was then evacuated at 120°C and filled with argon to form an inert atmosphere. The temperature was raised to 240°C, and 1.2 mmol CH3CH2ZnBr dissolved in 10 ml TOP and 0.5 ml diphenylphosphine were added. The reaction was carried out for 30 min to obtain quantum dot cores, which were then encapsulated using methods known in the industry to obtain ZnSe / ZnS quantum dots.

[0064] Embodiment 2: This embodiment provides a method for preparing quantum dots, and the specific steps are as follows:

[0065] 1 ml TOP-Se (2M) was dissolved in 20 ml ODE to obtain the first solution, which was then evacuated at 120°C and filled with argon to form an inert atmosphere. The temperature was raised to 240°C, and 1.2 mmol CH3CH2ZnCl dissolved in 10 ml TOP and 0.5 ml diphenylphosphine were added. The reaction was carried out for 30 min to obtain quantum dot cores, which were then encapsulated using methods known in the industry to obtain ZnSe / ZnS quantum dots.

[0066] Embodiment 3: This embodiment provides a method for preparing quantum dots, and the specific steps are as follows:

[0067] 1 ml of TOP-Se (2M) was dissolved in 20 ml of ODE to obtain the first solution, which was then evacuated at 120°C and filled with argon to form an inert atmosphere. The temperature was raised to 240°C, and 1.2 mmol of PhZnCl dissolved in 10 ml of TOP and 0.5 ml of diphenylphosphine were added. The solution was reacted for 30 min to obtain quantum dot cores, which were then encapsulated using methods known in the industry to obtain ZnSe / ZnS quantum dots.

[0068] Embodiment 4: This embodiment provides a method for preparing quantum dots, and the specific steps are as follows:

[0069] Dissolve 1 ml of TOP-Se (2M) in 20 ml of ODE to obtain the first solution, evacuate at 120°C, fill with argon to form an inert atmosphere, raise the temperature to 240°C, add 1.2 mmol of CH3(CH2)3ZnBr dissolved in 10 ml of TOP and 0.5 ml of diphenylphosphine, react for 30 minutes to obtain quantum dot cores, and use common knowledge methods in the industry to encapsulate to obtain ZnSe / ZnS quantum dots.

[0070] Embodiment 5: This embodiment provides a method for preparing quantum dots, and the specific steps are as follows:

[0071] Dissolve 1 ml TOP-Se (2M) in 20 ml ODE to obtain the first solution, evacuate at 120°C, fill with argon to form an inert atmosphere, raise the temperature to 240°C, add 2 mmol CH3(CH2) dissolved in 10 ml TOP 11 ZnBr and 0.5 ml of diphenylphosphine were reacted for 30 minutes to obtain quantum dot cores, which were then encapsulated using methods known in the industry to obtain ZnSe / ZnS quantum dots.

[0072] Embodiment 6: This embodiment provides a method for preparing quantum dots, and the specific steps are as follows:

[0073] 1 mmol of In(OA)3 and 2 mmol of EtZnBr were dissolved in 20 ml of ODE, and the mixture was evacuated at 60°C for 1 hour. Argon was introduced to form an inert gas atmosphere, and the temperature was raised to 180°C. 1 mmol of (TMS)3P dissolved in 5 ml of TOP was added and the reaction was continued for 30 minutes to obtain quantum dot cores. The cores were then encapsulated using methods known in the industry to obtain In(Zn)P / ZnSe / ZnS quantum dots.

[0074] Embodiment 7: This embodiment provides a method for preparing quantum dots, and the specific steps are as follows:

[0075] 1 mmol of InCl3 and 2 mmol of EtZnBr were dissolved in 20 ml of ODE, and the mixture was evacuated at 60 °C for 1 hour. Argon was introduced to form an inert gas atmosphere, and the temperature was raised to 180 °C. 1 mmol of (DEA)3P dissolved in 5 ml of TOP was added and the reaction was continued for 30 minutes to obtain quantum dot cores. The cores were then encapsulated using methods known in the industry to obtain In(Zn)P / ZnSe / ZnS quantum dots.

[0076] Comparative Example 1: This comparative example provides a method for preparing quantum dots, and the specific steps are as follows: a preparation method using halogenated zinc as a Zn precursor.

[0077] Dissolve 1 ml of TOP-Se (2M) in 20 ml of ODE to obtain the first solution, evacuate at 120°C, fill with argon to form an inert atmosphere, raise the temperature to 240°C, add 1.2 mmol of ZnCl2 dissolved in 10 ml of TOP and 0.5 ml of diphenylphosphine, react for 30 minutes to obtain quantum dot cores, and use common knowledge methods in the industry to encapsulate to obtain ZnSe / ZnS quantum dots.

[0078] Comparative Example 2: This comparative example provides a method for preparing quantum dots, and the specific steps are as follows:

[0079] 1 ml of TOP-Se (2M) was dissolved in 20 ml of ODE to obtain the first solution, which was then evacuated at 120°C and filled with argon to form an inert atmosphere. The temperature was raised to 240°C, and 1.2 mmol of diethyl zinc dissolved in 10 ml of ODE and 0.5 ml of diphenylphosphine were added. The solution was reacted for 30 min to obtain quantum dot cores, which were then encapsulated using methods known in the industry to obtain ZnSe / ZnS quantum dots.

[0080] Comparative Example 3: This comparative example provides a method for preparing quantum dots, and the specific steps are as follows:

[0081] Dissolve 1mmol InCl3 and 2mmol ZnCl2 in 20ml OLAM, evacuate at 60℃ for 1 hour, fill with argon to form an inert gas atmosphere, heat to 180℃, add 1mmol (DEA)3P dissolved in 5ml TOP, react for 30 minutes to obtain quantum dot cores, and use the commonly known method in the industry to encapsulate to obtain In(Zn)P / ZnSe / ZnS quantum dots.

[0082] The quantum dots obtained in Examples 1-7 and Comparative Examples 1-3 were tested for their fluorescence spectra, fluorescence half-peak widths, and fluorescence quantum yields.

[0083]

[0084]

[0085] It can be seen from the embodiments and comparative examples that the first cationic precursor RZnX of the present application for forming the quantum dot core, one end of the Zn atom is connected to R by a covalent bond, and the other end is connected to the halogen atom by an ionic bond, and the activity is moderate. The quantum dots formed have a narrow particle size distribution, a small half-peak width, and a high quantum yield. In addition, the present invention can also adjust the activity of the first cationic precursor by controlling the chain length of R and / or the type of halogen atom, thereby facilitating the preparation of quantum dots of different wavelengths; according to the method of the present invention, the quantum yield of the obtained ZnSe / ZnS quantum dots is as high as 68%, and the half-peak width is as small as 12nm; the quantum yield of the obtained In(Zn)P / ZnSe / ZnS quantum dots is as high as 82%, and the half-peak width is as small as 12nm.

[0086] In addition, the preparation method of the present application is easy to operate, has a short reaction time and high efficiency, and meets the needs of large-scale production of quantum dots.

[0087] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing quantum dots, wherein the quantum dots are of a core-shell structure, characterized in that: The first cationic precursor for forming the quantum dot core is RZnX, wherein R is an aliphatic segment or an aromatic segment, and X is a halogen atom; the number of carbon atoms in the R segment is not greater than 20; the formation of the quantum dot core also includes a first anionic precursor, and the first anionic precursor is at least one selected from a sulfur precursor, a selenium precursor, and a tellurium precursor; the steps for forming the quantum dot are as follows: the first anionic precursor and the first cationic precursor are dissolved in a solvent to obtain a first solution, and the solution is heated to 180-320°C in an inert atmosphere for reaction to obtain the quantum dot core, and then the solution is encapsulated to obtain the quantum dot.

2. The preparation method according to claim 1, characterized in that: The halogen atom is one of Cl and Br.

3. The preparation method according to claim 1, characterized in that: The feeding molar ratio of the first cationic precursor to the first anionic precursor is 1:(0.5-2).

4. The preparation method according to claim 1, characterized in that: The solvent is a coordinating solvent with a boiling point greater than 200°C.

5. The preparation method according to claim 1, characterized in that: The process for forming the quantum dot core further includes a second cation precursor, wherein the second cation precursor is an indium precursor or a cadmium precursor.

6. The preparation method according to claim 5, characterized in that: The formation of the quantum dot core also includes a second anion precursor, and the second anion precursor is at least one selected from a phosphorus precursor, a sulfur precursor, a selenium precursor, and a tellurium precursor.

7. The preparation method according to claim 6, characterized in that: The molar ratio of the first cationic precursor to the second cationic precursor is 1:(0.2-5), and the molar ratio of the second cationic precursor to the second anionic precursor is 1:(0.5-2).

8. The preparation method according to claim 5, characterized in that: The specific steps of forming quantum dots are as follows: the first cationic precursor, the second cationic precursor and the second anionic precursor are dissolved in a solvent and mixed to obtain a second solution; under an inert atmosphere, the temperature is raised to 180-320°C for reaction to obtain the quantum dot core; and then the quantum dot is obtained by encapsulation; the solvent is a coordinating solvent with a boiling point greater than 200°C.

9. A quantum dot, characterized in that: The method is described in any one of claims 1 to 8.

10. An application of quantum dots, characterized in that: The quantum dots as claimed in claim 9 are used for display, lighting or bio-marking.

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